Corrosion Resistance Study Of Copper-bearing Super Austenitic Stainless Steel

Thermal power plants,incinerators,oil refineries and other factories will produce a large number of waste gas during production,which contains a high level of SO₂.Its emissions will not only harm the environment and organisms,but also cause economic losses due to acid rain corrosion,which has become one of the increasingly prominent environmental protection issues.At present,in order to control SO₂emission,flue gas desulfurization devices are used all over the world,among which the widely used method is limestone-gypsum wet desulfurization.However,the corrosion damage o f flue gas desulfurization devices is serious after this method is adopted,especially in the absorption tower and the chimney,which causes great economic losses.Based on the shortcomings of traditional anticorrosive materials,such as poor wear resistanc e,easy to fall off and poor corrosion resistance,as well as the expensive price of 654SMO and Ni base alloy,the research and development of new anticorrosive materials is imminent.In order to reduce the material cost and prolong the service life of the equipment,it is very important to improve the corrosion resistance of super austenitic stainless steel by reasonably increasing the content of corrosion resistant elements.Copper(Cu)is often used to improve the corrosion resistance of stainless steel,so this paper takes20Cr-18Ni-6Mo-0.2N super austenitic stainless steel as the research object,and studies the corrosion resistance mechanism and reasonable content of super austenitic stainless steel by changing the content of Cu.The effects of Cu on th e solid solution behavior,precipitation behavior,corrosion resistance and passive microstructure of 6Mo super austenitic stainless steel were studied by using the physicochemical phase analysis,electrochemical method,chemical immersion method and high temperature furnace,metallographic microscope,scanning electron microscope,transmissionelectron microscope,and X-ray photoelectron spectroscopy equipment.According to the analysis of solid solution behavior,it was found that Cu promoted the recrysta llization of super austenitic stainless steel,coarsed the grains,and promoted the dissolution of precipitated phase after the heat preservation at1000??1200?for 60 min.According to precipitation behavior analysis,?phase,Laves phase,and?phase were the main precipitated phases after 120 min insulation at 600??1100?.Cu inhibited precipitation of?phase and promoted precipitation of Laves phase and?phase.According to the analysis of corrosion resistance,it was found that the resistance to uniform corrosion,pitting corrosion and crevice corrosion was the best when the Cu content was 1 wt.%,and the expansion of pitting corrosion was inhibited when the Cu content was 1 wt.%.Based on electrochemical analysis,it was found that the addition of Cu significantly reduced the passive current density and the passive film surface quality and passive film stability were optimal when Cu content was 1 wt.%.According to the passive film analysis,the microstructure of the passive film of20Cr-18Ni-6Mo-0.2N super austenitic stainless steel in Cl^-solution and H₂SO₄solution is three layers.The addition of Cu changes the distribution of the passive film oxides.When the Cu content is 1 wt.%,the thickness and continuity of the chromium and molybdenum oxide layers are the best.