ISO 26602:2017

Overview

ISO 26602:2017 - "Fine ceramics (advanced ceramics) - Silicon nitride materials for rolling bearing balls and rollers" specifies requirements and a classification system for preprocessed silicon nitride sintered bodies intended for rolling bearing elements. The standard defines physical and mechanical property ranges, microstructure criteria, test methods and reporting requirements to ensure consistent quality of silicon nitride rolling bearing balls and rollers.

Key topics and requirements

• Material classification: Three classes (Class 1, 2, 3) defined by flexural strength, Weibull modulus, Vickers hardness, indentation fracture resistance (IF/KIC), and microstructure limits (pore size and inclusion counts) - see Annex B for detailed limits.
• Physical property ranges: Typical preprocessed rolling element values are specified (e.g., density 3.0–3.6 g/cm³, elastic modulus 270–330 GPa, Poisson’s ratio 0.23–0.29, CTE 2.0–3.7×10⁻⁶/°C, room temperature to 500°C).
• Test methods: Mandated or referenced ISO test methods include:
  • Density (ISO 18754)
  • Elastic modulus and Poisson’s ratio (ISO 17561)
  • Thermal expansion (ISO 17562)
  • Flexural strength and Weibull statistics (ISO 14704, ISO 20501)
  • Hardness (ISO 14705) - recommended Vickers test force HV20 (HV5/HV10 allowed for small samples)
  • Indentation fracture resistance (ISO 14627)
• Microstructure inspection: Annex A gives sample preparation (polishing routes) and observation guidance (optical microscopy at about 100×–200×, or SEM as needed), and limits on pore and inclusion sizes.
• Test report content: The report must reference ISO 26602, list raw powder lot, test date and results (density, modulus, Poisson’s ratio, CTE, flexural strength, Weibull modulus, hardness, fracture resistance, microstructure) and declared material class.

Applications and practical value

• Ensures consistency and interchangeability of silicon nitride rolling elements used in high-speed, high-temperature, or corrosive environments.
• Useful for:
  • Bearing manufacturers and suppliers verifying preprocessed silicon nitride lots
  • Materials engineers and R&D teams developing advanced ceramic rolling elements
  • Quality and testing laboratories performing acceptance testing and certification
  • OEMs and design engineers specifying bearing materials for demanding applications (aerospace, automotive turbochargers, high-speed spindles, industrial machinery)
• Benefits include clearer acceptance criteria, reduced failure risk, and standardized communication between suppliers and customers. Note: ISO 26602:2017 can be applied to processed (finished) balls and rollers by agreement between parties.

Related standards

• ISO 14627 (IF fracture resistance)
• ISO 14704 (flexural strength)
• ISO 14705 (hardness)
• ISO 17561 (elastic moduli)
• ISO 17562 (thermal expansion)
• ISO 18754 (density and porosity)
• ISO 20501 / ISO 20507 (Weibull statistics, vocabulary)

Keywords: ISO 26602:2017, silicon nitride, rolling bearing balls, rollers, fine ceramics, material classification, microstructure, Vickers hardness, Weibull modulus, flexural strength, indentation fracture resistance, test methods.