Effects of nitrogen concentration on microstructures of WNX films synthesized by cathodic arc method

Tungsten nitride films (WNX) were deposited by the cathodic arc method in argon–nitrogen gas mixture changing nitrogen partial pressures. When the N2/Ar+N2 ratios were less than 0.1, the films showed α-W with hexagonal structures. On the other hand, the crystal structure changed to cubic W2N with the ratios between 0.1 and 0.35. When the ratios exceeded 0.35, the films were hexagonal WN. The micro-hardness of α-W, cubic W2N and hexagonal WN phase showed approximately 13, 24 and 28 GPa, respectively. The surface roughness of WNX films were smooth with approximately 10 nm and, correspondingly, the grains are all small with 10–50 nm in size. In this paper, the changes in crystal structures of WNX were investigated as a function of nitrogen flow and their mechanical properties were studied.