Calibration of depth-sensing indentation instruments: An international intercomparison

A round-robin has been carried out to validate calibration and measurement procedures for various designs of depth-sensing indentation instrument. The procedures used in instrument calibration and for the round-robin exercise are detailed. Hardness and Young's modulus values were obtained for the test materials used in the round-robin experiments over the load range 20-1000 mN. Both hardness and Young's modulus values showed a dependence on load with increasing values at lower loads. The effect was more marked for hardness than for Young's modulus. Uncertainties (95% confidence) in measurement varied greatly between the participants, the best being ±5% and in the worst case this was as great as ±100%. These differences were related both to the calibration accuracy achieved by the different participants and to the repeatability of measurements for the various instruments. Where accurate calibration was possible and instrumentation was adequate, agreement with accepted hardness and Young's modulus values was often better than ±10%; thus the calibration procedures and measurement methods are acceptable and can be considered as suitable for adoption as standards.