Faculty Publications
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Item Elevated temperature erosion performance of plasma sprayed NiCrAlY/TiO2coating on MDN 420 steel substrate(Institute of Physics, 2022) Reddy G, M.S.; Prasad, C.D.; Patil, P.; Naresh, N.; Ramesh, M.R.The current study deals with the erosion behaviour of a plasma-sprayed 70% NiCrAlY + 30% TiO2 coating on MDN 420 steel substrate at extreme temperatures. The coating was characterized by using an optical microscope, Scanning Electron Microscopy and X-ray diffraction methods. The coating's porosity, microhardness, surface roughness, and adhesion strength were all examined. The solid particle erosion experiments were carried out at temperatures of 300 °C, 500 °C, and 700 °C, with impact angles of 30° and 90°. The tests were conducted by using the alumina as an erodent in the hot air jet erosion testing machine. The erosion volume loss of coated and uncoated samples was measured using an optical profilometer. It is observed that erosion resistance of the coating was found to be more when compared to the substrate for the different test temperatures chosen. As the temperature increases, the erosion resistance of the coating also found increased from 300 °C to 700 °C at both impact angles of 30° and 90°. The morphology of the eroded coating surface reveals that the generalized behaviour of the coating is ductile in nature. © 2022 IOP Publishing Ltd.Item High temperature erosion performance of NiCrAlY/Cr2O3/YSZ plasma spray coatings(Taylor and Francis Ltd., 2023) Reddy, G.M.S.; Prasad, C.D.; Patil, P.; Shetty, G.; Naresh, N.; Ramesh, M.R.The current investigation's objective was to assess the air jet erosion tester's ability to measure the erosive behaviour of plasma sprayed coatings on titanium-15 alloy. 65% NiCrAlY, 30% Cr2O3, and 5% YSZ make up the coating's chemical composition. A study of microstructure and phases was carried out. Microhardness and adhesive strength have both been measured in this work. With impact angles of 30° and 90° at 300°C, 500°C, and 700°C, Al2O3 erodent was utilised in a solid particle erosion test. An optical profilometer was used to calculate the erosion volume loss. The coating erosion resistance was found to be higher than the substrate sample for the test temperature that was employed, and this was more obvious at higher impact angles and higher temperatures The ductile character of the coating is seen in the contour of the deteriorated coating surface. © 2023 Institute of Materials Finishing Published by Taylor & Francis on behalf of the Institute.Item Investigation of the effect of NiCrAlY/Cr2O3/YSZ plasma coatings on erosion performance of MDN 420 steel at high temperature(Inderscience Publishers, 2023) Reddy, G.M.S.; Prasad, C.D.; Patil, P.; Shetty, G.K.; Kakur, N.; Ramesh, M.R.The purpose of the current study was to use an air jet erosion tester to examine the erosive behaviour of plasma sprayed coatings on MDN-420 that were composed of 70% NiCrAlY, 25% Cr2O3, and 5% YSZ. Microstructure and phase studies were performed. Measurements were made on the microhardness and adhesion strength. Al2O3 erodent was used in a solid particle erosion test with impact angles of 30° and 90° at 300°C, 500°C, and 700°C. The erosion volume loss was measured using an optical profilometer. For the test temperature used, it was found that the coating’s erosion resistance was greater than that of the substrate and that it was more pronounced at higher impact angles and higher temperatures. The shape of the degraded coating surface reflects the coating’s ductile nature. © © 2023 Inderscience Enterprises Ltd.Item Influence of subsequent thermomechanical cycles on shape memory behavior of 4D printed PEKK(Elsevier B.V., 2023) Ojha, N.; Kumar, S.; Ramesh, M.R.; Balan, A.S.S.; Doddamani, M.The current study identifies and investigates the shape memory response of poly ether ketone ketone (PEKK) for the first time. 4D printed PEKK are subjected to annealing, crystalline behavior, and shape memory studies under susquent thermomechanical cycles. Scanning electron microscopy (SEM) revealed seamless bonding between the printed layers, confirming the suitability of the chosen printing parameters. Differential scanning calorimetry (DSC) results showed higher Tg (161.20 °C) and Tm (339.03 °C). Shape fixity ratio (Rf) is observed to be lower in the higher cycles (∼10% lower in cycle 8 compared to cycle 1), while the shape recovery ratio (Rr) is noted to be decreasing in each cycle ( 20% decreased in cycle 8 compared to cycle 1) due to reduction in storage modulus. The 4D printed PEKK exhibited excellent shape memory properties as compared to PEEK, making them potential materials in automotive and aerospace applications. © 2023 Elsevier B.V.Item Elevated temperature tribological performance of non-equiatomic CoCrNiTiWx high entropy alloy coatings developed by mechanical alloying and high-velocity oxy-fuel spray(Elsevier B.V., 2024) Addepalli, S.N.; Joladarashi, S.; Ramesh, M.R.High entropy alloys (HEA) have applications in multiple fields owing to their exceptional mechanical and physical properties. In the current study, mechanical alloyed CoCrNiTiWx (x; a molar fraction, x = 0.5 and 1.5) HEA feedstock powders were deposited on maraging steel substrate using high-velocity oxy-fuel spray (HVOF). The phase evolution and the microstructure of the milled powders and as-sprayed coatings were analysed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The tribological behaviour of CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings at elevated temperatures was studied extensively using a Pin-on-Disc tribometer. The CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings retained the BCC solid solution phases formed during the milling stage. However, additional oxide and intermetallic phases were formed owing to the in-flight oxidation and high temperatures experienced during the HVOF deposition. The deposited coatings exhibited a lamellar structure and good mechanical bonding with the substrate. The porosities of CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings were found to be 1.69 ± 0.32 % and 1.51 ± 0.37 % respectively.Consequently, the CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings displayed average microhardness values of 863 ± 52 HV0.3 and 1025 ± 39 HV0.3, respectively. Further, the wear rates of coatings exhibited a significant reduction at elevated temperatures, owing to the formation of TiO2, NiCr2O4 oxide tribofilms for CoCrNiTiW0.5, and CoCr2O4, NiWO4, WO3 oxides for CoCrNiTiW1.5. The specific wear rate of CoCrNiTiW0.5 HEA coating dropped by 73.6 % from 22.7 ± 2.6 × 10−6 mm3/N-m to 5.99 ± 1.9 × 10−6 mm3/N-m, while CoCrNiTiW1.5 dropped by 78.8 % from 11.86 ± 3.5 × 10−6 mm3/N-m to 2.51 ± 1.5 × 10−6 mm3/N-m, with a rise in the temperature from RT to 600 °C. Likewise, The frictional coefficients of CoCrNiTiW0.5 HEA dropped from 0.504 ± 0.015 to 0.397 ± 0.005, while CoCrNiTiW1.5 HEA dropped from 0.578 ± 0.025 to 0.471 ± 0.004, with a rise in temperature from RT to 600 °C. At room temperature, the wear mechanisms of the as-sprayed CoCrNiTiWx coatings were dominated by adhesive wear. However, at elevated temperatures, a shift towards oxidative wear was observed. © 2023 Elsevier B.V.