Browsing by Author "Vinayak, V.R."

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A Review on Surface Engineering Perspective of Metallic Implants for Orthopaedic Applications
(Springer, 2021) Jambagi, S.C.; Vinayak, V.R.
Orthopaedic metallic implant design is expected to meet two critical challenges—biocompatibility and mechanical strength. According to a survey conducted in 2017, the global market of implants will grow by ~46% by 2025. Researchers have been trying to alleviate the problems of these implants, namely, biocompatibility, microbial invasion, bio-inertness, corrosion, and wear. Surface modification techniques that operate at low temperature and diffusion-based processes are preferred to circumvent the problems. These methods include thermochemical (carburizing, nitriding, etc.), electrochemical processes (electrochemical deposition, chrome plating, etc.), and ion implantation. This review presents the significance of these methods while meeting various challenges, such as wear, biocompatibility, and corrosion. The implants reviewed are stainless steel, Co-Cr alloys, titanium alloys, and magnesium alloys. Finally, the friction-stir process, another low-temperature process, has been reviewed for Mg and its alloys. © 2021, The Minerals, Metals & Materials Society.
Comparative analysis of flipped and overlapped microwave sintered plus friction stir processed in-situ Al-Cu composites
(Springer Nature, 2024) Vinayak, V.R.; Bajakke, P.A.; Jambagi, S.C.; Bhajantri, V.; Deshpande, A.S.
The in-situ Al-Cu composites were fabricated with Cu content more than the solubility limit (5.65%) and the critical composition of an Al-Cu alloy (4.6%). A powder metallurgy route with state-of-the-art microwave sintering and friction stir process with overlapped and flipped conditions was attempted. The overlapped friction stir resulted in a minimum area of nugget region, unidirectional material mixing, high heat input in successive passes, and brittleness in the material. This accounted for the material to exhibit high strength with low ductility. Whereas flipped friction stir leads to a maximum area of stir zone, bidirectional material mixing, and similar thermal cycles in individual passes and avoids excessive heating. This facilitated the material to possess maximum strength by retaining ductility. The newly developed in-situ Al-Cu composite material (with Cu wt% in ranges of 8–12) possesses equivalent strength, ductility, electrical conductivity, and rate of corrosion compared to copper. Notably, these attributes, combined with its cost-effectiveness, position this material as a promising alternative to copper conductors in electrical applications. From the present investigation, it is strongly recommended to choose a flipped friction stir for better properties. © Qatar University and Springer Nature Switzerland AG 2024.
Corrosion behavior of novel AA1050/ZnO surface composite: A potential material for ship hull
(Elsevier B.V., 2020) Bajakke, P.A.; Vinayak, V.R.; Jambagi, S.C.; Deshpande, A.S.
Friction stir processing is one of the effective surface treatments which was employed to process the AA1050 sheets in bare and reinforced condition. The primary objective of the investigation was to expand the applications of AA1050 as a ship hull element in shipbuilding with the least corrosion rate to withstand the harsh marine environment. The base material processed with a rotational speed of 1200 rpm resulted in the highest corrosion rate of 0.173622 mpy. The formation of Al-Fe intermetallic phases was responsible for pitting corrosion. Further, processing by embedding zinc oxide with a rotational speed of 1000 rpm exhibited ~6.68 times improvement in corrosion resistance compared to as-received material. The corrosion rate was found to be 0.003390 mpy. The Al2O3 passive film hinders the initiation and propagation of pits. This study coins a novel composite material and future investigations are emphasized on the same lines. © 2020 Elsevier B.V.
Friction Stir Processing: An Emerging Surface Engineering Technique
(Springer Science and Business Media B.V., 2020) Bajakke, P.A.; Jambagi, S.C.; Vinayak, V.R.; Deshpande, A.S.
Surface modification technologies impart improved surface properties without affecting the bulk properties of the material. The properties could be mechanical, electrical or thermal properties. Until recent past, thermal spray techniques, namely, plasma spraying, high-velocity oxy-fuel coatings and many others widely used for these applications. Friction stir processing (FSP) is a relatively newer technique that uses friction (between two surfaces) as a heat source to form a surface composite on the base alloy. This solid-state process not only refines the given structure but also disperses the reinforcements well within matrix alloy to enhance the surface properties. FSP was earlier employed to low melting point alloys such as aluminum and magnesium-base alloys, but now, with the recent development in tool geometry and tool materials, it can even be effectively used for high melting point alloys like steel and titanium-based alloys. Several process parameters seem to affect temperature and dispersion of reinforcements at the surface. They include rotational speed and traverse speed of the tool, number of passes, cooling medium and the tool geometry. Among these, rotation speed and traversing speed of tool seem to greatly affect the temperature distribution in the plasticized zone formed at the surface. This temperature, in turn, affects the grain refinement and dispersion of reinforcement particles. The present chapter summarizes the effect of these parameters. This chapter also reviews the latest developments in the tool material and its design. Further, their role in augmenting the base alloy properties is also discussed. High hardness, high fracture toughness, chemical inertness and high-temperature strength are few desirable properties of a tool to be used for FSP. In the end, the applicability of FSP as a surface modification technique has been assessed. © 2020, Springer Nature Switzerland AG.
Investigating Mechanical and Corrosion Behavior of Plain and Reinforced AA1050 Sheets Fabricated by Friction Stir Processing
(Springer, 2020) Vinayak, V.R.; Bajakke, P.A.; Jambagi, S.C.; Chavana, C.; Deshpande, A.S.
The present investigations help in improving the bendability and corrosion resistance of AA1050 rolled sheets by selective friction stirring. The processing of AA1050 with a tapered square pin at a tool rotation speed of 1200 rpm yielded the highest strain of 0.345 at ultimate tensile strength compared with 0.054 in as-received material. The identified processing conditions produced an ultimate tensile strength of 89.23 MPa with a toughness of 34.451 × 106 J/m3 and a lower corrosion rate with Icorr of 0.324 × 10?6 A/cm2. Further, processing with a simple tapered circular pin resulted in maximum ultimate tensile strength of 102 MPa with a toughness of 33.990 × 106 J/m3. However, it came at the expense of least resistance to corrosion with Icorr of 4.813 × 10?6 A/cm2. Consequently, the addition of zinc oxide during friction stirring showed a remarkable improvement in corrosion resistance with Icorr of 0.094 × 10?6 A/cm2. Future studies are planned on these lines. © 2020, The Minerals, Metals & Materials Society.
Synthesis and Characterization of PVDF/Graphene Nanocomposite Membrane for Water Treatment Applications
(Trans Tech Publications Ltd, 2022) Rao, S.; Avinash, A.; As, S.; Hegde, C.; Isloor, A.M.; Vinayak, V.R.
Membrane technology advancement has gained momentous consideration around the globe because of their appealing highlights, such as effectiveness, low expenses, and effective solutions for longstanding issues in alchemical industries. This study expected to incorporate graphene nanoparticles into Polyvinylidene difluoride (PVDF) to form nanofiltration (NF) layers using DMF (Dimethyl formamide) as solvent via DIPS (diffusion induced phase separation) technique. PVDF polymer membrane performances with varied percent (1 – 6% wt.) of graphene concentrations are studied with Infrared spectral, water uptake, water contact angle, and ion rejection measurements. Scanning electron microscope (SEM) analysis showed that the pore size is often regulated by incorporating graphene nanoparticles (80-90 nm) as compared to PVDF membranes. The PVDF membranes exhibited a relative increase in the contact angle from PVDF to PVDF-G6%, i.e., 50.3° to 63.46 ± .3, thus, showing a relative increase in hydrophobicity. The higher percent of graphene (> 6% by wt.) results in nano-particle accumulation that showed the performances of PVDF/graphene rejection possessing relatively the same results. The results confirmed that the prepared membranes possess an excellent ability to treat wastewater. © 2022 Trans Tech Publications Ltd, Switzerland.