Considerations to the hardness Brinell measurement using optical equipment

A comparison of the results obtained applying the traditional methodology to measure the Brinell hardness value with different optical equipment has been performed. The results show that the measurements on Brinell hardness indentation give neither satisfactory results, nor reproducibility nor precision with respect to certificated values. The fundamental reason is the lack of definition on the indentation edge, where the Brinell indentation diameter should be measured. This causes a high dispersion of the diameters measured with different instruments, operators or measurement parameters.In this work, we propose an alternative measurement methodology using confocal microscopy, which allows to determine a unique indentation edge. This methodology is of high interest for certification of hardness reference blocks because the results are independent of the measuring instrument and the operator.