Hardness is frequently measured on advanced or technical ceramics, but accuracy and precision are often poor. An international round robin identified many problems, and errors up to 20% were observed. A prime conclusion was that there was a strong need for calibrated reference blocks. The growing use of ceramic materials specifications and traceability concerns also underscore the need for better test methods and reference blocks. NIST responded by creating Standard Reference Material 2830. The SRM was prepared from a silicon nitride ceramic bearing ball and has five indentations made at a load of 19.8 N (2 kgf) in the center of a polished face. Each SRM is individually certified for the average diagonal length (~142.0 m) and the average hardness (13.86 GPa or 1,414 HK2). Even though diagonal lengths were measured with a calibrated scanning electron microscope, the SRM may be used with conventional hardness machines with optical microscopes. This SRM will support new advanced (advanced technical or fine) ceramic hardness standards ASTM C 1326, ISO 14705, and CEN ENV 843-5.

For additional information, call (301) 975-6776, e-mail srminfo@nist.gov or visit http://ts.nist.gov/ts/htdocs/230/232/232.htm.