Surface Of 316L Stainless Steel Research Articles

Passivation-Induced Cr and Mo Enrichments of 316L Stainless Steel Surfaces and Effects of Controlled Pre-Oxidation

Passivation mechanisms and the effects of controlled pre-oxidation, by exposure to oxygen at ultra-low pressure, on Cr and Mo surface enrichments were investigated on polycrystalline AISI 316L stainless steel surfaces with direct transfer between surface preparation and analysis by X-ray photoelectron spectroscopy and electrochemistry. Exposure to sulfuric acid at open circuit potential causes preferential dissolution of oxidized iron species, which promotes Cr3+ and Mo4+/6+ enrichments. Anodic passivation forces oxide film re-growth and Cr3+ dehydroxylation with no loss of Mo4+/6+ pre-enrichment. Ultra-low pressure pre-oxidation promotes Mo4+/6+ enrichment in the exchange outer hydroxide layer of the passive film, with no Mo0 depletion in the modified alloy region underneath the oxide film at open circuit potential, and under anodic passivation. Mo4+/6+ enrichment improves protectiveness against transient active dissolution during the active/passive transition.

The influence of picosecond laser generated periodic structures on bacterial behaviour

The formation of a biofilm is preceded by bacterial retention and proliferation on a surface. Biofilm development on surfaces can cause numerous issues in terms of fouling and bacterial transmission and contamination. The design and fabrication of surfaces that prevent bacterial retention and biofilm formation may provide a potential solution to reduce bacterial fouling of surfaces. An EdgeWave, Nd:YVO4 picosecond laser was used to generate two periodic surface topographies on 316L stainless steel surfaces with and without fluoroalkylsilane (FAS) treatment. These were characterised using Optical Laser Microscopy (OLM), Scanning Electron Microscopy (SEM), contact angle measurements, and Energy Dispersive X-ray Spectroscopy (EDX). The surface wettability and retention of Escherichia coli bacteria on the laser generated surfaces were analysed over one month. Without chemical treatment, and with increasing the time to one month, the results showed that the wettability of laser treated surfaces was decreased as was subsequent bacterial retention. However, the control surface recorded the lowest number of adhered bacteria. After reducing the surface tension, the number of bacteria retention was decreased on all surfaces and one of laser generated surfaces which presented higher contact angle and lower surface tension components (CA = 132°, ΔGiwi = −85.26, γs = 13.81, γsLW = 13.37, and γs− = 0.13) recorded the minimal number of bacteria retention. The results showed that reducing the surface tension played an important role which reduced bacterial fouling.

Synthesis and Characterization of New Polymers Bearing Tetrazole and Triazole Moieties with Studying their Corrosion Protection of Stainless Steel Surface in Hydrochloric Acid

A series of polymers containing1,2,4-triazole and tetrazole groups in their main chains were synthesized through several steps. Poly(acryloyl hydrazide) was first prepared and then subjected to a hydrazide reaction with phenyl isothiocyanate to give a 1,2,4-triazole ring (2). This polymer was introduced into a reaction with chloro acetylchloride to yield polymer (3), which was refluxed with sodium azide to give polymer (4). Polymer (5) was synthesized by the reaction of polymer (4) with acrylonitrile in the presence of NH4Cl as a catalyst. Finally, polymer (6) was synthesized by the electrochemical polymerization of polymer (5) using 316L stainless steel as an anti-corrosion coating. Polymer-coated and uncoated stainless steel was tested for corrosion safety in a solution of 0.1 M HCl, followed by Tafel and Potentiostatic procedures at a temperature of 293 K. Nano materials such as ZnO were applied to the monomer solution at different concentrations to enhance the corrosion resistance of the 316L stainless steel surface. The results showed that the performance values of corrosion protection for the polymer coating were increased with the introduction of the nano materials. Furthermore, 13C-NMR, 1H-NMR, and FTIR were recorded to confirm the structures of the poylmers, while their physical properties were tested using atomic force microscope (AFM) and scanning electron microscope (SEM).

Characterization of Magnetoelectropolished Stainless Steel Surfaces’ Texture by Using the Angle-Resolved Scattering and Image Processing Analysis Methods

In this article, the results of preliminary experimental studies related to a fast, non-contact assessment of the AISI 316L stainless austenitic steel surfaces after electrochemical polishing in a magnetic field have been presented. The experiments were realized with the use of a modified angle-resolved scattering (ARS) method based on the analysis of angular distribution of the scattered light intensity. Digital images of such distribution were acquired for selected areas of examined samples—base surface and surface after magnetoelectropolishing (MEP) process. Parametric analysis oriented toward the calculation of selected key geo- and photometric parameters carried out in Image Pro®-Plus software allowed for characterization of the surface conditions of the assessed samples in terms of their scattering properties. The obtained experimental results confirmed the usefulness of the ARS method used in the presented studies as well as the possibility of its practical use (after appropriate modifications) on a wider scale, especially in industrial applications.

Anti-corrosion and corrosive wear properties of AISI 316L stainless steel with surface nanocrystallization by surface mechanical rolling treatment

In this work, surface mechanical rolling treatment (SMRT) was adopted to obtain the gradient nanostructured (GNS) layer on AISI 316L stainless steel (SS) surface. To evaluate the effect of the GNS, anti-corrosion and corrosive wear tests of the SMRT sample were conducted in pure water and corrosive medium in comparison with a unSMRT (i.e., coarse-grained 316L SS). The corrosion behaviors, tribological properties, damage mechanism as well as relation of pitting and delamination, have been investigated to clarify their synergetic effects and failure mechanism. The results show that, the GNS of 316L SS has poor corrosion resistance due to initiation in local of stress corrosion crack (SCC). However, in comparison with the unSMRT sample, the pitting resistance of 316L SS after SMRT is significantly enhanced. For both samples, the wear loss by delamination is obviously accelerated by corrosion in the friction process. The tribo-corrosion resistance is markedly enhanced with the GNS layer relative to the unSMRT sample, the GNS layer can effectively inhibit the formation of delamination in the corrosive environment, and can also mitigate the abrasive wear in the water lubrication condition, due to the beneficial combination of superfine nanocrystalline structure and high hardness of the GNS layer.

The Effect of H2S Pressure on the Formation of Multiple Corrosion Products on 316L Stainless Steel Surface.

H2S gas when exposed to metal can be responsible for both general and localized corrosion, which depend on several parameters such as H2S concentration and the corrosion product layer formed. Therefore, the formation of passive film on 316L steel when exposed to H2S environment was investigated using several analysis methods such as FESEM and STEM/EDS analyses, which identified a sulfur species underneath the porous structure of the passive film. X-ray photoelectron spectroscopy analysis demonstrated that the first layer of CrO3 and Cr2O3 was dissolved, accelerated by the presence of H2S-Cl−. An FeS2 layer was formed by incorporation of Fe and sulfide; then, passivation by Mo took place by forming a MoO2 layer. NiO, Ni(OH)2, and NiS barriers are formed as final protection for 316L steel. Therefore, Ni and Mo play an important role as a dual barrier to maintain the stability of 316L steel in high pH2S environments. For safety concern, this paper is aimed to point out a few challenges dealing with high partial pressure of H2S and limitation of 316L steel under highly sour condition for the oil and gas production system.

Sticking Probability of Ammonia Molecules on Tungsten and 316L Stainless Steel Surfaces

We present measurements of the sticking probability of ammonia on two metals, tungsten and 316L stainless steel, covered with natural surface impurities as they will be used for the international n...

Effect of surface mechanical attrition treatment on stainless steel corrosion

ABSTRACT Surface mechanical attrition treatment (SMAT) is a unique method for the nanoscale refinement of a surface grain structure without changing the alloy chemical composition. Herein, the effect of SMAT on the corrosion resistance of 316L stainless steel in artificial sea water used as a corrosive medium has been investigated. As a result, a passive film and a nanostructured layer were formed on the SMAT-processed 316L stainless steel surface, which considerably increased its corrosion resistance during short-term testing. However, after a long-term exposure to the corrosive medium, the treated sample exhibited deterioration of its corrosion properties because of the micro-strain build-up and the presence of defects in the surface layer. The findings of this work suggest that SMAT can be potentially used for providing short-term corrosion protection to stainless steel objects immersed in aqueous saline media.

Reduction of Escherichia coli adhesion to AISI 316L stainless steel surface by using mechanical and electrochemical polishing processes

ABSTRACT This paper presents the role of surface roughness on the bacterial adhesion to the food-grade AISI 316L stainless steel surface, which was prepared by the mechanical and electrochemical polishing processes. Escherichia coli or E. coli was the bacteria tested in this study as it is a sanitization indicator in the food and pharmaceutical industries. The average surface roughness (Ra ), peak-to-valley roughness (Ry ), and five-point average roughness (Rz ) of the polished surface were measured, and the results demonstrated that the amount of E. coli was found to increase with the increased surface roughness. As per the electrochemical polishing process, the effects of applied voltage, electrolyte concentration, and polishing time on the three roughness parameters were examined. Besides the Ra , the influence of Ry and Rz on the bacterial adhesion was found to be very significant. By using the electrochemical process with a suitable polishing condition, the Ry and Rz were substantially reduced compared to the mechanically polished surface with the similar level of Ra . The amount of bacteria on the electrochemically polished surface was also lower than the mechanical one by 25% on average.

Preparation of crack-free TiO2 coating by active screen plasma annealing method

A novel approach has been developed to fabricate a thin layer of titanium oxide (TiO2) on the surface of 316L stainless steel by a combination of Sol-Gel method and subsequent active screen plasma annealing (ASPA) method. Dip coated layers were plasma annealed in a titanium cylindrical mesh from 300 to 500 ℃. The effect of ASPA temperature on the particles size, morphology, and crystallinity of the coating layers was studied in comparison with conventional annealing. Also, electrochemical impedance spectroscopy and potentiodynamic polarization were employed to study the corrosion behavior of both types of coatings. The results showed that, a crack-free TiO2 coating with a thickness of about 1–5 μm can be obtained using the ASPA method at different calcination temperatures. Plasma annealing led to the decline of calcination temperature and formation of nanostructured anatase phase with higher crystallinity and structural uniformity in comparison to conventional annealing method. Moreover, the corrosion resistance of the coating was significantly increased compared to conventional annealing method. It was found that, the coating of titanium oxide can reduce by eight-fold the corrosion rate of 316L stainless steel.

Galvanic corrosion of Type 316L stainless steel and Graphite in molten fluoride salt

The effect of Graphite on the corrosion of Type 316L stainless steel (SS) was investigated in molten FLiNaK (LiF-NaF-KF: 46.5−11.5−42 mol.%) salt using electrochemical methods. Results show that Type 316L SS and Graphite, when ohmically-coupled, are susceptible to galvanic corrosion in molten fluoride salts. The Graphite, with the more positive electromotive potential, acts as the cathode in the Type 316L SS/Graphite galvanic couple and accelerates the corrosion of the steel. The galvanic effect of Graphite on Type 316L SS in molten FLiNaK salt increase linearly with increasing Graphite/Type 316L SS surface area ratio, temperature, and moisture impurities of the salt.

Properties of a Plasma-Nitrided Coating and a CrNx Coating on the Stainless Steel Bipolar Plate of PEMFC

PEMFC are considered to be the most promising for automotive energy because of their good working effect, low temperature, high efficiency, and zero pollution. Stainless steel as a PEMFC bipolar plate has unparalleled advantages in strength, cost, and processability, but it is easy to corrode in a PEMFC working environment. In order to improve the corrosion resistance, the surface modification of 316L stainless steel is a feasible solution for PEMFC bipolar plates. In the present study, the plasma-nitrided coating and CrNx coating were prepared by the plasma-enhanced balanced magnetron sputtering technology on the 316L stainless steel surface. The microstructures, phase compositions, and corrosion resistance behavior of the coatings were investigated. The corrosion behavior of the prepared plasma-nitrided coating and CrNx coating was investigated by potentiodynamic polarization, potentiostatic polarization, and electrochemical impedance spectroscopy (EIS) in both cathodic and anodic environments. The experimental results show that corrosion resistance of the CrNx coating was better than the plasma-nitrided coating. It was indicated that the technology process of nitriding first and then depositing Cr was better than nitriding only.

Wear behavior of wire electric discharge machined surface of 316L stainless steel

This study presents the wear behavior of 316L stainless steel material machined with wire electric discharge machine (EDM) at different machining conditions by varying the machining parameters pulse on time (TON), peak current (IP), servo voltage (SV) and wire tension (WT). Sliding wear tests are conducted on the cylindrical specimens using pin on disc apparatus and the worn morphology of the specimens are analyzed by SEM and XRD. The experimental investigation revealed that the wear resistance is highly influenced by the wire EDM parameters. TON and IP are identified to be the most influencing factors effecting wear resistance. At similar values of the product of TON and IP, the wear resistance remained constant and the wear resistance increased with decrease in the product of TON and IP. The obtained parameters setting can be used in die making industries where wear behavior is of importance.

Structural, tribological and corrosion properties of plasma nitrided-chromized-316L stainless steel in air and artificial seawater

To improve the protective performance of 316L stainless steel surface in seawater, a series of modified layers on the 316L stainless steel were fabricated by plasma nitriding, vacuum solid powder chromizing and duplex surface treatment of nitriding-chromizing, respectively. The microstructure, mechanical properties, tribological properties and corrosion resistance of different modified layers were contrastively investigated. The results of x-ray diffraction (XRD) and transmission electron microscope (TEM) showed that the nitrided layer was mainly CrN and Fe4N phases, and the chromized layer was mainly Fe-Cr and Cr23C6 phases. The surface hardness of 316L stainless steel was improved to varying degrees by nitriding and chromizing due to the formation of hard phases such as CrN and Cr23C6 on the surface of 316L. The friction coefficient and wear rate can be obviously reduced by nitriding treatment. However, the nitriding treatment can cause the precipitation of Cr from the solid solution of 316L to form CrN, resulting in the decrease of corrosion resistance in seawater. In contrast, chromizing treatment can significantly improve the corrosion resistance of 316L by increasing the chromium content of stainless steel surface. The duplex surface treatment of nitriding and chromizing made the 316L stainless steel had the highest surface hardness and plastic deformation resistance and showed the excellent tribological properties in both atmosphere and seawater.

Multistep active screen plasma co-alloying the treatment of metallic bipolar plates

ABSTRACTActive screen plasma (ASP) surface treatments have been widely utilized to improve surface performances of stainless steel in various applications. In our previous research, active screen plasma nitriding (ASPN) and active screen plasma co-alloying processes have been successfully employed to modify 316L stainless steel for the application of proton exchange membrane (PEM) fuel cell bipolar plates. In this study, a multistep active screen plasma co-alloying surface treatment with niobium and nitrogen was proposed to produce a tailored layer structure on the surface of 316L stainless steel. By tailoring the applied bias of step, single-layer and duplex-layer structures can be formed on the surface of 316L stainless steel. Performance tests showed that the sample with a duplex-layer structure exhibited improved interfacial contact conductivity and higher corrosion potential than the sample with a single-layer structure, indicating the feasibility of this multistep active screen plasma co-alloying surface treatment for PEM fuel cell bipolar plate application.

Study of TiCu/TiCuN multilayer films with antibacterial activity

ABSTRACTObjective: Three differently designed multilayer films of TiCu/TiCuN multilayer (M1, M2, and M3) were deposited on 316L stainless steel surface using the axial magnetic field-enhanced arc ion plating (AMFE-ARP) method. The aim of this study was to investigate both cytocompatibility and antibacterial activity of the multilayer films.Methods: The antibacterial rate, attached bacteria and developed biofilms were studied from quantitative antibacterial test and bacterial morphological examination. The in vitro biocompatibilities of the films were systematically investigated by means of methods of CCK8 cell proliferation assay, phalloidin cytoskeleton staining and Annexin-V/PI flow cytometry.Results: The multilayer film of M2 revealed a better cytocompatibility and antibacterial activity than the others. The M2 film is suggested to be much application potential as antibacterial films on the biomedical implants.

Ion Transport Mechanisms in the Oxide Film Formed on 316L Stainless Steel Surfaces Studied by ToF-SIMS with 18O2 Isotopic Tracer

The composition and structure of the native and passive oxide films formed on 316 L stainless steel have been studied in situ by ToF-SIMS. High temperature re-oxidation experiments in isotopic 18O2 gas have also been done to assess the ion transport mechanisms in the native and passive oxide films. Duplex oxides with an inner Cr rich layer and an outer layer rich in Fe and Mo oxide have been observed on native and passive oxide films. Exposure of the oxide films to isotopic 18O2 tracer at 300 °C reveals that the outward cationic diffusion governs the inner oxide growth. The outer Mo-rich layer prevents the continued transport of Cr to the outermost surface. The passive film, due to its composition and structure, exhibits a markedly lower oxidation rate compared to native oxide films.

Preparation and properties of FeAl/Al2O3 composite tritium permeation barrier coating on surface of 316L stainless steel

In fusion reactors, preparing barrier coatings on the surface of steel structures is one of the most effective ways to reduce the penetration of hydrogen and its isotopes. An FeAl/Al2O3 composite tritium permeation barrier is a good choice for the current tritium permeation prevention technology because it has low enthalpy permeability, small thermal mismatch, good compatibility with lithium lead, and metallurgical bonding. In this study, FeAl/Al2O3 composite tritium permeation barrier coating was successfully prepared on the surface of 316L stainless steel by embedding method combined with in-situ thermal oxidation. By using test methods, such as TEM, SEM, EDS, and XRD, we found that the FeAl alloy transition layer was successfully formed on the surface of the aluminized matrix, thereby effectively relieving the thermal mismatch between the Al2O3 coating and the substrate. The results showed that the thickness of the aluminum-rich layer and the FeAl transition layer on the surface of the substrate were approximately 32 μm and 8 μm, respectively. In addition, α-Al2O3 layer formed on the surface of the aluminum-rich layer after oxidation was approximately 4 μm thick. According to the scratch test, the bond strength of the coating showed that the adhesion of the FeAl/Al2O3 composite coating was 52.4 N. The hydrogen permeation test results showed that the FeAl/Al2O3 composite coating remarkably improved the hydrogen barrier properties of the 316L stainless steel matrix.

Thermal stability of the passive film formed on 316L stainless steel surface studied by ToF-SIMS

The modifications of the passive film formed on 316 L stainless steel surface during stepwise heating in ultra-high vacuum up to 300 °C have been studied in situ by ToF-SIMS. The pre-formed passive film (in 0.05 M H2SO4) has a bilayer structure, comprising Fe-rich, Mo-rich (outer) and Cr-rich (inner) layers. Below 100 °C, the passive film is stable. At 100 °C–250 °C, dehydroxylation and dehydration is observed. Above 250 °C, the main modification in the film is formation of chromium oxide at the expense of oxidized iron. At higher temperature, thicker Cr-rich inner layer with sharper inner/outer oxide interface is formed.

SURFACE MORPHOLOGY AND MICROHARDNESS BEHAVIOR OF 316L IN HAP-PMEDM

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.