ISO 4499-2:2020

Overview

ISO 4499-2:2020 - Hardmetals - Metallographic determination of microstructure - Part 2: Measurement of WC grain size - provides standardized guidelines for metallographic measurement of tungsten carbide (WC) grain size in WC/Co hardmetals (cemented carbides, cermets). The document prescribes optical and electron microscopy methods, with a strong recommendation for the linear‑intercept (mean-linear-intercept, LI) technique to obtain statistically meaningful average grain-size values. It includes calibration, measurement, analysis and reporting requirements and is supported by a measurement case study (Annex A).

Key topics and technical requirements

• Scope: Applies to WC/Co hardmetals (not intended for routine powder characterisation). Excludes recommendations for size distribution and shape measurements.
• Recommended method: Linear‑intercept (Heyn) technique for mean WC grain size; conversion to equivalent circle diameter (ECD) is discussed (ECD ≈ 1.13 × LI).
• Microscopy: Use of optical microscopy, SEM, FESEM and EBSD is covered; TEM may be required for extremely fine grains. FESEM is recommended for ultrafine and nano grades.
• Calibration: Images must be calibrated against stage micrometers or certified graticules (e.g., SIRA grids) traceable to national standards to ensure measurement accuracy.
• Sampling & statistics: Guidance on product sampling and microstructure sampling to collect sufficient, statistically meaningful intercept data and to control systematic and random errors.
• Measurement limits: Practical minimum intercept lengths and considerations for very large or very small WC grains are specified.
• Reporting: A structured reporting approach is required to meet modern quality and traceability needs (see Annex B proforma).

Applications and users

ISO 4499-2:2020 is intended for professionals who need robust, repeatable WC grain‑size measurement:

• Metallurgists and materials scientists in the powder metallurgy and cemented carbide industries
• Quality control and inspection laboratories for hardmetal production
• R&D teams developing cutting tools, wear parts and cermets
• Failure analysis and process development engineers seeking microstructure–property correlations

Practical uses include process control, specification verification, comparative research, and material certification where WC grain size directly impacts hardness, toughness and wear behaviour.

Related standards

• ISO 4499-1 (metallographic preparation) - essential companion for specimen prep
• ISO 4489:2019 (sampling and testing)
• ISO 3369 (density)
• ISO 6507-1 to -4 (Vickers hardness test series)
• ASTM and other metallography references are discussed for additional context

Keywords: ISO 4499-2:2020, hardmetals, WC grain size, metallographic measurement, linear-intercept, SEM, FESEM, EBSD, cemented carbides, grain-size measurement.