Investigation Of Hot Corrosion Resistance For P92 And P122 Ferrite Heat Resistance Steel Welded Joints

The pollution of sulphate and halide from fuel burning or other mixing salt in the main boiler steam pipeline leads to heat erosion losing efficiency, therefore it is of great significance that the use environment for weld joint in simulation boiler pipeline is carries on anticorrosive performance research. The P122 and P92 steel in this paper is now widely used in the boiler pipeline at present.This thesis directs against the real environment for use, choosing NaCl and Na2SO4 as the corrosive agent, analyzes and compares corrosion performance of P92, P122 in the various condition of treatment including different salinity, different temperature and after shot-peening. The following conclusion are shown through the test: the heat erosion intensity of P92 and P122 steel weld joint increase notably along with the increase of temperature; With the increase of NaCl content in the membrance, the heat erosion intensity of P92 and P122 steel weld joint also shows significant increase in the trend; Under the condition of 650℃and NaCl:Na2SO4=2:1, the heat erosion performance of P92 and P122 steel joint surface with shot-peening is superior to that without shot-peening. Meanwhile the thesis carry on XRD analyze and morphology SEM observed to heat erosion prodution of P92 and P122 steel joint.The result show the main heat erosion production of P92 steel joints is Fe2O3 and Cr2O3; the main production of P122 steel joint is is Fe2O3, NaFeO2 and Cr2O3.Meanwhile, the heat erosion mechanism of P92 and P122 steel welded joint is also discussed. The mechanism on heat erosion of P92 steel is taking place: Corrosion pregnant period, the joints surface of P92 mainly takes place chromium selective oxidation reactions and produces protective oxide film; corrosion stage with higher speed, melt salt keep in touch with P92 matrices through permeating protective oxide film, corrosion process follows sulfurization-oxidation mechanism. Corrosion mechanism of P122 is different slightly from that of P92: mix salt NaCl and Cr2O3 of membrane mainly react, the protective oxide film with great destructive effect to facilitate the infiltration of molten salt and accelerate the corrosion process.