Faculty Publications
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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 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 Comparison of Microstructural and Sliding Wear Resistance of HVOF Coated and Microwave Treated CoMoCrSi-WC + CrC + Ni and CoMoCrSi-WC + 12Co Composite Coatings Deposited on Titanium Substrate(Springer Science and Business Media B.V. editorial@springerplus.com, 2020) Prasad, C.D.; Joladarashi, S.; Ramesh, M.R.; Srinath, M.S.; Channabasappa, B.H.CoMoCrSi-WC + CrC + Ni and CoMoCrSi-WC + 12Co composite coatings are coated on titanium substrate by high velocity oxygen fuel method (HVOF). Prior to spraying, CoMoCrSi feedstock are processed through high energy ball milling (HEBM) in order improve the intermetallic laves phases and to reduce its particle size. The processed feedstock exhibits amorphous nature by improving laves phases and particle size of 60.12 ?m. Microwave heating energy is utilized as post heat treatment technique to improve the mechanical and metallurgical properties of as-sprayed coatings. Fused coatings reveals better properties in terms of surface roughness, porosity, microhardness and adhesion strength compared to as-sprayed coatings. Metallurgical bonding is observed in case of fused coatings due to diffusion of substrate elements. Frictional and wear behaviors have been investigated by a pin on disc apparatus at temperatures of 200 °C, 400 °C, and 600 °C under normal loads of 10 N and 20 N. Both wear trace and friction coefficients of the fused coatings are smaller than as-sprayed coatings and substrate at all test temperatures. The wear traces of fused coatings decreased with increasing the surface temperature due to the lubricant effect of cobalt oxides formed on the sliding surface. As a result, cobalt based cermet coatings are highly recommended as a durability improvement coating for the protection of sliding surface, such as high speed spindle. © 2020, 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.Item Effect of temperature on wear and friction performance of WC-Co and Cr3C2 reinforced with 17-4PH Fe-based composite coatings(Springer Science and Business Media Deutschland GmbH, 2024) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.; Rahman, M.R.Surface protection is crucial in industrial equipment and tools to prevent wear and friction in harsh environments, particularly at high temperatures, where anti-friction coatings are essential for optimal performance. The present research investigates the tribological properties of high-velocity oxy-fuel sprayed coatings of 17-4PH stainless steel reinforced with tungsten carbide and chromium carbide powders. The coatings are deposited onto a maraging steel substrate. A dry sliding wear test was performed using an alumina ball as a counter body under various test temperatures (25 °C, 300 °C, and 600 °C) and loads (10 N and 30 N). The coating is characterized by employing SEM, XRD, micro-hardness tester, particle analyzer, and bond strength tester, and the mechanism of wear reduction was discussed. The post-wear analysis was carried out on the wear track using SEM/EDS and 3D non-contact optical profilometers. The micro-hardness and bond strength of both (17-4PH-30%WC-Co and 17-4PH-30%Cr3C2) coatings are compared. The test results revealed that at all temperatures and loads, 17-4PH-30%WC-Co coating shows better wear resistance and lower friction coefficient than the 17-4PH-30%Cr3C2 coating. The significant influence of the tribo-oxide layer at high temperatures, which contributed to decreasing wear rate and coefficient of friction, was premeditated. © 2023, International Institute of Welding.Item Microstructure, Mechanical Properties, and Tribological Properties of Fe-Based Composite Coatings Reinforced with WC-Co and Cr3C2(Springer, 2025) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.; Rahman, M.R.Fe-based (stainless steel 316L) coatings are widely employed in the aerospace, chemical processing, petrochemical, and marine industries owing to their low and stable price, excellent corrosion resistance, and durability. However, at elevated temperatures, their performance is limited due to wear. Thus, the current investigation incorporates tungsten carbide (WC-Co) and chromium carbide (Cr3C2) into the Fe-based coating to enhance its wear resistance at high temperatures. SS316L reinforced by 30% of WC-Co and Cr3C2 by mechanical mixture, then sprayed using high-velocity oxy fuel spraying method. Coating characteristics, such as microstructures and phase analysis, were measured using FESEM/EDS and XRD. Coating density, microhardness, and bond strength were examined by water immersion, Vickers indentation, and ASTM C-633 methods, respectively. A ball-on-disk tribometer was employed to conduct wear examination at various temperatures (25, 300, and 600 °C) and loads (10 and 30 N) against the alumina counter body. The wear rate and friction coefficient of SS316L-30%WC-Co decrease from 25 to 600 °C, while the wear rate of SS316L-30%Cr3C2 increases with temperature up to 300 °C and then decreases at 600 °C. The oxide phase adheres strongly to underlying surfaces forming a protective layer (Cr2O3, NiWO4, Fe2O3, and NiMO4), changing the mode of wear mechanism. At higher temperatures and loads, the coating exhibited oxidation modified adhesive wear, and coatings provide excellent wear resistance along with reduction in friction. This research provides a novel approach for future standardization and evaluation of coatings on metal alloys for industrial applications. © ASM International 2024.Item Surface enhancement of SS304 for high-temperature wear resistance using laser cladded Mo-alloyed stellite 6 coatings(Elsevier B.V., 2025) Aprameya, C.R.; Joladarashi, S.; Ramesh, M.R.Severe wear often limits the high-temperature durability of SS304 components, necessitating the development of surface-engineered solutions. In this investigation, Mo-reinforced Stellite 6 claddings were developed using Laser Directed Energy Deposition (L-DED) to provide enhanced surface protection. Claddings with (3, 6, and 9 wt%) Mo reinforcement enhanced hardness by 2.9, 3.1, and 3.3 times, respectively, compared to the SS304 substrate. This improvement is attributed to Mo-induced solid solution strengthening and the formation of hard intermetallic phases. Dry sliding wear tests were conducted at RT and 600 °C under (10 and 20 N) loads. Wear characterisation of the clads was performed using OM, XRD, FE-SEM, EDX, and Raman spectroscopy. At RT, claddings primarily exhibited abrasive wear with minor plastic deformation. However, at 600 °C, the wear mechanism evolved into a combination of severe adhesive, oxidative, abrasive, and plastic deformation modes, with oxidative wear governing the tribological behavior. Stellite 6 with 9 wt% Mo clads exhibited better tribological performance than the other two variants, owing to the development of oxide glaze layers of Cr2O3, NiO, CoO2, and Co3O4. Enhanced performance of the claddings is attributed to solid solution strengthening, Cr-rich carbide formation, increased dislocation density, and the L-DED technology enabling refined microstructure and strong metallurgical bonding. These findings highlight the potential for further advancements in Mo-reinforced Stellite 6 L-DED claddings for high-temperature wear applications. © 2025 Elsevier B.V.