Properties Of 316L Stainless Steel Research Articles

选区激光熔化316L不锈钢成形工艺与性能研究

选区激光熔化316L不锈钢成形工艺与性能研究

Research on Dynamic Mechanical Properties of 316L Stainless Steel Processed Using Selective Laser Melting

Research on Dynamic Mechanical Properties of 316L Stainless Steel Processed Using Selective Laser Melting

Comparative Forming Size and Mechanical Properties of 316L Stainless Steel Fabricated Using Laser/Plasma Arc Directed Energy Deposition

Comparative Forming Size and Mechanical Properties of 316L Stainless Steel Fabricated Using Laser/Plasma Arc Directed Energy Deposition

Influence of hot isostatic pressing on the properties of 316L stainless steel, Al-Mg-Sc-Zr alloy, titanium and Ti6Al4V cold spray deposits

In this paper an effect of capsule-free hot isostatic pressing (HIP) on the porosity and mechanical properties of different cold spray deposits was experimentally evaluated. The HIP post-treatment significantly decreased (more than 2 times) the porosity of 316L and pure titanium deposits. The densification effect of HIP on the porous Ti6Al4V deposit was significantly less pronounced. Mechanical properties of the deposits after HIP were also improved. In particular, the tensile strength of the stainless steel, pure titanium and Ti6AL4V increased from 30 MPa, 70 MPa and 20 MPa to 211 MPa, 480 MPA and 560 MPa correspondingly. Compressive strength of the Al-Mg-Sc-Zr alloy samples after HIP was also increased ~25%. Improvement of mechanical properties is explained by material diffusion and microstructure changes during HIP cycle.

Compressive Properties of 316L Stainless Steel Topology‐Optimized Lattice Structures Fabricated by Selective Laser Melting

Some lattice structures with different relative densities (0.15–0.5) are designed by topology optimization and fabricated by selective laser melting. The temperature history of lattice structures is monitored experimentally to reveal the forming reason of the deviation of relative densities. The effect of relative densities on compressive properties of lattice structures, including mechanical properties, failure mechanism, and energy absorption capabilities, are systematically investigated. The results show that compressive properties of lattice structures vary dramatically with the changing of relative densities. Due to the existence of surface‐shaped struts, the compressive strength of topology‐optimized lattice structures has superior performance comparing to most of the other structures with rod‐shaped struts. The failure mechanism of lattice structures can be changed from shear‐ to bending‐dominated when increasing relative densities as a result of decreasing the thickness of struts. A systematic investigation of the fracture generation of struts is conducted through both deformation analysis and the finite element method. The fitting curves are established successfully to predict the mechanical properties of designed lattice structures. The aforementioned results verify the feasibility of designing high‐performance cellular structures via topology optimization. Moreover, herein a comprehensive solution to tailor desired properties for satisfying the requirements of functional components is provided.

Structural and micromechanical properties of 316L stainless steel produced by selective laser melting

The structure and micromechanical properties of a 316L stainless steel produced by the selective laser melting (SLM) technique have been studied in its initial state and the following heat treatment: quenching from 1050 °C and 4-hour annealing at 480 °C. The heat treatment does not result in changing the steel phase composition, however, it reduces the microhardness by 5%, HM hardness (Martens hardness) by 12% and indentation hardness by 16% at Hit maximum load. The heat treatment also increases the E* contact elasticity modulus by 14% due to the lower porosity of the material. As soon as heat treatment provides no strengthening of the steel synthesized by SLM, deformation processing, chemicothermal treatment and application of thin coatings may become quite promising strengthening methods.

Influence of substrate temperature on microstructural and mechanical properties of 316L stainless steel consolidated by laser powder bed fusion

This study investigates the microstructure and mechanical properties of 316L stainless steel (316LSS) samples fabricated by additive manufacturing (AM), in order to optimise the process for improving the properties of 316LSS parts built by laser powder bed fusion (LPBF). Accordingly, a substrate heating was performed on an SLM 280HL printer fitted with an experimental heating device. During the process, samples are built on a substrate heated up to 600 ∘C. The substrate temperature significantly influences the microstructural evolution and mechanical properties of manufactured parts. Concerning tensile properties, the ultimate tensile strength (UTS) and yield strength (YS) decrease as a function of the substrate temperature whereas the elongation (El) increases as a function of the substrate temperature. These results are similar to those obtained with a post-heat treatment performed on parts manufactured by forging or LPBF. The tensile and impact energies reach values higher than the minimum requirement for 316LSS manufactured by forging, according to the RCC-MRx code used for materials dedicated to French nuclear applications. When the substrate temperature is equal to 350 ∘C, the UTS, YS, El and impact energy reached 596 ± 5 MPa, 489 ± 3 MPa, 48 ± 3% and 123 ± 20 J, respectively. Finally, this study demonstrates that heating the substrate during the process is a promising solution to optimise the fabrication route by suppressing post-process heat treatment of 316LSS made by LPBF.

Effect of Different Molding Process on Mechanical Properties of 316L Stainless Steel

The effects of laser selective melting (SLM) and rolling on the mechanical properties of 316L stainless steel were studied. The morphology and fracture characteristics after impact were characterized by means of an optical microscope (OM) and scanning electron microscope (SEM), Meanwhile, tensile strength, hardness, and impact toughness are characterized. The results show that compared with the roll forming, the 316L stainless steel group formed by laser selective melting has surface holes, cracks and spheroidization, and the grains are smaller, the dimples are smaller and shallower, and the strength and hardness are higher than the roll forming. Plastic toughness is much lower than that of rolling.

Improving fluid retention properties of 316L stainless steel using nanosecond pulsed laser surface texturing

Stainless steel has been used as a successful biomaterial for decades. In this study, a pulsed nanosecond laser was used to create patterned surfaces of stainless steel coupons to study the effect of patterning on fluid retention and biocompatibility studies of laser patterned and control surfaces. An AVIA 355 nanosecond pulsed laser was used with different laser parameters to create unique “peak and valley” structures (uniform textured surface) on stainless steel coupons of size of 1 × 1 × 0.1 cm3. The surface structural changes can be attributed to the Gaussian beam profile of the laser. The coupons were observed under a scanning electron microscope to understand the change of the material surface profile. An optical profilometer was used to measure the surface roughness and compare it with a nontextured or control surface. The contact angle measurement showed a decrease in the contact angle, reduced to 71.6° from 82.2° making the patterned surface more hydrophilic. A biocompatibility study of the stainless steel was performed to evaluate the effect of surface modification on its impact on biocompatibility. The cell viability of the patterned sample was 94% as compared to 84% for the unpatterned surface. A simulation of the process was run using flow3d® to understand the behavior of the material during the texturing process. The results obtained from the simulation process were compared with the experimental data and found to be in good agreement. The effects of Gaussian beam, vapor pressure, and overlapping of the beam were also analyzed in the simulation process.

Effects of geometric dimension and grain size on impact properties of 316L stainless steel

The effects of geometric dimension and grain size on impact properties of 316L stainless steel were clearly revealed based on the analysis of impact properties and fracture morphologies. Results showed that the large Charpy impacting samples exhibited a higher impact toughness than the small samples, which was ascribed to the higher value of Splain-strain/Stotal (70–80%). The mean size of the dimples in the plain-strain region increased with the increasing of grain size. For large-sized grains with smaller grain boundaries, the cracks are prone to form larger dimples during the propagation process, which can consume a high impact energy accompanied by a high impact toughness.

Predicting mechanical properties of 316L stainless steel subjected to SMAT: A sequential DEM-FEM investigation

Surface mechanical attrition treatment (SMAT) is a specialized cold working method that is used to induce compressive residual stresses and to refine crystalline grains at the surface of metal components. This technique is increasingly employed in different industries, and the control and optimization of the method require a fundamental understanding and an accurate process modelling. In this study, a numerical modelling approach capable of accurately predicting the residual stress and plastic deformation during SMAT was developed by combining discrete element method (DEM) and finite element method (FEM). In the proposed framework, the spatial and statistic distributions of impact positions, angles and velocities from DEM simulations are utilized in the FEM simulations. The effects of treatment duration, shot number, shot size and impact angle distribution on residual stresses, plastic deformation and roughness of the treated component are investigated. The numerical results are compared with available experimental data with good agreements. The proposed numerical method demonstrates capabilities to establish the linkages between processing parameters and material properties during SMAT treatment.

Effect of cold working on crack growth rate of environmentally assisted cracking of 316L SS

Environmentally assisted cracking (EAC) is a main failure mode of key structural materials of nuclear power pressure vessels and pipelines in service. The key structural materials of nuclear power will undergo plastic deformation due to cold working during manufacturing, assembly and welding, and cold working will affect the EAC crack growth rate. In order to understand effect of cold working on crack growth rate of EAC, a combination of theory, experiment and finite element simulation is used. There are experiments to obtain the mechanical properties of 316L stainless steel at different degrees of cold working, and the creep characteristics of 316L stainless steel at low temperature and high stress were obtained by experiment. Based on experiment and theoretical analysis, creep rate of crack tip is used to replace strain rate of crack tip in Ford-Andresen model, and effect of cold working on crack growth rate of EAC is analyzed with hardening at crack tip and without hardening at crack tip. The results show that cold working accelerates crack growth rate of EAC, and the hardening of crack tip micro zone restrains crack growth rate of EAC, causing the “hysteresis” phenomenon in the EAC crack growth process. It is more reasonable to use creep rate of crack tip instead of strain rate of crack tip to calculate crack growth rate of EAC.

Effect of Processing Atmosphere and Secondary Operations on the Mechanical Properties of Additive Manufactured AISI 316L Stainless Steel by Plasma Metal Deposition

Plasma metal deposition (PMD) is an interesting additive technique whereby diverse materials can be employed to produce end parts with complex geometries. This study investigates not only the effects of the manufacturing conditions on the final properties of 316L stainless steel specimens by PMD, but it also affords an opportunity to study how secondary treatments could modify these properties. The tested processing condition was the atmosphere, either air or argon, with the other parameters having previously been optimized. Furthermore, two standard thermal treatments were conducted with the intention of broadening knowledge regarding how these secondary operations could cause changes in the microstructure and properties of 316L parts. To better appreciate and understand the variation of conditions affecting the behavior properties, a thorough characterization of the specimens was carried out. The results indicate that the presence of vermicular ferrite (δ) varied slightly as a consequence of the processing conditions, since it was less prone to appear in specimens manufactured in argon than in air. In this respect, their mechanical properties suffered variations; the higher the ferrite (δ) content, the higher the mechanical properties measured. The degree of influence of the thermal treatment was similar regardless of the processing conditions, which affected the properties based on the heating temperature.

Deformation mechanisms and enhanced mechanical properties of 304L stainless steel at liquid nitrogen temperature

The deformation mechanisms and enhanced mechanical properties of a fine-grained 304 L stainless steel were revealed at liquid nitrogen temperature. A remarkable Lüders-type deformation and subsequent dislocation slipping/accumulation deformation synergistically contribute to its good ductility. The enhanced strength was resulted from low-temperature strengthening and high density of dislocation storage hardening.

Effects of build direction on tensile and creep properties of 316L stainless steel produced by selective laser melting

AbstractThe influence of build direction on the mechanical properties of SS316L produced by selective laser melting was investigated. The tensile tests were performed at room temperature for vertical and horizontal specimens. Large crater‐like voids were found, which are believed to be responsible for the reduced strength and premature failure of the vertical specimens, whereas the nano‐sized dimples were detected on the fracture surface of the horizontal specimens. Creep tests were also conducted at 650°C in the applied stress range of 149 to 226 MPa in vertical and horizontal directions. The vertical direction specimen showed better creep resistance. The micro‐cracks were delayed compared with the horizontal case. Optical micrographs of the tip of the creep rupture specimens along the cross‐sectional area were observed. The micro‐cracks located at grain boundaries. The grain shapes orientated in the applied stress direction for the vertical specimens, and perpendicular to the applied stress direction for the horizontal specimens.

Study on microstructure and tensile properties of 316L stainless steel fabricated by CMT wire and arc additive manufacturing

An austenitic stainless steel 316L part was fabricated by cold metal transfer wire and arc additive manufacturing (CMT-WAAM), and its microstructure, microhardness and tensile properties were investigated. Results showed that the as-built 316L part exhibited a multilayered structure along the building direction. In the transverse direction (perpendicular to scanning direction) of each layer, there was also a multilayered structure of alternating overlapping zone (OA) and re-melting zone (RA). Compared with the OA, the RA had higher ferrite content, smaller austenite dendrite size, more dispersed orientation and lower residual stress. The overall multilayered structure and the intra-layer non-equilibrium microstructure exhibit a great influence on the mechanical properties of as-built 316L part. Along the building and transverse direction, the microhardness distribution in the OA was uniform, while the RA showed a trend of lower hardness in the middle and higher hardness on both sides of the RA layer. The effect of multilayered structure on tensile properties was stronger in the transverse direction than that in the building direction. The deformation feature was obviously inconsistent between the OA and RA. Local necking and fracture always occurred in the OA. Microvoids trended to initiate at silicate impurity particles, grow into large cracks, and finally lead to material failure during tension.

Effect of scanning strategies on the microstructure and mechanical behavior of 316L stainless steel fabricated by selective laser melting

Five scanning strategies were applied for relating the microstructural and crystallographic morphology to the mechanical properties of 316L stainless steel fabricated by selective laser melting (SLM). The results indicate that scanning strategies have a significant effect on the microstructure, grain growth, grain size and therefore mechanical properties of SLM-built 316L stainless steel. Applying the scanning strategy with the rotation angle between successive layers breaks the columnar growth of grains and fine equiaxial grains are formed, leading to an improvement of tensile strength and good ductility of SLM-built samples. Moreover, the microhardness is improved by applying the scanning strategy with a rectangular pattern. This work demonstrates the scanning strategy during SLM process acts as an essential factor affecting energy input, and therefore tailors the meso-/micro-scale structure and mechanical behavior of metals.

Impact of industrially applied surface finishing processes on tribocorrosion performance of 316L stainless steel

This investigation addresses the effect provided by industrial surface finishes on the tribocorrosion properties of 316L stainless steel exposed to NaCl solution. Three distinct surface treatments were evaluated: passivation (SSO), electropolishing-passivation (SSEP) and micro-undulation (SSM mechano-chemical + electropolishing + passivation). For the tribocorrosion tests, a potentiostatic approach was considered in order to highlight the alloy behavior under two opposite situations, where repassivation of the surface would be thermodynamically possible or not (anodic or cathodic polarization, respectively). The outcomes demonstrated that the surface treatments were either harmful (SSEP) or beneficial (SSM) in terms of resulting tribocorrosion resistance. The specific topography of the micro-undulated sample decreased the real contact area and improved the surface lubrication in aqueous medium. SSEP presented the highest chemical wear and several factors seemed to have contributed for it, including the chemical, mechanical and structural properties of the passive film. Regardless the surface treatment, the tribocorrosion response was modified by the applied potential and more severe damage was determined under anodic polarization. At this potential, calculations of the total surface degradation suggested that volume loss was mainly dominated by chemical wear.

Electroplating titanium film on 316L stainless steel in LiCl–KCl–Tix+ (2 < x<3) molten salts

To improve the anti-corrosion properties of 316L stainless steel, titanium (Ti) metal films were electroplated on it using LiCl–KCl molten salts as the electrolyte, and low-valence Tix+ (2 < x<3) as the solute. The solute was produced by the reaction of Ti4+ and Ti0 via mixing K2TiF6, and Ti metal (sponge Ti) in the melts. Anti-corrosion test has shown significant enhancement in the stability of the Ti-coated 316L due to the presence of Ti film. However, the anti-corrosion properties did not enhance with an increase in the thickness of the Ti layers owing to a possible defect in the thicker Ti layers.

Experimental characterization and micromechanical-statistical modeling of 316L stainless steel processed by selective laser melting

Additive manufacturing (AM) is regarded as one of the breakthrough innovations since the 19th century, whose impact on the manufacturing world is recognized as the same with the impact of airplane on the transportation industry [1]. Selective laser melting (SLM), one of the most popular AM techniques for processing metallic materials, has demonstrated its great potentials in medical, aerospace and automotive applications. The SLM technique itself is a complex metallurgical process, involving multi-physics phenomenon in laser scanning, powder melting and bonding procedure. Such a process may introduce a variety of defects and flaws such as pores and cracks, significantly reducing the mechanical performance of the final products. In this paper, we present experimental studies and micromechanical modeling to investigate the effects of the internal pores on the mechanical properties of 316L stainless steel (SS316L) processed by the SLM technique. Specifically, the internal pore characteristics such as size, morphology, spatial distribution and porosity (defined as the total volume of the pores divided by the total volume of the material) of the SLM processed SS316L is experimentally characterized and correlated with the mechanical properties. More importantly, a micromechanical model taking into account the statistical pore characteristics from the XCT analysis is developed to predict the elastic properties of the SS316L product. The numerical prediction results show good agreement with two analytical models and the experimental characterization of the mechanical properties. The present study provides future designers a methodology in predicting the mechanical properties using the XCT analysis results, which is a promising possibility of saving the expensive cost on destructive testing.