Austenitic Stainless Steel Wire Research Articles

Microstructure and Mechanical Property Stability of Wire Arc Directed Energy Deposition Austenitic Stainless Steels During Thermal Aging at 650°C

Austenitic stainless steels are used in power generation components subjected to elevated temperatures over long service lives. Replacing these components can involve lengthy lead times and deteriorate the robustness of the energy infrastructure. Wire arc directed energy deposition (WA-DED) has the potential to enable rapid manufacturing of replacement parts, but the long-term stability of microstructures and mechanical properties produced by WA-DED is not well understood. In this work, we explore the influence of aging at 650°C for 1000 h on the formation of embrittling phases, such as sigma (σ), in the commercially available austenitic stainless steel wire feedstocks 316L, 316LSi, 316H and 16-8-2. All WA-DED samples formed secondary phases at grain boundaries (likely σ, possibly other phases as well), but these phases caused negligible changes in tensile properties in 316L, 316LSi and 316H. Samples of 16-8-2 formed significant amounts of ferrite and/or martensite after aging, which increased tensile strength but reduced ductility when tested at room temperature. This work demonstrates the need to design feedstock compositions that are stable with respect to ferrite and/or martensite formation, in addition to phases typically associated with embrittlement, to ensure microstructure and mechanical property stability for high-temperature applications with long service lives.

Hydrogen embrittlement characteristics in cold-drawn high-strength stainless steel wires

Hydrogen uptake and embrittlement characteristics of a cold-drawn austenitic stainless steel wire were investigated. Slow strain rate testing and fracture surface analysis were applied to determine the hydrogen embrittlement resistance, providing an apparent decrease in resistance to hydrogen embrittlement for a 50% degree of cold deformation. The hydrogen content was assessed by thermal desorption and laser-induced breakdown spectroscopy establishing a correlation between the total absorbed hydrogen and the intensity of near-surface hydrogen. The sub-surface hydrogen content of the hot-rolled specimen was determined to be 791 wt.ppm.

Temperature-Dependent Deformation Behavior of “γ-austenite/δ-ferrite” Composite Obtained through Electron Beam Additive Manufacturing with Austenitic Stainless-Steel Wire

Temperature dependence of tensile deformation behavior and mechanical properties (yield strength, ultimate tensile strength, and an elongation-to-failure) of the dual-phase (γ-austenite/δ-ferrite) specimens, obtained through electron-beam additive manufacturing, has been explored for the first time in a wide temperature range T = (77–300) K. The dual-phase structures with a dendritic morphology of δ-ferrite (γ + 14%δ) and with a coarse globular δ-phase (γ + 6%δ) are typical of the as-built specimens and those subjected to a post-production solid–solution treatment, respectively. In material with lower δ-ferrite content, the lower values of the yield strength in the whole temperature range and the higher elongation of the specimens at T > 250 K have been revealed. Tensile strength and stages of plastic flow of the materials do not depend on the δ-ferrite fraction and its morphology, but the characteristics of strain-induced γ→α′ and γ→ε→α′ martensitic transformations and strain-hardening values are different for two types of the specimens. A new approach has been applied for the analysis of deformation behavior of additively fabricated Cr-Ni steels. Mechanical properties and plastic deformation of the dual-phase (γ + δ) steels produced through electron beam additive manufacturing have been described from the point of view of composite materials. Both types of the δ-ferrite inclusions, dendritic lamellae and globular coarse particles, change the stress distribution in the bulk of the materials during tensile testing, assist the defect accumulation and partially suppress strain-induced martensitic transformation.

Effect of welding parameters on the mechanical and metallurgical properties of armor steel weldment

The effect of welding parameters on the mechanical and metallurgical properties of armor steel weldment was studied using gas tungsten arc welding process with two filler wires: carbon steel and austenitic stainless-steel filler wires (AWS A5.18 ER 70S-6 and AWS A5.9 ER 307, respectively). The joint configurations were mainly single V and single bevel grooves. Using both AWS A5.18 ER70S-6 carbon steel filler wire and AWS A5.9 ER307, austenitic filler wire for the two joints passed the required tensile strength by the military standard. The joints successfully regained the base metal hardness at a distance of less than 15 mm. The ultimate tensile strength of the joints welded in a single bevel groove is 906 MPa which is higher than the joints welded using a single V groove is 865 MPa. This could be attributed to the increase in dilution percentage with the single bevel joints. Both single V joint and single bevel joints passed the required Charpy V-notch impact test whether using both carbon and stainless-steel wires. The effect of heat input and cooling rate on the mechanical and microstructure of welded joints was studied. The reduction of heat input caused a narrow HAZ with a small reduction in its hardness values with much reduction in the width of softening microstructure zone. SEM observations show that the base metal has a martensitic structure, but the weld metal microstructures depend on the filler: carbon steel or austenitic steel types. Using a single bevel groove with an austenitic steel filler metal, the weld metal shows a martensitic/austenitic microstructure by SEM observation, and this was verified by the Schaeffler diagram which showed a high dilution percentage (about 35% dilution). This resulted in a significant increase in joint strength and a higher weld metal impact resistance.

Evaluating Suitable Weld Condition to Obtain Enlarged Bead Width of 316 Stainless Steel Towards Weld Cladding

Usually bead-on-plate welding is performed to standardize process parameters before cladding. Selection of appropriate process parameters plays a vital role for achieving good weld bead geometry. In this experimental investigation, Metal Active Gas Welding is used with 316 austenitic stainless steel wire electrode. An experimental design for Response Surface Methodology named, Box-Behnken (Three Variable) design is adopted for determining the experimental runs. Heat input of 0.6kJ/mm and higher than this can be used to obtain desirable bead-on-plate welding that may also be recommended for weld cladding for this substrate-filler material combine.

Effect of drawing and annealing on the microstructure and mechanical properties of 304 austenitic stainless steel wire

Plastic deformation at room temperature, and the proceeding heat treatments, are important processes for optimizing the microstructure and mechanical properties of austenitic stainless steel. The microstructure and mechanical properties of cold-drawn 304 austenitic stainless steel wire were investigated after annealing at 700 °C and 800 °C, with different times (20, 40 and 60 min) and drawing strain (0.4, 1.0 and 1.5). Electron backscattered diffraction (EBSD) techniques, transmission electron microscope (TEM) analysis, differential scanning calorimeter (DSC) and tensile tests were performed in order to study the microstructure evolution and mechanical properties during different annealing processes for the 304 austenitic stainless steel wire. The results showed that the quantity of α′ martensite and dislocations increased with an increase in the strain, which means that, while the ultimate tensile strength of the cold-drawn wires elevated, the elongation reduced. The mechanical properties of stainless steel wires also varied with the evolution of martensite transformation characteristics, density of stacking fault, dislocation and twin, as well as the recrystallization degree under various annealing conditions. The recrystallization temperature of steel wire was mainly determined by the magnitude of the strain, while the martensite reversal temperature was determined by the stacking fault energy and the deformation value. The temperature of recrystallization and martensite reverse in steel wire decreased with the increment of the strain. The balance of tensile strength and elongation of steel wire can be obtained by adopting the proper annealing process combined with cold-drawing deformation. In this paper, we showed that a good combination of strength and elongation in 304 austenitic stainless steel can be obtained with a strain of 1.5 annealed at 800 °C for 20 min.

Methodical procedure of virtual manufacturing for analysing WAAM distortion along with experimental verification

This paper deals with a principal development of virtual manufacturing (VM) procedure to predict substrate distortion induced by Wire Arc Additive Manufacturing (WAAM) process. In this procedure, a hollow shape is designed in a thin-walled form made of stainless steel. The procedure starts with geometrical modelling of WAAM component consisting of twenty-five deposited layers with austenitic stainless-steel wire SS316L as feedstock and SS304 as substrate material. The hollow shape is modelled based on simplified rectangular mesh geometry with identical specimen dimensions during the experiment. Material model to be defined can be retrieved directly from a database or by conducting a basic experiment to obtain the evolution of material composition, characterized using Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray (EDX) analysis, and generated using advanced modelling software JMATPRO for creating new properties including the flow curves. Further, a coupled thermomechanical solution is adopted, including phase-change phenomena defined in latent heat, whereby temperature history due to successive layer deposition is simulated by coupling the heat transfer and mechanical analysis. Transient thermal distribution is calibrated from an experiment obtained from thermocouple analysis at two reference measurement locations. New heat transfer coefficients are to be adjusted to reflect actual temperature change. As the following procedure prior to simulation execution, a sensitivity analysis was conducted to find the optimal number of elements or mesh size towards temperature distribution. The last procedure executes the thermomechanical numerical simulation and analysis the post-processing results. Based on all aspects in VM procedures and boundary conditions, WAAM distortion is verified using a robotic welding system equipped with a pulsed power source. The experimental substrate distortion is measured at various points before and after the process. It can be concluded based on the adjusted model and experimental verification that using nonlinear numerical computation, the prediction of substrate distortion with evolved material property of component yields far better result which has the relative error less than 11% in a comparison to database material which has 22%, almost doubled the inaccuracy.

Effect of heat treatment on the mechanical properties of stainless steel wire

The article is devoted to the study of the mechanical properties of austenitic stainless steel wire with a diameter of 1 mm after heat treatment. Mechanical properties were tested: strength and ductility of hardened and normalized stainless steel. According to the test results, it was found that heat treatment of steel allows obtaining maximum plasticity, while low strength, thus, it seems possible to use this heat treatment as a preparatory operation for the subsequent electric arc spraying of the wire and obtaining a spherical powder.

Droplet transfer behavior and weld formation of gas metal arc welding for high nitrogen austenitic stainless steel

Abstract High nitrogen austenitic stainless steel (HNASS) wire with 0.78 wt.% nitrogen content was used for gas metal arc welding (GMAW) test. The characteristics of droplet transfer and weld formation in different welding parameters were investigated. There were three typical metal transfer modes in GMAW of HNASS, namely in terms of stable short circuit transfer, unstable short circuit transfer and spray transfer. With wire feed speed (WFS) of 3 m/min∼8 m/min and moderate arc voltage, the droplet transfer was stable short-circuiting transition mode. The transfer period and waveform of electrical parameters were regular and the weld formation was satisfactory with few spatters. With the increasing of arc voltage or WFS, the droplet grew up to abnormal large size due to the expansion of supersaturated nitrogen. The electric parameters were more disordered and the metal transfer became unstable with spatter. When wire feed speed was over 10 m/min with high arc voltage, the droplet transfer became spray transfer accompanied by numerous welding fumes. The weld formation of HNASS for unstable short circuit and spray transfer mode was inferior with serious spatters.

Multiscale analysis of mechanical behavior of multilayer steel structures fabricated by wire and arc additive manufacturing

ABSTRACT The mechanical behavior of multilayer steel structures fabricated via wire and arc additive manufacturing (WAAM) has been investigated from the multiscale perspective. The multimaterial WAAM approach can control a heterogeneous structure and improve its mechanical properties. In this study, WAAM equipment based on plasma arc welding was used to fabricate two pairs of single- and duplex-phase multilayer steel structures using austenitic and martensitic stainless steel wires. The heterogeneity of these structures was characterized through micro-indentation tests. In addition, tensile tests of the multilayer structures were conducted to evaluate the effect of heterogeneity on macroscopic material properties. The deformation behavior of the heterogeneous multilayer steel structures was investigated by comparison with the finite element simulations of tensile tests in which the finite element models were created according to the estimated local elastoplastic properties from the results of micro-indentation tests. The micro-indentation tests revealed that the local mechanical properties significantly change during WAAM in cases where martensitic stainless steel wire was used. Additionally, strain-induced transformation plasticity was particularly observed in duplex cases, caused by the metastable austenite phase formed according to the thermal history and through the mixing of alloy elements. Thus, the heterogeneity of the multilayer steel structures became more complicated than its design, and consequently, its macroscopic mechanical properties exceeded the upper and lower bounds of a micromechanic estimation. The results show the potential to fabricate a structure having a unique mechanical behavior via the multimaterial WAAM approach.

Practical Investigation of FSS (AISI 430) Weldments Welded by Pulse MIG Welding Process

Ferritic stainless steels are iron-chromium alloys having chromium content usually in the range of 10.5–27%. In these steels the predominant metallurgical phase present is ferrite. These steels are Fe-Cr-C alloys with sufficient chromium or chromium plus other ferrite stabilizer, such as aluminium, niobium, molybdenum, titanium, used to inhibit the formation of austenite phase on heating. Ferritic stainless steel (FSS) is generally considered to have poor weldability when compared to austenitic stainless steel (ASS) but has recently drawn greater attention owing to their lower costs and better resistance to stress corrosion resistance than austenitic stainless steel. Ferritic stainless steels have been widely used in vessels, vehicles, household appliances, kitchen equipments and building decoration because of its excellent stress corrosion and spot corrosion resistance addition to good strength. Because it does not contain nickel, it is a cheaper alternative of austenitic stainless steel. In this work weldments of FSS welded by pulse MIG welding using argon as a shielding gas were investigated. The austenitic stainless steel (ER309L) and ferritic stainless steel (ER430) electrode wires were used to prepare the weldments. To obtain a good welded joint the welding process parameters were experimentally optimised. The microstructures and mechanical properties of the prepared weldments were investigated. In the weldment welded by austenitic stainless steel electrode wire dendritic austenitic phase was observed in the weld metal zone. In heat affected zone intragranular carbide precipitation and grain boundary martensite were observed. In case of weldments welded by ferritic stainless steel electrode wire coarse grains were formed in weld metal zone and heat affected zone. Grain boundary martensite, ferrite and intragranular carbide precipitation were found in weld metal zone and heat affected zone. Impact strength of the weldments welded by austenitic stainless steel electrode wire was found higher due to formation of austenite phase in the weld metal zone. Impact strength of the weldments welded by ferritic stainless steel electrode wire was found very low due to formation of coarse grain and martensite in the weld metal zone. The ultimate tensile strength and percentage elongation of the weldments welded by austenitic stainless steel electrode wire were found higher than the weldments welded by ferritic stainless steel electrode wire. Hence weldments of ferritic stainless steel having superior mechanical properties will be obtained by using austenitic stainless steel electrode wire. During the tensile test the specimens were broken outside the welded joint (in base metal) which confirms the good quality of the joints

A Constitutive Model of Plate-Like Entangled Metallic Wire Material in Wide Temperature Range.

Entangled metallic wire material (EMWM) is a kind of porous damping material. To promote the engineering application of EMWM, it is necessary to establish the constitutive model of EMWM to estimate its mechanical properties. In this paper, a series of quasi-static compression experiments for plate-like EMWM specimens made of austenitic stainless steel wire (06Cr19Ni10) with different densities were carried out in the temperature range of 20–500 °C. It was found that the stiffness of the plate-like EMWM would increase with the increases in the ambient temperature. The non-linear characteristics of the force–displacement curve of the plate-like EMWM would be weakened. Taking the spatial structural characteristics of the plate-like EMWM and the influence of the thermal expansion of the structure into account, a new constitutive model for plate-like EMWM was presented by the combination of the Johnson–Cook model and the Sherwood–Frost constitutive framework model. The accuracy of the model was verified by the experimental data under different temperatures. The results show that the calculated results of the model are consistent with the experimental results. This model can provide an effective theoretical basis for predicting the mechanical properties of plate-like EMWM and guiding its design.

低変態温度溶接材料を用いた溶融金属積層造形材の変形低減法に関する基礎的検討

Current work deals with investigation of the effect of the use of low transformation temperature welding wire (LTT welding wire) on distortion reduction of parts made by wire and arc additive manufacturing technique (WAAM). LTT welding wire and SUS308L wire, which was austenitic stainless steel wire, were used for making WAAM test pieces. Distortion of base plates of test pieces were evaluated by 3D non-contact coordinate measurement system. As a result, longitudinal bending distortion of the base plates of test pieces in which LTT welding wire was partially or fully used was smaller than those of the test piece which was made only by SUS308L wire. Especially, longitudinal bending distortion of the base plates of test pieces which was made only by LTT welding wire was reduced drastically from those of the test piece which was made only by SUS308L wire. However, angular distortion of the base plates were not reduced drastically even if the test piece was made only by LTT welding wire. The difference of the reduction effect of the use of LTT welding wire was discussed by considering the position of neutral plane of each distortion mode.

Hardfacing of 3.5% Chromium Cast Steel by Flux Cored Wire Arc Welding Process

Hardfacing weld is a technique which mainly improves and extends the useful life of engineering components. The purpose of this research is to improve welding procedure for one layer and three layers hardfacing of 3.5% Chromium cast steel and to study wear behavior of hardfacing layers. Flux Cored Wire Arc Welding (FCAW) process has been used as a welding process of this research by choosing austenitic stainless steel and martensitic hardfacing wire to weld the buffer and hardfacing layer respectively. Preheating was also used in this study. Abrasive wear test of hardfacing deposit were conducted in accordance with procedure “A” standard of ASTM G65. In addition, microstructures and macrostructure of worn surface deposits were analyzed by using optical microscope. These results showed that there is no crack and defect in the Heat Affected Zone (HAZ) and other regions. The hardness of preheating sample in HAZ regions was lower than the ones without preheating. Therefore, preheating samples should be done before welding. The abrasive wear resistance of three layers hardfacing deposit was better than one layer hardfacing deposit because one layer hardfacing deposit was more diluted from buffer layer than three layers hardfacing deposit. Moreover, weight loss of one hardfacing layer was also higher than three layers.

Surface modification of an austenitic stainless steel wire by a multi-pulse treatment with a high-power electric current

The skin effect caused by high-power electric pulses can be used for modification of the surface microstructure in metallic materials. The electric current pulses of high amplitude and short rapid surface heating followed by melting and rapid solidification due to heat exchange with the bulk. New high-current multi-pulse equipment was engineered and used for the surface modification of a stainless steel. The microstructure was investigated by transmission electron microscopy as a function of the distance from the surface. Rapid surface heating and high cooling rate caused drastic changes in the initial austenitic structure, amorphization of the surface layer and pronounced mechanical twinning in the subsurface region.

Effects of nanostructured, diamondlike, carbon coating and nitrocarburizing on the frictional properties and biocompatibility of orthodontic stainless steel wires.

To evaluate and compare the effects of nanostructured, diamondlike, carbon (DLC) coating and nitrocarburizing on the frictional properties and biocompatibility of orthodontic stainless steel archwires. Plasma-enhanced chemical vapor deposition technology was applied to coat DLC films onto the surface of austenitic stainless steel wires, and salt-bath nitrocarburizing technology was employed to achieve surface hardening of other wires. Surface and cross-sectional characteristics, microhardness, modulus of elasticity, friction resistance, corrosion resistance, and cell toxicity of the modified and control wires were analyzed. The surfaces of the DLC-coated and nitrocarburized wires were both smooth and even. Compared with the control, the DLC-coated wires were increased in surface hardness 1.46 times, decreased in elastic modulus, reduced in kinetic friction coefficient by 40.71%, and decreased in corrosion current density by two orders of magnitude. The nitrocarburized wire was increased in surface hardness 2.39 times, exhibited an unchanged elastic modulus, demonstrated a decrease in maximum static friction force of 22.2%, and rose in corrosion current density two orders of magnitude. Cytotoxicity tests revealed no significant toxicity associated with the modified wires. DLC coating and nitrocarburizing significantly improved the surface hardness of the wires, reduced friction, and exhibited good biocompatibility. The nanostructured DLC coating provided excellent corrosion resistance and good elasticity, and while the nitrocarburizing technique substantially improved frictional properties, it reduced the corrosion resistance of the stainless steel wires to a lesser extent.

Research on the properties of TIG welded joints of high nitrogen nickel-free austenitic stainless steel and welding wire

TIG welding tests were carried out on high nitrogen nickel-free austenitic stainless steel by solid solution treatment,with three kinds of self-developed high nitrogen alloyed flux cored wires obtained. The results show the microstructure of the welded joints is austenite in dendritic crystalwith strong corrosive resistance. The grains in HAZ zone hardly grew, and the bonding were perfect between weld and base metal. Furthermore, no obvious nitrogen pores are found in welds and fusion zone. Connector Rm of Mo–N Wire and Mo–Nb–N flux cored wire is higher than the base metal to 983 MPa.

Effect of Strain Induced Martensite for 304M2 Austenitic Stainless Steel Wire

The impact of deformation and strain rate on the strain induced martensite (SIM) from 304M2 austenitic stainless steel was studied by using X-Ray diffraction, transmission electron microscopy. The results indicate that 304M2 is easy to have SIM because of the chemical component and microstructural characteristic. The amount of SIM has great relationship with the deformation and strain rate. It is found that the amount of SIM is reduced during high speed deformation. The obvious SIM can be observed with higher deformation, but the growth rate slows down. When the deformation rates are 8.3%, 55.0% and 67.3%, the contents of martensite are 6.55%, 15.35% and 16.21%, respectively. Compared with the slow stretching, the quick stretching leads to less martensite transformation. Moreover, the elongation of the specimens decreases. At the stable deformation stage, the temperature increases are 72.8 and 91.9℃, respectively, when the strain rates are 2×10-2s-1 and 5×10-4s-1. Therefore, the martensitic transformation and the deformation behavior of the austenitic stainless are affected by heating.

Effect of Different Deformation on Microstructures and Properties in 304HC Austenitic Stainless Steel Wire

Two different components of Φ5.5mm 304HC stainless steel wires were drawn at room temperature. After the drawing tests, hard wires of Φ4.5mm, Φ3.8mm and Φ3.45mm were obtained. During the process of drawing, the stacking fault energy of the metastable austenitic stainless steel was low, which have caused strain-induced martensitic transformation. By XRD, TEM, martensitic volume fraction measurement, etc., the results show that the strain-induced martensitic transformations of the two different components were different significantly. When the deformation amount was controlled at 33% or less, a small amount of γ → α ' martensitic transformations of two steels has occurred. While the deformation arrived at 52% or more, a large amount of γ → α ' martensitic transformation has occurred. The stainless steel which has a higher Cu content will have a lower martensite content, which results from the reason that Cu has a strong inhibitory effect on the martensitic formation. In addition, the martensitic transformation can also influence properties. With the accumulation of strain, deformation mainly occurs in martensitic structure, which reduces the plasticity.

Laser welding of NiTi shape memory alloy: Comparison of the similar and dissimilar joints to AISI 304 stainless steel

The unique properties of NiTi alloy, such as its shape memory effect, super-elasticity and biocompatibility, make it ideal material for various applications such as aerospace, micro-electronics and medical device. In order to meet the requirement of increasing applications, great attention has been given to joining of this material to itself and to other materials during past few years. Laser welding has been known as a suitable joining technique for NiTi shape memory alloy. Hence, in this work, a comparative study on laser welding of NiTi wire to itself and to AISI 304 austenitic stainless steel wire has been made. Microstructures, mechanical properties and fracture morphologies of the laser joints were investigated using optical microscopy, scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction analysis (XRD), Vickers microhardness (HV0.2) and tensile testing techniques. The results showed that the NiTi–NiTi laser joint reached about 63% of the ultimate tensile strength of the as-received NiTi wire (i.e. 835 MPa) with rupture strain of about 16%. This joint also enabled the possibility to benefit from the pseudo-elastic properties of the NiTi component. However, tensile strength and ductility decreased significantly after dissimilar laser welding of NiTi to stainless steel due to the formation of brittle intermetallic compounds in the weld zone during laser welding. Therefore, a suitable modification process is required for improvement of the joint properties of the dissimilar welded wires.