Faculty Publications
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Item Evaluation of cyclic oxidation and hot corrosion behavior of HVOF-sprayed WC-Co/NiCrAlY coating(Springer New York LLC journals@springer-sbm.com, 2014) Somasundaram, B.; Kadoli, R.; Ramesh, M.R.Corrosion of metallic structural materials at an elevated temperature in complex multicomponent gas environments are potential problems in many fossil energy systems, especially those using coal as a feedstock. Combating these problems involves a number of approaches, one of which is the use of protective coatings. The high velocity oxy fuel (HVOF) process has been used to deposit WC-Co/NiCrAlY composite powder on two types of Fe-based alloys. Thermocyclic oxidation behavior of coated alloys was investigated in the static air as well as in molten salt (Na2SO4-60%V2O5) environment at 700 °C for 50 cycles. The thermogravimetric technique was used to approximate the kinetics of oxidation. WC-Co/NiCrAlY coatings showed a lower oxidation rate in comparison to uncoated alloys. The oxidation resistance of WC-Co/NiCrAlY coatings can be ascribed to the oxide layer of Al 2O3 and Cr2O3 formed on the outermost surface. Coated alloys extend a protective oxide scale composed of oxides of Ni and Cr that are known to impart resistance to the hot corrosion in the molten salt environment. © 2014 ASM International.Item Hot Corrosion Behaviour of HVOF Sprayed (Cr3C2–35 % NiCr) + 5 % Si Coatings in the Presence of Na2SO4–60 % V2O5 at 700 °C(Springer, 2015) Somasundaram, B.; Kadoli, R.; Ramesh, M.R.The hot corrosion behavior of high velocity oxyfuel sprayed (Cr3C2–35 % NiCr) + 5 % Si coatings on three substrate alloys of SA213-T22, MDN-310 and Superfer 800 H was investigated. The as-sprayed coatings are characterized with respect to microstructure and mechanical properties. Thermocyclic hot corrosion studies were performed in a molten salt environment of Na2SO4–60 % V2O5 for 50 cycles at 700 °C. Thermogravimetric technique was used to establish the kinetics of hot corrosion of uncoated and coated steels. It was observed that the coated steel showed better hot corrosion resistance than the uncoated steels. The coated steels follow the parabolic rate law of oxidation and the parabolic rate constant values are appreciably lower in comparison to the uncoated steels. The coated steels showed slow oxidation kinetics which indicated that the reaction rate is diffusion limited. The oxides of Cr2O3 and SiO2 formed on the outermost surface of the coatings are found to be passive in the molten NaVO3 melt. © 2014, The Indian Institute of Metals - IIM.Item High temperature corrosion behaviour of HVOF sprayed WC-CrC-Ni coatings(Inderscience Publishers, 2016) Somasundaram, B.; Kadoli, R.; Ramesh, M.R.; RAMESH, C.S.The present work aims to study the hot corrosion resistance of high velocity oxy-fuel (HVOF) sprayed WC-CrC-Ni coating developed on three types of boiler tube materials such as SA213-T22, MDN-310 and Superfer 800 H steels. Hot corrosion studies were conducted in a molten salt environment of Na2SO4-60%V2O5 at 700°C and thermogravimetric analysis was used to establish kinetics of corrosion. Corrosion kinetics of coated steels followed nearly parabolic behaviour and showed a lower corrosion rate in comparison to uncoated alloys. It is concluded that corrosion is restricted to the external surface of the coating and the formation of thick scale composed of oxides of Cr, Ni and their spinel oxides, acts as a diffusion barrier to the transportation of corrosive species into the coating. The carbides of tungsten and chromium uphold the strength of the coating. © © 2016 Inderscience Enterprises Ltd.Item Erosion behaviour of HVOF sprayed (CR3C2-35%NICR) +5%Si coatings(IAEME Publication, 2017) Somasundaram, B.; Jegadeeswaran, N.; Madhu, G.; Ramesh, M.R.In the present study, (Cr3C2-35%NiCr) +5%Si cermet coatings were deposited on a Fe based T22 steel substrate to reduce the damage caused by erosion boiler applications. Erosion studies were conducted on uncoated as well as HVOF coated steels. The erosion experiments were carried out using an air-jet erosion test rig according to ASTM G-76 standard at a velocity of 30 m/s and at different impingement angles of 30°, 60° and 90°. Silica sand particles of size ranging between 150 to180 ?m were used as erodent. Analysis of weight-loss data and volumetric steady state erosion rates for different coatings and substrate alloys are evaluated. The bare T22 steel followed ductile erosion mode where as (Cr3C2-35%NiCr) +5%Si coating exhibited mixed behaviour respectively.Item Microstructure characteristics and properties of WC-CrC-Ni HVOF coating for boiler tube steel(Elsevier Ltd, 2022) Somasundaram, B.; Patil, V.G.; Ramesh, M.R.; Kandaiah, S.; Jegadeeswaran, N.In the present work, the characterization of HVOF sprayed WC-CrC-Ni coating on three bare alloys of MDN-310, SA213-T22, and Superfer 800H was investigated with the HVOF technique. The microstructure of the specimens were examined using a range of characterization techniques including XRD analysis, SEM, and EDS interfaced to SEM. The as-sprayed coatings are characterized with respect to microstructure and mechanical properties. The porosity, surface roughness, coating thicknesses, density, and bond strength of coatings have been also evaluated. © 2021Item Hot corrosion behavior of plasma sprayed FeCrNiC and FeCrNiC/Cenosphere coatings on ASTM-SA213-T22 steel(Elsevier Ltd, 2022) Hanumanthlal, S.; Siddaraju, C.; Ramesh, M.R.; Thirtha Prasada, H.P.; Somasundaram, B.The steel alloys tubes used to manufacture boilers which are used in high temperature environment in thermal power plants are often subjected to high temperature corrosion. Therefore, to protect the surface of boiler tubes, protective coatings are used to counter the corrosion. In this work FeCrNiC and FeCrNiC/Cenosphere coatings deposited on T22 boiler tube steel using atmospheric plasma spraying. Thermocyclic hot corrosion studies were examined in a liquid salt condition of Na2SO4-60%V2O5 for 17 cycles of 51 h at 600 °C on uncoated and coated steel. Thermogravimetric practice was utilized to build up the kinetics of hot corrosion of uncoated and coated steel. As-coated samples are studied for microstructure and microhardness. The X-ray diffraction(XRD), Scanning electron microscopy(SEM)/Energy dispersive spectroscopy(EDX), and X-ray mapping characterization techniques were used to analyse the corrosion products. It was observed that FeCrNiC/Cenosphere coated steel showed better hot corrosion resistance than the uncoated steels. Parabolic rate constant values of coated steel are lower in comparison to the uncoated steels. Better resistance is provided by high-temperature stability of mullite, alumina, defensive glassy oxide layer of silicon, titanium and spinels of chromium and carbon that is formed at elevated temperatures. © 2021Item High Temperature Corrosion Behavior of High Velocity Oxy Fuel Sprayed NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 Composite Coatings on ASTM SA213-T22 Steel in a Coal-fired Boiler Environment(Materials and Energy Research Center, 2022) Patil, V.G.; Somasundaram, B.; Kandaiah, S.; Ramesh, M.R.; Patil, S.High-velocity oxy fuel (HVOF) sprayed coatings can improve the corrosion resistance of bare ASTM SA213-T22 boiler steel. In this report, we have investigated the NiCrMoFeCoAl-30%SiO2 and NiCrMoFeCoAl-30%Cr2O3 composite coatings were deposited on bare ASTM SA213-T22 boiler steel for corrosion protection. High-temperature corrosion studies were conducted in a molten salt (Na2SO4-60%V2O5) environment at 700ºC under thermo-cyclic conditions. The as-sprayed composite coatings are characterized for microstructure and mechanical properties. The thermo-gravimetric method was utilized to understand the kinetics of corrosion. Characterization of the corrosion products was examined by using scanning electron microscope (SEM)/ Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) techniques. The obtained results suggest both the composite coatings are favorable to corrosion resistance over the bare ASTM SA213-T22 boiler steel. The NiCrMoFeCoAl-30%Cr2O3 composite coating was concluded to present a superior corrosion resistance in the high-temperature corrosion environment because of the uniform distribution of the composite coating matrix and the development of protective protection Cr2O3 in the scale. The molten salt heat-treated chromium oxide containing coating shows good corrosion stability than the silica composite. This could be attributed to the high temperature assisted formation metal chromates, chromites and oxide layers. © 2022 Materials and Energy Research Center. All rights reserved.