Faculty Publications

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    Recast Layer Formation during Wire Electrical Discharge Machining of Titanium (Ti-Al6-V4) Alloy
    (Springer, 2021) Pramanik, A.; Basak, A.K.; Prakash, C.; Shankar, S.; Sharma, S.; Narendranath, S.
    Titanium alloys, in particularly Ti-6Al-4V alloy is used enormously in many high-tech sectors specially in aerospace industries due to its superior properties. Machining process (for example wire electrical discharge machining) to reshape this alloy affects the integrity of the newly generated surfaces. This experimental study has identified three affected layers using scanning electron microscopy on the cross section of the machined titanium (Ti-6Al-4V) alloy surface generated from wire electrical discharge machining (WEDM). This study also explained the formation mechanism of those three layers as no detail investigation is available in this area so far. It was found that the top flaky layers are formed due to the highest cooling rate at the outermost surface, which is induced due to the low thermal conductivity of the titanium alloy as well as the quenching effect because of the existence of dielectric. The recast layer is formed at a cooling rate lower than that at the outer surface, where the melted material is resolidified very quickly without having any grain boundaries. The heat-affected zone appears at a slightly different color, which does not melt but experience heat treatment during the machining process. © 2021, ASM International.
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    Liquid-infused surfaces for mitigation of corrosion and inorganic scaling
    (Elsevier Ltd, 2024) Yandapalli, A.V.V.R.P.; A, S.; Kuravi, S.; Kota, K.
    In this study, the effectiveness of a binary surface (BiS), a type of liquid-infused surface, in enhancing corrosion resistance and mitigating inorganic fouling without compromising heat exchange efficiency is demonstrated. An Ultra-Omniphilic Surface (UOS) was initially prepared from a plain aluminum alloy surface (PS) using a bulk micro-manufacturing approach. Subsequently, the sub-surface micro/nanocavities of UOS were infused with a liquid lubricant to create BiS, characterized by two distinct superficial phases — solid islands and liquid puddles. Lab-scale experiments in a simulated brackish water environment revealed that BiS outperformed both PS and UOS in inhibiting scaling and corrosion. The BiS exhibited nearly 50% less mass gain due to mineral deposition than PS and UOS. Moreover, corrosion rates obtained from electrochemical and immersion tests indicated significantly slower metal degradation on BiS compared to PS and UOS. Furthermore, BiS displayed superior heat exchange capabilities, collecting approximately 73% and 44% more condensate than PS and UOS, respectively. This enhancement is attributed to well-distributed liquid puddles on BiS, promoting a smooth, defect-free surface that reduces foulant adhesion and shields the underlying metal from corrosion, while also enhancing two-phase heat transfer activity. © 2024 Elsevier Ltd