SIST EN ISO/ASTM 52948:2026

SLOVENSKI STANDARD
01-maj-2026
Dodajalna izdelava kovinskih izdelkov - Spajanje prahu na podlagi (PBF) -
Razvrstitev nepravilnosti (ISO/ASTM 52948:2026)
Additive manufacturing of metals - Powder bed fusion - Classification of imperfections
(ISO/ASTM 52948:2026)
Additive Fertigung von Metallen - Pulverbettfusion - Klassifizierung von Fehlern
(ISO/ASTM 52948:2026)
Fabrication additive de métaux - Fusion sur lit de poudre - Classification des
imperfections (ISO/ASTM 52948:2026)
Ta slovenski standard je istoveten z: EN ISO/ASTM 52948:2026
ICS:
25.030 3D-tiskanje Additive manufacturing
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO/ASTM 52948
EUROPEAN STANDARD
NORME EUROPÉENNE
January 2026
EUROPÄISCHE NORM
ICS 19.100; 25.030
English Version
Additive manufacturing of metals - Powder bed fusion -
Classification of imperfections (ISO/ASTM 52948:2026)
Fabrication additive de métaux - Fusion sur lit de Additive Fertigung von Metallen - Pulverbettfusion -
poudre - Classification des imperfections (ISO/ASTM Klassifizierung von Fehlern (ISO/ASTM 52948:2026)
52948:2026)
This European Standard was approved by CEN on 26 December 2025.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
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concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
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United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO/ASTM 52948:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO/ASTM 52948:2026) has been prepared by Technical Committee ISO/TC 261
"Additive manufacturing" in collaboration with Technical Committee CEN/TC 438 “Additive
Manufacturing” the secretariat of which is held by AFNOR.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by July 2026, and conflicting national standards shall be
withdrawn at the latest by July 2026.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
Any feedback and questions on this document should be directed to the users’ national standards
body/national committee. A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland,
Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of
North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the
United Kingdom.
Endorsement notice
The text of ISO/ASTM 52948:2026 has been approved by CEN as EN ISO/ASTM 52948:2026 without
any modification.
International
Standard
ISO/ASTM 52948
First edition
Additive manufacturing of metals —
2026-01
Powder bed fusion — Classification
of imperfections
Fabrication additive de métaux — Fusion sur lit de poudre —
Classification des imperfections
Reference number
ISO/ASTM 52948:2026(en) © ISO/ASTM International 2026

ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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© ISO/ASTM International 2026 – All rights reserved
ii
ISO/ASTM 52948:2026(en)
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 .5
4.3 Detailed classification of imperfections occurring in additive manufacturing .5
4.3.1 General .5
4.3.2 Crack .6
4.3.3 Porosity . . .6
4.3.4 Inclusions .6
4.3.5 Lack of fusion .6
4.3.6 Shape, dimensional and surface imperfections .6
4.3.7 Other imperfections .6
Annex A (informative) Illustration of imperfections and associated visual and metallographic
controls .22
Annex B (informative) Imperfections deriving from issues related to the process or to
the equipment .36
Annex C (informative) Powder imperfections.40
Annex D (informative) Imperfections appearing at subsequent production steps. 41
Bibliography .42

© ISO/ASTM International 2026 – All rights reserved
iii
ISO/ASTM 52948:2026(en)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards
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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 2026 – All rights reserved
iv
ISO/ASTM 52948:2026(en)
Introduction
Industrial additive manufacturing (AM) with powder bed fusion (PBF) processes for metallic materials,
using a laser beam (PBF-LB/M) or an electron beam (PBF-EB/M), is in full development. The principle is
based on depositing layers of powder on a build platform and selectively fusing each layer with a laser or an
electron beam. It is thus possible to produce parts of high 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) and destructive testing (DT).
Knowledge of the imperfections generated by the manufacturing process and their standardised
classification are preliminary and essential steps in defining and determining acceptance criteria.

© ISO/ASTM International 2026 – All rights reserved
v
International Standard ISO/ASTM 52948:2026(en)
Additive manufacturing of metals — Powder bed fusion —
Classification of imperfections
1 Scope
This document specifies the classification of imperfections possibly 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, nevertheless, the indication of
probable causes is process specific.
Acceptance criteria and dimensional description or scale 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 3252, Powder metallurgy — Vocabulary
ISO/ASTM 52900, Additive manufacturing — General principles — Fundamentals and vocabulary
ASTM B243, Standard Terminology of Powder Metallurgy
3 Terms and definitions
For the purposes of this document, the terms and definitions of ISO 3252, ISO/ASTM 52900, ASTM B243 and
the following apply.
ISO and IEC maintain terminology 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
bead
continuous line of fused metal
3.2
contour
one or a set of scan trajectories following the edges of a part on a layer
Note 1 to entry: Among scanning strategies (see 3.8), it is very common to use one or more contours, which consist of
paths that follow the edges of a part on a layer.
Note 2 to entry: See Figure 1.

© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
Key
1 bead
2 core scanning strategy
3 geometric edge
4 contour
Figure 1 — Example of a manufacturing strategy using a contour

3.3
downskin area
D

(sub-)area where the outward-pointing normal vector n projection on the Z-axis is negative
Note 1 to entry: See Figure 2.
[SOURCE: ISO/ASTM 52911-1:2019, 3.2, modified — Inclusion of "outward-pointing".]
Key

n normal vector
D downskin area (left)
U upskin area (right) (see 3.9)
Figure 2 — Upskin and downskin areas U and D (extracted from Figure 1 of ISO/ASTM 52911‑1:2019)

© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
3.4
imperfection
departure of a quality characteristic from its intended condition
[SOURCE: ISO/TS 18173:2005, 2.13]
3.5
inclusion
foreign material, either non-metallic or metallic, incorporated into the deposited material
Note 1 to entry: Inclusions are typically oxides, nitrides, hybrids, carbides, or a combination thereof and may or may
not have some coherency with the surrounding material.
[SOURCE: ASTM E3166-20]
3.6
lack of fusion
LOF
type of process-induced porosity, in which the powder 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: Lack of fusion typically occurs in the bulk, making its detection difficult.
Note 3 to entry: Like voids, lack of fusion can occur on the build layer plane (layer/horizontal LOF) or across multiple
build layers (cross layer/vertical LOF).
[SOURCE: ISO/ASTM TR 52905:2023, 3.2 modified — Deletion of "or wire".]
3.7
powder spreading device
powder supply mechanism, which distributes and evenly spreads the powder on the build surface
[SOURCE: ISO/ASTM 52941:—, 3.4]
3.8
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 bead and its direction.
Note 3 to entry: Scanning strategy can refer to both the path and process parameters along these paths such as laser
power, laser speed, beam shape, etc.

© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
Key
A stripes
B checkboard pattern
C parallel beads
D layer N
E layer N+1
F layer N+2
Figure 3 — Different types of scanning strategy

3.9
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 52911-1:2019, 3.4 modified — Reference to Figure 2 instead of Figure 1.]
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.
© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
Table 1 — Classification of imperfection by type
Class Imperfection type
1 Crack
2 Porosity
3 Inclusion
a
4 Lack of fusion
b
5 Shape, dimensional and surface imperfection
6 Other imperfection type
a
Also defined as cross-layer or layer on ISO/ASTM TR 52905 and vertical lack
of fusion or horizontal lack of fusion 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).
NOTE Valuable recommendations and guidance on the use of established and emerging non-destructive testing
(NDT) procedures to inspect metal parts made by additive manufacturing, are available in ASTM E3166. Valuable
recommendations and guidance on the use of post-process non-destructive testing of additive manufactured metallic
parts with a comprehensive approach, are available in ISO/ASTM TR 52905. Guidance on non-destructive in-process
monitoring methods can be found in ASTM E3353.
4.2 Designation
In this document, the imperfection class (or numbering) shall be preceded by the prefix PBF/M which
corresponds to PBF processes using a laser or electron beam for metallic parts.
When a designation is required for an imperfection, it shall have the following structure:
ISO/ASTM 52948-PBF/M [nnn].
With
ISO/ASTM 52948 for reference to this document
PBF/M indicating powder bed fusion (with laser or electron beam) for metallic parts
nnn classification index according to the type of imperfection (see 4.3)
EXAMPLE The designation ISO/ASTM 52948-PBF/M 112 according to this document refers to a crack within a
part produced using powder bed fusion.
To simplify reading, the following imperfections are designated PBF/M [nnn].
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 typical causes and associated comments. Additional illustrations can be
found in Annex A.
Illustrations within the tables are given labels defined at the foot of the tables, i.e. commentary about the
colour and pattern of components of the illustrations, such as the build direction.

© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
4.3.2 Crack
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, dimensional and surface imperfections
Shape, dimensional and surface imperfections shall be classified according to Table 6.
4.3.7 Other imperfections
Other imperfections shall be classified according to Table 7.

© ISO/ASTM International 2026 – All rights reserved
ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 2 — Classification of cracks
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
Often of mechanical origin resulting from the pres-
ence of significant residual stresses. These residual
stresses and the risk of cracks are mitigated in the
case of preheating the build platform or chamber
Stress concentration
110 Crack NA
(in particular in PBF-EB).
zone
They appear after adding the top layers.
Heat treatments such as stress relieving reduce the
risk of cracking.
Inadequate transition between parts and supports,
or between parts and build platform, or support
and build platform. The residual stress exceeds the
Crack at the interface
strength of the interface between parts/supports,
between parts/sup-
or parts/build platform or support/build platform.
111 port or parts/build Interface
platform or support/
The process parameters can also be involved. Ma-
build platform
terials are unequally sensitive to the phenomenon.
These imperfections can appear during subsequent
heat treatment or cutting.
See also Figure A.1
High residual stresses and the part’s geometry (a
solid part with stress concentration zones is more
112 Part crack Part
sensitive). The chosen process parameters also
have an impact, as does the chosen alloy.

ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 2 (continued)
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
High residual stresses. An undersizing of the sup-
Support crack or ports is possible. Support geometry, sizing, and the
113 Support
breakage process parameters used can also be the cause of
the imperfection.
Residual stresses generated during manufacture
which impact the build platform. A weak or non-ex-
Crack in the build
114 Build platform istent connection radius between the part and build
platform
platform is detrimental, as are solid parts. The
process parameters also have an important role.
120 Microcrack None NA NA
Solidification or microstructural phase changes.
Metallurgical imperfection, often difficult to detect
using NDT due to its size. Some materials, such
121 Microcrack in core Core as precipitation hardened nickel alloys, are more
sensitive.
NOTE This type of crack is usually only visible
under a microscope (×50 minimum).
See also Figure A.2
ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 2 (continued)
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
Metallurgical imperfection, often difficult to detect
by NDT due to its size. Some materials are more
sensitive, such as nickel-base alloys. This can pri-
Microcrack on sur-
marily 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 NA NA
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 shutdown are also
Multiple cracks in
131 Horizontal plane
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 bonding
in one dimension, having an aspect ratio of length
Core (interlayer or
and/or width to opening of several orders of magni-
132 Contact crack See also Figure A.5
cross-layer)
tude. Causes as per 131 above.
NOTE This type of crack is usually only visible in
section under an optical or electron microscope.
Key to illustrations:
1  part
2  platform
3  support
Z  Z-axis
ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 3 — Classification of porosities
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
210 Porosity None NA NA
Clustering of gas molecules in the metal during
solidification. 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 conditions
(deposition rate, alteration of the gas shield, mois-
ture in the powder, etc.). Porosities are often very
small in PBF-LB and PBF-EB and difficult to detect
by NDT (<50 µm).
Sudden drop in the solubility of various gases
Global spheroidal
212 None between the liquid and solid phases (example: alu-
porosities
minium alloys)
See also Figure A.6
Departure from nominal processing conditions, e.g.
213 Cluster porosity None
short spreading of powder.
ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 3 (continued)
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
Lack of overlapping of beads in adjacent layers, e.g.
214 Elongated porosity None
checkerboard pattern strategy (see Figure 3).
Key to illustrations:
1  part
2  platform
Z  Z-axis
ISO/ASTM 52948:2026(en)
© ISO/ASTM International 2026 – All rights reserved
Table 4 — Classification of inclusions
Typical causes and comments
PBF/M Typical
Designation Illustration
no. position/orientation
(non‑exhaustive)
300 Inclusion None NA NA
The powder can oxidise or create another phase
before or during manufacture. This can be due to
Non-metallic inclu- gas protection, storage, or the presence of moisture.
301 None
sion Some materials are much more sensitive to this
phenomenon than others. The shape depends on the
type of inclusion.
See also Figure A.7
Spatter typically occurs due to turbulent flow in the
melt pool as well as vapor.
302 Spatter None
This can cause lack of fusion in localised areas and
negatively impact the mechanical properties of
certain part(s).
The powder can be contaminated: during prepara-
tion (element of the crucible found in the powder
- rare case), during manufacture (fragment of a
External contamina-
303 None
blade, for example).
tion
These imperfections are often small in size and
very difficult to detect except using a microscope.
See also Figure A.8
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 are of the same size
as the powder and detectable by electron micros-
copy.
...