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用金相显微镜观察了WC系钢结硬质合金在三点弯曲载荷作用下的一断裂过程。试验结果表明,在外加载荷作用下,裂纹茵先在WC相粗大粒子和碳化物偏集区WC相粒子界面及碳化物偏集区的孔隙处萌生;随着应变量增大,已开裂WC相粒子中的解理裂纹张开粗化,与此同时较小的WC相粒子发生开裂;裂纹沿WC相与WC相粒子界面扩展,并穿过WC相粒子间的钢基体相薄层,然后裂纹沿WC相或二次碳化物粒子与钢基体相交界面扩展并撕裂钢基体相,最终导致试样完全断裂。作者根据对断裂过程的观察和断裂试样断口的分析结罘,讨论了WC系钢结硬质合金断裂的微观机制,并提出了提高材料抗脆性断裂能力和防止早期破裂的途径。
A fracture process of WC series steel-bonded cemented carbide under three-point bending load was observed with a metallographic microscope. The experimental results show that under the action of applied load, the crack initiation occurs at the interface between the WC phase coarse particles and the WC phase interface and in the carbides partial metamorphic zone. As the strain increases, the cracked WC phase The cleavage cracks in the particles are open and coarser, and at the same time smaller WC phase particles are cracked; the crack propagates along the WC phase and WC phase particles interface and passes through the thin layer of steel matrix between the WC phase particles and then cracks Extending and tearing of the steel matrix phase along the interface of the WC phase or secondary carbide particles with the steel matrix ultimately results in complete fracture of the specimen. Based on the observation of the fracture process and the fracture analysis of the fracture specimen, the author discussed the microscopic mechanism of the fracture of the WC-series cemented carbide and proposed ways to increase the fracture resistance of the material and prevent the early rupture.