FEM applied to evaluate composite hardness of SiO₂ Film/316 LSS substrate system

Due to non-ideal tip, performance of instrument and substrate effect, it is difficult to evaluate either composite mechanical properties of thin film/substrate system or the pure film's properties. In order to get composite hardness of thin film and how the substrate takes effect of the film's properties, FEM is used to simulate the indentation process of SiO₂ thin films on 316LSS. With experiments, we observe that the hardness heavily depends the thickness of SiO₂ film with different thickness deposited on 316 LSS by PVD. By FEM simulation and calculation, composite hardness is found to decrease greatly with increasing indentation depth. As thickness of film keeps constant, there exists a critical indentation depth about 1/20 of film thickness, less than which composite hardness may be regarded as film hardness. Discussion indicates FEM analysis method in this paper may not only play role in determining composite hardness of thin film/hardness system, but also provide a method to calculate pure hardness of thin film.