Effect Of WC,VC On Microstructure And Properties Of Mo₂FeB₂-based Cermets

Mo₂Fe B_2-based cermets is an ideal candidate for the wear-resistant materials because of their high hardness,excellent wear-resistance,corrosion resistance,perfect oxidation resistance,fatigue resistance and good metallurgical bonding performance with steel.However,the application of Mo₂FeB₂-based cermets is limited for its low transverse rupture.So the research on the strengthening and toughening of Mo₂FeB₂-based cermets is very important.In this investigation,Mo₂Fe B₂-based cermets were prepared by vacuum liquid sintering method.The effects of different WC addition,sub-micron WC and grain growth inhibitor on the microstructure and mechanical properties of Mo₂Fe B₂-based cermets were studied by X-ray diffraction?XRD?,scanning electron microscopy?SEM?.Firstly,the effects of different WC additions on the microstructure and mechanical properties of cermets has been researched.The results showed that the addition of a certain amount of WC can improve the strength of the cermet.With the increase of WC addition,the hardness of the cermet showed a monotonously increasing trend,and its hardness was up to HRA 85.7.While,the transverse rupture strength?TRS?firstlly increased and then decreased with increasing WC addition.And the maximum values of hardness and TRS are found with 9.0wt%and 3.0wt%WC addition,respectively.The microstructure has a trend to become finer with appropriate addition of WC.The cermets with 3.0wt%WC addition exhibited the smallest grain size,its average grain size reduced to 1.5?m.The effects of sub-micro WC on the mechanical properties and microstructure were studied.The results showed that,compared to the Mo₂FeB₂-based cermets with micron WC addition,the strength of the cermet was significantly improved and the hard particles were refined.The TRS and hardness of the cermets with sub-micron WC addition were higher.The cermets with sub-micro WC addition was obtained with the TRS of 1553MPa MPa and hardness of HRA 86.The fracture micrographs showed that the fracture modes in the two cermets are intergranular and transgranular fracture.Finally,the effects of grain inhibitor VC on the mechanical properties and microstructure of Mo₂Fe B₂-based cermets has been discussed.The results showed that the addition of VC cause the refinement of grains,which was beneficial to the improvement of the strength of the cermet.Both the TRS and hardness increase at first and then decrease with the increase of VC addition.The highest TRS and hardness was obtained for the cermets with 0.4wt%VC addition.Because the addition of VC reduces the solubility of the hard phase in the bonding phase,it inhibit the growth of the hard phase through the solution-precipitation mechanism.