Experimental investigations on Inconel 718 hard-faced layer deposited over SS304 using cold metal transfer

Abstract

This study used the cold metal transfer (CMT) process to deposit Inconel 718 (IN718) as a hard-facing layer on the Base Substrate (BS) of 304 stainless steel (SS304). Different profiles like straight/stringer and sinewave weaving techniques are adopted to deposit the hard-faced layers. For the above profile, IN718 is deposited as a single-track and 30 % overlap to study the impact of heat input on the base substrate. Through the Bead on Plate (BoP) trials, optimal parameters of welding current (175 A), speed (15 cm/min), and wire feed rate (7 m/min) is identified. Sinewave beads (single track) explored a minimum dilution of 13.46 % compared to all the combinations. The sinewave distributed the heat uniformly compared to the straight/stringer profile. At the top surface, fine grains with an equiaxed structure are identified. Annealed twins are present at the base substrate, and elongated columnar grains near the interface are identified through EBSD. The sinewave with 30 % overlapped layers exhibited a maximum hardness of 274.4 HV0.5 at the Hard Face Zone (HFZ), whereas the base substrate hardness was 204 HV0.5. Further, the hard-faced samples achieve an ultimate strength of 750 Mpa through the tensile test. The micro-voids, dimples, and riverine structure observed from fractured surfaces witnessed the ductile fracture. The segregation of Niobium is scattered at the inter-dendritic region. The SEM-EDX results confirm the existence of Niobium, Nickel, and Molybdenum elements.