The effect of indenter angle on the microindentation hardness

Nix and Gao established an important relation between the microindentation hardness and indentation depth. It agrees well with the microindentation experiments for the Berkovich indenter. However, it is unclear whether it holds for other indenters with different indenter angles. We use the conventional theory of mechanism-based strain gradient plasticity established from the Taylor dislocation model to study the effect of indenter angles on the microindentation hardness. It is shown that the Nix–Gao relation between the microindentation hardness and indentation depth also holds for other indenter angles. The effect of friction is negligible for relatively flat indenters (e.g. Berkovich indenter), but may be significant for sharp indenters (e.g. cubic indenter).