Microstructure Evolution and Mechanical Behavior of Mo–Si–N Films

• Main Authors: Yu-Cheng Liu, Bing-Hao Liang, Chi-Ruei Huang, Fan-Bean Wu
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Coatings
• Subjects: Mo–Si–N; magnetron sputtering; microstructure; hardness; wear
• Online Access: https://www.mdpi.com/2079-6412/10/10/987

The molybdenum silicon nitride (Mo–Si–N) films were deposited by a radio frequency (RF) magnetron reactive dual-gun co-sputtering technique with process control on input power and gas ratio. Composition variation, microstructure evolution, and related mechanical and tribological behavior of the Mo–Si–N coatings were investigated. The N₂/(Ar + N₂) flow ratios were controlled at 10/20 and 5/20 levels with the tuning of input power on the Si target at 0, 100, and 150 W. As the silicon contents increased from 0 to 33.7 at.%, the film microstructure evolved from a crystalline structure with Mo₂N and MoN phases to an amorphous feature with the Si₃N₄ phase. The analysis of selected area electron diffraction patterns in TEM also indicated an amorphous feature of the Mo–Si–N films when Si content reached 20 at.% and beyond. The hardness and Young’s modulus changed from 16.5 to 26.9 and 208 to 273 GPa according to their microstructure features. The highest hardness and modulus were attributed to nanocrystalline Mo₂N and MoN with Si solid-solution. The crystalline Mo–Si–N films showed a smooth tribological track and less wear failure was found. In contrast, the wear track with severe failures were observed for Mo–N and amorphous Mo–Si–N coatings due to their lower hardness. The ratios of <i>H</i>/<i>E</i> and <i>H</i>³/<i>E</i>² were intensively discussed and correlated to the wear behavior of the Mo–Si–N coatings.