Thin film deposition of tungsten nitride on SS 316 L surface using DC-Sputtering technique

Abstract

Abstract 316L stainless steel (SS) is an alloy steel that is not easily corroded, so it is widely used for biomaterial applications. In addition to being resistant to corrosion, 316L SS is also inexpensive when compared to other medical metals. However, 316L SS has relatively low hardness and wear resistance, thus this weakness must be improved. By heat treatment, it is impossible to improve the SS alloy, so other techniques must be applied. In this study, improvement of surface hardness of 316L SS by coating tungsten nitride (WN) using DC-sputtering method has been conducted. The sputtering process was implemented by varying the sputtering pressure of 1.8×10-2, 2.3×10-2 and 2.8×10-2 Torr. Furthermore, the composition ratio of Ar and N2 gases were varied i.e 70:30, 80:20 and 90:10 with a voltage of 4 kV and deposition time of 120 minutes. After the coating process, hardness testing was carried out using the Vickers hardness test with a load of 25 gf. The formation of tungsten nitride was also analyzed using XRD. The highest hardness in order of 938.64 VHN is achieved at a pressure of 2.8×10−2 Torr and the ratio of Ar:N2 gas was 90:10. From the XRD analysis, the layer formed is a W+WN layer which is shown at the peaks at a scattering angle of 2Ɵ is 43.55º; 2Ɵ is 39,530º; 2Ɵ is 56,880º; and 2Ɵ is 71,550º.