Additive manufacturing — Non-destructive testing — Intentionally seeding flaws in metallic parts

This document is intended to serve as a best practice for the identification and “seeding” of nondestructively detectable flaw replicas of metal alloy PBF and DED processes. Three seeding categories are described: a) process flaws through CAD design; b) build parameter manipulation; c) subtractive manufacturing. These include flaws present within as-deposited materials, post heat-treated or HIP processed material, and those flaws made detectable because of post-processing operations. Geometrical aspects or measurement are not the subjects of this document. WARNING — This document does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this document to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

Fabrication additive — Essais non destructifs — Implantation intentionnelle de défauts dans les pièces métalliques

Le présent document est destiné à servir de bonne pratique pour l'identification et «l'implantation» de répliques de défauts détectables de manière non destructive par les procédés PBF et DED en alliage métallique. Trois catégories d'implantation sont décrites: a) les défauts du procédé par la conception CAO; b) la manipulation des paramètres de fabrication; c) la fabrication soustractive. Cela comprend les défauts présents dans les matériaux tels que déposés, dans les matériaux traités par post-traitement thermique ou par HIP, et des défauts rendus détectables par les opérations de post-traitement. Les aspects géométriques ou les mesures ne font pas l'objet du présent document. ATTENTION — Le présent document n'a pas pour but de traiter tous les problèmes de sécurité, le cas échéant, liés à son application. Il est de la responsabilité de l'utilisateur du présent document d'établir des pratiques de sécurité et d'hygiène appropriées, et de déterminer l'applicabilité des restrictions réglementaires avant utilisation.

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TECHNICAL ISO/ASTM TR
REPORT 52906
First edition
2022-05
Additive manufacturing — Non-
destructive testing — Intentionally
seeding flaws in metallic parts
Fabrication additive — Essais non destructifs — Implantation
intentionnelle de défauts dans les pièces métalliques
Reference number
ISO/ASTM TR 52906:2022(E)
© ISO/ASTM International 2022
---------------------- Page: 1 ----------------------
ISO/ASTM TR 52906:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/ASTM International 2022

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester. In the United States, such requests should be sent to ASTM International.

ISO copyright office ASTM International
CP 401 • Ch. de Blandonnet 8 100 Barr Harbor Drive, PO Box C700
CH-1214 Vernier, Geneva West Conshohocken, PA 19428-2959, USA
Phone: +41 22 749 01 11 Phone: +610 832 9634
Fax: +610 832 9635
Email: copyright@iso.org Email: khooper@astm.org
Website: www.iso.org Website: www.astm.org
Published in Switzerland
© ISO/ASTM International 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/ASTM TR 52906:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 2

5 Typical AM flaws .................................................................................................................................................................................................. 3

6 Procedure to produce replicas ............................................................................................................................................................. 7

7 Seeding approaches ..........................................................................................................................................................................................7

7.1 General ........................................................................................................................................................................................................... 7

7.2 CAD seeding .............................................................................................................................................................................................. 8

7.3 AM process manipulation replicas .................................................................................................................................... 10

7.3.1 General ..................................................................................................................................................................................... 10

7.3.2 Entrapped unsintered powder............................................................................................................................ 11

7.3.3 Manual insertion of high-density inclusions .......................................................................................... 11

7.4 Post-production mechanical introduction of replicas ...................................................................................... 11

7.5 Significance and use for homogeneity ............................................................................................................................12

8 AM process manipulation for L-PBF and L-DED ...............................................................................................................14

8.1 General ........................................................................................................................................................................................................ 14

8.2 AM machine parameter manipulation ........................................................................................................................... 14

8.3 Applicable flaw-seeding approaches as a function of desired flaw type .........................................15

8.3.1 General .....................................................................................................................................................................................15

8.3.2 Porosity or voids (increased power density) ......................................................................................... 15

8.3.3 Surface-connected flaws .......................................................................................................................................... 15

8.4 Applicable flaw-seeding approach as a function of AM process ............................................................. 16

8.5 Applicable flaw-seeding approach as a function of AM material ........................................................... 17

8.5.1 General ..................................................................................................................................................................................... 17

8.5.2 High-density inclusions ............................................................................................................................................. 18

9 Applicable flaw-seeding approach as a function of post processing machining ..........................18

9.1 General ........................................................................................................................................................................................................ 18

9.2 Mechanical machining .................................................................................................................................................................. 18

9.3 Electrode discharge machining replicas ...................................................................................................................... 18

9.4 Laser drilling replicas ................................................................................................................................................................... 18

Bibliography .............................................................................................................................................................................................................................20

iii
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ISO/ASTM TR 52906:2022(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for

the different types of ISO documents can be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www.iso.org/iso/foreword.html.

This document was prepared by ISO/TC 261, Additive manufacturing, in cooperation with ASTM

Committee F42, Additive Manufacturing Technologies, on the basis of a partnership agreement between

ISO and ASTM International with the aim to create a common set of ISO/ASTM standards on additive

manufacturing, and in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 438, Additive manufacturing, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
© ISO/ASTM International 2022 – All rights reserved
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ISO/ASTM TR 52906:2022(E)
Introduction

This document provides information for intentionally seeding flaws in additively manufactured parts

and complements ISO/ASTM TR 52905 .

The different AM building descriptions can be found readily in published standards (see ISO 17296-2)

and scientific papers.

Jargon commonly used in the literature describing AM metal process defects includes “balling”,

“fireworks”, “smoke” and often are not specific to the morphology of the defect and often result from

widely differing mechanisms of formation.

When defining terms specific to AM metal flaws it may be useful to review some examples related to

welding technology.

This document is for the creation of seeded replicas supports the user’s understanding not only for the

characterization of actual flaws with respect to physical morphology but also for the materials and

mechanisms of formation, location, and orientation. In addition, the fundamentals of the processes

creating the replica (e.g. PBF or DED with regard to the heat sources electron beam (EB), laser beam

(LB) or AP (arc processes) also need to be considered). The intentional seeding to produce flaw replicas

can match the character of the actual flaw as closely as possible.

The reference photomicrographs or non-destructive testing images included in this document are in no

way to be construed as specifications. These reference photomicrographs and non-destructive testing

images are offered primarily to permit examples of “flaws” or replicate images thereof. They can be

used for comparison of reports. Flaw seeding will be discussed without context to a specific part,

location, or dimension. The material alloy will be provided as known. With some flaws the material

alloy may not be as important, for example, a pore may reside in any number of alloys. It can be noted

that there is currently no proven method for controlled and replicable seeding of intimate disbonds

(sometimes known as “kissing bonds”) – where two surfaces are in intimate or close contact, but with

compromised adhesion – in AM parts so this feature is, therefore, currently out of scope.

This document will not go into the fundamentals of each process but rather identify the parameters

within each process that can lead to the intentional seeding of AM structures.
1) In preparation. Stage at the time of publication ISO/ASTM DTR 52905:2022.
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TECHNICAL REPORT ISO/ASTM TR 52906:2022(E)
Additive manufacturing — Non-destructive testing —
Intentionally seeding flaws in metallic parts
1 Scope

This document is intended to serve as a best practice for the identification and “seeding” of

nondestructively detectable flaw replicas of metal alloy PBF and DED processes. Three seeding

categories are described:
a) process flaws through CAD design;
b) build parameter manipulation;
c) subtractive manufacturing.

These include flaws present within as-deposited materials, post heat-treated or HIP processed

material, and those flaws made detectable because of post-processing operations. Geometrical aspects

or measurement are not the subjects of this document.

WARNING — This document does not purport to address all of the safety concerns, if any,

associated with its use. It is the responsibility of the user of this document to establish

appropriate safety and health practices and determine the applicability of regulatory limitations

prior to use.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/ASTM 52900, Standard Terminology for Additive Manufacturing — General Principles —Terminology

ASTM B243, Standard Terminology of Powder Metallurgy
ASTM E7, Standard Terminology Relating to Metallography
ASTM E1316, Standard Terminology for Nondestructive Examinations
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/ASTM 52900, ASTM E7,

ASTM B243, ASTM E1316 and the following apply.

NOTE Terms for AM metal technology flaws are logically divided between PBF and DED categories of

processes.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
coupon
piece of material from which a specimen is prepared
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ISO/ASTM TR 52906:2022(E)
3.2
flaw classification

classification approach that provides a high-level system based on a primary characteristic or a

combination of characteristics

Note 1 to entry: Flaw classification may include similar flaw types that were created differently.

3.3
inclusion
foreign material held mechanically

Note 1 to entry: Inclusions are typically oxides, nitrides, hydrides, carbides, or combinations thereof being

formed due to contamination of the chamber gas, or already be present in the metal powder.

3.4
keyhole

type of porosity characterised by a circular depression formed due to instability of the vapour cavity

during processing
3.5
pore

inherent or induced cavity within a powder particle or within an object not connected to an exterior

surface
3.6
porosity
presence of small voids in a part making it less than fully dense
3.7
replica

intentional manipulated condition (flaw) to serve as the “seed” in a coupon (3.1) representing a known

flaw type
3.8
seeding

act of intentionally creating flaws, through CAD or manipulation of designated processing parameters,

that results in the placement of the anticipated replica (3.7) or the act of intentionally creating a replica

(3.7) through the insertion of a foreign object
3.9
sintering

process of heating a powder metal compact to increase density and/or improve mechanical properties

via solid state diffusion
3.10
surface-connected flaw

flaw that is in the body of the material but its boundaries reach to the material’s surface

3.11
unsintered

powder unaffected or affected but not fully consolidated during the additive manufacturing printing

process
4 Abbreviated terms
AM Additive Manufacturing
BM Base Metal
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ISO/ASTM TR 52906:2022(E)
CAD Computer-Aided Design/Computer-Aided Drafting/Computer-Aided Drawing
CNC Computer Numerical Control
DDC Ductility-Dip Cracking
DED Directed Energy Deposition
EB-DED Electron Beam Directed Energy Deposition
DR Digital Radiography (non-film)
EB-PBF Electron Beam Powder Bed Fusion
EDM Electrode Discharge Machining
GMA-DED Gas Metal Arc Directed Energy Deposition
HAZ Heat Affected Zone
HIP Hot Isostatic Pressing
LC Liquation Crack
L-DED Laser Directed Energy Deposition
L-PBF Laser Beam Powder Bed Fusion
MB Metal Base
NDE Non-destructive evaluation
NDT Non-destructive Testing
OEM Original Equipment Manufacturer
PBF Powder Bed Fusion
PSD Particle Size Distribution
RT Radiography Testing(film)
RQI Representative Quality Indicator
SC Solidification Crack
T Temperature melting point
WM Weld Metal
XCT X-ray Computed Tomography
5 Typical AM flaws

Typically, additive manufacturing flaws in materials fabricated using optimised parameters have small

spherical flaws. Builds with less developed parameters may have a keyhole or larger angular pores.

However, high value components are often screened for flaws at a level determined by fracture analysis

such as those described below. The ability to create replicas to support the NDT detection capability

of complex structures is unique to additive manufacturing and can be considered when standard

inspection techniques are not adequate to ensure inspection reliability.
© ISO/ASTM International 2022 – All rights reserved
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ISO/ASTM TR 52906:2022(E)

The occurrence of unintentional flaws during the additive manufacturing build is a possibility. The flaw

classification has been laid out in ISO/ASTM TR 52905 both L-PBF and DED. These flaws are: layer-

defects (horizontal lack of fusion), cross-layer (vertical lack of fusion), unconsolidated powder, trapped

powder, inclusion, layer shift, porosity and void; moreover, incomplete fusion, hole and cracking. It is

important to highlight that some DED defects are similar to those produced during the welding process,

while for L-PBF some defects are unique.

In addition to flaws created to replicate naturally occurring anomalies, replicas may be generated

to serve as targets that can be used to understand x-ray, ultrasonic or other NDT capabilities (see

Figure 1). It is important that the fabricator of such replicas understands the physics of the NDT’s

method for which the flaws will be used. Capabilities demonstrations include detection in a specific

[5]

complex geometry such as a Representative Quality Indicator (RQI) according to ASTM E1817 , or

detection at a specific orientation relating to the radiation beam. This replica is “seeded” intentionally

around the needs of the demonstrations. Ultrasonic sensing may find applicability through the technical

[3]

approach of ASTM E127 . Additionally, some of these seeding methods are implemented and detection

capabilities of seven NDT methods are assessed in ISO/ASTM TR 52905.

It has been found that replica size, orientation, and location can be designed into the build model to

create shapes (spheres, cubes, and rectangular prisms), sizes (lengths and diameters), and depths. An

example is shown in Figure 1 where embedded defects were designed into the step wedge with CAD

software, and since they are embedded with no powder removal vent, they are filled with unmelted

powder (unconsolidated powder/trapped powder).

a) CAD model showing the set of clusters and dimensions of the holes in the airfoil

© ISO/ASTM International 2022 – All rights reserved
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ISO/ASTM TR 52906:2022(E)

b) XCT scan displaying the visibility of the replicas seeded at different locations

and those that are not visible
Key
1 sets of holes containing 3 cluster
2 number of holes per cluster
3 holes dimensions per cluster
All 4 are visible.
⌀ 0,1 mm not visible.
Figure 1 — Example of RQI generic airfoil built on Ti-6Al-4V

With adjustments to the optimum build parameters, replicas can provide a desired off-nominal build

parameter. The shape of the replica can be planar, elliptical, rounded or another modelled configuration.

Two such off-nominal build parameters for seeding replicas are lowering laser power and increasing

the trace width to that which is greater than optimal.

Both of these types of replicas can be used to show the various NDT methods detection potentials. For

example, the computed tomography scans of the seeding replicas resulted in different yet detectable

material density changes created by each build parameter adjustment. The level of detail and different

views possible through computed tomography is shown in Figure 2 and Figure 3. The images in

both figures are not comparatives as those only illustrate differences in the detail when different

magnifications and methods are used.
© ISO/ASTM International 2022 – All rights reserved
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ISO/ASTM TR 52906:2022(E)

a) Computed tomography (XCT) slice image b) Microscopy image at 50×: large hatch spac-

ing
Figure 2 — Example of the difference in image when different magnification
a) Computed tomography (XCT) slice image b) Microscopy image at 50×
Figure 3 — Example of the difference in image when different method

Replicas that are open to the surface are producible through the predetermined width dimension in the

model. Figure 4 shows a model used to determine the width capability of the L-PBF machine. These are

linear-type replicas which can have the powder removed. Figure 5 shows the surface in the as-built and

polished conditions.
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ISO/ASTM TR 52906:2022(E)
Figure 4 — Open to the surface replica at different width dimensions
Figure 5 — As-built (left) and polished (right) coupon of the model in Figure 4
6 Procedure to produce replicas

The introduction of the AM process replicas can be accomplished through the changing of machine

parameters, feedstock conditions or mechanical procedures. The most representative methods are:

— seeding methods;
— AM process manipulation;
— mechanical procedures.
7 Seeding approaches
7.1 General

The following subsections provide seeding approaches for flaw replication using CAD insertion,

manipulation of off-nominal processing and mechanical machining.
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ISO/ASTM TR 52906:2022(E)
7.2 CAD seeding

This is the simplest, most direct, and most accurate method to seed defects on AM parts. Defects of

specific geometries (cylinders, spheres, etc.) are added in the CAD design at specific locations. Some

defects are open to the surface allowing the powder to be released and some are closed geometries

which will have trapped powder. This method is used in ISO/ASTM TR 52905 where artefacts were

built with such seeded defects and then tested with several NDT methods.

The typical AM only flaws were intentionally seeded in the following manner: horizontal cylinders

open to the surface for layer-defects (horizontal lack of fusion), vertical cylinders open to the surface

for cross-layer defects (vertical lack of fusion), spheres and cylinders not connected to the surface for

unconsolidated powder or trapped powder. Inclusions are represented by inserting foreign material

into the surface open seeded defects. Table 1 shows more detail of how this is achieved, while Figure 6

and Figure 7 show examples of a design S1 and the corresponding build in Inconel.

Table 1 — General AM Seeding by CAD design
Defect Classification CAD seed into geometry

Layer defects (horizontal Add horizontally oriented geometrical features to the part geometry at desired locations

lack of fusion) in the part. Geometries can include but not limited to: cylinders, cuboids, etc. Ideally open

to the surface to allow the powder to be released.

Cross Layer (vertical lack Add vertically oriented geometrical features to the part geometry at desired locations in

of fusion) the part. Geometries can include but not limited to: cylinders, cuboids, etc. Ideally open

to the surface to allow the powder to be released.

Trapped powder or un- Add geometrical features to the part geometry at desired locations in the part. Geome-

consolidated powder tries can include but not limited to: spheres, short cylinders, etc.

Layer shift Add such deviations to the CAD design of the part.

Inclusions Using any of the layer and/or cross layer defects insert a determined material in such cavity.

© ISO/ASTM International 2022 – All rights reserved
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ISO/ASTM TR 52906:2022(E)
Key
Diameter Length
Region Description
mm mm
Cylinders in various orientations
1 Region 1 (Unconsolidated/trapped powder). Orientation 0,3 2,0
offsets of 45° and 90° relative to the first instance
Vertical cylinders interconnected 0,1, 0,2, 0,3, 0,4, 0,5,
2 Region 2 5,0
and open at both top and bottom 0,6 and 0,7
Spheres (Voids/porosity, unconsolidated/ 0,1, 0,2, 0,3, 0,4, 0,5,
3 Region 3 -
trapped powder) 0,6 and 0,70
Horizontal cylinders open at 0,1, 0,2, 0,3, 0,4, 0,5,
4 Region 4 2,5
the outside edge (Layer defects) 0,6 and 0,7
Horizontal cylinders open at 0,1, 0,2, 0,3, 0,4, 0,5,
5 Region 5 2,0
the inside face of the pentagon (Layer defects) 0,6 and 0,7
Figure 6 — Example design for S1 version of seeded defects
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ISO/ASTM TR 52906:2022(E)
Figure 7 — An example of an S1 design build on Inconel
7.3 AM process manipulation replicas
7.3.1 General

This seeding is perhaps the more common approach when discussing the seeding of replicas (flaws)

and represents as closely as possible the potential naturally occurring flaws. Table 2 provides a list

of parameter adjustments that can be used for replica creation. It can be understood that the severity

of the replica may or may not match the target flaw. For example, the lack of fusion-type flaw can

vary considerably based on the cause and length of processing time. To compensate for severity,

multiple replicas using a range of the primary process manipulations provide a broader approach to

understanding demonstrable detection.

Many studies have been conducted through the manipulation of off-nominal processing parameters

such as defects – holes or slots, delays – laser on and/or off delays, trace width increase or decrease,

and laser power decrease or increase. Associated with these manipulations is the reference power

or optimal build parameters. Based on the outcome and end-use of the replica, the producer can seed

needed coupons. Table 2 presents the build parameter adjustments to create replica/flaw during the

additive manufacturing process.

Table 2 — Build parameter modifications and powder conditions for flaw formation in the AM

process
Defect Classification Off-nominal build condition
Hatch speed/hatch spacing
Vary/measure powder moisture content (or modify bake-out)
Pore Vary powder or chamber atmosphere purity
Remelt voids into larger or irregular pores
Choose parameter to ensure keyhole formation and collapse
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ISO/ASTM TR 52906:2022(E)
Table 2 (continued)
Defect Classification Off-nominal build condition
Spread powder layer with a damaged blade, rake, or roller

Choose parameters to create ejecta (“fireworks”), “balling” or “smoke” related defects

Void
Induce intentional process interruption/restart
Beam power spike

Vary constraint or support geometry to increase stress state upon solidification and cooling

Choose an alloy with a decreased level of weldability
Crack

Contaminate the built environment or alloy with a trace alloy to mock improper chamber

cleaning conditions
Beam power, W
Energy density, J/mm
Beam focal offset, spot size, µm
Hatching spacing (line offset), µm
Layer defects (horizon-
Scan speed, m/s
tal lack of fusion) (un-
Scan strategy
consolidated]
Temporary reduction of or turn off the heat source
Halt process, introduce thin layer tracer film, restart process
Induce disturbance typical to process, e.g. leak air into the process gas
Induce disturbance typical to process, e.g. switch process gas Ar to N
Trapped powder in Part
Due to part geometry design, the unmelted powder is trapped within part cavities
Geometry
Cross-Layer
...

RAPPORT ISO/ASTM TR
TECHNIQUE 52906
Première édition
2022-05
Fabrication additive — Essais
non destructifs — Implantation
intentionnelle de défauts dans les
pièces métalliques
Additive manufacturing — Non-destructive testing — Intentionally
seeding flaws in metallic parts
Numéro de référence
ISO/ASTM TR 52906:2022(F)
© ISO/ASTM International 2022
---------------------- Page: 1 ----------------------
ISO/ASTM TR 52906:2022(F)
DOCUMENT PROTÉGÉ PAR COPYRIGHT
© ISO/ASTM International 2022

Tous droits réservés. Sauf prescription différente ou nécessité dans le contexte de sa mise en œuvre, aucune partie de cette

publication ne peut être reproduite ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique,

y compris la photocopie, ou la diffusion sur l’internet ou un intranet, sans autorisation écrite soit de l’ISO à l’adresse ci-après,

soit d’un organisme membre de l’ISO dans le pays du demandeur. Aux États-Unis, les demandes doivent être adressées à ASTM

International.
ISO copyright office ASTM International
Case postale 401 • Ch. de Blandonnet 8 100 Barr Harbor Drive, PO Box C700
CH-1214 Vernier, Genève West Conshohocken, PA 19428-2959, USA
Tél.: +41 22 749 01 11 Tél.: +610 832 9634
Fax: +41 22 749 09 47 Fax: +610 832 9635
E-mail: copyright@iso.org E-mail: khooper@astm.org
Web: www.iso.org Web: www.astm.org
Publié en Suisse
© ISO/ASTM International 2022 – Tous droits réservés
---------------------- Page: 2 ----------------------
ISO/ASTM TR 52906:2022(F)
Sommaire Page

Avant-propos .............................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Domaine d'application ...................................................................................................................................................................................1

2 Références normatives ..................................................................................................................................................................................1

3 Termes et définitions ...................................................................................................................................................................................... 1

4 Termes abrégés ..................................................................................................................................................................................................... 3

5 Défauts de FA types ...........................................................................................................................................................................................4

6 Procédure de production de répliques ........................................................................................................................................ 7

7 Approches d'implantation .........................................................................................................................................................................7

7.1 Généralités ................................................................................................................................................................................................. 7

7.2 Implantation par CAO ....................................................................................................................................................................... 8

7.3 Répliques de manipulation par procédé de FA........................................................................................................ 10

7.3.1 Généralités ............................................................................................................................................................................ 10

7.3.2 Poudre non frittée piégée ........................................................................................................................................ 11

7.3.3 Insertion manuelle d'inclusions à haute masse volumique .......................................................12

7.4 Introduction mécanique des répliques en postproduction .........................................................................12

7.5 Signification et utilisation pour l'homogénéité ......................................................................................................12

8 Manipulation du procédé de FA pour L-PBF et L-DED ...............................................................................................14

8.1 Généralités .............................................................................................................................................................................................. 14

8.2 Manipulation des paramètres de la machine de FA ............................................................................................ 14

8.3 Approches applicables d'implantation de défauts en fonction du type de défaut

souhaité ........................................................................................................................................... ........................................................... 15

8.3.1 Généralités ............................................................................................................................................................................15

8.3.2 Porosité ou vides (densité de puissance accrue) ................................... ..............................................15

8.3.3 Défauts liés à la surface .............................................................................................................................................15

8.4 Approches applicables d'implantation de défauts en fonction du procédé de FA .................... 16

8.5 Approches applicables d'implantation de défauts en fonction du matériau de FA ................. 18

8.5.1 Généralités ............................................................................................................................................................................ 18

8.5.2 Inclusions à haute densité ....................................................................................................................................... 18

9 Approches applicables d'implantation de défauts en fonction de l'usinage post-

traitement ................................................................................................................................................................................................................18

9.1 Généralités .............................................................................................................................................................................................. 18

9.2 Usinage mécanique .......................................................................................................................................................................... 18

9.3 Répliques d'usinage par électroérosion ........................................................................................................................ 19

9.4 Répliques par perçage laser ..................................................................................................................................................... 19

Bibliographie ...........................................................................................................................................................................................................................21

iii
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ISO/ASTM TR 52906:2022(F)
Avant-propos

L'ISO (Organisation internationale de normalisation) est une fédération mondiale d'organismes

nationaux de normalisation (comités membres de l'ISO). L'élaboration des Normes internationales est

en général confiée aux comités techniques de l'ISO. Chaque comité membre intéressé par une étude

a le droit de faire partie du comité technique créé à cet effet. Les organisations internationales,

gouvernementales et non gouvernementales, en liaison avec l'ISO participent également aux travaux.

L'ISO collabore étroitement avec la Commission électrotechnique internationale (IEC) en ce qui

concerne la normalisation électrotechnique.

Les procédures utilisées pour élaborer le présent document et celles destinées à sa mise à jour sont

décrites dans les Directives ISO/IEC, Partie 1. En particulier, les différents critères d'approbation

requis pour les différents types de documents ISO peuvent être notés. Le présent document a été

rédigé conformément aux règles de rédaction données dans les Directives ISO/IEC, Partie 2 (voir

www.iso.org/directives).

L'attention est attirée sur le fait que certains des éléments du présent document peuvent faire l'objet de

droits de propriété intellectuelle ou de droits analogues. L'ISO ne saurait être tenue pour responsable

de ne pas avoir identifié de tels droits de propriété et averti de leur existence. Les détails concernant

les références aux droits de propriété intellectuelle ou autres droits analogues identifiés lors de

l'élaboration du document sont indiqués dans l'Introduction et/ou dans la liste des déclarations de

brevets reçues par l'ISO (voir www.iso.org/patents).

Les appellations commerciales éventuellement mentionnées dans le présent document sont données

pour information, par souci de commodité, à l'intention des utilisateurs et ne sauraient constituer un

engagement.

Pour une explication de la nature volontaire des normes, la signification des termes et expressions

spécifiques de l'ISO liés à l'évaluation de la conformité, ou pour toute information au sujet de l'adhésion

de l'ISO aux principes de l'Organisation mondiale du commerce (OMC) concernant les obstacles

techniques au commerce (OTC), voir le lien suivant: www.iso.org/iso/fr/avant-propos.

Le présent document a été élaboré par l'ISO/TC 261, Fabrication additive, en coopération avec le

Comité F42 de l'ASTM, Technologies de fabrication additive, dans le cadre d'un accord de partenariat

entre l'ISO et ASTM International dans le but de créer un ensemble commun de normes ISO/ASTM sur

la fabrication additive et en collaboration avec le Comité Européen de Normalisation (CEN), Comité

technique CEN/TC 438, Fabrication additive, conformément à l'Accord de coopération technique entre

l'ISO et le CEN (Accord de Vienne).

Il convient que l'utilisateur adresse tout retour d'information ou toute question concernant le présent

document à l'organisme national de normalisation de son pays. Une liste exhaustive desdits organismes

se trouve à l'adresse www.iso.org/fr/members.html.
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ISO/ASTM TR 52906:2022(F)
Introduction

Le présent document fournit des informations pour l'implantation intentionnelle de défauts dans les

pièces fabriquées de manière additive, et complète l'ISO/ASTM TR 52905 .

Les différentes descriptions de fabrication de FA peuvent être trouvées facilement dans les normes

publiées (voir l'ISO 17296-2) et les articles scientifiques.

Le jargon couramment utilisé dans la littérature décrivant les défauts du procédé de FA métallique

comprend le «balling», les «feux d'artifice», la «fumée» et ils ne sont souvent pas spécifiques à la

morphologie du défaut et souvent résultent de mécanismes de formation très différents.

Lors de la définition de termes spécifiques aux défauts de FA métallique, il peut être utile d'examiner

certains exemples liés à la technologie du soudage.

Le présent document est destiné à la création de répliques faisant l'objet d'une implantation qui aident

l'utilisateur à comprendre non seulement la caractérisation des défauts réels en ce qui concerne la

morphologie physique, mais également les matériaux et les mécanismes de formation, l'emplacement et

l'orientation. En complément, les principes fondamentaux des procédés de création de la réplique [par

exemple, PBF ou DED en ce qui concerne les sources de chaleur, faisceau d'électrons (EB), faisceau laser

(LB) ou AP (procédés d'arc) nécessitent également d'être pris en compte]. L'implantation intentionnelle

pour produire des répliques présentant des défauts peut correspondre au caractère du défaut réel le

plus fidèlement possible.

Les photomicrographies de référence ou les images d'essais non destructifs incluses dans le présent

document ne sont en aucun cas à être interprétées comme des spécifications. Ces photomicrographies

de référence et ces images d'essais non destructifs sont proposées principalement pour permettre

des exemples de «défauts» ou des images reproduites de ceux-ci. Elles peuvent être utilisées pour

la comparaison de rapports. L'implantation des défauts sera discutée sans référence à une pièce, un

emplacement ou une dimension spécifique. L'alliage du matériau sera fourni tel qu'il est connu. Pour

certains défauts, l'alliage du matériau peut ne pas être aussi important, par exemple, un pore peut se

trouver dans un nombre quelconque d'alliages. Il peut être noté qu'à l'heure actuelle, aucune méthode

éprouvée n'existe pour l'implantation contrôlée et reproductible de décollements intimes (quelquefois

connus comme «kissing bond») - lorsque deux surfaces sont en contact intime ou proche, mais avec une

adhérence compromise - dans des pièces de FA de sorte que cette caractéristique est, par conséquent,

actuellement hors du domaine d'application.

Le présent document n'aborde pas les principes fondamentaux de chaque procédé, mais identifie plutôt

les paramètres de chaque procédé qui peuvent conduire à l'implantation intentionnelle de structures

de FA.

1) En cours de préparation. Stade au moment de la publication ISO/ASTM DTR 52905:2022.

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RAPPORT TECHNIQUE ISO/ASTM TR 52906:2022(F)
Fabrication additive — Essais non destructifs —
Implantation intentionnelle de défauts dans les pièces
métalliques
1 Domaine d'application

Le présent document est destiné à servir de bonne pratique pour l'identification et «l'implantation»

de répliques de défauts détectables de manière non destructive par les procédés PBF et DED en alliage

métallique. Trois catégories d'implantation sont décrites:
a) les défauts du procédé par la conception CAO;
b) la manipulation des paramètres de fabrication;
c) la fabrication soustractive.

Cela comprend les défauts présents dans les matériaux tels que déposés, dans les matériaux traités par

post-traitement thermique ou par HIP, et des défauts rendus détectables par les opérations de post-

traitement. Les aspects géométriques ou les mesures ne font pas l'objet du présent document.

ATTENTION — Le présent document n'a pas pour but de traiter tous les problèmes de sécurité, le

cas échéant, liés à son application. Il est de la responsabilité de l'utilisateur du présent document

d'établir des pratiques de sécurité et d'hygiène appropriées, et de déterminer l'applicabilité des

restrictions réglementaires avant utilisation.
2 Références normatives

Les documents suivants sont cités dans le texte de sorte qu'ils constituent, pour tout ou partie de leur

contenu, des exigences du présent document. Pour les références datées, seule l'édition citée s'applique.

Pour les références non datées, la dernière édition du document de référence s'applique (y compris les

éventuels amendements).

ISO/ASTM 52900, Fabrication additive — Principes généraux — Fondamentaux et vocabulaire

ASTM B243, Standard Terminology of Powder Metallurgy
ASTM E7, Standard Terminology Relating to Metallography
ASTM E1316, Standard Terminology for Nondestructive Examinations
3 Termes et définitions

Pour les besoins du présent document, les termes et définitions donnés dans l'ISO/ASTM 52900,

l'ASTM E7, l'ASTM B243, l'ASTM E1316 ainsi que les suivants s'appliquent.

NOTE Les termes relatifs aux défauts de la technologie de FA métallique sont logiquement répartis entre les

catégories de procédés PBF et DED.

L'ISO et l'IEC tiennent à jour des bases de données terminologiques destinées à être utilisées en

normalisation, consultables aux adresses suivantes:
— IEC Electropedia: disponible à l'adresse https:// www .electropedia .org/

— ISO Online browsing platform: disponible à l'adresse https:// www .iso .org/ obp

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ISO/ASTM TR 52906:2022(F)
3.1
coupon
pièce de matériau à partir de laquelle un échantillon est préparé
3.2
classification du défaut

approche de classification qui fournit un système de haut niveau basé sur une caractéristique primaire

ou une combinaison de caractéristiques

Note 1 à l'article: La classification du défaut peut comprendre des types de défauts similaires qui ont été créés

différemment.
3.3
inclusion
matériau étranger retenu de mécaniquement

Note 1 à l'article: Les inclusions sont généralement des oxydes, des nitrures, des hydrures, des carbures, ou des

combinaisons de ceux-ci, formés en raison de la contamination du gaz de la chambre, ou déjà présents dans la

poudre métallique.
3.4
trou de serrure

type de porosité caractérisé par une dépression circulaire formée en raison de l'instabilité de la cavité

de vapeur pendant le traitement
3.5
pore

cavité inhérente ou induite à l'intérieur d'une particule de poudre ou à l'intérieur d'un objet non

connecté à une surface extérieure
3.6
porosité
présence de petits vides dans une pièce, la rendant moins que totalement dense
3.7
réplique

condition manipulée intentionnellement (défaut) pour servir d'« implant » dans un coupon (3.1),

représentant un type de défaut connu
3.8
implantation

fait de créer intentionnellement des défauts, par CAO ou manipulation de paramètres de traitement

désignés, qui entraîne la mise en place de la réplique (3.7) prévue ou le fait de créer intentionnellement

une réplique (3.7) par l'insertion d'un objet étranger
3.9
frittage

procédé de chauffage d'une poudre métallique compactée pour augmenter la masse volumique et/ou

améliorer les propriétés mécaniques par diffusion à l'état solide
3.10
défaut lié à la surface

défaut qui se trouve dans le corps du matériau mais dont les extrémités atteignent la surface du

matériau
3.11
non frittée

poudre non affectée, ou affectée mais non entièrement consolidée, pendant le procédé d'impression de

fabrication additive
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ISO/ASTM TR 52906:2022(F)
4 Termes abrégés
CAO Conception assistée par ordinateur
CNC Commande numérique par calculateur
DDC (ductility-dip cracking) Fissuration par chute de ductilité
DED (directed energy deposition) Dépôt de matière sous énergie concentrée

EB-DED (electron beam directed energy deposition) Dépôt de matières sous énergie concentrée par

faisceau d'électrons
DR (digital radiography (non-film)) Radiographie numérique (non film)

EB-PBF (Electron Beam Powder Bed Fusion) Fusion sur lit de poudre par faisceau d'électrons

EDM (electrode discharge machining) Usinage par électroérosion
FA Fabrication additive

GMA-DED (gas metal arc directed energy deposition) Dépôt de matière sous énergie concentrée par

arc avec électrode fusible
HAZ (Heat Affected Zone) Zone thermiquement affectée
HIP (hot isostatic pressing) Compression isostatique à chaud
LC (Liquation Crack) Fissuration par liquation

L-DED (laser directed energy deposition) Dépôt de matière sous énergie concentrée par laser

L-PBF (laser beam powder bed fusion) Fusion sur lit de poudre par faisceau laser
MB (Base Metal) Métal de base
NDE (non-destructive evaluation) Évaluation non destructive
NDT (Non-destructive Testing) Contrôles non destructifs
OEM (original equipment manufacturer) Fabricant d'origine
PBF (powder bed fusion) Fusion sur lit de poudre
PSD (particle size distribution) Distribution granulométrique
RT (radiography testing (film)) Essais radiographiques (film)
RQI (Representative Quality Indicator) Indicateur représentatif de qualité
SC (Solidification Crack) Fissure de solidification
T (temperature melting point) Température de fusion
WM (weld metal) Métal fondu
XCT (X-ray Computed Tomography) Tomographie par rayons X
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ISO/ASTM TR 52906:2022(F)
5 Défauts de FA types

En général, les défauts de fabrication additive dans les matériaux fabriqués en utilisant des paramètres

optimisés présentent de petits défauts sphériques. Les fabrications avec des paramètres moins

développés peuvent présenter un trou de serrure ou des pores angulaires plus grands. Cependant, les

composants de grande valeur font souvent l'objet d'un contrôle des défauts à un niveau déterminé par

l'analyse des fractures telles que celles décrites ci-dessous. La capacité de créer des répliques pour

soutenir la capacité de détection des NDT de structures complexes est unique à la fabrication additive

et peut être envisagée lorsque les techniques d'inspection standard ne suffisent pas à assurer la fiabilité

de l'inspection.

L'apparition de défauts non intentionnels au cours de la fabrication par fabrication additive est une

possibilité. La classification des défauts a été établie dans l'ISO/ASTM TR 52905, tant pour la L-PBF

que le DED. Ces défauts sont: les défauts de couche (manque horizontal de fusion), les couches croisées

(manque vertical de fusion), la poudre non consolidée, la poudre piégée, l'inclusion, le déplacement de

couche, la porosité et le vide; par ailleurs la fusion incomplète, le trou et la fissure. Il est important de

souligner que certains défauts du DED sont similaires à ceux produits pendant le procédé de soudage,

alors que pour la L-PBF, certains défauts sont uniques.

En complément des défauts créés pour reproduire des anomalies d'origine naturelle, des répliques

peuvent être générées pour servir de cibles qui peuvent être utilisées pour comprendre les rayons X,

les ultrasons ou d'autres capacités de NDT (voir la Figure 1). Il est important que le fabricant de ces

répliques comprenne la physique de la méthode de NDT pour laquelle les défauts seront utilisés. Les

démonstrations de capacités comprennent la détection dans une géométrie complexe spécifique telle

qu'un indicateur représentatif de la qualité (RQI, Representative Quality Indicator) conformément

[5]

à l'ASTM E1817 , ou la détection dans une orientation spécifique par rapport au faisceau de

rayonnement. Cette réplique fait l'objet d'une «implantation» intentionnelle en fonction des besoins des

démonstrations. La détection par ultrasons peut trouver une application grâce à l'approche technique

[3]

de l'ASTM E127 . En complément, certaines de ces méthodes d'implantation sont mises en œuvre et les

capacités de détection de sept méthodes de NDT sont évaluées dans l'ISO/ASTM TR 52905.

Il a été constaté que la taille, l'orientation et l'emplacement des répliques peuvent être conçus dans

le modèle de fabrication pour créer des formes (sphères, cubes et prismes rectangulaires), des tailles

(longueurs et diamètres) et des profondeurs. Un exemple est illustré à la Figure 1 où des défauts

intégrés ont été conçus dans la cale gradins à l'aide d'un logiciel de CAO et comme ils sont intégrés sans

évent d'évacuation de la poudre, ils sont remplis avec de la poudre non fondue (poudre non consolidée/

poudre piégée).

a) Modèle CAO montrant l'ensemble des amas et les dimensions des trous dans le profil aérody-

namique
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ISO/ASTM TR 52906:2022(F)

b) Balayage XCT montrant la visibilité des répliques implantées à différents endroits et celles

qui ne sont pas visibles
Légende
1 ensembles de trous comportant 3 amas
2 nombre de trous par amas
3 dimensions des trous par amas
Les 4 sont visibles.
⌀ 0,1 mm non visible.

Figure 1 — Exemple d'un RQI de profil aérodynamique générique fabriqué sur Ti-6Al-4V

Grâce à des ajustements des paramètres de fabrication optimaux, les répliques peuvent fournir un

paramètre de fabrication hors-norme souhaité. La forme de la réplique peut être plane, elliptique,

arrondie ou présenter une autre configuration modélisée. Deux de ces paramètres de fabrication hors-

normes pour l'implantation de répliques sont la réduction de la puissance du laser et l'augmentation de

la largeur du tracé au-delà de la valeur optimale.

Ces deux types de répliques peuvent être utilisés pour montrer les potentiels de détection des

différentes méthodes de NDT. Par exemple, les balayages de tomographie informatisée des répliques

d'implantation ont donné lieu à des changements de masse volumique du matériau différents mais

détectables, créés par chaque ajustement du paramètre de fabrication. Le niveau de détail et les

différentes vues possibles par tomographie informatisée sont illustrés dans la Figure 2 et la Figure 3.

Les images de ces deux figures ne sont pas comparatives, car elles illustrent uniquement les différences

de détails quand différents grossissements et méthodes sont utilisés.
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ISO/ASTM TR 52906:2022(F)

a) Coupe de tomographie informatisée (XCT) b) Image de microscopie à 50×: grand espace-

ment des hachures
Figure 2 — Exemple de la différence dans une image avec divers grossissements
a) Coupe de tomographie informatisée (XCT) b) Image de microscopie à 50×
Figure 3 — Exemple de la différence dans une image avec diverses méthodes

Les répliques qui sont ouvertes à la surface sont productibles grâce à la dimension de largeur

prédéterminée dans le modèle. La Figure 4 illustre un modèle utilisé pour déterminer la capacité de

largeur de la machine L-PBF. Il s'agit de répliques de type linéaire qui peuvent permettre de retirer la

poudre. La Figure 5 illustre la surface telle que fabriquée et polie.
© ISO/ASTM International 2022 – Tous droits réservés
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ISO/ASTM TR 52906:2022(F)
Figure 4 — Réplique ouverte à la surface pour différentes dimensions de largeur

Figure 5 — Coupon tel que fabriqué (gauche) et poli (droite) du modèle de la Figure 4

6 Procédure de production de répliques

L'introduction de répliques dans le procédé de FA peut être réalisée en modifiant les paramètres de la

machine, les conditions de la matière première ou les procédures mécaniques. Les méthodes les plus

représentatives sont:
— les méthodes d'implantation;
— la manipulation du procédé de FA;
— les procédures mécaniques.
7 Approches d'implantation
7.1 Généralités

Les paragraphes suivants fournissent des approches d'implantation pour la reproduction des défauts

utilisant l'insertion par CAO, la manipulation du traitement hors-norme et l'usinage mécanique.

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ISO/ASTM TR 52906:2022(F)
7.2 Implantation par CAO

Il s'agit de la méthode la plus simple, la plus directe et la plus exacte pour implanter des défauts sur

des pièces de FA. Des défauts de géométries spécifiques (cylindres, sphères, etc.) sont ajoutés lors la

conception CAO à des endroits spécifiques. Certains défauts sont ouverts à la surface, permettant à la

poudre d'être libérée, et d'autres sont des géométries fermées qui auront de la poudre piégée. Cette

méthode est utilisée dans l'ISO/ASTM TR 52905, où des pièces types ont été fabriquées avec de tels

défauts implantés et ensuite soumis à essai avec plusieurs méthodes de NDT.

Les défauts de FA types uniquement ont été implantés intentionnellement de la manière suivante:

cylindres horizontaux ouverts à la surface pour les défauts de couche (manque horizontal de fusion),

cylindres verticaux ouverts à la surface pour les défauts de couche croisée (manque vertical de fusion),

sphères et cylindres non reliés à la surface pour la poudre non consolidée ou la poudre piégée. Les

inclusions sont représentées par l'insertion d'un matériau étranger dans les défauts implantés ouverts

en surface. Le Tableau 1 montre plus de détail sur comment cela a été réalisé, tandis que la Figure 6 et

la Figure 7 illustrent des exemples d'une conception S1 et de la fabrication correspondante en Inconel.

Tableau 1 — Implantation générale de FA par conception CAO
Classification de
Implantation par CAO dans la géométrie
défaut

Défauts de couche Ajouter des caractéristiques géométriques orientées horizontalement à la géométrie de

(manque horizontal de la pièce aux endroits souhaités de la pièce. Les géométries peuvent comprendre mais

fusion) sans s'y limiter: des cylindres, des cuboïdes, etc. Idéalement ouverts à la surface pour

permettre à la poudre d'être libérée.

Couche croisée Ajouter des caractéristiques géométriques orientées verticalement à la géométrie de

(manque vertical de la pièce aux endroits souhaités de la pièce. Les géométries peuvent comprendre mais

fusion) sans s'y limiter: des cylindres, des cuboïdes, etc. Idéalement ouverts à la surface pour

permettre à la poudre d'être libérée.

Poudre piégée ou Ajouter des caractéristiques géométriques à la géométrie de la pièce aux endroits sou-

poudre non consolidée haités de la pièce. Les gé
...

TECHNICAL ISO/ASTM TR
REPORT 52906
First edition
Additive manufacturing — Non-
destructive testing — Intentionally
seeding flaws in metallic parts
Fabrication additive — Essais non destructifs — Implantation
intentionnelle de défauts dans les pièces métalliques
PROOF/ÉPREUVE
Reference number
ISO/ASTM TR 52906:2021(E)
© ISO/ASTM TR 2021
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ISO/ASTM TR 52906:2021(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO/ASTM International 2021

All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may

be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on

the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below

or ISO’s member body in the country of the requester. In the United States, such requests should be sent to ASTM International.

ISO copyright office ASTM International
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Published in Switzerland
PROOF/ÉPREUVE © ISO/ASTM International 2021 – All rights reserved
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ISO/ASTM TR 52906:2021(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Abbreviated terms ............................................................................................................................................................................................. 2

5 Typical AM flaws .................................................................................................................................................................................................. 3

6 Procedure to produce replicas ............................................................................................................................................................. 7

7 Seeding approaches ..........................................................................................................................................................................................7

7.1 General ........................................................................................................................................................................................................... 7

7.2 CAD seeding .............................................................................................................................................................................................. 7

7.3 AM process manipulation replicas ....................................................................................................................................... 9

7.3.1 General ........................................................................................................................................................................................ 9

7.3.2 Entrapped unsintered powder............................................................................................................................ 10

7.3.3 Manual insertion of high-density inclusions .......................................................................................... 10

7.4 Post-production mechanical introduction of replicas ...................................................................................... 10

7.5 Significance and use for homogeneity ............................................................................................................................ 11

8 AM process manipulation for L-PBF and L-DED ...............................................................................................................13

8.1 General ........................................................................................................................................................................................................13

8.2 AM machine parameter manipulation ........................................................................................................................... 13

8.3 Applicable flaw-seeding approaches as a function of desired flaw type ......................................... 14

8.3.1 General ..................................................................................................................................................................................... 14

8.3.2 Porosity or voids (increased power density) ......................................................................................... 14

8.3.3 Surface-connected flaws .......................................................................................................................................... 14

8.4 Applicable flaw-seeding approach as a function of AM process ............................................................. 15

8.5 Applicable flaw-seeding approach as a function of AM material ........................................................... 17

8.5.1 General ..................................................................................................................................................................................... 17

8.5.2 High-density inclusions ............................................................................................................................................. 17

9 Applicable flaw-seeding approach as a function of post processing machining ..........................17

9.1 General ........................................................................................................................................................................................................ 17

9.2 Mechanical machining .................................................................................................................................................................. 17

9.3 Electrode discharge machining replicas ...................................................................................................................... 17

9.4 Laser drilling replicas ................................................................................................................................................................... 17

Bibliography .............................................................................................................................................................................................................................19

iii
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ISO/ASTM TR 52906:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for

the different types of ISO documents can be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www.iso.org/patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO’s adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www.iso.org/iso/foreword.html.

This document was prepared by ISO/TC 261, Additive manufacturing, in cooperation with ASTM

Committee F42, Additive Manufacturing Technologies, on the basis of a partnership agreement between

ISO and ASTM International with the aim to create a common set of ISO/ASTM standards on additive

manufacturing, and in collaboration with the European Committee for Standardization (CEN) Technical

Committee CEN/TC 438, Additive manufacturing, in accordance with the Agreement on technical

cooperation between ISO and CEN (Vienna Agreement).

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www.iso.org/members.html.
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ISO/ASTM TR 52906:2021(E)
Introduction

This document provides information for intentionally seeding flaws in additively manufactured parts

and complements ISO/ASTM TR 52905 .

The different AM building descriptions can be found readily in published standards (see ISO 17296-2)

and scientific papers.

Jargon commonly used in the literature describing AM metal process defect include “balling”,

“fireworks”, “smoke” and often are not specific to the morphology of the defect and often result from

widely differing mechanisms of formation.

When defining terms specific to AM metal flaws it may be useful to review some examples related to

welding technology.

This document is for the creation of seeded replicas supports the user’s understanding not only for the

characterization of actual flaws with respect to physical morphology but also for the materials and

mechanisms of formation, location, and orientation. In addition, the fundamentals of the processes

creating the replica (e.g. PBF or DED with regard to the heat sources electron beam (EB), laser beam

(LB) or AP (arc processes) also need to be considered). The intentional seeding to produce flaw replicas

can match the character of the actual flaw as closely as possible.

The reference photomicrographs or non-destructive testing images included in this document are in no

way to be construed as specifications. These reference photomicrographs and non-destructive testing

images are offered primarily to permit examples of “flaws” or replicate images thereof. They can be

used for comparison of reports. Flaw seeding will be discussed without context to a specific part,

location, or dimension. The material alloy will be provided as known. With some flaws the material

alloy may not be as important, for example, a pore may reside in any number of alloys. It can be noted

that there is currently no proven method for controlled and replicable seeding of intimate disbonds

(sometimes known as “kissing bonds”) – where two surfaces are in intimate or close contact, but with

compromised adhesion – in AM parts so this feature is, therefore, currently out of scope.

This document will not go into the fundamentals of each process but rather identify the parameters

within each process that can lead to the intentional seeding of AM structures.
1) In preparation. Stage at the time of publication ISO/ASTM DTR 52905:2021.
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TECHNICAL REPORT ISO/ASTM TR 52906:2021(E)
Additive manufacturing — Non-destructive testing —
Intentionally seeding flaws in metallic parts
1 Scope

This document is intended to serve as a best practice for the identification and “seeding” of

nondestructively detectable flaw replicas of metal alloy PBF and DED processes. Three seeding

categories are described:
a) process flaws through CAD design;
b) build parameter manipulation;
c) subtractive manufacturing.

These include flaws present within as-deposited materials, post heat-treated or HIP processed

material, and those flaws made detectable because of post-processing operations. Geometrical aspects

or measurement are not the subjects of this document.

WARNING — This document does not purport to address all of the safety concerns, if any,

associated with its use. It is the responsibility of the user of this document to establish

appropriate safety and health practices and determine the applicability of regulatory limitations

prior to use.
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

ISO/ASTM 52900, Standard Terminology for Additive Manufacturing — General Principles —Terminology

ASTM B243, Standard Terminology of Powder Metallurgy
ASTM E7, Standard Terminology Relating to Metallography
ASTM E1316, Standard Terminology for Nondestructive Examinations
3 Terms and definitions

For the purposes of this document, the terms and definitions given in ISO/ASTM 52900, ASTM E7,

ASTM B243, ASTM E1316 and the following apply.

NOTE Terms for AM metal technology flaws are logically divided between PBF and DED categories of

processes.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— IEC Electropedia: available at https:// www .electropedia .org/
— ISO Online browsing platform: available at https:// www .iso .org/ obp
3.1
coupon
piece of material from which a specimen is prepared
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ISO/ASTM TR 52906:2021(E)
3.2
flaw classification

classification approach that provides a high-level system based on a primary characteristic or a

combination of characteristics

Note 1 to entry: Flaw classification may include similar flaw types that were created differently.

3.3
inclusion
foreign material held mechanically

Note 1 to entry: Inclusions are typically oxides, nitrides, hydrides, carbides, or combinations thereof being

formed due to contamination of the chamber gas, or already be present in the metal powder.

3.4
keyhole

type of porosity characterised by a circular depression formed due to instability of the vapour cavity

during processing
3.5
pore

inherent or induced cavity within a powder particle or within an object not connected to an exterior

surface
3.6
porosity
presence of small voids in a part making it less than fully dense
3.7
replica

intentional manipulated condition (flaw) to serve as the “seed” in a coupon (3.1) representing a known

flaw type
3.8
seeding

act of intentionally creating flaws, through CAD or manipulation of designated processing parameters,

that results in the placement of the anticipated replica (3.7) or the act of intentionally creating a replica

(3.7) through the insertion of a foreign object
3.9
sintering

process of heating a powder metal compact to increase density and/or improve mechanical properties

via solid state diffusion
3.10
surface-connected flaw

flaw that is in the body of the material but its boundaries reach to the material’s surface

3.11
unsintered

powder unaffected or affected but not fully consolidated during the additive manufacturing printing

process
4 Abbreviated terms
AM Additive Manufacturing
BM Base Metal
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CAD Computer-Aided Design/Computer-Aided Drafting/Computer-Aided Drawing
CNC Computer Numerical Control
CT Computed Tomography
DDC Ductility-Dip Cracking
DED Directed Energy Deposition
EB-DED Electron Beam Directed Energy Deposition
DR Digital Radiography (non-film)
EB-PBF Electron Beam Powder Bed Fusion
EDM Electrode Discharge Machining
GMA-DED Gas Metal Arc Directed Energy Deposition
HAZ Heat Affected Zone
L-DED Laser Directed Energy Deposition
L-PBF Laser Beam Powder Bed Fusion
NDE Non-destructive evaluation
NDT Non-destructive Testing
OEM Original Equipment Manufacturer
PBF Powder Bed Fusion
PSD Particle Size Distribution
RT Radiography Testing(film)
HIP Hot Isostatic Pressing
Tm Temperature melting point
WM Weld Metal
5 Typical AM flaws

Typically, additive manufacturing flaws in materials fabricated using optimised parameters have small

spherical flaws. Builds with less developed parameters may have a keyhole or larger angular pores.

However, high value components are often screened for flaws at a level determined by fracture analysis

such as those described below. The ability to create replicas to support the NDT detection capability

of complex structures is unique to additive manufacturing and can be considered when standard

inspection techniques are not adequate to ensure inspection reliability.

The occurrence of unintentional flaws during the additive manufacturing build is a possibility. The flaw

classification has been laid out in ISO/ASTM TR 52905 both L-PBF and DED. These flaws are: layer-

defects (horizontal lack of fusion), cross-layer (vertical lack of fusion), unconsolidated powder, trapped

powder, inclusion, layer shift, porosity and void; moreover, incomplete fusion, hole and cracking. It is

important to highlight that some DED defects are similar to those produced during the welding process,

while for L-PBF some defects are unique.
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ISO/ASTM TR 52906:2021(E)

In addition to flaws created to replicate naturally occurring anomalies, replicas may be generated to

serve as targets that can be used to understand x-ray, ultrasonic or other NDT capabilities (see Figure 1).

It is important that the fabricator of such replicas understands the physics of the NDT’s method for

which the flaws will be used. Capabilities demonstrations include detection in a specific complex

[5]

geometry such as a Representative Quality Indicator (RQI) according to ASTM E1817 , or detection

at a specific orientation relating to to the radiation beam. This replica is “seeded” intentionally around

the needs of the demonstrations. Ultrasonic sensing may find applicability through the technical

[3]

approach of ASTM E127 . Additionally, some of these seeding methods are implemented and detection

capabilities of seven NDT methods are assessed in ISO/ASTM TR 52905.

It has been found that replica size, orientation, and location can be designed into the build model to

create shapes (spheres, cubes, and rectangular prisms), sizes (lengths and diameters), and depths. An

example is shown in Figure 1 where embedded defects were designed into the step wedge with CAD

software, and since they are embedded with no powder removal vent, they are filled with unmelted

powder (unconsolidated powder/trapped powder).

a) CAD model showing the set of clusters and dimensions of the holes in the airfoil

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b) XCT scan displaying the visibility of the replicas seeded at different locations

and those that are not visible
Key
1 sets of holes containing 3 cluster
2 number of holes per cluster
3 holes dimensions per cluster
All 4 are visible.
⌀ 0,1 mm not visible.

Figure 1 — Model-designed replicas a), Computed tomography image of a generic airfoil built on

Ti-6Al-4V b)

With adjustments to the optimum build parameters, replicas can provide a desired off-nominal build

parameter. The shape of the replica can be planar, elliptical, rounded or another modelled configuration.

Two such off-nominal build parameters for seeding replicas are lowering laser power and increasing

the trace width larger than optimal.

Both of these types of replicas can be used to show the various NDT methods detection potentials. For

example, the computed tomography scans of the seeding replicas resulted in different yet detectable

material density changes created by each build parameter adjustment. The level of detail and different

views possible through computed tomography is shown in Figure 2 and Figure 3. The images in

both figures are not comparatives as those only illustrate differences in the detail when different

magnifications and methods are used.

Figure 2 — Computed tomography (CT) slice (left) with microscopy image at 50× (right): large

hatch spacing
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Figure 3 — Computed tomography (CT) slice (left) with microscopy image at 50× (right): lower

laser power

Replicas that are open to the surface are producible through the predetermined width dimension in the

model. Figure 4 shows a model used to determine the width capability of the L-PBF machine. These are

linear-type replicas which can have the powder removed. Figure 5 shows the surface in the as-built and

polished conditions.
Figure 4 — Open to the surface replica at different width dimensions
The left image is “as built” and right image is polished.
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ISO/ASTM TR 52906:2021(E)
Figure 5 — As-built coupon of the model in Figure 4
6 Procedure to produce replicas

The introduction of the AM process replicas can be accomplished through the changing of machine

parameters, feedstock conditions or mechanical procedures. The most representative methods are:

— seeding methods;
— AM process manipulation;
— mechanical procedures.
7 Seeding approaches
7.1 General

The following subsections provide seeding approaches for flaw replication using CAD insertion,

manipulation of off-nominal processing and mechanical machining.
7.2 CAD seeding

This is the simplest, most direct, and most accurate method to seed defects on AM parts. Defects of

specific geometries (cylinders, spheres, etc.) are added in the CAD design at specific locations. Some

defects are open to the surface allowing the powder to be released and some are closed geometries

which will have trapped powder. This method is used in ISO/ASTM TR 52905 where artefacts were

built with such seeded defects and then tested with several NDT methods.

The typical AM only flaws were intentionally seeded in the following manner: horizontal cylinders

open to the surface for layer-defects (horizontal lack of fusion), vertical cylinders open to the surface

for cross-layer defects (vertical lack of fusion), spheres and cylinders not connected to the surface for

unconsolidated powder or trapped powder. Inclusions are represented by inserting foreign material

into the surface open seeded defects. Table 1 shows more detail of how this is achieved, while Figure 6

and Figure 7 show examples of a design S1 and the corresponding build in Inconel.

Table 1 — General AM Seeding by CAD design
Defect Classification CAD seed into geometry

Layer defects (horizontal Add horizontally oriented geometrical features to the part geometry at desired locations

lack of fusion) in the part. Geometries can include but not limited to: cylinders, cuboids, etc. Ideally open

to the surface to allow the powder to be released.

Cross Layer (vertical lack Add vertically oriented geometrical features to the part geometry at desired locations in

of fusion) the part. Geometries can include but not limited to: cylinders, cuboids, etc. Ideally open

to the surface to allow the powder to be released.

Trapped powder or un- Add geometrical features to the part geometry at desired locations in the part. Geome-

consolidated powder tries can include but not limited to: spheres, short cylinders, etc.

Layer shift Add such deviations to the CAD design of the part.

Inclusions Using any of the layer and/or cross layer defects insert a determined material in such cavity.

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ISO/ASTM TR 52906:2021(E)
Key
Diameter Length
Region Description
mm mm
Cylinders in various orientations
1 Region 1 (Unconsolidated/trapped powder). Orientation 0,3 2,0
offsets of 45° and 90° relative to the first instance
Vertical cylinders interconnected 0,1, 0,2, 0,3, 0,4, 0,5,
2 Region 2 5,0
and open at both top and bottom 0,6 and 0,7
Spheres (Voids/porosity, unconsolidated/ 0,1, 0,2, 0,3, 0,4, 0,5,
3 Region 3 -
trapped powder) 0,6 and 0,70
Horizontal cylinders open at 0,1, 0,2, 0,3, 0,4, 0,5,
4 Region 4 2,5
the outside edge (Layer defects) 0,6 and 0,7
Horizontal cylinders open at 0,1, 0,2, 0,3, 0,4, 0,5,
5 Region 5 2,0
the inside face of the pentagon (Layer defects) 0,6 and 0,7
Figure 6 — Example design for S1 version of seeded defects
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Figure 7 — An example of an S1 design build on Inconel
7.3 AM process manipulation replicas
7.3.1 General

This seeding is perhaps the more common approach when discussing the seeding of replicas (flaws)

and represents as closely as possible the potential naturally occurring flaws. Table 2 provides a list

of parameter adjustments that can be used for replica creation. It can be understood that the severity

of the replica may or may not match the target flaw. For example, the lack of fusion-type flaw can

vary considerably based on the cause and length of processing time. To compensate for severity,

multiple replicas using a range of the primary process manipulations provide a broader approach to

understanding demonstrable detection.

Many studies have been conducted through the manipulation of off-nominal processing parameters

such as defects – holes or slots, delays – laser on and/or off delays, trace width increase or decrease,

and laser power decrease or increase. Associated with these manipulations is the reference power

or optimal build parameters. Based on the outcome and end-use of the replica, the producer can seed

needed coupons. Table 2 presents the build parameter adjustments to create replica/flaw during the

additive manufacturing process.

Table 2 — Build parameter modifications and powder conditions for flaw formation in the AM

process
Defect Classification Off-nominal build condition
Hatch speed/hatch spacing
Vary/measure powder moisture content (or modify bake-out)
Pore Vary powder or chamber atmosphere purity
Remelt voids into larger or irregular pores
Choose parameter to ensure keyhole formation and collapse
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Table 2 (continued)
Defect Classification Off-nominal build condition
Spread powder layer with a damaged blade, rake, or roller

Choose parameters to create ejecta (“fireworks”), “balling” or “smoke” related defects

Void
Induce intentional process interruption/restart
Beam power spike

Vary constraint or support geometry to increase stress state upon solidification and cooling

Choose an alloy with a decreased level of weldability
Crack

Contaminate the built environment or alloy with a trace alloy to mock improper chamber

cleaning conditions
Beam power, W
Energy density, J/mm
Beam focal offset, spot size, µm
Hatching spacing (line offset), µm
Layer defects (horizon-
Scan speed, m/s
tal lack of fusion) (un-
Scan strategy
consolidated]
Temporary reduction of or turn off the heat source
Halt process, introduce thin layer tracer film, restart process
Induce disturbance typical to process, e.g. leak air into the process gas
Induc
...

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