Study On Procedure And Performance Of Nickel-Base Alloy MIG Surfacing

The corrosion of steel is going on all the time,with the development of economy and the deteriorating environment,the consumption of steel is increasing.In the petrochemical,nuclear power and thermal power fields,the traditional carbon steel and stainless steel materials have been unable to meet the requirements of use,they are will occur corrosion failure,in severe cases,it also cause accidents.This poses a very great threat and loss to normal production operations.Preparing a surfacing layer of with corrosion resistance property in the carbon steel surface through the surfacing technology can reduce the corrosion loss,it also has important economic benefits.Inconel 625 Nickel-base alloy have a wide range of applications due to their excellent resistance to corrosion.In this paper,Inconel 625 alloy were surfacing on low carbon steel by pulse MIG welding method,and the forming process of Inconel 625 alloy MIG surfacing was studied,and analyzed microstructure and performance of the surfacing layer.The tests of pulse MIG surfacing Inconel 625 alloy showed that using reasonable welding parameters can form beautiful surfacing layer which had a good combination with substrate,it also had a smaller penetration depth.Welding torch swing helped liquid metal flow and spread;with the welding current increasing and welding speed decreasing,the thickness and width of the surfacing layer increased;the thickness of the surfacing layer decreased and the width increased with the gun swing amplitude increasing.The microstructure of the surfacing layer consists of plane crystal and cell crystal at the bottom of the surfacing layer,central cell dendrites and equiaxed crystals in the upper part of the surfacing layer.The content of Fe in different parts of the surfacing layer varies,and the content of Fe at the bottom is higher than that in the upper part.There were two kinds of precipitates in the surfacing layer,they were carbide and Laves phase,carbide were small particle with regular shape and small size,Laves phase were larger in size and irregular in shape,these two precipitates mainly distributed in the crystal room.As the welding current increases,the size of the precipitated phase became significantly larger,and Laves phase changed from a dispersive distribution to a continuous one.When the welding speed is reduced,Laves phase appeared at the bottom of the surfacing layer.Laves phase also appeared at the bottom of the surfacing layer when the welding torch didn't swing,Laves phase in the upper part of the surfacing layer is continuously distributed in the form of a network.The size of carbide precipitated in the multi-layer increased,and Laves phase became a sheet.The hardness of surfacing layer was higher than that of substrate,and the hardness of surfacing layer and substrate reached the maximum at the bottom of the surfacing layer.Decreasing of welding speed and swing amplitude and increasing of welding current all increased the hardness of surfacing layer.The corrosion resistance of surfacing layer at different thicknesses was different,the top of the surfacing was best,followed by the center of the surfacing layer,the bottom of surfacing layer had the worst corrosion resistance.The corrosion resistance of surfacing layer under different parameters was different,and the corrosion resistance of the surfacing layer was better under a smaller welding current and a larger welding speed.