316L Stainless Steel Research Articles

Circumventing cracking in grading 316L stainless steel to Monel400 through compositional modifications in directed energy deposition

In joining Fe-alloys and Cu-containing alloys to access the high strength of steels and corrosion resistance of Cu-alloy, cracking is widely observed due to the significant Cu microsegregation during the solidification process, resulting in an interdendritic Cu-rich liquid film at the end of solidification. By fabricating functionally graded materials (FGMs) that incorporate additional elements like Ni in the transition region between these terminal alloy classes, the hot cracking can be reduced. In the present work, the joining of stainless steel 316L (SS316L) and Monel400 by modifying the Ni concentration in the gradient region was studied. A new hot cracking criterion based on hybrid Scheil-equilibrium approach was developed and validated with monolithic multi-layer samples within the SS316L-Ni-Monel400 three-alloy system and a SS316L to 55/45 wt% SS316L/Ni to Monel400 FGM sample fabricated by direct energy deposition (DED). The new hot cracking criterion, based on the hybrid Scheil-equilibrium approach, is expected to help design FGM paths between other Fe-alloys and Cu-containing alloys as well.

Performance prediction of 304 L stainless steel based on machine learning

With the development of testing technology and data mining methodologies, machine learning (ML) has been widely applied for predicting the performance of materials in various systems including stainless steel with improved performance. To address the limitations of traditional experimental and statistical methods in predicting the thermal deformation of materials, a predictive machine learning model was developed based on the data obtained from thermal simulation compression tests. Specifically, the Arrhenius and the Modified Johnson-Cook (J-C) Constitutive Model were developed utilizing experimental data to initially predict the rheological behavior of 1.52% Cu-304L stainless steel. Then, a physical metallurgy (PM)-guided Back Propagation (BP) model was developed, and Genetic Algorithm (GA), Whale Optimization Algorithm (WOA), and Mind Evolutionary Algorithm (MEA) were incorporated into the model for optimization purposes, respectively. Finally, the results indicate that the PM-MEA-BP model exhibits superior predictive performance, accurately forecasting the texture evolution of 304L stainless steel with random crystal orientation under rolling deformation conditions. Additionally, the present work also clearly demonstrated that the model not only satisfies precision requirement but also has certain guiding significance for optimizing process parameters and forecasting the microstructure and properties of stainless steel.

Surface characteristics evolution of 316L stainless steel induced by tension loading

316L stainless steel has been employed as a medical implant material owing to its advantageous biocompatibility and durability. The microstructure and surface characteristics of 316L play a crucial role in implant application. Diverse processing methods were utilized to modify the surface properties of 316L to customize the characteristics of medical devices. Mechanical deformation induces changes in the microstructure and causes changes in surface topography. In this study, we introduced deformation to 316L by applying uniaxial tension at strain values ranging from 2% to 25%. During sample preparation, electrochemical polishing was employed to eliminate the deformed layers generated by mechanical grinding. After the tensile test, a contact angle test was conducted. The surface relief of 316L was examined using three-dimensional (3D) laser scanning microscopy and atomic force microscopy. X-ray diffraction with CuK radiation in the Bragg–Brentano (θ–θ) mode was also employed to identify the phase transformation. It can be concluded that higher strain levels increased surface roughness and the number of slip lines. At higher strain levels, samples exhibited a martensitic transformation, affecting topography changes and the surface free energy. The contact angle measurement results and surface free energy determination showed improved wettability following plastic deformation. Determining the factors that affect surface wettability requires an understanding of the relationship between surface free energy, topography, and surface roughness. Deformation-induced martensite can significantly increase the surface free energy and wettability of 316L stainless steel (SS) by altering strain levels. It is important to consider surface characteristics to understand slip mechanisms at grain boundaries, particularly in cases where surfaces have been electropolished. Nevertheless, the surface also manifested deformation-induced martensitic (DIM) transformation, potentially posing a risk to the passive film and contributing to corrosion, consequently reducing the implant’s lifespan.

Additive-Manufacturing-Induced Cell Structure in Stainless Steel 316L: 3D Morphology and Formation Mechanism

AbstractThe 3D morphology of the additive-manufacturing-induced cell structure is characterized and its formation in austenitic stainless steel 316L fabricated by laser powder bed fusion is analyzed. The experimental results demonstrate that the cell structure has a 3D prism-like morphology with a crystallography-dependent spatial orientation. The formation of the cell structure is discussed. It is proposed that both the liquid–solid transformation and thermal strain contribute to the formation: the initial cells form during the liquid–solid transformation, and the final dislocation cell structure is shaped by thermal-stress-induced deformation during cooling and subsequent thermal cycles.

Study on Heat Input Effect of 316L Stainless Steel Thin-Walled Parts Processed by Wire Arc Additive Manufacturing

Study on Heat Input Effect of 316L Stainless Steel Thin-Walled Parts Processed by Wire Arc Additive Manufacturing

Remelting-based microstructure engineering in laser powder bed fusion: A case study in 316L stainless steel

In laser powder bed fusion (LPBF), the formation of bulky columnar grains often results in undesirable mechanical anisotropy. Here, we demonstrate a new strategy to control the microstructure in LPBF through tuning melt pool overlaps without changing energy densities and scan patterns. Using 316L stainless steel as an example, we generate a wide range of grain sizes and morphologies. The underlying mechanism is associated with the retainment or elimination of newly nucleated grains at a melt pool during the formation of subsequent melt pools. The propensity of retainment or elimination of grains is largely dependent on the extent of melt pool overlaps because the grains are prone to nucleate at the free-surfaces of melt pool boundaries. This facile strategy could be applicable to a wide range of metallic alloys, paving a new way for microstructure engineering in additive manufacturing.

Electron Beam Welding of Dissimilar Stainless Steel and Maraging Steel Joints

The incorporation of additive manufactured (AM) metal parts to real assemblies is a crucial issue for the increasing of their industrial utilization. The presented research is devoted to the electron beam welding (EBW) of dissimilar steel joints. Dissimilarity is defined by the various types of steel and manufacturing processes used for the creation of specimens. Conventional AISI 316 stainless steel, selective laser melted (SLM) SS 316L stainless steel, and SLM M300 maraging steel were welded at variable parameters in the form of a welding current and a welding velocity. EBW joints were evaluated considering the macroscopic and microscopic characteristics, as well as a reached microhardness. The obtained preliminary results represent important input data for the follow-up experiments focused on the setting of optimal EBW parameters of welding the dissimilar joints including SLM products, with the consideration of their basic macroscopical and microscopical characteristics, mechanical properties, and residual stresses.

Effect of inclusion and microstructure transformation on corrosion resistance of 316L stainless steel after isothermal heat treatment

Effect of inclusion and microstructure transformation on corrosion resistance of 316L stainless steel after isothermal heat treatment

Closed-loop control of a directed energy deposition process for repair applications

AbstractAdditive manufacturing processes of the directed energy deposition family such as laser metal deposition or wire arc additive manufacturing offer great control and improved metallurgical properties over traditional processes such as casting. They are very promising for many industrial applications such as the fabrication of intricate parts with high-performance alloys as well as repair applications. However, these processes are generally very sensitive to process conditions, yet are most often operated in open loop. In this study, a closed-loop controller with a suitable error criteria based on 3D scanning data in-between layers is implemented. It is applied to various repair samples made of 316L stainless steel and Inconel 625 materials. The results show that the controller can compensate for suboptimal operating points and in-process deviations while maintaining satisfactory metallurgical and mechanical properties.

Inactivation of deposited bioaerosols on food contact surfaces with UV-C light emitting diode devices.

The airborne transmission of infectious diseases and bioaerosol-induced cross-contamination pose significant challenges in the food, dairy, and pharma industries. This study evaluated the effectiveness of 279 nm UV-C LED irradiation for decontaminating bioaerosols, specifically containing microorganisms such as Escherichia coli (C3040- Kanamycin resistant), Salmonella Enteritidis (ATCC 4931), and Pseudomonas fragi (ATCC 4973), on food contact surfaces. Borosilicate glass, silicon rubber, and stainless steel (316L) surfaces were selected for experimentation for their usage in the food industry. A 50 µL cell suspension was aerosolized at 25 psi pressure using a 4-jet BLAM Nebulizer within a customized glass chamber and then deposited onto the surface of the coupons. The serial dilution approach was used for the microbial enumeration, followed by duplicate plating. With a low Root Mean Square Error (RMSE) and high R2 values, the biphasic kinetic model for UV-C inactivation curves of all three pathogens demonstrated the excellent goodness of fit parameters. At a UV-C dose of 6 mJ cm-2, glass surfaces showed the maximum microbial inactivation (i.e., 2.80, 3.81, and 3.56 log CFU/mL for E. coli, Salmonella, and P. fragi, respectively). Stainless steel and silicon rubber surfaces showed significant microbial inactivation, but log10 reductions observed were consistently lower than glass surface. Our research indicates that UV-C LEDs (279 nm) can effectively disinfect bioaerosols on food contact surfaces.IMPORTANCEFood safety is a major public health concern, with contaminated food causing serious illnesses. UV-C light, used for germicidal action, is effective in disinfecting surfaces and is not subject to the same strict legal restrictions as chemical disinfectants, simplifying compliance with food safety regulations. In this study, we evaluated the efficacy of UV-C (279 nm) LED systems for inactivation of surface-deposited bioaerosols of kanamycin-resistant Escherichia coli (C3040), Salmonella Enteritidis (ATCC 4931), and Pseudomonas fragi (ATCC 4973). The research outcomes can be used to develop UV-based surface disinfection systems to minimize the risk of foodborne illnesses and enhance safety in high-traffic food preparation areas.

Multiscale Modeling of Nanoparticle Precipitation in Oxide Dispersion-Strengthened Steels Produced by Laser Powder Bed Fusion.

Laser Powder Bed Fusion (LPBF) enables the efficient production of near-net-shape oxide dispersion-strengthened (ODS) alloys, which possess superior mechanical properties due to oxide nanoparticles (e.g., yttrium oxide, Y-O, and yttrium-titanium oxide, Y-Ti-O) embedded in the alloy matrix. To better understand the precipitation mechanisms of the oxide nanoparticles and predict their size distribution under LPBF conditions, we developed an innovative physics-based multiscale modeling strategy that incorporates multiple computational approaches. These include a finite volume method model (Flow3D) to analyze the temperature field and cooling rate of the melt pool during the LPBF process, a density functional theory model to calculate the binding energy of Y-O particles and the temperature-dependent diffusivities of Y and O in molten 316L stainless steel (SS), and a cluster dynamics model to evaluate the kinetic evolution and size distribution of Y-O nanoparticles in as-fabricated 316L SS ODS alloys. The model-predicted particle sizes exhibit good agreement with experimental measurements across various LPBF process parameters, i.e., laser power (110-220 W) and scanning speed (150-900 mm/s), demonstrating the reliability and predictive power of the modeling approach. The multiscale approach can be used to guide the future design of experimental process parameters to control oxide nanoparticle characteristics in LPBF-manufactured ODS alloys. Additionally, our approach introduces a novel strategy for understanding and modeling the thermodynamics and kinetics of precipitation in high-temperature systems, particularly molten alloys.

The Influence of Ultrasonic Irradiation of a 316L Weld Pool Produced by DED on the Mechanical Properties of the Produced Component

Additive manufacturing of metallic components often results in the formation of columnar grain structures aligned along the build direction. These elongated grains can introduce anisotropy, negatively impacting the mechanical properties of the components. This study aimed to achieve controlled solidification with a fine-grained microstructure to enhance the mechanical performance of printed parts. Stainless steel 316L was used as the test material. High-intensity ultrasound was applied during the direct energy deposition (DED) process to inhibit the formation of columnar grains. The investigation emphasized the importance of amplitude changes of the ultrasound wave as the system’s geometry continuously evolves with the addition of multiple layers and assessed how these changes influence the grain size and distribution. Initial tests revealed significant amplitude fluctuations during layer deposition, highlighting the impact of layer deposition on process uniformity. The mechanical results demonstrated that the application of ultrasound effectively refined the grain structure, leading to a 15% increase in tensile strength compared to conventionally additively manufactured samples.

Effect of Post-Manufacturing Heat Treatment on Wear Performance of Laser Powder Bed Fusion 316L Stainless Steel Under Various Normal Loads

Effect of Post-Manufacturing Heat Treatment on Wear Performance of Laser Powder Bed Fusion 316L Stainless Steel Under Various Normal Loads

Parametric Optimization of Tig Welding of Aisi 316L Stainless Steel Using Response Surface Methodology

Parametric Optimization of Tig Welding of Aisi 316L Stainless Steel Using Response Surface Methodology

Prediction of weld morphology in laser-welded 316L stainless steel using a multilayer feedforward neural network

Prediction of weld morphology in laser-welded 316L stainless steel using a multilayer feedforward neural network

Mitigation of Stress Corrosion Cracking in Additively Manufactured Stainless Steel by Laser Shock Peening

Abstract Use of laser powder bed fusion (LPBF) stainless steel in corrosive environments is attractive due to material's high corrosion resistance and fine feature resolution, which is advantageous for fluidic applications. For this implementation to be optimized, LPBF stainless steel parts must have reduced susceptibility to stress corrosion cracking (SCC), a failure mode that is of high risk for stainless steels. Laser shock peening (LSP) surface processing has been used to improve SCC resistance in wrought metals and has also been used to improve other material properties of additively manufactured metals. However, LSP has yet to be investigated for the improvement of SCC behavior in LPBF stainless steel. This article demonstrates that not only does LSP improve time to crack initiation of LPBF 316L stainless steel in SCC testing but also improves SCC behavior differently when applied to different surfaces of the build. To explain these results, residual stress, texture, dislocation distribution, hardness, microstructure, and fracture surfaces are investigated, linking different hydrogen embrittlement mechanisms to each of the two build orientations as well as the peened and un-peened conditions. These results are supported by matching the observed crack morphologies to those simulated with dynamic crack modeling, thereby demonstrating the impact of residual stress and plastic versus brittle failure upon the observed outcome.

Rotating Bending Fatigue of Laser Powder Bed Fused 316L Stainless Steel at Various Stress Levels: Microstructural Evaluation and Predictive Modeling

ABSTRACTThis research studies the effect of variable stress levels on the rotating bending fatigue (RBF) tests of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) method. The mechanical properties and fatigue behavior were evaluated to ascertain the correlation between the applied stress levels and microstructural changes that occurred during the fatigue experiments. These relationships were further investigated using a classical model developed on the Python platform. The microstructural analysis demonstrated that the face‐centered cubic structure was maintained throughout the application of stresses, varying from 255 to 402 MPa along with no phase changes. Nevertheless, the density of shear lines on the surface was substantially influenced by variations in stress levels as demonstrated by high‐stress areas in Kernel average misorientation maps. At lower stress levels, the model analysis exhibited a higher degree of reliability, with R2 values of 96.25% at lower stress rather than 89.30% at higher stress.

Microstructural and mechanical properties study of various lattice structures of SS316L-CNTs nano composites fabricated through additive manufacturing

Abstract In this work, various lattice structures, such as FCC (face-centered), BCC (body-centered), GD (Gyroid), and BGD (bare gyroid (without CNTs)) with four different porosities (60%, 70%, 80%, and 90%), were prepared through the SLM (selective laser melting) additive manufacturing process. Stainless Steel (SS) 316L alloy was utilized as the base material, while 0.2 wt.% functionalized CNTs (Carbon Nanotubes) were employed as reinforcement. The uniform dispersion of CNTs was analyzed using FESEM, TEM, and Raman spectroscopy. The results indicated that the plateau stress increases with the addition of CNTs, as well as with relative density, whereas energy absorption increases with the addition of CNTs. However, with increasing relative densities, energy absorption nature changes from increasing to decreasing. The results showed that among all lattice structures formed with CNTs addition, the Gyroid lattice exhibited the highest plateau stress, while the BCC lattice exhibited the lowest plateau stress.

Effect of annealing and strain rate on the microstructure and mechanical properties of austenitic stainless steel 316L manufactured by selective laser melting

Effect of annealing and strain rate on the microstructure and mechanical properties of austenitic stainless steel 316L manufactured by selective laser melting

Contribution of the Self‐Heating Method in the Characterization of the Fatigue Damage of Materials With Defects Resulting From Additive Manufacturing

ABSTRACTThis paper investigates the ability of the self‐heating method to characterize the fatigue behavior of 316L stainless steel produced by Laser Powder Bed Fusion. Nearly dense cylinders are built vertically using various process parameters corresponding to various volumetric energy densities. Fatigue specimens are then machined from these cylinders and polished. Fully reversed tension–compression fatigue tests (R = −1) are conducted. The self‐heating method is used for the estimation of the fatigue limits. These fatigue limits are compared to results obtained from S‐N curves in the high cycle regime. Whatever the set of process parameters, the self‐heating curves show three distinct domains of heat dissipation. Thanks to microstructure analysis, fractographic observations, and correlations with S–N curves, these domains can be closely linked to damage mechanisms associated or not with defects.