Browsing by Author "Reddy, M."

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Hot corrosion behavior of plasma-sprayed NiCrAlY/TiO2 and NiCrAlY/Cr2O3/YSZ cermets coatings on alloy steel
(Elsevier B.V., 2021) Reddy, M.; Prasad, C.D.; Patil, P.; Ramesh, M.R.; Nageswara Rao, N.
The objective of the Present research work is to evaluate the hot corrosion resistance of plasma-sprayed 70% NiCrAlY+ 30% TiO2 and 70% NiCrAlY+ 25% Cr2O3+5% YSZ coatings on MDN 420 alloy. Hot corrosion tests are carried out under molten salt environment of Na2SO4+60 % V2O5 salt mixture at 700°C for 50 cycles. Each cycle consisting of 1 hour heating in a silicon carbide tubular furnace followed by 20 min of cooling. The thermogravimetric technique was used to determine the kinetics of corrosion. The scanning electron microscopy (SEM), energy dispersive analysis (EDAX), electron probe microanalyser (EPMA) and X-ray diffracton (XRD) techniques were used to evaluate the characterization of coatings with regard to coating bondstrength, thickness, microhardness and porosity. The parabolic rate constants of coated steels are lower when compared to the uncoated substrate. The NiCrAlY+ Cr2O3+YSZ coating is found to be more protective when compared to NiCrAlY+ TiO2 coating. The oxides of Al2O3, NiCr2O4, and Cr2O3 are formed on the outermost layer of the coatings which gives the resistance the coatings to high-temperature corrosion. © 2020
Studies on the role of HVOF coatings to combat erosion in turbine alloys
(2018) Prasanna, N.D.; Siddaraju, C.; Shetty, G.; Ramesh, M.R.; Reddy, M.
Erosive wear is caused by the action of sliding or impact of solids, liquids, gases or the combination of these. Solid particle erosion is an important material degradation mechanism encountered in a number of engineering systems such as gas turbine engines, thermal power plants, coal slurry pipe lines. Erosive action results from the impact of particulates, such as coal ash, dolomite and un-burnt carbon particles on the surface of turbine. Super alloys developed for high temperature applications suffer from the drawback that the strength and the erosion-corrosion resistance at high temperature exhibited are poor. To improve the resistance property, one way would be the use of coatings on the super alloy component. Coatings take care of the problems related to erosion whereas the super alloys take care of the requirement of strength at elevated temperature. Various coatings have been highly attractive; however, High Velocity Oxy-fuel (HVOF) process, a family of thermal spray techniques uses kinetic energy of the burnt gases to soften and to propel the spray powder producing dense very low porosity, good inter-particle cohesion and well bonded coatings. In the present study successful attempts have been made to spray Stellite-6, 10%Al2O3+90%CoCrAlTaY and 25%Cr3C2-20(Ni-Cr)+75%NiCrAlY on three kinds of turbine alloys, namely Ti-6Al-4V, Co-based super alloy (Super co 605) and Fe-based special steel (MDN121).Microstructure and mechanical properties of the coatings have been characterized. Erosion tests for different conditions using Air-jet erosion test rig for different impingement angles have been studied in detail. From these studies it is observed that satellite-6 coating exhibits lower erosive rate compared to other two coating materials. The morphology of the eroded surface shows craters, groove formation in the binder matrix and carbide pull-out as the existing erosion mechanism. Higher erosion loss is observed for Al2O3+CoCrAlTaY coating. � 2018 Elsevier Ltd.
Studies on the role of HVOF coatings to combat erosion in turbine alloys
(Elsevier Ltd, 2018) Prasanna, N.D.; Siddaraju, C.; Shetty, G.; Ramesh, M.R.; Reddy, M.
Erosive wear is caused by the action of sliding or impact of solids, liquids, gases or the combination of these. Solid particle erosion is an important material degradation mechanism encountered in a number of engineering systems such as gas turbine engines, thermal power plants, coal slurry pipe lines. Erosive action results from the impact of particulates, such as coal ash, dolomite and un-burnt carbon particles on the surface of turbine. Super alloys developed for high temperature applications suffer from the drawback that the strength and the erosion-corrosion resistance at high temperature exhibited are poor. To improve the resistance property, one way would be the use of coatings on the super alloy component. Coatings take care of the problems related to erosion whereas the super alloys take care of the requirement of strength at elevated temperature. Various coatings have been highly attractive; however, High Velocity Oxy-fuel (HVOF) process, a family of thermal spray techniques uses kinetic energy of the burnt gases to soften and to propel the spray powder producing dense very low porosity, good inter-particle cohesion and well bonded coatings. In the present study successful attempts have been made to spray Stellite-6, 10%Al2O3+90%CoCrAlTaY and 25%Cr3C2-20(Ni-Cr)+75%NiCrAlY on three kinds of turbine alloys, namely Ti-6Al-4V, Co-based super alloy (Super co 605) and Fe-based special steel (MDN121).Microstructure and mechanical properties of the coatings have been characterized. Erosion tests for different conditions using Air-jet erosion test rig for different impingement angles have been studied in detail. From these studies it is observed that satellite-6 coating exhibits lower erosive rate compared to other two coating materials. The morphology of the eroded surface shows craters, groove formation in the binder matrix and carbide pull-out as the existing erosion mechanism. Higher erosion loss is observed for Al2O3+CoCrAlTaY coating. Â© 2018 Elsevier Ltd.