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 E_Z 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 E_Z 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.