Please use this identifier to cite or link to this item: http://dspace.dtu.ac.in:8080/jspui/handle/repository/21299
Title: EXPERIMENTAL INVESTIGATION ON WIRE ARC ADDITIVE MANUFACTURING OF DISSIMILAR INCONEL AND STAINLESS-STEEL ALLOYS USING COLD METAL TRANSFER WELDING
Authors: MEENA, RAJENDRA PRASAD
Keywords: WIRE ARC ADDITIVE MANUFACTURING
DISSIMILAR INCONEL
STAINLESS-STEEL ALLOYS
COLD METAL TRANSFER (CMT)
TRANSFER WELDING
Issue Date: Aug-2024
Series/Report no.: TD-7689;
Abstract: Wire Arc Additive Manufacturing (WAAM) has grown in popularity due to the many practical uses of additive manufacturing (AM), most notably in the fabrication of large metal structures. Cold Metal Transfer (CMT) is an advanced gas metal arc welding (GMAW) technology with minimal heat input, producing clean surfaces and little spatter. Inconel 718 and SDSS 2507 1.2 mm diameter filler wire were selected in this research. Stainless steel 304 was selected as substrate material with 200mm × 50mm × 5 mm dimensions. This research work outlines techniques for optimizing input parameters for the welding process, such as welding current, speed, and gas flow rate in relation to weld bead geometry and Dilution, using Response Surface Methodology (RSM). In the WAAM process, single-weld bead stability and quality play a prominent role in the final manufactured part's quality and shape. A single-bead geometry model was initially established using RSM, and experiments were carried out using a central composite design of experiments for depositing for Super Duplex Stainless Steel (SDSS) 2507 and Inconel (IN) 718 in WAAM. The design factors and responses were analysed using multiple regression equations, and the validity of the resulting regression equations was evaluated using ANOVA. The optimum values for weld bead width and bead height were 6.57 mm and 3.43 mm, respectively; the minimum dilution observed was 31.30 % for SDSS 2507. The predicted optimal input parameters were 190.46A current, 8.94 mm/s welding speed, and 15 l/min shielding gas flow rate for SDSS 2507. The results indicated that current was the most influential factor in determining the multiple responses, followed by welding speed and gas flow rate. The microstructures of SDSS 2507 were characterized by optical microscopy, and results indicated that the microstructure of the weld bead region consisted of ferrite and austenite. The WAAM wall is fabricated with optimal parameters. The optimum parameters for IN 718 are a welding current of 210 A, 6.91 mm/min speed, and a gas flow rate of 25 l/min. Microstructure characterization revealed small grains in the top layer, equiaxed in the middle v and side regions, and columnar in the lower region for IN 718. The microhardness of the CMT based WAAM fabricated samples was also evaluated. The current study involved manufacturing a dissimilar alloy wall using SDSS 2507 and IN718 through the CMT-based WAAM. The microstructural characteristics reveal a discontinuity in the dendritic structure and an abrupt transition at the Interface (IF). A confirmation of the fine disintegration of elements at the Interface (IF) was found by energy-dispersive X-ray spectroscopy (EDS), and no significant change in composition was noted. Microstructure investigation indicates build-direction epitaxial grain growth and deposited layer non equilibrium microstructures. SDSS 2507's SEM microscopy displays austenite and ferrite in the lower part, and IN 718's shows columnar and cellular crystals with white laves phases, which form when Nb and Mo elements segregate. The interface (IF) samples at a 90° angle in the SDSS 2507L region experienced failure due to a lower Ultimate Tensile Strength (UTS) than IN718. The fracture mode observed was ductile. The microhardness measurements illustrate the progressive variation in building direction hardness. Ultrasonic vibration has been used in melting material solidification procedures to enhance part performance. This research proposes using ultrasonic vibration (UV) assisted CMT-based WAAM deposition to potentially manufacture dissimilar SDSS 2507-IN718 parts to decrease fabrication defects. Experimental studies are carried out to examine the impact of ultrasonic vibration on the microstructures and mechanical properties of parts manufactured using CMT. The findings demonstrated that the application of ultrasonic vibration improved the microstructure, leading to an average grain size of 4.59 um. In addition, it effectively fragmented the harmful Laves precipitated phase into small particles that were evenly distributed. Consequently, the yield strength, UTS, and microhardness of the fabricated dissimilar SDSS 2507-IN718 parts were improved.
URI: http://dspace.dtu.ac.in:8080/jspui/handle/repository/21299
Appears in Collections:Ph.D. Mechanical Engineering

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