Effects of CeO2, Si and Co on the microstructure and properties of Ni–Cu composite coating on 6061 aluminium alloy by laser cladding

Ni–Cu composite coatings have been fabricated on a 6061 aluminium alloy surface using a pulsed Nd-YAG laser. The basic coating was Ni–Cu powder with a Ni:Cu ratio of 4:1. The effects of adding to this powder 0.9 wt.% CeO2, 0.9 wt.% Si and 0.9 wt.% Co on the microstructure, microhardness and wear properties of the coatings have been investigated. The results show that, on adding the CeO2, Si or Co powders, the microstructure of the top region of the coating is mainly composed of equiaxed grains, dendritic crystals and fine equiaxed crystals, whereas the bottom region mainly consists of long rod-like, dendritic crystals and some particles. The average microhardness of the 99.1 wt.% Ni–Cu + 0.9 wt.% CeO2 coating is 529.05 HV, which was about four times higher than that of the bare 6061 aluminium alloy. In addition, the average friction coefficient decreased on adding CeO2, Si and Co powder to the Ni–Cu composite coating.