Faculty Publications
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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 High-temperature wear and frictional behavior of partially oxidized Al with NiCr composite coating(Institute of Physics Publishing helen.craven@iop.org, 2019) Medabalimi, S.R.; Ramesh, M.R.; Kadoli, R.The influence of composite coating in improving wear and frictional behavior from room temperature to 600 °C was investigated. Partially oxidized Al powder was prepared with a flame spray process by spraying pure Al powder into distilled water. The composite powder is the mixture of 30 weight percent of partially oxidized Al and 70 weight percent of NiCr alloy powder. The composite powder was subsequently coated on MDN321 steel by air plasma spray process. The composite coatings are characterized with respect to adhesion strength, porosity, micro-hardness, and density. Wear and frictional behavior of coatings are evaluated under disc speed of 1 and 2 m s-1, loads of 10, 20 and 30 N and 3000 m sliding distance. The test results indicated that at room temperature, frictional heat generated due to applied load produce three-body abrasion at the interface caused to increase the wear and friction in the coating. The oxide film formed at high temperature due to plastic deformation avoids surface degradation at the interface and reduce the wear and friction. The worn surfaces at 600 °C consist phases of ?-Al2O3, NiO, and Cr3O. These phases are contributing to improving the wear resistance of the coating more than 4-times compared to uncoated steels under varying load and sliding velocities. The coefficient of friction reduced with increase in temperature due to generated oxides act as lubricants at the interface. © 2019 IOP Publishing Ltd.Item Solid Particle Erosion Behavior of Partially Oxidized Al with NiCr Composite Coating at Elevated Temperature(Springer, 2021) Subba Rao, M.; Ramesh, M.R.; Kadoli, R.The composite coating was developed and investigated the solid particle erosion performance at elevated temperature by varying impact angles. Al2O3 erodent of grit size 50 µm was used in air-jet erosion tester to investigate the resistance to erosion at RT, 200, 400, 600, and 800 °C by varying 30, 45, 60, 75, and 90° impact angles. The composite coating was deposited on MDN321 steel by plasma spray process with feedstock of “30 weight percent of partially oxidized Al powder and 70 wt.% of NiCr alloy powder.” The composite coating was characterized by bond strength, porosity, micro-hardness, and density. Volumetric erosion loss concerning temperature and impact angle was studied using SEM, EDAX, and XRD analysis. Non-contact three-dimensional optical profilometer was used to quantify the volumetric erosion loss. MDN321 steel showed better erosion resistance than composite coating at all the temperatures. Due to the formation of stable oxides at 800 °C the erosion resistance of the coating was improved. © 2021, ASM International.Item Cyclic Oxidation and Hot-Corrosion Behavior of HVOF-Sprayed NiCrAl Coating on Industrial Boiler Tube Steels(Springer, 2024) Ramesh, M.R.; Medabalimi, S.; Rupanagudi, R.S.; Prasad, C.D.; Sollapur, S.B.At high temperatures, coatings provide a protective scale development on surfaces to maintain long-term stability. In the current study, ASTM-SA210-Grade A1 (GrA1) and ASTM-SA213-T-11 (T11) boiler tube steels were coated with NiCrAl alloy with high-velocity oxy-fuel (HVOF) to prevent oxidation and hot corrosion. For hot corrosion and oxidation, 50 cycles at 900°C were taken into account. Additionally, tests of hot-corrosion behavior were conducted in an atmosphere containing molten salt (Na2SO4-60%V2O5), while tests of oxidation behavior were conducted in static air. The kinetics of oxidation were calculated using the thermogravimetric method. Using XRD, EPMA, and SEM/EDAX methods, the produced oxide scales were characterized. The oxidation rate of NiCrAl-coated steels was found to be lower than that of uncoated steels. The coated steels subjected to oxidation in air exhibit slow scale growth kinetics and oxides of α-Al2O3 and Cr2O3 on the outermost surface, while accelerated oxidation caused by the molten salt exhibits metastable Al2O3. Along the nickel-rich splat boundary, Cr and Al were formed a preferential oxidation, which prevents other oxygen from entering the coating via pores and voids, resulting in steady-state oxidation. © The Minerals, Metals & Materials Society 2024.Item An investigation on tribological performance in HVOF sprayed of Amdry1371 and Amdry 1371/WC-Co coatings on Ti6Al4V(Elsevier B.V., 2024) Behera, N.; Srihari, M.; Sharma, Y.K.; Ramesh, M.R.This study investigates the effect of 30 wt% WC addition into Mo-based coating on the microstructure and dry sliding wear performance at elevated temperatures. A ball-on disk tribometer assessed coating wear and friction behavior at room temperature (RT), 300, and 600 °C with loads of 10 and 20 N. The wear rate and mechanism were assessed using SEM-EDX and an optical profilometer. The coating characteristics included density, porosity, surface roughness, microstructure, and microhardness. The bond strength of Amdry1371 and Amdry1371/30%WC-Co coatings is analyzed using the scratch test. During the scratch test, both coatings show cohesive failure at 30-50 N and cohesive along with adhesive failure at 70 N loads. Compared to Amdry1371 coating, Amdry1371/30%WC-Co coating has greater microhardness and bond strength. The wear rate and friction coefficients of Amdry1371 and Amdry1371/30%WC-Co coatings increase with temperatures up to 300 °C and decrease at 600 °C. Wear debris is generated when contact surfaces fracture under the applied load, acting as a third body in the sliding process. This phenomenon, observable from room temperature to 300 °C, increases wear rate and friction coefficients. Protective oxide phases formed on worn surfaces like MoO3, NiMO4, CoWO4, Cr3O8, and WO3 film at 600 °C. This glaze layer is present on worn surfaces, significantly reducing friction coefficients and the wear rate of coatings. Amdry1371/30%WC-Co coating exhibits superior wear resistance and lower friction coefficients than Amdry1371 coating due to MoO3 and WO3. At RT, the dominant abrasive wear mechanism shifts to oxidative wear at 600 °C for both coatings. © 2024 Elsevier B.V.Item A microstructural study and high-temperature oxidation behaviour of plasma sprayed NiCrAlY based composite coatings(Elsevier B.V., 2025) Hebbale, A.M.; Ramesh, M.R.; Petr?, J.; Chandramouli, T.V.; Srinath, M.S.; Shetty, R.K.In this study, the development and performance evaluation of plasma sprayed NiCrAlY based coatings, such as NiCrAlY, NiCrAlY + Al?O? and NiCrAlY + YSZ on T91 steel substrates for high temperature applications is carried out. Microstructural features, phase composition and oxidation resistance under cyclic oxidation at 800 °C of the coatings were characterized. Analysis of the XRD confirmed the formation of protective phases such as Cr?O?, Ni?Al and NiAl, and the improvement observed in the coating's performance was due to the addition of Al?O? and YSZ. Oxidation resistance was improved for the NiCrAlY + Al?O? coating through the formation of a dense Al?O? oxide layer, but the NiCrAlY + YSZ coating was superior in terms of thermal stability and spallation resistance, because YSZ has low thermal conductivity and high thermal shock resistance. Composite coatings showed improved cyclic oxidation behavior and microstructural analysis revealed reduced porosity and enhanced integrity. The results demonstrate that the addition of Al?O? and YSZ in the NiCrAlY coatings leads to capability of tailoring NiCrAlY–based coatings for high temperature industrial applications with improved durability and oxidation protection. © 2025 The Author(s)Item Tribological characteristics of HVOF sprayed Fe-based composite coatings at elevated temperatures(SAGE Publications Ltd, 2025) T V, C.; Joladarashi, S.; Ramesh, M.R.This study evaluates the tribological performance of Fe-based composite coatings for aerospace and automotive applications, focusing on wear resistance at elevated temperatures. The coatings, comprising 15% WC-Co and Cr3C2 in an SS316L matrix, were deposited onto maraging steel via HVOF spraying. Microstructural analysis and adhesive strength testing confirmed strong particle bonding, with the coatings achieving a hardness of 711 ± 14?HV. Dry sliding wear behaviour was assessed using a ball-on-disc tribometer with alumina as the counterface under 10?N and 30?N loads at 25?°C, 300?°C, and 600?°C. Results indicated a decrease in the coefficient of friction and specific wear rate with increasing load and temperature. At 600?°C, wear rates were reduced by ?97.56% (10?N) and ?97.12% (30?N) than uncoated steel. Abrasive wear dominated at room temperature, while adhesive and oxidative wear mechanisms emerged at 600?°C, attributed to protective glaze layer formation. © The Author(s) 2025.Item Effect of wt% molybdenum content on the tribological properties of WC-10Ni/Mo coatings at elevated temperatures(Elsevier Inc., 2025) Behera, N.; Ravish, M.; Kumar, P.; Ramesh, M.R.Maraging Steel is widely used in automotive and aerospace components; however, it should not be exposed to high temperatures because of its poor wear and friction characteristics. This study investigates the effect of temperature on WC-10Ni coatings with the addition of molybdenum from 10 to 30 wt% applied on a Maraging Steel using a high-velocity oxy-fuel technique. A ball-on-disc tribometer with Al2O3 as a counterpart was used to evaluate the wear and friction properties of the coatings at RT, 300, and 600 °C and 10 and 30 N of load. The coating characterization was carried out using SEM, XRD, density measurements, microhardness testing, porosity evaluations, surface roughness measurements, and bond strength assessment. The wear rate and mechanism are ascertained using a 3D profilometer and SEM-EDS. The outcomes demonstrate that the WC-Ni/10 %Mo coating has greater bond strength and microhardness than the WC-Ni/20 %Mo and WC-Ni/30 %Mo coatings. The wear rate of the substrate increases with increasing temperature. The WC-Ni/20 %Mo and WC-Ni/30 %Mo coatings showed increasing wear rates until 300 °C, decreasing at 600 °C. At 600 °C, coatings included oxide phases such as NiWO4, WO3, MoO3, and NiMoO4, which helped lower the wear rate and coefficient of friction. Moreover, when temperatures rose, the coefficient of friction for all three coatings and substrates dropped. At all loads and temperatures, the WC-Ni/10 %Mo coating was well performed compared to WC-Ni/20 %Mo, WC-Ni/30 %Mo coating, and substrate regarding coefficient of friction and wear resistance. In particular, fatigue and abrasive wear predominated at RT, but oxidative, adhesive, and abrasive wear were all seen at 600 °C. The volumetric loss of the ball for WC-Ni/10 %Mo is higher than that of WC-Ni/20 %Mo and WC-Ni/30 %Mo coatings due to the higher hardness of WC-Ni/10 %Mo coating. © 2025