Influence of C2H2/N2 flow ratio on the microstructure, mechanical properties, and electrochemical behavior of TiCN composite coatings

The microstructure, mechanical properties, and electrochemical performances of TiCN composite coatings were investigated. Via the modification of the C2H2/N2 flow ratio, TiCN coatings with various C contents were synthesized by combining a cathodic arc and glow discharge technology. With a C2H2/N2 flow ratio of 1:8, TiCN coating mainly consisted of the TiC phase. As the C2H2/N2 flow ratio exceeded 1:4, the crystallinity of TiCN coatings deteriorated. The coexistence of the amorphous and crystalline phases was detected in TiCN coatings with a C2H2/N2 flow ratio of 3:8. The introduction of the C element into TiCN coatings could disturb the growth orientation and induce dislocation motion, leading to an enhancive toughness and a decrease in hardness and elastic modulus. Moreover, the precipitation of amorphous C or CNx was beneficial to the corrosion resistance of TiCN coatings. This finding indicates the potential application of TiCN composite coating in corrosive environments. •A high C2H2/N2 flow ratio favors the formation of amorphous structures in TiCN coating, and the N atoms preferred to combine with C atoms rather than Ti atoms.•The formation of amorphous structures with a high C2H2/N2 flow ratio weakens the hardness of TiCN coating, but the toughness is strengthed.•The inert amorphous structures could endow the TiCN coating with low porosity, and enhance the corrosion resistance.