Faculty Publications
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Item Influence of Impact Angle and Temperature on Solid Particle Erosion Behavior of Titanium-31(Springer Nature, 2024) Behera, N.; Chandramouli, T.V.; Aprameya, C.R.; Ramesh, M.R.The present work shows the effects of impact angles and temperatures on volumetric erosion loss of titanium-31 alloy. An erosion tester was used to perform the erosion tests with temperatures (200, 400, 600, and 800 °C) and impact angles (30°, 60°, and 90°). The alumina particles (Al2O3) are used as an erodent particle with an average particle size of 50 μm. The microhardness, porosity, and surface roughness of titanium-31 alloy are evalu-ated. SEM/EDS and XRD were used to analyze tita-nium-31 alloy eroded samples. The weight loss method and 3D profilometer determined the volumetric erosion loss. The microhardness of titanium-31 alloy is found to be 337 ± 15HV0.3. The Volumetric erosion loss of tita-nium-31 alloy increased with increasing temperatures from 200 to 800 °C, whereas decreased with increasing impact angle from 30° to 90° for all temperatures. The volumetric erosion loss is higher at a 30° impact angle and lower at a 90° impact angle for all temperatures. As a result, titanium-31 alloy shows the ductile erosion mode for all temperatures. The volumetric erosion loss at 30° impact angles is due to micro-cutting and plough-ing, whereas deep crater, groove, and raised lips are for 90° impact angles. The results of volumetric erosion loss obtained by the weight loss method exhibit a good cor-relation with a 3D optical profilometer. © The Author(s), under exclusive license to Springer Nature Switzerland AG 2024.Item Tribological Performance of Fe-Based Composite Coatings Under Elevated Temperature Conditions(Springer, 2025) Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.The present study investigated the tribological performance of Fe-based coatings reinforced with carbides onto a maraging steel substrate using the HVOF spray technique. These materials are widely used in manufacturing various components in the aerospace and energy sectors. Commercially available SS316L and 17-4PH are reinforced with WC–Co feedstock powders to deposit these composite coatings on maraging steel substrate. The dry sliding wear tests were conducted using the ball-on-disc tribometer at varying temperatures (25 and 300 °C) with 10 N normal load using an alumina ball (Al2O3) as the counter body. The study includes micro-hardness, porosity, density, bond strength, and surface roughness of the coatings. The samples subjected to wear testing were analyzed using SEM/EDS and XRD techniques, and the wear scar volume was measured using a 3D profilometer to calculate the volume metric loss. The wear rate of SS316L30%WC–Co is 64.46% lower than that of 17-4PH30%WC–Co at room temperature and 67.33% lower at 300 °C under a load of 10 N. At room temperature, the worn surface exhibited abrasive wear, while at 300 °C, adhesive wear and oxidative wear were observed owing to the formation of protective layers. Therefore, SS316L-30%WC–Co demonstrates superior wear resistance compared to 17-4PH-30%WC–Co and offers enhanced mechanical strength, particularly in challenging environments. The deposition of these coatings effectively protects the maraging steel substrate. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item DRY SLIDING WEAR RESISTANCE OF HVOF SPRAYED IRON-BASED COMPOSITE COATINGS ALLOYED WITH CARBIDES ACROSS VARIOUS TEMPERATURES(American Society of Mechanical Engineers (ASME), 2025) Aprameya, C.R.; Chandramouli, T.V.; Joladarashi, S.; Ramesh, M.R.Maraging steel, widely used in aerospace applications for its remarkable strength and toughness, often faces challenges related to surface wear resistance in high-stress environments. This study investigates the dry sliding wear performance of Fe-based coatings allied with carbides, applied onto maraging 250-grade steel using the High-Velocity Oxy-Fuel (HVOF) thermal spraying surface modification technique. The objective is to assess the tribological behavior of these as-sprayed samples under varying circumstances. Dry wear tests were conducted at both room temperature and 300 °C under a normal load of 30 N. The study comprehensively investigates the factors influencing wear resistance by analysing key microstructural and mechanical properties, including microhardness, porosity, and bond strength. Advanced characterisation techniques were employed, including Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) for surface morphology and elemental analysis and X-ray diffraction (XRD) for phase identification. A 3D profilometer was utilised to measure wear scar volume and quantify volumetric wear loss precisely. At room temperature, abrasive wear dominated, with ploughing and furrows as primary material removal mechanisms. Notably, the 316L-20%Cr3C2 coating exhibited better wear resistance compared to the 17-4ph-20%Cr3C2 coating. This enhanced performance is attributed to the carbide reinforcements, which significantly increased hardness and improved wear resistance under high temperatures. These findings emphasize the potential of carbide-reinforced HVOF coatings as an effective surface engineering approach for enhancing the performance and service life of maraging steel under harsh operational conditions, particularly those involving high temperatures and severe wear. © © 2025 by ASME.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 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 Effect of molybdenum on high-temperature tribological performance in HVOF sprayed of WC-based coatings on superni-76(SAGE Publications Ltd, 2025) Behera, N.; Sarmah, P.; Chandramouli, T.V.; Ramesh, M.R.This study examines the effects of Mo on the high-temperature wear and friction behavior of HVOF-sprayed 70%WC-Co/25%Mo/5%C and 70%WC-CrC-Ni/30%Mo coatings on Superni-76. The ball-on-disc tribometer wear tests were conducted at different temperatures (300°C and 600°C) and loads (10 and 30?N) against counter body Al2O3 ball. Microstructures and phase formation were investigated using SEM/EDS and XRD. The characterization of coating microhardness, surface roughness, and coating density was examined. The 70%WC-Co/25%Mo/5%C coating showed lower surface roughness and higher microhardness values than the 70%WC-CrC-Ni/30%Mo coating. The wear rate of the substrate increases with an increase in temperature, whereas 70%WC-Co/25%Mo/5%C and 70%WC-CrC-Ni/30%Mo coatings decrease with temperature from 300°C to 600°C. The coefficient of friction of substrate and coating decreases with increasing temperatures. The worn surfaces of 70%WC-Co/25%Mo/5%C and 70%WC-CrC-Ni/30%Mo coating contain oxide phases (WO3, Cr2O5) and lubrication phases (M0.2W0.8O3, CoMoO4, and MoO3) at 600°C. These oxide phases reduced the coating wear rate and coefficient of friction at 600°C. The 70%WC-Co/25%Mo/5%C coating showed improved resistance to wear and lower friction coefficient than the substrate and 70%WC-CrC-Ni/30%Mo coating. At temperatures of 300°C, the main abrasive wear mechanism changes to oxidative wear when the temperature reaches 600°C for both coatings. © The Author(s) 2025.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.