中文摘要：

采用激光熔覆方法在NAK80模具钢表面制备钴基合金熔覆层，用扫描电镜、X射线衍射仪分析了熔覆层的显微组织，通过干滑动摩擦试验研究了熔覆层的摩擦磨损性能，分析了其磨损机制，并用三维表面形貌仪观察磨损试样的表面形貌。结果表明：熔覆层的主要组成相为Cr28C6、Co3Mo2Si、MoC、FeCr和γ-Co；熔覆层由涂层与基体界面处的平面晶区、涂层中部的胞状树枝晶区和表层的网状等轴晶粒区组成；经激光熔覆处理后的NAK80模具钢表面硬度和耐磨性得到了显著改善，与NAK80模具钢相比，熔覆层表面的平均摩擦因数降低了约349／5，比磨损率下降了约91．30A；熔覆层的磨损机制为粘着磨损和轻微的显微切削。

英文摘要：

The Co-based alloy cladding coating was successfully fabricated on the surface of NAK80 mold steel by laser cladding technology. The microstructure of the coating was analyzed by scanning electron microscopy （SEM）, X-ray diffraction （XRD）. The property of friction and wear, and the wear mechanism were studied by the dry sliding friction test. The morphology of wear samples were measured by 3D surface profilometer. The results show that the cladding coating was mainly composed of Cr28C6, Co3 Mo2 Si, MoC, FeCr andγ-Co. The plane crystal in the interface of the coating and the substrate, cellular dendrite at the central zone and reticular equiaxed crystal near top surface were observed in the cladding coating. The microhardness and wear resistance of NAK80 mold steel surface were improved noticeably by laser cladding technology. Compared with NAK80 mold steel, the average friction coefficient of the cladding coating decreased by about 34%, and the wear rate reduced by about 91.3%. The wear mechanism for the laser cladding coating was adhesive wear and slight micro-cutting.