316L Stainless Steel Research Articles

An analytical model for estimating process parameters input in L-DED based on bead geometry

Additive manufacturing of metal alloys via laser Directed Energy Deposition (L-DED) has been gaining popularity due to its potential to repair and create new features/components, enabling new applications for built parts. The success of L-DED operations hinges on the precise control of printing parameters, including laser power, scanning speed, and powder feed rate. These parameters significantly influence heat distribution during printing, directly impacting the quality of the resulting parts. Thus, defining an efficient methodology to find a good correlation between these parameters for the printing process is crucial to boost part production, as it reduces the time-consuming trial-and-error parameter tuning process. In this context, our study introduces an analytical model that predicts printing parameters based on the deposited material volume along track lines. Deposition was carried in stainless steel 316L with different values for laser power (ranging from 500 to 750W with 50W increments), scanning speed (from 400 to 700mm/min with 100mm/min increments), and powder feed rate (6.4,8.0 and 10.0g/min). The experimental data verified the effectiveness of the proposed model, demonstrating its potential to standardize the first step of printing process and expedite the initial search for optimal printing parameters in L-DED. The model provided accurate initial estimates of laser power, with a maximum relative error of 12%, particularly for the optimum mass flow rate (ṁ) of 8.0g/min. Beyond its benefits to the L-DED process, this analytical solution contributes to experimental practices by offering an efficient method for predicting material deposition volume during printing. Thus, our work underscores the significance of optimizing printing parameters to achieve high-quality parts and provides a valuable reference for future research and studies in the field of L-DED.

Evaluating the impacts of surface roughness and microstructure on the size effect in two additively manufactured stainless steels

Laser powder bed fusion (L-PBF) enables direct manufacturing of components with complex geometries and thin walls, but many authors report size-dependent mechanical properties that may complicate design. Size effects are commonly attributed to surface roughness, microstructure, and/or internal defects, but the relative importance of each is still not fully understood. To systematically study these effects, L-PBF specimens made of two microstructurally-distinct stainless steels (17-4PH and 316L) were manufactured and mechanically tested, in varied heat-treatment conditions and across a range of thicknesses and build angles. It was found that the size-dependent mechanical properties are efficiently predicted by the ratio of surface roughness to specimen thickness, Ra/t, in a way that is relatively microstructure-agnostic. This metric is particularly useful for predicting ultimate strength and elongation, while microstructure moderates its predictive power for yield strength, especially in the more processing-sensitive 17-4PH. When considered in isolation, thickness or surface roughness had weaker correlations with mechanical properties and, importantly, tended to correlate much more strongly with one steel's properties than the other's. Comparing this comprehensive dataset with summary data from other researchers highlights the utility of Ra/t, and provides semi-quantitative estimates of the relative impacts of porosity, microstructure, and Ra/t on size-dependent properties.

Mass finishing of additively manufactured AISI 316L using pecan nutshells as sustainable abrasive media

Abrasive processes represent the main methods for obtaining high-quality surface finish in metal parts. As one main characteristic, these processes have a relatively high consumption of energy per material volume removed, as well as many inputs, such as abrasive tools and equipment, and, consequently, a high associated environmental impact. Additive manufacturing is becoming a competitive method to produce customized parts, but the surface finish is often not good enough for the application, and post-processing is needed. In this work, a mass finishing process using a planetary mill with abrasive media made of sustainable materials (pecan nutshells) was used on AISI 316L stainless steel samples manufactured by selective laser melting (SLM). The main goal was to perform a multicriteria analysis of the sample surface before and after post-processing. Through the analysis, it could be observed that the nutshell abrasive media has results close to those of traditional ceramic media. The increase in the rotation speed of the planetary mill, increase of finishing time, and use of abrasive pastes can further increase the effectiveness of the process.

Dynamic compressive behavior of functionally graded triply periodic minimal surface meta-structures

Triply periodic minimal surface (TPMS) lattice structures have gained considerable attention because of their light weight, high strength, and excellent energy absorption capabilities. However, the effect of the amplitude that can control the topological morphology of a TPMS on the dynamic properties of the TPMS structure is not yet fully understood, as previous studies have focused on the relative density and size as well as their quasi-static mechanical properties. In this study, three types of uniform sheet-based TPMS structures with different amplitudes and three types of functionally graded sheet-based TPMS structures were proposed. Experiments and numerical simulations were conducted under quasi-static and dynamic loading conditions. Six types of TPMS lattice structures made of 316L stainless steel were manufactured via powder bed fusion. Quasi-static compression tests were performed at a strain rate of 0.001 s⁻¹. The experimental results indicate that increasing the amplitude can increase the elastic modulus, plateau stress, and energy absorption capacity of a structure. Moreover, the functional gradient amplitude structure has a higher energy absorption capacity, and the structures with line and log gradient strategies improved by 17.38% and 35.43%, respectively, compared to the uniform structure with an amplitude of 1. Additionally, an idealized rigid-linear plastic hardening (R-LPH) model was proposed to predict the mechanical response of the structures. The finite element method (FEM) was used to construct dynamic compression numerical models, and their validity was verified through split Hopkinson pressure bar (SHPB) tests at a strain rate of 695 s⁻¹. The mechanical response, deformation modes, and stress enhancement effects of the structures under dynamic compression were systematically studied. The results show that the mechanical performance and energy absorption capacity of the structures under dynamic impact loading increase with increasing strain rate. The critical velocity for the transition from the quasi-static mode to the impact mode increases with amplitude. For strain rates below 6000 s⁻¹, the strain rate effect is the main factor influencing the dynamic stress enhancement. As the strain rate continues to increase, the dynamic stress enhancement results from the combined effects of inertia and strain rate, with inertia effects gradually becoming the dominant factor. This study shows that functional gradient TPMS meta-structures have excellent mechanical and energy absorbing properties under quasi-static compression and dynamic compression, with potential applications in passive safety protection.

A Study on the Fretting Corrosion of 316L in Static Lead-Bismuth Eutectic (LBE): the Role of Slip Amplitude and Normal Force on Damage Mechanism at 350 °C

Fretting corrosion of stainless steel in the LBE affects the safety of lead-cooled fast reactors. Slip amplitude and normal load are the main mechanical factors affecting fretting wear behavior. Thus, the damage mechanism of 316L stainless steel at 350 °C LBE influenced by slip amplitude and normal load was investigated by jointly utilizing multiple characterization methods. The results indicate that the normal load and slip amplitude essentially affect the tangential stress and relative sliding value in the contact area, leading to different slip regions and damage mechanisms. In the mixed slip region, the damage mechanism is adhesion and delamination cracks. The increase in tangential stress leads to decrease in relative sliding. The thick wear debris layer attached to the worn surface can protect the substrate from being attacked by the LBE. In the gross slip region, the damage mechanism is abrasive wear and dissolution corrosion. The increase in relative sliding causes more damage and Ni dissolution, leading to the transformation from austenite to ferrite and internal strain, making the substrate more susceptible to damage and increasing the risk of liquid metal embrittlement (LME) of austenitic stainless steel at 350 °C. Accordingly, a model for different damage mechanisms was proposed. These results can provide important information on the fretting damage related to the LBE environment.

An experimental study on wire arc additive manufacturing (WAAM) of 308L stainless steel and its chemical dissolution

Wire arc additive manufacturing (WAAM) is a potential method of producing complicated metal parts directly from computer-aided design (CAD) models. In this experiment, stainless steel 308 L alloy was deposited with a GMAW-interfaced three-axis special purpose Cartesian robot. The major goal was to understand the behaviour of deposited material and, later, its dissolution in specific concentrations of chemical combinations. The deposited samples were investigated for better understanding of the impact of welding current on bead properties, surface roughness, and microstructure. Furthermore, the dissolving behaviour of deposited samples was investigated in various acidic bath mixes to better understand the rate of dissolution. The results reveal that WAAM parameters, particularly current, have a considerable impact on bead properties, roughness, and microstructure. On the other hand, dissolution experiments demonstrated that the faster breakdown of WAAM deposited stainless steel occurs when a 1:1 ratio mixture of acids is used.

Improved wear and corrosion resistance of additively manufactured SS316L by laser remelting process

Directed energy deposition is an efficient and flexible additive manufacturing technique that has broad application prospects due to its ability to fabricate intricate structures with heterogeneous properties. In this study, the laser-based directed energy deposition (L-DED) technique is employed to deposit an austenitic stainless steel 316L powder at a significantly high deposition rate. In recent developments, laser remelting (LR) has been explored as a superior alternative for enhancing the surface integrity of the components produced by L-DED. This study endeavours to examine the impacts of LR, emphasizing the improvement of wear and corrosion resistance. The grain refinement is achieved through laser remelting, which eventually leads to a 34 % improvement in micro–hardness over the as-deposited sample; as a result of increased micro–hardness, wear resistance improved by 66 % when compared to the as-deposited specimen. Furthermore, the corrosion resistance performance of the laser-remelted samples is compared with as-deposited samples by electrochemical impedance spectroscopy (EIS) in a solution of 3.5 % NaCl solution. The remelted sample showed improved corrosion resistance, which is attributed to the grain refinement due to rapid solidification in LR. This study demonstrates that laser remelting can be an effective way to improve the wear and corrosion resistance of SS316L, which enlarges its application in harsh environments.

Aqueous Electrophoretic Deposition of Yttrium-Doped Nanobioactive Glass/Collagen/Chitosan Orthopedic Coatings on 316L SS

The current study used yttrium-doped nano bioactive glass (Y-nBG, based on 62 SiO2 – (33 – x) CaO – 5 P2O5 – x Y2O3 mole %), collagen and chitosan composites for coating stainless steel 316L by an electrophoretic deposition (ED) method. x = 0, 1 and 3 moles % and the corresponding samples encoded as SS/Col-Chit, SS/BG-Y0/Col-Chit and SS/BG-Y3/Col-Chit, respectively. TGA, FTIR, SEM-EDX, contact angle, adhesion strength and in vitro bioactivity in SBF. Following SBF immersion, FTIR and SEM-EDX investigations were carried out. Furthermore, the coatings were loaded with gentamicin drug, the drug-releasing profile and mechanism of release were evaluated. Coatings' antibacterial efficacy was also assessed. The results showed formation of homogeneous coatings with good adhesion strengths, 1.39 MPa, 0.55 MPa and 0.81 MPa and enhanced the wettability by decreasing the contact angle 36.4, 21.8 and 11.7for SS/BG-Y0/Col-Chit and SS/BG-Y3/Col-Chit coatings, respectively. Also, in vitro bioactivity of coatings containing nBG was demonstrated by promoted apatite formation after immersion in SBF through the presence of calcium and phosphorus in SEM-EDX analysis. Furthermore, the antibiotic gentamicin was showed sustained release profile over time by diffusion mechanisms based on the Higuchi, Fickian and Weibull models. As well, all coatings containing drugs have an antibacterial effect. Overall, these findings suggest that the prepared coatings have potential for orthopedic applications.

Tribological Behavior of 316L Stainless Steel Fabricated Using Metal Extrusion Additive Manufacturing Under Dry and Simulated Body Fluid‐Lubricated Conditions

Herein, the tribological behavior of 316L stainless steel (SS) fabricated using metal extrusion additive manufacturing (MEAM) is investigated both under dry and simulated body fluid (SBF)‐lubricated conditions. The results and mechanisms are compared with those of 316L SS fabricated via selective laser melting (SLM) and hot rolling (HR). Under dry‐friction conditions, the 316L SS fabricated via MEAM shows inferior tribological performance compared with those fabricated via SLM and HR, primarily because of its lower initial hardness and better plasticity, which increase both abrasive and adhesive wear. Under SBF‐lubricated conditions, the tribological performance of the 316L SS fabricated via MEAM is comparable to that fabricated via HR and superior to that fabricated via SLM. The wear rate of the MEAM‐fabricated 316L SS is 16.8% and 3.2% lower than SLM‐ and HR‐fabricated, respectively. The numerous pores on 316L SS serve as traps for wear particles, which contribute to the reduction of three‐body wear. In terms of wear under SBF‐lubricated conditions, MEAM technology appears to be a promising method for the fabrication of customized 316L orthopedic implants.

Do Wettability Measurements Define Corrosion Inhibition of Etched Surfaces? A Study on Acid‐Etched 316L Stainless Steel

Special wetting surfaces have attracted attention owing to their potential applications in the automotive, engineering, environmental, and biomedical industries. Specifically, nature‐inspired superhydrophobic surfaces are more effective in blocking moisture, thus limiting corrosion. Hence, surface wettability analysis remains the primary method for demonstrating the corrosion mitigation characteristics of rough‐engineered surfaces. Herein, the influence of wettability measurements on the corrosion inhibition of 316L stainless steel surfaces etched in HCl: HNO3 acid is systematically investigated. Interestingly, etched hydrophobic surfaces with a contact angle of ≈125° significantly improve the corrosion resistance by 50%, resulting in suppressed corrosion rates. Furthermore, the surface chemical states of the etched 316L steel are analyzed and discussed in detail.

Effect of Scanning Speed on Microstructure Profile of Selective Laser Melted Stainless Steel 316L

Effect of Scanning Speed on Microstructure Profile of Selective Laser Melted Stainless Steel 316L

Comparative Analysis of Mechanical Properties: Conventional vs. Additive Manufacturing for Stainless Steel 316L

This research investigates the tensile strength and microstructural properties of stainless steel 316L, comparing samples fabricated using additive manufacturing (AM) to those produced via conventional manufacturing techniques such as forging and casting using stainless steel 316L for its mechanical performance and corrosion resistance. Tensile tests revealed that AM samples had an ultimate tensile strength (UTS) of 650 MPa, a yield strength of 550 MPa and an elongation at break of 20%, and conventionally manufactured samples achieved a UTS of 580 MPa, a yield strength of 450 MPa and a higher elongation at break of 35%. The reduced ductility of AM samples is offset by their higher strength. Scanning electron microscopy (SEM) analysis showed that AM samples had a refined grain structure, with grain sizes ranging from 1 to 5 µm, whereas conventionally produced samples exhibited larger grain sizes of 10 to 20 µm, contributing to their increased ductility. This shows that while AM processes can give a rather high strength, the ductility property is simpler to attain with casting. Further work is needed to investigate post-processing techniques like hot isotropic pressing (HIP) and heat treatments for enhancing the ductility of AM parts as well as mechanical properties.

(Invited) Development of Novel Coatings on Stainless Steel based Bipolar Plates for Proton Exchange Membrane (PEM) Water Electrolyzer Application

The stainless steel (SS) is an appropriate material for bipolar plate of PEM water electrolyzer owing to its high electron transport, superior mechanical characteristics, and formability, but it needs a coating to increase corrosion resistance. Herein, the multilayer coating of Au/Cr/Au on the SS was developed by electroplating method and corrosion studied were performed for bipolar plate application of PEM water electrolyzer. The gold striking underlayer on the SS substrate passivated the surface oxides and facilitated a dense electroplated chromium layer. Furthermore, a uniform gold protective layer was electroplated on the chromium coated substrate to achieve a promising anti-corrosive property. The Au/Cr/Au 316L SS substrate presented approximately ten times lower corrosion current density, and positive shift of corrosion potential as compared to uncoated SS substrate. The Au/Cr/Au/ 316 L SS was analysed for long time, and it depicted slower corrosion as compared to without striking underlayer of gold (Au/Cr/ 316L SS).

Determining the microstructure effects on the stress corrosion cracking initiation behavior of laser powder-bed-fusion printed 304L stainless steel in high-temperature hydrogenated water

This study investigated the microstructure effects on the stress corrosion cracking (SCC) initiation behavior of laser powder-bed-fusion (L-PBF) printed 304 L stainless steel in high-temperature hydrogenated water. The dislocation cells facilitate Cr transportation, thereby mitigating intergranular oxidation and SCC initiation. Compared to the warm-rolled dislocation cells, as-printed dislocation cells result in reduced strain localization, which is beneficial for suppressing SCC initiation. This is because the as-printed dislocation cells are stable and composed of abundant screw dislocations. Micro-inclusions can lead to nodular corrosion, thus increasing the depth of intergranular oxidation and promoting SCC initiation.

Passive film properties and corrosion resistance of AISI 304L stainless steel

Passive film properties and corrosion resistance of AISI 304L stainless steel

Corrosion behavior of 316L stainless steel reinforced by dispersed yttria stabilized zirconia fabricated by spark plasma sintering

This paper evaluates the corrosion behavior of 316L stainless steel (SS316L) matrix composites reinforced with 3% yttria-doped zirconia (3Y·ZrO2), fabricated using the spark plasma sintering. Four different compositions were produced (SS316L, SS316L-5%vol. 3Y.ZrO2, SS316L-10% vol. 3Y.ZrO2, and SS316L-20% vol. 3Y.ZrO2) and primarily assessed for their corrosion resistance evaluated via immersion tests and electrochemical impedance spectroscopy (EIS). Additionally, densification, surface morphology, microstructure and mechanical properties were characterized as complementary. Densification was measured using the Archimedes method, while surface and microstructural characteristics were analyzed using optical and scanning electron microscopy. Mechanical properties were determined through microhardness testing. The results indicate that higher 3Y·ZrO2 content decreases densification and induces porosity, which contributes to localized corrosion. Despite the presence of porosity, microhardness improved with increasing 3Y·ZrO2 content. Additionally, immersion and EIS tests revealed that 5% of 3Y·ZrO2 enhances corrosion resistance. However, in composites with 10% and 20% 3Y·ZrO2, porosity compromises corrosion resistance by degrading passivation. Notably, composites with 5% 3Y·ZrO2 demonstrated significantly better corrosion resistance compared to pure SS316L and the other compositions, highlighting their potential for practical applications.

Investigation of Fabricating Stainless Steel 304L Thin-Wall Structure Using Laser Marking-Assisted Wire Arc Additive Manufacturing Process

Investigation of Fabricating Stainless Steel 304L Thin-Wall Structure Using Laser Marking-Assisted Wire Arc Additive Manufacturing Process

Design and Assessment of an Austenitic Stainless Alloy for Laser Powder Bed Additive Manufacturing

Recent developments in metallic additive manufacturing (AM) processes for the production of high-performance industrial pieces have been hampered by the limited availability of reliably processable or printable alloys. To date, most of the alloys used in AM are commercial grades that have been previously optimized for different manufacturing techniques. This study aims to design new alloys specifically tailored for AM processes, to minimize defects in the final products and to optimize their properties. A computational approach is proposed to design novel and optimized austenitic alloy compositions. This method integrates a suite of predictive tools, including machine learning, calculation of phase diagrams (CALPHAD) and physical models, all piloted by a multi-objective genetic algorithm. Within this framework, several material-dependent criteria are examined and their impact on properties and on the occurrence of defects is identified. To validate our approach, experimental tests are performed on a selected alloy composition: powder is produced by gas atomization and samples are fabricated by laser powder bed fusion. The microstructure and mechanical properties of the alloys are evaluated and its printability is compared with a commercial 316L stainless steel taken as a reference. The optimized alloy performs similarly to 316L in terms of coefficient of thermal expansion, hardness and elongation, but has a 17% lower yield strength and ultimate tensile strength (UTS), indicating that further optimization is required.

Anisotropic sintering behavior of stainless steel 316L printed by binder jetting additive manufacturing

The influence of sintering temperature and printing orientation on the anisotropic sintering shrinkage of binder jetted (BJ) stainless steel 316L (SS316L) was investigated. Near quasi-isotropic shrinkage behavior with very little anisotropy (≤4 %) in the powder bed plane was observed. The out-of-plane anisotropic shrinkage of up to 16 % was attributed to the primitive lines formed perpendicular to the build direction. This follows the power law, and the activation energy is not affected by the anisotropy. For all printing orientations, grain boundary diffusion (25–162 kJ/mol) was the dominant sintering mechanism between 1100 °C and 1300 °C. Above 1300 °C, volume diffusion (490–623 kJ/mol) takes over as the dominating sintering mechanism, leading to significantly higher shrinkage up to 15 %. The anisotropic shrinkage behavior does not affect the microstructure, as similar evolution of grain sizes, ferrite fractions, and bulk densities (up to 96 %) is observed upon sintering.

Optimizing Surface Hardness and Corrosion Resistance in 316L Stainless Steel via SMRT and Plasma Nitriding.

Increasing the mechanical strength of stainless steel is fundamental to expanding its applications and extending its useful life, especially due to its impressive corrosion resistance. However, many processes that make possible increasing the hardness and wear resistance of these steels also compromise their performance when they are subjected to corrosive environments. Because of the need to increase surface hardness without jeopardizing corrosion resistance, this study explores the impact of a surface mechanical rolling treatment (SMRT) with volumetric reductions of 50% and 70%, together with high-temperature plasma nitriding (PN) (450, 500, and 550 °C), on 316L steel. X-ray diffraction analysis analyzed the composition and structure of the resulting coatings. Mechanical strength was assessed using Vickers microhardness, while corrosion resistance was tested in a 3.5%-by-weight NaCl solution. The results indicate a substantial increase in surface hardness in all of the nitrided samples. Notably, the samples were subjected to rolling with 50% and 70% volumetric reduction, and subsequent nitriding at 550 °C showed a reduced impairment of corrosion resistance. This shows that the methodology adopted in this study, consisting of SMRT and PN, can increase the useful life and expand the applicability of stainless steels commonly used in various industry sectors.