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Austenitic Stainless Steel (austenitic + stainless_steel)

Distribution by Scientific Domains

Polymers and Materials Science	66%
Chemistry	9%

Selected Abstracts

Phase Reversion-Induced Nanograined/Ultrafine-Grained Structures in Austenitic Stainless Steel and their Significance in Modulating Cellular Response: Biochemical and Morphological Study with Fibroblasts,

ADVANCED ENGINEERING MATERIALS, Issue 12 2009
R. Devesh Kumar Misra
Materials science, engineering, and biological sciences have been combined to improve the tissue compatibility of medical devices. In this regard, nano/ultrafine structuring of austenitic stainless steel obtained using an innovative approach of "phase-reversion" has been evaluated for modulation of cellular activity. The biochemical and morphology study with fibroblasts point toward the improvement of tissue compatibility on comparison with coarse-grained structures, strengthening the foundation of nanostructured materials for bio-medical applications. [source]

Favorable Modulation of Pre-Osteoblast Response to Nanograined/Ultrafine-grained Structures in Austenitic Stainless Steel

ADVANCED MATERIALS, Issue 12 2009
R.D.K. Misra
Nanograined (NG)/ultrafine-grained (UFG)structures show enhanced cellular response of pre-osteoblasts. Cell proliferation, viability, and morphology on phase-reversion annealed NG/UFG austenitic stainless steel were observed to be favorably modulated in comparison to conventional coarse-grained austenitic stainless steel. The improvement in cellular response is ascribed to NG/UFG structure and hydrophilicity of the cell substrate. [source]

Austenitic Stainless Steels from Quantum Mechanical Calculations,

ADVANCED ENGINEERING MATERIALS, Issue 4 2004
L. Vitos
Quantum mechanics is used to study the influence of the chemical composition on the elastic properties of austenitic stainless steels. Fe based alloys comprising approximately 15% Cr and 8% Ni are predicted to have the largest hardness among the usual austenitic steels, which, however, is associated with increased brittleness and susceptibility to various forms of localized corrosion. It is shown that few percent of additional Os or Ir to Fe15Cr8Ni alloy significantly improve on both of these shortcomings, without deteriorating the hardness. [source]

New Routes for Fabricating Ultrafine-Grained Microstructures in Bulky Steels without Very-High Strains,

ADVANCED ENGINEERING MATERIALS, Issue 8 2010
Nobuhiro Tsuji
Abstract Several routes to produce ultrafine-grained structures in steels without severe plastic deformation are introduced. The key point of the ideas is to combine plastic deformation with the phase transformation of matrix phases. When as-quenched martensite in steels is used as a starting microstructure, sub-micrometer grain-sized structures can be obtained easily. Another example using a dual-phase steel composed of soft and hard phases is also discussed. Repeating plastic deformation and phase transformation is also effective in obtaining nanostructures in an austenitic stainless steel. Examples of strips of UFG stainless steels in industry and their applications are presented. [source]

Phase Reversion-Induced Nanograined/Ultrafine-Grained Structures in Austenitic Stainless Steel and their Significance in Modulating Cellular Response: Biochemical and Morphological Study with Fibroblasts,

Experimental Determination of Fully-Coupled Kinematical and Thermal Fields at the Scale of Grains Under Cyclic Loading

ADVANCED ENGINEERING MATERIALS, Issue 9 2009
Laurence Bodelot
An experimental setup has been developed to measure fully-coupled kinematic and thermal fields at a very fine resolution matching the microstructure size of a heat-treated austenitic stainless steel. In this study, this setup is used in order to investigate the heterogeneous behavior of a polycrystalline material under cyclic loading, as far as the local strain and temperature data are concerned. [source]

Favorable Modulation of Pre-Osteoblast Response to Nanograined/Ultrafine-grained Structures in Austenitic Stainless Steel

Metal Objects Mapping After Small Charge Explosions.

JOURNAL OF FORENSIC SCIENCES, Issue 3 2006
A Study on AISI 304Cu Steel with Two Different Grain Sizes
ABSTRACT: Evidence of exposure of a metal component to a small charge explosion can be detected by observing microstructural modifications; they may be present even if the piece does not show noticeable overall plastic deformations. Particularly, if an austenitic stainless steel (or another metal having a face-centered cubic structure and a low stacking fault energy) is exposed to an explosive shock wave, high-speed deformation induces primarily mechanical twinning, whereas, in nonexplosive events, a lower velocity plastic deformation first induces slip. The occurrence of mechanical twins can be detected even if the surface is damaged or oxidized in successive events. In the present research, optical metallography (OM) and scanning electron microscopy (SEM), and scanning tunneling microscopy (STM) were used to detect microstructural modifications caused on AISI 304Cu steel disks by small-charge explosions. Spherical charges of 54.5 or 109 g TNT equivalent mass were used at explosive-to-target distances from 6.5 to 81.5 cm, achieving peak pressures from 160 to 0.5 MPa. Explosions induced limited or no macro-deformation. Two alloy grain sizes were tested. Surface OM and SEM evidenced partial surface melting, zones with recrystallization phenomena, and intense mechanical twinning, which was also detected by STM and X-ray diffraction. In the samples' interior, only twins were seen, up to some distance from the explosion impinged surface and again, at the shortest charge-to-sample distances, in a thin layer around the reflecting surface. For forensic science locating purposes after explosions, the maximum charge-to-target distance at which the phenomena disappear was singled out for each charge or grain size and related to the critical resolved shear stress for twinning. [source]

EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel

JOURNAL OF MICROSCOPY, Issue 3 2004
P. Cizek
Summary The evolution of crystallographic texture and deformation substructure was studied in a type 316L austenitic stainless steel, deformed in rolling at 900 °C to true strain levels of about 0.3 and 0.7. Electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were used in the investigation and a comparison of the substructural characteristics obtained by these techniques was made. At the lower strain level, the deformation substructure observed by EBSD appeared to be rather poorly developed. There was considerable evidence of a rotation of the pre-existing twin boundaries from their original orientation relationship, as well as the formation of highly distorted grain boundary regions. In TEM, at this strain level, the substructure was more clearly revealed, although it appeared rather inhomogeneously developed from grain to grain. The subgrains were frequently elongated and their boundaries often approximated to traces of {111} slip planes. The corresponding misorientations were small and largely displayed a non-cumulative character. At the larger strain, the substructure within most grains became well developed and the corresponding misorientations increased. This resulted in better detection of sub-boundaries by EBSD, although the percentage of indexing slightly decreased. TEM revealed splitting of some sub-boundaries to form fine microbands, as well as the localized formation of microshear bands. The substructural characteristics observed by EBSD, in particular at the larger strain, generally appeared to compare well with those obtained using TEM. With increased strain level, the mean subgrain size became finer, the corresponding mean misorientation angle increased and both these characteristics became less dependent on a particular grain orientation. The statistically representative data obtained will assist in the development of physically based models of microstructural evolution during thermomechanical processing of austenitic stainless steels. [source]

Influence of copper-alloying of austenitic stainless steel on multi-species biofilm development

LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2001
J. Kielemoes
Aims: To investigate the bactericidal influence of copper-alloying of stainless steel on microbial colonization. Methods and Results: Inhibition of bacterial adherence was investigated by monitoring (192 h) the development of a multi-species biofilm on Cu-alloyed (3·72 wt%) stainless steel in a natural surface water. During the first 120 h of exposure, lower numbers of viable bacteria in the water in contact with copper-containing steel relative to ordinary stainless steel were observed. Moreover, during the first 48 h of exposure, lower colony counts were found in the biofilm adhering to the Cu-alloyed steel. No lower colony or viable counts were found throughout the remainder of the experimental period. Conclusions: The presence of Cu in the steel matrix impedes the adhesion of micro-organisms during an initial period (48 h), while this bactericidal effect disappears after longer incubation periods. Significance and Impact of the Study: The application of Cu-alloyed stainless steels for bactericidal purposes should be restricted to regularly-cleaned surfaces. [source]

Pitting corrosion on 316L pipes in terephthalic acid (TA) dryer

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 11 2009
Y. Gong
Abstract Grade 316L is a type of austenitic stainless steel with ultra-low carbon content and it exhibits superior corrosion resistance. However, pitting is always observed in 316L steel when it is exposed to media containing halide ions. In the present study, we found that in the presence of acetate acid (HAc) containing chloride or bromide ions, pitting occurred on the surface of the rotary steam pipes with the matrix material of 316L steel in terephthalic acid (TA) dryer. In order to identify the causes of the failure, metallographic structures and chemical compositions of the matrix material were inspected by an optical microscope (OM) and a photoelectric direct reading spectrometer. Beside these, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) as well as ion chromatography (IC) were used to analyze the micromorphologies of the corrosion pits and the chemical compositions of the corrosion deposits within them. Analysis of the results revealed the sources of halide ions and the factors accelerating the corrosion rate. Beside these, detailed mechanisms of pitting were discussed and six out of all the seven theoretical morphologies of pitting features were obtained in practice. [source]

Interdiffusional degradation of oxidation-resistant aluminide coatings on Fe-base alloys

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 10 2007
Y. Zhang
One of the potential degradation modes of oxidation-resistant iron aluminide coatings is the loss of Al from the coatings into Fe-base substrate alloys that typically contain no Al. To address this issue, interdiffusion between aluminide coatings and steel substrates was studied for times up to 10,000 h in the temperature range of 500,800,°C. Coatings were synthesized in a laboratory chemical vapor deposition (CVD) reactor on representative commercial ferritic alloy Fe-9Cr-1Mo and type 304L austenitic stainless steel. The microstructural and compositional changes after diffusion anneals were examined in detail. An initial attempt to model the interdiffusion behavior was carried out by applying an existing software program COSIM (coating oxidation and substrate interdiffusion model). Complementary work was conducted using a simple mathematic model developed by Heckel et al. Reasonable agreement was observed between the simulated and experimental composition profiles for the aluminide coatings on ferritic alloys. Model results were then applied to predict coating lifetime. [source]

Using pit solution chemistry for evaluation of metastable pitting stability of austenitic stainless steel

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 3 2005
M. H. Moayed
Abstract The stability of a corrosion pit is directly related to the pit solution chemistry. In order to know the stability of a meastable pit, the product of corrosion current density and diffusion depth (pit radius for an open hemisphere pit) is compared to the stability product obtained from the artificial pit electrode results. In this paper the stability of a metastable pit recorded on a 904L stainless at 54°C (2°C below the alloy CPT) is investigated. Assuming the geometry result of such a transient is an open hemisphere, pick current density and pit radius were calculated from Faraday's equation and then pit stability product (i·a) was calculated. This value was compared with the product of i·a associated with the pit solution chemistries (critical, saturation and supersaturation concentrations) which were obtained from the investigation on artificial pit electrode at the same temperature. SEM investigations on pit cavity generated from large metastable pit current transients with the stability product greater than the stability product associated with supersaturation concentration of pit environment proves that measured pit solution chemistry from artificial pit electrode is a reliable step for evaluation of pit stability. [source]

EBSD investigation of intergranular corrosion attack on low interstitial stainless steel

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 6 2004
T. Kuníková
Abstract Grain boundary effect on corrosion behaviour of low interstitial AISI 316LN austenitic stainless steel after homogenization and heat treatment at 700 and 800°C was investigated by means of Electron Backscattered Diffraction (EBSD) technique. Rapid oxalic acid etch test (ASTM A262- practice A) was used to determine steel susceptibility to intergranular corrosion. An attempt to quantify oxalic acid etch test results was also made. Beneficial effect of low carbon and nitrogen content on grain boundary precipitation and corrosion was observed. No changes neither in grain orientations nor in grain boundary types between sensitised and non-sensitised steel states using orientation measurements were recorded. Twin boundaries were found in all samples with highest amount and only small occurrence changes. CSL categorizations showed only little increase of special boundary fractions with increasing time and temperature of heat treatment. Irrespective to annealing conditions a continued network of random boundaries was retained. Additionally, based on misorientation measurement of 50 grooved grain boundaries, a tendency for preferred attack of high angle boundaries (30,55°) was noted. [source]

Initiation and propagation of stainless steel pitting corrosion under heat flux

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2003
T. Pro
nichtrostender Stahl; Lochkorrosion; Wärmeübergang; Wärmefluss Abstract An effect of heat flux on initiation and propagation of pitting corrosion of austenitic stainless steel in chloride environment has been studied using electrochemical and exposure methods. The experiments were performed at constant surface temperature of 60°C and heat flux from , 15 to + 74 kW m,2. The presence of heat flux from metal to solution shifted the breakdown potential towards noble values and lowered the pit density, whereas the pit propagation rate increased. Presence of maximum heat flux caused, in comparison with isothermal conditions, increase of the breakdown potential by approx. 100 mV, reduction of pit density by 30% and increase of the average pit depth by 40%. The positive effect of heat flux from metal to solution was given mainly by improving the protective ability of the passive film, as the amount of oxygen available at the metal surface increased. With a smaller significance, the effect of intensified mass transfer, which made accumulation of the chloride ions on the surface more difficult, occurred. Entstehung und Fortschreiten der Lochkorrosion von nichtrostendem Stahl bei Wärmefluss Der Einfluss von Wärmefluss auf die Entstehung und das Fortschreiten der Lochkorrosion bei austenitischen nichtrostenden Stählen in chloridhaltiger Umgebung wurden unter Verwendung elektrochemischer Methoden und in Auslagerungsversuchen untersucht. Die Versuche wurden bei einer konstanten Oberflächentemperatur von 60°C und einem Wärmefluss von , 15 bis 74 kWm2 durchgeführt. Ein Wärmefluss vom Metall hin zur Lösung verschob das Durchbruchspotential hin zu edleren Werten, es verringerte sich die Lochdichte, während eine Zunahme der Lochbildungsrate erfolgte. Ein Maximum des Wärmeflusses bewirkte im Vergleich mit isothermen Bedingungen eine Zunahme des Potentials um ca. 100 mV, eine Verringerung der Lochdichte um 30% und eine Zunahme des Wertes für die Lochtiefe um 40%. Der positive Einfluss des Wärmeflusses in Richtung vom Metall zur Lösung ergab im wesentlichen eine Verbesserung der Schutzwirkung des Passivfilms, da sich die verfügbare Menge Sauerstoff an der Metalloberfläche erhöhte. Weniger signifikant war der Effekt eines erhöhen Stofftransportes, der eine Akkumulation von Chlorid-Ionen an der Oberfläche erschwerte. [source]

PIII nitriding of fcc-alloys containing Ni and Cr

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2008
Johanna Lutz
Abstract Face-centred cubic (fcc) alloys such as austenitic stainless steel, Ni base alloys and Co base alloys are important materials with a high corrosion resistance. Nitrogen insertion by PIII into all these alloys at moderate temperatures leads to the formation of an expanded austenite structure. A similar activation energy for the thermally assisted diffusion of about 0.75 eV was found for steel and CoCr alloys with CrN precipitates beyond 400 °C in both systems. However, a double layer structure was observed for CoCr, similar to Ni alloys, in contrast to a single layer for austenitic steel. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

On the crystal structure of Cr2N precipitates in high-nitrogen austenitic stainless steel.

ACTA CRYSTALLOGRAPHICA SECTION B, Issue 2 2006

The crystal structure and order,disorder transition of Cr2N were investigated utilizing transmission electron microscopy (TEM). Based on the analyses of selected-area diffraction (SAD) patterns, the crystal structure of the ordered Cr2N superstructure was confirmed to be trigonal (), characterized by three sets of superlattice reflections (001), (0) and (1). During electron irradiation, the superlattice reflections gradually disappeared in the regular sequence (001), (0) and (1), indicating that the order,disorder phase transition of Cr2N occurred. The convergent-beam electron diffraction (CBED) observation revealed that the space group of disordered Cr2N is P63/mmc, which corresponds to an h.c.p. (hexagonal close packed) sublattice of metal atoms with a random distribution of N atoms in six octahedral interstices. The redistribution model of N atoms through the order,disorder transition is discussed based on the characteristics and disappearing sequence of superlattice reflections. [source]

Austenitic Stainless Steels from Quantum Mechanical Calculations,

EBSD and TEM investigation of the hot deformation substructure characteristics of a type 316L austenitic stainless steel

Corrosion fatigue of spot-welded austenitic stainless steels in 3.5% NaCl solution

MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 12 2004
M. E. Somervuori
Abstract Corrosion fatigue and fatigue properties of spot-welded austenitic stainless steels EN 1.4301 and EN 1.4318 in 2B or 2F and 2H conditions were investigated in 3.5% sodium chloride (NaCl) solution and in air. The shear-loaded specimens were single spot overlap joints. The effect of steel grade, load, frequency, temperature and type of chloride on fatigue strength of the 1.0 mm thick steel specimens was evaluated by using the Taguchi Method®. Increase of the load, rise of temperature and lowering of the frequency accelerate corrosion fatigue of the spot-welded steel samples. Type of chloride had only a minor effect on fatigue strength. The 2B grade spot-welded steel samples exhibited better fatigue strength than the 2H grade samples of the same steels. On the basis of the results obtained by the Taguchi Method® the S-N curves were defined for the spot-welded 1.9 mm thick steels in 3.5% sodium chloride solution at 50°C. For reference the fatigue experiments were performed in air at the ambient temperature. Comparison of the results shows that corrosive environment decreases remarkably the fatigue strength of the spot-welded steels. The EN 1.4301 2H and EN 1.4318 2H steels have no distinctive difference in their corrosion fatigue strength even though they show a different fatigue behaviour in air. The microscopic investigations indicate that the fatigue cracks in the spot welds initiate from either side of the recrystallised area in the HAZ outside the spot-weld nugget both in air and in the corrosive environments. Pre-exposure in the corrosive environment seems to have no major influence on the crack initiation, because the cracks do not initiate at the heat-tinted area of the crevice where the crevice corrosion occurs. [source]