Microstructure formation and surface strengthening of simultaneous Al–Ni deposition on copper by pack cementation

Abstract

Aluminum and Nickel elements simultaneously deposited on the surface of copper by pack cementation was investigated. SEM examinations reveal that the coating consists of three layers. The outermost layer (adhesion layer) consists of Al2O3, Cu9Al4 and AlNi3 intermetallic compounds and Ni-based solid solution. The intermediate layer (diffusion layer) is composed of the Cu9Al4, AlNi, AlNi3 intermetallic compounds and Cu-based solid solution. The micrographs of diffusion layer show that it can be divided into striped and blocky areas. The innermost layer (solid solution layer) is Cu-based solid solution. Possible mechanism of Al and Ni co-penetration on Cu was also deduced. The hardness of coating is greatly higher (7 times in adhesion layer and 5 times in diffusion layer) than that of copper. The thermal conductivity of coating was 132.534–142.527 W m−1 K−1 in the temperature range of 300 °C–500 °C.