粘结相含量和相组成对Mo_2FeB_2基金属陶瓷断裂韧性的影响

Effect of binder phase contents and compositions on fracture toughness of Mo_2FeB_2 based cermets

通过真空液相烧结工艺制备不同粘结相含量和相组成的Mo_2FeB_2基金属陶瓷,并用压痕法测量其断裂韧性,研究粘结相含量和相组成对Mo_2FeB_2基金属陶瓷断裂韧性的影响。结果表明:粘结相含量对Mo_2FeB_2基金属陶瓷的断裂韧性具有一定影响,当粘结相含量(质量分数)由27%增加到37%时,断裂韧性从12.8 MPa·m^(1/2)提高到了17.3 MPa·m^(1/2);与粘结相含量的影响相比,粘结相相组成对Mo_2FeB_2基金属陶瓷的断裂韧性具有更加显著的影响,当粘结相为铁素体时,金属陶瓷的断裂韧性为28.5 MPa·m^(1/2),增加了约一倍;硬质相颗粒与粘结相的沿晶断裂,尤其是粘结相的撕裂对其断裂韧性的增加起重要的贡献。

A series of Mo_2FeB_2 based cermets with different binder phase contents and compositions were fabricated by liquid phase sintering. The fracture toughness was measured by the indentation method, and the effects of binder phase contents and compositions on fracture toughness of Mo_2FeB_2 based cermets were investigated. The results show that the fracture toughness increases from 12.8 MPa·m^(1/2) to 17.3 MPa·m^(1/2) with an increase of binder phase content(mass fraction) from 27% to 37%. In addition, the effect of the binder phase compositions on the fracture toughness of Mo_2FeB_2 based cermets is more obvious compared with that of the binder phase contents. The fracture toughness improves to 28.5 MPa·m^(1/2) when the binder phase is ferrite, which is twice higher than that of martensite binder phase. The toughening mechanism is characterized by dimple rupture across the binder and near a binder/hard phase interface.