Effect of V doping on the microstructure and mechanical properties of Mo₂FeB₂-based cermets and investigation on the enhancement mechanism

In this study, the effect of V doping on the microstructure and mechanical properties of Mo₂FeB₂-based cermets was explored. The doped V element was mainly dissolved in the Mo₂FeB₂ particles to substitute the Mo atom inside without generating a new phase. Doping V element increased the volume fraction of borides and the forming temperature of the liquid, thus resulting in the formation of micro pores in Mo₂FeB₂-based cermets. The appropriate V additions simultaneously enhanced the hardness and transverse rupture strength of Mo₂FeB₂-based cermets, while the excessive V additions generated negative influences. The nanoindentation results indicated that the intrinsic hardness and Young's modulus of Mo₂FeB₂ particle were enhanced monotonously with the increasing V contents. However, the V-containing Mo₂FeB₂ particles exhibited more brittleness. The first-principles calculation results showed that the enhanced covalent bonds in Mo₂FeB₂ contributed to the increased hardness. Moreover, V doping decreased the structural stability of Mo₂FeB₂ by forming the anti-bond. Additionally, the variations of bulk modulus, shear modulus and Poisson's ratio caused by the V doping were also discussed based on the calculation results.