烧结温度对钴基耐磨合金微观组织和性能的影响

在真空环境下采用粉末冶金法制备碳化物增强钴基耐磨合金,利用扫描电子显微镜(scanning electron microscope,SEM)、电子探针显微分析仪(electron probe microanalyzer,EPMA)、X射线衍射仪(X-ray diffractometer,XRD)等设备观察和分析烧结温度对合金微观组织的影响,研究了增强相的物相及其形成机制。研究结果表明:粉末冶金法制备的钴基耐磨合金基体由面心立方(face center cubic,FCC)结构的γ-Co和密排六方(hexagonal closed-packed,HCP)结构的ε-Co相组成,增强相为M6C和M_(23)C_6型碳化物。当固相烧结温度为1250℃时,块状M6C型碳化物和颗粒状M_(23)C_6型碳化物弥散分布于基体中;当烧结温度升高至1340℃,M6C型碳化物呈尖锐的棱角状,平均尺寸大于30μm,颗粒状M_(23)C_6消失;烧结温度继续升高至1360℃,M6C型碳化物呈骨架状,ε-Co相消失。对合金的力学性能测试结果表明,当烧结温度为1270℃时,钴基合金的综合性能最佳,硬度大于HRC 60,抗压强度为1921 MPa,抗拉强度为203 MPa,摩擦系数为0.561。

Effect of sintering temperature on microstructures and mechanical properties of Co-based wear-resistant alloy

The carbide-reinforced Co-based alloy was prepared by powder metallurgy technology in this paper. The effects of sintering temperature on the microstructures and mechanical properties of the prepared alloy were investigated by scanning electron microscope (SEM), electron probe microanalyzer (EPMA), and X-ray diffractometer (XRD), and the formation mechanism of reinforced phase was discussed. The results show that, the matrix of carbide-reinforced Co-based alloy prepared by powder metallurgy technology is composed ofγ-Co in face center cubic (FCC) structure andε-Co in hexagonal closed-packed (HCP) structure. The reinforced phases include M6C carbide and M23C6carbide. When the sintering temperature is 1250℃, the blocky M6C carbide and the granular M23C6 carbide are dispersed homogeneously in the matrix. When the sintering temperature increases to 1340℃, the M6C carbide grows into sharp-edge like shape with the average size more than 30μm, meanwhile, the M23C6 carbide is disappeared. When the temperature reaches to 1360℃, the M6C carbide develops into skeleton form, meanwhile, theε-Co phase disappears. The mechanical property test shows that, when the sintering temperature is 1270℃, the prepared Co-based alloy achieves the optimal property with the hardness over 60HRC, the compressive strength of 1921 Mpa, the tensile strength of 203 Mpa, and the friction coefficient of 0.561.