鉄-モリブデン複硼化物系硬質合金の特性および組織におよぼすMo/B原子比の影響

概要

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Fe-5B-xMo model alloys with five levels of Mo content corresponding to Mo/B atomic ratio ranging from 0.7 to 1.1 were prepared to study the effects of Mo/B atomic ratio on the mechanical properties and phase formation during liquid phase sintering. The effects of Mo/B ratio on the morphology, chemical composition and lattice parameters of a Mo2FeB2 type complex boride were also studied. In conclusion, a high transverse rupture strength of approximately 2.2 GPa was obtained for the alloys when Mo was added to match the stoichiometric Mo/B atomic ratio, 1.0 of Mo2FeB2. In addition to the two main constituents, namely the Mo2FeB2 type complex boride and the ferrous binder, in the Mo deficient alloys of which Mo/B atomic ratio was below 1.0 the Fe2B was detected as a third phase, while Mo excess alloys of which Mo/B atomic ratio was above 1.0 contained M6C (M: Metal). The morphology, chemical composition and lattice parameters of the Mo2FeB2 type complex boride varied when the Mo/B atomic ratio of the alloy was high in a manner related to the atomic ordering in the Mo2FeB2 structure.