Overview
EN ISO 26423:2016 sets out a standardized method for determining the thickness of ceramic coatings on fine ceramics (advanced ceramics and advanced technical ceramics) using the crater-grinding technique. Published by CEN and aligning with ISO 26423:2009, this European Standard describes a process in which a spherical cavity (crater) is ground into the coated material. The resulting crater is then examined microscopically to measure the thickness of the coating.
The method is particularly valued for its simplicity and effectiveness across a broad range of coated systems. However, it is important to note that the test is not suitable when the surface roughness of either the coating or the substrate exceeds 20% of the coating thickness, as increased roughness can introduce significant measurement uncertainty.
Key Topics
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Scope and Applicability
- Designed for advanced ceramics and technical ceramic coatings
- Unsuitable for surfaces with high roughness (greater than 20% of coating thickness)
- Utilizes a spherical ball wetted with abrasive slurry to create the crater
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Test Method Principle
- Grinding a spherical crater through the coating into the substrate
- Microscopic measurement of the outer and inner diameter of the crater
- Calculation of coating thickness based on geometric relationships and crater dimensions
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Microscopic Examination
- Requires clear contrast between coating and substrate for accurate measurement
- Typically uses optical microscopes, with options for electron microscopy to enhance contrast
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Uncertainty and Accuracy
- Key sources of error: crater roundness, calibration accuracy, and surface preparation
- Measurement uncertainty increases with surface irregularities and poorly defined crater perimeters
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Test Reporting
- Includes required details such as specimen description, test parameters, measured results, and uncertainty assessment
Applications
The crater-grinding method detailed in EN ISO 26423:2016 is widely used throughout the advanced ceramics industry for:
This standard is especially valuable where non-destructive thickness measurement methods are impractical or lack the necessary resolution for thin coatings.
Related Standards
Organizations implementing EN ISO 26423:2016 should refer to related standards for comprehensive quality management and testing protocols, including:
- ISO 3290-1 - Rolling bearings: Specifications for steel balls used in the crater-grinding test
- ISO/IEC 17025 - General requirements for the competence of testing and calibration laboratories, referenced for test reporting and quality assurance
- ISO 18452 - Alternative method for measuring thickness of ceramic films by contact-probe profilometer, suitable when crater-grinding is not applicable
By adopting EN ISO 26423:2016, companies and laboratories benefit from a reliable, repeatable approach to measuring advanced ceramic coating thickness. This promotes uniformity in quality assurance procedures and supports compliance with international best practices in the ceramics industry.