Abstract: In order to evaluate the effect of laser power on microstructure and mechanical properties of the Ni/316L layer deposited via high-speed laser cladding, the Ni/316L layer was clad on the Q235 steel surface under laser power of 1.1, 1.3, and 1.5 kW respectively. The microstructure, Vickers hardness, impact property and elastic modulus of the laser clad layers were examined by means of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), Vickers hardness tester, impact testing machine and Knoop indentation method. The results show that when the laser power is 1.1 kW, the grain growth in the laser clad layer contains perpendicular-to-interface growth mode and slant growth mode, the clad layer also has a small amount of pores and other defects, and the elements at the clad layer/substrate interface are distributed in a cliff-like manner, which means that the element diffusion between the substrate and the clad layer is limited. As the laser power increases, the perpendicular-to-interface growth mode of grains becomes the main mode, and the porosity of the clad layer is lower and the defect is less, the interdiffusion degree of elements at the clad layer/substrate interface is improved. The laser power has a significant effect on hardness and impact property of the clad layer, but has little effect on elastic modulus. The maximum hardness of the clad layer with different laser power is always about 100 μm away from the interface. When the laser power increases from 1.1 kW to 1.5 kW, the maximum hardness of the clad layer fusion zone is increased by about 50%, and the impact property of the clad layer specimen is about 20% higher than that of the substrate when the laser power is 1.5 kW.

Key words: high-speed laser cladding, laser power, microstructure, mechanical properties