Comparison of structural and chemical properties of Cr-based hard coatings

A series of chromium nitride, carbide and carbonitride coatings were prepared by ion plating using nitrogen and acetylene as reactive gases. The depositions were made at different partial pressures of the reactive gases while maintaining other parameters constant. The crystal structure and microstructure were studied by TEM. The CrN and Cr2N phases were detected in the chromium nitride coatings. In the carbide coatings, orthorhombic Cr7C3 and the metastable cubic CrC phase were confirmed. For oxidation studies, the samples were annealed at 750 °C. Afterwards, the depth profile was measured by glow discharge optical emission spectrometry (GDOES). A complex diffusion was observed involving outdiffusion of nitrogen and segregation of carbon at the substrate-coating interface.