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. (c) 2007 Elsevier B.V. All rights reserved.