Microstructural simulations on CrAlN HPPMS coatings

Due to their outstanding mechanical properties, hard coatings possess a wide range of applications as protective layers. However, an experimental determination of the properties of such thin coatings is not only difficult but also cost and time intensive. In this regard, numerical methods, such as the finite element method (FEM), have the ability to reduce the experimental effort, significantly. Usually, for characterisation of hard coatings indentation tests are performed to determine the hardness, the Young's modulus or the adhesive behaviour. With the aid of FE simulations, additional important effects such as residual stresses or the microstructure on material properties can be investigated. In the presented work FE simulations of indentation tests using a Berkovich pyramid were carried out to investigate the mechanical behaviour of hard coatings in depth. During a sensitivity study, FE models with different grain boundary behaviours representing stronger and weaker responses as well as different crystallographic orientations were established and analysed. The performed simulations were validated by indentation test data and cross sections of the coatings. As a result, the incorporation of grain boundary behaviour in the simulation model affects the macroscopic mechanical behaviour of the coating system significantly. Finally, these simulation results deliver insights into the effect of the grain boundaries of the investigated hard coating and can provide suggestions for optimization.