Research On Properties And Interface Boding Of Dissimilar Materials Surfacing Layer With Plasma Surfacing

Valves are very important in national economic construction,but sealing faces of valves are easy to be corroded and abraded,which were vulnerable to be damaged. So,it is significance to research the way how the wearable alloy powders were surfacing on sealing face, which would prolong the lifetime of valves and increase the economic performace.Albronze alloy powers were surfaced on 20g and HT200 with weak plasma arc under different welding parameters and DC transverse direction magnetic field. The hardness, wearing resistance, erosion resistance, microstructure and interfacing bonding mechanism of surfaing layer were tested and studied. The influence rule and acting mechanism of magnetic field currents and welding currents on properties and microstructure of surfacing layer were researched. The main results are as following:(1)The optimal value of forming, properties and microstructure of albronze with low carbon steel & cast iron surfacing layer are obtained when Q=17g/min, V=120mm/min, I=110A. For albronze and low carbon steel, the hardness is 259HV,wear extent is0..0088g,fraction factor is 0.3;For albronze and cast iron, the hardness is 233.7HV, wear extent is 0.128g, fraction factor is 0.35. The microstructure of albronze surfacing layer consists ofα-Cu and second phaseγ2,β′&κ,which has second phase invigoration effect. The polarization potential ofγ2 phase is low, so erosion resistance ofγ2 phase is not good and will erode at first. The erosion resistance of surfacing layer is not good when I=110A.(2)The interface bonding of surfacing layer is good when surfacing current is proper, fusion line is clear and clean, the phenomenon of element diffusion appears along surfacing layer interface. The component segregation will appear when surfacing current is too big, when the diffusion of element iaggravate. The bonded mode of albronze surfacing layer is lamellar bond. Through physical contact, face activation and inter diffusion, the surfacing layer bonds with based metal for atom size. (3)The optimal microstructure and properties of surfacing layer are obtained when I=110A and I_m=1A. For albronze and low carbon steel surfacing layer, hardness is 284HV, the wear extent is 0.0063g, fraction factor is 0.3;For albronze and cast iron surfacing layer, hardness is 252.9HV, wear extent is 0.0088g, fraction factor is 0.35. The microstructure of surfacing layer consists ofα-Cu and second phase K andβ,which has second phase invigoration effect. The erosion resistance of surfacing layer is best at this time, the corrosion potential is highest and corrosion current is lowest. The best state of interface bond also appears at this time, the breadth of transition layer is proper and metallic compound hasnot been found.(4)The"M stirring","S stirring"and"F stirring"will affect the solidifaction and crystallization of surfacing layer metal, which are induced by extra magnetic field. The effect of"F stirring"is best, which can refine the microstructure, nodulare impurity and improve the distribution of phae and the properties of surfacing layer. But the magnetic field current is too big to properties of surfacing layer because of the electromagnetic damping.