Microstructure and properties evolution of Co06/Ni60A duplex coating on copper by plasma cladding

Abstract

Co06/Ni60A duplex coating was fabricated on copper substrate by plasma cladding. To clarify the evolution of microstructure and wear resistance of the coating during high-temperature, the coating samples were heat-treated at 500 °C for up to 500 h in air. After heat treatment, the phases in the coating such as Cr 7 C 3 , Cr 23 C 6 and the crystal grains of the γ-Co solid solution had a tendency to grow up, and remained basically stable after 100 h. No martensite transformation (γ-Co → ε-Co) was observed. The mass fraction of Cr 23 C 6 reinforcement phase had an increasing trend, which was attributed to the conversion of Cr 7 C 3 and the precipitation of γ-Co solid solution. The diffusion degree of elements at the Co-Ni interface and Ni-Cu interface also showed a trend of stabilizing. Due to the coarsening of microstructure, the diffusion of copper and the reduction of Cr 7 C 3 , the wear resistance of the coating changed from 6.2 times to 2.9 times that of the copper substrate. The wear mechanism transformed from abrasive wear to abrasive wear + adhesive wear. Results showed that the properties of the coating have a certain decline in the initial stage, but it tended to be stable after long-time service. • Co06/Ni60A duplex coating was prepared for high temperature applications. • The microstructure evolution of the coating in high-temperature air was analyzed layer by layer. • Microstructure coarsening, copper diffusion and Cr 7 C 3 reduction reduced the wear resistance of the coating. • The gradual stabilization of the properties after long-term heat treatment indicated the usability of the coating.