Effect of Mn on valence-electron structure and properties of hard phase in Mo2FeB2-based cermets

Based on the empirical electron theory (EET) of solids and molecules, the valence-electron structures (VES) of the hard phases in Mo2FeB2-based cermets were calculated, and the relationship between the VES and properties was determined. The results indicated that the brittleness was due to weak bonds. The hardness of the phases with the same crystal structure could be compared using the covalent electron pairs, n(alpha), values on the strongest bonds and the plasticity by the sum of n(alpha) values for the covalent bonds. Mn dissolution in boride phase improved the plasticity of the hard phase, which should be advantageous for strengthening Mo2FeB2-based cermets. Based on those results, a Mo2FeB2-based cermet added with Mn was manufactured; the transverse rupture strength of Mo2FeB2-based cermet was improved. (C) 2009 Elsevier Ltd. All rights reserved.