Finite Element Prediction for the Internal Stresses of (Ti,Al)N Coatings

The general topic of this paper is the computer simulation with use of finite element method (FEM) for determining the internal stresses of selected gradient and single-layer PVD coatings deposited on the sintered tool materials, including cemented carbides, cermets and Al₂O₃+TiC type oxide tool ceramics by cathodic arc evaporation CAE-PVD method. Developing an appropriate model allows the prediction of properties of PVD coatings, which are also the criterion of their selection for specific items, based on the parameters of technological processes. In addition, developed model can to a large extent eliminate the need for expensive and time-consuming experimental studies for the computer simulation. Developed models of internal stresses were performed with use of finite element method in ANSYS environment. The experimental values of stresses were calculated using the X-ray sin2ψ technique. The computer simulation results were compared with the experimental results. Microhardness and adhesion as well as wear range were measured to investigate the influence of stress distribution on the mechanical and functional properties of coatings. It was stated that occurrence of compressive stresses on the surface of gradient coating has advantageous influence on their mechanical properties, especially on microhardness. Absolute value reduction of internal stresses in the connection zone in case of the gradient coatings takes profitably effects on improvement the adhesion of coatings. It can be one of the most important reasons of increase the wear resistance of gradient coatings in comparison to single-layer coatings.