Overview
ISO 20808:2016 specifies a standardized laboratory procedure - the ball-on-disc method - for determining the coefficient of friction and the specific wear rate of monolithic fine ceramics (advanced/technical ceramics). Tests are performed in pairs (ball vs. disc) under dry, non‑abrasive conditions to produce comparable friction and wear data for material selection, quality control and R&D.
Key topics and requirements
- Test configuration: ball-on-disc contact with the ball pressed against a rotating disc under constant load.
- Specimens:
- Ball: true sphere >5 mm (recommended 10 mm); surface roughness ≤ 0.1 µm Ra (ISO 4287).
- Disc: thickness >3 mm; sliding circle >30 mm diameter; flatness and parallelism within 0.02 mm (ISO 1101); surface roughness ≤ 0.1 µm Ra.
- Ball and disc may be from the same or different ceramic materials; material details (composition, microstructure, heat treatments) must be reported.
- Apparatus & measurements:
- Disc holder, drive system, rigid ball holder, controlled loading mechanism, friction transducer (accuracy ±1% of applied load), optional linear wear measurement (sensitivity ≤2.5 µm).
- Environmental control: temperature ±2 °C, relative humidity 50 ± 10 %.
- Ancillary equipment: balance (0.01 mg), micrometers, profilometer, micrometer microscope.
- Procedure essentials:
- Pre-test cleaning (e.g., ultrasonic acetone rinse, hexane rinse, drying at 120 °C) and storage in test atmosphere.
- Record specimen mass before/after test, measure wear scar on ball and wear track on disc, and calculate specific wear rate and coefficient of friction.
- Key metrics:
- Coefficient of friction μ = Ff / Fp.
- Specific wear rate Ws = V / (Fp × L) (wear volume V, normal force Fp, sliding distance L).
- Recommended conditions (example): applied load 10 N; sliding speed 0.1 m/s; but parameters can be adjusted and must be recorded.
Applications
- Comparative wear and friction evaluation for advanced ceramics used in bearings, seals, cutting tools, engine components, biomedical implants and high-temperature or corrosive environments.
- Material selection and qualification, process optimization, failure analysis, and R&D for new ceramic compositions or surface treatments.
- Establishing baseline tribological data for design engineers and quality labs.
Related standards
Keywords: ISO 20808:2016, fine ceramics, advanced ceramics, ball-on-disc method, friction and wear testing, coefficient of friction, specific wear rate, monolithic ceramics.
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