Influencing Parameters of Equivalent Indentation Test

−A newly developed hardness test based on equivalent indentation depth is currently expected to be the only hardness test method that enables seamless evaluations of hardness across different hardness scales in all load ranges from nanoscopic to macroscopic in an industrial friendly manner because the new method is free from the shortcomings of the instrumented indentation method, which requires calibration of tester frame compliance and detection of true specimen surface. However, as it is still in the early days of application, extensive data have yet to be accumulated concerning the equivalent indentation test. In this report, we discuss some major factors that can influence equivalent indentation depth, including the geometrical shape of the indenter used and the load ratio “r” (preliminary-to-total test force ratio). As a result, it is found that the results of the equivalent indentation test using a pyramidal or conical diamond indenter are mutually convertible, and that the difference in equivalent indentation depth among Vickers, Berkovich, and Modified Berkovich indenters, which are probably the most popular indenters for the test, is as small as around ±1%. From our experiments, it is also confirmed that the equivalent indentation test is less susceptible to indenter tip wear than the instrumented indentation test. Understandably, equivalent indentation depth is influenced by load ratio r, but the conversion formula developed by introducing an appropriate model into load curves is found to be effective for mutual conversions of the values of equivalent indentation depth at different load ratios for a practical range of applications.