采用激光熔覆方法在球墨铸铁表面制备30%TiC/钴基合金熔覆层,通过OM、SEM、EDS、XRD、TEM、MHV2000数显显微硬度计,分析了熔覆层的显微组织、成分、物相、熔覆层的硬度变化规律。结果表明,球墨铸铁基体与熔覆层能形成良好的冶金结合,熔覆层由表层的树枝晶和内部的胞状晶组成,从熔体中原位析出初晶TiC,且初晶TiC的量从熔覆层内部到表层逐渐增加,而未熔的TiC颗粒在晶间均匀分布,熔覆层主要由γ-Co、TiC、CoCx和少量的Cr7C3相组成,熔覆层的最高硬度是1278.8 HV0.2,提高到球墨铸铁基体的5倍以上。
Ductile cast iron, with excellent comprehensive mechanical properties, is widely used manufacturing traction wheel, crankshaft, cylinder liner, etc.. However, in the harsh environment, it often leads to failure due to the serious surface wear. At present, the repair methods for the damaged parts are mainly thermal spraying, deposit welding and other methods, but the properties and application effect of the repaired parts need to be improved. In order to significantly improve the surface properties of ductile cast iron, the 30%TiC/Co-based alloy cladding layer prepared by laser cladding is put forward on the surface of ductile cast iron in this work. The microstructure, composition, phase, hardness of the laser cladding layer are investigated and analyzed by OM, SEM, EDS, XRD, TEM and MHV2000 digital microhardness tester. The results show that the cladding layer can be integrated metallurgically with the nodular graphite cast iron matrix. The cladding layer consists of a surface layer of dendritic crystals and an internal cellular crystal. The primary phase of TiC from the melt is precipitated in situ during the solidification after laser heating. The amount of the primary TiC is gradually increased from the inner layer to the surface layer. Meanwhile, the undissolved TiC is dispersively distributed among the dendrites. The laser cladding layer is mainly composed of γ-Co, TiC, CoCx and a small amount of Cr7C3. The hardness maximum of the cladding layer is 1278.8 HV0.2, up to 5 times more than the hardness of the nodular graphite cast iron matrix.
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