激光熔化沉积Co／Co3Mo2Si三元金属硅化物耐磨合金显微组织

Microstructure of Laser-Melted Co/Co3Mo2Si Wear Resistant Ternary Metal Silicide Alloys

摘要:

为改善三元金属硅化物Co3Mo2Si耐磨合金的室温韧性，利用激光熔化沉积方法制备了钻基固溶体增韧的Co3Mo2Si三元金属硅化物合金。结果表明：其显微组织由Co3Mo2Si初生树枝晶和枝晶间少量Co／Co3Mo2Si共晶组成；Co／Co3Mo2Si金属硅化物合盒的硬度随Co3Mo2Si初生树枝晶体积分数的增加而提高；与激光熔化沉积Co3Mo2Si单相三元金属硅化物相比，钻基同溶体增韧的Co3Mo2Si三元金属硅化物合金的韧性显著改善，枝晶间钴基固溶体或Co／Co3Mo2Si共晶体积分数越高，合金的韧性越好。

Abstract:

The ternary metal silicide Co3Mo2Si is expected to be a promising wear resistant material due to its inherent high hardness, strong anomalous hardness-temperature dependence and covalent-dominated strong atomic bonds. Poor ductility from room to intermediate high temperatures is currently the main obstacle preventing it from practical industrial applications. In order to improve the ductility of Co3Mo2Si ternary metal silicide, Co solid solution toughened Co3Mo2Si ternary metal silicide alloys were designed and fabricated by the laser melting/deposition process. As-solidification microstructure of the Co/Co3Mo2Si metal silicide alloys was characterized by optical microscopy (OM), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) and Vickers microhardness measurement as a function of Co content. The Co/Co3Mo2Si ternary metal silicide alloys have a dense and uniform microstructure consisting of the Co3Mo2Si primary dendrites and the interdendritic Co/Co3Mo2Si eutectics. Volume fraction of Co3Mo2Si primary dendrites (72%~92%) and the average hardness (8000 MPa~11 000 MPa) of the alloys decrease with the increase of Co content. Compared with the single-phase Co3Mo2Si ternary metal silicide, the Co toughened Co3Mo2Si alloys have excellent balance of strength and ductility, which was attributed to the effective toughening of ductile cobalt solid solution.