Investigation on plastic behavior of HPPMS CrN, AlN and CrN/AlN-multilayer coatings using finite element simulation and nanoindentation

Abstract

Abstract A comprehensive investigation of hard coatings deposited by physical vapor deposition (PVD) requires, in addition to the elastic properties, a precise knowledge of their plastic behavior. Nanoindentation is a commonly applied method to determine the hardness and the elastic modulus of PVD coatings. Determination of flow curve of PVD thin coatings using a combination of nanoindentation and finite element (FE) simulation is the subject of current research. In the presented work, nanoindentation tests with a Berkovich tip, in combination with its FEM simulation, were used to determine the plastic flow curves of CrN, AlN and CrN/AlN-multilayer coatings deposited by high power pulse magnetron sputtering (HPPMS) PVD on cemented carbide substrates. The applied FEM model was used to simulate the indentation process. The details of the FEM model and the applied experimental and analytical methods are discussed. The determination of the simulative flow curves was carried out according to the Johnson–Cook model and by finding the coefficients of the considered plastic flow model. The coefficients were determined by comparing the simulated and measured maximum forces, and additionally, by correlating the indentation imprints after nanoindentation tests in simulation and experiment. The correlation was performed by depth profiling of the indentation imprints using confocal laser scanning microscopy (CLSM) and atomic force microscopy (AFM). The plastic behavior of the studied coating systems was analyzed combining the simulated flow curves and the results of the analysis of indentation imprints. The results show a higher resistance of the nanostructured CrN/AlN-multilayer coating against plastic deformation compared to CrN and AlN. This is most likely due to the nm-sized alternating layers and the fine grained morphology of the CrN/AlN-multilayer compared to the pure coatings, which hinders the dislocation motion.