ISO 21874:2019
(Main)PVD multi-layer hard coatings — Composition, structure and properties
PVD multi-layer hard coatings — Composition, structure and properties
This document specifies the evaluation standard of the composition, structure and properties of multi-layer hard coatings by common physical vapor deposition (PVD), indicating a vacuum deposition method that produces a material source by evaporation, sputtering or related non-chemical ways.
Revêtements durs multicouches déposés par PVD — Composition, structure et propriétés
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INTERNATIONAL ISO
STANDARD 21874
First edition
2019-10
PVD multi-layer hard coatings —
Composition, structure and properties
Revêtements durs multicouches déposés par PVD — Composition,
structure et propriétés
Reference number
©
ISO 2019
© ISO 2019
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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Samples for composition, structure and properties evaluation . 1
5 Testing of composition, structure and properties . 1
5.1 Testing of chemical composition . 1
5.2 Testing of layer structure . 2
5.3 Testing of surface deficiency . 3
5.4 Testing of thickness . 4
5.5 Testing of properties . 4
5.5.1 Hardness . 4
5.5.2 Friction and wear . 6
Annex A (informative) Sample preparation and operation of transmission electron microscopy .7
Annex B (informative) Example of a surface deficiency rate calculation . 9
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 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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
SC 9, Physical vapor deposition coatings.
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.
iv © ISO 2019 – All rights reserved
Introduction
Multi-layer hard coatings by physical vapor deposition (PVD), which possess high coating-substrate
adhesion, high hardness and good wear resistance, are widely applied on tools and machine parts to
improve their service life. Based on the chemical compositions, the mainstream PVD multi-layer hard
coatings in the market involve transition metal nitrides and carbides, such as Ti/TiN, TiN/CrN, CrN/
AlCrN, TiC/TiCN and CrAlN/AlCrTiSiN. To date, there has been no standard to qualify the composition,
structure and properties of these multi-layer hard coatings, which has limited their further
development.
This document defines the measurement and evaluation of the composition, microstructure, surface
quality, thickness, hardness and tribological properties (such as friction and wear performance) of
multi-layer hard coatings. The methods are for the purpose of coating development. Where standards
for quality assurance in production exist, they are referred to in this document.
INTERNATIONAL STANDARD ISO 21874:2019(E)
PVD multi-layer hard coatings — Composition, structure
and properties
1 Scope
This document specifies the evaluation standard of the composition, structure and properties of
multi-layer hard coatings by common physical vapor deposition (PVD), indicating a vacuum deposition
method that produces a material source by evaporation, sputtering or related non-chemical ways.
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 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 9220, Metallic coatings — Measurement of coating thickness — Scanning electron microscope method
ISO 14577-1, Metallic materials — Instrumented indentation test for hardness and materials parameters
— Part 1: Test method
ISO 20808, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of friction
and wear characteristics of monolithic ceramics by ball-on-disc method
ISO 26423, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of coating
thickness by crater-grinding method
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Samples for composition, structure and properties evaluation
Samples for the composition, structure and properties evaluation should be coated in the same batch
as the products requiring the composition, structure and properties evaluation. The samples should be
polished to a mirror finish (R < 0,05 μm) before being coated and cleaned using ultrasonic agitation,
pk
which immerses them in the correct solution to remove hydrocarbons and other surface contaminants.
5 Testing of composition, structure and properties
5.1 Testing of chemical composition
The chemical composition of PVD multi-layer hard coatings is decided by many factors, including
the composition of the evaporator source, the energy density of incident atoms/ions, the deposition
pressure and the bias voltage. Various elements in the evaporator source can segregate during
deposition, which results in different contents in the coatings. Testing methods that can be used to
characterize the chemical compositions of PVD multi-layer hard coatings are energy dispersive
spectrometer (EDS), electron probe micro analysis (EPMA), X-ray photoelectron spectrometer (XPS),
auger electron spectrometer (AES), secondary ion mass spectrometry (SIMS), X-ray fluorescence (XRF)
and glow discharge optical emission spectroscopy (GDOES). The details are shown in Table 1.
Table 1 — Testing methods of chemical compositions of PVD multi-layer hard coatings
Surface area Cross-sectional area
Testing
Maps and line scans
B, C, N and O B, C, N and O
method
Metal elements Metal elements
elements elements
Recommend-
Recommended Recommended Recommended
ed (monolayer
EDS (excluding Li and (excluding B and (excluding B and Recommended
thickness more
Be) C) C)
than 100 nm)
EPMA Recommended Recommended Recommended Recommended Recommended
Recommended Recommended Recommended
XPS Recommended Recommended
(only by etching) (only by etching) (destructive)
Preferably Preferably
AES Recommended Recommended Recommended
recommended recommended
Preferably Preferably Preferably Preferably Recommended
SIMS
recommended recommended recommended recommended (destructive)
XRF Recommended — — — —
Preferably rec- Preferably rec-
Preferably Preferably Recommended
GDOES ommended (only ommended (only
recommended recommended (destructive)
by etching) by etching)
5.2 Testing of layer structure
Different structures of PVD hard coatings observed by electron microscope, including columnar crystal,
equiaxed crystal and amorphous, lead to different grain or crystallite types, boundary energy and
texture, which influence their hardness, internal stress, toughness and adhesion. Therefore, structure
testing is essential for coating evaluation.
PVD multi-layer hard coatings can be defined in two classes. The first class comprises several different
layers consecutively, including the adhesive layer, transition layer, hard core layer and/or surface
adaptive layer for lubrication, hydrophobicity, electroconductivity, etc, as shown in Figure 1 a). The
other class comprises two kinds of layers, in which every two adjacent layers constitute a unit and the
thickness is called the "modulation period" (Λ = λ + λ ; λ and λ are the thickness of the A layer and
A B A B
B layer, respectively). It is called "nano-layered coating" when Λ is less than 100 nm or "super-lattice
coating", as shown in Figure 1 b).
Methods such as SIMS, scanning electron microscope (SEM) and transmission electron microscope
(TEM) are able to detect and confirm the layer structure of coatings. Detailed information about
analysing the layer structure by TEM is given in Annex A.
2 © ISO 2019 – All rights reserved
a) Several different layers b) Periodic structure
Key
1 adhesive layer 4 modulation layer A
2 transition layer 5 A layer
3 hard core layer 6 B layer
Figure 1 — Typical cross-section structures of PVD multi-layer hard coatings
5.3 Testing of surface deficiency
Droplets often occur in PVD hard coating processes. In addition, defects such as pinholes and shallow
craters can form on the coating surface for some PVD techniques. Figure 2 shows the droplets, pinholes
and shallow craters for arc ion plated coatings. The droplets are mainly from unreacted metal particles.
The pinholes are from the shrinking of grain or crystallites during the coating growth. The shallow
craters are from a spallation of the droplets.
a) b) c)
Key
1 droplet
2 pinhole
3 shallow crater
Figure 2 — Droplets and defects on the surface of arc ion plated coatings
These droplets and defects affect the mechanical properties, such as hardness, friction and wear of
hard coatings, further influencing their service performance. Therefore, it is necessary to calculate the
deficiency rate on the coating surface.
Surface deficiency analysis can be applied to evaluate the surface quality of coatings. Deficiency rate is
defined as the percentage of the area composed of droplets, pinholes and shallow craters divided by the
total observing area. A lower deficiency rate means better surface quality. A maximum value of 10 %
for the deficiency rate should be an acceptable performance of polished coatings.
The steps to calculate the surface deficiency rate are as follows.
a) The surface
...
INTERNATIONAL ISO
STANDARD 21874
First edition
2019-10
PVD multi-layer hard coatings —
Composition, structure and properties
Revêtements durs multicouches déposés par PVD — Composition,
structure et propriétés
Reference number
©
ISO 2019
© ISO 2019
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.
ISO copyright office
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Samples for composition, structure and properties evaluation . 1
5 Testing of composition, structure and properties . 1
5.1 Testing of chemical composition . 1
5.2 Testing of layer structure . 2
5.3 Testing of surface deficiency . 3
5.4 Testing of thickness . 4
5.5 Testing of properties . 4
5.5.1 Hardness . 4
5.5.2 Friction and wear . 6
Annex A (informative) Sample preparation and operation of transmission electron microscopy .7
Annex B (informative) Example of a surface deficiency rate calculation . 9
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 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).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of 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 www .iso
.org/iso/foreword .html.
This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings,
SC 9, Physical vapor deposition coatings.
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.
iv © ISO 2019 – All rights reserved
Introduction
Multi-layer hard coatings by physical vapor deposition (PVD), which possess high coating-substrate
adhesion, high hardness and good wear resistance, are widely applied on tools and machine parts to
improve their service life. Based on the chemical compositions, the mainstream PVD multi-layer hard
coatings in the market involve transition metal nitrides and carbides, such as Ti/TiN, TiN/CrN, CrN/
AlCrN, TiC/TiCN and CrAlN/AlCrTiSiN. To date, there has been no standard to qualify the composition,
structure and properties of these multi-layer hard coatings, which has limited their further
development.
This document defines the measurement and evaluation of the composition, microstructure, surface
quality, thickness, hardness and tribological properties (such as friction and wear performance) of
multi-layer hard coatings. The methods are for the purpose of coating development. Where standards
for quality assurance in production exist, they are referred to in this document.
INTERNATIONAL STANDARD ISO 21874:2019(E)
PVD multi-layer hard coatings — Composition, structure
and properties
1 Scope
This document specifies the evaluation standard of the composition, structure and properties of
multi-layer hard coatings by common physical vapor deposition (PVD), indicating a vacuum deposition
method that produces a material source by evaporation, sputtering or related non-chemical ways.
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 4545-1, Metallic materials — Knoop hardness test — Part 1: Test method
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 9220, Metallic coatings — Measurement of coating thickness — Scanning electron microscope method
ISO 14577-1, Metallic materials — Instrumented indentation test for hardness and materials parameters
— Part 1: Test method
ISO 20808, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of friction
and wear characteristics of monolithic ceramics by ball-on-disc method
ISO 26423, Fine ceramics (advanced ceramics, advanced technical ceramics) — Determination of coating
thickness by crater-grinding method
3 Terms and definitions
No terms and definitions are listed in this document.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https: //www .iso .org/obp
— IEC Electropedia: available at http: //www .electropedia .org/
4 Samples for composition, structure and properties evaluation
Samples for the composition, structure and properties evaluation should be coated in the same batch
as the products requiring the composition, structure and properties evaluation. The samples should be
polished to a mirror finish (R < 0,05 μm) before being coated and cleaned using ultrasonic agitation,
pk
which immerses them in the correct solution to remove hydrocarbons and other surface contaminants.
5 Testing of composition, structure and properties
5.1 Testing of chemical composition
The chemical composition of PVD multi-layer hard coatings is decided by many factors, including
the composition of the evaporator source, the energy density of incident atoms/ions, the deposition
pressure and the bias voltage. Various elements in the evaporator source can segregate during
deposition, which results in different contents in the coatings. Testing methods that can be used to
characterize the chemical compositions of PVD multi-layer hard coatings are energy dispersive
spectrometer (EDS), electron probe micro analysis (EPMA), X-ray photoelectron spectrometer (XPS),
auger electron spectrometer (AES), secondary ion mass spectrometry (SIMS), X-ray fluorescence (XRF)
and glow discharge optical emission spectroscopy (GDOES). The details are shown in Table 1.
Table 1 — Testing methods of chemical compositions of PVD multi-layer hard coatings
Surface area Cross-sectional area
Testing
Maps and line scans
B, C, N and O B, C, N and O
method
Metal elements Metal elements
elements elements
Recommend-
Recommended Recommended Recommended
ed (monolayer
EDS (excluding Li and (excluding B and (excluding B and Recommended
thickness more
Be) C) C)
than 100 nm)
EPMA Recommended Recommended Recommended Recommended Recommended
Recommended Recommended Recommended
XPS Recommended Recommended
(only by etching) (only by etching) (destructive)
Preferably Preferably
AES Recommended Recommended Recommended
recommended recommended
Preferably Preferably Preferably Preferably Recommended
SIMS
recommended recommended recommended recommended (destructive)
XRF Recommended — — — —
Preferably rec- Preferably rec-
Preferably Preferably Recommended
GDOES ommended (only ommended (only
recommended recommended (destructive)
by etching) by etching)
5.2 Testing of layer structure
Different structures of PVD hard coatings observed by electron microscope, including columnar crystal,
equiaxed crystal and amorphous, lead to different grain or crystallite types, boundary energy and
texture, which influence their hardness, internal stress, toughness and adhesion. Therefore, structure
testing is essential for coating evaluation.
PVD multi-layer hard coatings can be defined in two classes. The first class comprises several different
layers consecutively, including the adhesive layer, transition layer, hard core layer and/or surface
adaptive layer for lubrication, hydrophobicity, electroconductivity, etc, as shown in Figure 1 a). The
other class comprises two kinds of layers, in which every two adjacent layers constitute a unit and the
thickness is called the "modulation period" (Λ = λ + λ ; λ and λ are the thickness of the A layer and
A B A B
B layer, respectively). It is called "nano-layered coating" when Λ is less than 100 nm or "super-lattice
coating", as shown in Figure 1 b).
Methods such as SIMS, scanning electron microscope (SEM) and transmission electron microscope
(TEM) are able to detect and confirm the layer structure of coatings. Detailed information about
analysing the layer structure by TEM is given in Annex A.
2 © ISO 2019 – All rights reserved
a) Several different layers b) Periodic structure
Key
1 adhesive layer 4 modulation layer A
2 transition layer 5 A layer
3 hard core layer 6 B layer
Figure 1 — Typical cross-section structures of PVD multi-layer hard coatings
5.3 Testing of surface deficiency
Droplets often occur in PVD hard coating processes. In addition, defects such as pinholes and shallow
craters can form on the coating surface for some PVD techniques. Figure 2 shows the droplets, pinholes
and shallow craters for arc ion plated coatings. The droplets are mainly from unreacted metal particles.
The pinholes are from the shrinking of grain or crystallites during the coating growth. The shallow
craters are from a spallation of the droplets.
a) b) c)
Key
1 droplet
2 pinhole
3 shallow crater
Figure 2 — Droplets and defects on the surface of arc ion plated coatings
These droplets and defects affect the mechanical properties, such as hardness, friction and wear of
hard coatings, further influencing their service performance. Therefore, it is necessary to calculate the
deficiency rate on the coating surface.
Surface deficiency analysis can be applied to evaluate the surface quality of coatings. Deficiency rate is
defined as the percentage of the area composed of droplets, pinholes and shallow craters divided by the
total observing area. A lower deficiency rate means better surface quality. A maximum value of 10 %
for the deficiency rate should be an acceptable performance of polished coatings.
The steps to calculate the surface deficiency rate are as follows.
a) The surface
...
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