Surface Of 316L Stainless Steel Research Articles

Electrochemical characteristics and damage behaviour of DLC-coated 316L stainless steel for metallic bipolar plates of PEMFCs

ABSTRACT A diamond-like carbon (DLC) coating was deposited on the surface of 316L stainless steel using the arc ion plating (AIP) method to improve the life and efficiency of the metallic bipolar plate for polymer electrolyte membrane fuel cells (PEMFCs). The electrochemical characteristics and damage behaviour were investigated in an accelerating solution simulating the PEMFCs operation environment. A result of the experiment showed the corrosion current density of all specimens with DLC coatings was lower than that of the base metal. However, when the thickness of the DLC coating was 0.3 and 0.5 μm, the corrosion resistance was lower than that of the base metal. This is thought to be because defects on the coating surface result in crevice corrosion of the gap between the coating layer and the intermediate layer or between the coating layer and the base metal, further accelerating corrosion.

Investigation of coated 316L steel surface: Surface morphology, composition, corrosion, and biocompatibility using hydroxyapatite mixed-EDM process

316L stainless steel belongs to insufficient biological responses and corrosion resistance. Although hydroxyapatite powder (HAp)-based coating improves biological responses and corrosion resistance of the 316L stainless steel, these coatings have resulted in inferior adhesion strength and cracked surface. This study aims to synthesize a highly biocompatible and corrosion resistant coating on the 316L stainless steel with a high adhesion strength and surface integrity using the electro discharge machining (EDM) method. The study also aims to explore the impacts of process parameters on the surface features. To reach the set objectives, several characterisation methods including atomic force microscopy (AFM), scanning electronic microscopy (SEM), X-ray powder diffraction (XRD), Potentiostat (electrochemical cell), MTT assay and X-ray photoelectron spectroscopy (XPS) were adopted. The HAp-mixed EDM method synthesized a biocompatible and corrosion resistant coating with an average thickness of 14.6 μm and 20.8 MPa adhesion strength comprising of Ca-P based oxides and carbides. The modified surface showed nano surface roughness of 18.5 nm. The oxides and carbides formed in the coating improved the cell viability of 316L stainless steel surface to 87 % and corrosion resistance to 0.00123 mm per year. This study is trying to gain the attention of 316L stainless steel-based bioimplant manufacturers to launch the hydroxyapatite mixed-EDM method for concurrent machining and coating.

A tribological study of shot peening process on stainless steel

The goal of this study is to figure out how to use the microstructure, friction, and wear parameters of a shot-peened stainless steel 316L surface to study tribology. Tribology is the study of how moving parts rub against each other, wear out, and are oiled. Tribology looks at all of these things from a mechanical point of view. Improves the surface and frictional properties of materials, making them less likely to break and giving them a longer life. Because of this, it can make materials smoother and less likely to stick together. This is possible because it can improve the properties of many different materials. Shot peening is a type of cold working technique that can change the mechanical properties of materials like metals and composites. Because shot peening is a part of the peening process, this improvement is possible. Also, as a direct result of the result, a layer of compressive residual stress will form in the material. Before the process can be finished, the surface of the SS316L needs to be honed with abrasive sheets and a double-disc polishing machine. Next, a Vickers hardness test is done on the material, and then a pin-on-disc tribometer is used to study how the material wears. At the end of the process, a trinocular microscope is used to look at the structure of the substance being studied on a small scale.

Study of wear processes generated by cavitation phenomena produced by laser induced dielectric breakdown on borided and non-borided 316L stainless steel surfaces in bi-distilled water

This work presents a study of the wear of borided and non-borided 316L stainless steel surfaces produced by the cavitation and thermal effects caused by the laser induced dielectric breakdown using bi-distilled water as the dielectric medium. A pulsed beam of a high-power laser was focused at a different distance between the surfaces and the focus spot in a parallel configuration. The wear produced on the non-borided surface presented the combination of both cavitation and thermal effects that decreased with the increase of the surface-focus spot distance. On the other hand, the borided surfaces showed a higher thermal resistance due to that worn areas presented just the erosion of the material by the cavitation process, as revealed by the microstructure of the boride surfaces.

Effect of WC Content on Microstructure and Properties of CoCrFeNi HEA Composite Coating on 316L Surface via Laser Cladding.

Laser cladding technology is used to fabricate CoCrFeNi HEA/WC composite coatings with different mass fractions of WC on the surface of 316L stainless steel. The microstructures of HEA/WC composite coatings were analyzed by combining multiple characterization techniques. The results show that the HEA/WC composite coatings have good surface formation without pores and hot cracks, and the metallurgical bonding is well formed between the coating and the 316L SS substrate. Under the action of a laser beam and molten pool, WC particles partially or slightly melt and diffuse to the matrix, which hinders the orderly growth of grains and forms multiple strengthening. The phase structure of the HEA/WC composite coatings is composed of a main phase with FCC. The hardness and corrosion resistance of the HEA/WC composite coatings are clearly enhanced, and the HEA/WC composite coating with 5% WC has optimum properties.

Effects of Nano-CeO2 on Microstructure and Properties of WC/FeCoNiCrMo0.2 Composite High Entropy Alloy Coatings by Laser Cladding

FeCoNiCrMo0.2 high entropy alloy has many excellent properties, such as high strength, high wear resistance, high corrosion resistance, and high ductility. To further improve the properties of this coating, FeCoNiCrMo high entropy alloy (HEA) coatings, and two composite coatings, FeCoNiCrMo0.2 + WC and FeCoNiCrMo0.2 + WC + CeO2, were prepared on the surface of 316L stainless steel by laser cladding technology. After adding WC ceramic powder and CeO2 rare earth control, the microstructure, hardness, wear resistance, and corrosion resistance of the three coatings were carefully studied. The results show that WC powder significantly improved the hardness of the HEA coating and reduced the friction factor. The FeCoNiCrMo0.2 + 32%WC coating showed excellent mechanical properties, but the distribution of hard phase particles in the coating microstructure was uneven, resulting in unstable distribution of hardness and wear resistance in each region of the coating. After adding 2% nano-CeO2 rare earth oxide, although the hardness and friction factor decreased slightly compared with the FeCoNiCrMo0.2 + 32%WC coating, the coating grain structure was finer, which reduced the porosity and crack sensitivity of the coating, and the phase composition of the coating did not change; there was a uniform hardness distribution, a more stable friction coefficient, and the flattest wear morphology. In addition, under the same corrosive environment, the value of polarization impedance of the FeCoNiCrMo0.2 + 32%WC + 2%CeO2 coating was greater, the corrosion rate was relatively low, and the corrosion resistance was better. Therefore, based on various indexes, the FeCoNiCrMo0.2 + 32%WC + 2%CeO2 coating has the best comprehensive performance and can extend the service life of 316L workpieces.

Biocompatibility evaluation, wettability, and scratch behavior of Ta-coated 316L stainless steel by DC magnetron sputtering for the orthopedic applications

As 316L stainless steel is widely used in manufacturing biomedical devices such as hip joints, screws, and plates, these devices are likely to fail soon after implantation due to inadequate biological reactions. To address these issues, a coating was deposited on 316L SS to increase biocompatibility and hydrophilicity. Tantalum (Ta) coating for 15, 30, and 60 min (1.504 μm, 3.809 μm, and 6.083 μm thickness, respectively) were applied on the surface of 316L stainless steel by DC Magnetron Sputtering, followed by biocompatibility, Wettability, and scratch test investigations. The biocompatibility was determined through cell culture experiments (1, 7, and 14 days) on human osteoblast MG 63 cells and showed improved cell adherence, proliferation, and differentiation compared to bare 316L SS. Despite the ability to create highly adhering coatings of both aspects, studies on adhesion using a scratch test revealed significantly better adhesion strength (7μN, 17μN, and 23μN with ±0.296 μN) at coated surfaces. The surface characteristics of the Ta-coated and bare 316L SS were characterized using various techniques such as optical microscopy, energy dispersive x-ray spectroscopy, inductively coupled plasma mass spectroscopy, and scanning electron microscopy. Based on the results, the Ta-coated 316L stainless steel is considered a promising material for orthopedic applications due to its improved biocompatibility and surface properties.

Two-step electropolishing of internal surfaces of 316L stainless steel made by laser-based powder bed fusion

Investigating electropolishing (EP) effects on the material removal process of laser-based powder bed fused internal surfaces is crucial for the application of EP in the polishing of complex internal structures. This study aims to electropolish various internal surfaces of 316L stainless steel fabricated by laser-based powder bed fusion (L-PBF). Un-sintered powders and sintered area on top, face up, side and face down internal surfaces were characterized. Based on the material removal characteristics of different surface features, a two-step EP was proposed using different potentials and polishing time for L-PBF internal surfaces after parametric study in a developed EP system which is capable of circulating electrolytes in high-speed. Material removal process and anodic dissolution of L-PBF internal surfaces were then discussed based on experimental results and impedance analysis. The comprehensive characterizations of morphology, roughness and cross sections with microstructure differences in consideration are important for analyzing the evolution of L-PBF surfaces during polishing. The study demonstrates the high efficiency of the two-step EP in polishing various L-PBF internal surfaces.

Anodized Nanostructured 316L Stainless Steel Enhances Osteoblast Functions and Exhibits Anti-Fouling Properties.

Poor osseointegration and infection are among the major challenges of 316L stainless steel (SS) implants in orthopedic applications. Surface modifications to obtain a nanostructured topography seem to be a promising method to enhance cellular interactions of 316L SS implants. In this study, arrays of nanodimples (NDs) having controlled feature sizes between 25 and 250 nm were obtained on 316L SS surfaces by anodic oxidation (anodization). Results demonstrated that the fabrication of NDs increased the surface area and, at the same time, altered the surface chemistry of 316L SS to provide chromium oxide- and hydroxide-rich surface oxide layers. In vitro experiments showed that ND surfaces promoted up to a 68% higher osteoblast viability on the fifth day of culture. Immunofluorescence images confirmed a well-spread cytoskeleton organization on the ND surfaces. In addition, higher alkaline phosphate activity and calcium mineral synthesis were observed on the ND surfaces compared to non-anodized 316L SS. Furthermore, a 71% reduction in Staphylococcus aureus (S. aureus) and a 58% reduction in Pseudomonas aeruginosa (P. aeruginosa) colonies were observed on the ND surfaces having a 200 nm feature size compared to non-anodized surfaces at 24 h of culture. Cumulatively, the results showed that a ND surface topography fabricated on 316L SS via anodization upregulated the osteoblast viability and functions while preventing S. aureus and P. aeruginosa biofilm synthesis.

Effect of laser texturing bulges on tribological properties of 316L stainless steel

The laser surface texture process will inevitably produce the edge of material surface texture bulges. Currently, laser processing bulges are generally polished directly, but this method ignores its impact on the friction pairs. In this paper, the tribological properties of polished and unpolished textured surfaces were investigated under dry friction, oil lubrication, and seawater lubrication conditions using three shapes of texture (grooves, square pits, and round pits) prepared on the surface of 316L stainless steel. The results show that the polished surface of 316L stainless steel texture increases wears, and the friction mechanism is mainly adhesive wear, while the unpolished surface of the texture has less wear, and the friction mechanism is mainly abrasive wear. The method and principle of using machining bulges to improve the wear resistance of friction pairs are discussed to address the differences in the tribological performance of entire friction pairs due to the influence of machining bulges of different shapes of texture.

Optimization of Quench Polish Quench (QPQ) Coating Process Using Taguchi Method

In this research, the thickness of coating layer and hardness of coated 316L stainless steel surface has been improved by Quench Polish Quench (QPQ) coating process. The influences of nitriding Temperature(T), nitriding time(tc), and Oxidation time(to) on hardness and thickness of coated surface have also been investigated using Taguchi method. During this process, the percentage of carbonate and cyanate, post oxidation temperature, and time are constantly maintained. The experimental investigations have been performed using the Taguchi analysis to examine the effects and to predict the combination of optimum processing time settings. The nitriding time and temperature are significantly contributed to the hardness and maximizing the thickness respectively. The level-3 of all process parameters has been recommended to maximize the hardness (800 Hv) and layer thickness (19.6 µm). The microstructure of the Layer thickness on the coated stainless-steel surface has been illustrated using a Scanning Electron Microscope (SEM) image.

Microstructures and Mechanical Properties of an AlCoCrNiFe HEA/WC Reinforcing Particle Composite Coating Prepared by Laser Cladding.

In this study, an AlCoCrFeNi HEA coating with a 10% mass fraction of WC particles was fabricated on the surface of 316L stainless steel by laser cladding technology. WC powders were formed by the partial or total dissolution of the initial WC particles with different sizes in the AlCoCrFeNi HEA coating. Micron WC particles were dispersed in the coating homogeneously, and millimeter WC particles were deposited on the bottom of coating because of their high density. The addition of the WC powers prompted Columnar dendritic and cellular grains, observed in the bottom and top regions of the coating, respectively. Additionally, this led to a higher micro-hardness and better corrosion resistance than that of the pure HEA coating.

Oral microbiota accelerates corrosion of 316L stainless steel for orthodontic applications

• Multi-species biofilms well attach to the surface of 316L SS. • Oral microbiota accelerates the corrosion of 316L SS. • Oral microbiota causes severe pitting corrosion of 316L SS. • Electroactive microorganisms are detected in the multi-species biofilms. In this work, microbiologically influenced corrosion (MIC) of 316L stainless steel (SS) caused by oral microbiota was investigated with HOMINGS 16S rRNA gene sequencing technology, and electrochemical and surface analysis techniques. The results showed that oral microbiota from different subjects developed multi-species biofilms with significant differences in structure and composition of bacteria strains on the 316L SS coupons. In the presence of oral microbiota, more severe pitting corrosion and faster dissolution of metallic ions including Ni and Cr were observed. The biofilm considerably decreased the pitting potential of 316L SS from 1268.0 ± 29.1 mV vs. SCE (abiotic control) to less than 500 mV vs. SCE. The corrosion current density in the presence of oral microbiota from subject 1 (115.3 ± 83.3 nA cm −2 ) and subject 2 (184.4 ± 162.0 nA cm −2 ) was at least 4 times more than that in the abiotic medium (28.0 ± 2.3 nA cm −2 ). The electroactive microorganisms with the potential to facilitate corrosion via extracellular electron transfer found in oral microbiota may be mainly responsible for the accelerated corrosion.

Mechanism of laser-chemical process to remove of oxide layer and formation of periodic microstructures for drag reduction

The paper presents a novel method of combining nanosecond (ns) pulse laser ablation (LA) with chemical etching (CE) to prepare controllable periodic microstructures on 316L stainless steel surface, which utilized the intrinsic thermal effect of ns pulse laser in processing materials. The microstructures were generated by LA, and CE removed the surface oxides and residues to make the microstructures appear. The experiments demonstrated that the size and period of microstructures can be easily controlled by adjusting the ns laser average power and scanning interval. Moreover, the grain refinement caused by the thermal effect in the LA process increased the hardness of processed area from 181 HV to 295.7 HV. The surface treated by laser ablation-chemical etching (LACE) process became hydrophobic or even superhydrophobic after being stored in an ambient atmosphere for 5 days without hydrophobic reagent treatment. When the laser average power was 17.5 W and the scanning interval was 80 μm, the contact angle on the surface was 158.6°. Compared with the polished surface, the fluid can achieve an effective slip length of 17 μm on the samples prepared by the LACE process. Hence, the periodic microstructures prepared by LACE has great potential in the self-cleaning, drag reduction application.

Effects of controlled shot peening on multi-scale morphology and hydrophobicity of 316L stainless steel

In this study, we used shot peening-etching method to construct the multi-scale morphology on the surface of 316L stainless steel, assisted by surface modification to improve hydrophobicity. The effects of the diameter of projectile (0.2, 0.3, 0.4 mm) and shot peening time (1, 1.5, 2, 2.5 min) on the multi-scale morphology and hydrophobicity of the samples were studied. Meanwhile, the surface morphology was examined by metallographic microscope (OM) and scanning electron microscope (SEM). The surface profile and roughness were characterized by laser scanning confocal microscope (LSCM). The fractal dimension D was calculated by data analysis software, and the static contact angle measuring instrument was used to evaluate the hydrophobic performance. The results show that the smaller the diameter of projectile is, the stronger the hydrophobicity of the sample is, and there is the best time for shot peening. Moreover, the size and distance of pits on the surface decrease as the diameter of projectile decreases. The roughness of the surface shows a tendency to increase first and decrease with the increase of shot peening time, and the contact angle has the same tendency. The contact angle of the sample surface increases as the fractal dimension D increases. When the diameter of the projectile is 0.2 mm and the shot peening time is 2 min, after etching and surface modification, the static contact angle is 137.4° and the solid-liquid contact area is only 15.4%. This method has the advantages of low cost, high efficiency and environment-friendly, which is beneficial to the large-scale production of hydrophobic materials.

Thermo‐penetrative spreading behaviours of oil in lasered microgrooves on stainless steel 316L surfaces

AbstractThe thermo‐penetrative spreading behaviours of oil in microgrooves on stainless steel 316L surfaces were studied experimentally under temperature gradient conditions. An interface of smooth surface and microgrooved surface was designed to comparatively investigate the penetrative spreading of oil in microgrooves and the apparent spreading of oil on microgrooves and smooth surfaces. Then, microgrooves with different depths but a same width were laser processed to analyse the relationship between the actions of surface texture and temperature gradient on oil directional spreading. Results showed that the apparent oil on microgrooves extended directionally along the temperature gradient, leading to the lubricant loss from the high‐temperature region to the lower, while the penetrative oil in microgrooves could spread rapidly from the low‐temperature region to the higher under the obstruction of the thermocapillary effect, providing a potential method to enhance the lubrication.

Effect of Texturing Environment on Wetting of Biomimetic Superhydrophobic Surfaces Designed by Femtosecond Laser Texturing.

Inspired by Euphorbia leaves, micrometric pillars are designed on 316L stainless steel surfaces using a femtosecond laser to achieve superhydrophobicity. In this study, we focus on wetting behavior evolution as a function of time and chemical environment. Two types of texturing designs are performed: the laser texturing of micrometric square pillars, and the laser texturing of micrometric square pillars whose tops were irradiated using various fluences to obtain a different topography on the nanometric scale. Two laser texturing environments are considered in both cases: a CO2 flow and ambient air. The main result is that 250 days after laser texturing, steady-state contact angles (SSCA) were above 130° no matter what the environment was. We also study the effect of regular wetting over time. Comparing the results of surfaces for which wetting over time was conducted and that of the undisturbed surfaces for 250 days demonstrates that performing wetting measurements when the surface is not stable led to major changes in droplet behavior. Our surfaces have a unique wettability in which droplets are in an intermediate state. Finally, using a CO2 flow did not help reach higher SSCA, but it limited the effect of regular wetting measurements.

Capacitor lifetime prolonged by addition of organic ammonium salt with cyclohexyl substituent and 2,5-dihydroxybenzenesulfonic anion

It is well known that the electrochemical corrosion negatively affects the functional properties of metal and steel materials that constitute a part of systems conducting electric charge. On the other hand, the phenomenon of corrosion is rarely associated with the degradation of chemical power sources and energy storage devices. This article is aimed to fill this gap by describing the effect demonstrated by a substituted ammonium salt with cyclohexyl substituent and 2,5-dihydroxybenzenesulfonate anion used as a corrosion inhibitor in symmetrical electrochemical capacitor system. The accelerated ageing test of capacitor systems has shown that the addition of substituted ammonium salt to capacitor electrolyte allows to extend the service lifetime of the entire system by inhibiting the corrosion of 316L stainless steel current collectors. The inhibitory effect of substituted ammonium salt additives on the electrochemical corrosion of 316L stainless steel surface has been also confirmed by cyclic potentiodynamic polarization (CPP) tests and X-ray photoelectron spectroscopy (XPS) measurements.

Evaluation of corrosion resistant, antimicrobial and cytocompatible behaviour of cobalt based metallosurfactants self-assembled monolayers on 316L stainless steel surface

The present research is aimed at developing a more economic and ecological way to improve the biocompatibility of medical-grade stainless steel. In order to accomplish the purpose, the 316L stainless steel has been functionalized by depositing self-assembled monolayers (SAMs) of cost-effective Cobalt-based metallosurfactants (CoMS). The fabrication of well-defined SAMs on the surfaces was characterised using FTIR-ATR, spectroscopic ellipsometry and water contact angle measurements. The corrosion stability of functionalized surfaces in simulated body fluid was accessed by various electrochemical and spectroscopic techniques like cyclic potentiodynamic polarisation (CPP), chronoamperometry, electrochemical impedance spectroscopy, FE-SEM, XPS and ICP-MS studies. The metallosurfactant SAMs provided superior corrosion and bacterial protection especially against Gram-negative E. coli bacteria. The cytotoxicity of the SAMs against mouse embryonic fibroblast cell line (NIH-3T3) was assessed by MTT and fluorescent assays. The experimental results reveals that the metallosurfactant SAMs are multifunctional i.e., they enhanced the anticorrosive and anti-bacterial properties of the SS 316L without compromising the cytocompatibility of the surface which make them promising candidates for biomedical applications.

Improvement of Structures and Properties of Al2O3 Coating Prepared by Cathode Plasma Electrolytic Deposition by Incorporating SiC Nanoparticles

A serious issue in the preparation of Al2O3 coatings by cathode plasma electrolytic deposition (CPED) is that the coatings have a porous structure, which is detrimental to their protective performance. Therefore, to address this problem, SiC nanoparticles are incorporated into the Al2O3 coating in this study. A series of Al2O3–SiC composite coatings are efficaciously prepared on the surface of 316L stainless steel by CPED. The microstructures, compositions and phase components of the composite coatings are characterized; the electrochemical corrosion resistance and tribological behavior are evaluated; and the mechanism of SiC nanoparticles in the coating formation process is discussed in detail. The results indicate that the Al2O3 coating prepared by CPED consists of α-Al2O3 and γ-Al2O3, and the former is the main crystalline phase. With the incorporation of SiC nanoparticles in the coating, the content of α-Al2O3 gradually decreases, almost disappearing, accompanied by an increase in γ-Al2O3 as the main crystalline phase. The incorporation of SiC nanoparticles significantly reduces the surface irregularity and roughness of Al2O3 coatings and remarkably improves the corrosion resistance and wear resistance of the Al2O3 coatings. The improvement in corrosion resistance and anti-wear properties can be explained by the fact that the SiC nanoparticles effectively weaken electrical breakdown and increase the compactness of the coatings.