冷作模具曲面激光熔覆修复工艺及路径研究

目的冷作模具在高压力和高冲击力作用下易磨损,传统的修复方式效率慢、自动化程度低,导致冷作模具报废率高,故采用激光熔覆技术对其进行修复,以获得具有优良使用性能的修复层。方法利用修复质量高、修复速度快的激光熔覆技术与空间自由度大、操作灵活的机器人技术相结合的方法获得熔覆层,基于组织观察、硬度分析和摩擦磨损实验观察检测熔覆层质量。结果熔覆最佳工艺参数为:功率1500 W,扫描速度2 mm/s,载气6 L/min,送粉器转速10 r/min,搭接率1/2。熔覆层硬度为350~430HV,远高于基体硬度。结论沿曲面短边方向由下往上做"之"字形扫描,熔覆效果最优。多道多层激光熔覆时,下一层的起点相对于上一层的起点偏移1.5 mm,得到的熔覆成形效果较好。微观组织分析表明,熔覆层与基体之间的界面冶金结合,熔覆层主要由致密的树枝晶组成。熔覆层的耐磨损性能明显优于基体。

Laser Cladding Repair Technology and Path of Cold-worked Dies

Cold-worked dies have a high rejection rate due to wear susceptibility at high pressure and high impact force, and inefficient and low-level automation of traditional repair methods. The work aims to obtain a repair layer exhibiting excellent service performance by repairing the dies by adopting laser cladding technology. A cladding layer was obtained by combining laser cladding technology which featured in high repair quality and rapid repair rate with robot technology which featured in high spatial freedom and flexible operation. Quality of the cladding layer was observed based on microstructure observation, hardness analysis as well as friction and wear test. Optimum process parameters were as follows: laser power of 1500 W, scanning speed of 2 mm/s, carrier gas of 6 L/min, powder feeder speed of 10 r/min, and overlapping ratio of 1/2. Hardness of the cladding layer was 350~430HV, which was well above that of the substrate. In single layer experiments, the best path is scanning zigzag along short edge of camber from the botttom up. In multi-pass multilayer cladding experiments, more effective method is to shift starting points of the second layer by 1.5 mm compared to that of the first layer. The microstructure analysis shows that interface between the cladding layer and the substrate exhibites metallurgical bonding, the cladding layer mainly consists of dense dendrite, and wear resistance of cladding layer is superior to that of the substrate.