为了克服纯铜表面激光熔覆时热量难以积聚的困难, 得到冶金结合良好的Ni60熔覆层, 采用预热辅助脉冲激光熔覆的方法, 在纯铜表面进行了Ni60合金粉末的熔覆实验, 并建立了纯铜表面预热辅助脉冲激光熔覆过程的3维瞬态热弹塑性模型, 对温度场及残余应力进行了仿真。预热温度达到573K时, Ni60熔覆层中裂痕完全消除;预热温度为673K时, 激光熔覆的加工效率提升了2.2倍;预热辅助脉冲激光熔覆得到的Ni60熔覆层平均硬度达到800HV0.2; 常温下, Ni60熔覆层与ASTM52100钢相对耐磨性为4.45, 摩擦系数约是铜和ASTM 52100钢的57%。结果表明, 随着预热温度的升高, Ni60熔覆层中裂纹减少, 激光熔覆效率提高; Ni60熔覆层有效地提高了表面硬度, 减小了摩擦系数。通过预热辅助脉冲激光熔覆技术, 在纯铜表面制备得到无裂纹、无气孔的Ni60熔覆层, 可有效地提高铜基材的硬度与耐磨性。

In laser cladding, it was difficult to accumulate heat on the pure copper surface for forming effective metallurgical bonding between copper and Ni60 coatings. In order to overcome the difficulties, a method of pulsed laser cladding assisted with preheating was adopted. Laser cladding experiments on copper substrate were conducted, and a 3-D transient thermo-elastic-plastic model was developed to simulate the thermal process and residual stress. When the preheating temperature reached 573K, the cracks in Ni60 cladding layer were completely eliminated. The processing efficiency of laser cladding was increased 2.2 times when preheating temperature was 673K. The average hardness of the Ni60 coating obtained by laser cladding assisted with preheating was 800HV0.2. Under normal temperature, the relative wear resistance of Ni60 coating and ASTM52100 steel was 4.45. Friction coefficient of Ni60 coating was 57% of ASTM52100 steel or copper. The results show that with the increase of the preheated temperature, the number of cracks in Ni60 coating decreases and processing efficiency of laser cladding increases. Also, the surface hardness of Ni60 coatings improves and friction coefficient decreases effectively. By pulse laser cladding assisted with preheating, Ni60 cladding layer on pure copper without cracks and air holes is obtained.