High-Frequency Induction-Assisted Hybrid Friction Stir Welding of Inconel 718 Plates

The preheating system is a promising approach to decrease the axial load, improve the weld quality, and enhance the tool life during the friction stir welding (FSW) of high strength material. In the present work, conventional FSW and high-frequency induction heating-assisted friction stir welding (I-FSW) systems were used to join 3 mm thick Inconel 718 plates with a WC-10%Co tool and studied their performances. The welding was carried out at a constant rotational speed of 300 rpm, including varying traverse speeds of 90 mm/min and 140 mm/min and varying preheating temperatures (310 °C, 410 °C, and 700 °C). The results show that good weld joints were possible at high traverse speed (i.e., 140 mm/min) using the I-FSW at low preheating temperature (i.e., 310 °C). Grain refinement in the weld zone with and without preheated FSW led to improved mechanical properties. The increased size of intermetallic phases and carbide particles due to induction preheating in I-FSW was most likely to be responsible for the enhancement of the weld strength. The hardness of the stir zone was increased from 250 HV to 370 HV, and the ultimate tensile strength of the I-FSW joint reaches 740 MPa, which was 98.8% of the base material. The results also revealed that preheating affected the process temperature results lowering the axial force and frictional heat, which improved the tool life.