Browsing by Author "Kumari, S."

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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.
Improved electrochemical performance of graphene oxide supported vanadomanganate (IV) nanohybrid electrode material for supercapacitors
(Elsevier Ltd, 2020) Kumari, S.; Maity, S.; Anandan Vannathan, A.A.; Shee, D.; Das, P.P.; Mal, S.S.
Graphene oxide (GO)-supported polyoxometalates (POMs) have been considered as promising electrode materials for energy storage applications due to their ability to undergo fast and reversible redox reactions. Herein, vanadomanganate-GO composites (K7MnIVV13O38.18H2O-GO with 2:1 and 4:1 ratio) were investigated for use as potential electrode materials in supercapacitors (SCs). The K7MnIVV13O38.18H2O (MnV13) was synthesized and anchored on GO through electron transfer interaction and electrostatic interaction to make the composite electrodes for the present study. All synthesized electrode materials were fully characterized by various techniques, e.g., Fourier Transform Infrared (FTIR) Spectroscopy, Powder X-ray Diffraction (XRD), Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDS) and High Resolution-Transmission Electron Microscopy (HR-TEM). The electrochemical properties of MnV13/GO composites with different MnV13/GO ratios were investigated by two-electrode cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) in different electrolytes. The MnV13/GO composite of ratio 2:1 in 1 M LiCl electrolyte and that of ratio 4:1 in 1 M Na2SO4 electrolyte showed significant specific capacitance values of 269.15 F/g and 387.02 F/g, respectively and energy density of 37.38 Wh/kg and 53.75 Wh/kg, respectively for a scan rate of 5 mV/s. Interestingly, the 1:1 (MnV13/GO) composite in 1 M Na2SO4 and 1 M LiCl electrolytes showed very low specific capacitance values as the deposition of MnV13 on GO was not sufficient, as indicated by FTIR and SEM. Thus, it is evident that the specific capacitance value of these composite materials depends on the amount of MnV13 deposited on GO and these composite materials exhibit the potential to improve the performance of GO-based SCs. © 2019
Mechanical and Tribological Properties of High Velocity Air Fuel-Sprayed IN625 and IN718 Coatings
(Springer, 2025) Kumari, S.; Raj, S.; Babu, N.; Prashanth, M.; Junaid, S.; Cadambi, S.; Mondal, C.; Nand Gosvami, N.N.; Bhowmik, A.
This study explores the mechanical and tribological behavior of IN625 and IN718 coatings deposited on Ni-based IN718 alloy substrates using the high-velocity air fuel, HVAF technique. Microstructural analysis revealed that the IN625 coating exhibited more visible splats, weaker bonding, and a greater presence of unmelted and partially melted regions than IN718. Both IN625 and IN718 coatings retained the original constituent phases from the powder. The IN718 coating, however, demonstrated superior mechanical properties, with its hardness and adhesion strength surpassing those of IN625 by 56% and 30%, respectively. Notably, the adhesion strength was highest in a 0.5 mm thick IN718 coating, reaching 63 MPa. At room temperature, both the coatings had significant coefficient of friction (COF) values, while the wear volume loss for IN718 was reduced by 52% compared to IN625, although IN625 showed wider wear scars with more pits, deeper grooves, and peeling. IN718 formed a glaze layer, enhancing its wear resistance. These findings suggest that optimally thick IN718 HVAF coatings hold significant promise for improving performance in various repair and cladding applications. © ASM International 2025.
Optimisation of Machining Parameters using Grey Relation Analysis integrated with Harmony Search for Turning of AISI D2 Steel
(2018) Kumari, S.; Kumar, A.; Kumar, Yadav, R.; Vivekananda, K.
The objective of this study is to investigate the effects of different turning parameters like spindle speed (N), feed rate (f) and depth of cut (d) on different output performance parameters measures during dry turning of AISI D2 Steel using PVD coated carbide tool. An experiment has been conducted according to L9 orthogonal array in order to evaluate the turning performance characteristics like material removal rate (MRR) and surface roughness (Ra). An Effort was put to convert the multi responses into equivalent single response i.e. overall grey relation grade by using grey relational analysis. The present study also developed a mathematical model for overall grey relation grade in terms of the machining parameters. Here, improved version of the latest evolutionary algorithm such as harmony search (HS) has been implemented in order to evaluate the optimal machining condition. The results are also compared to genetic algorithm to validate the efficiency of aforesaid approach. � 2017 Elsevier Ltd. All rights reserved.
Optimisation of Machining Parameters using Grey Relation Analysis integrated with Harmony Search for Turning of AISI D2 Steel
(Elsevier Ltd, 2018) Kumari, S.; Kumar, A.; Kumar Yadav, R.; Vivekananda, K.
The objective of this study is to investigate the effects of different turning parameters like spindle speed (N), feed rate (f) and depth of cut (d) on different output performance parameters measures during dry turning of AISI D2 Steel using PVD coated carbide tool. An experiment has been conducted according to L9 orthogonal array in order to evaluate the turning performance characteristics like material removal rate (MRR) and surface roughness (Ra). An Effort was put to convert the multi responses into equivalent single response i.e. overall grey relation grade by using grey relational analysis. The present study also developed a mathematical model for overall grey relation grade in terms of the machining parameters. Here, improved version of the latest evolutionary algorithm such as harmony search (HS) has been implemented in order to evaluate the optimal machining condition. The results are also compared to genetic algorithm to validate the efficiency of aforesaid approach. Â© 2017 Elsevier Ltd. All rights reserved.