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.