Effects of NiCr intermediate layer on microstructure and tribological property of laser cladding Cr3C2 reinforced Ni60A-Ag composite coating on copper alloy

Abstract In order to improve the wear resistance of Cu alloy as structural components, the Cr3C2 reinforcing Ni60A-Ag self-lubricating composite coating was successfully fabricated on Cu alloy through laser cladding technology. The formation and uneven distribution of coarse Cr7C3 columnar dendrites caused macro-cracks and severe phases segregation in the single layered composite coating. However, the preparation of NiCr intermediate layer effectively suppressed the formation of defects and precipitated homogeneous distribution of Cr7C3 and Ag fine dendrites. Ni3B and Ni31Si12 ceramic generated the preferential solidification along Cr7C3 dendrites boundary. The γ-Ni and Cr7C3 phases present an obvious texture index in the pole figures. The microhardness and plastic deformation resistance of composite coating significantly increased by 10 and 106 times relative to the substrate due to amount of Cr7C3 ceramic and dispersed distribution of Ni3B and Ni31Si12 refinement structure. The composite coating exhibited mean friction coefficient below 0.25 along with the elevated load and two orders of magnitude lower wear rates compared with substrate, which can attribute to the evenly distributed of Cr7C3 and Ag dendrites.