Effect of N2/TMS Gas Ratio on Mechanical and Erosion Performances of Ti-Si-C-N Nanocomposite Coatings

Abstract

To optimize the tribo-mechanical performance of thick Ti-Si-CN nanocomposite coatings for a wide range of harsh industrial applications, reactive gases of nitrogen and trimethylsilane were employed with specific flow rates of PEMS process. Plasma-enhanced magnetron sputtering (PEMS) was employed for depositing thick Ti-Si-C-N nanocomposite (22-27 µm) on Ti-6Al-4V substrates at relatively high deposition rate up to 4.5 µm/h. Controlling the nitrogen partial pressure ratio PN2/(PN2 + PTMS) from 0.29 to 0.69 resulted in controlling the chemical and physical properties of the coatings. The XRD results demonstrated that the crystallinity of the nanocomposite structure increased with the increase in nitrogen pressure ratio. The coating hardness, erosion resistance, sliding wear resistance and corrosion resistance were augmented with increasing the nitrogen content in the plasma atmosphere. The results displayed that the sliding wear resistance of Ti-Si-C-N coatings increased by approximately three orders of magnitude comparing with the uncoated Ti-6Al-4V substrate. At low nitrogen content, low coefficient of friction (0.13-0.15) was achieved. Furthermore, the coating prepared at high nitrogen content reflected greater values of ratios H/E* and H3/E*2 that correlated well with the coating erosion resistance.