铜表面激光熔覆NiCrWB合金的组织结构与耐磨性能研究

采用高能量密度激光重熔NiCrWB喷涂涂层的方式制备熔覆层,用XRD分析熔覆层和喷涂层的物相组成,用扫描电镜和金相显微镜分析涂层和熔覆层组织形貌以及磨损表面形貌.研究了涂层组织形貌、物相组成对涂层耐磨性能的影响,分析了喷涂层和熔覆层的磨损机理.结果表明:对于NiCrWB材料来说,组织结构对耐磨性能的影响要大于硬度对耐磨性能的影响.显微硬度较低的熔覆层由于组织致密均匀,其耐磨性能明显优于组织缺陷较多的喷涂层.通过扫描电镜观察发现,喷涂层的磨损表面出现较多的疲劳裂纹、凹坑、磨粒和较深的磨痕,推断喷涂层颗粒脱落是由于在周期载荷作用下,裂纹在表层和亚表层扩展后连接,使得裂纹包围区域颗粒脱落.而熔覆层中的裂纹是由于磨损表面发生塑性变形而形成的.

Microstructure and Wear Resistance of Laser Cladding NiCrWB Alloy Coating on Cu Substrate

NiCrWB cladding layer was prepared by high energy density laser-remelting of NiCrWB spraying layer from high velocity air fuel spray (HVAFS). The phase compositions, structures and patterns of the two layers were investigated by x-ray diffraction (XRD), scanning electron microscopy (SEM) and optical microscopy (OM). The worn surface morphologies of the two layers were examined by SEM and OM, and the sliding wear mechanism of the cladding layer and the spraying layer were suggested. In addition, the effects of the phase structure and pattern of the layers on the wear-resistance were investigated. The result showed that the structure was the main factor affecting the wear-resistance of the layers. The cladding layer had a lower microhardness than that of the spraying layer, while the wear-resistance of the cladding layer was better than that of the spaying layer because of the dense and uniform structure and few of defects. Many fatigue cracks, ruts, abrasive particles and deep grinding cracks were found on the worn surfaces of the spraying layer It is deduced that cracks originated from surface layer and subsurface layer coalesced under the cyclic load and resulted in detachment of wear particles. However, the cracks in the cladding layer were generated by the plastic deformation of the abrasive surfaces.