The effect of the gas mixture ratio on 316 L stainless steel bio material's mechanical properties and crystal structures using DC sputtering technique

Stainless steel type of 316L is widely used as an orthopedic implant due to its high corrosion resistance and biocompatibility, but the weakness of these materials is low hardness and high wear. The surface must be modified to improve the material. For the purpose, a titanium nitride (TiN) thin film was deposited on the surface of stainless steel 316L using DC sputtering technique. The sputtering process was carried out for various of a gas mixture of argon (Ar) and nitrogen (N₂ ) of 90:10, 80:20, 70:30, and 60:40, while the other parameters kept constant. The objective of the gas mixture variation was to find out the optimum condition of ratio Ar: N₂ gas mixture with the highest hardness and lowest wear resistance. From experiment done it was found that the highest hardness in order of 232.02 VHN, while before being coated the hardness was 133.61 VHN, or there was an increase in hardness by factor of 1.73, while the wear resistance reduces from 11.6 x 10^-8 mm²/kg to 1.17 x 10^-8 mm²/kg or there was a reduce in wear resistance by factor of 9.9. The optimum conditions were achieved at Ar:N₂ ratio = 70:30. Based on XRD analysis, it can be concluded that the crystal structure of TiN thin film is cubic with the peaks (111), (200), (202), (311) and (222). From cross-section microstructure analysis using Scanning Microscope Electron (SEM), it was found the thickness of the thin film is 744 nm. The study showed that it was possible to deposited a titanium nitride (TiN) thin film on the surface of stainless steel 316L. The TiN thin film was successfully carried out to increase the hardness and to reduce the wear resistance. (author)