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采用不含氮原料及微压氮化+真空脱氮烧结工艺制备脱β层梯度硬质合金,并采用扫描电镜及自带能谱仪、电子探针微区分析技术分析不同烧结阶段下硬质合金样品的微观组织结构及成分分布,研究烧结过程中微观组织结构演变规律,总结缺立方相层的形成机制,同时分析富Co层的形成机理。结果表明:在微压氮化阶段,硬质合金中的TiC相被氮化生成了Ti(C,N)相;在之后的脱氮烧结阶段,Ti(C,N)相溶解在液相中,并且发生氮钛的耦合扩散,导致缺立方相层的形成。Co元素的空位扩散及液相迁移机制联合作用形成了富Co层;冷却过程中液相迁移导致了富Co层内部不同区域之间Co含量的差异。
Β-layer gradient cemented carbide was prepared by nitrogen-free raw material and micro-pressure nitriding + vacuum denitrification sintering process. The microstructure of the hard layer was analyzed by scanning electron microscopy and energy dispersive spectrometer The microstructure and compositional distribution of the alloy samples were studied. The evolution of microstructure during sintering was investigated. The formation mechanism of the cubic phase was summarized. The formation mechanism of the Co-rich layer was also analyzed. The results show that the TiC phase in the cemented carbide is nitrided to form Ti (C, N) phase during the micro-pressure nitriding stage. In the subsequent denitrification and sintering phase, the Ti (C, N) phase dissolves in the liquid phase , And the coupling diffusion of the nitrides and nitrides occurs, resulting in the formation of an absent cubic phase layer. Co-vacancy diffusion and liquid-phase migration mechanism to form a Co-rich layer. The liquid-phase migration during cooling leads to the difference in Co content between different regions within the Co-rich layer.