Indentation stress–strain analysis and finite element simulation to determine elastoplastic properties of thin films decreasing the substrate contribution

Abstract

AbstractThe mechanical performance of protective coatings is crucial in daily industrial environments, with transition metal nitrides being among the most commonly used hard coatings for machining tool protection. However, determining their elastoplastic properties via conventional methods can be challenging due to the thickness‐dependent response of film/substrate systems. In this study, we utilised two sputtering Ti‐Al‐N films as a model hard thin film/soft substrate system to showcase an alternative methodology to the Oliver and Pharr method. This alternative approach involves determining Young's modulus, yield stress and hardness through indentation stress–strain curves obtained from nanoindentation tests, effectively decreasing the substrate's contribution. This decrease was corroborated by finite element simulations conducted on films with thickness below 1.0 μm. The elastoplastic properties determined using our methodology fell within the range reported for typical Ti‐Al‐N films. Furthermore, by applying our methodology, we were able to correlate and discuss the observed differences in mechanical behaviour between the two films based solely on their microstructural, compositional and morphological properties. Thus, we have demonstrated a viable alternative methodology to address substrate contribution challenges in the mechanical characterisation of thin film/substrate systems when employing an indenter with a large radius of curvature (~650 nm). This research holds potential implications for the design of protective submicrometric films with industrial applications.