Faculty Publications
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Item Effect of Laser Surface Modification on Texture, Roughness, Wettability and Surface Energy of Hastelloy C22, C276 & X(Trans Tech Publications Ltd, 2024) Suvin, P.S.; Singh, A.; Depu Kumar Patro, B.; Edachery, V.; Kailas, S.V.; Horng, J.H.Hastelloy is a nickel-chromium-molybdenum-iron-based alloy and a member of the ‘superalloy’ family. Hastelloy has exceptional properties like high strength, wear resistance and hightemperature stress-corrosion resistance. Therefore, Hastelloy is used in gas turbines, power plants, metal injection molding, etc. Many industrial applications are related to the properties of the surface. Wettability is a key surface property that affects applications like lubrication, adhesion, coating, heat conduction, etc. Laser Texturing is an excellent method to modify the surface properties of materials like metal, polymers and ceramic. In the present study, a carbon dioxide laser created unidirectional textures on Hastelloy (C22, C276, X). Different sets of unidirectional textures were formed by changing the laser power and frequency. Various roughness parameters were compared for every laser parameter. In this paper, the effective change in wettability properties of Hastelloy (C22, C276, X) after the Laser texturing process for a range of power and frequency were studied under DI water and glycerol as test fluids. Results show that the contact angle of the test fluid increases as the laser power increases, and the contact angle decreases as the laser frequency increases for all three superalloys. The surface energy of a given set of samples was also measured using the recorded contact angle of DI water and Glycerol by the OWRK equation. Similar trends were found in surface energy for all three Hastelloy. © 2024 Trans Tech Publications Ltd, Switzerland.Item Enhanced tribological performance of laser directed energy deposited Inconel 625 achieved through laser surface remelting(Elsevier B.V., 2024) Praharaj, A.K.; Chaurasia, J.K.; Gurugubelli, R.C.; Bontha, S.; Suvin, P.S.Inconel 625 (IN625) is an essential material for the manufacture of turbine blades and seals, aircraft ducting systems, engine components, and pressure valves. Laser Directed Energy Deposition (LDED) process has shown the potential to fabricate IN625 parts with superior mechanical properties and higher corrosion resistance when compared to those fabricated using conventional manufacturing techniques. However, the poor surface quality limits the practical application of LDED fabricated parts, especially in sectors that demand high tribological performance. To this end, this study focuses on improving the surface quality and tribological performance of LDED fabricated IN625 components using Laser Surface Remelting (LSR) as a postprocessing operation. The tribological performance was evaluated using a linear reciprocating ball-on-flat wear test setup. The surface roughness, remelting depth (RD), microstructure, hardness, and tribological performance (coefficient of friction and wear rate) of the remelted (RM) samples were compared with that of as-deposited (AD) samples. Microstructural characterization revealed that LSR resulted in grain refinement, reduced dendrite size, and primary dendritic arm spacing (PDAS). Laser scanning speed effects RD, dendrite size and PDAS via its effect on cooling rates. SEM + EDS analysis confirmed the presence of Laves phase in both AD and RM samples. XRD analysis of RM samples showed an increase in the amount of Laves phase. The refinement in microstructural features and the increased amount of Laves phase among the RM samples led to improvement in microhardness when compared to AD samples. Wear test results revealed a reduction in the coefficient of friction (COF) and wear rate after LSR with wear mechanism being either abrasive or delamination. Reduction in the size of dendrites and refinement in grain size are attributed to the enhanced tribological performance after LSR. © 2023 Elsevier B.V.Item Green lubricants in action: a comprehensive performance evaluation of groundnut oil-based cutting fluids in metal machining processes(Institute of Physics, 2024) Srinivas, M.S.; Kumar, D.; Suvin, P.S.; Kailas, S.V.; Pawar, S.R.; Roy Choudhury, M.As industries worldwide seek environmentally sustainable solutions, the metalworking sector faces a growing need for eco-friendly alternatives to traditional cutting fluids. This abstract introduces the concept of an innovative approach to cutting fluid technology—the use of groundnut oil as a base material for machining fluids. Derived from peanuts, groundnut oil presents a renewable and biodegradable alternative to petroleum-based counterparts, addressing concerns related to resource depletion and environmental impact. A comprehensive performance evaluation of groundnut oil- based cutting fluid has been carried out by series of critical tests such as separation testing, particle size and stability testing, frictional testing, corrosion testing and drilling testing. The results of these tests collectively contribute to a comprehensive understanding of groundnut oil-based cutting fluids, shedding light on their potential as sustainable and high-performance alternatives in metalworking. The zeta potential for the prepared green cutting fluid has been found to be 49.10 mV. The dimensions of the dispersed particles in a fluid of the cutting fluid have been found as 250-260 nm. The environmentally friendly cutting fluid exhibits favourable outcomes in corrosion resistance, frictional performance, and drilling efficacy during testing. © 2024 The Author(s). Published by IOP Publishing Ltd.Item Microstructure - corrosion performance correlation of laser directed energy deposited Inconel 625(Elsevier Ltd, 2025) Praharaj, A.K.; Bontha, S.; Balla, V.K.; Chakrapani, S.K.; Suvin, P.S.The primary objective of the current work is to understand the influence of process parameters on the corrosion performance of laser directed energy deposited Inconel 625 (IN625). In this regard, IN625 bulk samples were deposited using optimized laser power and three different scanning speeds. The as-deposited (AD) samples are named as AD-L, AD-M, and AD-H corresponding to low, medium, and high scanning speeds, respectively. Comprehensive microstructural characterization, microhardness evaluation, and electrochemical corrosion testing (medium: 3.5 wt% NaCl solution) were performed to correlate the process parameters with the microstructural features and corrosion performance. The results revealed that average grain size of the AD-H sample was lowered by 22.8 % and 19 %, respectively than the AD-L and AD-M samples, resulting in an enhancement of 8.4 % and 3.3 % in microhardness. Electrochemical corrosion tests indicated that AD-H sample possessed a higher corrosion potential (Ecorr) and a lower corrosion current density (Icorr) when compared to other samples, confirming the corrosion resistance of the samples in the order of AD-H > AD-M > AD-L. The higher scanning speed resulted in finer grains, high dislocation density, and lowered volume fraction of secondary phases, which are attributed to superior corrosion resistance of the AD-H sample. Surface analysis of the corroded samples suggested a greater susceptibility to localized corrosion over pitting corrosion. The current work provides valuable insights to the correlation between process parameters, microstructure, and corrosion performance of LDED fabricated IN625, confirming notable influence of scanning speed on the corrosion behavior. © 2025 Elsevier B.V.Item Investigation on the tribological performance of protic ionic liquid as an additive in PEG200 for steel–steel contact(SAGE Publications Ltd, 2025) Depu Kumar Patro, B.D.K.; Suvin, P.S.Ionic liquids (ILs) offer multifunctional capabilities as lubricant additives. However, many conventional ILs contain moisture-sensitive halogen-based anions that may hydrolyze to form corrosive halogen acids, leading to surface degradation. This study explored halogen-free, amine-based protic ionic liquids (PILs) as additives in polar base oil polyethylene glycol (PEG200). Anti-corrosion tests revealed that incorporating PILs into PEG200 significantly improves corrosion resistance. Lubrication tests performed at various PIL concentrations showed that the blend containing 5wt% PIL exhibited the best performance, reducing the friction coefficient by 26.12% and wear volume by 90.61% compared to neat PEG200. Spectroscopic analysis confirms the formation of a protective tribofilm within the wear tracks, consisting of oxy-organic compounds and metal oxides such as FeOOH, Fe2O3and Fe3O4. This tribofilm minimizes direct contact between sliding surfaces and facilitates effective lubrication. These findings demonstrate the potential of amine-based PILs as efficient and environmentally friendly additives for PEG-based lubricants. © IMechE 2025