Prediction of nanoindentation hardness profile from a load-displacement curve

During the nanoindentation process, the load and depth data are continuously recorded. A single load-displacement curve is thus expected to contain material property information from the whole depth range indented. In the present paper, a new method to obtain the hardness-depth curve has been derived for small depths from the load-displacement curve measured at a large depth, based on the assumption that the elastic properties of the indented material can be obtained from the indentation depth. Using this method, hardness values can be computed for various small depths from a single load-displacement curve. From a series of nanoindentation experiments, it has been proven that the method can be used on both homogeneous and surface-modified materials, such as fused silica, single crystal tungsten, and plasma nitrided steel with and without an iron nitride Fe₄N compound layer. Testings on a series of Ni–P films coated on 15 MnB steel also gave fairly good results.