The adhesion and tribological properties of c-BN films deposited by high power impulse magnetron sputtering

Abstract

Nitride based films are very important for industrial applications due to their mechanical and tribological properties. Among the nitride based films, c-BN films have superior properties. But, the adhesion properties of c-BN films deposited using magnetron sputtering with different power sources are inadequate generally. Recently, High Power Impulse Magnetron Sputtering (HiPIMS) power sources have been used to increase the adhesion of coatings and there is no open literature about c-BN deposited using HiPIMS. From this point, c-BN films were coated on 4140 steels using HiPIMS with closed-field unbalanced magnetron sputtering (CFUBMS). In the process, two B4C, two Ti targets and Ar + N-2 gas mixture were used to synthesize c-BN films. The amount of N-2 was altered as 2.5, 3.5 and 4.5sccm. The characteristic properties of c-BN films were analyzed using SEM, XRD and FT-IR. The mechanical properties were tested using a microhardness and scratch testers. The tribological properties were performed by a pin-on-disc tribotester under atmosphere, argon, and oil test conditions. The results showed that the properties of c-BN films deposited by HiPIMS are interesting. The hardness values were obtained above 36 GPa and the maximum critical load was reached to 80 N. Also, the minimum CoFs were observed as expected from the oil condition, in that case, the lowest CoF (mu congruent to 0.06) was noted from the hardest coating.