Surface Structural Characterization of TiSiN and TiSiCN Coatings Produced by Cathodic Arc Physical Vapor Deposition

Cathodic arc physical vapour deposition is considered the industrial process for production of nitride coatings, but it suffers from micro-sized particles due to inherent characteristics of electric arc. Macro-particles exert undesirable effects on surface roughness, tribological properties, corrosion and oxidation resistance and, therefore, must be controlled. In the present study, these particles have been characterized and evaluated in three-component, TiSiN, and four-component, TiSiCN, coatings deposited on steel substrate in an industrial process. Energy dispersive spectrometry and X-ray diffraction indicated that chemical composition of the coatings were in the nominal ranges and TiSiN and TiSiCN had composite structures based on TiN and Ti(C, N) crystal lattices, respectively. According to the size and distribution of micro-particles, their roughness and morphology by field emission scanning electron microscopy, together with Image analysis, the particles were classified into three groups; most of them were spherical with an average diameter of 1 micron. EDS and X-ray mapping on the surface of coatings were carried out to assess the chemical composition and origin of the particles. The results revealed that increasing silicon content of the particles, as compared to the coating matrix, was associated with the formation of the particles from cast Ti-20Si target due to separation of Si in the microstructure and the lower melting temperature of silicon compared to titanium. The dominant cause in the formation of macro-particles is the heterogeneity of the target material together with the arc mobility; TiSiCN coating, with higher vapour pressure during deposition, experienced more particles and a higher roughness than TiSiN coating.