Microhardness characterization of superlattices formed by reactive magnetron sputtering and ion beam assisted deposition

At present, the development of indentation techniques permits to perform measurements of hardness and other mechanical properties of a material with good accuracy, reproducibility and at a relatively low cost. Nevertheless, since the mechanical contact between indenter and material at low loads is very complex, it is difficult to attribute a hardness value to a film. Several models have been created to solve this problem and are currently in use. The use of particular deposition techniques permits the formation of multilayered coatings with a few nanometers thickness periodicity, which are namely superlattices and are characterized by extremely high hardness. The aim of this paper is to characterize multilayer coatings using the most important nano and microhardness models. The coatings were deposited by reactive magnetron sputtering and ion beam assisted deposition and consists of Cr/V and Ti/TiN layers. The layer periodicity, superlattices wavelengths and elemental characterization were studied by means of grazing angle X-ray diffraction and Rutherford backscattering spectroscopy. The microhardness tests were performed using a computer controlled dynamic load–unload process. The hardness values are either corrected for the indentation size effect or following Oliver–Pharr model. The results show an increase of the hardness values, confirming the development of a superlattice successfully formed by a magnetron sputtering system. The nano and microhardness models show differences in the hardness values obtained, probably due to the difficulty to estimate the real indented area.