Microstructure evolution and wear properties of bulk MoSi2 fabricated by field activated sintering

Field activated sintering (FAS) was employed to fabricate dense bulk MoSi2 from Mo and Si powders. During the FAS process, Si was melted first, and then Mo was dissolved leading to a precipitation of MoSi2. A eutectic reaction of MoSi2–Mo5Si3 resulted from a combined effect of Mo–Si exothermic reactions and field induced Joule heating. With hyper-stoichiometric amount of Si (Mo/Si = 1:2.06), the FAS MoSi2 is free of Mo5Si3 phase. Subsequently, an un-lubricated sliding wear test of MoSi2 against carbon steel was conducted. Both normal load and temperature have crucial points related to a transition from mild to severe wear. Sliding speed and relative density have a negative effect on wear rate. In addition, at room temperature the wear is with a protective layer composed of oxide and transferred substance, whereas poor oxidation resistance leads to spalling of the layer and brittle fracture at an elevated temperature up to 500 °C.

Research Highlights
► Field activated sintering was employed to synthesize dense bulk MoSi2 in one step.
► MoSi2-Mo5Si3 eutectic was discovered in sintered MoSi2.
► With hyper-stoichiometric amount of Si, the FAS MoSi2 is free of Mo5Si3 phase.
► The dry sliding wear of MoSi2 was studied at both room temperature and 500 °C.