The Effect Of MgO Content On Microstructure And Properties Of Ni-WC Coating Formed By Vacuum Fusion Sintering

Vacuum Fusion Sintering coating as one of surface-coating technologies makes good effect on improving properties of the material. So there is very important significance to do some researches on it.Made Ni-base alloy tungsten Carbide composite coating of different MgO content on 45 steel matrixes by the way of Vacuum fusion sintering. The coating's microstructure and the morphology of WC were observed by Optics Microscope (OM) and Scanning Electron Microscope (SEM), the elements diffusion on the fusion band were checked by Energy-Dispersive Spectrometer (EDS); The Rockwell hardness of coatings' surface and micro-hardness of coatings' longitudinal section were measured by Rockwell hardometer and micro-hardness instrument; The wear-resisting property,thermal fatigue of the coatings and corrosion resisting property were also tested. The results showed that:(1) There is obvious transition region between coating and matrix with addition of MgO , it is bonding closed; There is many elements diffusion on transition region, element of Ni, Cr, Si, C etc., in the coating diffuse into the base metal, the Fe element in the base metal diffuse into the coating, and Fe, Ni diffusion is the most obvious; The defects in the coating become little, WC in the coating is further refined, and its distribution changes uniform with adding proper quantities MgO. In this paper, when the content of MgO is 0.5 %, the coating is the best.(2) Adding MgO makes effects on the properties of the coatings, the concrete content is as follows:1) Hardness: when the content of MgO is 0.5%, the surface's hardness and section's micro-hardness are the highest, HRC of the surface's hardness reaches 59.13, the highest of the section's micro-hardness is 823HV;2) Wear resistance: when the content of MgO is 0.5%, the wear-loss weight is the least; the wear resistance is the best; wear mechanics is grinding abrasion by observing the grinding crack pattern;3) Thermal fatigue property: when the content of MgO is 0.5%, the thermal fatigue property of the coating is the best; during the course of 750℃(?)20℃thermal cycling, the times of crack appearing is 21;4) Corrosion resisting property: When the content of MgO is 0.5%, the salt spray corrosion rate is the lowest; the corrosion resisting property of coatings is the best.