Faculty Publications
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Item Elevated temperatures erosion wear behavior of HVOF sprayed WC-Co-Cr/Mo coatings on Ti6Al4V substrate(Elsevier B.V., 2023) Behera, N.; Medabalimi, S.; Ramesh, M.R.The present research aims to investigate the effect of different impact angles and temperatures on volumetric erosion loss of WC-Co-Cr coating containing 10 wt% Mo. The composite coating was developed using High-Velocity Oxy Fuel (HVOF) process on a titanium substrate (Ti-31). A solid particle erosion behavior of the coatings is carried out at different impact angles (30°, 60°, and 90°) and temperatures (200 °C, 400 °C,600 °C, and 800 °C). The volumetric erosion loss of the coated samples was measured using an air jet erosion tester at high temperatures using Al2O3 as an erodent. The XRD, SEM/EDS, porosity, density, microhardness, bond strength, and scratch tests characterized the as-sprayed coatings. The 3D optical profilometer was employed to evaluate the volumetric erosion loss and the mode of erosion. The scratch resistance of WC-Co-Cr coating is better than WC-Co-Cr/Mo coating. The WC-Co-Cr coating shows a brittle mode of erosion up to 600 °C and a ductile mode of erosion at 800 °C. In contrast, the WC-Co-Cr/Mo coating shows a brittle mode of erosion at 200 °C and a mixed mode of erosion at 400 °C to 800 °C. The volumetric erosion loss of WC-Co-Cr is less than WC-Co-Cr/Mo for all temperatures and impact angles. The formation of oxide phases on the coating surfaces demonstrates erosion resistance at high temperatures. The results of volumetric erosion loss measured by the weight loss method correlate well with a non-contact type 3D optical profilometer. © 2023 Elsevier B.V.Item Elevated temperature wear and friction performance of WC-CoCr/Mo and WC-Co/NiCr/Mo coated Ti-6Al-4V alloy(Elsevier Inc., 2024) Behera, N.; Ramesh, M.R.; Rahman, M.R.The effect of adding Mo to WC-based coatings on the microstructure and dry sliding wear performance at elevated temperatures is investigated. The WC-based coatings are deposited using a high-velocity oxy-fuel process on the titanium-31 substrate. The coating was characterized by microstructure, microhardness, porosity, surface roughness, density, and bond strength. The wear and friction behavior of coatings was evaluated using a ball-on disc tribometer at temperatures of 200, 400, 600, and 800 °C and loads of 20 and 30 N. SEM-EDS and an optical profilometer were utilized to evaluate the wear rate and mechanism. The microhardness and bond strength of WC-CoCr/10%Mo coating is more than that of WC-Co/20%NiCr/10%Mo coatings. The WC-CoCr, WC-CoCr/10%Mo, and WC-Co/20%NiCr/10%Mo coatings exhibited decreasing wear rates up to 600 °C, transitioning to an increase at 800 °C. The oxide phases of CoWO4 WO3 MoO3, CoMoO4, and NiMoO4, formed at 600 °C, aid in reducing the rate of wear and friction coefficient. However, the wear rate slightly increased at 800 °C due to vigorous oxidation and softness of coatings. The friction coefficient of WC-CoCr, WC-CoCr/10%Mo, and WC-Co/20%NiCr/10%Mo coating decreases with increasing temperatures due to the lubricating properties of oxide phases on the worn surface. The WC-CoCr/10%Mo coating demonstrates a lower friction and wear rate than the WC-CoCr and WC-Co/20%NiCr/10%Mo coating. At 200 °C, the predominant wear mechanisms were abrasive and fatigue wear, while at 800 °C, oxidative wear, abrasive wear, and adhesive wear were observed. © 2024Item 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 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