SUS316L Stainless Steel Research Articles

Strain effect on microstructural properties of SUS 304L joint by PAW+GTAW

JIS SUS 304L stainless steel was joined by a combination welding process of plasma arc welding and gas tungsten arc welding (PAW+GTAW). Then pre-strain treatment on 304L welded joint of 9 % was carried out using uniaxial quasi-static tensile at room temperature. Effect of strain on microstructure evolution in joint was analyzed by field emission scanning electron microscope (FESEM) and on mechanical properties was also studied. The results indicated that the pre-strain rate of 304L joint showed inhomogeneity including 3 % in the weld metal and 13 % in the heat-affected zone (HAZ), which induced martensitic transformation occurring in HAZ. Tensile strength of the joint increased from 700 MPa as welded to 804 MPa after pre-strain treatment at room temperature, and it reached 1700 MPa from 1480 MPa as welded at low temperature of −196 °C. Impact energy in the HAZ was the least among the whole 304L weld, but it was still 94 J at −196 °C after pre-strain. The fracture morphology showed large numbered of cleavage steps with elongated parabolic dimples.

Determine The Suitable Heat Input Range for Butt Joint Made by Heat Resistance Stainless Steel SUS316L by Using the Numerical Simulation

One of the methods for reducing the production costs to increase competitiveness is to minimize waste products as well as the cost of testing products, and numerical simulation is a useful tool to solve this task. In this study, the authors use SYSWELD software to compute in advance the suitable heat input range to weld specific layers in heat-resistant stainless steel butt welded joints in chemical plants, oil and gas, and energy. The simulation results show that with the butt-welded joint made by SUS316L steel in 8 mm thick and welded by the MIG welding process, the appropriate heat input of the root pass is 506 J/mm ≤ qđl ≤ 650 J/mm and the heat input suitable for cap pass is 754 J/mm ≤ qđl ≤ 1066 J/mm.

Improved Biological Responses of Titanium Coating Using Laser-Aided Direct Metal Fabrication on SUS316L Stainless Steel.

Direct metal fabrication (DMF) coatings have the advantage of a more uniform porous structure and superior mechanical properties compared to coatings provided by other methods. We applied pure titanium metal powders to SUS316L stainless steel using laser-aided DMF coating technology with 3D printing. The purpose of this study was to determine the efficacy of this surface modification of stainless steel. The capacity of cells to adhere to DMF-coated SUS316L stainless steel was compared with machined SUS316L stainless steel in vitro and in vivo. Morphological in vitro response to human osteoblast cell lines was evaluated using scanning electron microscopy. Separate specimens were inserted into the medulla of distal femurs of rabbits for in vivo study. The distal femurs were harvested after 3 months, and were then subjected to push-out test and histomorphometrical analyses. The DMF group exhibited a distinct surface chemical composition, showing higher peaks of titanium compared to the machined stainless steel. The surface of the DMF group had a more distinct porous structure, which showed more extensive coverage with lamellipodia from osteoblasts than the machined surface. In the in vivo test, the DMF group showed better results than the machined group in the push-out test (3.39 vs. 1.35 MPa, respectively, p = 0.001). In the histomorphometric analyses, the mean bone-to-implant contact percentage of the DMF group was about 1.5 times greater than that of the machined group (65.4 ± 7.1% vs. 41.9 ± 5.6%, respectively; p < 0.001). The porous titanium coating on SUS316L stainless steel produced using DMF with 3D printing showed better surface characteristics and biomechanical properties than the machined SUS316L.

Ratcheting-Fatigue Behavior of Harmonic-Structure-Designed SUS316L Stainless Steel

Stainless steels with harmonic-structure design have a great balance of high strength and high ductility. Therefore, it is imperative to investigate their fatigue properties for engineering applications. In the present work, the harmonic-structured SUS316L stainless steels were fabricated by mechanical milling (MM) and subsequent hot isostatic pressing (HIP) process. A series of ratcheting-fatigue tests were performed on the harmonic-structured SUS316L steels under stress-control mode at room temperature. Effects of grain structure and stress-loading conditions on ratcheting behavior and fatigue life were investigated. Results showed that grain size and applied mean stress had a significant influence on ratcheting-strain accumulation and fatigue life. Owing to the ultrafine grained structure, tensile strength of the harmonic-structured SUS316L steels could be enhanced, which restrained the ratcheting-strain accumulation, resulting in a prolonged fatigue life. A higher mean stress caused a faster ratcheting-strain accumulation, which led to the deterioration of fatigue life. Moreover, a modified model based on Smith–Watson–Topper (SWT) criterion predicted the ratcheting-fatigue life of the harmonic-structured SUS316L steels well. Most of the fatigue-life points were located in the 5 times error band.

Influence of Assembly Gap Size on the Structure and Properties of SUS301L Stainless Steel Laser Welded Lap Joint.

The microstructure and properties of laser welding lap joints with different assembly gap sizes are experimentally investigated. The laser weld joint is composed of γ-austenite and δ-ferrite, and the strip ferrite phase is mainly distributed at the austenite grain boundary. The weld metal presents the austenitic-ferritic (AF) solidification mode. When there is a gap between the two plates, a triangular region composed of similar equiaxed crystals can be found, and the size of the cellular crystals in this region decreases significantly. When the assembly gap size increases from 0.1 mm to 0.4 mm, the weld penetration state of the joint changes from full penetration to semi-penetration, and the surface collapse increases. The excessive size of the gap leads to a decrease in the tensile-shear force and fatigue strength of laser welded joints. In order to ensure that the surface morphology and properties of the welded joint meet the quality standard and requirement, the assembly gap should be less than 0.1mm.

Development of New Particle Method Based on MPS and its Applicability for Friction Stir Welding of Dissimilar Joint

Friction stir welding (FSW) is one of the solid-state welding and it has been widely employed for joining aluminum alloys. In addition, as a result of R&amp;D efforts about FSW tool, this method is expected to join the steels and/or various dissimilar materials. In order to examine the thermal and mechanical behavior in FSW, many numerical studies have been conducted and the heat generation behavior near FSW tool is precisely demonstrated by using the moving particle semi-implicit (MPS) method which is one of the particle method. In this research, in order to reduce the computational time, a new parcel method based on MPS is developed and its applicability is examined for simulating the friction stir welded dissimilar joint between V-ally and austenite stainless steel SUS316L. From the serial computational results, it is revealed that the influence of rotational speed on the heat generation during FSW seems to be larger than that of traveling speed. Moreover, the numerical result indicates that the sound dissimilar joint might be fabricated when V-alloy is set to be the retreating side (RS), the FSW tool is inserted in RS and the rotational speed increased appropriately although the two materials have not been joined in this welding condition of FSW experimentally.

Platelet adhesion on commercially pure titanium plates in vitro III: effects of calcium phosphate-blasting on titanium plate biocompatibility

BackgroundPlatelet-rich plasma (PRP) is often used to improve surface biocompatibility. We previously found that platelets rapidly adhere to plain commercially pure titanium (cp-Ti) plates in the absence, but not in the presence, of plasma proteins. To further expand on these findings, in the present study, we switched titanium plates from a plain surface to a rough surface that is blasted with calcium phosphate (CaP) powder and then examined platelet adhesion and activation.MethodsElemental distribution in CaP-blasted cp-Ti plates was analyzed using energy-dispersive X-ray spectroscopy. PRP samples prepared from anticoagulated blood samples of six healthy, non-smoking adult male donors were loaded on CaP-blasted cp-Ti plates for 1 h and fixed for examination of platelet morphology and visualization of PDGF-B and platelet surface markers (CD62P, CD63) using scanning electron microscopy and fluorescence microscopy. Plain SUS316L stainless steel plates used in injection needles were also examined for comparison.ResultsSignificant amounts of calcium and phosphate were detected on the CaP-blasted cp-Ti surface. Platelets rapidly adhered to this surface, leading to higher activation. Platelets also adhered to the plain stainless surface; however, the levels of adhesion and activation were much lower than those observed on the CaP-blasted cp-Ti plate.ConclusionsThe CaP-blasted cp-Ti surface efficiently entraps and activates platelets. Biomolecules released from the activated platelets could be retained by the fibrin matrix on the surface to facilitate regeneration of the surrounding tissues. Thus, PRP immersion could not only eliminate surface air bubbles but also improve the biocompatibility of the implant surface.

Amorphization under fracture surface in hydrogen-charged and low- temperature tensile-tested austenitic stainless steel

ABSTRACT The microstructure just below the fracture surface in hydrogen-charged stable austenitic SUS 316L stainless steel, which was subjected to a low strain rate tensile test at −70°C, was studied by a combination of the focused-ion-beam method and transmission electron microscopy. An amorphous region with a chemical composition almost identical to that of the polycrystalline region was found under the lath-like structure on the fracture surface, although no deterioration of tensile properties by hydrogen appeared. In the amorphous region, band-like regions with wavy contrasts were observed, which were often accompanied by cracks at the boundaries. The presence of the amorphous region with band-like regions implies that amorphization occurred due to high-density vacancies accompanied by agglomerations of excess vacancies in the hydrogen-charged SUS 316L stainless steel that was tensile-tested at low temperatures.

Ultralow rotation speed produces high-quality joint in dissimilar friction welding of Ti–6Al–4V alloy and SUS316L stainless steel

Ultralow rotation speed and high friction pressure were adopted to friction weld Ti–6Al–4V alloy and SUS316L stainless steel. Ultralow rotation speed effectively suppressed the formation of harmful mechanically mixed layers. High friction pressure guaranteed a proper welding temperature and a sufficient SUS316L deformation. A high-quality joint was then successfully fabricated.

Corrosion Behavior of SUS 304L Steel in pH 13 NaOH Solution

In order to investigate the corrosion behavior of SUS 304L steel in alkaline solutions, linear sweep voltammogram measurements were performed in NaOH solutions at pH 12 and 13 at 333 K. Constant potential electrolysis was carried out in an NaOH solution at 333 K at pH 13 from 5 to 20 hours. The surface analysis of the samples before and after the constant potential electrolysis was performed by atomic force microscopy, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The XPS measurements of the samples before the electrolysis showed that Fe and Cr oxide films were formed on the SUS 304L stainless steel surface, and the presence of FeOOH, CrOOH and Ni(OH)2 on the surface was confirmed after the electrolysis. It is suggested that the dissolved metal ions from the SUS 304L surface reacted with OH− and formed a precipitated film on the surface in the alkaline environment.

Effect of Nitrogen Atmosphere on the Mechanical Properties and Microstructure of SUS316L Stainless Steel Additively Manufactured by Selective Laser Melting

Effect of Nitrogen Atmosphere on the Mechanical Properties and Microstructure of SUS316L Stainless Steel Additively Manufactured by Selective Laser Melting

Anti-Bacterial and Anti-Fouling Capabilities of Poly(3,4-Ethylenedioxythiophene) Derivative Nanohybrid Coatings on SUS316L Stainless Steel by Electrochemical Polymerization.

We have successfully fabricated poly(3,4-ethylenedioxythiophene) (PEDOT) derivative nanohybrid coatings on flexible SUS316L stainless steel by electrochemical polymerization, which can offer anti-fouling and anti-bacterial capabilities. PEDOT derivative nanohybrids were prepared from polystyrene sulfonates (PSS) and graphene oxide (GO) incorporated into a conducting polymer of PEDOT. Additionally, the negative charge of the PEDOT/GO substrate was further modified by poly-diallyldimethylammonium chloride (PDDA) to form a positively charged surface. These PEDOT derivative nanohybrid coatings could provide a straightforward means of controlling the surface energy, roughness, and charges with the addition of various derivatives in the electrochemical polymerization and electrostatically absorbed process. The characteristics of the PEDOT derivative nanohybrid coatings were evaluated by Raman spectroscopy, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), water contact angle, and surface potential (zeta potential). The results show that PEDOT/PSS and PEDOT/GO nanohybrid coatings exhibit excellent anti-fouling capability. Only 0.1% of bacteria can be adhered on the surface due to the lower surface roughness and negative charge surface by PEDOT/PSS and PEDOT/GO modification. Furthermore, the anti-bacterial capability (7 mm of inhibition zone) was observed after adding PDDA on the PEDOT/GO substrates, suggesting that the positive charge of the PEDOT/GO/PDDA substrate can effectively kill bacteria (Staphylococcus aureus). Given their anti-fouling and anti-bacterial capabilities, PEDOT derivative nanohybrid coatings have the potential to be applied to biomedical devices such as cardiovascular stents and surgical apparatus.

Deposition of Multicomponent AlTiCrMoN Protective Coatings for Metal Cutting Applications

The high potential of the protective coatings for metal machining applications using the physical vapor deposition (PVD) processes is one to be valued, and will accelerate development of the multicomponent coating design and increase the cutting efficiency. In this study, nanostructured AlTiCrMoN coatings in a multilayered structure were fabricated using cathodic-arc deposition (CAD). Controlling the cathode current of both CrMo and AlTi alloy targets in a nitrogen environment, multilayered AlTiN/CrMoN coatings were deposited. The AlTiN and AlTiN/CrMoN multilayered coatings exhibit a face-centered cubic (fcc) structure with columnar morphologies. The highest hardness of 35.6 ± 1.5 GPa was obtained for the AlTiN coating; however, the H3/E*2 and H/E* values were the lowest (0.124 and 0.059, respectively). The multilayered AlTiN/CrMoN coatings possessed higher H3/E*2 and H/E* values of up to 0.157 and 0.071, respectively. The present study investigated the cutting performance of end mills in the milling of SUS316L stainless steel. The cutting performance was evaluated in terms of cutting length and tool wear. Because of high resistance to adhesive and abrasive wear, the end mills coated with multilayered AlTiN/CrMoN showed less flank wear than monolithic AlTiN. The introduction of CrMoN sublayers improved the cutting tool life of AlTiN.

A low-cycle fatigue life-prediction model for SUS301L stainless steel butt-welded joint with considering ratchetting

According to the existing experimental investigation on the ratchetting-fatigue interaction of SUS301L stainless steel butt-welded joint, a new life-prediction model addressing the important role of ratchetting is developed based on the ductility exhaustion theory (DET) and continuum damage mechanics (CDM). The total ductility damage is assumed to consist of fatigue ductility and ratchetting ductility ones, and the ductility and corresponding damage variables are defined in a strain-based form in the proposed life-prediction model. The proposed model is employed to predict the stress-controlled low-cycle fatigue life of SUS301L stainless steel butt-welded joint based on the local strain in its fusion zone FZ-1 measured directly by using the digital image correlation (DIC) technology, and the predicted results show a good agreement with the experimental ones.

Anti-fouling and anti-coagulation capabilities of PEDOT-biopolymer coating by in-situ electrochemical copolymerization

In this study, 3,4-ethylenedioxythiophene (EDOT), polystyrene sulfonate (PSS), chondroitin sulfate (CHS), and carboxymethyl-hexanoyl chitosan (CHC) nanohybrids were coated on nitrogen plasma pre-treated SUS316L stainless steel using in-situ electrochemically copolymerization. The negatively charged PSS, CHS, and CHC were used to repel the negatively charged proteins, platelets, and cell walls of bacteria (E. coli) to achieve anti-fouling and anti-clotting capabilities. The anti-fouling capabilities of the poly-3,4-ethylenedioxythiophene (PEDOT) derivative coatings had the following order: PEDOT/CHC/CHS > PEDOT/CHS > PEDOT/CHS/PSS > PEDOT/PSS > pristine SUS316L. In particular, with the addition of CHC, the PEDOT/CHC/CHS coating could decrease the adhesion of platelets and bacteria using the functional group (-COOH) of CHC. The blood clotting time (activated partial thromboplastin time) of the PEDOT/CHC/CHS substrates was prolonged to 48 s, compared to the 32 s required for the pristine SUS316L stainless steel, showing the good hemocompatibility. Furthermore, cytotoxicity tests showed that PEDOT and its derivatives exhibited very good biocompatibility. Thus, they could potentially be applied in anti-clotting, anti-fouling, and anti-bacterial biomedical devices such as cardiovascular stents.

Unraveling the Effect of Deformation Temperature on the Mechanical Behavior and Transformation‐Induced Plasticity of the SUS304L Stainless Steel

The behavior of the SUS304L metastable austenitic stainless steel during deformation above and below Md temperature is systematically studied. At temperatures higher than Md, linear temperature‐dependent relationships are observed for tensile strength and elongation; whereas below Md, a sharp increase in these parameters is identified. A pronounced transformation‐induced plasticity (TRIP) effect is observed when the amount of martensite in the necked region becomes significant, resulting in a maximum point in the work‐hardening plot and enhancement of strength–ductility balance.

Spherical particles with and without attached nanoparticles formed by DC-arc spheroidization of irregularly shaped stainless-steel powder

Water-atomized powder of SUS316L stainless steel was spheroidized by DC arc plasma to obtain a spherical powder with high fluidity and high packing density at low cost. This process successfully spheroidized the raw powder and improved the powder characteristics. In the spheroidized powder, fluidity was enhanced by up to 100% versus raw powder; tapped density was likewise increased by up to 50% versus raw powder. We also formed a nanoparticle-modified spherical powder. Spark plasma sintering using spheroidized powders yielded high densities, including a relative density of 99.6% for the compact produced from nanoparticle-modified powder.

Effect of welding parameters on weld formation quality and tensile-shear property of laser welded SUS301L stainless steel lap filet weld

Laser welding of lap-filet joints SUS301L austenitic stainless steel plates were carried out with filler wire. Results showed that the weld zone was composed of columnar austenite and a small amount of δ-ferrite. The effect of feed direction, wire distance (H), laser incident position (L) and laser incident angle on the wire melting mechanism, weld pool geometry, metal transfer modes and heat distribution were studied with the assistance of the high speed camera recording the welding process. Better weld quality was obtained under the circumstances of leading direction, wire distance 0.5mm, laser incident position 0.5mm, and laser incident angle 0̊. The fracture was always located in the weld where the thickness of it was the smallest. There was a linear relationship between the weld width and the smallest weld thickness. The maximum tensile-shear force was 24.46kN. The fracture mode was ductile fracture with fracture surface dimples.

Principle for obtaining high joint quality in dissimilar friction welding of Ti-6Al-4V alloy and SUS316L stainless steel

Ti-6Al-4V alloy (Ti64) and SUS316L stainless steel rods were dissimilarly friction welded. Especially focusing on the detailed observation of interface microstructural evolution during the friction welding (FW), the relationship between the processing conditions, weld interface microstructure, and mechanical properties of the obtained joints were systematically investigated to elucidate the principle for obtaining a high joint quality in the FW of Ti64 and SUS316L. A higher friction pressure produced a lower welding temperature in the FW, hence suppressing the thick intermetallic compound layer formation. However, hard and brittle Ti64/SUS316L mechanically mixed layers generally formed especially at the weld interface periphery due to the high temperature increasing rate, high rotation linear velocity and high outward flow velocity of the Ti64. These harmful layers tended to induce the cracks/voids formation at the weld interfaces hence deteriorating the joints’ mechanical properties. The rotation speed reduction and liquid CO2 cooling during the entire processing decreased the temperature increasing rate, rotation linear velocity and outward flow velocity of the Ti64 at the weld interface periphery. Therefore, they suppressed the formation of the harmful mechanically mixed layers, facilitated the homogeneous and sound interface microstructure generation, and finally produced a high-quality dissimilar joint in the FW of Ti64 and SUS316L.

A novel biofunctionalizing peptide for metallic alloy.

Improving biocompatibility of metallic alloy biomaterials has been of great interest to prevent implant associated-diseases, such as stent thrombosis. Herein a simple and efficient procedure was designed to biofunctionalize a biomaterial surface by isolating a SUS316L stainless steel binding peptide. After three rounds of phage panning procedure, 12 mer peptide (SBP-A; VQHNTKYSVVIR) was identified as SUS316L-binding peptide. The SBP-A peptide formed a stable bond to a SUS316L modified surface and was not toxic to HUVECs. The SBP-A was then used for anti-ICAM antibody modification on SUS316L to construct a vascular endothelial cell-selective surface. The constructed surface dominantly immobilized vascular endothelial cells to smooth muscle cells, demonstrating that the SBP-A enabled simple immobilization of biomolecules without disturbing their active biological function. The SUS316L surface was successfully biofunctionalized using the novel isolated peptide SBP-A, showing its potential as an ideal interface molecule for stent modification. This is the first report of material binding peptide-based optimal surface functionalization to promote endothelialisation. This simple and efficient biofunctionalization procedure is expected to contribute to the development of biocompatible materials.