Study On The Welding Procedure And Corrosion Resistance Of UNS8825 Clad Pipe

As the researching progress of new alternative energy slowly,oil and gas are the most important role in the world and the key for country development.Many oil and gas projects became strong corrosive environments which contain H₂S/C1^-/CO₂by hundreds of years exploitation,and big amount of the nickel-based alloys had used costly for oil and gas transportation and storage to meet the safety and security requirement.This paper had conducted a systematic study on the clad pipe,low-cost and suitable corrosion-resistance,which are carbon steel A333GR.6 seamless pipe as the base pipe and 825 alloy as the clad layer.The consumable wire was used for the 825 clad pipe was ERNi Cr Fe-1,deposited metal belongs to the Ni-Fe-Cr-Mo-Cu series alloy,and the hot-wire TIG welding process was used.Further tests were done for checking the property of the 825 clad pipe,the experiment of metallographic and XRD indicated that the microstructure of cladding layer was FCC austenite;The LEIS test results of the clad pipe cross-section shown that the anti-corrosion ability increased from location of the carbon steel to the cladding layer,which demonstrated the cladding layer had greatly improved the corrosion resistance of the pipe;the polarization curve and EIS curve of the electrochemical test shown that the corrosion resistance and the corrosion rate of the cladding metal decreased as the temperature and Cl^-densiy increasing in the Na Cl solution;the DL-EPR test results demonstrated the reactivation value of the cladding layer metal increased as the treating temperature increasing,and the reactivation value Ra reaches a peak near 720?,which means more severely intergranular corrosion.The experimental results of pitting corrosion,intergranular corrosion and SSC shown that the clad pipe is satisfied for the materials engineering requirement.The SSRT,slow strain rate tensile test,shown that welding residual stress significantly shortens the failure time and exacerbates the failure,and the coexisting environment of H₂S and CO₂does the same affection.however,the result of SSRT indicated that the cladding metal had a good performance in the environment of coexistence welding residual stress&H₂S/CO₂,which plastic strain ratio Ep R,the fracture-section shrinkage ratio RAR and the time failure ratio TTFR are greater than 90%.