A novel approach to investigate oxidation behaviour and mechanical properties of CVD bilayer TiN/TiC coatings

A novel approach to investigate the oxidation behaviour of bilayer TiN / TiC coatings deposited on WC-Co substrate by CVD method was employed. Two coatings with di f f erent structures and mechanical properties were manufactured using di f f erent processing parameters. Energy dispersive X-ray analysis was utilized to monitor the elemental composition during oxidation tests at 800 degrees C for up to 40 min, which simulated the hightemperature conditions experienced by the coated cutting tools. The obtained results demonstrated that the oxygen content increased significantly, reached similar to 68.8 at.%, while carbon and nitrogen contents decreased due to the formation of gaseous by-products. X-ray di f f raction confirmed complete transformation of the TiN layer into rutile-TiO 2 after 20 min of oxidation. The microhardness of the coated samples significantly decreased due to the oxide formation and development of pores and cracks during the oxidation process. Tribological tests revealed a significant increase in the volume loss during dry sliding against zirconia counterpart after 20 min of oxidation time. Moreover, surface colour of the oxidized coated samples changed from silver-white to grey-black with oxidation progression, enabling visual evaluation of oxidation damage.