ISO 23737:2021

Fine ceramics (advanced ceramics, advanced technical ceramics) - Methods for evaluating wear and friction characteristics of fine ceramic thin films under dry and humid conditions

This document specifies a method for testing the wear resistance and friction coefficient for fine ceramic thin films in dry and high-humidity environments, where such films have a thickness of up to approximately 1 µm and are deposited on a substrate or a base, including a thin substrate or a very thin organic polymer film base.

Céramiques techniques — Méthodes pour l'évaluation des caractéristiques d'usure et de frottement des films minces de céramiques techniques en conditions sèches et humides

General Information

• Status: Published
• Publication Date: 23-Aug-2021
• ICS: 81.060.30 - Advanced ceramics
• Technical Committee: ISO/TC 206 - Fine ceramics
• Drafting Committee: ISO/TC 206/WG 10 - Coatings
• Current Stage: 6060 - International Standard published
• Start Date: 24-Aug-2021
• Due Date: 19-Dec-2021
• Completion Date: 24-Aug-2021

Relations

• Consolidated By: ISO 22300:2025 - Security and resilience - Vocabulary
• Effective Date: 15-Oct-2022

Overview

ISO 23737:2021 specifies standardized methods for evaluating wear resistance and friction coefficient of fine ceramic thin films under controlled dry and high-humidity conditions. The scope covers thin films up to approximately 1 µm thickness deposited on substrates - including thin substrates or very thin organic polymer film bases. This standard is intended to provide reproducible, humidity‑sensitive tribology methods tailored to modern electronic, optical and microdevice ceramic coatings.

Key topics and technical requirements

• Test specimen scope: Fine ceramic (advanced technical) thin films ≤ ~1 µm on rigid or very thin polymer/glass substrates.
• Environmental control: Specified procedures for dry environments (e.g., dry air or nitrogen) and regulated high‑humidity conditions; includes use of drying chambers and defined relative humidity control.
• Measurement principles: Friction coefficient calculation from measured frictional and normal forces; evaluation of wear formation by sliding contact tests.
• Wear motion modes: Defined reciprocating and rotating disc/slide wear conditions to simulate common sliding geometries.
• Specimen preparation & pretreatment: Surface cleaning, drying and thickness measurement requirements prior to testing.
• Wear and damage evaluation:
  • Measurement of wear track cross‑section on thin film surfaces.
  • Determination of worn volume on indenter (ball) surfaces, including profile observation and volume calculation.
  • Morphology and elemental distribution mapping (e.g., imaging and composition analysis) of wear tracks and worn counterfaces.
• Test documentation: Requirements for test procedures, result summarization and test reports; precautions for consistent reporting.
• Relevant definitions: Terms such as wear, frictional force, friction coefficient, dry air/dry nitrogen (dew point −60 °C at 101.3 kPa) are included.

Practical applications and users

ISO 23737:2021 is directly applicable to industries and professionals concerned with thin‑film tribology and reliability, including:

• Materials scientists and ceramic engineers developing fine ceramic coatings for MEMS, sensors, actuators, optical elements, memory and display devices.
• Coating and thin‑film manufacturers evaluating wear resistance and friction behavior under variable humidity.
• R&D and quality control laboratories performing standardized verification of thin‑film durability for electronics, packaging films, automotive glazing and architectural glass.
• Tribology labs and test laboratories offering accredited wear testing services for advanced ceramic thin films.

Using ISO 23737:2021 ensures humidity‑sensitive tribological properties are measured reproducibly, supporting product development, failure analysis and comparative benchmarking.

Related standards

• ISO 20507 - Fine ceramics (vocabulary)
• ISO 3274 - Surface texture: profile method (contact instruments)
• ISO 13565-1 / ISO 13565-2 - Surface texture: filtering, measurement conditions and stratified surface characterization

Keywords: ISO 23737:2021, fine ceramic thin films, wear resistance testing, friction coefficient, dry and high‑humidity tribology, thin film tribology, advanced ceramics.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 23737
First edition
2021-08
Fine ceramics (advanced ceramics,
advanced technical ceramics) —
Methods for evaluating wear and
friction characteristics of fine ceramic
thin films under dry and humid
conditions
Céramiques techniques — Méthodes pour l'évaluation des
caractéristiques d'usure et de frottement des films minces de
céramiques techniques en conditions sèches et humides
Reference number
©
ISO 2021
© ISO 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
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Published in Switzerland
ii © ISO 2021 – All rights reserved

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Test specimens. 2
5 Measurement principle . 2
6 Testing room environment . 2
7 Wear formation test apparatus . 3
8 Test specimen preparation . 5
9 Test specimen pretreatment . 5
9.1 General . 5
9.2 Test specimen cleaning . 5
9.3 Test specimen drying . 5
10 Environmental conditions for the formation of the wear and the evaluation of
friction coefficient . 6
10.1 General . 6
10.2 Dry environment . 6
10.3 High-humidity environment . 6
11 Wear motion conditions . 6
11.1 Reciprocating wear conditions . 6
11.2 Rotating disc wear conditions . 7
12 E valuation of wear track cross-section formed on thin film test specimen surface .8
13 Evaluation of volume of worn portion on indenter ball surface .8
13.1 General . 8
13.2 Observation of indenter ball wear surface profile . 8
13.3 Calculation of volume of worn portion on indenter ball surface . 9
14 Investigations of morphology and elemental distribution maps for wear tracks on
thin film test specimens and worn sections on indenter balls .9
14.1 General . 9
14.2 Observation of the morphology . 9
14.3 Investigations of elemental distribution maps .10
15 Calculation of friction coefficient .10
16 Testing procedures .10
16.1 Measurement of thickness of thin film test specimen .10
16.2 Thin film test specimen preparation and cleaning .10
16.3 Setting of wear formation conditions .10
16.3.1 General.10
16.3.2 Wear formation conditions for a dry environment .11
16.3.3 Wear formation conditions for a high-humidity environment .11
16.4 Wear formation .11
16.4.1 Start of wear formation on the thin film test specimen .11
16.4.2 Friction force measurement .11
16.5 E valuation of thin film test specimen surface and indenter ball surface after wear
formation .11
16.5.1 General.11
16.5.2 Measurement of wear track cross-section on thin film test specimen .11
16.5.3 Evaluation of volume of worn portion on indenter ball surface .11
16.5.4 Investigations of morphology and elemental distribution maps .11
16.6 Calculation of friction coefficient .11
17 Precautions for summarization of test results .12
18 Test report .12
Annex A (informative) Example of reciprocating slide wear results and rotating slide wear
results .13
Annex B (informative) Method of holding polymer film or thin glass plate with a thickness
of < 200 µm in sliding wear formations .15
Annex C (informative) Effects of combining thin film materials and indenter materials
in sliding wear tests.17
Annex D (informative) Investigation of optimal load for indenter .22
Annex E (informative) Quantification of wear track cross-section area .24
Annex F (informative) Examples of investigations of morphology and elemental
distribution maps for wear tracks on thin films and worn sections of indenter balls .25
Bibliography .30
iv © ISO 2021 – All rights reserved

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
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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
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iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 206, Fine ceramics.
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.
Introduction
Fine ceramic thin films are used in a wide variety of applications, such as sensors, actuators or other
micromechanical elements; display elements; memory elements; recording media; optical elements;
packaging films; and films and glass for building construction and vehicles. In the industrial application
of fine ceramic thin films, resistance to wear is an important index for evaluation. The resistance
to wear of fine ceramic thin films is greatly affected by environmental humidity and the humidity
history of the thin film. Fine ceramic thin films are also used in different humidity environments,
necessitating standards for the evaluation of wear resistance and the friction coefficient under a
wide humidity range. Standards published to date concerning wear resistance testing assume only
a temperature environment of 23 °C and a relative humidity of 50 %; the thickness of the thin films
subject to evaluation is also comparatively large, at several to 10 µm. These testing procedures are
inappropriate for evaluating the wear resistance of fine ceramic thin films that have a thickness of up
to approximately 1 µm and are applied for electronic and optical devices, because the wear resistance
for a smaller indentation load is affected by the relative humidity of the test environment, i.e. the
mechanisms employed in the wear test for fine ceramic thin films with a smaller indentation load are
strongly affected by the relative humidity of the test environment. Therefore, the wear test for fine
ceramic thin films should be performed under a regulated relative humidity condition. This document
provides measurement methods that facilitate the accurate evaluation of wear resistance for fine
ceramic thin films in dry and high-humidity environments, where such films have a thickness of up
to approximately 1 µm and are deposited on a thin substrate or an organic polymer film base. This
document has been enacted to facilitate industrial development through the prompt dissemination of
these measurement methods.
vi © ISO 2021 – All rights reserved

INTERNATIONAL STANDARD ISO 23737:2021(E)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Methods for evaluating wear and friction
characteristics of fine ceramic thin films under dry and
humid conditions
1 Scope
This document specifies a method for testing the wear resistance and friction coefficient for fine
ceramic thin films in dry and high-humidity environments, where such films have a thickness of up to
approximately 1 µm and are deposited on a substrate or a base, including a thin substrate or a very thin
organic polymer film base.
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 3274, Geometrical Product Specifications (GPS) — Surface texture: Profile method — Nominal
characteristics of contact (stylus) instruments
ISO 13565-1, Geometrical Product Specifications (GPS) — Surface texture: Profile method; Surfaces having
stratified functional properties — Part 1: Filtering and general measurement conditions
ISO 13565-2, Geometrical Product Specifications (GPS) — Surface texture: Profile method; Surfaces having
stratified functional properties — Part 2: Height characterization using the linear material ratio curve
ISO 20507, Fine ceramics (advanced ceramics, advanced technical ceramics) — Vocabulary
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 20507 and the following apply.
ISO and IEC maintain terminology databases for use in standardization 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
wear
phenomenon leading to progressive loss or progressive displacement from the surface of a solid
material due to motion relative to a contacting body
3.2
frictional force
resistive force exerted on an opposing body when bodies in contact move or tend to slide against each
other
3.3
friction coefficient
dimensionless ratio of frictional force to the normal force applied
3.4
wear test
test for evaluating friction and wear characteristics caused by sliding contact motion
Note 1 to entry: In a narrow sense, the term “wear test” implies the process of wear formation on the test
specimen due to a sliding motion; in a broad sense, it implies procedures such as specimen preparation, wear
formation, friction coefficient measurements, and evaluations of the wear track and the worn portion formed on
the counter material.
3.5
drying chamber
hermetically sealed vessel for eliminating moisture on a test specimen surface while the test specimen
remains held in a vacuum
3.6
relative humidity
ratio of water vapour partial pressure to saturated vapour pressure at a given temperature
3.7
dry air
air with a dew point of −60 °C or lower at an absolute pressure of 101,3 kPa
3.8
dry nitrogen
nitrogen with a dew point of −60 °C or lower at an absolute pressure of 101,3 kPa
4 Test specimens
Use fine ceramic thin films that have a thickness of up to approximately 1 µm and are deposited on
a silicon wafer, glass, organic polymer film or other such substrate or base. Provided that the test
specimens can be fitted on a wear testing apparatus as described in this document, the test specimen
dimensions and shape are of no concern. However, the thickness in the area where the wear formation
is performed shall be uniform.
5 Measurement principle
The wear properties of ceramic thin films are greatly affected by environmental humidity and the
humidity history of the thin film. Consequently, the wear resistance of a thin film test specimen should
be evaluated accurately by measuring wear of the thin film test specimen in dry and high-humidity
environments.
A reciprocating wear formation method or a rotating disc wear formation method shall be used as the
method for evaluating wear. Details of the principles pertaining to a reciprocating wear test method
are given in EN 1071-12. Details of the principles pertaining to a rotating disc wear test method are
given in ISO 20808 and EN 1071-13.
This document addresses both methods, i.e. a reciprocating wear test method and a rotating disc wear
test method. Annex A provides an example of results from testing carried out using a reciprocating
wear test method and a rotating disc wear test method.
6 Testing room environment
Measurements shall be carried out in a location subject to minimal changes in temperature and
humidity. Specifically, testing shall be carried out under the following environmental conditions:
a) testing room temperature: (23 ± 2) °C;
b) testing room relative humidity: 70 % or lower.
2 © ISO 2021 – All rights reserved

NOTE If the temperature of the testing room is low, condensation can form on the wear evaluation apparatus.
7 Wear formation test apparatus
7.1 Reciprocating wear tester: The reciprocating wear tester shall consist of a test specimen
holder which retains a thin film test specimen, a drive apparatus which moves a thin film test specimen
reciprocally, a holder which retains and secures an indenter ball, a loading mechanism which applies a
constant load to the indenter ball, an equipment unit for detecting frictional force and a test environment
control sealing mechanism. Figure 1 shows a schematic of a test specimen holding system for a
reciprocating wear tester. Details concerning the reciprocal wear tester are given in EN 1071-12.
Key
1 indenter with a lateral force measurement system
2 test specimen
3 test specimen holder
4 wear track
Figure 1 — Schematic of a reciprocating wear tester (indicating the test specimen holding
system)
a) The test specimen holder shall move reciprocally within a horizontal plane and the deflection in
the direction of reciprocal motion shall be adjustable to 0,02 mm or less.
b) The drive apparatus shall allow for the setting of a predetermined sliding speed and changes in
the sliding speed due to variations in the frictional force shall be negligible. A reciprocating sliding
motion counter or equivalent device shall be included.
c) The indenter ball holder shall secure the indenter ball reliably against displacement by the frictional
force generated at the area of contact between the indenter ball and the test specimen, and shall
have high rigidity against induced stress.
d) The indenter ball loading mechanism shall apply and maintain a predetermined load either directly
or through a lever, and by means of a weight or a hydraulic or pressurized air system.
e) The frictional force detection equipment can be a load cell or a leaf spring strain measurement,
rotational torque measurement or other such measurement mechanism as desired, but its insertion
shall not affect the frictional conditions. The measurement precision for the frictional force shall
be within 1 % of the applied load. Use of an in situ linear wear measurement apparatus shall be
optional. If used, the apparatus shall have a depth resolution of less than 0,01 µm.
f) A sealing mechanism for controlling the test atmosphere shall be provided.
7.2 Rotating disc wear tester: The rotating disc wear tester shall consist of a test specimen holder
which retains a thin film test specimen, a drive apparatus which moves a thin film test specimen
rotationally, a holder which retains and secures an indenter ball, a loading mechanism which applies a
constant load to a thin film test specimen, a frictional force detection mechanism and a test environment
control sealing mechanism. Figure 2 shows a schematic of a test specimen holding system for a rotating
disc wear tester. Details concerning the rotating disc wear tester are given in ISO 20808.
Key
1 indenter with a lateral force measurement system
2 test specimen
3 test specimen holder
4 wear track
Figure 2 — Schematic of a rotating disk wear tester (indicating the test specimen holding
system)
a) The rotating disc holder shall rotate within a horizontal or vertical plane, the deflection of the
rotational axis shall be adjustable to 0,02 mm or less, and the deflection in the direction of the
rotational axis at the area of contact shall be adjustable to 0,05 mm or less.
b) The drive apparatus shall allow for the setting of a disc rotation speed that provides a predetermined
sliding speed, and changes in the rotational speed due to variations in the frictional force shall be
negligible. A rotational speed counter or equivalent device shall be included.
c) The indenter ball holder shall secure the indenter ball reliably against rotation or displacement
by the frictional force generated at the area of contact between the indenter ball and the disc test
specimen, and shall have high rigidity against induced stress.
d) The indenter ball loading mechanism shall apply and maintain a predetermined load either directly
or through a lever, and by means of a weight or a hydraulic or pressurized air system.
e) The frictional force detection mechanism can be a load cell or a leaf spring strain measurement,
rotational torque measurement, or other such measurement mechanism as desired, but its
insertion shall not affect the frictional conditions. The measurement precision for the frictional
force shall be within 1 % of the applied load. Use of an in situ linear wear measurement apparatus
shall be optional. If used, the apparatus shall have a depth resolution of less than 0,01 µm.
f) A sealing mechanism for controlling the testing environment shall be provided.
7.3 Thermo-hygrostat chamber: The item used shall allow for the setting of relative humidity within
the range of 30 % to 90 % at a temperature of 23 °C. A metal or plastic tube shall be used to introduce air
of a predetermined temperature and humidity into the wear test chamber.
7.4 Dew point meter: The item shall be a capacitance (impedance) hygrometer (dew point meter) or
a chilled mirror dew point meter. Details are given in JIS Z 8806.
7.5 Stylus profilometer: A stylus surface roughness measurement apparatus as specified in
ISO 13565-1 and ISO 13565-2 or one with an equivalent or better precision shall be used.
7.6 Laser interferometric profilometer: The apparatus used shall make use of interference in parallel
light beams with an aligned wave surface to measure the surface profile of a test specimen surface, based
on the interference produced by a phase difference between light reflected from the test piece surface
4 © ISO 2021 – All rights reserved

and light reflected from a reference surface serving as a standard. The apparatus used shall have a height
measurement resolution of approximately 10 nm at a magnification power of approximately 100× to
500×. A coherence scanning interferometry (CSI) system for three-dimensional mapping of surface
height is specified in ISO 25178-604.
7.7 Optical microscope: This apparatus shall magnify an object visually for observation using optical
lenses. The apparatus used shall have sufficient resolution at a magnification power of approximately
100× to 800×.
7.8 Scanning electron microscope: This microscope shall be equipped with a basic function for
forming a magnified image using an appropriate method, e.g. secondary electrons obtained from a test
specimen by two-dimensional scanning during irradiation of a test specimen with a tightly focused
electron beam. The apparatus used shall have sufficient resolution at an observational magnification
power of the order of 5 000×. For ceramic thin films, applying an electroconductive coating prior to the
observation is strongly recommended.
7.9 Energy dispersive X-ray spectroscopy: This instrument shall be equipped with an energy
dispersive X-ray (EDX) spectrometer to provide elemental identification by measuring the energy
of X-rays emitted from a specimen due to excitation by the primary electron beam. An elemental
distribution map can be acquired by combining the EDX signal with the position signal of the scanning
primary electron beam.
7.10 Drying chamber: Provided that the chamber can maintain an internal pressure of 4 kPa or lower
and a temperature of 130 °C or higher, its material, form and other details are not of concern.
7.11 Exhauster: A diaphragm pump or similar item shall be used. Provided that the item has an ultimate
pressure of 4 kPa or lower, its type shall not be of concern.
8 Test specimen preparation
Use the same lot or the same batch to prepare thin film test specimens as needed, allowing for
completion of at least three test runs.
9 Test specimen pretreatment
9.1 General
Pretreat test specimens as needed. If test specimens have been exposed to high humidity, for example
cleaned using water or subject to similar processes, the test specimen shall be dried.
9.2 Test specimen cleaning
If thin film test specimens are dirty, clean them using an organic solvent or a surfactant. If an organic
solvent is used for cleaning, rinse with a sufficient amount of a clean organic solvent and dry naturally
or steam dry with an organic solvent. If a surfactant is used, rinse with a sufficient amount of water
and dry rotationally or by, for example, dry air or hot air drying to remove water. If water is used in
the cleaning, the drying treatment described hereafter shall be performed. If a mineral spirit is used in
cleaning, the solvent shall be only a single boiling point spirit.
9.3 Test specimen drying
Place a thin film test specimen in the drying chamber, bring the pressure in the drying chamber to
4 kPa or lower and the test specimen temperature to 130 °C or higher, and maintain these conditions for
30 minutes. If the substrate cannot be heated to 130 °C or higher, bring the test specimen temperature
to the highest temperature to which the substrate can be heated. After the drying procedure has been
completed, transfer the thin film test specimen promptly to a test apparatus for wear evaluation testing
in a dry environment.
10 Environmental conditions for the formation of the wear and the evaluation of
friction coefficient
10.1 General
The environmental conditions for the formation of the wear and the evaluation of friction coefficient
shall be as follows:
10.2 Dry environment
Replace the atmosphere in the wear test chamber with dry nitrogen or dry air to create a dry
environment under conditions where the temperature is (23 ± 2) °C and the relative humidity is 10 %
or lower. Calculate the relative humidity from the dew point (frost point) measurement results.
10.3 High-humidity environment
Create a high-humidity environment in the wear test chamber under conditions where the temperature
is (23 ± 2) °C and the relative humidity is 70 % to 80 %. To create a high-humidity environment,
introduce air with a predetermined temperature and humidity from the thermo-hygrostat chamber
into the test specimen holding area of the wear tester. Measurements can be performed using the entire
measurement room as a high-humidity environment.
11 Wear motion conditions
11.1 Reciprocating wear conditions
a) Wear area: This area shall be the centre of the thin film test specimen.
b) Stability of test specimen securing area: The test specimen holder shall rotate within a horizontal
or vertical plane, the deflection of the rotational axis shall be adjustable to 0,02 mm or less and
the deflection in the direction of the rotational axis at the area of contact shall be adjustable to
0,05 mm or less.
c) Test specimen securing method: Test specimens shall be pressed from above to prevent any
rattling movement. If the substrate or base is thin, use a vacuum chuck to provide uniform suction
retention. In the case of retention by suction, due consideration shall be given to the flatness of the
test specimen surface after retaining by suction, as indicated in Annex B.
d) Indenter ball material, diameter and surface roughness: The indenter ball material shall be
304 stainless steel (ISO 4301-304-00-I, EN 10088 X5CrNi18-10 or JIS SUS304), 440C stainless
steel (ISO 4023-440-04-I, EN 10088 X105CrMo17 or JIS SUS440C), Al O (purity: > 99,99 %;
2 3
hardness: > 1 500 HV), SiC (purity: > 99,9 %; hardness: > 2 200 HV), Si N (ISO 3290-2;
3 4
purity: > 95,0 %; hardness: > 1 600 HV) or another such material. The ball specimen shall be a
true sphere with a diameter of 5 mm to 20 mm. The recommended ball diameter is 10 mm. The
surface roughness of the indenter ball should preferably be 0,01 µm or less. The surface roughness
(Ra – arithmetical mean roughness value) of the indenter ball shall be determined as needed by
measuring the roughness curve at the equator of the indenter ball using a measuring instrument
as specified in ISO 3274 and determining the mean roughness on the centre line. Pay due attention
to the fact that the test results can differ depending upon the combination of the thin film test
specimen material and the indenter ball material that is used. Annex C provides examples of
wear testing results produced by different combinations of thin film test specimen materials and
indenter ball materials.
6 © ISO 2021 – All rights reserved

e) Indenter ball cleaning: Clean the indenter ball in pure water prior to use by performing ultrasonic
cleaning, and dry with warm alcohol or alcohol steam. If a mineral spirit is used in cleaning, the
solvent shall be only a single boiling point spirit.
f) Indenter ball load: The indenter ball load shall be approximately 0,50 N or lower. An appropriate
indenter ball load for the fine ceramic thin film test specimen should be determined by pre-testing.
Annex D presents results from reciprocating wear testing with varying loads.
g) Reciprocating movement frequency: 1 Hz.
h) Indenter ball movement speed: 33,3 mm/s.
i) Indenter ball movement stroke: 10 mm.
j) Wear oscillating cycles: 1 000 oscillating cycle. In the case of low wear, the cycle number can be
increased to 5 000 cycles. In the case of high wear, where the coating thickness is worn down to the
substrate, 500 cycles are sufficient.
k) Number of tests: Test at least three specimens under identical conditions.
11.2 Rotating disc wear conditions
a) Test specimen wear area: This area shall be the centre of the thin film test specimen.
b) Stability of test specimen securing area: The test specimen holder shall rotate within a horizontal
or vertical plane, the deflection of the rotational axis shall be adjustable to 0,02 mm or less, and
the deflection in the direction of the rotational axis at the area of contact shall be adjustable to
0,05 mm or less.
c) Test specimen securing method: Disc-shaped testing specimens shall be secured in a disc holder.
If the substrate or base is thin, use a vacuum chuck to provide uniform suction retention. In the
case of retention by suction, due consideration shall be given to the flatness of the test specimen
surface after retaining by suction, as indicated in Annex B.
d) Indenter ball material, diameter and surface roughness: The indenter ball material shall be
304 stainless steel (ISO 4301-304-00-I, EN 10088 X5CrNi18-10 or JIS SUS304), 440C stainless
steel (ISO 4023-440-04-I, EN 10088 X105CrMo17 or JIS SUS440C), Al O (purity: > 99,99 %;
2 3
hardness: > 1 500 HV), SiC (purity: > 99,9 %; hardness: > 2 200 HV), Si N (ISO 3290-2;
3 4
purity: > 95,0 %; hardness: > 1 600 HV) or another such material. The ball specimen shall be a true
sphere with a diameter of 5 mm to 20 mm. The recommended ball diameter is 10 mm. The surface
roughness of the indenter ball should preferably be 0,01 µm or less. The surface roughness of the
indenter ball shall be determined as needed by measuring the roughness curve at the equator of
the indenter ball using a measuring instrument as specified in ISO 3274 and determining the mean
roughness on the centre line. Pay due attention to the fact that the test results can differ depending
upon the combination of the thin film test specimen material and the indenter ball material that
is used. Annex C provides examples of wear testing results produced by different combinations of
thin film test specimen materials and indenter ball materials.
e) Indenter ball cleaning: Clean the indenter ball in pure water prior to use by performing ultrasonic
cleaning, and dry with warm alcohol or alcohol steam. If a mineral spirit is used in cleaning, the
solvent shall be only a single boiling point spirit.
f) Indenter ball load: The indenter ball load shall be approximately 0,50 N or lower. An appropriate
indenter ball load for the fine ceramic thin film test specimen shell be determined by pre-testing.
Annex D presents results from reciprocating wear formation with varying loads.
g) Sliding radius: More than 12,5 mm (if less, the curvature of the wear track can affect results).
h) Indenter ball sliding speed: 33 mm/s.
i) The number of sliding revolutions: 2 000 rotational cycles (revolutions). In the case of low wear,
the cycle number can be increased to 10 000 cycles. In the case of high wear, where the coating
thickness is worn down to the substrate, 1 000 cycles are sufficient.
j) Number of tests: Test at least three test specimens under identical conditions.
12 E valuation of wear track cross-section formed on thin film test specimen
surface
Perform ultrasonic cleaning with pure water before performing an evaluation of the wear track cross-
section. The cleaning time shall be 10 minutes. In ultrasonic cleaning, oscillate the test specimen to
provide for uniform cleaning. After ultrasonic cleaning has been completed, dry the test specimen. The
drying shall be performed by immersion in a warm alcohol bath or exposure to alcohol steam followed
by natural drying, rotational drying or other such means.
Profile the cross-section of the wear track formed on the thin film test specimen by using a stylus
profilometer or a laser interferometric profilometer, as specified in Clause 7. Annex E provides an
example of the method for quantifying a wear cross-section.
Measurements shall be performed at three points, generally near 3 mm, 5 mm and 7 mm, in reciprocating
wear formation and at four points with an interval of 90° within the wear circle in rotating disc
wear formation. If the formation of extreme excrescences or similar features is observed, change the
measurement points or perform the ultrasonic cleaning again to obtain a grooved wear mark profile.
Calculate the wear volume from the cross-sectional area for rotating disc wear formation by using
Formula (1), if needed.
π×+RS()SS++S
12 34
V = (1)
where
V is the wear volume of thin film test specimen (m );
R is the radius of the wear track (m);
S to S represent the cross-sectional area at four places on the wear track circle (m ).
1 4
13 Evaluation of volume of worn portion on indenter ball surface
13.1 General
Observe the morphology of the worn portion on the indenter ball surface. From the results of the
morphology observation, the volume of the worn portion shall be evaluated by the following methods.
13.2 Observation of indenter ball wear surface profile
Observe the worn portion on the indenter ball surface by using a laser interferometric profilometer, an
optical microscope or a scanning electron microscope, as specified in Clause 7.
8 © ISO 2021 – All rights reserved

13.3 Calculation of volume of worn portion on indenter ball surface
Calculate the volume of the worn portion on the indenter ball surface by using Formula (2), based on
the shortest diameter of the worn portion mark measured in accordance with 14.2 and a diameter
perpendicular to the same. Figure 3 shows the schematic of the worn portion on the indenter ball.
πAB
V = (2)
ball
32D
where
V is the indenter ball wear volume (m );
ball
A is the shortest diameter of the worn portion (m);
B is the diameter in the direction perpendicular to the shortest diameter of the worn portion (m);
D is the indenter ball diameter (m).

Key
A shortest diameter of the worn portion (m)
B diameter in the direction perpendicular to the shortest diameter of the worn portion (m)
D indenter ball diameter (m)
Figure 3 — Quantification of the wear volume of the indenter ball
This formula is an approximation which simplifies the complex three-dimensional profile of a wear
mark. If the wear mark profile is greatly distorted (B > 1,5 A), for reasons such as a deep wear mark in
the sliding area of a thin film test specimen, this formula shall be deemed inapplicable. Refer to EN 1071-
13.
14 Investigations of morphology and elemental distribution maps for wear tracks
on thin film test specimens and worn sections on indenter balls
14.1 General
Investigate the morphology and elemental distribution maps for the wear tracks formed on the thin
film test specimen surface and the worn sections formed on the indenter ball surface. From the results
of the morphology and elemental distribution map investigations, the debris adhesion on the wear
tracks and the worn sections on the indenter ball shall be evaluated.
14.2 Observation of the morphology
Observe the morphology of the wear track surface and the indenter ball surface by using a scanning
electron microscope, as specified in Clause 7. The observational magnification shall depend on the
wear track width, but it shall generally range from 500× to 2 000× . Annex F provides examples of
observations of the morphology of the wear track surface and the indenter ball surface.
14.3 Investigations of elemental distribution maps
Investigate elemental distributions on the wear track surface and the indenter ball surface by using
energy dispersive X-ray spectroscopy, as specified in Clause 7. Annex F provides examples of elemental
distribution maps of the wear track surface and the indenter ball surface.
15 Calculation of friction coefficient
In the wear formation process, the friction coefficient can be obtained as an extraneous value. Calculate
the friction coefficient by using Formula (3) based on the applied load and the mean frictional force.
F
f
μ= (3)
F
n
where
μ is the friction coefficient;
F is the mean frictional force (N);
f
F is the applied load (N).
n
In reciprocating wear motion, the dynamic friction coefficient and static friction produced by
approximately 10 sliding strokes shall be measured as the friction coefficients for the starting wear,
interim wear and ending wear, and their mean shall be taken (e.g. 1 000 measurements of reciprocating
wear are taken as strokes 0 to 10, 501 to 510 and 901 to 910).
In measurements for rotating disc wear motion, the friction coefficient shall be obtained by measuring
it continuously. Alternatively, the dynamic friction coefficient shall be calculated for the starting wear,
interim wear and ending wear rotations, and their mean shall be obtained (e.g. 2 000 measurements of
rotating wear are taken as rotation laps 0 to 10, 1 001 to 1 010 and 1 801 to 1 810).
16 Testing procedures
16.1 Measurement of thickness of thin film test specimen
Measure the thickness of each thin film test specimen and the uniformity of its thickness. A method
for measuring this thickness is not designated in this document, but a method with adequate precision
shal
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