激光熔覆Co基合金/MoSi_2复合涂层显微组织分析

在304不锈钢表面预置Co基合金和MoSi2混合粉末,采用激光熔覆技术制备Co基合金/MoSi2复合涂层.利用光学显微镜、扫描电镜、电子探针和X衍射仪对熔覆层显微组织进行分析,并测试其显微硬度.结果表明熔覆层与基体呈良好的冶金结合.熔覆层中存在两种明显不同的凝固特征：一是MoSi2的添加量在0～20%之间,涂层组织主要由柱状树枝亚共晶和枝晶间共晶组成;二是MoSi2的添加量在30%～80%之间时,涂层组织主要是形貌各异的小平面树枝过共晶组成如竹叶状、星状、蝴蝶状、花瓣状等.其中Co基合金/40wt.%MoSi2复合涂层的平均显微硬度达到最大值1 455 HV0.2,是基体材料的4.9倍.

Microstucture Analysis of Co Based Alloy/MoSi2 Compound Coating by Laser Cladding

Using laser cladding technique, Co based alloy/MoSi2 compound coating was fabricated by preplacing Co based alloy and MoSi2 mixed-powders on the 304 stainless steel. By means of OM, SEM, EPMA and XRD, microstructure of the compound coating were investigated, and microhardness were measured. The experimental results show that an excellent bonding between the coating and the substrate can be ensured by the strong metal- lurgical interface. Two significantly different solidification characteristics were found in the microstructural evolu- tion in laser clads. One was characterized by the rodlike eutectic and equiaxed dendrite structure from 0 to 20 wt. % MoSi2. Another was characterized by various faceted dendrites in herringbone like, star shapes, butterfly, flower, and so on from 30 to 80 wt. % MoSi2. The microhardness of clad layer with Co based alloy ＋ 40 wt. % MoSi2 was the highest of 1455HV0.2. It was 4.9 times the substrateg.