Understanding the effect of Pt doping on the microstructure, mechanical and tribological properties of CrN coating

Abstract

This study investigated the effect of Pt doping on the microstructure, mechanical and tribological property of the CrN coating. Results showed that this CrN coating exhibited a loose columnar texture and a rough surface with a high Ra value of 3.07 ± 0.035 nm. A prominent coherent growth within the grain appeared in this coating, which provides strong bond strength of coating texture resulting in a high H/E ratio of 0.083. This CrN coating showed an unidirection scratch fracture, but also possessed good wear resistance with a smooth wear track. Pt doping induced a nearly single preferential growth of (200) plane, and resulted in a dense columnar texture and a smooth surface. The Ra value was 2.71 ± 0.285 nm for the CrN–Pt9.55 coating, and decreased to 1.04 ± 0.14 nm for the CrN–Pt17.73 coating. However, Pt atoms greatly blocked the coherent growth within the grain, and further degraded the bond strength of coating texture. The CrN–Pt9.55 coating showed serious multidirection scratch fracture, but also experienced severe wear accompanied with numerous cracks and adhesive debris. In contrast, the hindrance effect and mechanical degradation were further strengthened with the increase of Pt doping content. This CrN–Pt17.73 coating suffered from most severe fracture damage and debris adhesion during the scratch and sliding wear tests.