Faculty Publications
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Item HVOF sprayed Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings: Microstructure, microhardness and oxidation behaviour(Elsevier Ltd, 2018) Reddy, N.C.; Kumar, B.S.A.; Reddappa, H.N.; Ramesh, M.R.; Koppad, P.G.; Kord, S.This paper reports the development of Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings on AISI 420 stainless steel (MDN-420) and titanium alloy ASTM B265 (Ti-15) by HVOF technique. Microstructure, microhardness and high temperature oxidation behaviour of coatings were investigated. Microstructure of coatings was dense and displayed layers depicting lamellar structure. The microhardness of coatings was significantly higher than that of substrate owing to higher density and cohesive strength between individual splats of coating materials. Cyclic oxidation studies conducted on Ni3Ti and Ni3Ti+(Cr3C2+20NiCr) coatings showed oxide scale was composed of various oxides like NiO, NiCr2O4 and Cr2O3 phases. The formation of compact and protective NiO phase in case of Ni3Ti coatings; NiO and Cr2O3 phases in Ni3Ti+(Cr3C2+20NiCr) coatings stabilised the weight gain exhibited slow oxidation rate at higher temperatures. © 2017 Elsevier B.V.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 Effect of cutting parameters on tool wear, cutting force and surface roughness in machining of MDN431 alloy using Al and Fe coated tools(Institute of Physics Publishing helen.craven@iop.org, 2019) V Badiger, P.V.; Desai, V.; Ramesh, M.R.; Prajwala, B.K.; Raveendra, K.Thin solid films are used in cutting tools in order to improve its performance, reduce tool wear and improve tool life. Cathodic arc evaporation is the state of art PVD technique widely accepted in industries for the development of thin solid films. The turning cutting tool inserts are coated with AlCN/AlC and FeCrN monolayer thin solid films using cathodic arc evaporation technique. Quality characteristics of thin films are estimated using Calo and VDI3198 tests. Thickness of the coatings are found to be 1.430 and 1.475 ?m for AlCN/AlC and FeCrN coatings respectively and adhesion quality of HF1 is attained. Performance of the thin solid films are evaluated in machining MDN431 steel with range of cutting speed (59-118 m min-1), feed rate (0.062-0.125 mm/rev) and depth of cut (0.2-0.4 mm). Experiments are performed based on full factorial design and regression analysis. Optimization of the process parameters is carried out using combined techniques of desirability and Particle swarm optimisation (PSO). The objective of the study is to establish correlation between machining parameters with cutting force, tool wear and surface roughness. Optimal process parameter for least cutting force and surface roughness are obtained for coatings. ANN has been adopted to improve the coefficient of determination (CoD) and capability of predictive regression models. ANN trained model and mathematical regression models are adequate to predicted the responses, which follows the experimental data with minimum absolute error. The AlCN/AlC coatings exhibited lower cutting forces and surface roughness than FeCrN coated tools. Tool wear was reduced by 3.62 times in AlCN/AlC and 1.63 times in FeCrN coated tools compared to uncoated tool which is due to increased hardness and elastic modulus of the coating. © 2018 IOP Publishing Ltd.Item Evaluation of Wear Behaviour of Metal Injection Moulded Nickel Based Metal Matrix Composite(Springer Netherlands rbk@louisiana.edu, 2019) Veeresh Nayak, V.N.; Ramesh, M.R.; Desai, V.; Kumar Samanta, S.K.Metal injection moulding (MIM) is a near-net shape manufacturing technology for producing intricate parts, cost-effectively. MIM comprises combined techniques of plastic injection moulding and powder metallurgy. The present study focused on the development of the binder and fabrication of defect free MIM component. A wax-based binder system consisting of paraffin wax (PW), low density polyethylene (LDPE), polyethylene glycol (PEG-600) and stearic acid was established for MIM of NiCrSiB (70% Wt.) + Cr3C2-NiCr (30% Wt.) nickel based metal matrix composite (NMMC) powder. The feedstock was characterised through rheological properties at different temperatures. Injection temperature was determined from the rheological investigation of the feedstock having the 56% powder loading and 44% binder by volume. Sintering process was carried out with the temperature cycle in the range of 1250–1300 ?C under hydrogen purged atmosphere. The MIM components showed good and acceptable shrinkage in linear dimensions. The mechanical properties and wear behaviour of NMMC was studied using a pin-on-disc apparatus with alumina disc.Tests were performed under dry sliding conditions at room temperature and elevated temperatures of 200 and 400 ?C. Results shows that wear rate is maximum at 400 ?C for 40 N and lowest at room temperature for 10 N. Further wear mechanism was analysed using scanning electron microscope (SEM). © 2018, Springer Science+Business Media B.V., part of Springer Nature.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 Development of Self-lubricating Nickel Based Composite Clad using Microwave Heating in Improving Resistance to Wear at Elevated Temperatures(Korean Institute of Metals and Materials, 2022) Gudala, S.; Ramesh, M.R.; Srinath, M.S.This paper reports on a study of the high-temperature tribological performance of self-lubricating nickel-based composite clad. A porous and crack free clad containing matrix, reinforcement, and lubricant phase is developed on titanium 31 alloy using microwave irradiation. The microstructure of both NiCrSiB/WC and NiCrSiB/WC/Ag/BaF2 clad revealed very good metallurgical bonding with the substrate. The average microhardness of NiCrSiB/WC and NiCrSiB/WC/Ag/BaF2 clad is 710.58 HV and 650.25 HV respectively, is comparatively higher than the titanium 31 substrate (320 HV). The addition of Ag and BaF2 solid lubricants in the clad endowing clad to operate at a broad temperature range. Compared with the NiCrSiB/WC clad, solid lubricant encapsulate clad has shown very low friction coefficient and wear rates. The sliding wear characteristics of the clad were investigated by varying load and temperatures. The results revealed that oxide phases (NiO and Cr3O) and lubricant phases (Ag and BaWO4) formed at low and high temperatures are adequate to reduce delamination and material loss. Graphical abstract: [Figure not available: see fulltext.] © 2021, The Korean Institute of Metals and Materials.Item Effect of Microwave Hybrid Heating on High-Temperature Adhesive Wear Behavior of High-Velocity Oxygen Fuel-Sprayed WC-CrC-Ni and WC-Co/NiCrFeSiB Coatings(Springer, 2023) Medabalimi, S.; Ananthu, M.R.; Gudala, S.; Ramesh, M.R.HVOF-processed coatings are chemically inhomogeneous and are not metallurgically bonded to the substrate. As a result, components coated with HVOF experience considerable material degradation during sliding wear. Microwave hybrid heating (MHH) is a novel surface modification technique for modifying the as-sprayed properties of the coating. Hence, this paper investigates and compares the wear and frictional behavior of HVOF as-sprayed coatings against MHH samples of WC-CrC-Ni and WC-Co/NiCrFeSiB coatings at elevated temperatures. MHH had a significant impact on wear rate and coefficient of friction by optimizing the porosity, integrated oxide phases and intersplat cohesion strength of the coatings. A modified domestic oven was used to perform MHH on HVOF-coated samples for 5 min at 1200 °C. Wear tests were performed using a pin-on-disk tribometer from room temperature to 200, 400, and 600 °C with Al2O3 disk as a counterface. SEM/EDS and XRD were utilized to examine the microstructural characterization of the coatings and substrate. Both the coatings showed higher wear resistance than the substrate at all temperatures. The WC-Co/NiCrFeSiB coating produced an oxide layer on the worn surfaces and integrated WC, CoWO4, and Fe2SiO4 splats, enhancing wear resistance. The MHH WC-CrC-Ni coating formed Cr2O3 and NiWO4 phases on the worn surfaces, increasing the intersplat cohesion strength between matrix and carbide splats, lowering the overall wear rate. After MHH, the wear rate of a substrate and WC-CrC-Ni coating was 3.5 and 1.12 times more at room temperature and 8.07 and 2.92 times more at 600 °C than WC-Co/NiCrFeSiB coating. © 2022, ASM International.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.