High temperature scratch testing of hard PVD coatings deposited on surface treated tool steel.

In this work, a simple and a robust test for the mechanical characterisation of hard PVD coatings at high temperature and open atmosphere has been developed, based on a modification of the scratch test where the diamond tip is replaced by a WC indenter. The test has been used to evaluate the effect of temperature up to 500 °C on commercial PVD AlCrN coating deposited on tool steel subject to different surface treatments. Results show a decrease in the failure load Lc2 with increasing temperature, and a very noticeable effect of substrate nitriding.