The effect of heat treating on the microstructure and mechanical properties of Cr-Cu-N nanocomposite thin films

The Cr-Cu-N nanocomposite thin films with copper contents ranging from 1.6 to 24.1 at.% were deposited on silicon wafer substrates using a bipolar asymmetry pulsed DC reactive magnetron sputtering system. A dense and compact structure was observed for the thin film containing higher than 10.2 at.% Cu, whereas columnar structures were revealed on the coatings with less than 10.2 at.% Cu. Heat treatments of the as-deposited thin films were held in a vacuum tube furnace at 400, 450 and 500 degrees C for 30 minutes, respectively. It was observed that the copper atoms would diffuse to the surface to form oxide particles on the coating contained higher Cu content after heating higher than 450 degrees C. The quantity and size of the oxide particles increased with increasing heating temperature and Cu content in the thin film. The hardness of coatings increased after heating except #D thin film containing 24.1 at.% Cu, which the softening effect was found after heating at 500 degrees C. A granular and less dense cross-sectional morphology was observed on #D coating after heat treating at 500 degrees C, which was responsible for the lower hardness of thin film.