The effect of substrate temperature of titanium aluminium nitride coating on titanium alloy (TI-6AL-4V) substrate using PVD method

Abstract

Titanium and its alloys are widely employed in many industrial fields, due to their high specific strength and good corrosion resistance. On the other hand, these materials show relatively low shear strength and high coefficient of friction. As matter of fact, the poor wear resistance of these materials is still a limit to a wider use. However, these disadvantages mainly concern on bulk materials and can be avoided by using intermetallic coatings. Thin hard coatings have good wear resistance only when they have both good cohesion and adhesion. In this study, the effect of substrate temperature of titanium aluminium nitride (TiAlN) coating on the titanium alloy substrate using PVD method was evaluated. The TiAlN coating was deposited on Ti-6Al-4V substrate by DC magnetron sputtering process at various temperature. The reactive sputter gas with a mixture of Ar (99.999%) and N2 (99.999%) with flow rate of 20sccm and 10 sccm respectively was used. The substrate temperature was set at 200 °C, 240 °C and 300 °C, and the bias was kept at -60V for all the coatings. Structural characterization of the coating was done using X-ray diffraction (XRD). The XRD measurements showed the presence of Ti2AlN and also, the results show that its intensity was decreased with substrate temperature, however there was no changes in crystalline structure was occurred. The substrate temperature during the growth, change in crystalline structure will not occur. The surface roughness of the coating was determined using an Atomic Force Microscope (AFM). From three-dimensional AFM analysis it was indicated that the surface roughness will decrease as the substrate temperature increases. And also, Cross-sectional FESEM indicated the presence of dense columnar structure. The mechanical properties of the coating layers (cohesion and adhesion) were deduce by both Rockwell-c adhesion test and knife test. These two tests indicated that by increasing substrate temperature, the adhesion and cohesion were also increased.