等离子堆焊镍包SiC_p增强钴基覆层的组织分析

Microstructure Analysis of Plasma Hardfacing Co-based Coating Reinforced by Nickel Coated Silicon Carbide

为了降低等离子堆焊过程中SiCp的烧损及改善SiCp的湿润性,采用改进的等离子喷焊枪在H13钢表面制备钴基镍包SiCp陶瓷增强复合堆焊层。用XRD对覆层的物相进行了鉴定;用OM和SEM分析了堆焊层组织;用显微硬度计测试了堆焊层的显微硬度。结果表明,堆焊层组织由结合区的胞状晶组织及涂层区的树枝晶以及一些颗粒相组成;堆焊层主要由Cr、Co等元素的硅化物和Cr的碳化物(Cr23C6、Cr7C3)及Co的固溶体组成,并在堆焊层顶层发现有少量的SiCp;显微硬度从表面向基体逐渐降低,呈梯度分布,堆焊层表面平均硬度(HV)可达800。

In order to decrease the burning loss of SiCpand improve the wettability of SiCpin PTA welding process,the Co-based overlaying coating reinforced by nickel coated silicon carbide particles on H13 steel surface was prepared with the modified plasma gun.Coating phases were identified by XRD.Microstructure of coating was obserbed by OM and SEM.Microhardness of coating was tested by microhardness tester.The results show that coating is composed of cellular crystals in bonding area,the dendrites in coating area and some particle phase.Hardfacing layer is mainly composed of the silicides of Cr and Co,Cr carbides such as Cr23C6 and M7C3,solid solution of Co,and a small amount of SiC at the top of hardfacing layer.Microhardness of coating is decreased gradually from the surface to the substrate,and exhibits the gradient distribution.The average microhardness of surface reaches 800 HV.