Synthesis and investigation of structural-mechanical-tribological properties of c-BN based BN thin films

Abstract

C-BN films are candidate material to diamond due to their promising properties. Although some properties of c-BN films are better than diamond, adhesion properties between the substrate and the film are very poor. In this study, c-BN films were deposited by closed-field unbalanced magnetron sputtering system onto 4140 steels in Ar/N2 atmosphere. The c-BN films coated in three different N2flow rates. The coated specimens were characterized by SEM and X-ray diffraction techniques. The bonding state of B, N and C elements were obtained using XPS. The mechanical properties of the c-BN films were tested by micro-indentation. The adhesion properties between substrate and the film were investigated by using scratch test. The tribological properties were carried out using pin-on-disc in atmospheric conditions. Our results showed that the c-BN films exhibited very dense and columnar microstructure. The maximum critical load was read 23 N in the softest c-BN film. The maximum and minimum hardness were measured 69 GPa and 33 GPa, respectively. When the hardness was increased the friction coefficient was decreased. The lowest friction coefficient (0.15) was obtained from the hardest film and the highest friction coefficient (0.65) was obtained from the lowest hardness