Comparative studies on microstructure and mechanical properties of CrN, Cr–C–N and Cr–Mo–N coatings

Two different CrN-based ternary coatings were synthesized by hybrid coating system of arc ion plating (AIP) and DC magnetron sputtering technique. In this work, the effects of C addition for anion solid solution (Cr–C–N) and Mo addition for cation solid solution (Cr–Mo–N) on microstructures and mechanical properties of CrN coating were investigated. The microhardness values of Cr–C–N and Cr–Mo–N coatings were largely depended on C and Mo contents, respectively. The maximum hardness values of Cr–C–N and Cr–Mo–N coatings were 23 and 34 GPa, respectively. These values were much enhanced ones compared with 18 GPa of CrN coating. The enhanced hardness values of Cr–C–N and Cr–Mo–N coatings were explained with the solid solution hardening as well as defect hardening. The residual stresses in both coatings were compressive and less than 5 GPa. The average friction coefficient of Cr–C–N and Cr–Mo–N coatings was measured 0.5 and 0.4, respectively. The decreased friction coefficients of Cr–C–N and Cr–Mo–N coatings was explained by the formation of carbon rich transfer layer (or amorphous carbon layer) and the formation of MoO3 layer known as self-lubricant materials.