A comparative study of conventional magnetron sputter deposited and plasma enhanced magnetron sputter deposited Ti–Si–C–N nanocomposite coatings

In this study, Ti–Si–C–N nanocomposite coatings were deposited using Conventional Magnetron Sputtering (CMS) and Plasma Enhanced Magnetron Sputtering (PEMS) techniques on Ti–6Al–4V and Custom-450, a stainless steel used in the turbine industry. The only difference between the CMS and the PEMS is that in the PEMS process a global plasma is generated using hot tungsten filaments, in addition to the magnetron plasma generated in the CMS process. During both the CMS and PEMS depositions, two magnetrons with Ti targets were used in an argon–nitrogen–trimethylsilane gaseous mixture to form Ti–Si–C–N. Then the microstructural, mechanical, and tribological properties of these coatings were studied and compared. The Ti–Si–C–N coatings deposited by both techniques have the same grain size of 5.2 ± 0.1 nm with a cauliflower-like microstructure. However, the CMS coating has a number of embedded micrometer-sized defects and microcracks. The PEMS coating has substantially reduced the number and size of the defects and microcracks. It has also significantly improved the mechanical and tribological properties. The surface microhardness of the PEMS coating (24.65 GPa) is twice as high as that of the CMS coating (11.77 GPa), while the effective elastic modulus of the PEMS coating (331 GPa) is 50% higher than that of the CMS coating (215 GPa). As a result, higher H/E* and H3/E*2 values have been achieved. Finally, the PEMS coating has significantly increased the wear and erosion resistance, while reducing the coefficient of friction slightly.