不同粘结相WC基硬质合金微观结构与性能

Microstructure and mechanical properties of WC-based cemented carbides with different binder phases

以碳质量分数为理论含碳量的WC为硬质相,在1450℃下通过气压烧结制备WC-20Fe,WC-20Ni和WC-20Co硬质合金,通过X射线衍射、扫描电子显微镜、电子探针和力学性能测试研究了不同金属粘结相对烧结硬质合金微观结构和力学性能的影响。结果表明:WC-20Fe合金出现η脱碳相(Fe_(3)W_(3)C),W在粘结相Fe中的溶解度仅有1.915%(质量分数),WC晶粒尺寸最小。WC-20Ni合金渗碳出现石墨相(C),W在粘结相Ni中的溶解度达到10.753%(质量分数),WC晶粒尺寸最大,合金硬度最小。WC-20Co合金为正常两相区组织(WC+γ),具有最高抗弯强度2720 MPa和最大硬度934.41 kg∙mm^(-2)。所有合金断裂模式均为脆性断裂和沿晶断裂,WC-20Co合金断口出现明显的粘结相撕裂。

The WC-20Fe,WC-20Ni,and WC-20Co cemented carbides were prepared by gas pressure sintering at 1450℃using the WC powders with the theoretical carbon content(mass fraction).The effects of metal binders on the microstructure and mechanical properties of the cemented carbides were investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM),electron probe microanalysis(EPMA),and mechanical properties tester.The results show that,the brittle η-phase(Fe_(3)W_(3)C)appears in the WC-20Fe alloys,and finer grains are observed due to the lower solubility of W(1.915%by mass)in Fe binder.However,the graphite phase(C)is detected in the WC-20Co alloys,the solubility of W in Ni binder can reach to 10.753% by mass,resulting in the largest grain size and the lowest hardness.The WC-20Co alloys show the two-phase region(WC+γ),which exhibit the highest bending strength and hardness of 2720 MPa and 934.41 kg∙mm^(-2),respectively.The fracture mode of all the alloys can be described as the brittle fracture and intergranular fracture.Moreover,the fracture surface of the WC-20Co alloys shows the obvious binder tearing character.