Optimization of Friction Stir Process Parameters to Enhance Sensitization Resistance of Ferritic Stainless Steel Joints

Friction stir welding (FSW) is a novel solid-state joining process that was invented in 1991, it can avoid many problems associated with fusion welding processes, thereby defect-free welds having excellent properties can be produced even in some materials with poor fusion weldability. The present investigation is aimed at to study the influence of FSW process parameters such rotational speed, welding speed and shoulder diameter on sensitization of AISI 409M grade ferritic stainless steel joint. FSW experiments were conducted based on three factors, three-level, and central composite small design. Specimens were extracted from each joint. Modified strauss test and double loop electrochemical potentiokinetic reactivation (DL-EPR) test using an electrolyte of 0.1M H2SO4, 0.4M Na2SO4 and 0.5 ppm KSCN with a PH value of 1.8 at room temperature and at a potential scan rate dE/dt of about 2.5 mV/s, was chosen to evaluate the sensitization of frictions stir welded ferritic stainless steel joints. Activation to reactivation current ratio (Ia/Ir) and corrosion rate were evaluated for each condition and empirical relationships were developed between the process parameters and corrosion rate. The effect of FSW process parameters on sensitization of friction stir welded AISI 409M ferritic stainless steel joints.