Faculty Publications
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Item 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.Item Influence of microwave hybrid heating on the sliding wear behaviour of HVOF sprayed CoMoCrSi coating(Institute of Physics Publishing helen.craven@iop.org, 2018) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.CoMoCrSi superalloy powder (Tribaloy-T400) consists of intermetallic laves phase and primary eutectic phase of Co-rich solid solution. Processing of Tribaloy-T400 powder is carried out through high-energy ball milling (HEBM) technique to obtain a higher volume fraction of intermetallic laves phases. The feedstock is sprayed using high-velocity-oxy-fuel (HVOF) process on titanium grade-15 substrate. The coating microstructure is homogenized by microwave hybrid heating technique. Characterization of feedstock, as-sprayed and microwave fused coatings is done by using Scanning Electron Microscopy (SEM), Energy dispersive spectroscopy (EDS) and x-ray Diffraction (XRD). Porosity, surface roughness, microhardness, and bond strength are measured. Adhesive wear behavior of the coatings under the dry sliding condition is evaluated at an applied load of l0 and 20 N and temperature of 200, 400 and 600 °C Fused coating exhibit higher wear resistance than the as-sprayed coatings and substrate. The hard intermetallic laves phases which are amorphous (bulk metallic glass) in nature strengthen the coating at high temperatures. © 2018 IOP Publishing Ltd.Item 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.Item Microstructure and tribological behavior of flame sprayed and microwave fused CoMoCrSi/CoMoCrSi-Cr3C2 coatings(Institute of Physics Publishing helen.craven@iop.org, 2019) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.This present work deals with the investigation of dry sliding wear behavior of CoMoCrSi and CoMoCrSi-Cr3C2 depositing on titanium substrate through Flame spray process, subsequently fused by the microwave hybrid heating process. Prior to the deposition of the coating, CoMoCrSi powder is milled by using high energy ball milling (HEBM) process and later 30% of Cr3C2 powder is added. Microstructural features and phase analysis of milled powders, as-coated and microwave fused coatings are inspected by using SEM with EDS and XRD process respectively. The coatings before and after fusing are tested for microhardness and bond strength by using a Vickers microhardness and universal tensile machines respectively. Dry sliding wear behavior of coatings before and after fusing is conducted against alumina counter face at ambient and elevated temperatures, also normal load is varied. The wear mechanism of both coatings is examined by employing XRD, SEM-EDS techniques. The fused coatings exhibit lower friction and better wear resistance compared with as-deposited coatings. The detailed results of each test of their coatings are discussed in this paper. © 2018 IOP Publishing Ltd.Item Effect of microwave heating on microstructure and elevated temperature adhesive wear behavior of HVOF deposited CoMoCrSi-Cr3C2 coating(Elsevier B.V., 2019) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.This research reports the improvement of high-temperature sliding wear resistance of a grade 15 titanium alloy protected by an HVOF sprayed CoMoCrSi-Cr3C2 coating. The coatings have been tested in as-sprayed condition and after a post-deposition microwave heating step. The powder feedstock has been manufactured by high energy ball milling. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) equipped with the Energy Dispersive Spectroscopy (EDS) methods were used for coatings characterization. Surface roughness, microhardness, adhesion strength, and porosity of coatings were also measured. The wear test was conducted at an applied load of l0 N and 20 N with varying temperatures of 200 °C, 400 °C, and 600 °C under dry sliding conditions. Co3Mo2Si, Co7Mo6, Mo3Si, Co3Mo, and Co2Mo3 were the intermetallic laves phases generated in the CoMoCrSi feedstock during HEBM process. The microwave-fused coating exhibited metallurgical bonding, homogeneous structure, less porosity, and greater hardness as compared to as-sprayed coating. Microwave-treated coating revealed better wear property than an as-sprayed coating. This was mainly due to the intermetallic formation and metallurgical bonding in coatings. The fused coatings exhibit tribo-oxide layers during sliding action which was the main phenomenon of improving the wear resistance of the fused composite coatings. © 2019 Elsevier B.V.Item Development and Sliding Wear Behavior of Co-Mo-Cr-Si Cladding through Microwave Heating(Springer editorial@springerplus.com, 2019) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.The aim of the present study is to improve the sliding wear resistance of pure titanium grade-2 substrate by developing CoMoCrSi (Tribaloy T400) cladding on it by using microwave hybrid heating technique. The developed cladding is characterized by microstructural features, phase analysis, measurement of microhardness by employing a scanning electron microscope (SEM), X-ray diffraction (XRD) and Vickers microhardness. The cladding and substrate are subjected to sliding wear test against alumina counterpart at elevated temperatures under dry conditions using a pin on disc tribometer. The test is performed by varying normal load and temperatures, whereas sliding speed is maintained constant. The developed clad shown partial melting of CoMoCrSi powders and obtained sound metallurgical bonding with the substrate. The high specific energy of microwave diluted the substrate atoms into cladding region which forms Cr3C2, Co3Ti, and TiC, phases confirmed by phase analysis. The cladding obtained better porosity and microhardness are 1.5 ± 0.2% ?m and 760 ± 35 Hv respectively. The substrate exhibits low microhardness of 182 ± 25 Hv. The cladding exhibits 6 times of lower volume loss and 70.14% of less wear rate with respect to the substrate. The cladding experienced least coefficient of friction is 0.55 compared with the substrate. The worn surfaces of cladding and substrate are examined. The detailed mechanism of wear is discussed in this paper. © 2019, Springer Nature B.V.Item Microstructural and Tribological Resistance of Flame-Sprayed CoMoCrSi/WC-CrC-Ni and CoMoCrSi/WC-12Co Composite Coatings Remelted by Microwave Energy(Springer, 2020) Prasad, C.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.The hard facing composite coatings such as CoMoCrSi/30%WC-CrC-Ni and CoMoCrSi/30%WC-12Co are coated on grade-2 titanium substrate through Flame spray technique. Prior to deposition of coatings CoMoCrSi feedstock were processed using high energy ball milling to obtain intermetallic laves phases. The sprayed coatings are subjected to post-heat treatment through microwave energy to homogenize coating structure which reduces surface defects and to achieve metallurgical bonding. The as-sprayed and microwave treated coatings are examined for metallography analysis by using XRD, SEM–EDS and mechanical properties are estimated by using microhardness, universal tensile equipment. The high-temperature sliding wear tests are performed against alumina counterpart under dry conditions. The sliding wear test is conducted with normal loads of 10 N and 20 N at a sliding velocity of 1.5 m/s with a constant sliding distance of 3000 m. Microwave treated coatings obtained homogeneous structure and metallurgical bonding with improved hardness. Fused coatings revealed better wear resistance due to formation of oxides and fatigue spalling mechanism. © 2020, Springer Nature Switzerland AG.