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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Cr_7C_3、Cr_(23)C_6、Ni_3Si、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 composite cladding layer of Ni-Co / WC-Graphite (G) was prepared by vacuum cladding technique. The microstructure and phase composition were analyzed by SEM and XRD. The bending behavior of the composite cladding layer was studied by three-point bending The fracture topography, micro-elemental analysis and fracture mechanism were analyzed. The results show that the Ni-Co / WC-G cladding layer consists of composite layer, transitional layer, diffusive metallurgical fusion zone and heat-affected diffusion zone. The composite layer presents three-dimensional textured structure with the main components of Cr7C3, (23) The solid solution of C_6, Ni_3Si, CrB, WC, C and γ-Ni-Co, the main microstructure of diffusion affected zone is pearlite, the main phase of diffusion metallurgical zone and transitional layer are Ni-Co-based solid solutions and intermetallic compounds; The three-point bending load-displacement curve of the composite cladding layer initially linearly changes, while the slope of the post-curve decreases gradually. When the load peak is reached, the Ni-Co / WC-G composite cladding layer cracks under compressive stress , While the fracture under tensile stress due to the transition layer, the diffusion of metallurgical zone and the existence of heat-affected diffusion zone, the load after the failure of the cladding layer is still within a certain range of slow increase, cladding layer fracture morphology was along the crystal Or transgranular, the heat-affected diffusion zone on the substrate side has fan-shaped cleavage fracture characteristics, and the matrix region away from the interface is a ductile fracture with a large number of dimples.