Faculty Publications
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Item Effect of Impact Angles and Temperatures on the Solid Particle Erosion Behavior of HVOF Sprayed WC-Co/NiCr/Mo and Cr3C2-CoNiCrAlY Coatings(Springer, 2023) Behera, N.; Medabalimi, S.; Ramesh, M.R.Extreme erosion wear from elevated temperature caused by the impact of entrained solid particles in the fluid stream primarily affects aerospace components and marine parts. This work focuses on increasing the base material erosion resistance by applying thermally sprayed carbide-based coatings. A high-temperature Solid particle erosion behavior of WC-Co/NiCr/Mo and Cr3C2-CoNiCrAlY coatings deposited by the HVOF process on a titanium-31 was evaluated using an air-jet erosion tester. The erosion test was conducted utilizing alumina erodent of grit size 35-50 µm. The effects of impact angles (30°, 60°, and 90°) and temperatures (200-800 °C) on the erosion performance of two coatings are compared. The feedstock powder and as-sprayed coatings were characterized for micro-structure phase composition, porosity, density, micro-hardness, and adhesion strength. SEM/EDS and a 3D optical profilometer were used to examine eroded samples further to determine the erosion mode. The Cr3C2-CoNiCrAlY coating shows a brittle mode behavior of erosion at 200-400 °C and ductile mode behavior of erosion at 600-800 °C. In contrast, the WC-Co/NiCr/Mo coating shows brittle mode behavior of erosion at 200-400 °C and 600-800 °C, a mixed mode behavior of erosion. The erosion loss in volume of Cr3C2-CoNiCrAlY is lower than WC-Co/NiCr/Mo for all temperatures and impact angles. The development of carbide and oxide phases on the eroded surfaces demonstrates increasing erosion resistance at high temperatures. The optical profilometer measures the volumetric erosion loss, compares it with the weight loss method, and finds consistency between them. © 2023, ASM International.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 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 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