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- 2017
Ni-Co/WC-Graphite复合熔覆层的组织与三点弯曲行为
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Abstract:
采用真空熔覆技术制备了Ni-Co/WC-Graphite（G）复合熔覆层，采用SEM、XRD等分析了微观组织及相组成，利用三点弯曲研究了复合熔覆层的弯曲行为，并分析了断口形貌特征、微区元素分析与断裂机制。结果表明：整个Ni-Co/WC-G熔覆层包括复合层区、过渡层区、扩散冶金熔合带以及热影响扩散区，复合层区呈现三维织构组织特征，主要组成相有Cr7C3、Cr23C6、Ni3Si、CrB、WC、C和γ-Ni-Co固溶体，扩散影响区主要组织为珠光体，扩散冶金熔合带及过渡层主要组成相为镍钴基合金固溶体及金属间化合物；具有复合熔覆层试样的三点弯曲载荷-位移曲线初始呈线性变化，而后曲线斜率逐渐减小，在达到载荷峰值时Ni-Co/WC-G复合熔覆层在承受压应力时溃裂，而在承受拉应力时断裂，由于过渡层、扩散冶金带以及热影响扩散区的存在，使载荷在熔覆层失效后仍在一定范围内缓慢增加，熔覆层区断口形貌呈沿晶或穿晶特征，基体侧的热影响扩散区呈扇形解理断裂特征，远离界面的基体区域为具有大量韧窝的韧性断裂。 The Ni-Co/WC-Graphite composite coating was fabricated by vacuum cladding. The microstructure and composition of the composite coating were characterized and analyzed by SEM and XRD. The bending behavior was studied through three point bending test, and the fracture characteristics, elements analysis and fracture mechanism were discussed. The results show that the whole composite coating consists of composite area, transition area, diffusion-fusion strip and heat-affected area. The WC particles well-distribute among the composite coating and form a 3D reticular microstructure characteristic. The main phases are Cr7C3, Cr23C6, Ni3Si, CrB, WC, C and γ-Ni-Co solid solution in the composite coating. The pearlite is the main phase at heat-affected area. There are γ-Ni-Co solid solution and intermetallics in fusion area and transition area. Three point bending test show that the load-distance curve presents linear change at the initial state, and then the slope of curve decreased. The composite coating debacle happens as the load reaches a maximum when the composite coating bears compress stress, and fracture happens as the load reaches a maximum when the composite coating bears tensile stress. The load increases slowly after the composite coating failure because of the forming of the transition area, diffusion-fusion strip and heat-affected area. The fracture characteristics present intergranular or transgranular at composite coating area. The fracture presents fan cleavage characteristics at the heat-affected area, and there are many dimples at substrate area. 国家自然科学基金（51205178）；甘肃省自然科学基金（14RJYA308）
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