Pipeline girth friction welding of the UNS S32205 duplex stainless steel

Abstract

In most cases, welding is a critical issue and one that motivates a constant search for alternative solutions that can both reduce costs and increase efficiency. Supported by numerical simulation data, the present work evaluated the microstructure across the weld cross-section and the respective Charpy impact toughness at 0 °C for the different regions formed for the pipeline girth friction welding of the UNS S32205 alloy. The results indicated that the most important microstructural modifications occurred at the weld interface as a consequence of the combination of very high temperature and a great deal of plastic deformation. The considerable drop in impact toughness for this region is related to substantial changes in austenite morphology and an excessive ferrite grain growth. Moreover, pronounced austenite reorientation and increased ferrite fraction surrounded the weld interface, which in turn took its proportional toll on toughness. Finally, the analyses of the crack profiles revealed that as the crack advances to regions of either reformed or reoriented austenite crystals, cleavage facets appear on fracture surfaces in varying intensity, producing the corresponding reduction in impact toughness.