EFFECT OF DIFFERENT MIG WELDING MODES ON HARD-FACING OF INCONEL 718 ON 321 STAINLESS STEEL

In this study, the metal inert gas (MIG) welding process is taken to deposit the Inconel 718 material on 321 stainless steel. Various modes like the DC, DC-pulsed, and DC-wave-pulsed modes in MIG welding are used for depositing Inconel 718. The primary parameters such as the welding current (90-120 A) and speed (150-350 mm/min) are varied within the range for making the layer deposition over 321 stainless steel. After performing the layer deposition, the dilution, contact angle, and peak temperature are analyzed to find the optimal MIG welding mode. From the macrograph, very low dilution (7.44%) is identified for the DC mode. The most inferior contact angle (theta) of 49 degrees was measured for the DC-wave-pulsed mode. The simulation work predicted a peak temperature of 2800 degrees C for the DC mode. Considerable microstructure changes have occurred at the weld deposition (dendritic structure) and HAZ (grain coarsening) for all the three modes. At the top, interface, and HAZ locations, the microhardness obtained from the DC-pulsed mode is in between those of the DC and DC-wave-pulsed modes. Overall, the DC-pulsed mode is qualified for making the metal deposition and further work. For 50% overlap, defect-free 2-mm-thick layer depositions are made on the 321 stainless steel surfaces.