Effect of MoSi2 on the microstructure and wear resistance of NiCrBSi coating with CuNi interlayer on aluminum alloy

In this study, the MoSi 2 reinforced NiCrBSi coatings were prepared on the aluminum alloy by laser cladding. A Cu-based interlayer was employed to refrain undesirable intermetallic compounds caused by the diffusion of Al element at the interface between composite coating and substrate, and to improve the metallurgical quality of the composite coating. The effects of different content of MoSi 2 (0, 10 and 20 wt%) on the microstructure evolution and wear resistance of the NiCrBSi coatings were investigated. Experimental results show that the CuNi transition layer is composed of (Cu, Ni) solid solution, without obvious cracks or pores and exhibits excellent metallurgical bonded to the substrates. The phases present in the NiCrBSi coating without MoSi 2 addition comprises γ-Ni solid solution, Ni 3 Fe, Ni 3 Si, Ni 3 B and Cr 23 C 6 . MoSi 2 reinforced NiCrBSi coatings mainly include γ-Ni solid solution, Ni 3 Fe, Ni 31 Si 12 , CrB, Mo 2 C and SiC. With the MoSi 2 content increasing to 20 wt%, the content of Ni 31 Si 12 , CrB and carbides in the coating has significantly increased, which enhanced the microhardness and mechanical properties of the NiCrBSi coating. All three coatings exhibited lower mean friction coefficients and wear rates than aluminum alloy substrate, the composite coating with 20 wt% MoSi 2 had lowest mean friction coefficient and wear rate. The excellent wear resistance can be attributed to the synergistic effect of CrB and carbides hard reinforcing phases as well as the Ni 31 Si 12 tough phase.