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 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.