The influence of hydrogen pre-charging on the stress corrosion susceptibility of SCR welded joints
This study shows the influence of hydrogen pre-charging on the stress corrosion cracking(SCC)susceptibility of steel catenary riser(SCR)welded joints made of X65 through microstructural analysis,slow strain rate tensile test(SSRT),and fracture surface analysis.The results reveal that the fine-grained heat-affected zone(FGHAZ)of the welded joints primarily comprises fine and uniform ferrite(F)and pearlite(P),significantly enhancing the mechanical property of this zone compared to other heat-affected zone.In contrast,the coarse-grained heat-affected zone(CGHAZ)is characterized by large block of proeutectoid ferrite(PF)and M-A constituent,resulting in poor SCC resistance in this area.Although the elastic stage of the stress-strain curve of SSRT sample under various hydrogen pre-charging time nearly coincide,hydrogen pre-charging decreases the tensile strength of the samples.Additionally,in a NaCl solution corrosion environment,the stress corrosion susceptibility coefficient EZ of the samples hydrogen uncharged and after four days of hydrogen pre-charging are 0.67％and 11.14％,respectively;in an H2S corrosion environment,the stress corrosion susceptibility coefficient EZ values for the samples hydrogen uncharged and after four days of hydrogen pre-charging are 11.96％and 46.38％,respectively.This demonstrates that hydrogen pre-charging reduces the SCC resistance of welded joints in both corrosion environment.The samples undergo ductile fracture in the air environment,while quasi-cleavage fracture predominates in both corrosion environment.Hydrogen pre-charging reduces the material toughness and exacerbates microcracks and hole near the fracture surface,thereby reducing the material's resistance to SCC.
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