Influence of the annealing temperature on a crystal phase of W/WC bilayers grown by pulsed arc discharge

The X-ray diffraction technique was used to study the influence of the temperature on a crystal phase of W/WC bilayer produced by the plasma-assisted pulsed arc discharge. In order to grow the films, a target of W with 99.9999% purity and stainless-steel 304 substrate were used. For the production of W layer, the reaction chamber was filled up with argon gas until reaching a 300 Pa and the discharge was performed at 270 V with 3 pulses. The WC layer was grown in a methane atmosphere at 300 Pa and 275 V discharge voltage with 4 pulses. The active and passive times of the pulsed discharge were 1 and 0.5 s, respectively. The influence of post-annealing temperature of their crystal phases was studied at the post-annealing temperatures up to 600 °C. As-grown layer comprised of mixed phases WC, W2C and W. The post-annealed layer also comprised of the mixed phases of WC, W2C and W at annealing temperatures below 600 °C. At the annealing temperature above 600 °C, XRD diffractograms showed only substrate and W peaks, and tungsten carbide peaks were not observed, but the presence of WO phases were detected for an annealing temperature of 600 °C. XPS analyses showed the presence of WC before the annealing process and the existence of C–C bond that is considered responsible for the high polycrystallinity of the material was also detected. The XPS showed the formation of WO2 and WO3 without the presence of WC for post-annealing at 600 °C.