Conference Papers
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Item Effect of ECAP on sliding wear behaviour of Mg-Zn-Gd-Zr alloy(Elsevier Ltd, 2020) Patil, A.; Bontha, S.; Ramesh, M.R.Magnesium is a lightweight, recyclable, and biocompatible material. However, the extensive commercial use of Magnesium and its alloys is hindered by their poor wear behaviour and mechanical properties. Equal Channel Angular Pressing (ECAP) is a severe plastic deformation technique which improves the material properties through grain refinement. In the present study, wear behaviour of ECAP processed Mg-Zn-Gd-Zr alloy was investigated. ECAP process was carried out up to 3 passes at a temperature of 380 °C. Wear testing of as-cast and ECAP processed alloy were carried out using dry sliding wear method on a pin on disk tribometer by varying loads. The wear mechanism was analysed using Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDS). Average Coefficient of Friction (COF) increased after each pass of ECAP. Wear rate increased with the applied load. Despite severe plastic deformation, wear resistance of ECAP processed samples was found to be lower than that of as-cast samples at higher loads. Abrasive and oxidation wear mechanisms were found in both as-cast and ECAP processed samples. © 2019 Elsevier Ltd. All rights reserved.Item Elucidating Corrosion Behavior of Hastelloy-X Built Using Laser Directed Energy Deposition-Based Additive Manufacturing in Acidic Environments(Springer Science and Business Media Deutschland GmbH, 2021) Diljith, P.K.; Jinoop, A.N.; Paul, C.P.; Krishna, P.; Bontha, S.; Bindra, K.S.This paper reports an investigation on the electrochemical corrosion behavior of laser directed energy deposition (LDED)-based additive manufacturing built Hastelloy-X (Hast-X) bulk samples for the first time in various acidic environments (2M HNO3, 2M HCl, and 2M H2SO4). Open-circuit potential results reveal that corrosion activity is more in HCl than the other two media. The corrosion rate (CR) estimated using the Tafel extrapolation method shows that the corrosion rate (CR) is the most in HCl and least in HNO3. Potentiodynamic studies reveal active–passive behavior of Hast-X in all the media and it is seen that the material stays in passivation for a longer potential range in HCl. Further, pitting potential is observed to be comparable in all three media. The cyclic polarization curve shows no loops, which points out the absence of pitting in the samples immersed in any of the media. The estimated CR for Hast-X in all the acidic environments under investigation comes within the acceptable CR for nickel-based alloys (4 mpy). The morphology of the corroded surface is analyzed using stereo microscope and it confirms the absence of pitting in all the three samples. These observations confirm the suitability of LDED built Hast-X components for applications in investigated acidic environments. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item An Improved Finite Element Based Approach to Predict Single Track Geometry During Laser Directed Energy Deposition(Springer Science and Business Media Deutschland GmbH, 2025) Chaurasia, J.K.; Gurugubelli, R.C.; Jinoop, A.N.; Bontha, S.; Paul, C.P.; Bindra, K.S.This paper reports development of a two-dimensional transient finite element based numerical model to predict dimensions of deposited single track during laser directed energy deposition (LDED) of Inconel 625 (IN625) superalloys. The numerical model in the paper is based on two steps where first melt pool dimensions are determined using a transient thermal simulation. The second step accounts for the material addition, where the elements are activated based on the calculation of excess enthalpy. The numerical model is based on the fundamental principles of energy and mass balance. The numerical model also incorporates the fluid dynamics effects by multiplying the correction factor to the thermal conductivity of the material above melting temperature and also compares the track dimensions without considering the correction factor. A comparison of the track height and width obtained from the numerical model at Cf = 1 and 2.5 with experimental measurements was done. The maximum absolute percentage error in the numerical model considering the fluid dynamics effects (Cf = 2.5) is 5% in track height and 9% in track width. The percentage errors in the case of numerical model without fluid dynamics effects (Cf = 1) is 13% in track height and 16% in track width. The numerical model without considering the fluid dynamics effect is found to overpredict the track dimensions in all the cases. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Influence of Process Parameters on Microstructural Properties of L-DED Produced Ti64 Alloy(Springer Science and Business Media Deutschland GmbH, 2025) Suresh, S.; Kuriachen, B.; Kumar, V.; Bontha, S.; Gurugubelli, R.C.Additive manufacturing (AM) techniques have revolutionized the manufacturing of complex and customized parts across various applications. However, they are known for producing titanium parts with high anisotropy and low ductility, due to high cooling gradient in the build direction and the presence of martensite phase in microstructure respectively. These are inherent problems which limit their application in critical engineering fields. Laser—Direct Energy Deposition (L-DED) produced parts also have the same disadvantages. Thus, the primary objective of this paper is to identify the optimal combination of process parameters for L-DED that can mitigate these inherent limitations. Keeping the parameters such as powder size, orientation angle and hatch angle as constant, the laser power and scan speed are varied to fabricate 9 different sets of samples using L-DED. The research methodology includes an analysis of the microstructure, focusing on grain width, phase distribution, lath characteristics and presence of defects, if any. Microscopy and XRD techniques were used to observe the microstructure. Additionally, hardness studies were performed to evaluate the changes in material hardness. It was noticed that laser power significantly influences β width and α’ length while scan speed has a lesser dominant effect on both of them. The findings will contribute to the development of process-structure-property relations for L-DED-produced Ti64 and further, optimized manufacturing strategies for producing titanium parts with reduced anisotropy and increased ductility. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Laser Surface Melting of Cold Metal Transfer Wire Arc Directed Energy Deposited AZ31 Mg Alloy(Springer Science and Business Media Deutschland GmbH, 2025) Manjhi, S.K.; Bontha, S.; Balan, A.S.S.The deposition of Mg alloy using an additive manufacturing process is challenging due to its volatile nature at high temperatures and difficult handling of Mg powder during fabrication. Therefore, the cold metal transfer wire arc additive manufacturing (CMT-WAAM) process deposits AZ31 Mg alloy because of its tremendous potential to fabricate heat-sensitive materials due to comparatively low heat input and wire as a feed material. However, the mechanical properties of CMT-WAAMed AZ31 Mg alloy are still poor due to pores, microcracks, and poor surface finish. Therefore, deposited components cannot be directly used in the application. Machining is required to make the surface smooth and flat before application. However, microcracks and burrs are the primary issues during milling operation, further reducing the mechanical properties and corrosion performance of deposited parts. Therefore, this study uses the laser surface melting (LSM) process to enhance surface properties by minimizing the microcracks and other CMT-WAAMed AZ31 Mg alloy defects. The obtained results of the 3D profilometer show that the surface roughness (Ra) of machined samples was 3.34 μm, which is reduced to 2.279 μm after laser surface melting treatment. In addition, optical microscope (OM) results exhibited a huge reduction of grain refinement after LSM from 45 ± 3 μm to less than 1 μm with dendrites microstructure. Consequently, the hardness of the surface increased from 60 ± 2 to 143 ± 10 HV due to grain refinement and the formation of secondary phase particles. The grain refinement and uniform distribution of secondary phase particles act as a barrier to Cl−1 corrosive ions, enhancing corrosion resistance after the SLM process. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.