316L SS Research Articles

Influence of AWJ Process Parameters on Erosion Groove Formation in Additively Manufactured Stainless Steel.

The presented manuscript focuses on the influence of process parameters of abrasive water jet technology on the creation of non-transient erosive grooves. The processed stainless steel SS 316L is additively manufactured using the selective laser melting (SLM) method. Due to the distinct mechanical properties of this material resulting from the production process, the material was machined in two planes according to the direction of the printing layers. The experimental part employed a planned experiment utilizing the DoE (Design of Experiment) method. Experiments aimed at varying process parameters (traverse speed, standoff distance, abrasive mass flow) were conducted at a water pressure of 50 MPa, assessing the parameters' impact on the removed material and the properties of the resulting non-transient erosion groove. The properties of the erosion groove, such as shape and the material removal (area of erosion groove), were evaluated. The influences of process parameters on the observed parameters were assessed using the analysis of variance (ANOVA) method. Experiment preparation and setup were based on a thorough theoretical analysis of the machining process with the abrasive water jet (AWJ) method. The experiment also highlights the diverse properties of the SS 316L material prepared using the SLM method when machined with AWJ technology.

Using Bio-inline Reactor to Evaluate Sanitizer Efficacy in Removing Dual-species Biofilms Formed by Escherichia coli O157:H7 and Listeria monocytogenes

The efficacy of a sanitizer in biofilm removal may be influenced by a combination of factors such as sanitizer exposure time and concentration, bacterial species, surface topography, and shear stresses. We employed an inline biofilm reactor to investigate the interactions of these variables on biofilm removal with chlorine. The CDC bioreactor was used to grow E. coli O157:H7 and L. monocytogenes biofilms as a single species or with Ralstonia insidiosa as a dual-species biofilm on stainless steel, PTFE, and EPDM coupons at shear stresses 0.368 and 2.462 N/m2 for 48 hours. Coupons were retrieved from a CDC bioreactor and placed in an inline biofilm reactor and 100, 200, or 500 ppm of chlorine was supplied for 1- and 4 min. Bacterial populations in the biofilms were quantified pre- and posttreatment by plating on selective media. After chlorine treatment, reduction (Log CFU/cm2) in pathogen populations obtained from three replicates was analyzed for statistical significance. A 1-min chlorine treatment (500 ppm), on dual-species E. coli O157:H7 biofilms grown at high shear stress of 2.462 N/m2 resulted in significant E. coli O157:H7 reductions on SS 316L (2.79 log CFU/cm2) and PTFE (1.76 log CFU/cm2). Similar trend was also observed for biofilm removal after a 4-min chlorine treatment. Single species E. coli O157:H7 biofilms exhibited higher resistance to chlorine when biofilms were developed at high shear stress. The effect of chlorine in L. monocytogenes removal from dual-species biofilms was dependent primarily on the shear stress at which they were formed rather than the surface topography of materials. Besides surface topography, shear stresses at which biofilms were formed also influenced the effect of sanitizer. The removal of E. coli O157:H7 biofilms from EPDM material may require critical interventions due to difficulty in removing this pathogen. The inline biofilm reactor is a novel tool to evaluate the efficacy of a sanitizer in bacterial biofilm removal.

Novel Cardiovascular Stent Based on Hibiscus-Aestivation-Inspired Auxetic Unit Cell

Conventional stents have some limitations, such as dogboning and foreshortening, that can lead to issues like in-stent restenosis and thrombosis. Negative Poisson's ratio stents, called auxetic stents, are known as a solution to overcome these challenges due to their unique deformation mechanism. Auxetic stents are scale-independent, and their behavior depends solely on their geometry. In this study, a novel auxetic unit cell inspired by aestivation mechanism of the Hibiscus flower is designed, developed, and implemented in plane, and a tube to achieve a novel NPR cardiovascular stent. The stent structure is fabricated using two methods, including a novel 7-axis laser cut method capable of producing stents the same size as human blood vessels from an SS 316 L tube, and fused deposition modelling 3D printing at a scale 20 times larger than the metallic sample using PLA filaments. Novel laser cut effectively overcame some challenges in laser cutting stents, including HAZ and thermal shocks. SEM images are taken from the laser cut sample, and the manufacturing method's accuracy and surface quality are investigated. Fabricated metallic and polymeric stent samples proposed negative Poisson's ratio equal to 0.89 with an average of 4.38 and 14.8% errors, respectively, compared with finite element analysis. Finally, the structure's stress, strain energy distribution pattern, and unit cell distribution have been examined. Furthermore, the stent thickness parameter, drug release patch application, and stent implementation process are also investigated using FEM method. Proposed geometry in stent application showed solutions to conventional positive Poisson's ratio stent challenges.

Artificial Neural Networks Based Prediction of Penetration in Activated Tungsten Inert Gas Welding

Using GTAW, or tungsten inert gas (TIG) welding, weld penetration is usually lesser than the other arc welding processes. ATIG (Activated-flux TIG) welding can be a good alternative to provide deep penetration, and hence, improved productivity. In this work, 304L SS plate of 8 mm thickness was used as base plate, and a flux with a mixture of SiO2, MnO2 and MoO3 was used as a ternary flux in the ratio of 1:1:2. A 2-factor 3-level response surface methodology of central composite design was considered for designing experimental runs. Back Propagation (BP) type Artificial Neural Networks (ANN) model was developed to assess penetration in ATIG welding by using heat input and pulse frequency as the two process parameters. The ANN chosen has 2-10-1 network structure. Results show that the predicted values through ANN are conforming quite well to the experimentally obtained penetration, and hence, the applicability of ANN.

Wear performance of Ti-based alloy coatings on 316L SS fabricated with the sputtering method: Relevance to biomedical implants.

This investigation was conducted to encapsulate 316L SS with a Ti-based alloy coating. The aim was to fabricate a coating using TiN, TiO2, and TiCoCr powders on 316L SS through the physical vapor deposition (PVD) sputtering process. The powders were consecutively coated on 316L SS through the PVD sputtering process with coating durations of 30, 60, and 90 min. Further microhardness, surface roughness, microabrasion, and adhesion strength tests were also carried out. A 60% improvement in abrasion resistance was observed in TiCoCr-coated samples compared to the uncoated substrate. The X-ray diffraction results confirmed the optimal formation of Ti alloy coatings with corresponding orientation over the SS substrates. Moreover, TiCoCr with a 90 min coating duration had much better surface characteristics than TiO2 and TiN. The 90 min coating duration should be optimal for coating in steel for bio-implants.

Residual Stress Evaluation in L-PBF-Produced SS 316L Specimens.

The identification of residual stresses (RS) in components made by selective laser melting (SLM) is necessary for subsequent technological optimization. The presented research is devoted to evaluating the influence of the combination of laser power (P), scanning velocity (v) and the rarely considered number of layers (nL) on surface residual stresses in SLM stainless steel SS 316L. Experimental parameters were set based on the Design of Experiment (DoE) method, with follow-up X-ray diffraction (XRD) measurements and data processing using analysis of variance (ANOVA) and regression analysis. The obtained data are a valuable stepping-stone for the subsequent design of research focused on the application of sustainable eco-friendly Abrasive Water Jet (AWJ) peening for RS modification in the evaluated material.

Tribological behavior and biocompatibility of novel Nickel-Free stainless steel manufactured via laser powder bed fusion for biomedical applications

Due to the risk of releasing carcinogenic nickel ions from conventional 316L stainless steel under a corrosive human body environment, a new variant of steel termed nickel-free stainless steel (NiFSS) has been investigated. The present study investigates the tribological properties and biocompatibility of NiFSS manufactured via laser powder bed fusion (PBF-LB/M). The ferritic NiFSS exhibited significantly lower coefficient of friction (0.08 to 0.28) and wear rate (1.60 × 10-6 mm3/Nm to 6.60 × 10-6 mm3/Nm) compared to reported values for austenitic 316L SS, under both dry and simulated body fluid (SBF) conditions and various sliding geometries. This improvement is attributed to the superior hardness (3.394 ± 0.1340 GPa) and elastic modulus (238 ± 9.0797 GPa) of NiFSS. To assess the biocompatibility, the viability of mouse pre-osteoblastic MC3T3-E1 cells was evaluated with an Alamar Blue assay when the cells were cultured on top of PBF-LB/M built NiFSS and 316L SS samples. The results indicated that even though cell growth was most optimal on regular cell culture plastic, cell viability was better maintained on PBF-LB/M built NiFSS compared to 316L SS. Therefore, the results of the present study propose that PBF-LB/M fabricated NiFSS holds promise for application in biomedical devices for joint arthroplasty.

Corrosion of austenitic and ferritic steels, Kovar, and molybdenum in liquid Sb-Bi alloys with different compositions

Sb-Bi alloys may be applied as positive electrode in liquid metal batteries. In this work, the material compatibility of two steels (SS 316L and T91), Kovar 4J29, and molybdenum with SbBi9, Sb2Bi8, and Sb3Bi7 is investigated in static corrosion tests for 740 h at around 450 °C. Kovar shows severe dissolution attack (800 µm depth for SbBi9), which is mitigated at higher Sb contents due to the formation of Fe-Sb compounds. Both steels exhibit moderate corrosion depths (10–20 µm) for all Sb-Bi alloys thanks to the additional formation of stable Fe-Cr-Sb compounds. Good corrosion resistance is obtained for molybdenum.

Convective boiling heat transfer enhancement via femtosecond laser textured inclined microfeatures

Designing efficient cooling devices is crucial in a multitude of applications. Although cooling technologies have existed for decades, there is a lack of efficient heat dissipation methods, especially for space applications where thermal management devices must dissipate heat in reduced gravity and where convective boiling heat transfer is frequently employed. In this framework, we evaluate the change in bubble production for different types of surface textures produced on 200 µm thick 316L SS foils using a femtosecond laser. The investigated textures include microscale grooves and conical holes with tilted (= 45°) geometry. In addition, we also evaluate the effect of laser-induced periodic surface structures (LIPSS), which are sub-micron scale features fabricated by fs laser processing. The fluid used is PP1, a replacement of 3M™ FC-72 in heat transfer applications.

A comparison of clinical outcomes between narrow and broad dynamic compression plate for femur fractures

Purpose: To review the short term performance 4.5/5.0mm Wise-Lock Narrow Dynamic Compression Plate with LC under cuts and 4.5/5.0mm Wise-Lock Broad Dynamic Compression Plate with LC under cuts for femur fractures in terms of postoperative complications and failure rates. Methods: The total number of 46 patients, 24 to 55 years’ age group, who underwent internal fixation with wise-lock narrow and broad dynamic compression plate for femur fractures were reviewed. These implants were manufactured at Auxein Medical Private Limited Sonipat (India). The wise-lock narrow dynamic compression plates were implanted to 24 patients (18 Male and 05 Female) and broad dynamic compression plates were implanted to 22 patients (15 Male and 08 Female). These plates were made up of SS 316L and Ti6Al4V alloy respectively. Clinical and radiological follow-ups were conducted at the end of 30 days, 90 days, 180 days, 270 days and 365 days after surgery to examine the bone union, non-union & other related complications. During the one year of follow-up by the surgeon the patient's health status was analysed by the American society of anesthesiologists grade and the visual analogue score (VAS) was also determined. Results: Patients were followed up for one year. Out of 24 patients who were treated with wise-lock narrow dynamic compression plate, stainless steel, 04 patients (03 males & 01 female) were faced the complications of pain. However, out of 22 patients who were treated with broad dynamic compression plate, titanium, 02 patients (02 males) developed complications of pain. No biomechanical issue related to screw loosening, corrosion, bending, or other factors was not detected in 46 patients. Conclusions: Femur plate fixation is feasible for the treatment of femur fracture. The clinical outcomes and prognosis of patients are dependent on the accuracy of intraoperative reduction and surgical expertise.

Facile preparation of ZIF-67 on TiO2 and enhancement photocathodic protection for 316L stainless steel

Photocathodic protection (PCP) anticorrosion using sunlight is a green and sustainable technology. However, the ease of carriers compounding and the low light utilization are still the main restraints to its development. To develop an effective photoanode, a metal-organic framework (MOF, i.e., ZIF-67) material is electrodeposited and grown in-situ on TiO2 nanorods. The morphological structure, light absorption properties, photoelectrochemical properties and cathodic protection principle of ZIF-67/TiO2 photoanode are analysed by SEM, PL, I-V and EIS. The material characterization and light absorption characteristics show that the photoanode has good light absorption performance and higher electron hole separation efficiency. Photoelectrochemical test shows that ZIF-67/TiO2 photoanode has excellent photocathodic protection for 316L stainless steel (316L SS). ZTRs-60 has the optimal protection effect. Under simulated sunlight, the OCP of 316L SS coupled ZTRs-60 is -0.41 V vs. Ag/AgCl, and the current density of the I-t curve can reach 20 μA/cm2. EIS and Tafel tests show that the photogenerated electrons transfer to the stainless steel surface, which promotes the cathode polarization process and alleviates the metal corrosion.

An Investigation of the Anisotropic Mechanical Properties of Additive-Manufactured 316L SS with SLM.

Selective laser melting (SLM) forms specimens that often exhibit anisotropic mechanical properties. Most existing research only explains that the mechanical properties of specimens perpendicular to the build direction are superior to those parallel to the build direction. In this paper, the mechanical properties of SLM 316L SS specimens with different surfaces and different directions are compared. Finally, it was found that the mechanical properties of specimens on Face 3 are stronger than those on Face 1 and Face 2, while the mechanical properties of specimens on Face 1 and Face 2 are similar. For specimens in different directions on the same surface, the mechanical properties of Face 1 and Face 2 exhibit clear anisotropy, while the mechanical properties of Face 3 tend to be isotropic. In this paper, the EBSD technique was used to analyze the specimens. It was found that the anisotropy of the mechanical properties of Face 1 and Face 2 are attributed to the presence of texture and columnar crystals in the sample. This paper can provide accurate and reliable material performance data for the practical application of SLM 316L SS, thereby guiding the optimization of engineering design and manufacturing processes.

Nanostructuring of Additively Manufactured 316L Stainless Steel via High-Pressure Torsion for Enhanced Strength and Corrosion Performance

Bulk nanostructured materials (BNM) are defined as metallic materials with grain sizes <100 nm and are known to possess superior mechanical and functional properties compared to those with grain sizes in the micron and millimeter ranges. In this study, high-pressure torsion (HPT), a nanostructuring approach that imposes compressive stress and extreme torsional strain on bulk materials is applied to an additively manufactured (AM) 316L stainless steel (316L SS) for 10 revolutions. The grain sizes, hardness, and corrosion performance before and after HPT are evaluated by using extensive microscopy techniques, Vickers hardness (HV) measurements, and electrochemical tests conducted in 3.5 wt.% NaCl solution, respectively. The results show that after 10 HPT revolutions, nano-sized grains (average: ~42 nm) are obtained, whereas a three-fold increase in HV values from ~220 HV to ~600 HV are observed. Furthermore, the corrosion performance is also significantly enhanced as indicated by the reduction in corrosion ratefrom 2.53 μm/year initially, to 0.48 μm/year after HPT processing. These results highlight the benefits of HPT in producing bulk nanostructured materials with remarkably high hardness and excellent corrosion performance, potentially useful for a myriad of applications.

Radionuclide tracing based in situ corrosion and mass transport monitoring of 316L stainless steel in a molten salt closed loop

In the study, we report an in situ corrosion and mass transport monitoring method developed using a radionuclide tracing technique for the corrosion study of 316L stainless steel (316L SS) in a NaCl–MgCl2 eutectic molten salt natural circulation loop. This method involves cyclotron irradiation of a small tube section with 16 MeV protons, later welds at the hot leg of the molten salt flow loop, generating radionuclides 51Cr, 52Mn, and 56Co at the salt–alloy interface. By measuring the activity variations of these radionuclides at different sections along the loop, both the in situ monitoring of the corrosion attack depth of 316L SS and corrosion product transport and its precipitation in flowing NaCl–MgCl2 molten salt are achieved. While 316L SS is the focus of this study, the technique reported herein can be extended to other structural materials being used in a wide range of industrial applications.

FORMATION OF NANOCONES AND GENERATION OF NEGATIVE POTENTIAL ON STAINLESS STEEL SURFACES BY ELECTROCHEMICAL ETCHING SYNERGISTICALLY REDUCE PSEUDOMONAS AERUGINOSA'S BIOFILM

Hospital-acquired infections cause severe patient problems because of the augmented appearance of antibiotic-resistant bacteria, including Pseudomonas aeruginosa. Material surfaces modified with several biophysical parameters can decrease bacterial biofilm formation, which could be an advantageous alternative to treatment with antibiotics. Since stainless steel is an extensively used material for manufacturing medical implants and in healthcare settings, in this study, we used stainless steel (SS 316L and SS 304) to examine the result of the material surface topographies on bacterial biofilm establishment. This work used the electrochemical etching method to modify the stainless steel surface topography as an anode. The electrochemical etching method influenced the nanocones’ formation on stainless steel surfaces of both SS316L (Disk-6: 2682 peaks/[Formula: see text]m[Formula: see text] and SS304 (Disk-12: 1654 peaks/[Formula: see text]m[Formula: see text] estimated by atomic force microscopy and 3D Profilometer reduced the biofilm by 78% and 85%, respectively. Additionally, the higher negative potential on an average of 600[Formula: see text]mV measured by Kelvin probe atomic force microscopy reduced the biofilm formation on both SS316L and SS304 surface synergistically compared to the non-electrochemically etched surface. Biofilm growth and nanopotrusions on the stainless-steel surface examined by atomic force microscopy and scanning electron microscopy demonstrated significantly dead bacterial cells (20%) on the electrochemically etched surface than on the non-electrochemically etched surface after 2[Formula: see text]h contact time. Our observations exhibit that the nanotextured surface topographies and surface negative potential effectively inhibit bacterial adhesion and biofilm formation.

ASTM interlaboratory study on tensile testing of AM deposited and wrought steel using miniature specimens

An interlaboratory study, involving eigth international laboratories and coordinated by COMTES FHT (Czech Republic), was conducted to validate tensile measurements obtained using miniature specimens on additively manufactured (AM) components and artifacts. In addition to AM 316L stainless steel (316L SS), a wrought high-strength steel (34CrNiMo6V, equivalent to AISI 4340) was also used. Based on the results, a precision statement in accordance with ASTM E691 standard practice was developed, intended for inclusion in a proposed annex to the ASTM E8/E8M tension testing method. The primary outcomes of the study highlighted the agreement between yield and tensile strength measured from miniature and standard-sized tensile specimens. Furthermore, most tensile properties exhibited similar standard deviations, offering users insight into the efficacy of miniature specimen applications.

Evaluation of microstructure, corrosion resistance performance, and mechanical properties of 316L austenitic stainless steel FCAW welded joints: a comparative study

ABSTRACT This research aims to not only examine the effect of different mixtures of Ar and CO2 on microstructural features and corrosion behavior of double-pass FCAW of 316L SS but also compare these characteristics with gas tungsten arc welding (GTAW) and self-shielded FCAW. Different shielding gas mixtures, namely 100%Ar, 100%CO2, 82%Ar+18%CO2 were used to make the specimens. All specimens represent biphasic microstructures containing austenite (Ɣ) and delta-ferrite (δ-ferrite). Based on the potentiodynamic (PD) test results, the anti-corrosion protection performance of the welded region was enhanced when using GTAW compared to self-shielded FCAW. Additionally, the impedance value of the GTAW joint was higher than that of the FCAW-welded specimens. The ductility of welded joints was ranked as GTAW > CO2 +Ar shielded FCAW > self-shielded FCAW > CO2 shielded FCAW. The ranking of transverse tensile strength was as follows: CO2 shielded FCAW> self-shielded FCAW > CO2+ Ar shielded FCAW> GTAW.

Chloride Ion Effect on 316L SS Reinforcement in Fresh and Hardened Concrete: Electrochemical and Microscopic Analysis

Chloride Ion Effect on 316L SS Reinforcement in Fresh and Hardened Concrete: Electrochemical and Microscopic Analysis

Lattice Design and Advanced Modeling to Guide the Design of High-Performance Lightweight Structural Materials

Lightweight structural materials are required to increase the mobility of fission batteries. The materials must feature a robust combination of mechanical properties to demonstrate structural resilience. The primary objective of this project is to produce lightweight structural materials whose strength-to-weight ratios exceed those of the current widely used structural materials such as 316L stainless steels (316L SS). To achieve this, advanced modeling and simulation tools were employed to design lattice structures with different lattice parameters and different lattice types. A process was successfully developed for transforming lattice-structures models into Multiphysics Object Oriented Simulation Environment (MOOSE) inputs. Finite element modeling (FEM) was used to simulate the uniaxial tensile testing of the lattice-structured parts to investigate the stress distribution at a given displacement. The preliminary results showed that the lattice-structured sample displayed a lower Young’s modulus in comparison with the solid material and that the unit cell size of the lattice had a minimal effect. The novelty here is to apply up-front modeling to determine the best structure for the application before actually producing the sample. The approach of using modeling as a guiding tool for preliminary material design can significantly save time and cost for material development.

Effect of dissolved precursors on corrosion characteristics of Ni-based alloy Inconel 625, stainless steel 316L and titanium alloy TA2 in acidic and neutral supercritical water: A comparative study

This work investigated the corrosion characteristics of nickel-based alloy Inconel 625, stainless steel 316L (SS 316L), and commercial grade 2 titanium alloy (TA2) in ZrO(NO3)2-containing and ZrO(NO3)2/KOH-containing supercritical water (SCW) at 400 °C and 25 MPa. During ZrO(NO3)2-containing SCW exposure, Inconel 625 undergoes pitting and intergranular corrosion, while SS 316L and TA2 suffer uniform corrosion. Based on corrosion rate and metal oxide stability, the corrosion resistance follows an order of TA2 > Inconel 625 > SS 316L. The addition of KOH reduces the intergranular corrosion sensitivity of Inconel 625, and leads to different oxide distribution of SS 316L. The thick TiO2 oxide layer mixed with ZrO2 formed in ZrO(NO3)2/KOH-containing SCW enables TA2 to exhibit superior corrosion resistance than Inconel 625 and SS 316L.