Investigation on the structural and mechanical properties of anti-sticking sputtered tungsten chromium nitride films

Tungsten chromium nitride (WCrN) thin films are prepared by dual-gun co-sputter process. As the surface coatings on the molding die for glass forming, WCrN films show less deterioration at high temperature than the conventional CrN coating. WCrN thin films are deposited via the reactive co-sputtering of Cr/W targets. The working pressure is kept at 2.66 Pa and the argon/nitrogen ratio is 10. Applied power of chromium is fixed and the applied power of tungsten is varied. Experimental results indicate that the atomic ratio of tungsten in the films increases with the applied power of tungsten. The dominant crystalline phase is chromium nitride when the tungsten target power is below 100 W, while tungsten nitride dominates in the film structure when the tungsten target power is beyond 200 W. A dense structure with much finer particles is developed as the tungsten power is 200 W. As the power is increased to 300 W, the particles become coarser in size. The film roughness exhibits a decreasing trend at low tungsten power and then increases as the tungsten power increased up to 300 and 400 W, presumably due to the phase change from chromium nitrides to tungsten nitrides. Further annealing of the WCrN thin films is simulated as the glass molding condition to check the anti-sticking property which is a critical requirement in molding die surface coating application. The WCrN thin film coating shows good anti-sticking property at 400 °C annealing when the tungsten target power is 200 W.

► WCrN films are deposited by dual sputtering of pure Cr and W targets.
► The covalent bonding character of WCrN films explains the difference in hardness.
► WCrN (200 W W-target-power/400 °C-annealing) exhibits the best anti-sticking performance.