Faculty Publications
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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 Effect of Heat Treatment on Microstructure and Dry Sliding Wear Behavior of Laser Directed Energy Deposited Inconel 625(Springer, 2025) Praharaj, A.K.; Chaurasia, J.K.; Suvin, P.S.; Narayanan, J.A.; Paul, C.P.; Balla, V.K.; Chakrapani, S.K.; Bontha, S.Laser directed energy deposition (LDED) is a promising technology for manufacturing and repair of Inconel 625 (IN625) components used in critical sectors requiring enhanced tribological performance due to harsh operating environments. Hence, the current work focuses on the evaluation of the tribological performance of LDED-built IN625 with the implementation of different heat treatment methods, i.e., solution treatment (ST), direct aging (AG), and solution treatment + aging (ST + AG). A detailed microstructural analysis, hardness, and wear testing were performed for the as-deposited (AD) and heat-treated (HT) samples, and the results were compared. The analysis revealed coarser grains in the case of ST and ST + AG samples, whereas finer grains for AD and AG samples, indicating grain coarsening after solution treatment. Further, the brittle laves phase gets dissolved after ST, whereas the AG and ST + AG samples resulted in the precipitation of metal carbides and strengthening phases. The microhardness of the ST sample (193.2 HV) was lower compared to the AD (211.6 HV) sample, whereas the AG and ST + AG samples exhibited 25.6 and 9.3% higher hardness than the AD sample. Considering tribological performance, the AG sample illustrated a maximum reduction of 61.4% in the coefficient of friction (COF) and 36.5% in wear rate when compared to the AD sample. This could be attributed to the presence of finer grains and strengthening phases. © ASM International 2025.Item Investigation on high-temperature tribological performance of laser directed energy deposited Inconel 625 for aerospace applications(Elsevier Ltd, 2025) Praharaj, A.K.; Bontha, S.; Balla, V.K.; Chakrapani, S.K.; Suvin, P.S.Laser directed energy deposition (LDED) is an emerging technique for fabricating superalloy based aero engine components. Hence, the current work investigates the tribological performance of LDED processed IN625 at room temperature (RT) and high temperature (HT) conditions of 850 °C to replicate the operating environment of aero engine components. The comparison with conventionally processed (CP) sample confirmed that as-deposited (AD) sample showed similar friction behavior to the CP sample but slightly improved wear performance. The COF and wear rate of AD sample reduced significantly at HT compared to RT due to the evolution of stable oxide layer. NiO, Fe2O3, and Cr2O3 were the major phases in oxide layer. The work indicates suitability of LDED to fabricate wear resistant surfaces. © 2024 Elsevier LtdItem Effect of temperature on tribological behavior of L–proline–based green deep eutectic solvents for Ti6Al4V interfaces: A study of novel potential lubricant(Elsevier Ltd, 2025) Kumar Patro, B.D.; Naik, S.; Suvin, P.S.; Udayakumar, U.; Kreivaitis, R.This study aims to develop a novel, eco-friendly lubricant engineered to meet antiwear requirements, reduce energy consumption, and improve performance reliability. A series of deep eutectic solvents (DESs) was successfully synthesized using a facile, one-step approach by combining eco-friendly L-Proline with diols and two distinct carboxylic acids as hydrogen bond donors. The resulting DES lubricants exhibit favourable physicochemical properties and excellent lubrication performance. Notably, the L-Proline /Oxalic acid DES demonstrates superior lubrication performance, resulting in a substantial decrease in both friction (?46–78 %) and wear volume (?61–91 %) compared to PEG 200 and choline chloride/urea across all tested temperatures. Furthermore, in-depth analysis of the worn surfaces reveals the formation of a tribo-chemical film derived from L-Proline based DESs, consisting of hydrocarbon (CxHy), oxy metal nitride (Ti-N-O) fragments, along with titanium oxide/hydroxide-rich layer. This film plays a vital role in delivering effective lubrication for titanium alloy surfaces. These findings pave the way for designing eco-friendly, high-performance lubricants for sustainable lubrication practices. © 2025 Elsevier LtdItem Enhancing the tribological performance of PEG 200 using oil-miscible deep eutectic solvents as lubricant additives(Elsevier Ltd, 2025) Kumar Patro, B.D.; Suvin, P.S.This study investigated a comprehensive assessment of the tribological and anti-corrosion behavior of a novel, halogen-free, and oil-miscible deep eutectic solvent (DES) additive in PEG 200. The DES, referred to as DOA, was synthesized from naturally derived L-Proline and oxalic acid and exhibited good miscibility with PEG 200 due to its polar functional groups. Corrosion tests, including electrochemical and copper strip experiments, confirmed that the DOA/PEG blends maintained consistent anti-corrosion performance. Tribological evaluations revealed that incorporating 3 wt% DOA resulted in a 30 % reduction in the coefficient of friction and a 60.3 % decrease in wear volume compared to PEG 200 alone. ANOVA analysis validated the statistical significance (p < 0.05) of DOA concentration on friction and wear responses, confirming a synergistic effect between DOA and PEG 200. These improvements are attributed to strong interfacial interactions and the formation of a protective tribo-chemical film. Surface characterization identified the presence of hydrocarbons (CxHy), iron oxides, and FeOOH layers, which improved lubrication in the steel–steel contact pair. These findings highlight the potential of DOA as a promising green additive for advancing sustainable lubrication technologies. © 2025 Elsevier Ltd