316L Stainless Steel Research Articles

Fabrication and Process Monitoring of 316L Stainless Steel by Laser Powder Bed Fusion with µ-Helix Scanning Strategy and Narrow Scanning Line Intervals

Fabrication and Process Monitoring of 316L Stainless Steel by Laser Powder Bed Fusion with µ-Helix Scanning Strategy and Narrow Scanning Line Intervals

Assessment of High-Temperature Oxidation Properties of 316L Stainless Steel Powder and Sintered Porous Supports for Potential Solid Oxide Cells Applications

Assessment of High-Temperature Oxidation Properties of 316L Stainless Steel Powder and Sintered Porous Supports for Potential Solid Oxide Cells Applications

Process parameter translation strategies for variable directed energy deposition spot size using 316L, copper, and Inconel 625

Directed energy deposition (DED) is a form of additive manufacturing available across a variety of laser spot diameter values, often referred to as spot sizes. However, there is no method to easily transfer process parameters across discrete spot sizes, leading to DED process parameters that are equipment specific and not widely applicable. In this study, a strategy is proposed and investigated for five spot sizes that keep the areal energy density constant while varying power, feed rate, and powder flow during the deposition of 316L stainless steel. An assessment of trends in hardness and microstructure is possible due to the novel production of components of a single material across several spot sizes using a single nozzle on a single DED system. The proposed strategy was used to nullify the hardness drop during functional grading of Inconel 625 and pure copper, enabling fabrication of multi-material sample that does not compromise desirable properties. This application shows the value in establishing more efficient process parameter development and understanding spot size influences on geometric and material property flexibility, to enable a more diverse powder-based DED design space and to increase the industry adoption of DED systems.

Deformation by light Impacts to Create a Near-Surface Nano- and Microstructured Layer in AISI 316L Stainless Steel

Deformation by light Impacts to Create a Near-Surface Nano- and Microstructured Layer in AISI 316L Stainless Steel

A six degrees of freedom femtosecond laser system for fabrication of small-scale mechanical property specimens.

We present the details of a novel ultra-short pulsed laser machining workstation that has been employed for high-throughput laser machining of small-scale mechanical property specimens. This system employs a six degrees of freedom hexapod positioning stage capable of macroscopic movements at high positional accuracy. We developed a methodology that uses quantitative image analysis to measure key parameters required to minimize the hexapod positioning and rotational error. Application of this system to laser machining of small-scale 316L stainless steel tensile specimens and ultra-high molecular weight polyethylene compressive specimens using eucentric tilt and rotation about the specimen axis will be shown, where serial laser milling at a specimen tilt angle of 10° was used to effectively eliminate any taper in the sample cross section that is typically found in laser machining.

Influence of friction stir processing (FSP) on arc directed energy deposited 316L stainless steel: a corrosion science study

Friction stir processing (FSP) was employed as a post-printing surface modification technique to enhance surface properties of arc-directed energy deposited 316L austenitic stainless-steel parts. Corrosion properties and passivity of stir zone and base metal were investigated in 3.5 wt.% NaCl solution. Results reveal a gradual improvement in corrosion protection ability of formed passive film on the alloy's surface over time. Specifically, FSPed region exhibited superior passive behavior and uniform corrosion resistance compared to base metal. This improvement was attributed to a more homogeneous microstructure of stir zone, which hindered micro-galvanic coupling effect. However, it was observed that FSP-treatment did not effectively impede the propagation of pitting corrosion.

Experimental studies on mechanical properties of metal fused filament fabricated SS316L

Fused filament fabrication is a simple and commercially popular additive manufacturing (AM) technique for developing high-accuracy polymer-based materials. In this experiment, a retrofit type of setup was developed to manufacture stainless steel 316L–based products. The current study focuses on the encapsulation of stainless steel with polylactic acid to prepare the filament for 3D printing. The effects of printing parameters such as layer thickness, infill density, and extruder temperature on responses like density, surface roughness, micro-hardness, and material/filament consumption have been studied. A Box–Behnken design approach was employed to systematically evaluate 15 specimens under varying conditions. The results revealed that a maximum relative density of 97% was achieved with a layer thickness of 0.2 mm, an extruder temperature of 215°C, and a 100% infill density. Additionally, the optimized infill density demonstrated a significant effect on both hardness and surface roughness, confirming the importance of precise control over processing conditions for improving the performance of the printed parts. The findings contribute to the advancement of metal-polymer composite filaments in additive manufacturing, highlighting their potential for producing complex, high-performance components.

Impact toughness of LPBF 316L stainless steel below room temperature

The fracture behavior of LPBF 316L stainless steel in rapid loading conditions was characterized from room to cryogenic temperatures. Instrumented impact toughness tests allow to determine the influence of the microstructural features of this material on its crack initiation and propagation behavior. In the stress-relieved, homogenized/partially recovered and recrystallized states, LPBF 316L exhibit gradual impact toughness decreases between 20 °C and – 193 °C, with close toughness loss ranging from 0.38 to 0.55 J cm−2/°C. These values were similar to those reported by the literature for hot isostatically pressed (0.35–0.58 J cm−2/°C) and wrought (0.45–0.51 J cm−2/°C) 316L stainless steels, meaning that the microstructural features of LPBF 316L (segregations cells, dislocations cells, oxide particles, etc.) did not significantly influence the temperature sensitivity of its fracture properties. Whatever the testing temperature and microstructural state, fully ductile fracture occurred by decohesion at the oxide/matrix interfaces and void growth into dimples. The martensitic transformation during deformation at low temperature did not appears to play a significant role in the temperature sensitivity of the decrease in impact toughness of these materials. The latter is likely a consequence of the loss of ductility of the austenitic matrix, especially, under localized strain conditions.

Fabrication of novel 316L stainless steel scaffolds by combining freeze-casting and 3D-printed gyroid templating techniques

Porous metals have been widely investigated as bioimplants to repair cancellous bone defects. Nevertheless, how to endure extreme stress and strike a balance between load-bearing performance, elastic modulus, and permeability are important issues. Freeze-casting is a novel technique for manufacturing micro-scale open-cellular lamellar porous materials. However, the pore size is relatively small because of the inherent constraints of the ice template. On the other hand, the scaffold with gyroid pore structures has been proven to have higher permeability due to its larger and smoother channels. To combine the advantages of both porous structures, the present study aims to develop dual-scale 316L stainless steel (316L SS) porous structures by incorporating the 3D-printed gyroid templates into the freeze-casting to further improve the lightweight, specific strength, energy absorption, and permeability of the porous structures. The results showed that macro-scale gyroid channels were successfully built into the micro-scale open-cellular lamellar porous scaffolds. The porosity of dual-scale scaffolds was 70.1 %–74.4 %, which was higher than that of 53.1 %–66.5 % in the single-scale scaffolds. The elastic moduli of the single-scale scaffolds were higher than that of the dual-scale scaffolds; both were within the range of human cancellous bone, demonstrating their mechanical compatibility. Furthermore, the dual-scale scaffolds presented a prominent rise in permeability compared to the single-scale scaffolds. Notably, the permeability of the 3G series scaffolds was comparable to human cancellous bone. In summary, the hierarchical 316L SS scaffolds with controllable macro-scale gyroid channels exhibit great potential for biomedical applications.

Effect of heat treatment on the corrosion resistance of 316L stainless steel manufactured by laser powder bed fusion

Understanding the influence mechanism of microstructures and inclusions during heat treatment on the corrosion resistance of L-PBF 316L stainless steel (SS) is crucial for steel quality control and subsequent industrial application. In this study, the evolution of microstructure, inclusions and passive film in the L-PBF 316L SS during heat treatment at the temperature of 1000 °C and 1200 °C for 2 h, including crystal characteristics, dislocation density, passivation film composition and so on, were characterized by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The corrosion resistance of L-PBF 316L SS samples was evaluated by Tafel test and electrochemical impedance spectroscopy test. The corrosion mechanisms of L-PBF 316L SS before and after heat treatment were clarified to elucidate the intrinsic effect of microstructure and inclusions on the corrosion resistance of the steel. Results showed that the heat treatment conducted at 1200 °C effectively reduced the number of grain boundaries and induced a substantial number of Σ3 twin grain boundaries in the L-PBF 316L SS, thereby efficiently impeding the precipitation of detrimental phases and reducing corrosion susceptibility at the grain boundaries. Meanwhile, the recrystallization-induced rearrangement of dislocations and the homogenization of grains effectively facilitated the growth of passivation film, thereby increasing the corrosion resistance of HT1200 sample. Additionally, the increase of MoO3 content compensated for the detrimental impact on the stability of the passivation film resulting from the reduction in chromium oxide content. Transformation from the MnO–SiO2–Cr2O3 inclusions in the as-built sample to the SiO2 inclusions in the HT1200 sample would also retard the penetration of corrosive ions into the steel matrix.

Near-full density enabled excellent dynamic mechanical behavior in additively manufactured 316L stainless steels

Mechanical properties of additively manufactured alloys are momentously affected by the fabrication defects, thus limiting their applications in extreme conditions. Here we report on a near fully dense 316L stainless steel via optimized laser processing parameters. The results reveal that the dynamic mechanical response exhibits much greater sensitivity to defects than the quasi-static one. The densest specimen (porosity < 0.01 %, 260W-316L) exhibits superior spall strength of 3.87 GPa and negligible damage fraction of 0.03 % at peak stress of 4.8 GPa, which are 12 % higher and 92 % smaller than those of 0.18 % porosity specimen (300W-316L). For both horizontal and vertical impacts, hardly any anisotropy of spall strength is observed in 260W-316L, demonstrating the crucial role of the pore defects on the dynamical behavior. Moreover, dislocation slip dominated spallation mechanisms have been observed in the additively manufactured 316L specimens, accompanied by a small amount of deformation twinning and martensitic transitions. This comprehensive understanding of the defect-dependent spallation behavior and deformation mechanisms provides valuable insights for optimizing the dynamic mechanical properties of additively manufactured metals and alloys.

Influence of printing parameters on the mechanical behavior of 3D-printed SS316L parts manufactured using laser hot wire directed energy deposition

Hybrid manufacturing combines the simultaneous benefits of additive manufacturing (complex geometries, part consolidation, and mass customization) with the advantages of subtractive manufacturing (superior surface finish and enhanced dimensional accuracies) by integrating a suite of complementary traditional processes into a base platform of additive manufacturing. The use of hybrid technology has grown in recent years given its capabilities on repairing metallic structures, producing parts with conformal cooling features, and manufacturing functionally graded products. These kinds of capabilities are of great interest to the medical implant, energy, automotive, maritime, and aerospace industry sectors, among many other fields. This work investigated the mechanical properties of stainless steel (SS) 316L as a function of different tool paths strategies using an integrated 5-axis CNC hybrid Mazak system with a laser hot wire deposition system (LHWDS). This study includes the evaluation of different printing parameters and their impact on the quality of the printed bead as well as the incorporation of a structure–property material relationship based on the mechanical performance of the manufactured coupons.

Nickel release from 316L stainless steel following a Ni-free electroplating cycle

Electroplating can induce nickel release even from 316L stainless steel, typically considered safe. In this work, the influence of different electroplating processes and surface treatments on nickel release was evaluated. The nickel release was tested according to the EN 1811 standard. The impact of surface roughness on nickel release was assessed by comparing polished and unpolished samples. Results indicate that internal stresses can worsen nickel release, while increasing the thickness of the precious metal layer is beneficial. To corroborate our hypothesis, it was verified that coatings obtained through physical vapor deposition (PVD), without removing the passivation layer of the steel, did not release nickel. For these reasons, we identified the main cause of nickel release as the combined effect of the removal of the passivation layer of stainless steel and the microporosity of the electroplating process.

Fatigue Response of Additive-Manufactured 316L Stainless Steel

This study investigated the fatigue performance of 316L stainless steel fabricated via laser powder bed fusion (LPBF). Stress-controlled fatigue tests were performed at different stress amplitudes on vertically built samples using a frequency of 15 Hz and a stress ratio of 0.1. The stress amplitudes were varied to provide the cyclic response of the materials under a range of loading conditions. The average fatigue strength was determined to be 92.94 MPa, corresponding to a maximum stress of 185.87 MPa. The microstructures were observed through scanning electron microscopy (SEM) with the aid of electron backscattered diffraction (EBSD), and the average grain size of the as-built samples was determined to be 15.6 µm, with most grains having a &lt;110&gt; preferred crystallographic orientation. A higher kernel average misorientation value was measured on the deformed surfaces, revealing the increased misorientation of the grains. Defects were observed on the fractured surfaces acting as crack initiators while deflecting the crack propagation paths. The fatigue failure mode for the LPBF 316L samples was ductile, as illustrated by the numerous dimples on fracture surfaces and fatigue striations.

Optimization of TIG welding parameters for enhanced mechanical properties in AISI 316L stainless steel welds

Optimization of TIG welding parameters for enhanced mechanical properties in AISI 316L stainless steel welds

In‐Plane Crashworthiness of Gradient Curved‐Walled Honeycombs: Experimental, Numerical Simulation, and Theoretical Analysis

Honeycombs are widely used in engineering protection, while the gap between peak and mean stresses remains to be narrowed, and the interaction effects among walls are weak. To break these limits, gradient curved‐walled honeycombs have been proposed recently. However, their in‐plane crashworthiness has never been studied, which restricts the actual applications in complex load environment. For this purpose, this article adopts experiments, finite‐element simulations, and theoretical analysis to reveal in‐plane crash performance of gradient curved‐walled honeycombs. Quasistatic and dynamic experiments are carried out for 3D‐printed honeycomb specimens made of 316L stainless steel, and numerical simulations are conducted by ABAQUS/Explicit. Compared to traditional straight‐ and curved‐walled honeycombs, gradient curved‐walled honeycombs display stabler deformation mode and more efficient mechanical response. Their EA and SEA are respectively 25.5% and 6.4% larger than straight‐walled honeycombs, and their energy absorption and force efficiencies are nearly 2.4 and 5.3 times larger, respectively. On this basis, plastic hinge model with high accuracy has been established, to derive the analytical solutions of their force–displacement relations. This work extends the comprehensive properties and application prospects of gradient curved‐walled honeycombs and sets an example to develop plastic hinge analysis with effective simplification and desirable accuracy on complex‐shaped structures.

Effect of Load Cycling on High Temperature Creep of 316L Stainless Steel

For components in concentrating solar thermal plants, the creep mechanism will cause a significant portion of material damage to receivers, storage tanks, turbines and pipework. These components will undergo conditions where loads, temperature, or both load and temperature are not constatnly applied. This creep damage process will not resemble the constant load creep tests used to characterise creep of materials. Therefore, creep tests incorporating a load cycle were undertaken to obtain a better understanding of how high temperature materials respond to these cyclic conditions. These tests showed that when time under load was considered, creep undertaken under load cycling conditions were accelerated relative to constant load conditions. A modified Larson-Miller approach was used to assess this effect and determine an equivalent stress where constant load test data agrees with the cycled test data. This found that cycling the load was equivalent to if the system were under 3 and 7 MPa higher stress, for tests which were loaded for 12 hrs and 6 hrs per 24 hrs respectively. This could be a potential approach to simply and easily consider these load cycling effects for design and life analysis.

Interaction of contour and hatch parameters on vertical surface roughness in laser powder bed fusion

In Laser Powder Bed Fusion (L-PBF), surface roughness is pivotal for controlling the mechanical and functional performances, as well as the geometrical accuracy of the final product. This study extensively investigated the interactions of hatch and contour processing parameters, along with contour offset distance, on vertical surface roughness for 316L stainless steel in L-PBF. Melt pool morphology and surface arithmetic average roughness (Sa) were quantified using confocal microscopy, while scanning electron microscopy was employed to interpret the detailed microstructure of surface features. Under low volumetric energy density (VED) hatch conditions (e.g., 66.7 J/mm3), varying the contour offset distance has a negatable effect on the surface roughness when the contour VED is lower than 121.6 J/mm3, remaining relatively smooth surfaces dominated by bare melt tracks with sparely attached partially melted particles. Increasing the hatch or contour VED (e.g., 166.7 J/mm3), dross formation, identified by the microstructural differences and explained by the melt pool instability and migration, is inevitable, which dictates the surface roughness with higher Sa values. The larger contour offset distance further promotes the dross occurrence with irregularity and increases Sa. Employing a low contour VED with an appropriate offset distance and adopting the contour-first scan strategy was demonstrated as an effective solution to reduce the dross formation. Through the analysis of melt pool behavior, surface topography, and microstructure, this study elucidates the mechanisms governing dominant surface characteristics under the combined influence of hatch and contour parameters. It lays the foundation for precise control of surface roughness without altering hatching parameters, enabling the tailored manipulation of performance in additively manufactured structures.

Repairability and effectiveness in direct energy deposition of 316L stainless steel grooves: A comparative study on varying laser strategy

Direct energy deposition (DED) has gained attention in the field of metal repair because of its ability to integrate additively deposited material with preexisting components. Having the beneficial aspects of depositing right material, DED is evaluated the best option for repair deposition. Machining grooves in damaged components is the common first to repair, which is necessary to remove cracked or damaged material and provide suitable geometry for deposition. Preprocessing as grooving is commonly applied to prevent the propagation cracks or tears. However, challenges such as dimensional error and crack induced by residual stress emerge owning to complex interactions between the DED parameters and groove geometry during repair deposition. This study investigates effective deposition strategies for repairing 316L stainless steel grooves with wall-angles of 90° and 135° by exploring the relationship between the repair integrity and parameters such as groove angles, laser energy input, and powder supply, all with reference to the underlying mechanism of metallurgical bonding in angled areas. Based thereon, a modified effective repair strategy is proposed, using enhanced dual laser power to address bonding issues in the angled areas. Samples repaired using this method exhibit a defect-free groove–deposit interface and a continuous columnar-grained microstructure with abrupt changes in grain size between the repaired area and groove. This microstructural heterogeneity results in an exceptional combination of strength and ductility when compared to the base material and samples repaired using a single laser strategy. The findings of this study provide insights into the optimization of DED strategies for achieving robust metallurgical bonding within grooves, thereby advancing technological maturity in the field of metal repair.

Flow Strength Measurements of Additively Manufactured and Wrought 304L Stainless Steel up to 200 GPa Stresses

Flow Strength Measurements of Additively Manufactured and Wrought 304L Stainless Steel up to 200 GPa Stresses