Study On High Temperature Chlorine Corrosion Performance Of Inconel625 Alloy And Its Modified Materials

Due to its excellent resistance to high temperature chlorine corrosion,Inconel625 alloy is often used as a coating material in the environment of high temperature chlorine-containing media,but its service life is still limited and the cost is high.Al is added to Inconel625 alloy as Al source material that can form a protective Al₂O₃ scale,which can improve high temperature chlorine corrosion resistance of the alloy to a certain extent.Y as a highly active rare earth element added to Inconel625 alloy can greatly improve the adhesion of the oxide scale and promote the formation of protective Cr₂O₃ layer.Therefore,this paper designed Inconel625-Al and Inconel625-Y systems to study their high temperature corrosion behavior at 600-800°C under N₂-0.5 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂ and N₂-1.0 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂.The research concentrated on the influence of Al and Y addition on the formation of protective Al₂O₃ and Cr₂O₃ oxide scale.(1)The corrosion behavior of Inconel625-xAl(x=3,5,7,10 wt.%)alloys has been studied at 600-800°C under N₂-0.5 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂and N₂-1.0 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂.The corrosion kinetics of Inconel625-xAl(x=3,5,7,10 wt.%)alloys at 800°C under N₂-0.5 vol.%HCl-1.5vol.%O₂-3.0 vol.%CO₂ roughly conform to the parabolic law while those under N₂-1.0 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂ are irregular.The oxide scale structures of the four alloys at 600-700°C are very similar,and all are composed of mixed oxides of Ni and Cr.At 800°C,a large amount of SiO₂ is formed on the surface of Inconel625-3Al alloy,which increases with the HCl concentration.With the increase of HCl concentration,the Al₂O₃ content in the Inconel625-xAl(x=3,5,7,10)alloy oxide film increases,and with the increase of Al content,the Al₂O₃ layer gradually tends from discontinuity to continuous and dense,which provides better protection for the alloy.Compared with Inconel625 alloy,Inconel625-3Al alloy has a higher corrosion rate,while Inconel625-10Al alloy shows more excellent corrosion resistance.As the concentration of HCl further increases,the Al₂O₃ layer becomes more continuous and dense.(2)The corrosion behavior of Inconel625-x Y(x=0.1,0.3,0.5,0.7,1.0 wt.%)alloys has been studied at 600-800°C under N₂-0.5 vol.%HCl-1.5 vol.%O₂-3.0vol.%CO₂ and N₂-1.0 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂.Similar to Inconel625-xAl(x=3,5,7,10 wt.%)alloy,the corrosion kinetics of Inconel625-x Y(x=0.1,0.3,0.5,0.7,1.0 wt.%)alloys at 800°C under N₂-0.5 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂ roughly conform to the parabolic law.With the increase of temperature,the corrosion process gradually changes from mass loss to mass gain.The corrosion kinetics of Inconel625-x Y(x=0.1,0.3,0.5,0.7,1.0 wt.%)alloys at800°C under N₂-1.0 vol.%HCl-1.5 vol.%O₂-3.0 vol.%CO₂ are irregular and the mass gain increase with the of Y content.The oxide scale structures of the five alloys at 600-700°C are relatively similar.The corrosion at 600°C is relatively light,mainly composed of mixed oxides of Ni and Cr,while the surface formed at 700°C is Cr₂O₃ and NiCr₂O₄.With the increase of temperature and Y content,a large amount of SiO₂ is formed on the surface of Inconel625 alloy and it increases with HCl concentration.Inconel625 alloy with low Y content forms a continuous dense Cr₂O₃ layer,showing better corrosion resistance.