Effect of Nitrogen Content on the Microstructure and Mechanical Properties of Ti-Mo-N Coating Films

Effects of nitrogen content on the microstructure, hardness, and friction coefficient of Ti-Mo-N coating films were investigated. Ti-Mo-N films were deposited onto an AISI304 stainless steel substrate by reactive r.f. sputtering in the mixture of argon and nitrogen gases with various gas flow rates. The hardness and friction coefficients were measured by nanoindentation and ball-on-disk testing systems, respectively. The hardness of the Ti-Mo-N films increased with increasing a nitrogen gas flow rate ( f_\textN2 ) \left( {f_{{{\text{N}}_{2} }} } \right) and showed a maximum hardness of about 30 GPa at a f_\textN2 = 0.3 \textccm f_{{{\text{N}}_{2} }} = 0.3\,{\text{ccm}} . On the one hand, the films deposited at f_\textN2 3 1.0  \textccm f_{{{\text{N}}_{2} }} \ge 1.0{\text{ccm}} showed a constant hardness value of approximately 25 GPa. On the other hand, the friction coefficient of the Ti-Mo-N film decreased with increasing N content and was 0.44 in the film deposited at f_\textN2 = 2.0  \textccm. f_{{{\text{N}}_{2} }} = 2.0{\text{ccm}}.