Effects of Friction Stir Processing on the Microstructure and Mechanical Properties of Fusion Welded 304L Stainless Steel

: A variation of FSW, friction stir processing (FSP), has been used to modify selected regions of materials to enhance specific properties while eliminating fusion welding defects such as porosity, cracking, and the cast microstructure. The combination of fusion welding defects and high tensile residual stresses caused by the solidification of the molten weld pool adversely affect the post weld service integrity. FSP has been demonstrated to eliminate many of these problems while at the same time improving the resulting properties. FSP has been utilized to locally process regions of arc weldments in 304L stainless steel to improve the service integrity. The cast microstructure and coarse delta-ferrite is replaced with a fine-grained wrought microstructure. This paper presents a preliminary processing window for FSP of 304L stainless steel, the resulting microstructure associated with this process window, along with considerations given to mechanical properties and corrosion.