FprCEN ISO/ASTM/TR 52906

Additive manufacturing - Non-destructive testing - Intentionally seeding flaws in metallic parts (ISO/ASTM/DTR 52906:2021)

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.

Additive Fertigung - Zerstörungsfreie Prüfung und Bewertung - Bewusstes Einbringen von Fehlern in Bauteilen (ISO/ASTM/DTR 52906:2021)

Fabrication additive - Essais non destructifs - Implantation intentionnelle de défauts dans les pièces métalliques (ISO/ASTM/DTR 52906:2021)

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.

Aditivna proizvodnja - Neporušitveno preskušanje - Namerno vnešene nepravilnosti v kovinskih delcih (ISO/ASTM PRF TR 52906:2021)

General Information

• Status: Not Published
• Technical Committee: CEN/TC 438 - Additive Manufacturing
• Current Stage: 6055 - CEN Ratification completed (DOR) - Publishing
• Due Date: 28-Apr-2022
• Completion Date: 28-Apr-2022
• Ref Project: kSIST-TP FprCEN ISO/ASTM/TR 52906:2022 - Additive manufacturing - Non-destructive testing - Intentionally seeding flaws in metallic parts (ISO/ASTM PRF TR 52906:2021)

Standards Content (sample)

SLOVENSKI STANDARD
kSIST-TP FprCEN ISO/ASTM/TR 52906:2022
01-februar-2022
[Not translated]

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

parts (ISO/ASTM PRF TR 52906:2021)

Additive Fertigung - Zerstörungsfreie Prüfung und Bewertung - Bewusstes Einbringen

von Fehlern in Bauteilen (ISO/ASTM PRF TR 52906:2021)

Fabrication additive - Essais non destructifs - Implantation intentionnelle de défauts dans

les pièces métalliques ISO/ASTM PRF TR 52906:2021)
Ta slovenski standard je istoveten z: FprCEN ISO/ASTM/TR 52906
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
25.030 3D-tiskanje Additive manufacturing
kSIST-TP FprCEN ISO/ASTM/TR en,fr,de
52906:2022

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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kSIST-TP FprCEN ISO/ASTM/TR 52906:2022
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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kSIST-TP FprCEN ISO/ASTM/TR 52906:2022
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
CP 401 • Ch. de Blandonnet 8 100 Barr Harbor Drive, PO Box C700
CH-1214 Vernier, Geneva West Conshohocken, PA 19428-2959, USA
Phone: [phone] Phone: [phone]
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Published in Switzerland
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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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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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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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kSIST-TP FprCEN ISO/ASTM/TR 52906:2022
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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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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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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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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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

...