ISO 22680:2020

Metallic and other inorganic coatings - Measurement of the linear thermal expansion coefficient of thermal barrier coatings

This document specifies a method for measuring the reproducible linear thermal expansion coefficient of ceramic top coats (TCs) for thermal barrier coatings (TBCs) up to 1 300 °C.

Revêtements métalliques et autres revêtements inorganiques — Mesure du coefficient de dilatation thermique linéaire des revêtements barrières thermiques

General Information

• Status: Published
• Publication Date: 26-May-2020
• ICS: 25.220.40 - Metallic coatings
• Technical Committee: ISO/TC 107 - Metallic and other inorganic coatings
• Drafting Committee: ISO/TC 107/WG 1 - Thermal spraying
• Current Stage: 9093 - International Standard confirmed
• Start Date: 24-Sep-2025
• Completion Date: 13-Dec-2025

Relations

• Consolidated By: ISO 23936-1:2022 - Oil and gas industries including lower carbon energy - Non-metallic materials in contact with media related to oil and gas production - Part 1: Thermoplastics
• Effective Date: 06-Jun-2022

Overview

ISO 22680:2020 specifies a standardized method to measure the linear thermal expansion coefficient of ceramic top coats (TCs) used in thermal barrier coatings (TBCs) - up to 1 300 °C. It addresses reproducible measurement of TC dilatation behavior (not the metallic bond coat or substrate) and fills a gap left by standards that target monolithic ceramics. The procedure covers specimen preparation, apparatus requirements, measurement cycles and reporting essentials.

Key topics and technical requirements

• Scope and principle
  • Measures mean linear thermal expansion coefficient α(T) of ceramic top coats of TBCs.
  • Requires repeated heating cycles because TCs commonly show unstable expansion during initial cycles; testing continues until a reproducible value is reached.
• Specimen preparation
  • TC is separated from the TBC (chemical stripping or mechanical machining) into a free-standing plate.
  • Minimum specimen size: length ≥ 10 mm, width ≥ 5 mm, thickness ≥ 0.5 mm; thickness chosen to avoid warping.
• Apparatus and setup
  • Typical components: furnace, push rod, load control, differential transformer, recorder and thermocouple (tip close to specimen per ISO 17562).
  • Supporting jig must allow free dilatation, prevent tilting, be chemically compatible with specimen; high-purity alumina recommended.
  • Calibration required using a reference specimen per ISO 17139.
• Measurement procedure
  • Heating rate: 1 °C/min to 5 °C/min.
  • Push-rod contact force: 0.1 N to 1 N.
  • Temperature increment for computing α(T): approximately 50 °C.
  • Repetition continues until the criterion Z(T) ≤ 5% is met - i.e., the relative difference between successive measurements is within 5%.
• Reporting
  • Must include specimen details, apparatus and materials, force/heating/atmosphere, number of measurements, expansion curve and α(T) values, and any deviations.

Applications and users

ISO 22680:2020 is relevant to:

• Coating manufacturers (plasma-sprayed, EB-PVD, etc.) validating TC thermomechanical properties.
• Turbine OEMs and aero/industrial gas-turbine component designers evaluating TBC performance.
• Materials and thermal-mechanical testing laboratories performing quality control and R&D.
• Researchers studying high-temperature behavior of ceramic coatings for engine and power-generation applications.

Keywords: ISO 22680:2020, thermal barrier coatings, linear thermal expansion coefficient, TBC, ceramic top coat, thermal expansion measurement, high-temperature testing.

Related standards

• ISO 17139 - thermophysical properties of ceramic composites (reference specimen & apparatus calibration)
• ISO 17562 - push-rod technique for monolithic ceramics (thermocouple placement guidance)
• ISO 14188 - TBC thermal cycle and shock test methods

This standard ensures consistent, reproducible measurement of TC thermal expansion, supporting reliable material selection, coating development and component life prediction at elevated temperatures.

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 22680
First edition
2020-05
Metallic and other inorganic
coatings — Measurement of the linear
thermal expansion coefficient of
thermal barrier coatings
Revêtements métalliques et autres revêtements inorganiques —
Mesure du coefficient de dilatation thermique linéaire des
revêtements barrières thermiques
Reference number
©
ISO 2020
© ISO 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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Published in Switzerland
ii © ISO 2020 – All rights reserved

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus for measuring the linear thermal expansion coefficient .3
5.1 Apparatus . 3
5.2 Supporting jig . 4
6 Specimen . 4
6.1 Test specimen . 4
6.2 Reference specimen . 5
7 Measuring procedure . 5
8 Test report . 5
Annex A (informative) An example of the measurement of the linear thermal expansion
coefficient of a TC . 7
Bibliography . 9
Foreword
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This document was prepared by Technical Committee ISO/TC 107, Metallic and other inorganic coatings.
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iv © ISO 2020 – All rights reserved

Introduction
Thermal barrier coatings are highly advanced material systems, generally applied to surfaces of hot-
section components made of nickel or cobalt-based superalloys, such as combustors, blades and vanes
of power-generation gas turbines in thermal power plants and aero-engines operated at elevated
temperatures.
The function of these coatings is to protect metallic components for extended periods at elevated
temperatures by employing thermally insulating materials that can sustain an appreciable temperature
difference between load bearing alloys and coating surfaces. These coatings permit the high-
temperature operation by shielding these components, thereby extending their lives.
Although the linear thermal expansion coefficient is an important property of thermal barrier coatings,
the existing International Standard (e.g. ISO 17562) describes only a method for measuring this
parameter for monolithic ceramics.
This document specifies a method for measuring the linear thermal expansion coefficient of the ceramic
top coat for thermal barrier coating.
INTERNATIONAL STANDARD ISO 22680:2020(E)
Metallic and other inorganic coatings — Measurement of
the linear thermal expansion coefficient of thermal barrier
coatings
1 Scope
This document specifies a method for measuring the reproducible linear thermal expansion coefficient
of ceramic top coats (TCs) for thermal barrier coatings (TBCs) up to 1 300 °C.
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 3611, Geometrical product specifications (GPS) — Dimensional measuring equipment: Micrometers for
external measurements — Design and metrological characteristics
ISO 17139, Fine ceramics (advanced ceramics, advanced technical ceramics) — Thermophysical properties
of ceramic composites — Determination of thermal expansion
ISO 17562, Fine ceramics (advanced cer
...