DETERMINATION OF PVD COATING MECHANICAL PROPERTIES BY NANOINDENTATIONS AND IMPACT TESTS AT AMBIENT AND ELEVATED TEMPERATURES

The performance of physical vapour deposition (PVD) films depends on the operational mechanical and thermal loads of coated tools or components. To withstand these loads, sufficient film strength properties, at ambient and elevated temperatures are required. The present paper deals with the mechanical properties and the impact resistance of cemented carbides and high speed steel specimens, coated with various films, at temperatures up to 400 degrees C. Nanoindentations were conducted by a nanoindentation device, enabling measurements at room and elevated temperatures in an inert gas atmosphere. The obtained results were evaluated using appropriate FEM algorithms for determining the film stress-strain curves, at the temperatures of the conducted nanoindentations. The results reveal a non-linear temperature dependence of the coating properties. Moreover, perpendicular impact tests on the coated specimens were carried out up to 400 degrees C, for investigating the film impact behaviour. The developed impressions were recorded by scanning electron microscopy and white light confocal measurements. The attained results demonstrate a non-linear dependence of the film fatigue properties versus temperature, whereas a significant impact resistance improvement at approximately 150 degrees C develops. Finally, a convergence between the yield and the fatigue endurance stress versus the temperature was revealed.