TiC coatings were cladded on the surface of45 steel by a CO2 constant current laser using Ni60+TiC gradient layer structure.The effect of process parameters(laser power,scanning rate and overlap rate)on the microstructure and properties of TiC coatings was investigated.The results show that the surface cracks of the coating decrease and then increase with the increase of laser power and scanning rate.The surface cracks disappear when the laser power is 4.0 kW and the scanning rate is 400 mm/min.With the increase of the overlap rate,the surface cracks of the coating increase and then decrease,and the surface cracks of the coating disappear when the overlap rate is 50％.The optimal process parameters are laser power 4.0 kW,scanning rate 400 mm/min,and overlap rate 50％.The thickness of TiC gradient coating is about 1.2 mm after the best process,and it is metallurgic ally bonded with the base layer.The microstructure of the most superficial layer is dendritic TiC and a small amount of Ni-based solid solution,the microstructure of the gradient layer is TiC+Ni-based solid solution,TiC content from the surface to the inside is in a gradient decrease,Ni-based solid solution content from the surface to the inside is in a gradient increase.The hardness of TiC coating decreases from 1968 HV0.2 to 240 HV0.2.In addition,the wear rate of the TiC coating is 1.757 × 10-15m3/(N·m).
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