Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
Search Results
Item Improving Surface Finish of Laser Additively Manufactured Curvilinear Surfaces Via Electropolishing and Electroless Coating(American Society of Mechanical Engineers (ASME), 2025) Praharaj, A.K.; Kambikath, N.V.; Suvin, P.S.; Bontha, S.Laser-directed energy deposition (LDED) is a very useful additive manufacturing technique for repairing and manufacturing complex-shaped parts compared to traditional manufacturing techniques. However, the inadequate surface quality of the LDED fabricated components limits their direct utilization in different sectors. In addition, improving the surface finish of the curvilinear surfaces (useful for cooling channels and fuel nozzles) is also challenging. Hence, the current study focuses on surface modification of LDED fabricated SS 316L hollow cylindrical samples by combining electropolishing and electroless coating. We have performed electropolishing (two different currents, 8 A and 15 A) on the as-deposited (AD) sample with and without the application of the grinding process. The electropolishing reduced the roughness of the AD sample from 3.2 ?m to 0.85 ?m and 0.74 ?m for 8 A and 15 A, respectively. The reduction in roughness was more at a higher current value due to the rapid anodic dissolution of the surface peaks. A further reduction in roughness was observed when grinding was performed before electropolishing. However, grinding resulted in higher material removal from the deposited surfaces and reduction in roughness was also minimal. Hence, only the electropolishing sample was selected for the next step, in which Ni-P electroless coating was performed on the surface to form a protective layer. After electroless coating, the coefficient of friction and wear-rate were reduced by 9.5% and 25.6% compared to the AD sample. Delamination and severe plastic deformation were the major wear mechanisms for the AD sample, whereas abrasion was dominant for the coated sample. The current work proposes a combined surface modification approach of electropolishing and electroless coating for the LDED processed components with curvilinear surfaces. © © 2024 by ASME.Item Mechanical and chemical post-treatments for enhancement in tribological performance of laser powder directed energy deposited Inconel 625(Elsevier B.V., 2025) Praharaj, A.K.; Byregowda, T.; Bontha, S.; Suvin, P.S.Laser powder-directed energy deposition (LP-DED) technique has shown tremendous potential to fabricate high-performance superalloy parts for real engineering applications. However, certain disadvantages like poor surface quality and incompetent mechanical and wear properties limit its practical usage. Hence, the current work investigates the effect of different post-processing techniques, including laser shock peening (single shot) (LSP1), laser shock peening (three shots) (LSP2), shot peening (high pressure) (SP1), shot peening (low pressure) (SP2), glass bead blasting (GB), sand blasting (SB), and electroless coating (EC) on the surface quality, hardness, and wear resistance of Inconel 625 (IN625) samples fabricated by LP-DED technique. EC sample resulted in the least surface roughness value (0.09 µm), whereas LSP2 sample exhibited the highest increase of 32.4 % in hardness compared to the as-polished (AP) sample. This can be attributed to grain refinement and the plastic deformation in the samples. Further, the wear test confirmed that LSP2 sample resulted in the lowest coefficient of friction (0.6) and wear rate (0.58 × 10-4 mm3/N.m) among the post-processed samples. © 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