| The centrifugal compressor blade will lose efficacy when it serviced in the condition of high content CO2/H2S for a long time. To investigate the corrosion behavior of blade material FV(520)B stainless steel in working conditions is not only conducive to the material selection of compressor impeller, but also has important significance on the corrosion protection. Scraping the failture impeller will be a great waste of resources because of its high precess cost. Remanufacturing may be a good solution. The presence of corrosion layer is repulsion for remanufacturing. It has a practical significance for impeller remanufacturing to investigate the rejection mechanism and remove methods of corrosion film.By high temperature and high pressure autoclave CY-300, the specific conditions ware simulatied and corrosion films were prepared after corroded for different time. The morphology, structure, composition of the corrosion layer and the change rules were analyzed by using SEM, XRD, XPS. The corrosion behavior and mechanism of FV(520)B stainless steel in the condition of CO2/H2S were investigated. The effects of corrosive medium, H2S partial pressure and temperature on corrosion were researched in the condition of CO2/H2S. The influence of sulfide corrosion layer on remanufacturing was investigated by plasma spray welding on FV(520)B stainless steel surface after different sulfide corroded time. The low temperature plasma technology was used to remove the corrosion layer. By investigating the mechanism, process and parameters, it was explored to use the low temperature plasma technology to improve or remove the sulfide corrosion layer.The results show that the corrosion rate decreases gradually with extension of the corrosion time for the FV(520)B stainless steel corroded in CO2/H2S. The specimen surface’s roughness increases at first and then decreases. The corrosion product is granular. When corrosion is over, the solution is black suspension. The hanging turbid material consists of S and FeS2. In the early stage of the corrosion, the corrosion rate is higher with the forming of FeS, FeCO3, Cr(OH)3. As the corrosion continues, the Cr(OH)3 protective film forms and inhibites the corrosion. The corrosion particle FeS is oxidized form S and FeS2, and decreases the samples’ surface roughness. When complete protective films formed, no corrosion occurres again.In the influence factors’research of FV(520)B stainless steel in CO2/H2S condition, it was found that the corrosion at 150℃ is serious than at 90℃ and at 210℃. When the partial pressure of H2S increases from 0.3MPa to 1.5MPa, the shape of corrosion products change from muscoid into granular, corrosion become more serious. Corrosion is more serious when the corrosive medium is NaCl solution.Preparation of sulfur corrosion layer under CH4/H2S conditions, a large number of inclusions and pores were found in the organization after plasma spray welding on the specemen with sulfur corrosion layer prepared under CH4/H2S conditions. With the corrosion time increasing, inclusions and pores increased. In three-point bending test, with the increase of corrosion time, the specimen bending strength decreased.The corrosion layer formed in the condition of CH4/H2S was removed by using the low temperature plasma. The field emission current forms on micro convex objects on the surface of sulfide corrosion film, and then the sulfide on surface is evaporated. The electronic work function of sulfide is lower than that of matrix elements. Under the same conditions, the arc spots preferentially forms on the sulfide surface. By observing the changes of voltage, sulfides can be effectively removed and do not hurt the matrix. The removal efficiency increases with the current. After removal, the sulfur content on specimen surface is very low. Low temperature plasma technology for the removal of sulfide corrosion film is feasible. |
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