鉄硼化物系硬質合金の焼結機構

概要

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The ternary Fe-6%B-x%Mo alloys have a composite microstructure consisting mainly of a complex boride Mo2FeB2 as a hard phase and a ferritic binder. The mechanism of liquid phase sintering of this alloy was investigated by means of dilatometry, differential thermal analysis, X-ray diffraction, and scanning electron microscopy. A fine composite microstructure of Mo2FeB2 and ferrite was produced from powders of Fe, Mo and FeB by a reaction sintering process involving two liquid phases. The hard phase Mo2FeB2 is produced in the compact prior to liquid formation. Above 1, 365K, considerable densification results from the initial stage rearrangement of the solid phases (austenite and Mo2FeB2) coexisting with the first formed liquid phase (L1). Another liquid (L2) which forms above 1, 415K, where Mo2FeB2 is the only coexisting solid phase, is required for complete densification. L2 having a high solubility for Mo2FeB2, provides for solution/reprecipitation process which characterize the intermediate stage of liquid phase sintering. The effective separation of the initial and intermediate stages by L1 and L2 is considered essential for the control of the sintered microstrucure of the ternary alloy.
社団法人粉体粉末冶金協会の論文