Faculty Publications

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    Laser aided metal additive manufacturing and postprocessing: A comprehensive review
    (Elsevier, 2021) Velu, R.; Kumar, A.V.; Balan, A.S.S.; Mazumder, J.
    In the recent industrial revolution (Industry 5.0), additive manufacturing (AM) will be a very interesting technology, and it is predicted that it will have a significant impact on a wide range of industries in the near future. AM involves many different processing techniques, such as powder bed fusion, directed energy deposition (DED), sheet lamination, and so on, and it can use many different feedstock materials such as metals, polymers, and ceramics. In this chapter, we focused our attention on laser-based AM techniques used to produce metal parts, specifically in selective laser melting and laser-assisted DED techniques. The chapter begins with a classification of lasers and the interaction of lasers with materials. Furthermore, a comprehensive review on the classification of laser-based AM processes, their working principle, relevance of laser processing, need for postprocessing, and a classification of postprocessing techniques are explained in detail. Finally, it is shown that AM processes must be combined in the near future with all traditional manufacturing technologies; however, laser-based AM techniques have an excellent opportunity to influence the current manufacturing sector. © 2021 Elsevier Inc. All rights reserved.
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    Burnishing of ultra high molecular weight poly ethylene
    (Elsevier Ltd, 2021) Ashish, V.; Prasanna Kumar Reddy, S.; Kannan, C.; Oyyaravelu, R.; Balan, A.S.S.
    Ultra-high molecular weight polyethylene (UHMWPE) has been a choice for knee and hip implants since a very long time due to its outstanding tribological properties. UHMWPE has many applications other than biomedical implants like hydrodynamic bearings and marine applications. The main objective of this research work is to enhance the surface properties of UHMWPE and eventually increase its life expectancy for the implants. For this purpose, the UHMWPE sheet has been milled to give it a required shape and then ball burnished with a carbide ball of 6mm diameter under two different environments viz. room and cryogenic with three different burnishing strategic patterns. A constant load of 150N is maintained by the tool on UHMWPE sample with a burnishing feed of 4000mm/min along with a step over a distance of 0.06mm after every pass for three different carefully chosen burnishing patterns. To understand the wear behaviour of the material, wear test has been performed on reciprocating wear testing machine with a stainless-steel ball as a pin for 6500 cycles in the medium of Hank's balanced salt solution (HBSS) as a lubricating agent and to maintain the pH value which is same as in the human body. The lowest average surface roughness (Ra=0.52μm) is reported for the second strategy pattern which gets burnished under the cryogenic environment. This sample also exhibited better wear resistance than other samples burnished under different environments and using different strategic patterns. © 2021 Elsevier Ltd. All rights reserved.
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    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.
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    Additive manufacturing of magnesium alloys: Characterization and post-processing
    (KeAi Publishing Communications Ltd., 2024) Manjhi, S.K.; Sekar, P.; Bontha, S.; Balan, A.S.S.
    Magnesium and its alloys remain perilous in the framework of light weighting and advanced devices structure such as rockets and satellites. However, the utilization of Magnesium (Mg) is increasing every year, revealing growing demands in manufacturing industries. Manufacturing of Mg components is challenging because of their HCP crystal structure and limited ductility. In this context, additive manufacturing (AM) provides the flexibility to manufacture complex shape components with excellent dimensional stability. It also provides a new possibility for utilizing novel component structures that increase the applications for Mg alloy. This review herein pursues to holistically explore the additive manufacturing of Mg alloy with a synopsis of processes used and microstructure, mechanical properties, corrosion behaviour and postprocessing of AMed Mg alloy. The challenges and future scope of AMed Mg alloys are critically explored. © 2023 The Authors
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    Experimental Investigation and Parametric Optimization on Hole Quality Assessment During Drilling of CFRP/GFRP/Al Stacks
    (Springer, 2020) Janakiraman, A.; Pemmasani, S.; Sheth, S.; Kannan, C.; Balan, A.S.S.
    Carbon fiber/glass fiber-reinforced aluminum (Al) stacks are becoming predominant in the aerospace industries owing to their synergistic effect on numerous properties obtained by the combination of metal and composite material. This necessitates an investigation work to be performed on the machining characteristics of this special category of Al stacks. This research work focuses on studying the influence of cutting speed, feed rate and machining environment on thrust force, delamination and roughness of the finished surface of hybrid Al stacks. Dry, minimum quantity lubrication (MQL), and cryogenic environments are considered in this work. The impact of cutting speed on the responses is observed to be negligible in contrast to the feed rate. Moreover, the drilling under cryogenic environment is found to improve the surface finish and mitigated the delamination, while drilling under MQL environment minimized the thrust force. Regression models are also developed to determine the output responses. High-quality holes in aluminum stacks can be obtained under cryogenic conditions over other machining environments as revealed by multi-objective optimization. © 2020, The Institution of Engineers (India).
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    Exploring grinding and burnishing as surface post-treatment options for electron beam additive manufactured Alloy 718
    (Elsevier B.V., 2020) Karthick Raaj, R.; Vijay Anirudh, P.; Karunakaran, C.; Kannan, C.; Jahagirdar, A.; Joshi, S.; Balan, A.S.S.
    Numerous additive manufacturing (AM) techniques have been developed over the past decade. Features like immense freedom of intricate part design and shorter lead time make AM routes promising for a wide range of applications spanning aerospace, marine and automobile sectors. Among the various metal AM processes, Electron Beam Additive Manufacturing (EBAM) is being widely explored to realise the potential of Ni-based superalloys and Ti alloys for varied high-performance applications. A novel attempt has been made in this paper to assess the surface integrity of as-built EBAM nickel-based superalloy 718 (AB) subjected to grinding (G), Low Plasticity Burnishing (LPB) and their sequential combination. Apart from their influence on sub-surface microstructures, the effect of process variables during the above post-treatments on the residual stress profiles was also investigated. Results revealed that G + LPB results in about 0.6 ?m lower surface roughness, 17% improved microhardness compared to AB + LPB, and higher compressive surface residual stress as compared to LPB processed EBAM samples. The sequential grinding and LPB - improved microhardness, was also found to extend about 500 ?m more when compared to the LPB process. The G + LPB, which is greatly influenced by the prior grinding, smoothens the surface and thus results in a better surface finish. Highest hardness, superior surface finish, reduced porosity and improved compressive residual stress were observed in samples that adopted the AB + G + LPB sequence over other samples, with the LPB step at 40 MPa yielding the best results. © 2020 Elsevier B.V.
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    Effect of Cryogenics-Assisted Low-Plasticity Burnishing on Laser-Clad Stellite 6 over SS420 Substrate
    (Springer, 2020) Anirudh, P.V.; Kumar, B.; Girish, G.; Shailesh, S.; Oyyaravelu, R.; Kannan, C.; Balan, A.S.S.
    The influence of modern additive manufacturing methods, especially from the direct energy deposition (DED) processes to the coat-like finished components, is crucial under present industrial circumstances. DED induces several traits like enhanced mechanical, thermal properties in shorter lead time, which extend their adaptation for diverse applications including aerospace and automobile industries. Among the several DED processes, laser cladding has been a prospect that explores various capabilities of improving the wear resistance of cobalt-chromium (Co-Cr)-based alloys. Rather than fabricating the complete component using expensive alloys, laser cladding has paved an approach to deposit particles possessing superior qualities over the conventional material. This research work attempts to evaluate the surface integrity of SS420 when cladded with Stellite 6. The vertical face milling is executed on the cladded component surface to facilitate either low-plasticity burnishing (LPB) or cryogenic burnishing (CB) as sequential post-treatment processes. The effects of these post-treatments on the surface and subsurface microhardness, surface topography and residual stress profiles are elaborated. Increased surface and subsurface microhardness, as well as improved residual stress profiles, are observed with CB over LPB-processed specimen samples. © 2020, ASM International.
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    Effect of cryogenic grinding on fatigue life of additively manufactured maraging steel
    (MDPI AG, 2021) Balan, A.S.S.; Kannan, C.; Kumar, A.V.; Hariharan, H.; Pimenov, D.Y.; Giasin, K.; Nadolny, K.
    Additive manufacturing (AM) is replacing conventional manufacturing techniques due to its ability to manufacture complex structures with near?net shape and reduced material wastage. However, the poor surface integrity of the AM parts deteriorates the service life of the components. The AM parts should be subjected to post?processing treatment for improving surface integrity and fatigue life. In this research, maraging steel is printed using direct metal laser sintering (DMLS) process and the influence of grinding on the fatigue life of this additively manufactured material was investigated. For this purpose, the grinding experiments were performed under two different grinding environments such as dry and cryogenic conditions using a cubic boron nitride (CBN) grinding wheel. The results revealed that surface roughness could be reduced by about 87% under cryogenic condition over dry grinding. The fatigue tests carried out on the additive manufactured materials exposed a substantial increase of about 170% in their fatigue life when subjected to cryogenic grinding. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.
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    Mathematical modeling and optimization of tribological behaviour of Al 7075 based hybrid nanocomposites
    (SAGE Publications Ltd, 2021) Kannan, C.; Radhakrishnan, R.; Balan, A.S.S.
    Many industrial applications necessitate lightweight materials that possess better tribological behaviour. Whilst aluminium based nanocomposites are proposed owing to their lightness, their tribological characteristics must be improved which are dominantly influenced by the selection of reinforcements, manufacturing process and heat treatments. In this research, an aluminium hybrid nanocomposite is produced using a novel molten salt processing and subjected to different heat treatments. Their tribological behaviour is assessed under different operating conditions viz. load, sliding velocity and material condition of the pin. Regression models are formulated to predict the tribological behaviour of developed hybrid composite under different heat treatments. The most significant parameter and optimum level for each of these operating parameters are determined using analysis of variance, main and interaction plots and response surface methodology in the end. The integrated approach helps in deciding the optimum parameter setting for the development of nanocomposite with ameliorated tribological behaviour. Under the optimized conditions, the hybrid nanocomposite could able to reduce the wear resistance by about 63% and the coefficient of friction by 18.5% than unreinforced alloy. © IMechE 2020.
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    4D printed stereolithography printed plant-based sustainable polymers: Preliminary investigation and optimization
    (John Wiley and Sons Inc, 2021) Danish, M.; Vijay Anirudh, P.; Karunakaran, C.; Vasudevan, V.; Mathew, A.T.; Koziol, K.; Thakur, V.K.; Kannan, C.; Balan, A.S.S.
    The increasing demand for applying shape memory polymer to tissue culture and biomedical engineering has opened up research opportunities in the field of 4D Printing. The biocompatibility of the scaffolds as a culture medium resulted in the use of plant-based polymers to provide an ambient environment for the growth of cells. This research investigates the 4D printing of acrylated epoxidized soybean oil (AESO), a plant-based shape polymer. The objective of the present work is to establish the relationship between the 4D printing parameters (laser power frequency and print speed) and different properties of the printed material viz. tensile stress, surface roughness, wettability, recovery time, strain fixity and glass transition temperature. The maximum fixity was about 85%, while the recovery time as low as 1.6 s. The print parameters are optimized using regression modeling and multi-objective optimization techniques. The shape memory effect of the polymer is demonstrated by printing samples at the optimized conditions. Dynamic mechanical analysis is performed to evaluate the variation in the glass transition temperature of AESO at specific print parameters. The adoption of an optimal set of laser frequency and print speed is found to improve the properties of AESO, while built by micro stereolithography (micro-SLA). © 2021 Wiley Periodicals LLC.