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 different structures and mechanical properties were
manufactured using different processing parameters. Energy dispersive X-ray
analysis was utilized to monitor the elemental composition during oxidation
tests at 800 ?C for up to 40min, which simulated the high temperature
conditions experienced by the coated cutting tools. The obtained results
demonstrated that the oxygen content increased significantly, reached ~68.8
at.%, while carbon and nitrogen contents decreased due to the formation of
gaseous by-products. X-ray diffraction confirmed complete transformation of
the TiN layer into rutile-TiO2 after 20min 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 20min 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.