Browsing by Author "Madhu Sudana Reddy, G."

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    High-Temperature Oxidation Studies of Plasma-Sprayed NiCrAlY/TiO2 and NiCrAlY/Cr2O3/YSZ Cermet Composite Coatings on MDN-420 Special Steel Alloy
    (Springer, 2021) Madhu Sudana Reddy, G.; Prasad, C.D.; Shetty, G.; Ramesh, M.R.; Rao, T.N.; Patil, P.
    The plasma spray process was used to form 70%NiCrAlY + 30%TiO2 and 70%NiCrAlY + 25%Cr2O3 + 5%YSZ cermet coatings on MDN-420 special steel alloy. Cyclic oxidation testing was conducted on coated and uncoated specimens at 700°C under a static air environment. Thermogravimetric analysis was applied to establish the oxidation kinetics. X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy-dispersive x-ray spectroscopy (EDS), and electron probe microanalysis (EPMA) techniques were used to analyze the oxidized products. The NiCrAlY + Cr2O3 + YSZ coating was found to be most resistive when compared with the NiCrAlY + TiO2 coating in the aggressive oxidation environment. Net weight loss was observed for bare MDN-420 alloy due to sputtering. The oxidation resistance of the coatings was due to formation of Cr2O3, NiCr2O4, NiO, and Al2O3 phases. © 2021, ASM International.
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    Investigation of thermally sprayed NiCrAlY/TiO2and NiCrAlY/Cr2O3/YSZ cermet composite coatings on titanium alloys
    (Institute of Physics, 2022) Madhu Sudana Reddy, G.; Prasad, C.D.; Patil, P.; Shetty, G.; Ramesh, M.R.; Nageswara Rao, T.
    The present work investigates the hot corrosion behavior of thermally sprayed 65 pct NiCrAlY + 35 pct TiO2 and 65 pct NiCrAlY + 30 pct Cr2O3 + 5 pct YSZ coatings on titanium 15 alloys. The coatings on the titanium 15 alloy substrates exhibit a near-uniform, dense, and adherent microstructure with a porosity of 2.7 to 2.9%. Thermogravimetric studies are made to examine the hot corrosion performance of coatings in a molten salt environment of Na2SO4 + 60%V2O5 at the temperature of 700 °C for 50 cycles. One cycle is carried out by heating for a period of one hour and cooling the sample at ambient conditions. The corrosion products are analyzed based on scanning electron microscopy, energy dispersive analysis, and X-ray diffraction techniques to study the morphology, phase composition, and abundance of the high-temperature corrosion constituents. The bare titanium-15 alloy, 65 pct NiCrAlY + 35 pct TiO2 coating and 65 pct NiCrAlY + 35 pct Cr2O3 + 5 pct YSZ coating produced a weight gain of 307.92 mg cm-2, 42.16 mg cm-2 and 44.02 mg cm-2 respectively after the period of 50 cycles. The effective resistance of the coatings is due to the formation of Ni3V2O8, NiCr2O4, Cr2O3 & AlV2O4 phases. © 2022 IOP Publishing Ltd.