Friction Stir Processing of 304L Stainless Steel for Crack Repair

Friction stir processing (FSP) was investigated as a method for repairing cracks in 304L stainless steel. Healing feasibility was demonstrated by processing a tapered crack and a series of randomly sequenced cracks with different widths. It was possible to heal a crack that begins narrow and then progressively widens, but processing a crack that starts too wide created voids that could not be closed up. Tension and hardness testing of 304L plates processed under different conditions were performed in order to assess the effect of processing on weld and heat affected zone properties. Corrosion testing was also carried out, in order to evaluate the effect of FSP on potential sensitization of the stir zone. After 1000 h of testing in saline solution at room temperature it was found that no corrosion products formed on the base material controls or on any of the friction stir processed specimens.