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

Abstract

Tungsten nitride films (WN X ) were deposited by the cathodic arc method in argon–nitrogen gas mixture changing nitrogen partial pressures. When the N 2/Ar+N 2 ratios were less than 0.1, the films showed α-W with hexagonal structures. On the other hand, the crystal structure changed to cubic W 2N 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 W 2N and hexagonal WN phase showed approximately 13, 24 and 28 GPa, respectively. The surface roughness of WN X 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 WN X were investigated as a function of nitrogen flow and their mechanical properties were studied.