Faculty Publications

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Joining of Inconel-625 alloy through microwave hybrid heating and its characterization
(Elsevier Ltd, 2015) Badiger, R.I.; Narendranath, S.; Srinath, M.S.
Joining of bulk metals using microwave energy is being explored as a new processing method in the era of high technology applications. The present work investigates the results of on-going project in which joining of Inconel-625 alloy has been effectively carried out through microwave hybrid heating. Characterization of the microwave developed joints is done through SEM, XRD, UTM and Vicker's microhardness tester. The microstructural analysis through scanning electron microscope exhibits a fully fused weld interface free from interfacial cracks. XRD study reveals the formation of carbides of Ni, Cr and Mo in the joint interface. The average Vicker's microhardness in the joint region observed was 360 ± 20 Hv. Assessment of tensile strength shows an ultimate tensile strength of 328 MPa with 9.04% elongation. Further the fractured joints are subjected to fractography study which possibly reveals a mixed mode fracture. © 2015 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Microstructure and mechanical properties of Inconel-625 welded joint developed through microwave hybrid heating
(SAGE Publications Ltd info@sagepub.co.uk, 2018) Badiger, R.I.; Narendranath, S.; Srinath, M.S.
Application of microwave energy for processing of bulk metals is effectively utilized to join Inconel-625 plates through hybrid heating technique using Inconel-625 powder as an interface filler material. Post welding characterization of microwave developed joints through X-ray diffraction shows the development of carbides of niobium and chromium as well as intermetallic phases along with the primary ?-phase face-centered cubic matrix. Microstructural examination reveals the formation of Laves phase along the grain boundaries in the fusion zone. Microwave-induced joints exhibit average microhardness of 245 ± 20 HV and 0.7% porosity in the fusion zone. Average ultimate tensile strength and flexural strength of the developed joints were estimated at 375 and 377 MPa respectively. Average impact toughness of microwave-induced joints is observed to be 18 J. © IMechE 2017.
Optimization of Process Parameters by Taguchi Grey Relational Analysis in Joining Inconel-625 Through Microwave Hybrid Heating
(Springer New York LLC barbara.b.bertram@gsk.com, 2019) Badiger, R.I.; Narendranath, S.; Srinath, M.S.
The quality of welded joints developed using microwave hybrid heating (MHH) technique is largely influenced by properties of the constituents employed in the process. This article investigates the influence of process parameters on tensile strength and flexural strength of Inconel-625 plates welded through MHH. Experiments were planned according to Taguchi L 16 orthogonal array by considering three factors: separator, susceptor and filler powder particle size. Ultimate tensile strength and flexural strength of the specimens welded at 600 and 900 W were chosen as response characteristics. Application of Taguchi-based GRA has been effectively used to optimize multi-performance characteristics of the process. ANOVA results indicate that size of interface filler powder is the most significant factor in determining the joint strength followed by separator and susceptor. Further to corroborate the optimal parameter setting for maximum strength values, metallurgical characterization of the specimens is carried out through XRD and SEM. Specimens processed at 600 W exhibited superior properties compared to their counterparts developed at 900 W. © 2018, Springer Science+Business Media, LLC, part of Springer Nature and ASM International.
Characterization of Inconel 625-SS 304 Weldments Developed by Selective Microwave Hybrid Joining Technique for Promising Applications
(Springer, 2024) Kamble, D.L.; Sahu, R.K.; Narendranath, S.
Production of dissimilar weldments using microwave hybrid heating is currently gaining immense impetus in the field of advanced welding. This is because such heat source could provide benefits like cost-effectiveness, rapid, volumetric, uniform and selective heating, and efficient throughput which would be significant to various industries. Till-date researchers have carried out joining of dissimilar general purpose engineering materials using microwave hybrid heat source. But attention has not been paid on the joining and characterization of dissimilar exotic-general purpose materials using the aforementioned heat source and the promising applications of the weldments. Therefore, the present article is focused on the joining of dissimilar materials- Inconel 625 and SS 304 alloys using selective microwave hybrid joining (SMHJ) technique. In SMHJ, nickel-based powder is used as a filler material, Silicon carbide (SiC) block and SiC powder are used as susceptor to increase the initial temperature. The developed weldments through SMHJ are characterized using various physico-chemical diagnostic methods. The results reveal the average micro-hardness of joint was found to be 303 ± 17 HV owing to the presence of various carbides and nitrides phase like NbC, Cr23C6, Cr2Ni3, Ni8Nb, and Fe3Ni2 in the joint zone which is evident from XRD. The average UTS of the joints found to be 448.6 MPa with an elongation of 10.93% and flexural strength observed to be 435 MPa. Further, fractography study reveals, the joint regions have mixed mode of failure. The failure was attributed to the existence of secondary phases in the joint zone. © ASM International 2023.

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