Journal Articles
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Item 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.Item Bioactive surface modifications through thermally sprayed hydroxyapatite composite coatings: a review of selective reinforcements(Royal Society of Chemistry, 2022) Jagadeeshanayaka, N.; Awasthi, S.; Jambagi, S.C.; Srivastava, C.Hydroxyapatite (HA) has been an excellent replacement for the natural bone in orthopedic applications owing to its close resemblance to the bone properties; however, it is brittle and has low strength. Surface modification techniques have been able to allay such mineral issues by depositing on substrate. These methods, being economical, impart mechanical strength without compromising biocompatibility. In this review article, the discussion is confined to plasma spray (high temperature) and other low temperature surface modification techniques: high-velocity oxy-fuel (HVOF) and cold spray. The processing temperature seems to significantly affect the performance of implants deposited with HA. Monolithic HA may not add enough strength to the bioimplants. Hence, this review discusses selective reinforcements to HA and their roles in enhancing the properties. Herein, a variety of selective reinforcements are discussed, such as carbon allotropes: graphene, carbon nanotubes, and nano diamond; metallic materials: Ag, Sr, Mg, and Ti; ceramic materials: Al2O3, SiO2, ZrO2, and TiO2; multi-materials: Al2O3-CNT/HA, Al2O3-TiO2/HA and others; and functionally graded composites: HA, 20 and 50 wt% Ti-6Al-4V/HA layered coating. Most of these reinforcements could not trade-off between biocompatibility and strength. The detailed in vitro and in vivo studies are still lacking. The literature on the relative effectiveness of these reinforcements is scanty, while the interface between HA coating and reinforcements is seldom explored. This review presents the suitability of thermal spray techniques based on the microstructure, mechanical, and biological properties. Therefore, it is envisaged that the present review can intrigue future researchers to understand the scope of surface coatings in achieving the better performance of implants at clinical trials. © 2022 The Royal Society of Chemistry.Item Scratch adhesion strength of plasma sprayed carbon nanotube reinforced ceramic coatings(Elsevier Ltd, 2017) Jambagi, S.C.This report investigates the effect of both mechanical and thermal properties of Carbon nanotube (CNT) on scratch adhesion strength of ceramic coatings. Micro sized alumina and titania with 1 wt% CNT powders were prepared by three routes: dry/wet milling (with alcohol) and heterocoagulation. First, degree of CNT dispersion in the coatings was analysed. Heterocoagulated coatings displayed homogeneous dispersion of CNT. Next, the effect of homogeneous dispersion on phase transformation was studied. Higher thermal conductivity of CNT and its degree of dispersion seemed to affect the melting of powders and thus the phase transformations in the coatings. A higher fraction of stable phase was detected in the coatings. In addition, CNT/ceramic interface was analysed for the reaction layer. A stable phase layer was found covering the entire CNT surface, protecting it from thermal degradation. Finally, the scratch adhesion strength was quantified for both CNT reinforced and unreinforced coatings. The scratch resistance of heterocoagulated coatings improved by ?36–176%. Improvement in strength was attributed to: a) a higher stable phase fraction in the coatings, b) Strong wettability at CNT/ceramic interface, c) improvement in elastic moduli of the coatings has also led to the improvement in the work of adhesion of the coatings, and d) a toughening mechanism, CNT bridging. © 2017 Elsevier B.V.Item 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.Item 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.Item Influence of carbon nanotube reinforcement on the heat transfer coefficient, microstructure, and mechanical properties of a die cast Al-7Si-0.35Mg alloy(Elsevier Ltd, 2021) Usef, A.P.; Bhajantri, V.; Kannoth, V.; Jambagi, S.C.Al-7Si-0.35Mg or A356 alloy is most widely used in aircraft and automobile industries owing to its high strength to weight ratio. This alloy has been reinforced with a 1 wt% carbon nanotube (CNT) to improve its properties in this investigation. First, A356/1 wt% CNT powders were ball milled in the presence of ethanol and subsequently consolidated using gravity die casting. Ball milling was effective in achieving homogeneous dispersion of CNT. The microstructural study revealed the segregation of the Al4C3 phase at the grain boundary. This mechanism is known as grain boundary precipitation. Also, the grain size has decreased by ~44%. Next, the casting-die interfacial heat transfer coefficient (IHTC) has been evaluated using Beck's inverse heat transfer algorithm. With the reinforcement, the IHTC has increased by ~2.5%, which indicates the rise in heat transfer rate during solidification. Then, the experimental and theoretical tensile properties of A356 were correlated using simulation software. The experimental results showed the synergistic effect of grain size, Al4C3, and IHTC improving yield strength by ~19.8%, ultimate tensile strength by ~14.13%, elongation by 7%, and hardness ~22%. Therefore, a meagre 1 wt% CNT has improved the heat transfer rate of the melt as indicated by IHTC values. This effect was further corroborated by evaluating the thermal conductivity of the sample. The thermal conductivity has improved by 10% that resulted in finer grain size of the sample. Therefore, such reinforced alloys are expected to display higher strength demanded in various industrial applications. © 2021Item Improvement in Slurry Erosion and Corrosion Resistance of Plasma-Sprayed Fly Ash Coatings for Marine Applications(American Chemical Society, 2022) Chavana, N.; Bhajantri F, V.; Jambagi, S.C.Fly ash (FA), a multicompound mineral, is an industrial waste produced during coal burning in thermal power stations. It has been regarded as the most environmentally hazardous material. Furthermore, handling FA has been a significant challenge for many developing countries. Therefore, researchers have been exhorted to enhance its usage to counter its handling issues. FA is enriched with mullite, silica, and alumina. Having such mineralogy, FA can be envisaged as a promising candidate for combating erosion and corrosion in marine environments. With this motivation, the research aims to deposit as-received FA using the plasma-spraying technique onto a marine-grade steel substrate without additives and assess the performance of such coatings for erosion and corrosion properties. The coating has exhibited more than 100% improvement in microhardness. The erosion resistance was improved by ∼11% compared to that of the uncoated sample, which is attributed to the hardness to elastic modulus ratio (H/E) and its unique mineralogy. The minor improvement in erosion resistance was attributed to the coating's poor fracture toughness. The erosion study shows that slurry concentration and rotational speeds were the most influential parameters. The scar depth was significantly shallower for FA-coated samples. The corrosion resistance has improved only by ∼13.49%, owing to the porous nature of the coating. Therefore, such coatings with appropriate improvements in their properties are expected to assuage both environmental and industrial challenges. © 2022 The Authors. Published by American Chemical Society.Item Factors influencing powders’ flowability and favorable phases like crystalline (Mullite and quartz) and amorphous phases of plasma-sprayed fly ash coatings suitable for marine and offshore applications(Elsevier B.V., 2023) Bhajantri, V.F.; Jambagi, S.C.Due to its rich mineralogy, fly ash (FA), an industrial waste, has been used to combat erosive, corrosive environments. Powder flowability dictates coating properties. In this investigation, raw FA powder was obtained from a thermal power plant and sieved in various sizes to assess their flowability. Powder's physical characteristics, such as specific surface area, Blaine's fineness number, and bulk density, were determined, and their influence on powder flowability was analyzed. Of these properties, bulk density affects more. Rietveld refinement was performed on the powder to quantify the phases. The powders had 45.08 ± 11.38 amorphous and 11.00 ± 2.76 % of mullite phases. Later, alumina was added between 10 and 50 wt% to FA, and samples were subjected to high-temperature X-ray diffraction at 1150 °C. A ∼32.27% rise in Mullite content was observed for 50 wt% alumina, with ∼119% decrease in the amorphous phase. Finally, one set of FA without additives coating was plasma sprayed onto a marine-grade steel substrate. The coating showed ∼17.31 ± 0.6% of mullite and ∼69.43 ± 0.6 % of the amorphous phase, with decent Mechanical properties. Therefore, 50 wt% alumina in FA powder has improved the mullite phase, bulk density (43%), and flowability by decreasing the amorphous phase content. © 2023 Society of Powder Technology JapanItem An Investigation into the Relative Efficacy of High-Velocity Air-Fuel-Sprayed Hydroxyapatite Implants Based on the Crystallinity Index, Residual Stress, Wear, and In-Flight Powder Particle Behavior(American Chemical Society, 2023) Jagadeeshanayaka, N.; Kele, S.N.; Jambagi, S.C.Due to its resemblance to the bone, hydroxyapatite (HA) has been widely used for bioactive surface modification of orthopedic implants. However, it undergoes significant thermal decomposition and phase transformations at a high operating temperature, leading to premature implant failure. This investigation uses high-velocity air-fuel (HVAF) spray, an emerging low-temperature thermal spray technique, to deposit HA over the Ti-6Al-4V substrate. Coating characteristics, such as the crystallinity index and phase analysis, were measured using X-ray diffraction, Raman analysis, and Fourier transform infrared spectroscopy, residual stress using the sin2ψ method, and tribological performance by a fretting wear test. The coating retained an over 90% crystallinity index, a crystallite size of 41.04 nm, a compressive residual stress of −229 ± 34.5 MPa, and a wear rate of 1.532 × 10-3 mm3 N-1 m-1. Computational in-flight particle traits of HA particles (5 to 60 μm) were analyzed using computational fluid dynamics; it showed that 90% of particles were deposited at a 700 to 1000 m/s velocity and a 900 to 1450 K temperature with a 2.1 ms mean residence time. In-flight particle oxidation was minimized, and particle impact deformation was maximized, which caused severe plastic deformation, forming crystalline, compressive residual stressed coatings. The thermal decomposition model of low-temperature HVAF-sprayed HA particles helped to understand the implants’ crystallinity index, residual stress, and tribological characteristics. Hence, this experimental and computational analysis shows that the HVAF process can be a promising candidate for biomedical applications for having strong and durable implants. © 2023 American Chemical Society.Item Effect of Surface Chemistry on Hemolysis, Thrombogenicity, and Toxicity of Carbon Nanotube Doped Thermally Sprayed Hydroxyapatite Implants(American Chemical Society, 2024) Shankar, D.; Jambagi, S.C.; Gowda, N.; Lakshmi, K.S.; Jayanthi, K.J.; Chaudhary, V.K.Assessing blood compatibility is crucial before in vivo procedures and is considered more reliable than many in vitro tests. This study examines the physiochemical properties and blood compatibility of bioactive powders ((0.5-2 wt % carbon nanotube (CNT)/alumina)-20 wt %)) produced through a heterocoagulation colloidal technique followed by ball milling with hydroxyapatite (HAp). The 1 wt % CNT composite demonstrated a surface charge ∼5 times higher than HAp at pH 7.4, with a value of −11 mV compared to −2 mV. This increase in electrostatic charge is desirable for achieving hemocompatibility, as evidenced by a range of blood compatibility assessments, including hemolysis, blood clotting, platelet adhesion, platelet activation, and coagulation assays (prothrombin time (PT) and activated partial thrombin time (aPTT)). The 1 wt % CNT composite exhibited hemolysis ranging from 2 to 7%, indicating its hemocompatibility. In the blood clot investigation, the absorbance values for 1-2 wt % CNT samples were 0.927 ± 0.038 and 1.184 ± 0.128, respectively, indicating their nonthrombogenicity. Additionally, the percentage of platelet adhered on the 1 wt % CNT sample (∼5.67%) showed a ∼2.5-fold decrement compared to the clinically used negative control, polypropylene (∼13.73%). The PT and aPTT experiments showed no difference in the coagulation time for CNT samples even at higher concentrations, unlike HAC2 (80 mg). In conclusion, the 1 wt % CNT sample was nontoxic to human blood, making it more hemocompatible, nonhemolytic, and nonthrombogenic than other samples. This reliable study reduces the need for additional in vitro and in vivo studies before clinical trials, saving time and cost. © 2024 American Chemical Society.