Sintering Mechanisms and Mechanical Properties of Mo₂FeB₂ Based Hard Alloys

Abstract

The sintering phenomena of Fe-6 wt%B-(0-58) wt%Mo alloys are studied by means of TG-DTA, dilatometric measurements and X-ray diffractometry. In addition, the mechanical properties of the sintered alloys are discussed.
The optimum process-property relations can be summarized as follows:
(1)Highest transverse rupture strength values around 200 kg/mm² are obtained for the 48 wt%Mo alloy.
(2)The 48 wt%Mo alloy consists of the Mo₂FeB₂ and a small amount of Fe₂B as hard phases and of an Fe binder phase.
(3)The Mo₂FeB₂ phase is formed in the temperature range 750-1090°C. The liquid phase sintering of the alloy is accomplished by two different liquid phases produced by two different reactions. The first reaction, γ-Fe+Fe₂B→L₁, occurs in a temperature range 1090-1150°C, this being somewhat lower than expected for the binary Fe-Fe₂B system presumably due to the presence of Mo. The second reaction, γ-Fe+Mo₂FeB₂→L₂, occurs above 1150°C.
(4)The optimum sintering temperature lies slightly above the temperature at which the reaction γ-Fe+Mo₂FeB₂→L₂ occurs.