Plain bearings — Dynamic adhesion test method for DLC coated parts under lubricated condition

This document specifies a procedure to measure the adhesion strength of diamond-like carbon (DLC) coatings specified in ISO 20523 by detecting acoustic emission signals using ball-on-disk method under the lubricated condition. DLC is normally coated on metal or ceramic. The test results are not applicable when the DLC coated parts operate in an unlubricated environment.

Paliers lisses - Méthode d'essai d'adhérence dynamique sur des composants revêtus de DLC dans des conditions de lubrification

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Status
Published
Publication Date
17-May-2022
Current Stage
4060 - Close of voting
Start Date
04-Aug-2021
Completion Date
03-Aug-2021
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ISO 4821:2022 - Plain bearings — Dynamic adhesion test method for DLC coated parts under lubricated condition Released:5/18/2022
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INTERNATIONAL ISO
STANDARD 4821
First edition
2022-05
Plain bearings — Dynamic adhesion
test method for DLC coated parts
under lubricated condition
Paliers lisses - Méthode d'essai d'adhérence dynamique sur des
composants revêtus de DLC dans des conditions de lubrification
Reference number
ISO 4821:2022(E)
© ISO 2022
---------------------- Page: 1 ----------------------
ISO 4821:2022(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2022

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© ISO 2022 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 4821:2022(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction .................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ..................................................................................................................................................................................... 1

3 Terms and definitions .................................................................................................................................................................................... 1

4 Specimens.................................................................................................................................................................................................................... 2

4.1 General ........................................................................................................................................................................................................... 2

4.2 Ball specimen ........................................................................................................................................................................................... 2

4.3 Disk specimen ......................................................................................................................................................................................... 2

5 Apparatus .................................................................................................................................................................................................................... 2

5.1 Testing equipment ............................................................................................................................................................................... 2

5.2 Specification of ball-on-disk equipment .......................................................................................................................... 2

5.3 Sample of disk holder ........................................................................................................................................................................ 3

5.4 Sample of ball holder ......................................................................................................................................................................... 3

5.5 Oil bath and equipment for controlling oil temperature .................................................................................. 4

5.6 AE sensor and its holder................................................................................................................................................................. 5

5.7 AE sensor amplifier ............................................................................................................................................................................ 6

5.8 Universal counter for AE events ............................................................................................................................................. 6

6 Testing procedure .............................................................................................................................................................................................. 6

6.1 Pre-treatment of specimen before test ............................................................................................................................. 6

6.2 Set up of adhesion test ..................................................................................................................................................................... 6

6.3 Lubricant ...................................................................................................................................................................................................... 6

6.4 Testing conditions for adhesion test ................................................................................................................................... 6

6.5 Measurement of AE events .......................................................................................................................................................... 7

6.6 Number of test repeats .................................................................................................................................................................... 8

7 Recommendation................................................................................................................................................................................................. 8

7.1 Measurement of friction force .................................................................................................................................................. 8

7.2 Observation of disk after the test .......................................................................................................................................... 8

7.3 Observation of balls after the test ......................................................................................................................................... 8

8 Test report .................................................................................................................................................................................................................. 9

Annex A (informative) Example of stages for adhesion strength tests of coatings applied

to engine parts ....................................................................................................................................................................................................10

Annex B (informative) Example of the dynamic adhesion test result relationship between

the cam/follower tester and ball-on-disk tester ............................................................................................................11

Bibliography .............................................................................................................................................................................................................................13

iii
© ISO 2022 – All rights reserved
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ISO 4821:2022(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

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 123, Plain bearings, Subcommittee SC 7,

Special types of plain bearings.

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 2022 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 4821:2022(E)
Introduction

Reducing the mechanical loss in engines is one of the effective ways to improve the fuel efficiency of

automobiles. To reduce the friction coefficient between engine parts, diamond-like carbon (DLC)

coatings can be applied for plain bearings as well as other sliding parts such as valve lifters and piston

rings.

Since DLC hard coatings have high internal stress due to its coating process under high temperature

and the difference of the coefficient of thermal expansion between DLC and engine parts, the quality

control of the adhesion strength between coatings and base materials of specific parts after the coating

process is very important. As there is no appropriate official test, automobile manufacturers or part

suppliers must validate the adhesion strength by using a specially designed test facility using actual

engine parts. In order to further spread the DLC coatings to mechanical parts of engines in the future, a

test method can be used to easily evaluate the adhesion strength of the coatings.

The purpose of this document is to provide a test method for evaluating adhesion strength of DLC

coatings. The test method specified in this document is a test apparatus equipped with a simple ball-

on-disk that has a correlation with conventional engine evaluation results and a relatively inexpensive

acoustic emission measurement machine without using actual parts.

The positioning of this test method in the process of parts evaluation performed by automobile

manufacturers or part suppliers is shown in Annex A. The correlation between results obtained by the

test method specified in this document and results obtained by the test method using conventional

engine parts is described in Annex B.
© ISO 2022 – All rights reserved
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INTERNATIONAL STANDARD ISO 4821:2022(E)
Plain bearings — Dynamic adhesion test method for DLC
coated parts under lubricated condition
1 Scope

This document specifies a procedure to measure the adhesion strength of diamond-like carbon (DLC)

coatings specified in ISO 20523 by detecting acoustic emission signals using ball-on-disk method under

the lubricated condition. DLC is normally coated on metal or ceramic.

The test results are not applicable when the DLC coated parts operate in an unlubricated environment.

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 683-17, Heat-treated steels, alloy steels and free-cutting steels — Part 17: Ball and roller bearing steels

ISO 1101, Geometrical product specifications (GPS) — Geometrical tolerancing — Tolerances of form,

orientation, location and run-out

ISO 21920-2, Geometrical product specifications (GPS) — Surface texture: Profile— Part 2: Terms,

definitions and surface texture parameters
3 Terms and definitions
For the purposes of this document, the following terms and definitions 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
ball-on-disk method

test method in which the sliding contact between fixed balls and rotating disk specimen

3.2
acoustic emission

physical vibration caused by sudden movement within a material subjected to physical stress, often

symptomatic of a defect
3.3
adhesion strength

load of diamond-like carbon (DLC) coating delamination detected by sharp signal increment of acoustic

emission (3.2)
© ISO 2022 – All rights reserved
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ISO 4821:2022(E)
4 Specimens
4.1 General

Ball and disk specimens having the dimensions described later are prepared. To load equally on each

ball, three balls shall be applied. In the ball-on-disk test, a bearing ball is fixed and used. The disk can

be used as a substrate for a DLC film for testing. All appropriate details regarding the ball and disk

specimens shall be provided, such as their dimensions, surface finish, material type, composition,

microstructure, and processing.
4.2 Ball specimen

The ball specimen shall be 9,525 mm in diameter, made of 100Cr6 material as specified in ISO 683-17,

and is recommended to be the equivalent to G28 or more as specified in ISO 3290-1. The hardness of the

ball is HRC 62-67.
4.3 Disk specimen

The thickness of the disk specimen is 2,5 mm or more. The thickness of the DLC film is 0,1 μm to 10 μm.

In order to set the sliding radius of the ball to 9 mm, the diameter of the test specimen is 28 mm or

more. If the disk has a hole inside, the acceptable inner diameter is 12 mm or less. The surface of the

disk shall be flat and parallel within 0,02 mm as specified in ISO 1101. The roughness of the test surface

shall be less than 0,02 μm Ra as defined in ISO 21920-2. The hardness of the substrate is recommended

to be HRC 60 or more, or 700 HV or more.
5 Apparatus
5.1 Testing equipment

Adhesion strength test using ball-on-disk testing equipment shall consist of the following:

a) the disk holder, for securing a disk specimen;
b) the ball holder, for fixing ball specimens;

c) the equipment, for driving the disk while pressing the ball against the disk with stepwise load;

d) the equipment, for measuring the friction force;
e) the oil bath maintaining lubrication and its temperature;
f) the oil heater, for controlling the oil temperature;
g) the acoustic emission (AE) sensor, for detecting delamination of DLC coating;
h) the AE sensor holder, for detecting AE by way of ball specimens;
i) the equip
...

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