Mo2FeB2系硬質合金の焼結機構におよぼすNiおよびC量の影響

概要

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Effects of Ni and C content on the liquid phase sintering of Fe-6 wt%B-48 wt%Mo-(0-7)wtooNi-(0.0l-0.3)wt%C alloys are studied by means of DTA, dilatometric measurements, microstructural observations and mechanical properties. The results are summarized as follows. (1) In proportion to the increase of Ni and C contents, the temperature ranges of liquid forming reactions of γ-Fe+Fe2B→L1 and γ-Fe+Mo2FeB2→L2 shift to lower temperatures, respectively. As the C content increases, another liquid forming reaction, γ-Fe+Fe3C→Lc, occurs in addition to the L1 and L2 forming reactions. The Lc forming reaction occurs slightly below the temperature range in which the L1 reaction occurs. (2) When the Ni content is in the range of 2-3 wt% and the C content is low (0.01 wt%), the sintered alloy consists of Mo2FeB2, a small amount of Fe2B as hard phases and a martensitic binder. However, transverse rupture strength and hardness are not improved. (3) Highest transverse rupture strength values around 2.2 GPa are obtained for the Fe-6 wt%B-48 wt%Mo-3 wt%Ni-0.1 wt%Calloy, which consists of the martensitic binder phase.