Faculty Publications
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Item Development and properties evaluation of Mg-6% Zn/Al multilayered composites processed by accumulative roll bonding(Cambridge University Press, 2017) Anne, G.; Ramesh, M.R.; Shivananda Nayaka, H.; Arya, S.B.; Sahu, S.Accumulative roll bonding (ARB) process was used to develop Mg-6% Zn/Al and Mg-6% Zn/anodized-Al multilayered composites. Microstructural characterization was done using scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscattered diffraction, and transmission electron microscopy. An average grain size measured in the roll-bonded layers of Al, anodized Al, and Mg-2% Zn was found to be 1.8 ?m, 1.6 ?m, and 0.6 ?m, respectively. Phases Al17Mg12, AlMg4Zn11, and Al2O3 after 5-pass of ARB were confirmed by X-ray diffraction analysis. The Mg-6% Zn/Al and Mg-6% Zn/anodized Al composites exhibited tensile strengths ?252 MPa and ?256 MPa, respectively, after a 5-pass ARB process. Hardness of the individual layers of composite increased linearly with an increase in the number of ARB passes. Fractographs of the multilayered composite illustrated the ductile failure in Al and anodized Al layers and transgranular brittle fracture in Mg-6% Zn layers. © Materials Research Society 2017.Item Influence of ceramic top coat and thermally grown oxide microstructures of air plasma sprayed Sm2SrAl2O7 thermal barrier coatings on the electrochemical impedance behavior(Elsevier B.V., 2018) Baskaran, T.; Arya, S.B.Electrochemical impedance spectroscopy (EIS) technique is used to examine the top coat and thermally grown oxide (TGO) microstructures of Samarium Strontium Aluminate (SSA) thermal barrier coatings (TBCs) after exposed to pre-oxidation and oxidation at 1050 and 1100 °C, respectively. EIS spectra showed that the three relaxations frequencies in Bode plot corresponded to SSA top coat, TGO, and TGO-bond coat interface. A significant reduction in polarization resistance of SSA top coat and increase in capacitance for different pre-oxidation times of 10, 20 and 30 h are being found due to increasing the defects (pores and cracks) of about 13, 29 and 45%, respectively at 1050 °C. The reduction in bi-axial residual stresses was calculated to be about 57% as a consequence of decrement in top coat resistance. The growth of SSA TGO was found from 10 to 20 h of pre-oxidation treatment caused to decrease the capacitance which indicates the presence of highly enriched ?-Al2O3 at the bond coat-top coat interface. The highest charge transfer resistance and lowest capacitance were found to be about 0.48 × 106 ? cm2 and 1.1 nF cm?2 respectively for 20 h of pre-oxidation which could reflect the overall impedance kinetics of TBC system (SSA top coat and TGO) at the TGO-bond coat interface. The impedance responses of SSA top coat, TGO, and TGO-bond coat interface were reduced drastically after oxidation at 1100 °C for 10 h pre-oxidized specimen as compared to 20 and 30 h due to the compositional change of pure ?-Al2O3 based TGO into more conductive NiCr2O4. The lowest diffusion coefficient, DCr3+ in the NiO lattice which reduced the formation of metal ion vacancies at the TGO-top coat interface caused to exhibit higher TGO resistance for 20 h pre-oxidized specimens over 10 and 30 h after oxidation at 1100 °C. © 2018 Elsevier B.V.Item Deposition of TiN and TiAlN Thin Films on Stainless Steel Tubes by a Cylindrical Magnetron Sputtering Method(ASTM International, 2021) Trivedi, K.; Rane, R.; Joseph, A.; Arya, S.B.Titanium nitride (TiN) and titanium aluminum nitride (TiAlN) coatings are very hard materials that are mostly coated on cutting tools to increase the tool life. These coatings have also been successfully applied as a coating material for biomedical applications mainly due to their tribological properties, biocompatibility, and affordable price. In an attempt to develop transition metal nitride coatings on specimens of cylindrical geometry, TiN and TiAlN thin films were deposited successfully on stainless steel tubes using a direct-current cylindrical magnetron cosputtering method. Both types of coatings were uniform in nature and had good adherence to the substrate. TiN and TiAlN thin films were characterized systematically to determine their structure, surface morphology, chemical states, chemical structure, and electrochemical behavior using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and potentiodynamic methods, respectively. The XRD patterns of the TiN and TiAlN coatings indicated (111) preferential orientation. Crosssectional SEM images revealed a columnar growth of the coatings with an arrow-headed geometry. XPS characterization showed the presence of TiN, Titanium dioxide, titanium oxynitride, aluminum oxide, and aluminum nitride phases. Potentiodynamic polarization tests in 3.5 % sodium chloride solution revealed that the TiAlN coating exhibited superior corrosion resistance compared with the TiN coating. Furthermore, TiAlN coating showed 94 % of average absorption in ultraviolet-visible region using photospectrometry. The cylindrical magnetron sputter deposition technique enables development of uniform protective coatings on tubular geometries, which are frequently employed in solar thermal and nuclear applications. © 2021 by ASTM International.Item Hot corrosion behavior of Al2O3 + Sm2SrAl2O7 composite thermal barrier coatings(John Wiley and Sons Inc, 2022) Joseph, F.J.; Arya, S.B.; Tailor, S.Rare earth-based samarium strontium aluminate (Sm2SrAl2O7) powder has been synthesized in the laboratory through molten salt synthesis and Al2O3 + Sm2SrAl2O7 (SSA) thermal barrier coatings have been developed on an Inconel 718 superalloy substrate by atmospheric plasma spraying technique. The microstructures and surface morphologies of the samples before and after the hot corrosion tests in 50 wt% Na2SO4 + 50 wt% V2O5 (aviation atmosphere) and 90 wt% Na2SO4 + 5 wt% V2O5 + 5 wt% NaCl (marine atmosphere) at 700°C and 900°C were examined. It is observed that samples exposed to marine conditions exhibited 14.5% and 11.6% lower lifetime than the samples exposed to aviation conditions at 700°C and 900°C, respectively, due to significant chlorides attack. © 2022 Wiley-VCH GmbH.Item Isothermal oxidation characteristics of laser-treated Al2O3 + Sm2SrAl2O7 composite thermal barrier coatings(John Wiley and Sons Inc, 2023) James J, F.; Arya, S.B.; Satish Kumar, D.A thermal barrier coating system with Al2O3 + Sm2SrAl2O7 composite top coat was developed on an Inconel 718 superalloy substrate by using an atmospheric plasma spray technique, and the coated samples are treated with an Nd:YAG fiber laser to improve the surface properties. The as-coated and laser-treated samples were subjected to high temperature isothermal oxidation test at 1100°C for 150 h duration. The surface of the oxidized samples showed the presence of dissociated SmAlO3, SrAl2O4, and Sm2O3. Thermally grown oxides (TGO) are found at the bond coat top coat interface of the samples. The oxidation kinetics is examined by monitoring weight gain at regular intervals. The electrochemical impedance behavior, oxidation mechanism, and TGO formation in the developed composite coatings are discussed in detail. © 2023 Wiley-VCH GmbH.Item Enhancement of Corrosion Resistance of Al2O3 + Sm2SrAl2O7 Composite Thermal Barrier Coatings by Laser Treatment(Springer, 2024) James J, F.; Arya, S.B.The rare earth aluminate Sm2SrAl2O7 was synthesized in the laboratory through a molten salt synthesis technique at 1100 °C. A composite thermal barrier coating system on Inconel 718 substrate was developed with Al2O3–Sm2SrAl2O7 composite as the top coat and NiCrAlY as the bond coat using atmospheric plasma spraying. The surface of the plasma-sprayed coatings was treated using an Nd: YAG fiber laser to seal off the open porosities and reduce surface roughness. Hot corrosion tests on the laser-modified samples were performed at 700 °C and 900 °C, in aviation and marine corrosive conditions using 50 wt.% Na2SO4 + 50 wt.% V2O5 and 90 wt.% Na2SO4 + 5 wt.% V2O5 + 5 wt.% NaCl, respectively. The laser-treated samples showed higher resistance to failure than the as-coated samples under similar conditions. The corrosion products are identified, and the mechanisms involved are discussed in detail. The effect of surface modifications on the hot corrosion resistance of the coatings is investigated. © The Indian Institute of Metals - IIM 2023.Item Effect of Surface Modification on Erosion Behavior of Alumina-Samarium Strontium Aluminate Composite Thermal Barrier Coatings(Springer, 2025) James J, F.; Arya, S.B.; Yadav, S.; Paul, C.P.The mechanical and tribological characteristics of a thermal barrier coating are highly critical in gas turbine applications to resist high-temperature oxidation, corrosion, and solid particle erosion. In the present investigation, a composite coating with alumina and samarium strontium aluminate has been developed through a plasma spraying process. The as-coated composite top coat consisted of three phases ?-alumina, ?-alumina, and Sm2SrAl2O7. The as-coated surface is re-engineered with an Nd: YAG fiber laser to improve the mechanical and microstructural properties. The laser-treated samples showed a better erosion resistance than the as-coated samples. Despite the surface treatment, both the as-coated and the laser-treated samples showed a higher ‘average erosion value’ at an impact angle of 90° for the test temperatures of 200 and 800 °C. In addition, the as-coated and the laser-treated samples have a higher erosion rate at 800 than at 200 °C for the selected impact angles, with a mixed mode of material removal presenting both ductile and brittle failure mechanisms. © ASM International 2024.