Faculty Publications

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Publications by NITK Faculty

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    An Assessment of Coating Thickness on the Microstructure and Mechanical Behavior of IN625 Coating on Ni-Based Superalloy Substrate Deposited by High Velocity Air Fuel Technique
    (Springer, 2024) Prashanth, M.; Babu, N.; Kumari, S.; Maurya, S.S.; Keshri, A.K.; Cadambi, S.; Nand Gosvami, N.N.; Bhowmik, A.
    High velocity air fuel (HVAF) technique, an innovative thermal spraying method, has proven more promising than traditional methods for both coating and repairing surfaces. This study focuses on the application of different thicknesses of IN625 superalloy coatings using HVAF to assess its potential for repair and cladding applications. Detailed coating characteristics of IN625 superalloy coating have been examined based on various techniques like nanoindentation, adhesion, micro-tensile and flexural strength of the coated samples. Within the coating, ? (NiCr rich), secondary peaks ?? and carbide phases were identified. Particle deformation under impact and rapid cooling resulting in the formation of ?? precipitates enhances the coating strength. However, the decrease in the adhesion strength with increasing coating thicknesses results from the defects formed at the coating–substrate interface and also influenced by thermal stresses and oxidation. Coating microstructure revealed a strong particle-to-substrate adhesion and varied splat morphologies dependent on degree of particle melting—at higher particle velocities in-flight oxidation of the powders was also minimal. Furthermore, the in-plane cohesive strength of the coating approaches 50% of the wrought alloy's yield strength, attributed to strain hardening from the peening effect. However, decrease in flexural strength as coating thickness increases due to compressive residual stress and coating delamination. The flexural strength of the as-sprayed coating exhibits up to 70% of the flexural strength of the wrought material with thicker coatings exhibiting lower strength. © ASM International 2024.
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    A Novel Dual-Input Single-Output High-Gain DC-DC Converter for Interfacing Fuel Cell with High-Way Charging Station Applications
    (Institute of Electrical and Electronics Engineers Inc., 2025) Diwakar Naik, M.D.; Vinatha Urundady, U.
    This article presents a novel dual-input single-output high-gain dc-dc converter designed specifically for interfacing fuel cells (FCs) with high-way charging station applications. The converter boasts several notable features, including high output voltage gain achieved with only two switches, continuous input current, reduced switch stress, and the ability to provide a reliable continuous power supply. This article elucidates the two operating modes of the converter along with their corresponding switching states. In addition, it delves into the design and analysis of the proposed converter, covering various aspects, such as the development of a state-space model and the derivation of the small-signal transfer function to comprehend the dynamic behavior of the converter. Moreover, a suitable control strategy using the k-factor method has been devised to effectively regulate the output voltage and ensure stability, even in the face of input voltage fluctuations. To validate the effectiveness of both the proposed converter and controller, a 150-W prototype was meticulously constructed and experimentally verified in a laboratory setting. © 2024 IEEE.
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    Novel adsorption-based upgradation of end-of-life polypropylene pyrolysis oil using carbonised rice husk
    (Elsevier Ltd, 2025) Kailas, T.G.; A R, A.; Dutta, S.; Madav, V.
    Plastic waste management is a global issue, with end-of-life polypropylene (EoL PP) having significant contribution. Polypropylene degradation forms undesirable compounds in pyrolysis oil, reducing its quality and limiting its fuel usability. Pyrolysis offers a promising solution for converting plastic waste into valuable fuels; however, the presence of degraded materials necessitates an effective upgrading process to enhance the fuel quality. This study introduces an innovative ex-situ adsorption-based upgradation technique using carbonised rice husk (CRH), an abundantly available, sustainable and cost-effective biomass residue, to significantly improve the quality of pyrolysis oil derived from EoL PP. The upgradation process reduced sulphur content in polypropylene pyrolysis oil from 0.19 % to 0.02 %. The cetane index, a key fuel quality metric, rose from 43.83 to 55.25, enhancing combustion properties. Proton nuclear magnetic resonance showed an increase in paraffin content from 53.15 vol% to 60.81 vol%, improving energy content and combustion efficiency. Olefins and aromatics decreased, improving fuel stability and reducing emissions. GCxGC TOF-MS analysis revealed a decrease in oxygenates and an increase in diesel-range hydrocarbons, improving fuel quality and stability. This comprehensive study highlights the dual benefits of CRH in enhancing fuel quality and supporting circular economy practices, making a significant contribution to the development of sustainable fuel alternatives in the waste-to-energy conversion sector. © 2024