Study Of Remanufacturing On Ni60 High Temperature Alloy Coating By Micro-plasma Technology

Micro-Plasma arc welding is one of methods of plasma arc welding when the welding current below 35 A,This welding method is extensively applied in sheet metal welding because its energy concentrated and low heat input.Remanufacturing is a method by using advanced surface engineering technology which repairs the damaged part to reach its original quality and property.This paper is aimed at studying influence of different surfacing parameters on surfacing morphology and property.Also include the possibility of remanufacturing special materials.In this paper,using steel Q235 as base metal,cladding self-fluxed Ni60 alloy powder on steel Q235 by different parameters.Different surface morphology a nd property layer are obtained,by studying on different hardfacing specimens we can draw a conclusion about influence of parameter on hardfacing metal.Experiment parameters include welding current,powder feeding rate and welding velocity,We also using optical microscope,scanning electron microscope and energy disperse spectroscopy to analyse microstructure and second phase of surface layers.The result shows that surfacing morphology is affected by welding parameters,welding current and change heat input which affects welding pool depth.Powder feeding rate affects the thickness of the surfacing.Welding velocity affects continuity of the surfacing,The average hardness of surface layer center is 500Hv_0.3 when current is 33 A,the average hardness will drop to 450Hv_0.3 when current increases to 36 A.When powder feeding rate is 13g/min the average hardness of surface layer appears minimum,it's about 430Hv_0.3,increasing powder feeding rate to 16g/min the average hardness add to 500Hv_0.3,further increasing powder feed rate will increase the average hardness slightly but pore and crack will appear in the surface layer.Using optical microscope to observe grain morphology,columnar grains are dominant when close to bonding line,and weld center are mainly equiaxed grains.Using Scanning Electron Microscope and energy disperse spectroscopy to observe the microstructure of surface layer,flake and net shape material are precipitated near the grain boundary,flake shape material are mainly carbon chromium compounds through EDS analysis and silicon nickel compounds,net shape material are mainly ferrum carbon compounds.Multi surfacing layer appears apparent boundary after etched,and the two surfacing layers show different anti-corrosion ability,the latter surfacing layer is weaker than former,because the former surfacing layer undergo the process of heat treatment,it can eliminate element segregation effectively,making element Cr and Ni disperse in matrix g uniformly,so the whole surfacing layer shows good anti-corrosion property.