Showing papers on "Austenitic stainless steel published in 2007"
TL;DR: In this paper, the effects of external stress and stacking fault energies (SFE) on the width of the stacking faults were analyzed and an excellent correlation between the calculations and actual microstructures examined by scanning electron microscopy was found.
678 citations
TL;DR: In this paper, the authors provide a framework for describing the permeability, solubility and diffusivity of hydrogen and its isotopes in austenitic stainless steels at temperatures and high gas pressures of interest for hydrogen storage and distribution infrastructure.
361 citations
TL;DR: Protective Al2O3 scale formation was achieved with smaller amounts of aluminum in austenitic alloys than previously used, provided that the titanium and vanadium alloying additions frequently used for strengthening were eliminated.
Abstract: A family of inexpensive, Al2O3-forming, high-creep strength austenitic stainless steels has been developed. The alloys are based on Fe-20Ni-14Cr-2.5Al weight percent, with strengthening achieved through nanodispersions of NbC. These alloys offer the potential to substantially increase the operating temperatures of structural components and can be used under the aggressive oxidizing conditions encountered in energy-conversion systems. Protective Al2O3 scale formation was achieved with smaller amounts of aluminum in austenitic alloys than previously used, provided that the titanium and vanadium alloying additions frequently used for strengthening were eliminated. The smaller amounts of aluminum permitted stabilization of the austenitic matrix structure and made it possible to obtain excellent creep resistance. Creep-rupture lifetime exceeding 2000 hours at 750 degrees C and 100 megapascals in air, and resistance to oxidation in air with 10% water vapor at 650 degrees and 800 degrees C, were demonstrated.
300 citations
TL;DR: Pitting corrosion of Type 304 stainless steel under drops of MgCl2 solution has been investigated to clarify the rusting mechanism in marine atmospheres as discussed by the authors, and a pitting corrosion test was performed under the droplets with various combinations of the diameter and thickness by exposure to a constant relative humidity.
224 citations
TL;DR: In this article, microbially-influenced corrosion of stainless steel AISI 316 by two sulphate-reducing bacteria, Desulfovibrio desulfuricans and a local marine isolate was investigated using atomic force microscopy (AFM).
201 citations
TL;DR: In this article, an analysis of the relationship between yield strength and grain size in submicron-grained stainless steels indicates a classical Hall-petch behavior, and when the yield dependence on annealing temperature is considered, the results show that the Hall-Petch relation is due to an interplay between finegrained austenite, solid solution strengthening, precipitate hardening and strain hardening.
Abstract: An ultra-fine-grained AISI 301LN austenitic stainless steel has been achieved by heavy cold rolling, to induce the formation of martensite, and subsequent annealing at 800 °C, 900 °C, and 1000 °C, from 1 to 100 seconds. The microstructural evolution was analyzed using transmission electron microscopy and the yield strength determined by tension testing. Ultra-fine austenite grains, as small as ∼0.54 μm, were obtained in samples annealed at 800 °C for 1 second. For these samples, tensile tests revealed a very high yield strength of ∼700 MPa, which is twice the typical yield strength of conventional fully annealed AISI 301LN stainless steels. An analysis of the relationship between yield strength and grain size in these submicron-grained stainless steels indicates a classical Hall–Petch behavior. Furthermore, when the yield dependence on annealing temperature is considered, the results show that the Hall–Petch relation is due to an interplay between fine-grained austenite, solid solution strengthening, precipitate hardening, and strain hardening.
155 citations
15 Sep 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, laser-shock peening and deep rolling were applied to an austenitic stainless steel AISI 304 and the effects on the fatigue life were investigated, e.g. s/n curves, cyclic deformation curves as well as the residual stress stability of the laser-shatter peened condition were compared to untreated and deep rolled conditions.
Abstract: Laser-shock peening and deep rolling were applied to an austenitic stainless steel AISI 304 and the effects on the fatigue life were investigated. Isothermal push–pull fatigue tests were performed in the temperature range 25–600 °C. The results of the investigations, e.g. s/n curves, cyclic deformation curves as well as the residual stress stability of the laser-shock peened condition were compared to untreated and deep rolled conditions. Near-surface regions were characterized using X-ray diffraction methods, transmission electron microscopy (TEM) and focused ion beam microscopy (FIB). The different near-surface microstructures as well as residual stress stabilities of laser-shock peened and deep rolled specimens were investigated and discussed.
149 citations
TL;DR: Wrought austenitic stainless steels are widely used in high temperature applications as mentioned in this paper, and a short review discusses initially the processing of this class of steels, with emphasis on solidification and hot working behavior.
Abstract: Wrought austenitic stainless steels are widely used in high temperature applications. This short review discusses initially the processing of this class of steels, with emphasis on solidification and hot working behavior. Following, a brief summary is made on the precipitation behavior and the numerous phases that may appear in their microstructures. Creep and oxidation resistance are, then, briefly discussed, and finalizing their performance is compared with other high temperature metallic materials.
143 citations
TL;DR: In this paper, the surface of nano-titania nano-coating with anions of nitrogen, sulfur and chlorine was evaluated by electrochemical impedance spectroscopy (EIS) and electrochemical polarization measurements.
140 citations
TL;DR: In this article, the authors investigated the effect of MC carbide precipitates on the performance of Al-modified austenitic stainless steels and found that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of nbC within the γ-Fe matrix.
Abstract: Creep strengthening of Al-modified austenitic stainless steels by MC carbides or Fe2Nb Laves phase was explored. Fe-20Cr-15Ni-(0–8)Al and Fe-15Cr-20Ni-5Al base alloys (at. pct) with small additions of Nb, Mo, W, Ti, V, C, and B were cast, thermally-processed, and aged. On exposure from 650 °C to 800 °C in air and in air with 10 pct water vapor, the alloys exhibited continuous protective Al2O3 scale formation at an Al level of only 5 at. pct (2.4 wt pct). Matrices of the Fe-20Cr-15Ni-5Al base alloys consisted of γ (fcc) + α (bcc) dual phase due to the strong α-Fe stabilizing effect of the Al addition and exhibited poor creep resistance. However, adjustment of composition to the Fe-15Cr-20Ni-5Al base resulted in alloys that were single-phase γ-Fe and still capable of alumina scale formation. Alloys that relied solely on Fe2Nb Laves phase precipitates for strengthening exhibited relatively low creep resistance, while alloys that also contained MC carbide precipitates exhibited creep resistance comparable to that of commercially available heat-resistant austenitic stainless steels. Phase equilibria studies indicated that NbC precipitates in combination with Fe2Nb were of limited benefit to creep resistance due to the solution limit of NbC within the γ-Fe matrix of the alloys studied. However, when combined with other MC-type strengtheners, such as V4C3 or TiC, higher levels of creep resistance were obtained.
139 citations
TL;DR: In this paper, a three-ply clad sheet, comprised of austenitic stainless steel (STS304), aluminum (Al1050) and copper (C1220), was fabricated by means of a hot-rolling process at 350°C and the mechanical and interfacial properties were investigated for use in cookware applications.
TL;DR: In this paper, the effects of TiO 2 addition on the properties of the coating were investigated in terms of microhardness and fracture toughness values, and the results indicated that an increase in TiO2 amount improves fracture toughness and lowers the micro-hardness values of the coatings.
Abstract: Plasma sprayed ceramic coatings are successfully used in many industrial applications, where high wear and corrosion resistance with thermal insulation are required. In this study, various types of Al 2 O 3 –TiO 2 plasma sprayed coatings in different compositions (Al 2 O 3 –13 wt.% TiO 2 , Al 2 O 3 –40 wt.% TiO 2 and Al 2 O 3 –50 wt.% TiO 2 ) were prepared on an AISI 304L austenitic stainless steel substrate. The effects of TiO 2 addition on the properties of the coating were investigated in terms of microhardness and fracture toughness values. The results obtained from experimental work were evaluated with standard characterisation techniques. The results indicated that an increase in TiO 2 amount improves fracture toughness and lowers the microhardness values of the coatings.
TL;DR: In this article, the deformation induced martensite formation was analyzed by X ray diffraction, electron back scatter diffraction (EBSD), magnetic methods and atomic force microscope (AFM) in samples of a low SFE austenitic stainless steel, AISI 301LN and compared with a medium SFE 316L.
Abstract: In austenitic stainless steels, plastic deformation can induce martensite formation. The induced martensite is related to the austenite (g) instability at temperatures close or below room temperature. The metastability of austenite stainless steels increases with the decreasing of stacking fault energy (SFE). In this work, the deformation induced martensite was analyzed by X ray diffraction, electron back scatter diffraction (EBSD), magnetic methods and atomic force microscope (AFM) in samples of a low SFE austenitic stainless steel, AISI 301LN and compared with a medium SFE stainless steel, AISI 316L. Both techniques, X ray diffraction and EBSD, presented similar quantities for the a-martensite. Texture results indicate that the crystallographic orientation of the formed a-martensite is {001} and {103} . The morphology of a-martensite was analyzed by AFM. Corrosion tests showed that deformation reduces pitting corrosion and generalized corrosion resistance in both steels.
TL;DR: In this article, a twin-induced grain boundary engineered 304 austenitic stainless steel with a high frequency of coincidence site lattice boundaries produced by a one-step thermomechanical process was arc-welded.
TL;DR: In this paper, high-resolution and spatially resolved analytical transmission electron microscopy revealed the precise carbide-austenite orientation relationship, a highly coherent interface, and precipitation only occurs when the carbon-induced lattice expansion of the austenite has reached a level that substantially reduced volume-misfit stress and diffusional transport of nickel, chromium, and iron.
TL;DR: In this article, pure mechanical and thermo-mechanical laser shock processing treatments have been carried out on an AISI 316L stainless steel, and a significant improvement in the pitting corrosion resistance was observed in 0.05 M NaCl.
Abstract: Pure mechanical and thermo-mechanical laser shock processing treatments have been carried out on an AISI 316L stainless steel. Surface properties, mostly mechanical and metallurgical modifications, were analysed at different scales: a local scale using the nano-indentation technique and AFM analysis, and a more macroscopic scale, using microhardness, optical microscopy and residual stress determinations. After a pure mechanical laser-peening treatment, a significant improvement in the pitting corrosion resistance (+0.1 V) was observed in 0.05 M NaCl. This improvement was attributed to the combined effects of compressive residual stresses and work-hardening, and, in turn, to a mechano-electrochemical phenomenon by which a modification of cathodic reactions occurs during electrochemical tests. For the surface treated by thermo-mechanical laser peening (combination of a surface ablation and shock waves), a tendency for decreasing resistance against pitting corrosion was shown, and attributed to the processing-specific surface texture (ablation craters), which made the material susceptible for the creation of occluded cells.
15 May 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a nickel-base hardfacing alloy AWS NiCr-B was deposited on austenitic stainless steel substrate 316 LN using the plasma transferred arc-welding process.
Abstract: In the current investigation, nickel-base hardfacing alloy AWS NiCr-B was deposited on austenitic stainless steel substrate 316 LN using the plasma transferred arc-welding process. The deposit was characterized by hardness measurements, microstructural examination and sliding wear assessment. Identification of precipitates was carried out using X-ray diffraction, scanning electron microscope/energy dispersive X-ray analysis (SEM/EDAX), electron probe micro analyzer (EPMA) mappings and line-scan profiles. The microstructure of the hardfacing deposit predominantly consists of the γ-Ni phase and the interdendritic eutectic mixture comprised of γ-nickel and nickel-rich borides. These studies also revealed the presence of chromium-rich carbides and borides in a γ-nickel matrix. The sliding wear behaviour of the hardfacing alloy was investigated in air at three different temperatures viz., room temperature, 300 and 500 °C. The study revealed significant weight loss at room temperature and abrupt decrease at high temperatures. This behaviour at high temperatures has been attributed to the formation of a wear protective oxide layer at the surface during sliding. To evaluate the microstructural stability of the deposit, ageing studies were carried out at 650 °C for 250 h. Microstructural examination and hardness testing revealed that there is no deterioration in the microstructure and that the hardness remains intact. Sliding wear tests at room temperature and at high temperatures also demonstrated that there is no significant change in the weight loss or the wear behaviour after the thermal exposure.
TL;DR: In this paper, the development of mathematical equations using a three factor 5-level factorial technique to predict the geometry of weld bead in butt joint of austenitic stainless steel 304 sheet of 2.5 mm thickness is presented.
Abstract: Laser beam welding (LBW) is a field of growing importance in industry with respect to traditional welding methodologies due to lower dimension and shape distortion of components and greater processing velocity. Because of its high weld strength to weld size ratio, reliability and minimal heat affected zone, laser welding has become important for varied industrial applications. With increased use of laser welding in continuous mode, there will be increased dependence on the use of equations to predict the dimensions of the weld bead. In this paper, the development of mathematical equations using a three factor 5- level factorial technique to predict the geometry of weld bead in butt joint of austenitic stainless steel 304 sheet of 2.5 mm thickness are presented. The models developed have been checked for their significance by using F-test and t-test. The direct and interaction effect of the process variables on bead geometry are presented in graphical form for quick analysis.
TL;DR: In this article, a general prescription for as-welded residual stress distributions in stainless steel pipe butt welds of arbitrary diameter and thickness, based solely on finite element studies, is critically examined by comparing the estimated profiles with an array of diverse weld residual stress measurements in pipe welds 16mm to 110mm thick.
TL;DR: In this article, the rate of stress corrosion cracking (SCC) was measured for nonsensitized, cold-worked Type 316 (UNS S31600) and Type 304 (Uns S30400) in both hydrogenated pressurized water reactor (PWR) and PWR.
Abstract: The rate of stress corrosion cracking (SCC) was measured for nonsensitized, cold-worked Type 316 (UNS S31600) and Type 304 (UNS S30400) in both hydrogenated pressurized water reactor (PWR)...
TL;DR: Pitting immersion test performed on 316 austenitic stainless steel weld metals showed that austenite is the preferential phase for corrosion attack in 3% ferric chloride solution at critical pitting temperature.
TL;DR: Extensive creep cavitation precluded the beneficial effect of Cu addition on long-term creep rupture strength of 18Cr-12Ni-Nb (type 347) austenitic stainless steel as mentioned in this paper.
TL;DR: Fully reversed fatigue tests have been performed on wrought 316L stainless steel samples after low-temperature carburization, and the resulting 25μm case depth, with a surface hardness three times that of the core and a surface compressive stress greater than 2 GPa, leads to significantly enhanced fatigue performance.
TL;DR: In this paper, the influence of Cu and Sn on the pitting corrosion resistance of AISI 304 and 316 stainless steels in chloride-containing media has been investigated, and the corrosion behavior was evaluated by cyclic polarization, potentiostatic CPT measurements and electrochemical impedance spectroscopy in 3.5-wt% NaCl.
07 Jul 2007-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the formation mechanism of spinel inclusions containing the spinel crystals was developed based on the experimental results and from the compositions of the inclusions in the steel samples taken during plant operations.
Abstract: Fundamental thermodynamics of the relationship between high-alloyed stainless steel melts (Fe-20 mass pct Cr-13 mass pct Ni-3 mass pct Si) and the inclusions were investigated. The formation mechanism of the inclusions containing the spinel crystals was developed based on the experimental results and from the compositions of the inclusions in the steel samples taken during plant operations. The molar content of alumina in the inclusions was found to be linearly proportional to the increase of aluminum content, indicating that the inclusions could contain alumina even with less than about 200 ppm aluminum in the steel melt, e.g., steel melts that were mainly deoxidized by silicon. Furthermore, the composition of the inclusions is shown to be a function of the activity of the deoxidizers such as aluminum and silicon in the steel melt. From the analysis of the plant samples, it was found that the contents of MgO and Al2O3 in the calcium silicate type inclusions increased continuously as the steel melt transfers from the argon oxygen decarburization (AOD) converter to the tundish. This composition change in the inclusions originated from the reduction of MgO and Al2O3 in the slags or refractories by silicon in the steel melt. Increases of MgO and Al2O3 contents were prominent in tundish samples, and thus, the spinel phase could be crystallized in the calcium silicate inclusion matrix in the tundish; and finally the spinel crystals grew during cooling of the steel melt through the continuous casting (CC) mold and in the slabs. On the other hand, manganese silicate type inclusions containing chromium oxide were observed after tapping of the molten steel to the ladle. The MnO and Cr2O3 in these inclusions was initially reduced by silicon in the steel melt in the ladle treatment (LT) process, followed by further reduction by aluminum through the LT to the CC mold. The fractions of inclusions containing spinel crystals in cast slabs were negligible at the alumina content of less than about 20 mass pct, while they critically increased at alumina contents greater than about 20 mass pct.
TL;DR: In this article, the role of nitrogen on the samples sintered under nitrogen-hydrogen atmosphere and its relation to the microstructural features was described, and the results were correlated to the presence of precipitates and mainly to the lamellar constituent.
25 Sep 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effects of pulsed magnetic field on the microstructure of 1Cr18Ni9Ti austenitic stainless steel were investigated, and it was shown that during the solidification of the steel, applications of magnetic field can significantly refine its micro-structure.
Abstract: The aim of this paper is to investigate the effects of pulsed magnetic field on the microstructure of 1Cr18Ni9Ti austenitic stainless steel. Experimental results indicate that during the solidification of 1Cr18Ni9Ti austenitic stainless steel, applications of pulsed magnetic field can significantly refine its microstructure. And there is an optimal value of magnetic intensity under which the grain size is the finest. Moreover, applications of pulsed magnetic field can significantly reduce the solidification time, and also lead to increase of the initiation and finishing solidification temperature.
15 Jun 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, a wear resistant TiC titanium carbide-reinforced composite coating was fabricated on 1Cr18Ni9Ti austenitic stainless steel substrate by plasma-transferred arc (PTA) weld-surfacing process using Fe-Ti-C powder blends.
Abstract: A wear resistant TiC titanium carbide-reinforced composite coating was fabricated on 1Cr18Ni9Ti austenitic stainless steel substrate by plasma-transferred arc (PTA) weld-surfacing process using Fe–Ti–C powder blends. The microstructure, microhardness and dry-sliding wear behavior of the composite coating were investigated using optical microscopy (OM), X-ray diffraction (XRD), scanning electron micrograph (SEM), energy-dispersive X-ray analysis (EDS), microhardness tester and ring-on-ring wear tester. The formation mechanism of the composite coating has been discussed. Results show that the composite coating consists of primary TiC carbide as the reinforcing phase and TiC/γ-Fe eutectics as the matrix. The composite coating is metallurgically bonded to the 1Cr18Ni9Ti austenitic stainless steel substrate. The TiC/γ-Fe composite coating has high hardness and excellent wear resistance under dry-sliding wear test condition.
TL;DR: A pin-on-disk tribometer was employed to perform wear tests and in addition to wear, structural changes of AISI 304 stainless steel were investigated under wear condition as discussed by the authors.
TL;DR: In this article, the influence of the primary welding parameters affecting the heat input such as; peak current on the morphology, microhardness, and tensile shear load bearing capacity of dissimilar welds between AISI 316L austenitic stainless steel and DIN EN 10130-99 (7114 grade) interstitial free steel has been investigated.