ISO 19674:2025
(Main)Fine ceramics (advanced ceramics, advanced technical ceramics) — Methods of test for ceramic coatings — Determination of internal stress in ceramic coatings by application of the Stoney formula
Fine ceramics (advanced ceramics, advanced technical ceramics) — Methods of test for ceramic coatings — Determination of internal stress in ceramic coatings by application of the Stoney formula
This document specifies a method for determination of the internal stress in thin ceramic coatings. The internal stress is determined by application of the Stoney formula to the results obtained from measurement of the radius of curvature of isotropic strips or discs with single-face coating.
Céramiques fines (céramiques avancées, céramiques techniques avancées) — Méthodes d'essai des revêtements céramiques — Détermination de la contrainte interne des revêtements céramiques par application de la formule de Stoney
General Information
Relations
Buy Standard
Standards Content (Sample)
International
Standard
ISO 19674
Second edition
Fine ceramics (advanced ceramics,
2025-06
advanced technical ceramics) —
Methods of test for ceramic coatings
— Determination of internal stress
in ceramic coatings by application
of the Stoney formula
Céramiques fines (céramiques avancées, céramiques techniques
avancées) — Méthodes d'essai des revêtements céramiques
— Détermination de la contrainte interne des revêtements
céramiques par application de la formule de Stoney
Reference number
© ISO 2025
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
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 1
5 Apparatus . 2
6 Preparation of test specimens . 3
6.1 Material .3
6.2 Sample geometry .3
6.3 Sample surface finish . .3
6.4 Sample dimensions .3
7 Procedure . 4
7.1 Measuring range and initial profile .4
7.2 Deposition of the coating .4
7.3 Coating thickness .5
7.4 Adjusting the sample geometry after deposition of the coating .5
7.5 Measuring the final profile .5
7.6 Calculation of stress .6
7.6.1 h / h < 0,02 .6
f s
7.6.2 0,02 ≤ h / h < 0,1 .7
f s
7.7 Number of repeat measurements .7
8 Limits to method . 7
9 Test report . 7
Annex A (informative) Determination of suitable dimensions for the test sample . 9
Annex B (informative) Internal stress calculation in ceramic coating of real components .11
Bibliography .13
iii
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).
ISO draws attention to the possibility that the implementation of this document may involve the use of (a)
patent(s). ISO takes no position concerning the evidence, validity or applicability of any claimed patent
rights in respect thereof. As of the date of publication of this document, ISO had not received notice of (a)
patent(s) which may be required to implement this document. However, implementers are cautioned that
this may not represent the latest information, which may be obtained from the patent database available at
www.iso.org/patents. ISO shall not be held responsible for identifying any or all such patent rights.
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 206, Fine ceramics.
This second edition cancels and replaces the first edition (ISO 19674:2017), which has been technically
revised.
The main changes are as follows:
— in the Scope, the substrate is limited to isotropic ones;
— in Clause 5, the contents of EXAMPLE are all deleted due to an incorrect Formula (2) and its weak
correlation;
— in 7.5, the calculation for R has been revised;
exp
— at the end of 7.5, a schematic diagram (Figure 1) and an approximate calculation of R from deflection
exp
has been added and the formula renumbered to Formula (3);
— Annex B has been added.
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
Introduction
There is an increasing use of coatings to improve the functional performance of materials and components.
This can be to protect against damage due to exposure to demanding environments including high stresses
and aggressive chemical environments, but can also be to modify many other properties, e.g. thermal
conductivity through thermal barrier coatings, friction through low friction coatings, such as diamond like
carbon (DLC), and optical reflectivity through coatings with controlled optical properties.
Appropriate choice of coatings for particular applications depends on the mechanical and other functional
requirements that arise. One factor that can be crucial in determining coating performance and lifetime
is the residual stress that is generated by the deposition process and/or by thermal expansion mismatch
between the coating and the substrate as the component is cooled from the processing temperature.
This document describes the application of a simple experimental technique using the Stoney formula to
analyse the coating induced bending of coupons, of known mechanical properties, to determine the residual
stress in the coating.
v
International Standard ISO 19674:2025(en)
Fine ceramics (advanced ceramics, advanced technical
ceramics) — Methods of test for ceramic coatings —
Determination of internal stress in ceramic coatings by
application of the Stoney formula
1 Scope
This document specifies a method for determination of the internal stress in thin ceramic coatings. The
internal stress is determined by application of the Stoney formula to the results obtained from measurement
of the radius of curvature of isotropic strips or discs with single-face coating.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
No terms and definitions are listed in this document.
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/
4 Principle
Coating stress often plays a major role in the performance of coated tools and machine parts. Different
techniques have been developed for the determination of coating stress. The technique considered in this
document calculates the stress from measurement of the bowing of thin discs or strips of well-characterized
materials of known thickness that have been coated on one side only. It is assumed that the deformation is
elastic, i.e. if the coating were to be removed the substrate would return to its initial shape.
Provided that the coating is thin compared to the thickness of the substrate (coating thickness <2 % of
substrate thickness), that the curvature has a spherical form and that the substrate was initially flat or of
known curvature, then the stress in the coating can be calculated using the Stoney formula (see 7.6) without
the need to know the elastic properties of the coating material.
The technique does require accurate knowledge of the thickness of the coating, the thickness of the
substrate, and Young’s modulus and Poisson’s ratio of the substrate material.
NOTE 1 Coating thickness can be determined by techniques such as step height measurement (see ISO 18452),
[4]
crater grinding (see ISO 26423), and cross-sectioning (see EN 1071-10 ).
As ceramic coatings are normally deposited at elevated temperatures, the stress determined at any other
temperature will be a combination of the intrinsic growth stress and stress introduced by virtue of the
difference in thermal expansion between the coating and the substrate.
The internal stress, σ , in the coating is deduced from the measured radius of curvature, R , through the
0 exp
[6]
application of the Stoney formula as shown in Formula (1):
Eh
1 1
s s
σ =− (1)
61−ν hR
s fexp
where
h is the thickness of the coating;
f
h is the thickness of the substrate;
s
E is Young’s modulus of the substrate;
s
R is the radius of curvature;
exp
ν is Poisson’s ratio of the substrate.
s
NOTE 2 σ is the mean value of the local stress through the thickness of the coating (h << h ):
0 f s
h
f
σσ= z dz (2)
()
0 f
∫
h
f
where σ (z) is the film stress as a function of position perpendicular to the plane of the substrate.
f
The radius of curvature, R , is obtained from the profile of the sample.
exp
5 Apparatus
The profile can be measured by means of an optical profilometer, a high magnification
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.