Overview
ISO 7148-1:2012 - Plain bearings - Testing of the tribological behaviour of bearing materials - Part 1: Testing of bearing metals - specifies standardized tribological tests for metallic plain-bearing materials under boundary lubrication. The standard defines repeatable test procedures to compare friction and wear behaviour of bearing material / mating material / lubricant combinations, enabling informed material selection for low-speed, continuous sliding or repeated operation where hydrodynamic lubrication cannot be guaranteed.
Key topics and requirements
- Scope and limitations
- Tests are for metallic bearing materials under boundary lubrication and low sliding speed; results are comparable only when all influencing parameters are identical. Variability between test facilities is explicitly noted.
- Test methods
- Method A - Pin-on-disc
- Method B - Block-on-ring
- Method C - Rotation under thrust load (sleeve-to-sleeve, sleeve-to-plate)
- Tests require equipment for continuous measurement of friction and wear.
- Test specimens and preferred dimensions
- Disc: diameter 40–110 mm, width 8–12 mm.
- Ring: outside diameter 40–80 mm.
- Pin: diameter 3–10 mm.
- Block: cross-section 5–10 mm (height and width).
- Sleeve and plate dimensions given (machined specimens).
- Specimen preparation
- Machining to application-representative surface finish, cleaning steps (example: alcohol ultrasonic bath, hot-air drying, hexane rinse, drying at 110 °C).
- Test conditions and variables to control
- Initial surface roughness (Ra), normal force (Fn), lubricant temperature (TL), sliding distance, sliding velocity (U), and overlap ratio (K).
- Specific-load guidance: up to about one third of the material’s proof stress or compression limit (as per ISO 4385) for heavily loaded comparisons.
- Lubrication
- Oil or grease as appropriate; full contact lubrication filling recommended (immersion preferred for oil). Oil temperature must be controlled; lubricant choice strongly affects outcomes.
- Designation
- Example: “Test ISO 7148-1 -A” for pin-on-disc testing.
Applications and users
- Practical use:
- Selecting metallic bearing materials for plain bearings operating under boundary lubrication, low speed, or frequent starts/stops.
- Comparative lab evaluation of material/mating/lubricant combinations and wear-rate prediction under controlled conditions.
- Typical users:
- Tribologists, bearing designers, materials engineers, OEMs, test laboratories, and quality/receiving inspection teams involved in bearing selection, development and certification.
Related standards
- ISO 7148-2 (Part 2: polymer-based bearing materials) - companion document for non-metallic bearings.
- ISO 4385 - referenced for compression testing and material limits used in load selection.
Notes: ISO 7148-1:2012 provides test method selection, specimen specs and strict control of variables to produce comparable friction and wear data. When applying results to real-world designs, ensure test parameters closely match the intended service conditions to reduce uncertainty.