The influence of Mo/B atomic ratio on microstructural evolution and mechanical properties of Mo2FeB2-based cermets

Abstract

AbstractMo2FeB2-based cermets were prepared with various Mo/B atomic ratios in the range of 0.8 to 1.1. The microstructure and crystalline phases were studied through scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray analysis and X-ray diffractometry. The results indicated that as the Mo/B atomic ratio increased, the morphology of the hard phase gradually transformed from long-strip to near-equiaxed. The tendency of transformation in the range of 1.0 to 1.1 was more significant. Two typical cermet samples (Mo/B = 1.0, Mo/B = 1.08) of different morphologies were studied with transmission electron microscopy. As the Mo/B atomic ratio increased, the average particle size decreased, inhibiting the nucleation of the particles, the anisotropy of different crystallographic planes reduced, the particles transformed from long-strip to the near-equiaxed shape. Moreover, it could be found from X-ray diffractometry results that the disparity between the crystal lattice constants c and a gradually diminished and the surface tension differences of the amorphous surfaces decreased, resulting in the anisotropy of different crystal-lographic planes gradually decreasing. The cermets with Mo/B = 1.02 demonstrated the highest transverse rupture strength, as well as the hardness and improved fracture toughness values of 2367.5 ± 50 MPa, 88.2 ± 0.1 HRA, and 27.6 ± 0.5 MPa · m1/2, respectively.