Study of laser clad Ni-base alloy/ZrO₂ (4Y) ceramic layer on the surface of 45 steel

In this paper the microstructure and hardness of laser clad Ni-base ZrO₂ (4Y) ceramic layer on the surface of 45 steel were examined by SEM, EDAX, XRD and microdurometer. A lamination phenomenon was observed in laser clad zone, in which there are two layers ZrO₂ ceramic surface layer followed by solidified Ni-base solid solution. The ceramic layer mainly consists of t-ZrO₂ and γ-Ni phases. The quick melting and solidifying caused by laser processing restrains t→m-ZrO₂ phase transformation. Under optimal laser parameters condition, a compact ZrO₂ ceramic layer can be obtained, and its microhardness attains HV0.21720. If the laser parameters deviate from the optimal value, pores and cracks will occur in the clad ceramic layer, and its hardness will drop to a great extent.