激光熔覆复合涂层WC对裂纹产生机理影响研究

为了研究复合涂层中碳化钨(WC)组织演变对裂纹产生的影响机理, 采用单层激光熔覆、过渡层梯度熔覆与双层熔覆制备3种Ni50A/WC复合涂层对比的方法, 分析涂层的形貌与组织、裂纹产生特点以及原因, 探究WC的组织演变对裂纹产生的影响。结果表明, 不同熔覆方法的WC组织演变对裂纹产生的影响主要由残余WC颗粒内部开裂形成裂纹源、硬质相元素引起成分偏析等作用组成; 双层熔覆、梯度熔覆涂层与单层熔覆涂层相比, 由于粉末吸收了更多的能量, 残余WC颗粒含量降低了32.7%与37.9%, 减少了涂层内部裂纹源; 共晶化合物的W元素质量分数也从单层熔覆涂层的0.534分别下降到双层熔覆涂层的0.417与梯度熔覆涂层的0.386, 降低了硬质相元素集中程度, 减少了涂层成分偏析, 降低了涂层开裂敏感性。该研究对改善激光熔覆复合涂层的开裂问题、提高复合涂层的成品率有一定的指导意义。

Study on the effect of laser cladding composite coating and its WC on crack formation mechanism

In order to study the influence mechanism of WC microstructure evolution on crack generation in composite coating, three Ni50A/WC composite coatings were prepared by single-layer laser cladding, transition layer gradient cladding and double-layer cladding. The morphology and structure of coating, crack generation characteristics, and the causes of crack were analyzed. The influence of WC microstructure evolution on crack generation was then explored. The results show that the influence of microstructure evolution of WC by different cladding methods on crack generation is mainly caused by internal cracking of residual WC particles. Compared with the monolayer cladding coating, the content of residual WC particles decreased by 32.7% and 37.9% due to the absorption of more energy by the powder of double-layer cladding and gradient cladding coating, and the source of cracks in the coating was reduced. In addition, the mass fraction of W element in eutectic compounds decrease from 0.534 of monolayer cladding coating to 0.417 of double cladding coating and 0.386 of gradient cladding coating, which reduced the concentration of hard phase elements, composition segregation and cracking sensitivity of coating. This research has certain guiding significance to improve the cracking of laser cladding composite coating and improve the yield of composite coating.