摘要
利用Ni60+TiC梯度层结构,通过CO2恒流激光器在45钢表面制备了 TiC涂层,研究了工艺参数(激光功率、搭接率和扫描速率)对TiC涂层组织和性能的影响.结果表明,随着激光功率和扫描速率的增加,涂层表面裂纹先减后增,当激光功率为4.0kW,扫描速率为400 mm/min时,涂层表面裂纹消失;随着搭接率的增加,涂层表面裂纹先增后减,搭接率至50％时,涂层表面裂纹消失.最佳工艺参数为:激光功率4.0 kW、扫描速率400 mm/min、搭接率50％,其处理后的TiC梯度涂层厚度约为1.2 mm,与基体层呈冶金结合,最表层组织为树枝状TiC及少量Ni基固溶体,梯度层组织为TiC+Ni基固溶体,TiC含量由表及里呈梯度减少,Ni基固溶体含量由表及里呈梯度增加;TiC涂层的显微硬度由表及里从1968 HV0.2梯度下降至240 HV0.2;TiC涂层的磨损率为1.757 × 10-15 m3/(N·m).
Abstract
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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