原位生成VC-VB-B4C复合颗粒增强镍基激光熔覆层

采用预涂粉末激光熔覆技术,在A3钢表面成功制备出原位生成VC-VB-B4C复合颗粒增强的镍基复合涂层.使用扫描电镜(SEM),EDS能谱和X射线衍射(XRD)对熔覆层的显微组织和物相构成进行了分析,并对熔覆层进行了硬度、摩擦性能测试.结果表明,原位生成VC-VB-B4C复合颗粒增强镍基复合涂层与基材呈冶金结合.熔覆层底部组织为定向生长的γ(Ni)树枝晶,熔覆层中、上部组织为大量先共晶析出的VC-VB-B4C颗粒相和Cr3C2条状相均匀分布于γ(Ni)基体中.熔覆层具有高的硬度(平均硬度HV0.31350)和良好的耐磨性,其磨损失重仅为纯Ni60熔覆层的1/3.熔覆层硬度和耐磨性的提高归因于大量VC-VB-B4C复合颗粒的形成及其在涂层中的均匀分布.

In Situ Synthesized VC-VB-B4C Complex Particulates Reinforced Ni-based Composite Coating by Laser Cladding

The VC-VB-B4C complex particulate reinforced Ni-based composite coating has been successfully synthesized in situ by prior pasting laser cladding on steel A3. The microstructural and metallographic analyses were carried out by a scanning electron microscopy, energy-dispersive spectroscopy(EDS) and X-ray diffractometer(XRD). The microhardness and wear resistance of the coatings were also tested. The results indicate that the composite coating is bonded metallurgically to the substrate. The microstructure in the bottom of coating consists mainly of oriented dendrites of γ(Ni). The microstructure locating in the center and upper zones contain a large number of VC-VB-B4C complex particles and acicular Cr3C2 phases distributed uniformly in the matrix of γ(Ni) solid solution. The VC-VB-B4C particulate reinforced composite coating gives a high average hardness of HV0.31350 and better wear resistance. The wear mass loss of the composite is just one third of that of the pure Ni60 coating. This could be attributed to the presence of the high content of in-situ synthesized VC-VB-B4C complex particulates and their well distribution in the composite coatings.