Hardness-depth profiling on nanometer scale

Three methods for hardness-depth profiling were applied to a 200-nm-thick T iC film deposited onto a Ti-6Al-4V substrate. The methods were evaluated an d compared with regard to their ability to detect local changes in hardness with a depth resolution on the order of a few nanometers. In the cross sec tion method (CSM), the indentations are performed on a cross section of the sample, i.e.. in a direction perpendicular to the hardness gradient. In th e load-variation method (LVM) and in the constant-load method (CLM), the in dentations are made in the direction of the hardness gradient, i.e., perpen dicular to the as-prepared surface. In the LVM, the hardness-depth profile is assessed using a stepwise increase of the maximum load applied to the su rface. In the CLM, sublayers are removed successively by ion sputtering and hardness measurements are performed at each newly exposed surface using th e same low maximum load. The CSM revealed a nearly constant hardness across the TiC film and a sharp transition from the TIC film to the Ti-6Al-4V sub strate. The hardness profile obtained using the LVM and the CLM is smeared out because the recorded response is due to both the TiC film and the under lying softer Ti-6Al-4V substrate.