Faculty Publications
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Item Erosion behavior of Al2O3 + Sm2SrAl2O7 composite thermal barrier coatings(Elsevier Ltd, 2022) James J, F.; Arya, S.; Tailor, S.Thermal barrier coatings (TBC) are applied in gas turbines to protect the components from critical operating conditions at high temperatures. Foreign object damage is a major failure cause of turbine components due to erosion of the topcoat ceramic layer of the TBC system. In the present study, Samarium Strontium Aluminate (Sm2SrAl2O7) powders have been synthesized in the laboratory through molten salt synthesis, and thermal barrier coatings were developed using Atmospheric Plasma Spray (APS) technique on an Inconel substrate with NiCrAlY as a bond coat. The erosion behavior of the composite TBC system at temperatures of 200 °C and 800 °C at 30° and 90° impingement angles was analyzed using alumina erodent with a grit size of 50 µm. The erosion weight loss was measured in regular intervals and plotted against erodent mass. The samples exhibited a higher volumetric erosion at 90° and 800 °C. The morphological analysis of developed 70% Al2O3 + 30% Sm2SrAl2O7 composite coatings and eroded areas were performed using XRD, SEM, and surface profilometer. Erosion scars and surrounding deformed areas have been identified in the samples. The microstructure of the eroded areas in the samples showed micro-cutting and plowing as the major material removal mechanisms. Detailed phase analysis of the eroded locations in samples has been reported. © 2022Item 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.