Browsing by Author "Rao, T.N."

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High-temperature oxidation behavior of plasma-sprayed NiCrAlY/TiO2 and NiCrAlY/Cr2O3/YSZ coatings on titanium alloy
(Springer Science and Business Media Deutschland GmbH, 2022) Reddy, G.M.S.; Prasad, C.D.; Shetty, G.; Ramesh, M.R.; Rao, T.N.; Patil, P.
The 70% NiCrAlY + 30% TiO2 and 70% NiCrAlY + 25% Cr2O3 + 5% YSZ metallic coatings are sprayed on titanium-15 alloy of ASTM B338, Grade 2, by using the plasma spray coating technology. Cyclic oxidation studies are conducted on the uncoated and coated alloys at 700 °C under static air environment. The kinetics of oxidation is studied by using the thermo-gravimetric method. Phase, microstructural, and chemical analysis tests are performed on as-sprayed and oxidized coatings. The coated alloys are found to be more resistant when compared to the uncoated alloys. The NiCrAlY + Cr2O3 + YSZ coating is found to be more protective when compared to NiCrAlY + TiO2 coating. It is concluded that the formation of Cr2O3, NiCr2O4, and Al2O3 is attributed to the development of oxidation resistance in the coatings. © 2022, International Institute of Welding.
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.
Solid Particle Erosion Behaviour of Plasma-Sprayed (WC–Co)/(Cr3C2–NiCr) Coatings
(Springer Science and Business Media Deutschland GmbH, 2022) Reddy, G.M.S.; Ramesh, S.; Anne, G.; Ramesh, M.R.; Rao, T.N.; Patil, P.
This study reports the high-temperature erosion behaviour of plasma-sprayed 35% (WC–Co)/65% (Cr3C2–NiCr) coating on MDN-420 alloy. Plasma spray coatings have always played a pivotal role in enabling industries to combat problems of premature degradation of components that operate in harsh environments. (WC–Co) + (Cr3C2–NiCr) coating is investigated for erosion under various laboratory-simulated conditions. Coating surface is characterized by using an optical microscope, scanning electron microscope (SEM), and X-ray diffraction (XRD). Porosity, microhardness, surface roughness, and adhesion strength of the coating are measured. The solid particle erosion test is conducted at the temperatures of 300 °C, 500 °C and 700 °C with the impact angles of 30° and 90° by using Al2O3 as an erodent in the hot air jet erosion testing machine. The optical profilometer is used to evaluate the erosion volume loss of the coated and uncoated samples. It is observed that erosion resistance of the substrate is found to be higher than the coating at the different test temperatures. As the temperature increases, the erosion resistance of the coating is also increased at all the temperatures for both impact angles of 30° and 90°.The eroded coating surface morphology reveals that the generalized behaviour of the coating is ductile in nature. © 2022, The Author(s), under exclusive licence to Springer Nature Switzerland AG.