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Nanoindentation testing of gear steels

Abstract A combination of nanoindentation testing and atomic force microscopy (AFM) has been used to accurately determine the hardness and elastic modulus of gear steels. The results confirmed that the conventional analysis method due to Oliver and Pharr tends to greatly overestimate the hardness and elastic modulus due to the effect of pile-up by about 25 %. Hardness and Young’s modulus calculated using the slopes method are overestimated by about 10%. AFM offers a reliable method for measuring the area of contact because the indentations are relatively well-defined in gear steel samples. Two correction factors, kH = 0:82 and kE = 0:75 have been determined and applied in the Oliver and Pharr formulas for hardness and elastic modulus, respectively. The corrected values are in good agreement with those expected.