FprEN ISO/ASTM 52948
(Main)Additive manufacturing of metals - Powder bed fusion - Classification of imperfections (ISO/ASTM FDIS 52948:2025)
Additive manufacturing of metals - Powder bed fusion - Classification of imperfections (ISO/ASTM FDIS 52948:2025)
This document specifies a classification of the imperfections likely to be generated during an additive manufacturing operation by PBF-LB (laser beam powder bed fusion) or PBF-EB (electron beam powder bed fusion) for metal parts. This document also indicates the most probable causes of the formation of imperfections and gives some illustrations taken from feedback.
NOTE This classification applies to both PBF-LB and PBF-EB processes and can be extended to other additive manufacturing processes.
Additive Fertigung von Metallen - Pulverbettfusion - Klassifizierung von Fehlern (ISO/ASTM FDIS 52948:2025)
Fabrication additive de métaux - Fusion sur lit de poudre - Classification des imperfections (ISO/ASTM FDIS 52948:2025)
Dodajalna izdelava kovinskih izdelkov - Spajanje prahu na podlagi (PBF) - Razvrstitev nepravilnosti (ISO/ASTM FDIS 52948:2025)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN ISO/ASTM 52948:2023
01-december-2023
Aditivna proizvodnja kovinskih izdelkov - Neporušitveno preskušanje in
vrednotenje - Razvrstitev nepravilnosti v delih, izdelanih s spajanjem prahu v
postelji (PBF) (ISO/ASTM DIS 52948:2023)
Additive manufacturing for metals - Non-destructive testing and evaluation -
Imperfections classification in PBF parts (ISO/ASTM DIS 52948:2023)
Additive Fertigung für Metalle - Zerstörungsfreie Prüfung und Bewertung - Klassifizierung
von Fehlern in PBF-Teilen (ISO/ASTM DIS 52948:2023)
Fabrication additive de métaux - Essais et évaluations non destructifs - Classification des
imperfections dans les pièces PBF (ISO/ASTM DIS 52948:2023)
Ta slovenski standard je istoveten z: prEN ISO/ASTM 52948
ICS:
19.100 Neporušitveno preskušanje Non-destructive testing
25.030 3D-tiskanje Additive manufacturing
oSIST prEN ISO/ASTM 52948:2023 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN ISO/ASTM 52948:2023
oSIST prEN ISO/ASTM 52948:2023
DRAFT INTERNATIONAL STANDARD
ISO/ASTM DIS 52948
ISO/TC 261 Secretariat: DIN
Voting begins on: Voting terminates on:
2023-10-02 2023-12-25
Additive manufacturing for metals — Non-destructive
testing and evaluation — Imperfections classification in
PBF parts
Fabrication additive de métaux — Essais et évaluations non destructifs — Classification des imperfections
dans les pièces PBF
ICS: 25.030; 19.100
This document is circulated as received from the committee secretariat.
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NATIONAL REGULATIONS.
ISO/ASTM DIS 52948:2023(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
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PROVIDE SUPPORTING DOCUMENTATION. © ISO/ASTM International 2023
oSIST prEN ISO/ASTM 52948:2023
ISO/ASTM DIS 52948:2023(E)
DRAFT INTERNATIONAL STANDARD
ISO/ASTM DIS 52948
ISO/TC 261 Secretariat: DIN
Voting begins on: Voting terminates on:
Additive manufacturing for metals — Non-destructive
testing and evaluation — Imperfections classification in
PBF parts
Fabrication additive de métaux — Essais et évaluations non destructifs — Classification des imperfections
dans les pièces PBF
ICS: 25.030; 19.100
This document is circulated as received from the committee secretariat.
© ISO/ASTM International 2023 THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
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ii
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Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Classification of imperfections . 4
4.1 General . 4
4.2 Designation . 4
4.3 Detailed classification of imperfections occurring in additive manufacturing . 5
4.3.1 General . 5
4.3.2 Cracks . 5
4.3.3 Porosity . . . 5
4.3.4 Inclusions . 5
4.3.5 Lack of fusion . 5
4.3.6 Shape imperfections and dimensional imperfections . 5
4.3.7 Other imperfections . 5
Annex A (informative) Illustration of imperfections and associated visual and
metallographic controls .21
Annex B (informative) Imperfections deriving from issues related to the process or to
the equipment .33
Annex C (informative) Powder imperfections.37
Annex D (informative) Imperfections appearing at subsequent production steps.38
Bibliography .39
iii
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ISO/ASTM DIS 52948:2023(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
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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 should 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).
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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
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).
iv
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ISO/ASTM DIS 52948:2023(E)
Introduction
Metal laser powder bed fusion (PBF) additive manufacturing (AM) using a laser beam (PBF-LB) or an
electron beam (PBF-EB) is in full development. It consists of depositing layers of powder on a tray and
fusing each layer with a laser or electron beam. It is thus possible to produce parts of great geometric
complexity.
The control of this process is the subject of numerous studies to attain the best possible quality. It
is essential to supplement the approaches addressed by these studies with a standard describing
observable imperfections to serve as a basis for non-destructive testing (NDT).
Knowledge of the imperfections generated by the manufacturing process and their standardised
classification are preliminary and essential steps in defining and applying acceptance.
v
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oSIST prEN ISO/ASTM 52948:2023
DRAFT INTERNATIONAL STANDARD ISO/ASTM DIS 52948:2023(E)
Additive manufacturing for metals — Non-destructive
testing and evaluation — Imperfections classification in
PBF parts
1 Scope
This document specifies the classification of imperfections likely to be generated during an additive
manufacturing process by PBF-LB (laser beam powder bed fusion) or PBF-EB (electron beam powder
bed fusion) for metallic parts.
This document also indicates the most probable causes of the formation of imperfections and includes
illustrations.
This can be extended to other additive manufacturing process categories as long as no other related
standard exists.
Acceptance criteria for imperfections are not included in this document.
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 version cited applies. For
undated references, the latest version of the referenced document (including any amendments) applies.
ISO/ASTM 52900, Additive manufacturing — General principles — Fundamentals and vocabulary
ISO 3252, Powder metallurgy — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions of ISO 3252, ISO/ASTM 52900 and the
following apply.
ISO and IEC maintain terminological databases for use in standardisation at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
contour
one or a set of scan trajectories following the edges of the layer
Note 1 to entry: Among scanning strategies, it is very common to use one or more contours, which consist of
paths that follow the edges of the layer.
Note 2 to entry: See Figure 1.
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ISO/ASTM DIS 52948:2023(E)
Key
1 weld bead
2 core scanning strategy
3 geometric edge
4 contour
Figure 1 — Example of a manufacturing strategy using a contour
3.2
downskin area
D
(sub-)area where the normal vector projection on the z-axis is negative
Note 1 to entry: See Figure 2.
[SOURCE: ISO/ASTM 52911-1, 3.2 modified — reference to Figure 2 instead of Figure 1]
Key
normal vector
n
D downskin area (left)
U upskin area (right)
Figure 2 — Upskin and downskin areas U and D (extracted from Figure 1 of ISO/ASTM 52911-1)
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ISO/ASTM DIS 52948:2023(E)
3.3
imperfection
any discontinuity or deviation observed from a specification (geometrical, material integrity)
3.4
lack of fusion
LOF
type of process-induced porosity, in which the powder or wire feedstock is not fully melted or fused
onto the previously deposited substrate
Note 1 to entry: In PBF, this type of flaw can be an empty cavity, or contain unmelted or partially fused powder,
referred to as unconsolidated powder.
Note 2 to entry: LOF typically occurs in the bulk, making its detection difficult.
Note 3 to entry: Like voids, LOF can occur on the build layer plane (layer/horizontal LOF) or across multiple build
layers (cross layer/vertical LOF).
[SOURCE: ISO/TR ASTM 52905, 3.2]
3.5
powder spreading device
layering device
powder supply mechanism, which distributes and evenly spreads the powder on the build surface
[SOURCE: ISO/ASTM 52941, 3.4 modified — addition of accepted term layering device]
3.6
scanning strategy
concept that describes the laser or electron beam path at each layer
Note 1 to entry: The scanning strategy is automatically generated by the machine or by upstream software.
There is a wide variety of scanning strategies.
Note 2 to entry: See Figure 3 where each arrow represents a weld bead.
Figure 3 — Different types of scanning strategy
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ISO/ASTM DIS 52948:2023(E)
3.7
upskin area
U
(sub-)area where the normal vector n projection on the z-axis is positive
Note 1 to entry: See Figure 2.
[SOURCE: ISO/ASTM 52911-1, 3.4 modified — reference to Figure 2 instead of Figure 1]
3.8
bead
continuous line of fused metal
4 Classification of imperfections
4.1 General
The principle of the classification (or numbering) system is based on six groups of imperfections
according to Table 1.
Table 1 — Classification of imperfection by type
Class Imperfection type
1 Crack
2 Porosity
3 Solid inclusion
a
4 Lack of fusion
b
5 Shape imperfection and dimensional imperfection
6 Other imperfection type
a
Also defined as cross-layer or layer on ISO/ASTM TR 52905 and vertical
LoF or Horizontal LoF in ASTM E3166.
b
Equivalent to layer shift in ISO/ASTM TR 52905 and ASTM E3166.
The occurrence of imperfections can be related to issues in the process or the machine (see Annex B),
the powder (see Annex C), or issues arising during stages subsequent to the manufacturing process (see
Annex D).
4.2 Designation
In this document, the imperfection class (or numbering) shall be preceded by the prefix PBF which
corresponds to PBF processes using a laser or electron beam.
When a designation is required for an imperfection, it shall have the following structure:
ISO/ASTM 52948-PBF-[nnn].
With
ISO/ASTM 52948 for reference to this document
PBF indicating powder bed fusion (with laser or electron beam)
nnn classification index according to the type of imperfection (see 4.3)
EXAMPLE The designation ISO/ASTM 52948-PBF-112 according to this document refers to a crack within a
part produced using powder bed fusion.
To simplify reading, in the following imperfections are designated PBF- [nnn].
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oSIST prEN ISO/ASTM 52948:2023
ISO/ASTM DIS 52948:2023(E)
4.3 Detailed classification of imperfections occurring in additive manufacturing
4.3.1 General
For each type of imperfection, the Tables 2 to 7 indicate its designation, position and orientation, an
illustration if applicable, and the main causes and associated comments. Additional illustrations can be
found in Annex A.
4.3.2 Cracks
A crack shall be classified according to Table 2.
NOTE ISO/ASTM 52911-1 on conception on post-treatment provides guidance on how to reduce cracks.
4.3.3 Porosity
Porosity shall be classified according to Table 3.
4.3.4 Inclusions
Inclusions shall be classified according to Table 4.
4.3.5 Lack of fusion
Lack of fusion shall be classified according to Table 5.
4.3.6 Shape imperfections and dimensional imperfections
Shape imperfections and dimensional imperfections shall be classified according to Table 6.
4.3.7 Other imperfections
Other imperfections shall be classified according to Table 7.
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Table 2 — Classification of cracks
PBF Typical
Designation Illustration Main causes and comments
no. location/orientation
These are often cracks of mechanical origin re-
sulting from the presence of significant residual
stresses. These residual stresses and the risk of
Stress concentration
110 Crack NA
cracks are mitigated in the case of preheating build
zone
plate or chamber (in particular in PBF-EB).
They appear after adding the top layers.
Connections between zones, from a geometrical
point of view (no connection radius for example),
from a metallurgical point of view (lack of fusion,
Crack at the interface
or from a mechanical point of view insufficient
between parts/sup-
dimensioning) are frequently to blame.
111 Interface
port or parts/plate or
The process parameters can also be involved. Ma-
Support/plate
terials are unequally sensitive to the phenomenon.
These imperfections can appear during subsequent
heat treatment or cutting.
See also Figure A.1
They are mainly due to the presence of high resid-
ual stresses and the part’s geometry (a solid part
112 Part crack Part with stress concentration zones will be more sensi-
tive). The chosen process parameters also have an
impact, as does the chosen grade.
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ISO/ASTM DIS 52948:2023(E)
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Table 2 (continued)
PBF Typical
Designation Illustration Main causes and comments
no. location/orientation
They are mainly due to the presence of high
residual stresses. An undersizing of the supports
113 Support crack Support is possible. Supports geometry, sizing, and the
process parameters used can also be the cause of
the imperfection.
Cracks in the plate, generally initiated along a part,
are due to residual stresses generated during man-
ufacture which impact the plate. A weak or non-ex-
114 Crack in the plate Plate
istent connection radius between the part and
plate is detrimental, as are solid parts. The process
process parameters also have an important role.
120 Microcrack None NA
They are mainly related to solidification or micro-
structural phase changes.
Metallurgical imperfection, often difficult to detect
121 Microcrack in core Core using NDT due to its size. Some materials, such as
certain nickel alloys, are more sensitive.
NOTE This type of crack is usually only visible
under a microscope (x 50 minimum).
See also Figure A.2
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ISO/ASTM DIS 52948:2023(E)
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Table 2 (continued)
PBF Typical
Designation Illustration Main causes and comments
no. location/orientation
Metallurgical imperfection, often difficult to detect
by NDT due to its size. Some materials are more
sensitive, such as nickel-base alloys and superal-
Microcrack on sur-
loys. This can primarily concern the upper surface.
122 Surface
face
NOTE This type of crack is usually only visible
under an electron microscope by observing the
surface or in section under an optical microscope.
See also Figure A.3
130 Other cracks NA
Cracks come from lack of pre-existing fusion
between layers. A major process parameters issue
can be the cause, especially if the phenomenon
occurs in multiple areas. Poor layering or machine
Multiple cracks in
131 Horizontal plane
shutdown are also possible.
horizontal planes
Cracks appear due to residual stresses associated
with manufacturing or those resulting from heat
treatment.
See also Figure A.4
Imperfection where the surfaces are extremely
close - in partial or direct contact - without bond-
ing in one dimension, having an aspect ratio of
Core (interlayer or
length and/or width to opening of several orders of
132 Contact Crack See also Figure A.5
cross-layer)
magnitude.
NOTE This type of crack is usually only visible in
section under an optical or electron microscope.
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ISO/ASTM DIS 52948:2023(E)
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Table 3 — Porosity classification
PBF Privileged
Designation Illustration Main causes and comments
no. location/orientation
210 Porosity None NA
Spheroidal shape imperfection, due to the cluster-
ing of gas molecules in the metal during solid-
ification. A circular depression formed due to
instability of the vapor cavity during processing
(known as the keyhole effect) can also create this
type of imperfection. Many factors can lead to the
211 Spheroidal Porosity None
formation of porosities, starting with the nature of
the deposited material and the operating condi-
tions (deposition rate, alteration of the gas shield,
moisture in the powder, etc.). Porosities are often
very small in PBF-LB and PBF-EB and difficult to
detect by NDT (<50 µm).
Isolated, distributed spheroidal porosity (see PBF
210). A sudden drop in the solubility of various
Distributed spheroi-
212 None gases between the liquid and solid metal can be the
dal porosities
cause of this imperfection (example: aluminium
alloys)
See also Figure A.6
Isolated porosity of vertical elongated shape
213 Elongated porosity None (especially in the case of a checkerboard strategy
without overlapping) (see PBF 210).
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Table 4 — Classification of inclusions
PBF Privileged
Designation Illustration Main causes and comments
no. location/orientation
The powder can oxidise before or during manufac-
ture. This can be due to gas protection, storage, or
301 Oxide inclusion None
the presence of moisture. Some materials are much
more sensitive to this phenomenon than others.
See also Figure A.7
In PBF-LB, inclusions linked to the spatter during
the part scanning, particularly if the gas flow is
not optimised, if there are a large number of parts
302 Spatter None produced simultaneously, or if the parts are in-
correctly oriented. This can cause lack of fusion in
localised areas and negatively impact the mechani-
cal properties of certain part(s) of the plate.
The powder can be contaminated: during prepara-
tion (element of the crucible found in the powder
- rare case), during manufacture (fragment of a
Exogenous contami-
303 None
blade, for example).
nation
These imperfections are often small in size and
very difficult to detect except using a microscope.
See also Figure A.8
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Table 4 (continued)
PBF Privileged
Designation Illustration Main causes and comments
no. location/orientation
The origin of the imperfection is a pollution by a
different kind of powder.
Poor cleaning of the equipment upstream (from at-
304 Cross contamination None
omization to final use including any handling of the
powder). These imperfections will be of the same
size as the powder and detectable by electronic
microscopy.
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Table 5 — Classification of lack of fusion
PBF Privileged
Designation Illust
...
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