Experimental Investigation of Underwater Stud Friction Stir Welding Parameters

Optimum parameter settings for stud friction stir welding (SFSW) in underwater conditions are experimentally investigated using M12 electrical galvanized bolts of grade 8.8 and plates of S235 (St37) steel. Several sets of SFSW experiments in underwater conditions are performed without a shroud to investigate the approximate input parameter (i.e., speed, pressure, heating time, and upset) interactions. The tensile strength of each stud weld is measured to investigate welded joint performance. The pressure ranges and corresponding speeds which produce consistent strength levels are identified. Further experimentation is performed within the selected pressure ranges to investigate the variation of tensile strength. The upset is also measured as an output performance factor. The microstructure is examined to observe different regions. Hardness is measured at each region to investigate the martensite formation.