Overview
ISO 26443:2023 - "Fine ceramics (advanced ceramics, advanced technical ceramics) - Rockwell indentation test for evaluation of adhesion of ceramic coatings" specifies a qualitative adhesion test for ceramic coatings (and some metallic coatings) up to 20 μm thickness. The standard defines using a Rockwell diamond indenter on a Rockwell hardness tester to produce indentations, then inspects the indent and surrounding area microscopically to classify adhesion and reveal cohesive failure (cracking). The test is not suitable for elastic coatings on hard substrates.
Key topics and technical requirements
- Scope: Adhesion evaluation for coatings ≤ 20 μm; also applicable to some metallic coatings. Not for elastic coatings on hard substrates.
- Test principle: Indentation with Rockwell diamond indenter followed by optical microscopy to detect cracking, flaking or delamination.
- Equipment & references:
- Use Rockwell procedures per ISO 6508-1 (test method).
- Machine/indenter verification per ISO 6508-2.
- Regular indenter contour checks recommended (optical magnification ≥ ×200 to detect ring cracks/microwear).
- Loading rules (select by substrate/coating):
- Metallic substrates harder than 54 HRC: 1 471.5 N (Rockwell C scale).
- Metallic substrates softer than 54 HRC and medium case‑hardened steel: 981 N (Rockwell D).
- Other substrates (ceramics, cermets, thin/soft substrates): 588.6 N (Rockwell A).
- Timing: Loading time 1–8 s and hold time (4 ± 2) s (per ISO 6508-1) - keep constant for repeatability.
- Classification: Results are categorized into Class 0–3:
- Class 0: No cracking/delamination (acceptable).
- Class 1: Cracking without adhesive delamination (acceptable).
- Class 2: Partial adhesive delamination (unacceptable; report % area delaminated).
- Class 3: Complete adhesive delamination (unacceptable; report r/a ratio).
- Inspection: Use optical microscopy (×100) and optional contrast techniques (e.g., Nomarski) to reveal cracks.
- Reporting: Include equipment, calibration, specimen description, load used, at least three test results, and detailed descriptions for class 2/3 failures.
Applications and who uses it
ISO 26443:2023 is intended for:
- Coating engineers, materials scientists, and R&D developing thin ceramic or metallic coatings.
- Quality control and industrial test laboratories performing coating adhesion tests on advanced ceramics, cermets, cemented carbides, and coated metals.
- Failure analysis and comparative evaluation of coating/substrate systems during process development or production qualification.
Practical uses: production QA, comparative adhesion assessment across substrates or coatings, early-stage screening of coating adhesion, and documenting adhesion performance for supplier/customer agreements.
Related standards
- ISO 6508-1 - Metallic materials - Rockwell hardness test - Part 1: Test method
- ISO 6508-2 - Metallic materials - Rockwell hardness test - Part 2: Verification and calibration of testing machines and indenters
Keywords: ISO 26443, Rockwell indentation test, adhesion of ceramic coatings, fine ceramics, Rockwell diamond indenter, coating adhesion test, ceramic coating evaluation.
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