316L SS Substrate Research Articles

Investigation and In Vitro Studies of a ZrO2/g‐C3N4 Composite Coated on 316L Stainless Steel for Biomedical Applications

ABSTRACTThe advancement of smart coatings for bioimplants has yielded a combination of biocompatibility and corrosion resistance. 316L stainless steel (316LSS) is a commonly used commercial implant, but it has limitations in biocompatibility and durability, which hinders the widespread utilization of 316LSS alloys. In this study, the 316LSS alloy is coated with a mixture of zirconium dioxide (ZrO2), prepared using the sol–gel method, and graphitic carbon nitride (g‐C3N4), synthesized by thermal polymerization. XRD and Raman analyses confirmed the crystal structure and purity of the synthesized samples. The corrosion resistance property was assessed using OCP, POL, and PEIS. The findings demonstrate that the ZrO2/g‐C3N4‐coated 316LSS shows significantly enhanced corrosion resistance and biocompatibility in a simulated body fluid. The in vitro bioactivity test reveals that the ZrO2/g‐C3N4 coating leads to the formation of an apatite layer over the surface of 316LSS. The elemental composition of the HAP deposition was confirmed by Raman analysis. The results suggested that the ZrO2/g‐C3N4–coated 316LSS substrate is a promising material for use in biomedical applications.

Ti3C2Tx MXene deposition: A simple surface engineering technique for dual enhancement of biological functions for nonbearing applications

Implant-associated complications, such as infection and poor osseointegration, present significant challenges in the field of biomedical implants. To address these issues, it is crucial to develop implant surfaces that possess both bacteriostatic and osteoconductive properties. In recent years, the field of surface modification for metallic substrates using two-dimensional materials has emerged as a highly promising strategy to enhance their biological properties. Among these materials, MXenes stand out as an excellent candidate for surface modifications due to their unique properties, such as biocompatibility, high specific surface area, and tunable chemical composition. In the present study, we introduce a simple deposition method of Ti3C2Tx MXene films on SS316L substrates to improve surface-cell interactions. The differentiation study demonstrated the alkaline phosphatase (ALP) enzyme activity on Ti3C2Tx-MXene-coated samples without osteogenic medium compared to uncoated samples in both, basic and osteogenic media. Moreover, the bacteriostatic character of the deposited MXene-coatings was confirmed against Gram-positive Staphylococcus aureus as well as Gram-negative Escherichia coli bacteria. The improved stimulation of both cell osteogenic differentiation and distinctive antimicrobial features triggered by Ti3C2Tx-MXene-coatings emphasizes their great potential as implant surface modifiers to improve integration and reduce the risk of infection in various biomedical applications.

Impact of Surface Pretreatment on the Corrosion Resistance and Adhesion of Thin Film Coating on SS316L Bipolar Plates for Proton-Exchange Membrane Fuel Cell Applications.

Coated SS316L is a potential alternative to the graphite bipolar plates (BPPs) used in proton-exchange membrane fuel cells (PEMFCs) owing to their low manufacturing cost and machinability. Due to their susceptibility to corrosion and passivation, which increases PEMFC ohmic resistance, protective and conductive coatings on SS316L have been developed. However, coating adhesion is one of the challenges in the harsh acidic environment of PEMFCs, affecting the performance and durability of BPPs. This study compares mechanical polishing and the frequently adopted chemical etchants for SS316L: Adler's, V2A, and Carpenter's etchant with different etching durations and their impact on the wettability, adhesion, and corrosion resistance of a Nb-coated SS316L substrate. Contact angle measurements and laser microscopy revealed that all etching treatments increased the hydrophobicity and surface roughness of SS316L substrates. Ex situ potentiodynamic and potentiostatic polarization tests and interfacial contact resistance analysis revealed high corrosion resistance, interfacial conductivity, and adhesion of the Nb-coated SS316L substrate pretreated with V2A (7 min) and Adler's (3 min) etchant. Increased hydrophobicity (contact angle = 101°) and surface roughness (Ra = 74 nm) achieved using V2A etchant led to the lowest corrosion rate (3.3 µA.cm-2) and interfacial resistance (15.4 mΩ.cm2). This study established pretreatment with V2A etchant (a solution of HNO3, HCl, and DI water (1:9:23 mole ratio)) as a promising approach for improving the longevity, electrochemical stability, and efficiency of the coated SS316L BPPs for PEMFC application.

Conductivity and corrosion resistance of TiSiC/MeN multilayer films

TiSiC/MeN (where Me represents Zr, Ti, and Cr) multilayer films were deposited onto 316LSS substrates for proton exchange membrane fuel cells via magnetron sputtering. A comparative investigation of the microstructures and corrosion resistances of the films was conducted. The results indicate that the incorporation of the MeN interlayers interrupts the continuous growth of the columnar TiSiC layer. The TiSiC/MeN multilayer coated 316LSS exhibits better resistance to corrosion and higher electrical conductivity compared to the TiSiC monolayer. The film porosity dominates the corrosion resistance while the electrical conductivity depends on both the phase structure and oxygen concentrations of the films. The multilayer structure suppresses ion diffusion in the etchant solution and decreases the film porosity. However, interfacial delamination caused by the interaction of the solution with the substrate produces the failure of the monolayer TiSiC.

Effect of TiC grain size on corrosion behaviors of Ti-Si-C nanocomposite coatings fabricated by heterogeneous targets high-power impulse magnetron sputtering

Ti-Si-C coatings with different carbon contents were prepared on SS316L substrates by heterogeneous targets high-power impulse magnetron sputtering with a repetitive C and TiSi deposition. Various tests were employed to analyze the microstructure, anti-corrosion properties in a simulated proton exchange membrane fuel cells (PEMFC) environment and interfacial conductivity of the coatings. Results indicated that the Ti-Si-C coating possessed a typical nanocomposite structure of TiC nanocrystals embedded in amorphous carbon matrix. With the increase of the carbon content, the grain size of TiC nanocrystals was reduced gradually. Electrochemical measurements revealed that a proper decrease of TiC grain size led to an enhanced corrosion resistance of the as-deposited coating. The smallest interfacial contact resistance and corrosion rate of the Ti-Si-C coating in the simulated PEMFC solution reached 5.07 mΩ cm2 and 5.93E-07 A/cm2, respectively. This improvement could be attributed to the formation of a dense and continuous passivation layer composed of Ti2O3 and SiO2 on the top surface of the coating.

Fabrication of TiO2 Nanoparticle Coating on Stainless Steel 316L and Its Assessment for Orthopaedic Applications

The study aims to investigate the efficacy of titanium dioxide (TiO2) nanoparticle coating on stainless steel 316L (SS 316L) orthopaedic implants to enhance their biocompatibility, osseointegration, and durability. The TiO2 nanoparticles were synthesized via the hydrothermal method and extensively characterized for composition, crystallinity, and morphology using techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) with energy dispersive X-ray analysis (EDX), corroborated by elemental mapping. SEM and XRD analyses revealed the synthesized nanoparticles have a spherical shape and an average size of approximately 23 nanometres. The synthesized TiO2 nanoparticles were uniformly coated on SS 316L substrates using the spin coating technique, as confirmed by SEM images. Cell viability of the synthesized TiO2 nanoparticles, as well as uncoated and TiO2 nanoparticle-coated SS 316L substrates, was evaluated using the MTT (3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide) assay against the NIH-3T3 mouse embryonic fibroblast cell line. The results demonstrated that the TiO2 nanoparticle-coated SS 316L substrate showed a significant increase of 22.87% in cell viability as compared to the uncoated SS 316L substrate. A ball-on-disc tribometer was employed to assess wear and friction resistance at various speeds, viz., 150 rpm, 300 rpm, and 450 rpm, under 30N load conditions for five minutes. The results collectively indicate a substantial improvement in the performance of TiO2 nanoparticle-coated SS 316L substrates for orthopaedic applications.

Corrosion behavior of Ti–Pt-coated stainless steel for bipolar plates in polymer electrolyte membranes under water electrolysis conditions

In this study, the corrosion behavior and degradation mechanism of Ti–Pt-coated stainless steel bipolar plates were investigated through electrochemical tests and surface analysis in a polymer electrolyte membrane water electrolysis (PEMWE) operating environment. The coated bipolar plate has a corrosion current density of only 1.68 × 10−8 A/cm2, which is an order of magnitude lower than that of the bare SS316L substrate (1.94 × 10−7 A/cm2), indicating that its corrosion resistance is superior to that of bare SS316L substrate. However, in the PEMWE operating environment, the protection efficiency of the coating and the corrosion resistance of the coated bipolar plate decreased. The degradation of the coated bipolar plate can be attributed to electrolyte penetration into the blistering areas of the coating layer with micro voids. Defects in the coating layer occur because of the pressure of oxygen gas generated within the coating layer under high-potential conditions, thereby exposing the substrate to the electrolyte and corrosion.

Surface Evaluation of Tricalcium Phosphate Bioceramic Coating on SS-316L by Electrophoretic Deposition

The development of orthopedic implant materials has become an important topic of discussion lately. The SS-316L alloy is widely used as an implant material due to its relatively low cost, corrosion resistance, and ease of production. However, metal alloys, especially SS-316L, are prone to ion release into the blood over time. Therefore, TCP or tricalcium phosphate [Ca3(PO4)2] is needed to coat the surface of SS-316L, preventing ion release into the blood and enhancing the biocompatibility of the implant material. In this study, TCP coating was applied to the SS-316L substrate using the electrophoretic deposition technique. The influence of deposition time on changes in microstructure and mechanical properties is the main focus of this study. The results of the coating technique indicate that the deposition yield increases with the deposition time. Morphological testing results show that increasing deposition time improves coating quality by increasing the thickness of the coating layer and preventing layer peeling. The coating process also reveals the accumulation of layers in certain areas and the formation of thin layers in other regions. A deposition time of 30 minutes results in a coating thickness ranging from 48.7 to 57.9 µm. Hardness testing, conducted with indentation loads of 50, 100, and 300 gf, indicates that longer deposition times and higher indentation loads during hardness testing result in reduced material hardness.

Microstructural Evolution and Wear Resistance of Surface Alloyed AISI 316L Stainless Steel with Equi-atomic CoCrFeMnTi by Continuous Wave Diode Laser

In this investigation, a multicomponent alloyed surface was developed on AISI 316L stainless steel (AISI 316L SS) substrate by melting it with a fiber coupled diode laser having 3.6 mm beam diameter (using argon as shrouding gas) along with simultaneous melting of equiatomic pre-mixed elemental powders of cobalt (Co), chromium (Cr), iron (Fe), manganese (Mn) and titanium (Ti) (high entropy alloy). The process parameters used in the experiment were laser power (1800–2200 W) and scan speed (6 mm/sec to 8 mm/sec). Following laser surface alloying (LSA) a detailed microstructural characterization of the surface and evaluation of surface mechanical properties (micro/nano hardness, Young’s modulus and wear resistance) were undertaken. Due to LSA there is formation of near eutectic microstructure consisting of FCC and BCC phase mixtures along with the precipitates of Fe2Ti randomly distributed in the microstructure which was confirmed by X-ray diffraction (XRD) and electron back scattered diffraction (EBSD) analysis. There is an increase in microhardness in the processed zone from 180 VHN (of as received AISI 316L SS) to 309–650 VHN. In addition, there is an increase in Young’s modulus from 208 GPa for as received AISI 316L SS to 228–301 GPa for laser surface alloyed zone. The wear resistance (against WC ball in fretting wear mode) property of AISI 316L SS substrate after LSA was superior to the substrate. The wear mechanism was established.

Impact of hydroxyapatite (HaP) nano particle on the morphology, thickness, and adhesion strength of electrophoretic ZnO/HaP composite coated SS316L

The present study explores how the hydroxyapatite (HAp) nanoparticles could influence the surface properties of the electrophoretic ZnO/HAp composite coating on stainless steel SS316L substrate. Various weight dispersion of HAp nanoparticles (1.0 g/l, and 1.5 g/l) and applied voltage of 40 V and 50 V were applied during the deposition of the composite coatings. The ZnO/HAp composite coatings were characterized using field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), contact angle, Vicker's hardness, surface profilometer, scratch tester, and atomic force microscopy (AFM) analyser. The composite coating with 1.5 g/l of HAp with an applied voltage of 40 V has exhibited a homogeneous distribution with higher coating thickness of 11.17 μm, and importantly, low porosity (< 0.94 %, which is <1 %). Crystal sizes increases from 19.2 to 28 nm when the applied voltage and weight dispersion of HAp is increased. FTIR analysis confirmed the higher deposition of polymeric groups in ZnO/HAp composite coatings irrespective to the weight dispersion and voltages. Furthermore, the higher dispersion of HAp has decreased the surface energy and roughness with optimum coating hardness. However, the better adhesion strength was achieved in comparison to the other composite coatings. The failures that occurred during the scratch test were further detailed in this study using the AFM and SEM.

Implications of FCC and HCP cobalt phases on wear performance of weld deposited cobalt-based coating

SS316L possesses comparatively low wear and abrasion resistance properties and thus needs proper surface modification to sustain under severe industrial applications. Cobalt-based Stellite 6, a suitable coating for such applications, contains 4–5 % of tungsten that provides solid solution strengthening to the cobalt-based matrix, due to which it shows good wear resistance in abnormal working conditions. Stellite 6 is dominated by face-centered cubic (FCC) and hexagonal close packed (HCP) cobalt along with different carbide phases such as M7C3, M23C6, MC and M6C where M is Cr, W, Mo, Co and Fe. Weld deposited cobalt-based Stellite 6 coating on SS316L substrate, contains FCC structure as primary phases. Pure cobalt contains a stable HCP phase at temperature below 417 °C and FCC phase at and above 417 °C up to melting point of pure cobalt i.e., 1495 °C. Under the frictional stresses caused during wear test, impact more on FCC cobalt than HCP cobalt due to the high slip system of FCC. Because of this, FCC cobalt underwent through high wear losses compared to HCP cobalt in cobalt-based coating. Present study revealed that, high wear losses are seen in samples where FCC cobalt phases are dominant. The observed mechanism by SEM shows abrasive wear in which material removal takes place by ploughing, micro cutting and indentation. The targeted industrial applications where such wear losses are supposed to happen includes slurry transportation applications such as pipes, sea engineering components, submersible pumps, control valves.

Bacterial and corrosion resistance of polytetrafluoroethylene-silver composite coatings by magnetron sputtering

Titanium alloy and stainless steel implants have been widely applied in orthopedics. However, harmful ions released from implant corrosion caused by human body fluids and bacterial infections may inhibit patients’ recovery. In this work, a polytetrafluoroethylene-silver composite coating was prepared by RF unbalanced magnetron sputtering to improve the bacterial and corrosion resistance of the SS316L. The removal rates of the composite coatings for Escherichia coli and Staphylococcus aureus reached 97.27% and 99.99%, respectively. The contact angle of 131.5° and fluorescence staining experiments show that the composite coating has an antiadhesive effect on bacteria and less cytotoxicity against osteoblasts. The corrosion voltage of the composite coating was much higher than that of the control SS316L substrate, and the corrosion current density was reduced to 1/3, implying the enhancement of the corrosion resistance of the SS316L substrate.

Ensuing the formation of photocatalytic TiO2/Fe2O3 nanocomposite from heat treatment of electrophoretically deposited TiO2 films on stainless steel

In this study, thermal transformations in electrophoreticlly coated TiO2 coatings on SS-316L substrate were investigated. Such films were previously employed for antibcaterial purposes, however their heat-treatment at 900 °C resulted in an unexpected transformation in the film color. This study was designed to trace back the origin of such optical transformation in the TiO2 film that was expected to be whitish in its outlook, however it became brownish at elevated temperature, indicating an exploitable characteristics of visible light absorbance. The films were carefully transformed to particles by subsequently applying scratching/ball milling method and characterized through various materials’ characterization tools including but not limited to SEM-(EDS), XRD, alongside characteristic characterizations such as TGA, UV-Vis and EIS for elucidating thermal, optical and electrochemical behavior respectively of particles obtained from pristine (TiO2) and heat-treated films (termed as TFNC) owing to the transformation of TiO2 to TNFC (i.e. TiO2/Fe2O3) nanocomposite. TFNC exhibited decreased band gap from 3.2 eV to 2.86 eV and consequently improved photocatalytic activity. The TFNC degraded 50% Rhodamine B dye under visible light, while pure TiO2 degraded only 13%, which was credited to the formation of Fe2O3 particles inside TiO2 film. It was estimated that the Fe-element was capable to diffuse inside such TiO2 film and resulted the formation of TFNC at ≥ 900°C. The evolution of visible light dependent photocatalytic performance in TFNC was credited to the lowering of bandgap and enhanced electron-hole generation as investigated by EIS.

Revealing bactericidal events on graphene oxide nano films deposited on metal implant surfaces.

At the time when pathogens are developing robust resistance to antibiotics, the demand for implant surfaces with microbe-killing capabilities has significantly risen. To achieve this goal, profound understanding of the underlying mechanisms is crucial. Our study demonstrates that graphene oxide (GO) nano films deposited on stainless steel (SS316L) exhibit superior antibacterial features. The physicochemical properties of GO itself play a pivotal role in influencing biological events and their diversity may account for the contradictory results reported elsewhere. However, essential properties of GO coatings, such as oxygen content and the resulting electrical conductivity, have been overlooked so far. We hypothesize that the surface potential and electrical resistance of the oxygen content in the GO-nano films may induce bacteria-killing events on conductive metallic substrates. In our study, the GO applied contains 52 wt% of oxygen, and thus exhibits insulating properties. When deposited as a nano film on an electrically conducting steel substrate, GO flakes generate a Schottky barrier at the interface. This barrier, consequently, impedes the transfer of electrons to the underlying conductive substrate. As a result, this creates reactive oxygen species (ROS), leading to bacterial death. We confirmed the presence of GO coatings and their hydrolytic stability by using X-ray photoelectron spectroscopy (XPS), μRaman spectroscopy, scanning electron microscopy (SEM), and Kelvin probe force microscopy (KPFM) measurements. The biological evaluation was performed on the MG63 osteoblast-like cell line and two selected bacteria species: S. aureus and P. aeruginosa, demonstrating both the cytocompatibility and antibacterial behavior of GO-coated SS316L substrates. We propose a two-step bactericidal mechanism: electron transfer from the bacteria membrane to the substrate, followed by ROS generation. This mechanism finds support in changes observed in contact angle, surface potential, and work function, identified as decisive factors. By addressing overlooked factors and effectively bridging the gap between understanding and practicality, we present a transformative approach for implant surfaces, combating microbial resistance, and offering new application possibilitie.

Corrosion-Resistant and Electrically Conductive Oxide Coatings for Metal Bipolar Plates for PEM Electrolyzers

The PEM electrolyzers are considered a promising alternative to alkaline water electrolyzers, as the advantages of PEM technology are high efficiency, high power density, a wide range of power inputs, low operating temperatures, relatively quick start-up, and easy scale-up. The ability of PEM electrolyzers to function dynamically makes them particularly appealing in energy capture and storage systems where electrical energy is derived from renewable sources such as solar and wind power. The bipolar plates (BPPs) are essential components of the PEM electrolyzer stacks and account for the main fraction of the total weight and cost. The BPPs must be electrically conductive, highly corrosion-resistant, and maintain a low interface contact electrical resistance (ICR). The root causes of the BPPs corrosion issues are non-conductive oxides formation increasing electrical resistance, and metal ions out-diffusion poisoning the catalyst and electrolyte membrane. The US Department of Energy has set targets for bipolar plates in fuel cells, including corrosion current densities < 1 µA/cm2 and ICR < 10 mΩ·cm2. Even though these targets do not apply to BPPs in PEM electrolyzers, they provide an indication of acceptable values. The problems outlined above are being overcome or minimized by applying corrosion-resistant and simultaneously electrically conductive coatings.This work, therefore, investigates various corrosion-resistant and electrically conductive oxide coatings prepared by reactive high-power impulse magnetron sputtering (HiPIMS) on SS316L substrates. Reactive HiPIMS is an advanced and progressive magnetron sputter deposition technique suitable for preparing high-quality oxide coatings. The main advantage of HiPIMS is a high degree of ionization of sputtered particles in the discharge plasma and the associated high ion-to-atom ratio in particle flux toward the substrate. This allows one to achieve coating densification and crystallinity at low substrate temperature and without applying a substrate bias voltage. In our case, the native oxide on the SS316L substrate surface was removed by employing plasma etching prior to the coating deposition utilizing HiPIMS-generated ions accelerated towards the substrate by an applied bias voltage. The oxide coatings were deposited using an unbalanced magnetron with a directly water-cooled planar target with a diameter of 100 mm in argon-oxygen gas mixtures at the argon pressure of 1 Pa in an ultra-high vacuum chamber. The oxygen partial pressure was controlled by a PID regulator at a given power density in a pulse. This allowed the deposition of the coatings with different stoichiometries and, thus, different electrical conductivity and corrosion resistance.The electrical resistivity of oxide coatings was measured by a four-point probe system on a non-conductive glass substrate. The compaction pressure dependence of ICR between the test plate and a gas diffusion layer (GDL) was measured in a range from 0.3 to 2.0 MPa on a custom-designed device using gold-coated cylindrical copper electrodes. All electrochemical measurements were performed in an H2SO4 electrolyte solution with an acidity of pH 5.5, fluorine ions concentration of 5 ppm, and a temperature of 60 ℃ to simulate the PEM electrolyzer environment. Accelerated corrosion tests were carried out in extreme anodic conditions of the PEM electrolyzer via potentiostatic polarization at a potential of 2 V vs SHE. Open circuit potential, corrosion current, Tafel slopes, and polarization resistance were determined from potentiodynamic polarization curves measured from 0 to 2 V vs SHE recorded at a scan rate of 1 mV/s, this range should cover most of the potentials experienced inside a PEM electrolyzer. Potentiodynamic polarization and ICR versus compaction pressure were measured before and after the accelerated corrosion test.

Corrosion characteristics of Ti and Al2O3/Ti thin films sputtered on 316LSS

In this work, two thin films (Ti and Al2O3/Ti) were deposited on 316LSS substrates by the physical vapor deposition (PVD) sputtering technique. Heat treatment was applied for thin films at 400 °C for 2 h. Thin films were divided into two groups, The First group cooled in the air (normalized), and the second cooled in the furnace (annealed). The electrochemical characteristics were investigated by potentiodynamic polarization (POT) and impedance spectroscopy (EIS) tests. The corrosion resistance (CRST) for all thin films before and after heat treatment was determined in 3.5% NaCl at room temperature (RT). Scanning electron microscope (SEM), and surface topography were studied for all thin films before and after heat treatment and corrosion tests. At as-deposited conditions, superior CRST belonged to Ti thin film. Meanwhile, after heat treatment, the annealed 316LSS/ Al2O3/Ti had the lowest corrosion rate 0.17 mm/y, and the highest CRST of about 3655 ohm.cm2.

Electrochemical corrosion study of chitosan-hydroxyapatite coated dental implant

Chitosan (Ch) is a naturally occurring biocompatible and bio-degradable material with high corrosion protective capacities for metals in various corrosive media. Hydroxyapatite (HA) is a significant biodegradable and bioactive material. In the present work, chitosan-hydroxyapatite (Ch-HA) composite coatings with various concentrations of chitosan were made on 316L stainless steel (316L SS) using sol–gel dip coating technique. The coatings were characterized by X-ray diffraction (XRD), FTIR, SEM, and electrochemical measurements. The surface morphology results (SEM) of coated implants exposed the fairly dense microstructures having uniformity without cracks and pores indicating that coating was successfully deposited. From electrochemical analyses, it was observed that the value of corrosion current density and the corrosion rate decreased from 6.03 to 0.15 and 5.56-0.13 respectively indicating that 1.5gCh-HA is the best coating concentration. The electrochemical results demonstrated an improvement in the corrosion resistance of 316L SS than the bare one. The decrease in slope and loop area of cyclic voltammograms reveals about improvement in corrosion resistance. This increment in corrosion resistance of the Ch-HA coated SS implant in the artificial saliva is as 1.5gCh-HA > 2gCh-HA >1gCh-HA >0.5gCh-HA. Furthermore, Ch-HA coatings revealed appropriate adhesion with 316L SS substrate for its use in dental implants.

A study on the effect of bioactive glass and hydroxyapatite-loaded Xanthan dialdehyde-based composite coatings for potential orthopedic applications

The most important challenge faced in designing orthopedic devices is to control the leaching of ions from the substrate material, and to prevent biofilm formation. Accordingly, the surgical grade stainless steel (316L SS) was electrophoretically deposited with functional composition of biopolymers and bioceramics. The composite coating consisted of: Bioglass (BG), hydroxyapatite (HA), and lawsone, that were loaded into a polymeric matrix of Xanthan Dialdehyde/Chondroitin Sulfate (XDA/CS). The parameters and final composition for electrophoretic deposition were optimized through trial-and-error approach. The composite coating exhibited significant adhesion strength of “4B” (ASTM D3359) with the substrate, suitable wettability of contact angle 48°, and an optimum average surface roughness of 0.32 µm. Thus, promoting proliferation and attachment of bone-forming cells, transcription factors, and proteins. Fourier transformed infrared spectroscopic analysis revealed a strong polymeric network formation between XDA and CS. scanning electron microscopy and energy dispersive X-ray spectroscopy analysis displayed a homogenous surface with invariable dispersion of HA and BG particles. The adhesion, hydrant behavior, and topography of said coatings was optimal to design orthopedic implant devices. The said coatings exhibited a clear inhibition zone of 21.65 mm and 21.04 mm with no bacterial growth against Staphylococcus aureus (S. Aureus) and Escherichia coli (E. Coli) respectively, confirming the antibacterial potential. Furthermore, the crystals related to calcium (Ca) and HA were seen after 28 days of submersion in simulated body fluid. The corrosion current density, of the above-mentioned coating was minimal as compared to the bare 316L SS substrate. The results infer that XDA/CS/BG/HA/lawsone based composite coating can be a candidate to design coatings for orthopedic implant devices.

Microstructure and Performance Research on Ceramic-Enhanced Inconel 718 Matrix Composite Using Laser Additive Manufacturing

This article presents a 95% IN718 + 5% (75% Cr2O3 + TiO2) ceramic coating on the SS316L substrate surface with laser additives. The macro shape, phase, microstructure, interface, wear resistance and tensile resistance of metal base composite materials are analyzed. The results show that metal matrix composite (MMC) laminated composite materials have good microscopic hardness and wear resistance compared to single materials. Comparative analyses with single IN718 materials indicate that the laminated composite materials exhibit superior microscopic hardness and wear resistance. Additionally, the study reveals a positive correlation between material hardness and wear resistance, characterized by reduced wear coefficient and average abrasion with increased material hardness. The findings of this research offer a cost-effective and practical method for producing high-resistance coating layer composite materials.

Fabrication of Multi-Walled Structure through Parametric Study of Bead Geometries of GMAW-Based WAAM Process of SS309L.

In the present study, an attempt is made to investigate and optimize the bead geometries of bead width (BW) and bead height (BH) of SS-309L using an SS316L substrate by employing a gas metal arc welding (GMAW)-based wire-arc additive manufacturing (WAAM) process. The Box-Behnken design approach was used to conduct the trials of single-layer depositions with input variables of travel speed (TS), voltage (V), and gas mixture ratio (GMR). The developed multi-variable regression models were tested for feasibility using ANOVA and residual plots. The data obtained indicated that V had the most significant impact on BW, followed by TS and GMR. For BH, TS had the most significant impact, followed by GMR and V. The results of single-response optimization using a passing vehicle search (PVS) algorithm showed a maximum BH of 9.48 mm and a minimum BW of 5.90 mm. To tackle the contradictory situation, a multi-objective PVS algorithm was employed, which produced non-dominated solutions. A multi-layered structure was successfully fabricated at the optimal parametric settings of TS at 20 mm/s, of voltage at 22 V, and of GMR at 3. For multi-layer structures, fusion among the layers was observed to be good, and they were found to be free from the disbonding of layers. This revealed the suitability of the PVS algorithm for generating suitable optimal WAAM variables. We consider the current work highly beneficial for users fabricating multi-layer structures.