Properties Of Austenitic Stainless Steel Research Articles

The influence of ultrafine-grained structure on the mechanical properties and biocompatibility of austenitic stainless steels.

In this study, equal-channel angular pressing (ECAP) of austenitic 316L and Cr-Ni-Ti stainless steels was carried out. Effect of ECAP at 400°C on the evolution of the microstructure, mechanical properties, and biocompatibility of these steels was investigated. The biocompatibility of samples with the ultrafine grain structure obtained in the ECAP process did not deteriorate in comparison with an austenitic 316L stainless steel in coarse-grained state. However, this treatment enhances the multipotent mesenchymal stromal/stem cell proliferation by 26% for 316L steel and by 17% for Cr-Ni-Ti stainless steel in comparison with coarse-grained counterparts. At the same time, ECAP contributes to a significant improvement in performance and weight reduction of medical devices, which is especially important for the creation of implanted prostheses for replacement of skeletal defects, due to significant increase in specific strength of steels. The strength properties of austenitic stainless steels were remarkably improved due to the grain refinement and deformation twinning resulted from ECAP at 400°C. After ECAP, the yield strength of 316L and Cr-Ni-Ti stainless steels increased by 4.2 and 2.9 times up to 950 and 900 MPa, and the fatigue limit by 2 and 1.7 times up to 500 and 475 MPa, respectively, comparing to coarse-grained counterparts.

Effect of nitrogen content on microstructure, mechanical properties, and corrosion behaviour of coarse-grained heat-affected zone of nitrogen-containing austenitic stainless steel

AbstractThe microstructures and properties of austenitic stainless steel with varying nitrogen content after welding thermal simulation were investigated. The results indicate that the nitrogen fraction has a considerable influence on the phase composition and properties. Low nitrogen fraction leads to formation of δ-ferrite. After a welding thermal cycle, the number of annealing twins of high nitrogen-containing steel decreases, M23C6 precipitates, and fine M23C6 are observed. For low nitrogen-containing steel, large-size M23C6 and elongated δ-ferrite are formed, which deteriorate the ductility. Meanwhile, equilibrium phase calculations also reveal the inhibiting effect of nitrogen on M23C6 and δ-ferrite. Furthermore, susceptibility to intergranular attack by 10 % oxalic acid solution was detected, and the synergistic effect of coherent twin boundaries, M23C6, and δ-ferrite leads to low resistance to corrosion for low nitrogen-containing steel.

Effect of Microstructure and Mechanical Properties of Austenitic Stainless Steel 1.6mm Butt Welded by Plasma Arc Welding

Plasma Arc Welding (PAW) is more tolerant to joint misalignment than Laser Beam Welding (LBW) at a lower cost [1]. The present study deals with the assessment of mechanical and metallurgical properties of butt welded 1.6 mm thick austenitic stainless steel similar (SS304 and SS304) by using plasma arc welding technique. Similar butt-Welded joints were analyzed by using mechanical (Bend test, Erichsen cup test, tensile test) and metallurgical (Optical macroscopic and microscopic images) characterization methods. The bead width and depth of the butt welded 1.6mm thick butt joined SS304 was analyzed by macroscopic and microscopic images [2]. The Erichsen cup test was conducted on the weld specimens. The indentation was made on the weld specimens. In the similar metal joint the depth of indentation is high, which shows that the similar metal joint has better formability. This makes them appropriate for practicing in the aircraft industries (engine parts), automotive sector (engine-parts and assemblies) chemical processing, food processing, turbine buckets, pumps and valve parts [3]. Keywords: SS304, PAW, Butt weld, Erichsen Cup Test, Microstructure

Elastic Parameters of Paramagnetic Fe–20Cr–20Ni-Based Alloys: A First-Principles Study

The single-crystal and polycrystalline elastic parameters of paramagnetic Fe0.6−xCr0.2Ni0.2Mx (M = Al, Co, Cu, Mo, Nb, Ti, V, and W; 0 ≤ x ≤ 0.08) alloys in the face-centered cubic (fcc) phase were derived by first-principles electronic structure calculations using the exact muffin-tin orbitals method. The disordered local magnetic moment approach was used to model the paramagnetic phase. The theoretical elastic parameters of the present Fe–Cr–Ni-based random alloys agree with the available experimental data. In general, we found that all alloying elements have a significant effect on the elastic properties of Fe–Cr–Ni alloy, and the most significant effect was found for Co. A correlation between the tetragonal shear elastic constant C′ and the structural energy difference ΔE between fcc and bcc lattices was demonstrated. For all alloys, small changes in the Poisson’s ratio were obtained. We investigated the brittle/ductile transitions formulated by the Pugh ratio. We demonstrate that Al, Cu, Mo, Nb, Ti, V, and W dopants enhance the ductility of the Fe–Cr–Ni system, while Co reduces it. The present theoretical data can be used as a starting point for modeling the mechanical properties of austenitic stainless steels at low temperatures.

Effect of bimodal harmonic structure on fatigue properties of austenitic stainless steel under axial loading

Axial fatigue tests and fatigue crack propagation tests were conducted to investigate the fatigue properties of austenitic stainless steel (JIS-SUS304L) with a harmonic structure (HS), which is defined as a coarse-grained structure surrounded by a network of fine grains. Fatigue cracks initiated at the coarse-grained structure in the HS SUS304L, but the fatigue limit was increased by the HS design due to the grain refinement. In contrast, the crack growth rates for the HS material for long cracks were constantly higher, and its threshold stress intensity range were lower compared to a material with a homogenous coarse-grained structure.

레이저 및 TIG 용접된 오스테나이트계 스테인리스강의 기계적 특성에 대한 연구

레이저 및 TIG 용접된 오스테나이트계 스테인리스강의 기계적 특성에 대한 연구

Investigation of wear properties of borided austenitic stainless steel different temperatures and times

Although the corrosion properties of austenitic stainless steels are good, their surface strength is low and their usage areas are limited. Many processes are implemented to improve the surface properties in order to expand the areas of use. For this purpose, in this study, AISI 303 steels are boronized by pack boriding method at 1123 K, 1173 K and 1223 K for 2, 4 and 6 h and the effect of surface coating on the tribological properties of steel by using box boring method. The hardness values were obtained by micro-hardness tester and the phases formed in the layer were determined by XRD method. In the XRD analysis, FeB, Fe2B, CrB and MnB phases were formed on the boride layer. Wear behavior of AISI 303 steel was determined by ball-on-disc abrasion method in dry environment. The hardness value of AISI 303 steel was 240 HV0.05, while the boronizing process resulted in a hardness of 1897 HV0.05. As a result, it was seen that an increase in the thickness and a decrease in the wear rate were observed with an increase in the boriding time and temperature, the decrease in the boriding temperature resulted in a decrease in the thickness of boride layer obtained on the boronized steel.

Investigation of the Effects of Soaking Time on the Properties of Stainless Steel

An investigation was carried out to determine the effect of soaking time during sensitization on the Mechanical properties of Austenitic stainless steels [1]. The selected samples of AISI 316 and AISI 304 were cut into several pieces so that different amount of sensitization was introduced into the different pieces. To induce sensitization, the samples were heated and soaked at 750°C for different time intervals such as 30 minutes, 60 minutes, 180minutes, 300 minutes and 600 minutes followed by water quenching. The resultant samples were tested for Tensile strength, Micro hardness and Macro hardness. It was concluded from the results obtained that the macro and micro hardness of AISI 316 and AISI 304 decreases with increase in soaking time at a constant soaking temperature., However, the macro hardness of AISI 304 decreases more than AISI 316 with increase in soaking time at specified soaking temperature. It was similarly concluded that the tensile strengths AISI 316 and AISI 304 decreases with increase in soaking time at a constant soaking temperature.

Crystal Plasticity Simulation on Effect of Heterogeneous-nanostructure Induced by Severe Cold-rolling on Mechanical Properties of Austenitic Stainless Steel

Severe plastic deformation has attracted interests as one of the breakthrough procedures to improve various properties of metals and alloys. Recently, it has been revealed that heavy cold rolling of some kinds of austenitic stainless steels can cause ultrafine-grained structure comparable with those achieved by severe plastic deformation. Coarse initial grains were fragmented by deformation induced microstructure to develop heterogeneous nanostructure. Tensile strength of heterogeneous-nanostructured stainless steel exceeds 2 GPa. It is considered that high strength of heterogeneous-nanostructured metals is attributed to such peculiar microstructure with dispersed “eye-shaped twin domains”. In this study, microstructural mechanisms and factors which contribute to macroscopic strength of heterogeneous-nanostructured austenitic stainless steel were evaluated on the basis of multiscale crystal plasticity simulation. Microstructure of heavily cold-rolled SUS316LN austenitic stainless steel was investigated by transmission electron microscopy, and stress-strain curves were attained by tensile tests. It was observed that microstructure of SUS316LN manufactured by 92% cold rolling was composed of deformation nano-twins, shear bands, and lamella structure. Evaluation of mechanical properties of heterogeneous-nanostructured SUS316LN was conducted using crystal plasticity finite element simulation considering microstructural information, such as dislocation density, crystal orientation, shape of grains, and dislocation sources. Information of microstructure obtained by electron backscatter diffraction, e.g. geometry of heterogeneous nanostructures and crystal orientation, were introduced to computational models for multiscale crystal plasticity simulation. It was revealed that deformation behavior depends on the tensile direction and the strength increases with the increase of volume fraction of twin domains as well as nano-twin and lamellar inter-spacings.

Anisotropy of the tensile properties in austenitic stainless steel obtained by wire-feed electron beam additive growth

Anisotropy of the tensile properties in austenitic stainless steel obtained by wire-feed electron beam additive growth

The influence of prior deformation on phase composition and strength properties of austenitic stainless steel in ion-plasma treatment

The influence of prior deformation on phase composition and strength properties of austenitic stainless steel in ion-plasma treatment

Deformation Properties of Austenitic Stainless Steels with Different Stacking Fault Energies

In FCC metals a single parameter – stacking fault energy (SFE) – can help to predict the expectable way of deformation such as martensitic deformation, deformation twinning or pure dislocation glide. At low SFE one can expect the perfect dislocations to dissociate into partial dislocations, but at high SFE this separation is more restricted. The role of the magnitude of the stacking fault energy on the deformation microstructures and tensile behaviour of different austenitic steels have been investigated using uniaxial tensile testing and electron backscatter diffraction (EBSD). The SFE was determined by using quantum mechanical first-principles approach. By using plasticity models we make an attempt to explain and interpret the different strain hardening behaviour of stainless steels with different stacking fault energies.

An overview of the recurrent failures of duplex stainless steels

Abstract The favourable combination of mechanical and corrosion properties of ferritic-austenitic duplex stainless steels (DSSs) makes this class of materials widely employed in many industries (e.g. petrochemical, nuclear, pulp and paper). Despite their wide and growing usage, the DSS components might be subjected to various types of mechanical and environmentally induced failures during their life cycle, especially when the component is exposed to temperatures in the range of 300 to 900 °C, which might promote the precipitation of stable and deleterious phases. For instance, the precipitation of sigma, alpha-prime and M23C6 phases - the latter more often observed in high carbon DSS – might induce the premature failure of DSS components due to the mechanical embrittlement and the sensitization of the microstructure during thermal exposure (either in processing, such as welding, or in service). Additionally, the ferrite phase features a ductile-to-brittle temperature, which defines the lower service temperature of DSS components. In this sense, the main properties of DSSs will be compared with the properties of austenitic stainless steels (ASSs) and ferritic stainless steels (FSSs) to provide the reader a broader view about boundary conditions for the selection and use of DSSs. The main phase transformations and microstructures of the DSSs will be concisely presented and microstructural, fractographic and crack propagation characterization of selected in-service failures will illustrate the role of these stable and deleterious phases on the life of DSS components.

Proton irradiation for radiation-induced changes in microstructures and mechanical properties of austenitic stainless steel

We report on microstructural and mechanical property changes as a function of radiation damage value in proton-irradiated austenitic stainless steel by means of advanced characterization techniques. The microstructural changes in proton-irradiated austenitic stainless steel were analyzed by transmission electron microscopy for observation of radiation-induced defects as well as the measurement of the chemical composition at grain boundaries. The radiation hardening after the proton irradiation was characterized by nano indentation for changes in hardness profiles with radiation damage.Various transition points for microstructural and mechanical property changes under proton irradiation are analyzed via material characterization of proton-irradiated austenitic stainless steels. The saturation is expected to occur at approximately 10 displacements per atom (dpa) for the radiation-induced segregation of Cr, Ni, and P and approximately 2.5 dpa for radiation hardening. The cavity formation is observed to occur at hydrogen concentration levels greater than 5E5 atomic parts per million (appm) H. It is also found that the transition from black dot to Frank loop happened above approximately 1 dpa.Profiles of radiation-induced segregation and radiation hardening as a function of dpa can be extended to the high irradiation condition, and can be compared with experimental data for neutron irradiation-induced segregation and radiation hardening. The radiation-induced segregation after the proton irradiation at 360 °C are in good agreement with that after neutron irradiation. On the other hand, it is observed that the evolution of radiation-induced defects and the corresponding radiation hardening exhibit sooner, that appears to be because of the dose rate effect.

Influence of Work‐Hardening and Lower Temperatures on the Yield Stress of Austenitic Stainless Steel X2CrNi18‐10 under Combined Tension‐Torsion Loading

This study investigates the impact of work‐hardening and lower temperatures on the mechanical properties of austenitic stainless steel X2CrNi18‐10 under multiaxial stress. For this purpose, the yield behavior of hollow tubular specimens under combined torsion‐tension loading is examined using a servo‐hydraulic testing system MTS809.10S. Yield points are determined for different tension‐to‐torsion ratios using 1) solution‐annealed specimens tested at room temperature, 2) pre‐strained specimens with 3.6% α’‐martensite tested at room temperature, and 3) solution‐annealed specimens tested at −20 °C. Experimental results show that the yield stresses of the solution‐annealed material at room temperature and at −20 °C can be reasonably approximated using the von Mises and the isotropic Hosford yield hypothesis. Contrary, the yield stresses of the work‐hardened material cannot be fitted with isotropic yield hypotheses because the required torsional stress component to induce plastic deformation is much higher than suggested in those criteria. This effect is mainly attributed to the strain hardening behavior of the X2CrNi18‐10, showing a comparatively high rate of work‐hardening especially at low strains. A suitable approach for fitting the yield points of the work‐hardened material is found with the anisotropic yield hypothesis according to Hosford.

Excellent mechanical and corrosion properties of austenitic stainless steel with a unique crystallographic lamellar microstructure via selective laser melting

We first developed a unique “crystallographic lamellar microstructure” (CLM), in which two differently oriented grains appear alternately, in a 316L stainless steel specimen via selective laser melting technology. The CLM was composed of major 〈011〉 grains and minor 〈001〉 grains aligned along the build direction, which stemmed from vertical and approximately ±45° inclined columnar cells formed in the central and side parts of melt-pools, respectively. The development of CLM was found to largely improve the material properties via the strengthening of the product, simultaneously showing superior corrosion resistance to commercially obtained specimens.

Effect of Cold Deformation on Microstructures and Mechanical Properties of Austenitic Stainless Steel

In this paper, the effect of cold deformation on the microstructures and mechanical properties of 316LN austenitic stainless steel (ASS) was investigated. The results indicated that the content of martensite increased as the cold rolling reduction also increased. Meanwhile, the density of the grain boundary in the untransformed austenite structure of CR samples increased as the cold reduction increased from 10% to 40%, leading to a decreased size of the untransformed austenite structure. These two factors contribute to the improvement of strength and the decrease of ductility. High yield strengths (780–968 MPa) with reasonable elongations (30.8–27.4%) were achieved through 20–30% cold rolling. The 10–30% cold-rolled (CR) samples with good ductility had a good strain hardening ability, exhibiting a three-stage strain hardening behavior.

Secondary Phases Quantification and Fracture Toughness at Cryogenic Temperature of Austenitic Stainless Steel Welds for High-Field Superconducting Magnets

The ITER magnet system is based on the “cable-in-conduit” conductor concept, which consists of various types of stainless steel jackets filled with superconducting strands. The jackets provide high strength and fracture toughness to counteract the high stress imposed by, amongst others, electromagnetic loads at cryogenic temperature. Material properties of austenitic stainless steel at cryogenic temperature are known to some extent, but only partial information is available for their welds, particularly in combination with weld fillers envisaged for cryogenic service. When a full inspection of the welded components is not possible, it becomes of special interest an assessment of its fracture toughness under close-to-service conditions if a fracture mechanics' design approach is to be adopted. In absence of defects, brittle secondary phases are generally held responsible of the loss of ductility and toughness which is to be expected after postweld heat treatments. Their quantification becomes thus essential in order to explain the negative impact in fracture toughness after unavoidable thermal treatments. This paper investigates fracture toughness behavior at 7 K of AISI 316L and AISI 316LN tungsten inert gas welds using two fillers adapted to cryogenic service, EN 1.4453 and JK2LB. Additionally, the effect of such an aforementioned heat treatment, here the Nb 3Sn reaction heat treatment (650° for 200 h) on fracture toughness of the welds is evaluated. A correlation between the evolution of properties and the quantity of secondary phases as a result of the above treatment is provided.

Comparison of magnetic properties of austenitic stainless steel after ion irradiation

Abstract Specimens of austenitic stainless steel (ASS) were irradiated with H, Fe and Xe ions at room temperature. The vibrating sample magnetometer (VSM) and grazing incidence X-ray diffraction (GIXRD) were used to analyze the magnetic properties and martensite formation. The magnetic hysteresis loops indicated that higher irradiation damage causes more significant magnetization phenomenon. Under the same damage level, Xe irradiation causes the most significant magnetization, Fe irradiation is the second, and H irradiation is the least. A similar martensite amount variation with irradiation can be obtained. The coercivity Hc increases first to 2 dpa and then decreases continuously with irradiation damage for Xe irradiation. At the same damage lever, H irradiation causes a largest Hc and Xe irradiation causes a minimal one.

Microstructure and Mechanical Properties of Austenitic Stainless Steels after Dynamic and Post‐Dynamic Recrystallization Treatment

The effects of dynamic and post‐dynamic recrystallization (DRX and post‐DRX) on the microstructure and mechanical properties of austenitic stainless steels are critically reviewed. Particularly, the paper is focused on the grain refinement and strengthening by large strain deformation including severe plastic deformation conditions. The DRX and post‐DRX microstructures are considered with close relation to the operative recrystallization mechanisms. Specific emphasis is placed upon two recrystallization mechanisms, that is, discontinuous and continuous, and their dependence on the deformation/annealing conditions. The relationships between DRX microstructures and processing conditions are summarized and their effect on post‐DRX behavior is clarified. The structural strengthening mechanisms including the grain size and the dislocation density are elaborated.