316L SS Research Articles

The effect of Nb content on microstructure and properties of laser cladding 316L SS coating

316L SS with different Nb content (0.2, 0.5, 1.0, 3.0, 5.0, 7.0 wt%) coatings were fabricated on Q235 steel plate by laser cladding. The addition of Nb made the phase structure of 316L change from FCC to FCC + BCC + Laves phase . With the Nb content increasing, the microhardness of 316L coating increased gradually. The Nb7.0 coating is about 2.0 times as hardness of the substrate. Electrochemical testing showed that Nb 1.0 coating had the best corrosion resistance in 3.5 wt% NaCl solution. Excess Nb will cause corrosion to occur more easily and decrease the corrosion resistance of the coating. • The compact 316L SS with dissimilar Nb alloy coating was prepared by laser cladding. • The Nb1.0 coating has good corrosion resistance in 3.5 wt% NaCl solution. • Niobium oxide played an important role in improving the corrosion resistance of passive film, but excessive niobium will have adverse effects on the structure. • The Nb7.0 coating has high microhardness.

A comprehensive model to predict friction factors of fluid channels fabricated using laser powder bed fusion additive manufacturing

Laser powder bed fusion (L-PBF), or selective laser melting, can be used to significantly reduce the size and weight of hydraulic components. However, the current design approach still greatly depends on the technician’s experience. The friction loss of the L-PBF fabricated fluid channels is greatly affected by the fabrication quality but remains unknown, which is essential for the design approach. In this study, circular 316L SS fluid channels with various diameters (4–10 mm) and build angles (0–90°) were fabricated using L-PBF. Fabrication quality was characterized, and the friction factors were measured and analyzed. The results indicate that the geometric tolerance and surface roughness are closely related to the build angle. The friction factor of the L-PBF fabricated channels, which is higher than the classical theory in the turbulent flow, is influenced by both channel diameters and build angles. A comprehensive model is developed to predict friction factors of the L-PBF fabricated fluid channels. Design guidelines of fluid channels are proposed, for the first time, by considering both fabrication quality and friction factors. • The influence of build angle on channel forming quality is studied. • The relationship between forming quality and friction factor is developed. • A comprehensive friction factor prediction model for 316L SS L-PBF channel is developed. • Design guidelines of L-PBF fabricated fluid channels are proposed.

CMT-Based Wire Arc Additive Manufacturing Using 316L Stainless Steel (2): Solidification Map of the Multilayer Deposit

This study aimed to suggest a solidification map based on the solidification parameters G and R of each layer in the multilayer deposition for the investigation of heat accumulation on the deposit. Through the solidification map, the appropriate solidification conditions of the microstructure were determined. In order to investigate the solidification parameters, the temperature profile of the deposit was experimentally acquired during deposition. A simulation model reflecting the characteristics of the deposition process was developed and verified. The solidification parameters from the simulation model and the microstructure from experiments were correlated. Based on the analysis, a solidification map of 316L SS processed with CMT-WAAM process was derived, which is suggested as a guide for controlling and predicting the morphology of the microstructure in the deposit.

Data on corrosion inhibition effect of Stylosanthes gracilis extract on UNS S30403 austenitic stainless steel in dilute acid solution

This article presents data on the evaluation of Stylosanthes gracilis extract as corrosion inhibitor for 304 L in H2SO4 solution. The data were obtained from weight loss measurements, energy dispersive spectroscopy and X-ray diffraction studies. The extract reduced the rate of corrosion on SS 304l in H2SO4 solution at an optimum concentration of 1.2 g/L with inhibition efficiency of about 87.81% and corresponding surface coverage of 0.878. The corrosion rate of 0.232 mm/yr was observed in the inhibited sulphuric acid as against 1.904 mm/yr in the blank acid respectively at 240 h of exposure of the specimens. At 2400 h of exposure, the observed corrosion rate was 0.228 mm/yr with an efficiency of 74.21%. Whereas the extract's efficacy was slightly influenced by time, concentration has a profound effect on the extract's protection capability. The decrease in the efficiency of the extract after 2400 h is 13.6% suggesting the good stability with time.

Influence of High-Pressure Torsion on the Microstructure and Microhardness of Additively Manufactured 316L Stainless Steel

High-pressure torsion (HPT) is known as an effective severe plastic deformation (SPD) technique to produce bulk ultrafine-grained (UFG) metals and alloys by the application of combined compressive force and torsional shear strains on thin disk samples. In this study, the microstructures and microhardness evolution of an additively manufactured (AM) 316L stainless steel (316L SS) processed through 5 HPT revolutions are evaluated at the central disk area, where the effective shear strains are relatively low compared to the peripheral regions. Scanning electron microscopy (SEM) analysis showed that the cellular network sub-structures in AM 316L SS were destroyed after 5 HPT revolutions. Transmission electron microscopy (TEM) observations revealed non-equilibrium ultrafine grained (UFG) microstructures (average grain size: ~115 nm) after 5 revolutions. Furthermore, energy dispersive x-ray spectroscopy (EDX) analysis suggested that spherical Cr-based nano-silicates are also found in the as-received condition, which are retained even after HPT processing. Vickers microhardness (HV) measurements indicated significant increase in average hardness values from ~220 HV before HPT processing to ~560 HV after 5 revolutions. Quantitative X-ray diffraction (XRD) patterns exhibit a considerable increase in dislocation density from ~0.7 × 1013 m−2 to ~1.04 × 1015 m−2. The super-high average hardness increment after 5 HPT revolutions is predicted to be attributed to the UFG grain refinement, significant increase in dislocation densities and the presence of the Cr-based nano-silicates, according to the model established based on the linear additive theory.

High-manganese and nitrogen stabilized austenitic stainless steel (Fe–18Cr–22Mn–0.65N): a material with a bright future for orthopedic implant devices

The rationale behind the success of nickel free or with extremely low nickel austenitic high manganese and nitrogen stabilized stainless steels is adverse influences of nickel ion on human body. Replacement of nickel by nitrogen and manganese provides a stable microstructure and facilitates better biocompatibility in respect of the conventional 316L austenitic stainless steel (316L SS). In this investigation, biocompatibility of the high-manganese and nitrogen stabilized (Fe–18Cr–22Mn–0.65N) austenitic stainless steel was studied and found highly promising. In vitro cell culture and cell proliferation (MTT) assays were performed on this stainless steel and assessed in respect of the 316L SS. Both the steels exhibited similar cell growth behavior. Furthermore, an enhancement was observed in cell proliferation on the Fe–18Cr–22Mn–0.65N SS after surface modification by ultrasonic shot peening (USP). The mean percent proliferation of the MG-63 cells increased from ≈88% for Un-USP to 98% and 105% for USP 3–2 and USP 2–2 samples, respectively for 5 d of incubation. Interestingly, in vivo animal study performed in rabbits for 3 and 6 weeks showed callus formation and sign of union without any allergic reaction.

Effect of process parameters on machinability, hemocompatibility and surface integrity of SS 316L using R-MRAFF

Surface finish at nanometric scale is imperative for biomedical implants made up of stainless steel 316L (SS 316L) and titanium alloy to ensure the biocompatibility. However, such fine finishing is quite difficult to process. A rotational magnetorheological abrasive flow finishing process is used for nano-finishing. Rotational magnetorheological abrasive flow finishing (R-MRAFF) is one of the processes to achieve nano-level finishing. In this present study, a rotating die has been developed to perform the R-MRAFF processes with four rectangular-shaped permanent magnets held at an angle of 90° to one another. A new method for producing a variable magnetic field was investigated in this study by increasing or decreasing the distance between permanent magnets in the rotating die and workpiece fixtures. The increase in the distance between permanent magnets in rotating die and workpiece fixture leads to a decline in the value of material removal rate (MRR) as well as a percentage reduction in surface roughness (%ΔRa). This validates the importance of magnetic field intensity in the R-MRAFF process. A central composite design (CCD) in the response surface methodology (RSM) is employed to study the effect of process parameters on the response variables. The effect of the process parameter was evidenced with the help of the ANOVA technique. Optimization was carried out with constraints of maximizing both output response variables, the optimum MRR and %ΔRa, which were found as 2.02 mg/s and 50.66%. To quantify the effect of surface roughness on hemocompatibility, a platelet adhesion study was investigated. The platelet adhered area starts to decrease with the reduction in the surface roughness from 319 to 167 nm.

Acoustic Emission during Press-Brake Bending of SS 304L Sheets and its Correlation with Residual Stress Distribution after Bending

Acoustic Emission during Press-Brake Bending of SS 304L Sheets and its Correlation with Residual Stress Distribution after Bending

Nondiffractive beam shaping for enhanced optothermal control in metal additive manufacturing.

High thermal gradients and complex melt pool instabilities involved in powder bed fusion–based metal additive manufacturing using focused Gaussian-shaped beams often lead to high porosity, poor morphological quality, and degraded mechanical performance. We show here that Bessel beams offer unprecedented control over the spatiotemporal evolution of the melt pool in stainless steel (SS 316L) in comparison to Gaussian beams. Notably, the nondiffractive nature of Bessel beams enables greater tolerance for focal plane positioning during 3D printing. We also demonstrate that Bessel beams significantly reduce the propensity for keyhole formation across a broad scan parameter space. High-speed imaging of the melt pool evolution and solidification dynamics reveals a unique mechanism where Bessel beams stabilize the melt pool turbulence and increase the time for melt pool solidification, owing to reduced thermal gradients. Consequently, we observe a distinctively improved combination of high density, reduced surface roughness, and robust tensile properties in 3D-printed test structures.

The evolution of oxygen-rich nanoparticle and its effect on the mechanical property in selective laser melted 304L stainless steel

The evolution of oxygen-rich nanoparticles in selective laser melted 304L stainless steel (SLM 304L SS) and its effect on the mechanical property were studied by adjusting the heat treatment process. The nanoparticles mainly contained oxygen, chromium, and silicon; the average size of oxygen-rich nanoparticles increased with the temperature of heat treatment. The nanoparticles were Cr-rich phases when treated below 950 °C, while the nanoparticles were Si-rich oxides when treated at 1100 °C. With the increase in the temperature of heat treatment, the molten pool boundaries and cellular structures of SLM 304L SS gradually disappeared and the yield strength decreased obviously. The boundary of the cellular structure with high dislocation density provides a fast channel for atom diffusion, and thus it becomes the preferred nucleation site for nanoparticles. The dispersed nanoparticles are not only the strengthening phases but also can hinder the movement of dislocations, and thus they can greatly improve the strength of the material without sacrificing ductility.

Thermo-elastic creep analysis and life assessment of rotating thick pressurized cylindrical shells using third-order shear deformation theory

In the present study, time-dependent thermo-elastic creep behavior and life assessment of rotating thick-walled cylindrical shells made of 304L austenitic stainless steel (304L SS) are investigated based on the third-order shear deformation theory (TSDT). Loading is composed of a uniform internal pressure, distributed temperature field, and a centrifugal body force due to rotating speed. Norton’s law is utilized as the material creep constitutive model. Using the minimum total potential energy principle, a system of differential equations in terms of displacement and boundary conditions are derived. Then, the governing equations are solved with an analytical approach, which leads to an accurate solution. Subsequently, an iterative procedure is also proposed to determine the stresses and deformations at different creep times. Larson-Miller Parameter (LMP) and Robinson's linear life fraction damage rule are employed for assessing the creep damages and the remaining life of cylindrical shells. To the best of the researcher’s knowledge, in the previous studies, there is no study carried out into third-order shear deformation theory for thermo-elastic creep analysis of cylinders. To validate the accuracy of the suggested method based on TSDT, a comparison among analytical results and those of the finite element method (FEM) is performed and very good agreement is found. The results indicate that the present analysis is accurate and computationally efficient.

The influence of cathode material, current density and pH on the rapid Cr(III) removal from concentrated tanning effluents via electro-precipitation

The Cr(III) removal (3585 mg L−1) from real tanning discharges is herein conducted using an electro-precipitation process in a rotating cylinder electrode (RCE) reactor. A 1018-type carbon steel anode and two different cathodes (TiO2/RuO2 or 316L stainless steel, 316L SS) are tested within this process, using three current densities (10, 20 and 30 mA cm−2), and two initial pH values for the real solution. A synthetic solution is initially evaluated to analyze more ideal conditions in the reactor. The Cr(III) electroprecipitation is not favorable in the original pH of the real tannery wastewater (∼3.55) unlike the synthetic solution (pH 2.8), presumably since the Fe-Cr interaction is hindered by impurities in the solution, whereby the pH of the real discharge needs to be modified to pH 5 or 6. Residence times of 4800 (80 min) and 3600 s (60 min) using 30 mA cm−2 are enough to remove all the Cr concentration at pH 5 and 6, respectively. Energy consumptions of 10 and 7.5 kWh m−3 are calculated for these treatments, respectively. The precipitates are mainly comprised of Cr2FeO4(s) (Chromite) regardless of the experimental condition used in the removal process, followed by minor traces of Cr(OH)3(s) and CrO(OH)(s). A reaction mechanism is proposed for the Cr(III) electro-precipitation relying on the thermodynamic diagrams, and characterizations of the precipitates.

Evaluation of residual stresses in isothermal friction stir welded 304L stainless steel plates

Friction stir welding was performed on 304L SS plates in order to heal simulated cracks created by electrical discharge machining. Two different tool temperatures (825 and 725 °C) were chosen for this study. Both neutron diffraction and X-ray diffraction techniques were employed to evaluate the residual stresses along two orthogonal reference directions, longitudinal (σyy) and transverse (σxx). The former technique was also used to measure residual stresses at various depths. It was found that, at 1 mm depth from the top surface inside the stir zone (SZ), the longitudinal component was tensile in nature while the transverse component was compressive. The nature and magnitude of the residual stress fields, and the position of the peak residual stresses were found to vary with the weld depth. The SZ of the 725 °C weld exhibited higher peak stress than 825 °C weld mainly due to a lack of stress relief at the lower temperature.

Electro-analysis of freshwater biofilm on stainless steel surface at different temperatures

The electrochemical response of stainless steel surface in the presence of natural freshwater biofilm was investigated at various temperatures such as 30 °C, 40 °C, and 50 °C. The adhesion of biofilm on 316L SS was also observed by means of potential shift (E) of 316L SS. Cyclic voltammogram, impedance spectroscopy and polarization studies were used to evaluate the electrochemical behavior of 316L SS in the presence of biofilm. The present study will be useful to develop biosensors for industrial applications.

Characterization of nano / micro bimodal 316L SS powder obtained by electrical explosion of wire for feedstock application in powder injection molding

Bimodal nano / micro powders are in demand in powder injection molding (PIM) and additive manufacturing (AM) technologies. Feedstocks with bimodal powder have a higher flowability, and the resulting products have a higher density.In this work, a bimodal 316L steel powder obtained by the electric explosion of a wire (EEW) was investigated. The bimodal powder is formed directly during the explosion and does not require a mixing step. The powder was obtained at different explosion energy densities. A feedstock was obtained with a powder content of 94 wt%.The powders have a different micro: nano ratio depending on the energy density. Feedstocks with these powders have different rheological behavior. The morphology and chemical composition of the powders and the homogeneity and rheological properties of feedstock with bimodal powder were studied and discussed. A comparison of feedstock properties with bimodal and micron powder is carried out.

Electrochemical deposition of HAP/f-MWCNTs and HAP/GO composite layers on 316L SS implant with excellent corrosion resistance performance

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.

Effect of the variation of the electrodeposition time of hydroxyapatite/chitosan coatings on AISI 316L SS

Type AISI 316 L Stainless Steel (316 L SS) plays a crucial role in bone replacement surgery due to its excellent mechanical features, availability at low cost, and ease of fabrication, but its performance is low when in contact with the aggressive conditions of the human body fluids. Chitosan (CTS) is a biopolymer that blended with hydroxyapatite (HAp) could form coatings to improve surface properties of a metallic orthopedic prosthesis, i.e., corrosion-resistance to the base metal and biocompatibility of the ceramic on the metal surface. This work aims to obtain and evaluate HAp/CTS composite coatings deposited on the surface of AISI 316 L SS substrate by electrophoretic deposition (EDP) technique. The influence of the time of deposition on the coating’s characteristics and properties was characterized and discussed. The coatings were structural, elemental, and chemically characterized using X-Ray diffraction and Raman spectroscopy. HV values in a range of 64.7 to 111.5 were observed, showing the lowest HAp/CTS-30.0 coating values for all the loads applied. The lowest HV value was nearby to the reported value for human bone’s hardness, around 47HV; considering that the coating will be in constant contact motion with the bone surface, the contact with a softer surface could decrease the wear on the human bone. The hardness decreases with the coating thickness’s increment because the coating presented a higher plastic deformation than the 316 L SS surfaces. A decrease in the roughness average (Ra) was well noticed as the deposition time increased; meanwhile, the thickness increased as the deposition time increased.

Development of fiber flow finishing (FFF) process for polishing hip prostheses

In this paper, a new polishing process has been developed based on a smart polishing media called fiber flow finishing (FFF). The proposed polishing media included styrene butadiene rubber (SBR), coarse sisal fibers, and naphthenic oil. During the process, the rheological behavior of the polishing media changes intelligently due to severe mechanical disintegration and chemical treatment. This intelligent behavior is very similar to the behavior of pseudo-plastic materials. To evaluate the polishing performance, experiments were performed on the femoral head of hip prostheses grade ASTM F138 (SS 316L) for the different number of finishing cycles to investigate its effect on the percentage change in surface roughness (%ΔR a ). The experimental results clearly showed that the %ΔR a of the femoral head is low in the initial finishing cycles (i.e., up to 200 working cycles), while the %ΔR a increases to 72.54% with an increase in the number of finishing cycles up to 1000. Moreover, the surface morphology of the specimens well substantiated that the FFF process performed a kind of surface modification on the surface texture of the femoral head, resulting in a smooth and uniform surface finish without surface defects that is as a mirror. • The fiber flow finishing (FFF) process is first developed for polishing hip prostheses. • The surface finish of the femoral head was improved by 72.54% using the FFF process. • The FFF process performed a kind of surface modification on the femoral head surface. • The FFF process has a better performance than the abrasive flow finishing (AFF) process. • The FFF process has a promising future to improve surface integrity of industrial parts.

Precision Electropolishing on Fabricating SS 316L Microchannel – A Taguchi Approach

This paper presents the fabrication of a microchannel on stainless steel 316L (SS 316L) by electropolishing method. Machining parameters such as applied voltage, concentration of NaCl in the electrolyte solution and machining gap between tool and workpiece have been optimized in this electropolishing process. The Taguchi method is adopted to ascertain the optimum process parameters in order to increase maximum material removal rate using L9 orthogonal array. Pareto analysis of variance is employed in order to analyze the machining process parameters to the material removal rate. The result shows that the optimal parameters to achieve the maximum material removal rate is by using a combination of 10 V as applied voltage, NaCl concentration of 15 wt.%, and setting 1 cm as the machining gap. It has been also found out that in order to have relatively high material removal without sacrificing the surface quality and the geometrical accuracy of the microchannel produced, applied voltage at 7 V, NaCl concentration of 7 wt.% and machining gap of 3 cm is the best combination of the electropolishing parameters.

Quantification of in-grain lattice gradient in neutron irradiated 304L SS during deformation using insitu EBSD

Quantification of in-grain lattice gradient in neutron irradiated 304L SS during deformation using insitu EBSD