The effect of annealing duration at deposition temperature on the strength properties gradation of PVD films and on the wear behaviour of coated cemented carbide inserts

Strength properties alterations may occur in the already deposited film material during the physical vapour deposition (PVD), induced by annealing, at the process temperature. Similar annealing mechanisms occur in PVD films during heat treatments, at a temperature corresponding to the temperature of the deposition. In the described investigations, cemented carbide inserts were coated through high ionisation sputtering PVD processes with a (Ti46Al54)N film, keeping all process parameters constant except the deposition time, which was set according to the desired film thicknesses. The coated specimens were isothermally annealed at deposition temperature for various time periods. The occurred coating superficial stress–strain laws were determined versus the film thickness through nanoindentations and a FEM-based evaluation method of the corresponding results. The detected film strength properties were correlated to the performance of the corresponding coated cutting inserts. In this way, annealing durations dependent on the coating thickness were predicted, enhancing the tool wear resistance in milling. Finally, the obtained results were theoretically explained by means of a FEM-simulation of the cutting process.