BULK Mo_2FeB_2 BASED CERMETS FABRICATED BY MECHANICAL BALL MILLING AND REACTION BORONIZING SINTERING

摘要

The ternary boride Mo_2FeB_2-based cermets were fabricated successfully with Mo, FeB, Fe, Cr, and Ni mixed powders by mechanical ball milling and reaction boronizing sintering. The results indicate that there is no alloying reaction between powders during milling; at milling times from 4 to 24 h, the morphology of the mixed powder becomes finer and the powder distribution becomes more and more uniform. However, as milling time exceeds 24 h, the morphology and distribution have no obvious change. The bulk Mo_2FeB_2 can be fabricated with sintering temperature increasing from 1437 to 1517 K. The relative density, hardness, and bending strength increase with temperature increasing from 1437 to 1477 K; however, the relative density has no obvious change and the hardness and bending strength decrease with temperature exceeding 1477 K. The result also indicates that when the sintering time increases from 25 to 50 min, the relative density, hardness, and bending strength of the sample increase; however, the relative density has no obvious change and the hardness and bending strength decrease with the time exceeding 50 min.