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Sol-Gel-based reaction mixture sols have been long used to fabricate dense and uniform bioactive coatings with superior mechanical stability over metallic implants. On account of precise control over synthesis, fabrication, formed and low temperature of processing, this technology is one of the most feasible routes to produce bio-ceramic coatings. The study aims to develop a physical barrier over metal implants in form of bioinert Zirconia coatings, phase-stabilized using Dysprosium. The metallic substrates were cut into 10 mm × 10 mm samples and diamond polished after being polished with a 1000 grade emery sheet. Novel spin-coated zirconia films were fabricated over 316L Stainless steel substrates and were sintered at 600°C to obtain firm and uniform crack-free coatings. The thickness of the coatings was determined by ELCA-D meter thermal analysis was performed using TGA-DTA. Phase determination was performed using X-Ray diffraction followed by morphological investigations using Scanning electron microscopy. The corrosion resistance was evaluated with Polarization studies and electrokinetic data was derived using Tafel extrapolation. Biocompatibility evaluation was performed against MG-63 cell lines and RBCs along with bone-forming ability in vitro in SBF. Stable crack-free 3 Layer coatings fabricated at 2000 rpm for 3 s with a thickness of around 1 μm were found to be optimal for corrosion resistance behavior of steel implants at a low I Corr value of 0.501 µA/cm 2 and adhesion strength of 40.93 MPa when untreated falling down to 39.92 MPa when immersed in SBF. The study concludes that medium rpm coatings sustain enough sol to produce crack-free coatings that form a strong physical barrier between body fluid and implant surface thereby reducing the attack of corrosive ions and protecting the implant surface without participating in any form of bioactivity but supporting native bone regeneration capabilities.

Medical grade 316L stainless steel was laser surface melted (LSM) using continuous wave Nd-YAG laser in argon atmosphere at 1 and 5 mm/s. The treated surfaces were characterized using electron backscatter diffraction to study the influence of top surface crystallographic orientation and type of grain boundaries on corrosion resistance, wettability, and biocompatibility. The laser scan velocity was found to have a marginal influence on the surface roughness and the type of grain boundaries. However, the crystal orientation density was found to be relatively high in 1 mm/s samples. The LSM samples showed a higher concentration of {101} and {123} planes parallel to the sample surface as well as a higher fraction of low-angle grain boundaries. The LSM samples were found to exhibit better surface wettability and enhanced the viability and proliferation of human fetal osteoblast cells in vitro when compared to the untreated samples. Further, the corrosion protection efficiency of 316L stainless steel was improved up to 70% by LSM in as-processed condition. The increased concentration of {101} and {123} planes on surfaces of LSM samples increases their surface energy, which is believed to be responsible for the improved in vitro cell proliferation. Further, the increased lattice spacing of these planes and high concentration of low-energy grain boundaries in LSM samples would have contributed to the better in vitro corrosion resistance than untreated 316L stainless steel. Our results indicate that LSM can be a potential treatment option for 316L stainless steel-based biomedical devices to improve biocompatibility and corrosion resistance. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 569-577, 2018., (© 2017 Wiley Periodicals, Inc.)

We propose herein a nondestructive surface modification technique called ultrasonic nanocrystalline surface modification (UNSM) to increase the strength and to improve the tribological performance of 316L stainless steel (SS) tubing. Nanocrystallization along nearly the complete tube thickness of 200μm was achieved by UNSM technique that was confirmed by electron backscatter diffraction (EBSD). Nano-hardness of the untreated and UNSM-treated specimens was measured using a nanoindentation. Results revealed that a substantial increase in hardness was obtained for the UNSM-treated specimen that may be attributed to the nanocrystallization and refined grains. Stress-strain behavior of the untreated and UNSM-treated specimens was assessed by a 3-point bending test. It was found that the UNSM-treated specimen exhibited a much higher strength than that of the untreated specimen. In addition, the tribological behavior of the untreated and UNSM-treated specimens with an outer diameter (OD) of 1.6mm and an inner diameter (ID) of 1.2mm was investigated using a cylinder-on-cylinder (crossed tubes of equal radius) tribo-tester against itself under dry conditions at ambient temperature. The friction coefficient and wear resistance of the UNSM-treated specimen were remarkably improved compared to that of the untreated specimen. The significant increase in hardness after UNSM treatment is responsible for the improved friction coefficient and wear resistance of the tubing. Thus, the UNSM technique was found to be beneficial to improving the mechanical and tribological properties of 316L SS tubing for various potential biomedical applications, in particular for coronary artery stents., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Wire- and arc-based additive manufacturing (WA-AM) technology is a prominent solution to produce components having large-scale dimensions in terms of elevated deposition rates, high material utilization efficiency, and cost effectiveness. Although many research works have explored the WA-AM process of 316L stainless steel, the selection of optimal input parameters for enhancing geometrical characteristics of the WA-AMed 316L stainless steel has not been addressed. In this paper, the variables—voltage (U), current (I), and traveling speed (V), were optimized to obtain the expected attributes of weld beads (WB) in the WA-AM of 316L SS. The empirical models of the width (BW), height (BH), and contact angle (CA) of WBs were developed using a BRFFNN (Bayesian regularized feed forward neural networks) model. To determine the best optimality, the non-dominated-sorting-genetic algorithm based on a grid partition (NSGA-GP) and TOPSIS (technique for order of preference by similarity-to-ideal solution) were adopted. The outcomes indicate that the developed BRFFNN models are adequate to predict the objectives (BW, BH, and CA). The optimized value of I, U, and V is 130 A, 22.0 V, and 0.30 m/min, respectively, which enable BW, BH, and CA to be improved by 22.97%, 11.24%, and 5.61%, respectively. The optimal parameters were used to successfully build a component without major defects, indicating their suitability for producing 316L SS components used in industrial applications. The outcomes have demonstrated the efficiency of the proposed optimization approach, which can also be used to predict optimal parameters of other AM and conventional manufacturing processes. [ABSTRACT FROM AUTHOR]

ABSTRACT This research studies the effect of variable stress levels on the rotating bending fatigue (RBF) tests of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) method. The mechanical properties and fatigue behavior were evaluated to ascertain the correlation between the applied stress levels and microstructural changes that occurred during the fatigue experiments. These relationships were further investigated using a classical model developed on the Python platform. The microstructural analysis demonstrated that the face‐centered cubic structure was maintained throughout the application of stresses, varying from 255 to 402 MPa along with no phase changes. Nevertheless, the density of shear lines on the surface was substantially influenced by variations in stress levels as demonstrated by high‐stress areas in Kernel average misorientation maps. At lower stress levels, the model analysis exhibited a higher degree of reliability, with R2 values of 96.25% at lower stress rather than 89.30% at higher stress. [ABSTRACT FROM AUTHOR]

Selective Laser Melting (SLM) is an advanced additive manufacturing technique that demands meticulous control over thermal dynamics to maintain the integrity and performance of manufactured parts. This study presents the development and validation of a thermal model designed to enhance the SLM process for 316L stainless steel (316L SS) and titanium alloy Ti6Al4V. A specially constructed Argon Chamber Setup, equipped with a 200 W continuous-wave (CW) fibre laser system, was used to create an SLM-representative environment for 316L SS, enabling precise experimental validation of the model. This validation serves as a robust baseline, facilitating the model's extension to more complex materials like Ti6Al4V, thereby supporting a cost-efficient and safe approach to initial testing. The rigorously validated thermal model offers a comprehensive link between experimental data and numerical simulations in SLM. It supports process optimisation by accurately predicting thermal behaviours, contributing significantly to additive manufacturing advancements. By fine-tuning processing parameters, this model enhances material characteristics, thereby providing practical insights applicable to industrial production and improving the consistency and quality of SLM-manufactured parts. [ABSTRACT FROM AUTHOR]

WC–Co cutting tools are widely used in harsh conditions, but the brittleness of this material can limit their use. Joining steels to WC–Co can provide an alternative, by combining the toughness of steel with the high hardness and wear resistance of WC–Co. The creation of textures at the bonding interface is known to increase the adhesion between materials, through a mechanical interlocking effect and an increase in the contact area. In this sense, this work proposes the laser surface texturing of WC–Co green compacts with cross-hatched and circular micropatterns and subsequent pressure-assisted sintering of the textured and sintered WC–Co with 316L SS powder to improve the bonding between materials. Results showed that the bonding of the textured multi-material was successfully processed and an interdiffusion zone was formed at the bonding interface without the presence of detrimental compounds. The addition of textures showed a tendency to increase the shear bond strength, with the cross-hatched micropatterns generally showing a higher bonding strength than the circular micropatterns. This approach showed to have the potential to improve the bonding between materials, thus contributing to the development of novel multi-material WC–Co/316L stainless steel cutting tools with enhanced properties and performance. [ABSTRACT FROM AUTHOR]

This study investigates the microstructure and corrosion behavior of the selective laser melted (SLM) 316L stainless steel in a Ringer's solution. Besides, the biocompatibility of the fabricated SLM alloy was investigated using MG63 cells. The wrought, SLM, and heat-treated at 450 °C (SLM-450) stainless steel alloys were picked for the investigation. Microscopy evaluation indicated that SLM and SLM-450 samples showed a cellular morphology due to the fast cooling rate the SLM process. SLM-450 sample showed a better corrosion performance compared to other samples. Charge transfer resistance of the SLM-450 after 330 h of immersion was two times higher than wrought and SLM samples in the corrosive solution, respectively. Moreover, the SLM-450 alloy revealed the highest biocompatibility, most probably because of the stress relief after heat treatment, the lower release of toxic cations, and the presence of round MnSiO 3 phase in the SLM-processed alloy. [ABSTRACT FROM AUTHOR]

Purpose: The current investigation aims at observing the influence of the cooling channel on the thermal and residual stress behavior of the selective laser melting (SLM)316L uni-layer thermo-mechanical model. Design/methodology/approach: On a thermo-mechanical model with a cooling channel, the effect of scanning direction, parallel and perpendicular and scan spacing was simulated. The effect of underlying solid and powder bases was evaluated on residual stress profile and thermal variables at various locations. Findings: The high heat dissipation of solid base due to high cooling rates and steep thermal gradients can reciprocate with smaller melt pool temperature and melt pool size. Given the same scan spacing, residual stresses were found lower when laser scanning was perpendicular to the cooling channel. Moreover, large scan spacing was found to increase residual stresses. Originality/value: Cooling channels are increasingly being used in additive manufacturing; however, their effect on the residual stress behavior of the SLM component is not extensively studied. This research can serve as a foundation for further inquiries into the impact of base material design such as cooling channels on manufactured components using SLM. [ABSTRACT FROM AUTHOR]

Sol-Gel-based reaction mixture sols have been long used to fabricate dense and uniform bioactive coatings with superior mechanical stability over metallic implants. On account of precise control over synthesis, fabrication, formed and low temperature of processing, this technology is one of the most feasible routes to produce bio-ceramic coatings. The study aims to develop a physical barrier over metal implants in form of bioinert Zirconia coatings, phase-stabilized using Dysprosium. The metallic substrates were cut into 10 mm × 10 mm samples and diamond polished after being polished with a 1000 grade emery sheet. Novel spin-coated zirconia films were fabricated over 316L Stainless steel substrates and were sintered at 600°C to obtain firm and uniform crack-free coatings. The thickness of the coatings was determined by ELCA-D meter thermal analysis was performed using TGA-DTA. Phase determination was performed using X-Ray diffraction followed by morphological investigations using Scanning electron microscopy. The corrosion resistance was evaluated with Polarization studies and electrokinetic data was derived using Tafel extrapolation. Biocompatibility evaluation was performed against MG-63 cell lines and RBCs along with bone-forming ability in vitro in SBF. Stable crack-free 3 Layer coatings fabricated at 2000 rpm for 3 s with a thickness of around 1 μm were found to be optimal for corrosion resistance behavior of steel implants at a low ICorr value of 0.501 µA/cm2 and adhesion strength of 40.93 MPa when untreated falling down to 39.92 MPa when immersed in SBF. The study concludes that medium rpm coatings sustain enough sol to produce crack-free coatings that form a strong physical barrier between body fluid and implant surface thereby reducing the attack of corrosive ions and protecting the implant surface without participating in any form of bioactivity but supporting native bone regeneration capabilities. [ABSTRACT FROM AUTHOR]

Sol-Gel-based reaction mixture sols have been long used to fabricate dense and uniform bioactive coatings with superior mechanical stability over metallic implants. On account of precise control over synthesis, fabrication, formed and low temperature of processing, this technology is one of the most feasible routes to produce bio-ceramic coatings. The study aims to develop a physical barrier over metal implants in form of bioinert Zirconia coatings, phase-stabilized using Dysprosium. The metallic substrates were cut into 10 mm × 10 mm samples and diamond polished after being polished with a 1000 grade emery sheet. Novel spin-coated zirconia films were fabricated over 316L Stainless steel substrates and were sintered at 600°C to obtain firm and uniform crack-free coatings. The thickness of the coatings was determined by ELCA-D meter thermal analysis was performed using TGA-DTA. Phase determination was performed using X-Ray diffraction followed by morphological investigations using Scanning electron microscopy. The corrosion resistance was evaluated with Polarization studies and electrokinetic data was derived using Tafel extrapolation. Biocompatibility evaluation was performed against MG- 63 cell lines and RBCs along with bone-forming ability in vitro in SBF. Stable crack-free 3 Layer coatings fabricated at 2000 rpm for 3 s with a thickness of around 1 µm were found to be optimal for corrosion resistance behavior of steel implants at a low ICorr value of 0.501 µA/cm2 and adhesion strength of 40.93 MPa when untreated falling down to 39.92 MPa when immersed in SBF. The study concludes that medium rpm coatings sustain enough sol to produce crack-free coatings that form a strong physical barrier between body fluid and implant surface thereby reducing the attack of corrosive ions and protecting the implant surface without participating in any form of bioactivity but supporting native bone regeneration capabilities. [ABSTRACT FROM AUTHOR]

Polymer coatings are increasingly used in varied fields and applications from simple coatings of barrier to intricated nanotechnology based composite. In the present study, polyvinylidene fluoride(PVDF)/Hydroxyapatite (HA)coatings were produced by spin coating technique over 316L SS. Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) were used to observe the coated 316L SS substrates surface morphology. The corrosion protection efficiency of pure polyvinylidene fluoride and polyvinylidene fluoride/HA nanocomposite coatings on 316L SS was inspected using potentiodynamic polarization along with the ions release techniques in Hank's solution. A superior biocompatibility and an improved protection performance against corrosion were obtained for the 316L SS samples with nanocomposite coatings compared with the pure polyvinylidene fluoride coatings and pristine 316L SS counterparts. The 316L SS samples coated by PVDF/HA nanocomposite showed enhanced corrosion protection within Hank's solution. The corrosion of 316L SS samples within Hank's solution increased from 92.99% to 99.99% when using 3wt% HA due to increasing the PVDF inhibition efficiency. Good agreements in the electrochemical corrosion parameters were obtained from using ions release and potentiodynamic polarization tests. [ABSTRACT FROM AUTHOR]

The influences of the plastic strain and strain rate on the corrosion behaviours of 316L stainless steel (316L SS) in a simulated cathodic environment of proton exchange membrane fuel cells (PEMFCs) are investigated using potentiodynamic curves, electrochemical impedance spectroscopy (EIS), Mott-Schottky plots and X-ray photoelectron spectroscopy (XPS). The results demonstrate that 316L SS is in the passive state in the simulated cathodic environment of PEMFCs and that a passive film can be formed on the cathodic bipolar plate, which is composed of 316L SS, during PEMFC operation. The passive film can protect 316L SS from further corrosion, and the corrosion resistance of the passive film on 316L SS reaches a maximum at a plastic strain of 20%. The corrosion resistance increases with the strain rate; thus, the maximal corrosion resistance corresponds to a plastic strain of 20%, and the corrosion protection increases with the strain rate. The XPS results demonstrate that the Cr 2 O 3 content in the passive film on 316L stainless steel reaches a maximum at a plastic strain of 20%, and the increased strain rate can increase the Cr 2 O 3 content. • A passive film can be formed on 316L SS in the cathodic environment of PEMFC. • The plastic strain has an evident effect on the corrosion behavior of 316L SS. • The plastic strain of 20% corresponds to the best corrosion resistance. • The increased strain rate can improve the corrosion resistance of 316L SS. [ABSTRACT FROM AUTHOR]

The influences of two types of heat-treatments on the corrosion behavior of 316L SS in the simulated cathodic environment of PEMFC, are investigated using potentiodynamic curve, electrochemical impedance spectroscopy (EIS), Mott-Schottky plot and auger electron spectroscopy (AES), respectively. The results show that 316L SS is in the passive state within the potential region from −0.1V SCE to 0.8V SCE in the simulated cathodic environment of PEMFC, and a passive film can be formed on 316L SS. The passivity of 316L SS in the simulated cathodic environment of PEMFC firstly increases and then degrades with the increased solid solution temperature or time, and the best passivity corresponds to the solid solution temperature at 1050 °C for 40 min among other solid solution treatments. While 316L SS heat-treated with the solid solution treatment at 1050 °C for 40 min plus aging treatment at 900 °C for 4 h, also has the best passivity in the same solution among other solid solution plus aging treatments. The best corrosion protection, lowest donor density and the highest thickness of the passive film corresponding to the solid solution temperature at 1050 °C for 40 min among other solid solution or solid solution plus aging heat treatments, and this treatment is mostly suitable for improving the anti-corrosion property of 316L SS in the simulated cathodic environment of proton exchange membrane fuel cell (PEMFC). • Two kinds of heat treatments were used to prepare the 316L stainless steel samples. • A passive film can be formed on 316L SS in the cathodic environment of PEMFC. • The heat treatment had an obvious effect of the film corrosion protection on 316L SS. • The solid solution treatment at 1050 °C corresponded to the best film corrosion on 316L SS. [ABSTRACT FROM AUTHOR]

This work aims to investigate the influence of niobium and carbon nanostructured coatings on the corrosion resistance of the 316L SS. The coated and uncoated specimens were morphologically and structurally characterized by using OM, SEM/EDX, DRX, FTIR, Raman spectroscopy and XPS techniques. The corrosion behaviour was assessed by OCP, PPc, EIS as well as immersion tests in 0.6 mol L−1 NaCl solution. In addition, the average contact angles were used to evaluate the surfaces free energy by the Van Oss interfacial tension component theory approach. Results showed that the surface treatments positively influenced the corrosion resistance of the 316L SS and the coatings act as a protective barrier against corrosion process. The reactive sputtering technique increased the wettability of the surfaces in relation to the base material. Considering applications in aggressive media, the 316L SS/Nb 2 O 5 specimen exhibits superior performance when compared to the base material and 316L SS/carbon. [Display omitted] • Nanostructured niobium and carbon coatings deposited on the 316L SS surface. • Reactive sputtering technique as a powerful tool to produce niobium and carbon coatings. • The surface treatment increased the corrosion resistance of the 316L SS. • Nb 2 O 5 coating presented a superior performance to uniform and localised corrosion processes. • Reactive sputtering technique increased the wettability of the functionalized samples. [ABSTRACT FROM AUTHOR]

The development of biomaterials for implants nowadays requires materials with superior mechanical and physical properties for enhanced osseointegration and sustained longevity. This research work was conducted to investigate the influence of nano hydroxyapatite (HAp) powder mixed electrical discharge machining (PMEDM) on surface morphology and microhardness of modified 316L stainless steel surface. The chosen process parameters were discharge current, pulse on/off duration and gap voltage in order to analyze the selected output responses. HAp concentration (15 g/l) along with reverse polarity was kept constant for current experimentation. The experimental results testified that surface morphology of PMEDM surface was significantly improved along with augmentation of 79% in microhardness (HV) of HAp modified surface of medical grade stainless steel. Furthermore, XRD and SEM characterization confirmed the deposition of calcium, phosphorous and inter-metallic compounds on HA-PMEDMed surface. The surface thus produced is expected to facilitate better bone-implant adhesion and bioactivity. [ABSTRACT FROM AUTHOR]

Brass alloys are used in many applications. However, improving their surface properties would help to increase their service life. For that, this study proposed to deposit using high velocity oxygen fuel (HVOF), nickel-chromium-boron-silicon (NiCrBSi) alloy, and 316L stainless steel (SS) coatings on brass substrates and investigate the mechanical properties and corrosion resistance of the coatings. The surface–interface morphologies, phases, and porosity of the coatings were analyzed using a scanning electron microscope and 3D profilometer. The adhesive strength and microhardness of the NiCrBSi and 316L SS coatings were also studied. Corrosion investigations were carried out using the salt fog test in an acetic acid salt spray atmosphere according to the NF EN ISO 9227 standard. This work showed that the 316L SS coatings presented a lower microhardness and higher adhesion strength than the NiCrBSi coatings despite their lower corrosion resistance. This could be explained by the microstructure of the coatings, the 316L SS coatings exhibiting more defects such as pores, un-melted particles, and oxides. [ABSTRACT FROM AUTHOR]

The corrosion behaviour of 316L stainless steel (316L SS) in 10% H2SO4 solution (94°C) with various concentrations of NaCl (0–0.085 mol/L) was studied by immersion corrosion test and polarization methods, combined with SEM/EDS, XPS and XRD tests. The influence of NaCl on the corrosion of 316L SS was investigated. The results showed that at lower NaCl contents (0–0.0085 mol/L), the steel presented a general corrosion characteristic with a higher corrosion speed and the corrosion rate increased with the NaCl content. At higher NaCl contents (≥0.017 mol/L), the corrosion rate decreased remarkably due to the protective corrosion products precipitation which contained metallic sulphates and NaHSO4. However, the higher concentration of chloride ions caused micron pitting-like local dissolution on the surface. The addition of Na2SO4 effectively inhibited general corrosion of the steel because of a dense and continuous products layer enriched with more NaHSO4 and metallic sulphates formed. [ABSTRACT FROM AUTHOR]

Single-step electrophoretic co-deposition (EPD) technique was used to enhance the bioactivity of the 316L stainless steel (316L SS) surface by bioactive glass/chitosan composite coatings. Two modified glass compositions of Bioglass® by the addition of boron were utilized to prepare such composite layers, and the Bioglass® was synthesized for comparison. Different EPD coating factors were studied. Namely, voltage, time, glass powder, and chitosan concentrations, to obtain crack-free and good adhesive coatings. The achieved surfaces were characterized by SEM/EDX, TGA, XRD and FTIR and their wettability and roughness were investigated. The in vitro bioactivity of the coated metals was compared in simulated body fluid (SBF) and Dulbecco's modified eagle medium (DMEM) for up to 15 days. The electrochemical corrosion behavior of the coated metals was evaluated using potentiodynamic polarisation and impedance techniques in the two biological solutions SBF and DMEM at 37 °C. The results showed that the achieved coatings were uniform, homogenous and crack-free with desirable thickness. Moreover, the coating layers were exhibited by very high wettability, and their roughness values ranged from 170 ± 18 to 234 ± 17 μm. The in vitro bioactivities proved that the coating layers represented a better ability to form hydroxyapatite crystals on their surfaces in SBF than in DMEM. The corrosion resistance of 316L SS was improved by the bioactive composite coatings. [ABSTRACT FROM AUTHOR]

Niobium oxide is known for its biocompatibility; however it lacks on bioactivity. Sodium is one of the essential elements required for the formation and maintenance of bone. In this present study, we focus on improving the bioactivity of niobium oxide by incorporating sodium ions and obtaining nanoporous morphology by adding polyethylene glycol. Sodium niobate was prepared using sol-gel method and dip coated on 316L SS. The coated sample was sintered at the optimised heating rate of 0.5 °C min −1 . The surface morphology, chemical composition, phase composition and porosity were analysed using scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction analysis (XRD) and porosimetry. The BET analysis and AFM studies showed that the coating exhibited pores with the average diameter of 97 and 101 nm. The Vicker's microhardness test showed that sodium niobate coating exhibits three fold higher microhardness compared to 316L SS. In vitro studies show that the coating exhibited good bioactivity. Electrochemical studies confirmed that the coating offers better corrosion resistance to the substrate at pH 5.2 and pH 7.4. The hemolysis percentage of the coating was found to be 1.54% and anticoagulation studies showed that coagulation time of sodium niobate coating was similar to that of the plasma. Better adhesion, proliferation and differentiation of MG-63 cells with significant cell spreading were observed in the coating. [ABSTRACT FROM AUTHOR]

Powder injection molding (PIM) is a hybrid of powder metallurgy and plastic injection molding. It is used to develop metallic molded parts with intricate shapes and with improved properties compared with those offered by their wrought counterparts. PIM dental implants should exhibit biocompatibility, high density, good dimensional control, homogeneous properties and low manufacturing cost. In order to achieve these properties, the effect of boron (additive) addition on sintered density and of process effects on the biocompatibility of sintered implants was studied. In activated sintering, additives are used in small quantities to modify the sintering behavior of stainless steel. A constant amount of nanosize elemental boron (0-1.5 wt%) was admixed with 316L stainless steel and was compounded with complex binder to develop feedstocks using a z-blade mixer. Optimal solvent debinding parameters followed by an optimal sintering cycle played a vital role in the development of biocompatible and densified 316L stainless steel dental implants. Although all boron-containing formulations were injection-molded successfully, only PWA-0.5B-1230 samples were able to retain their shapes after sintering. It was concluded that 0.5 wt% addition of elemental boron favored the formation of 316L stainless steel with a sintered density of up to 98.5 % through the formation of a complex iron boride compound (BFe) on the grain boundaries during the sintering process. The formation of a passive layer on the outer surface of implants was controlled using optimal sintering parameters. In in vitro analysis, the cytotoxicity assessment of sintered dental implants materials was determined using the direct and indirect contact techniques. [ABSTRACT FROM AUTHOR]

The usage of conducting polymers as coating materials for bipolar plates to prevent corrosion is the recent trend in Proton Exchange Membrane Fuel Cell (PEMFC) technology. Paraphenylenediamine ( p PD) monomer was electropolymerized to poly p -phenylenediamine (P p PD) over 316L SS. The characterization of P p PD, the conducting polymer coating, over 316L SS was done using attenuated total reflectance infra-red (ATR-IR) spectroscopy to confirm the formation of P p PD. The surface morphology and topography were studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The corrosion protection performance of the coating was evaluated using open circuit potential (OCP) measurement, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization studies in PEMFC environment. EIS studies revealed that the charge transfer resistance for the coated substrates has increased by one order of magnitude than the bare substrate. Potentiodynamic polarization studies have registered lower corrosion current density by one order magnitude for the 0.06 M p PD coated substrate than the bare substrate and the polarization resistance values for the coated substrates have increased by two and a half time than the bare substrate. These results showed that P p PD coated substrates exhibited enhanced corrosion resistance in PEMFC environment. [ABSTRACT FROM AUTHOR]

Surgical grade stainless steel (316L SS) is a widely used implant material in orthopedic surgeries. However, the release of metallic ions evidenced from the 316L SS implants in vivo conditions is a big challenge. In order to minimize the release of metallic ions, coating the 316L SS implant with a biocompatible material like hydroxyapatite [HAP, Ca(PO)(OH)] is one of the suitable methods. In this paper, the hydroxyapatite coating on borate passivated through poly- ortho-phenylenediamine (PoPD)-coated 316L SS by a dip coating method has been reported. The coatings were characterized by electrochemical techniques such as potentiodynamic polarization, electrochemical impedance spectroscopy, and cyclic voltammetry. Surface characterization studies of the coatings such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) were also carried out. The leach out characteristics of the coatings was determined at the impressed potential. The mechanical property of the coatings was evaluated by Vicker's microhardness test. The Cr-rich passive film formed underneath the PoPD layer showed a higher protective efficiency. The ability to form apatite on the post-passivated PoPD-coated 316L SS specimen was examined by immersing it in the simulated body fluid. The enhanced corrosion resistivity of the HAP coating on the post-passivated PoPD-coated 316L SS was due to an effective barrier of PoPD followed by the passive film underneath the PoPD. [ABSTRACT FROM AUTHOR]

The effect of novel, pyrazolone derivatives, namely, (Z)-3-methyl-4-(2-m-tolylhydrazono)- 1H-pyrazol-5(4H)-compound A, (Z)-4-(2-(3-methoxyphenyl)hydrazono)-3-methyl-1H-pyrazol- 5(4H)-compound B, and (Z)-3-methyl-4-(2-(3-nitrophenyl) hydrazono)-1H-pyrazol-5 (4H)-compound C as corrosion inhibitors of 316L stainless steel (SS) in 1M HCl has been investigated by using weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrical frequency modulation (EFM) techniques. Polarization data clearly indicated that the pyrazol-5-one derivatives behave as mixed type inhibitors. The effect of temperature on corrosion inhibition has been studied and the thermodynamic activation and adsorption parameters were calculated and discussed. EIS was used to investigate the mechanism of corrosion inhibition. EFM can be used as a rapid and nondestructive technique for corrosion rate measurements without prior knowledge of Tafel constants. The adsorption of compounds on 316L SS was found to obey Temkin adsorption isotherm. [ABSTRACT FROM AUTHOR]

Abstract: A clear ethanol based precursor sol obtained using zirconium acetate hydroxide was utilized for the deposition of nanometer ZrO2 thin films on 316L stainless steel substrates by a sol–gel dip coating process. The influence of heat treatment temperature on the structural evolution of the films was examined using X-ray diffractometry (XRD) and Fourier transform-infrared spectroscopy (FT-IR). The results indicated that the adopted production route led to the formation of an amorphous structure at 200–300°C and surface tetragonal (t-ZrO2) and monoclinic (m-ZrO2) zirconia phases at 700°C and 900°C temperatures, respectively. Microstructural studies by a scanning electron microscopy (SEM) showed that the morphology and size of the particles of ZrO2 films depend upon the heat treatment temperature. The effect of firing temperature on the thickness of ZrO2 nanometer thin films was studied by three different techniques: single-wavelength ellipsometry (SWE), SEM and atomic force microscopy (AFM). The film thickness measured by the SWE and SEM techniques, as a function of heat treatment temperature, was in close agreement, elucidating a major decrease when heated up to 700°C, and a slight increase between 700 and 900°C. As determined by the AFM studies, the thickness changes were similar to those of SWE and SEM results during the former step, up to 700°C, but it appeared to be constant in the later temperature interval. The AFM profile images showed an increase in surface roughness of the films with rising of the heat treatment temperature. [Copyright &y& Elsevier]

Abstract: In this paper, structural evolution of zirconia (ZrO2) thin films which are produced by a sol–gel dip coating process on the 316L stainless steel substrates were investigated at different temperatures. Microstructural features and phase transformations of the synthesized thin films were characterized by Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffractometry (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The FT-IR, TG/DTA and XRD analysis results, in a good agreement, indicated that the adopted production route led to the formation of a surface tetragonal zirconia (t-ZrO2) film with high crystallinity at 700°C. The formed tetragonal phase was transformed to monoclinic zirconia phase (m-ZrO2) at 900°C. Corrosion performance of the heat treated ZrO2 films was evaluated through potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 1-M H2SO4 solution at 80°C. The results demonstrated that the treated thin film at 500°C had the strongest corrosion barrier performance on the 316L stainless steel. The SEM images showed a crack-free uniform film with an average thickness of 155nm on the surface can be obtained. Moreover, AFM investigations also showed that the average roughness of the coated films increased with the rising heat temperature. [Copyright &y& Elsevier]

The use of metal additive manufacturing (AM) has strongly increased in the industry during the last years. More specifically, selective laser melting (SLM) is one of the most used techniques due to its numerous advantages compared to conventional processing methods. The purpose of this study is to investigate the effects of process parameters on the microstructural and corrosion properties of the additively manufactured AISI 316L stainless steel. Porosity, surface roughness, hardness, and grain size were studied for specimens produced with energy densities ranging from 51.17 to 173.91 J/mm3 that resulted from different combinations of processing parameters. Using experimental results and applying the Taguchi model, 99.38 J/mm3 was determined as the optimal energy density needed to produce samples with almost no porosity. The following analysis of variance ANOVA confirmed the scanning speed as the most influential factor in reducing the porosity percentage, which had a 74.9% contribution, followed by the position along the building direction with 22.8%, and finally, the laser energy with 2.3%. The influence on corrosion resistance was obtained by performing cyclic potentiodynamic polarization tests (CPP) in a 3.5 wt % NaCl solution at room temperature for different energy densities and positions (Z axis). The corrosion properties of the AM samples were studied and compared to those obtained from the traditionally manufactured samples. The corrosion resistance of the samples worsened with the increase in the percentage of porosity. The process parameters have consequently been optimized and the database has been extended to improve the quality of the AM-produced parts in which microstructural heterogeneities were observed along the building direction. [ABSTRACT FROM AUTHOR]

Abstract: The composition and structure of passive film formed on 316L SS immersed in an anhydrous methanol solution (water content<0.05wt%) containing 0.42wt% LiCl at 323–473K were investigated by X-ray photoelectron spectroscopy (XPS), and compared with those of film formed in an aqueous solution. The passive film formed in the methanol solution was mainly composed of Fe and Cr oxides, and it possessed a double-layered structure consisting of an Fe oxide-rich outer layer and a Cr oxide-rich inner layer. Dissolution of the Fe-rich layer and densification of the Cr-rich inner layer were observed, especially at high temperatures. However, these were suppressed in an aerated methanol solution at 423K or below, probably due to the barrier effect of adsorbed oxygen. No Ni compound contributed to composing the passive film, even at higher temperatures. The ratio of OH− to O2− was small and decreased with an increase in temperature (the presence of oxygen suppressed the decrease, especially at 423K or below). The chloride ions were concentrated in the Fe-rich outer layer, and they penetrated more deeply than that in the aqueous solution into the passive film formed in the methanol solution. [Copyright &y& Elsevier]

Abstract: Thin film hydroxyapatite deposits through dip-coating onto prefinished low carbon 316L stainless steel substrates were prepared using alkoxide based sol–gel technique. This technique provides several advantages in the control of microstructure and the thickness of the coatings. The coatings were annealed in vacuum; sintering temperature reaching 900 °C were applied to enhance the crystallinity and purity of the films. The resultant coatings have been characterized by the use of FT-IR, XRD, EDXA SEM ICP-AES, shear bond strength and potentiodynamic polarization. The experimental results revealed that the crystallinity, microstructure, corrosion resistance and morphology of the coatings prove the formation of hydroxyapatite coating appropriate for several biomedical applications. [Copyright &y& Elsevier]

In this study, the effects of pseudo-ternary oxides on mechanical properties and microstructure of 316L stainless steel tungsten inert gas (TIG) and activating tungsten inert gas (ATIG) welded joints were investigated. The novelty in this work is introducing a metaheuristic technique called the particle swarm optimization (PSO) method to develop a mathematical model of the ultimate tensile strength (UTS) in terms of proportions of oxides flux. A constrained optimization algorithm available in Matlab 2020 optimization toolbox is used to find the optimal percentages of the selected powders that provide the maximum UTS. The study indicates that the optimal composition of flux was: 32% Cr2O3, 43% ZrO2, 8% Si2O, and 17% CaF2. The UTS was 571 MPa for conventional TIG weld and rose to 600 MPa for the optimal ATIG flux. The obtained result of hardness for the optimal ATIG was 176 HV against 175 HV for conventional TIG weld. The energy absorbed in the weld zone during the impact test was 267 J/cm2 for the optimal ATIG weld and slightly higher than that of conventional TIG weld 256 J/cm2. Fracture surface examined by scanning electron microscope (SEM) shows ductile fracture for ATIG weld with small and multiple dimples in comparison for TIG weld. Moreover, the depth of optimized flux is greater than that of TIG weld by two times. The ratio D/W was improved by 3.13 times. Energy dispersive spectroscopy (EDS) analysis shows traces of the sulfur element in the TIG weld zone. [ABSTRACT FROM AUTHOR]

• The incorporation of GO and f-MWCNTs on HAP exhibits more corrosion resistive in SBF. • The hardness of the coatings with GO and f-MWCNTs revealed enhanced strength. • Hydrophilicity of the coated implant surface allows the formation of apatite layer. • The attachment of HAP on chemically modified f-MWCNTs and GO are proved by HR-TEM. Bioceramic composite coatings were deposited on surgical grade 316L stainless steel substrate via in-situ electrolytic method by supplying the voltage of −1.5 V for 30 mins using three electrode arrangements. Formations of pure HAP/GO and HAP/f-MWCNTs composite films were developed and the structure of hydroxyapatite was retained even with incorporation of secondary materials into its matrix. Homogeneously dispersed dense coating was observed for the electrochemically derived HAP composite films on 316L SS. The attachment of GO and f-MWCNTs with hydroxyapatite particles were observed using high resolution transmission electron microscopic (HR-TEM). In-vitro corrosion studies of the fabricated bioceramic composite coatings showed better corrosion protection against the simulated body fluid. Apatite mineralization formed at faster rate for the prepared bioceramic composite films; further which it enhance their bone bonding ability. These results concluded that the electrochemical deposition of bioceramic coatings on implant may be treated as an effective method for orthopedic repair and replacements. [ABSTRACT FROM AUTHOR]

Here, we report the fabrication of a graphene oxide (GO)/polyvinylpyrrolidone (PVP) (GP) composite coating on 316L stainless steel (SS) with superior antibacterial and anti-biofouling performance using electrophoretic deposition (EPD). At an optimal EPD condition (10 V, 60 s), PVP and GO concentrations of 0.03 and 0.1 wt%, respectively, a uniform crack free coating with superior antibacterial and anti-biofouling properties is obtained. The morphology and composition of the composite coating were characterized by field emission scanning electron microscope (FESEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. The absence of COOH peak in GO and GP specimen found in the XPS and FTIR confirm the partial reduction of GO by oxidative decarboxylation during the EPD. The shift in the >N C O bond to a higher binding energy, as compared to the pure PVP, indicated the presence of intermolecular hydrogen bonding between the PVP and GO. The antibacterial activity of the coated specimens using marine bacterial isolates of Gram-negative Pseudomonas sp. and Gram-positive Bacillus sp. showed a four order reduction in bacterial density, and a significant decrease in the biofilm thickness on the GP specimens. The enhanced antibacterial activity was due to the disruption of cell membranes by sharp edges of GO surface and oxidative stress imparted due to reactive oxygen species. The enhanced surface hydration by PVP inhibited the adhesion and growth of organic molecules on GP coating. Further, the enhanced photocatalytic activity of GO due to the presence of PVP also increased the generation of H 2 O 2 in GP coatings as compared to GO coating. These results show that GP composite coating is a promising candidate to tailor 316L SS surface with excellent antibacterial and anti-biofouling properties. • GO/polyvinylpyrrolidone (GP) coating is fabricated on 316L stainless steel. • GP coating showed a four order enhancement in antibacterial activity. • Photocatalytic activity and reactive oxygen species enhanced the bactericidal activity of GP coating. • The surface hydration of GP coating augmented the antifouling property. [ABSTRACT FROM AUTHOR]

• SLM 316L SS has a better resistance to irradiation hardening than TM 316L SS under high temperature He ions irradiation. • The number density of He bubbles in TM samples was larger than that in SLM samples, while the diameter was no significant difference. • The difference in the number density of He bubbles might be the main factor causing the different irradiation hardening behavior in two kinds of samples. • The interfaces and intrinsic defects in SLM 316L SS might reduce density of He bubbles and size of dislocation loops effectively. To evaluate the effects of irradiation on additive manufacturing materials which are expected to be applied in advanced nuclear energy systems, selective laser melting 316L stainless steel (SLM 316L SS) and traditionally manufactured 316L stainless steel (TM 316L SS), were irradiated with 500 keV He ions at 700°C, respectively. SEM, TEM and nanoindentation measurements were performed to survey the effects of helium (He) bubbles on the irradiation hardening. It was found that the degree of irradiation hardening of the two materials increased with an increase of ions fluences. The hardening range of SLM 316L SS was 6-47% while that of TM 316L SS was 32-75%. Moreover, the hardening saturation phenomenon was more pronounced in TM 316L SS than in SLM 316L SS. These results suggested that SLM 316L SS owned higher resistance to irradiation hardening than TM 316L SS. TEM observations showed that the density of He bubbles in TM 316L SS was 7.06 × 1023/m3 while that in SLM 316L SS was 3.33 × 1023/m3. Further, the average sizes of bubbles were 2.2 and 2.4 nm, respectively. The differences of the number density might be why SLM 316L SS had a slighter irradiation hardening than TM 316L SS, which was consistent with Orowan model. It was suggested that the numerous intrinsic microstructures such as entangled dislocation network walls and subgrain boundaries in SLM 316L SS could greatly reduce the density of He bubbles. [Display omitted] [ABSTRACT FROM AUTHOR]

• 316L SS was fabricated by laser powder bed fusion (L-PBF) process. • L-PBF processed steel showed fine cellular/columnar structure due to rapid cooling. • The formation of passive layer on the L-PBF processed steel is favored in the alkaline media. • Better corrosion performance was observed for L-PBF processed steel. This study investigates the microstructure and electrochemical behavior of 316 L processed through laser powder bed fusion (L-PBF) and the related commercial wrought counterpart in the concrete pore solution (0.9 M NaOH + 0.9 wt% NaCl). Analyses showed that the L-PBF method did not decline the corrosion resistance of 316L SS in the alkaline solution. Even in some cases, L-PBF processed alloy showed better electrochemical behavior compared the wrought alloy. Microscopy evaluation indicated that L-PBF processed specimen showed an ultrafine cellular/columnar structure with the more uniform morphology at the higher magnifications compared to the wrought sample, possibly because of the excessive cooling rate of the L-PBF process. Besides, electrochemical studies revealed that corrosion current density related to the L-PBF processed sample reported about one-third of wrought counterpart. Also, L-PBF processed alloy identified the lower defect density compared to the wrought one. The better corrosion performance of the L-PBF processed 316L SS could be related to the fabrication method of the additively manufactured samples, which hindered the presence of detrimental phases and more stability of the passive film. [ABSTRACT FROM AUTHOR]

Effect of microstructure on the crack initiation and early propagation mechanism in the very high cycle fatigue (VHCF) regime was studied in 316L stainless steel (316L SS) by atomic force microscope (AFM) and electron back scattered diffraction (EBSD). The results show that small fatigue cracks initiate from the slip band near the grain boundaries (GBs) or the twin boundaries (TBs). Early crack propagation along or cross the slip band is strongly influenced by the local microstructure such as grain size, orientation, and boundary. Besides, the gathered slip bands (SBs) are presented side by side with the damage grains of the run-out specimen. Finally, it is found that dislocations can either pass through the TBs, or be arrested at the TBs. [ABSTRACT FROM AUTHOR]

• Interactions of the Hastelloy N-316 L SS couple affect the corrosion of material. • Corrosion of 316 L SS is accelerated while that of Hastelloy N is impeded. • Interactions of the Hastelloy N-316 L SS couple lead to the mass transfer of Fe. • Mass transfer relies on whether dissolved element can be alloyed by Hastelloy N. • Interactions of the couple depend on galvanic corrosion and Fe mass transfer. The corrosion behavior of a Hastelloy N-316 L stainless steel couple in molten LiF-NaF-KF salt at 700 °C was investigated using electrochemistry, immersion tests, and microstructure analyses. Hastelloy N exhibits better corrosion resistance than 316 L SS. Galvanic coupling between two metals accelerates the corrosion of 316 L SS but impedes the corrosion of Hastelloy N. Fe dissolved from 316 L SS was alloyed with Ni in Hastelloy N to form a concentration cell of Fe, which accelerated the mass transfer of Fe from 316 L SS to Hastelloy N. The interactions of the Hastelloy N-316 L SS couple depend on galvanic corrosion and the Fe transfer. [ABSTRACT FROM AUTHOR]