Showing papers on "Austenitic stainless steel published in 2000"
TL;DR: In this paper, a critical analysis is presented of the operating temperature windows for nine candidate fusion reactor structural materials: four reduced-activation structural materials (oxide-dispersion-strengthened and ferritic/martensitic steels containing 8-12%Cr, V-4Cr-4Ti, and SiC/SiC composites), copper-base alloys (CuNiBe), tantalum base alloys, and molybdenum and tungsten alloys.
442 citations
TL;DR: In this article, a cross-sectional transmission electron microscopy (TEM) was used to study the nitrogen-rich layer produced by nitriding austenitic stainless steel at temperatures below 500°C.
Abstract: This paper attempts to reduce some of the confusion that exists over the nature of the nitrogen-rich layer produced by nitriding austenitic stainless steel at temperatures below 500°C Cross-sectional transmission electron microscopy shows that the modified layer is dominated by a cubic phase with considerable expansion of the austenite lattice In some cases, a thin (
210 citations
TL;DR: In this paper, the authors present a review of low-temperature plasma-assisted nitriding methods for metallurgical surface modification to improve wear, hardness and fatigue resistance of ferrous and non-ferrous materials.
Abstract: Plasma-assisted nitriding is an attractive surface treatment for metallurgical surface modification to improve wear, hardness and fatigue resistance of ferrous and non-ferrous materials. For this purpose, ion nitriding by a d.c. glow discharge is generally efficient for numerous materials. However, for some metals and alloys, the processing temperature, dominated by the discharge parameters, is too high and cannot be controlled independently from the plasma reactivity. This paper reviews the following solutions for low-temperature plasma-assisted nitriding: pulsed d.c. discharge, thermionically assisted d.c. triode arrangements, plasma implantation, electron cyclotron resonance systems and thermionic arc discharges. We focus on metallurgical results obtained by these techniques on austenitic stainless steel and aluminium.
193 citations
15 Nov 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy, showing that the stainless steel weld metals solidified dendritically, while the 16-8-2 (16%Cr-8%Ni-2%Mo) weld metal showed a predominantly cellular substructure.
Abstract: For joining type 316LN austenitic stainless steel to modified 9Cr–1Mo steel for power plant application, a trimetallic configuration using an insert piece (such as alloy 800) of intermediate thermal coefficient of expansion (CTE) has been sometimes suggested for bridging the wide gap in CTE between the two steels. Two joints are thus involved and this paper is concerned with the weld between 316LN and alloy 800. These welds were produced using three types of filler materials: austenitic stainless steels corresponding to 316, 16Cr–8Ni–2Mo, and the nickel-base Inconel 182 1 . The weld fusion zones and the interfaces with the base materials were characterised in detail using light and transmission electron microscopy. The 316 and Inconel 182 weld metals solidified dendritically, while the 16–8–2 (16%Cr–8%Ni–2%Mo) weld metal showed a predominantly cellular substructure. The Inconel weld metal contained a large number of inclusions when deposited from flux-coated electrodes, but was relatively inclusion-free under inert gas-shielded welding. Long-term elevated-temperature aging of the weld metals resulted in embrittling sigma phase precipitation in the austenitic stainless steel weld metals, but the nickel-base welds showed no visible precipitation, demonstrating their superior metallurgical stability for high-temperature service.
186 citations
TL;DR: In this article, a series of experiments designed to study the influence of plasma nitriding on the mechanical properties of austenitic stainless steel were conducted on AISI 304L steel in a temperature range of 375-475°C using pulsed-DC plasma with different N2-H2 gas mixtures and treatment times.
Abstract: In this paper, we report on a series of experiments designed to study the influence of plasma nitriding on the mechanical properties of austenitic stainless steel. Plasma nitriding experiments were conducted on AISI 304L steel in a temperature range of 375–475°C using pulsed-DC plasma with different N2–H2 gas mixtures and treatment times. Firstly the formation and the microstructure of the modified layer will be highlighted followed by the results of hardness measurement, adhesion testing, wear resistance and fatigue life tests. The modified surface was analyzed directly after plasma nitriding as well as using a depth profiling method. The microhardness after plasma nitriding is increased up to 19 GPa, that is a factor of five higher compared to the untreated material (3.3 GPa). The adhesion is examined by Rockwell indentation and scratch test. No delamination of the treated layer could be observed. The wear rate after plasma nitriding is significantly reduced compared to the untreated material. Plasma nitriding produces compressive stress inside the modified layer, which can be easily derived from the bending of thin metal foil, which was treated only on one side. The treatment influences the fatigue life, which can be raised by a factor of 10 at a low stress level (230 MPa).
167 citations
TL;DR: In this article, a trimetallic joint involving modified 9Cr-1Mo steel and 316LN austenitic stainless steel as the base materials and Alloy 800 as the intermediate piece was investigated.
150 citations
TL;DR: In this article, a set of ODS steels with varying oxide particle dispersion were irradiated at 650°C, using 3.2 MeV Fe + and 330 keV He + ions simultaneously.
139 citations
TL;DR: In this article, the authors compared 316L and Rex734 stainless steels in terms of mechanical properties, corrosion and dry wear resistance as well as the combined wear-corrosion behavior.
123 citations
TL;DR: In this paper, a model for the transport of nitrogen in austenitic stainless steel at temperatures around 400°C is presented and discussed, considering the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium.
Abstract: A model for the transport of nitrogen in austenitic stainless steel at temperatures around 400 °C is presented and discussed. The model considers the diffusion of nitrogen under the influence of trapping and detrapping at trap sites formed by local chromium. Nitrogen depth profiles simulated on the basis of the model with diffusion and detrapping activation energies of 1.1 and 1.45 eV, respectively, are in good agreement with experimental nitrogen profiles.
120 citations
TL;DR: In this paper, a small amount of liquid nitrogen was injected to the chip-tool interface, but not to the workpiece, which yielded a 67% tool-life improvement at 3.82 m/s and a 43% improvement at the medium speed of 3.40m/s when compared with conventional emulsion cooling.
Abstract: While it is a clean alternative to conventional machining using environmentally polluting cutting oils and emulsions, cryogenic machining using liquid nitrogen has been reported to increase cutting forces and shorten tool life when cutting AISI 304 austenitic stainless steel. This paper presents improved results by using an economical cryogenic cooling approach designed after studying the cryogenic properties of the stainless steel material. By injecting a small amount of liquid nitrogen to the chip–tool interface, but not to the workpiece, this approach yielded a 67% tool-life improvement at 3.82 m/s and a 43% improvement at the medium speed of 3.40 m/s when compared with conventional emulsion cooling. It improved machining productivity and reduced production cost. In this study, different cryogenic machining approaches were compared in the machining test using commercial carbide inserts. The results show the cooling approach is crucial in attaining the benefits of cryogenic machining in cutting stainless steel.
118 citations
TL;DR: In this article, Austenitic stainless steels 316L(N)-IG and 316L, nickel-based alloys Inconel 718 and ICONEL 625, Ti-6Al-4V alloy and two copper alloys, CuCrZr−IG and CuAl25−IG, have been proposed as reference structural materials, and ferritic steel 430, and austenitic steel 304B7 with the addition of boron have been selected for some specific parts of the ITER in-vessel components.
TL;DR: In this paper, the authors measured the strain response of multiple hkl lattice planes to an applied uniaxial tensile load using neutron diffraction, to macroscopic plastic strains of around 1%.
TL;DR: In this paper, an explanation for the chemical changes which lead to high-rate dissolution of sulfide inclusions and hence to pit initiation is found in the composition changes induced in the sulfides as the steel cools from the melting temperature of the steel to the solidification temperature, and metallic phases rich in iron and depleted in chromium may precipitate within the inclusion.
Abstract: An explanation for the chemical changes which lead to high-rate dissolution of sulfide inclusions and hence to pit initiation is found in the composition changes induced in the sulfides as the steel cools from the melting temperature of the steel to the solidification temperature of the sulfide. In this temperature regime, on cooling, substantial chromium depletion of the steel may occur around the sulfide, and metallic phases rich in iron and depleted in chromium may precipitate within the inclusion. These chromium-depleted zones can provide the high-rate dissolution which triggers pitting corrosion. Experimental observations on artificial inclusions are supported by thermodynamic calculations.
TL;DR: In this paper, the use of low-pressure rf plasmas for nitriding with an emphasis on treatments at temperatures of 250-450°C was reported, i.e. well below those used by more conventional methods.
Abstract: This paper reports advances in the use of low-pressure rf plasmas for nitriding with an emphasis on treatments at temperatures of 250–450°C; i.e. well below those used by more conventional methods. The treatment of austenitic stainless steel AISI-316 was chosen to represent the efficacy of such plasmas for nitriding over a wide temperature range, producing thicker nitrogen-rich layers at low temperature than more conventional methods in the same process time. This is due to a lower activation energy. Application of high-voltage pulses to the workpiece (plasma-immersion ion implantation, PI3) increases the thickness of the nitrogen-rich layer but does not significantly alter the activation energy. Other aspects of the process investigated include the role of hydrogen, various regimes of plasma-based cleaning, process gas purity and the variation of workpiece bias, from zero up to the 10s of kV characteristic of PI3.
TL;DR: In this article, a new strain-induced martensitic transformation kinetics model and constitutive equation of TRIP steels are proposed by considering the dependence of the austenitic grain size.
15 Jul 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the dependence of cyclic behavior, fatigue crack initiation and fatigue life on crystallographic texture was investigated for a 316L austenitic stainless steel in the low cycle fatigue range.
Abstract: The dependence of cyclic behavior, fatigue crack initiation and fatigue life, on crystallographic texture was investigated for a 316L austenitic stainless steel in the low cycle fatigue range. Specimens of five different orientations of the rolled sheet were compared to study different textures. It is shown that, texture influences the stress–strain response of the material and the fatigue damage (crack density). Moreover, to study the influence of the environment on the fatigue behavior and the coupling effects with crystallographic aspects, fatigue tests were performed in air and in vacuum. It is shown that the environment modifies both the total crack density and the ratio of transgranular to intergranular cracks. All results are discussed with regard to the relative fraction of 〈111〉 and 〈100〉 grains oriented for multiple slip or to the fraction of grains favoring single slip behavior.
TL;DR: Grain-boundary carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy to clarify the effect of grainboundary structure on precipitation and corrosion as discussed by the authors.
Abstract: Grain-boundary carbide precipitation and intergranular corrosion in sensitized austenite stainless steel were examined by transmission electron microscopy to clarify the effect of grain-boundary structure on precipitation and corrosion The propensity to intergranular precipitation depends strongly on the grain-boundary structure Carbide precipitates tend to be detected at grain boundaries with higher Σ values or larger deviation angles (Δθ) from low-Σ coincidence site lattice misorientations The more ordered boundary requires a longer time for intergranular carbide precipitation and corrosion than less ordered or random boundaries
TL;DR: In this article, the microstructure of AISI 304 stainless steel was studied by optical microscopy and both glancing angle and conventional Bragg-Brentano (θ-2θ) symmetric geometry X-ray diffraction (XRD).
Abstract: Low pressure plasma arc discharge-assisted nitriding of AISI 304 austenitic stainless steel is a process that produces surface layers with useful properties such as a high surface hardness of approximately 1500 Hv0.1 and a high resistance to frictional wear and corrosion. The phase composition, the thickness, the microstructure and the surface topography of the nitrided layer, as well as its properties, depend essentially on the process parameters. Among them, the processing temperature is the most important factor for forming a hard layer with good wear and corrosion resistance. Nitriding austenitic stainless steel at approximately 420°C for 70 min can produce a thin layer of 7–8 μm with very high hardness and good corrosion resistance on the surface. The microstructure was studied by optical microscopy and both glancing angle and conventional Bragg–Brentano (θ–2θ) symmetric geometry X-ray diffraction (XRD). The formation of expanded austenite was observed. Measurements of the wear depths indicated that the wear resistance of austenitic stainless steel can be improved greatly by nitriding at approximately 420°C using low-pressure plasma-arc source ion nitriding.
31 Jan 2000-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the influence of copper as an alloying element on the structure and passive behaviour of ferritic Fe and duplex ferritic-austenitic Fe was investigated.
Abstract: The paper presents investigations of the influence of copper as an alloying element on the structure and on the passive behaviour of ferritic Fe–18%Cr and duplex ferritic–austenitic Fe–24%Cr–6%Ni–3%Mo cast alloys. Copper dissolved in the solid solution (austenite) does not show detrimental effect on the stability of a passive film. The solubility of copper in ferrite is lower than in austenite and therefore the e-phase can be precipitated during thermal treatment (500–600°C). Ferritic alloy containing high copper content (1.58%Cu) shows precipitation of the e-phase already in cast form (without sensitisation). In duplex ferritic–austenitic steels, the precipitation of the e-phase in ferrite occurs during the sensitisation in a temperature range 500–600°C. The presence of the e-phase stimulates pitting corrosion of ferrite. Electrochemical measurements of the passive behaviour of investigated materials show that the alloys containing precipitates of the the e-phase undergo pitting corrosion in 1 M H 2 SO 4 –1 M NaCl. Thermal treatment dissolving the e-phase increases the resistance of alloys to local attack. Our experiments show that the increase of copper content in ferritic alloys increases also the tendency to chromium segregation at grain boundaries and thus the tendency to intergranular corrosion of cast alloys.
TL;DR: The electrochemical impedance spectroscopy technique was used to investigate the interfacial behavior of beta-lactoglobulin at an austenitic stainless steel surface over the temperature range 299 to 343 K at an open circuit potential and the adsorption process was found to be entirely governed by the change in entropy.
TL;DR: In this article, the load sharing between phases and the evolution of micro- and macrostresses during cyclic loading was investigated in a 1.5mm cold-rolled sheet of the duplex stainless steel SAF 2304.
Abstract: The load sharing between phases and the evolution of micro- and macrostresses during cyclic loading has been investigated in a 1.5-mm cold-rolled sheet of the duplex stainless steel SAF 2304. X-ray ...
TL;DR: In this paper, the microstructure of the layers produced by plasma nitriding austenitic stainless steel at different treatment temperatures (400 and 500°C) were studied by transmission electron microscopy (TEM) together with X-ray diffraction (XRD) and scanning electron microscope (SEM).
Abstract: The microstructure of the layers produced by plasma nitriding austenitic stainless steel at different treatment temperatures (400 and 500°C) were studied by transmission electron microscopy (TEM) together with X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the microstructures were composed of ‘expanded austenite’ (γ N ) and α(ferrite)+CrN following plasma nitriding at lower and higher treatment temperatures, respectively. The former contains stacking faults and deformed twin substructures, while the latter is made up of colonies displaying a lamellar structure. Kurdjumov–Sachs or Nishiyama–Wassermann orientation relationships between the α and CrN layer were observed.
TL;DR: In this paper, the lattice expansion of austenitic stainless steels after nitrogen plasma immersion ion implantation by x-ray diffraction is investigated, showing that the expansion along the (100) direction is about 20% larger than for the (111) direction.
Abstract: Nitrogen treatment of austenitic stainless steels at temperatures around 300–400 °C leads to the formation of a hard and corrosion resistant phase called expanded austenite. The most puzzling feature of this phase is an anisotropic lattice expansion where the expansion along the (100) is about 20% larger than for the (111) direction. In this report an investigation of the lattice expansion of austenitic stainless steel after nitrogen plasma immersion ion implantation by x-ray diffraction is presented. Pole figure measurements as well as θ/2θ scans at different polar angles were performed. Comparing the data with three different structural models, fcc, tetragonal, and triclinic, it can be concluded that none of them yields good agreement with the data, so that the crystallographic characterization is still open. However, a model for the atomic origin of the observed lattice expansion based on the anisotropic Young’s modulus, which is found for every fcc metal, is presented, showing good agreement with the ...
TL;DR: In this paper, a free-form laser consolidation is used to build functional metallic components from a computer-aided design model, by using an optical fiber coupled Nd:YAG laser beam along with the simultaneous delivery of desired metal/alloy powders through a nozzle into the molten pool.
Abstract: Functional metallic components can be built layer by layer from a computer-aided design model, by using an optical fiber coupled Nd:YAG laser beam along with the simultaneous delivery of desired metal/alloy powders through a nozzle into the molten pool. Building of shapes using various alloys, including 316 L stainless steel, Ni-base IN-625 superalloy, and M4 tool steel, have been investigated. The components built using the free-form laser consolidation are metallurgically sound, free of cracks and porosity. Surface finish on the order of 1–2 μm (Ra) can be obtained on the consolidated samples. The microstructure of the laser-consolidated samples is similar to the rapidly solidified materials. Under certain conditions, directionally solidified microstructure can also be obtained. X-ray diffraction analysis reveals that laser-consolidated material maintains the same phase structure as the original powder. The tensile properties of the laser-consolidated IN-625 alloy and 316 L stainless steel are comparabl...
TL;DR: In this article, cyclic polarization scans, scratch tests and Contact Electric Resistance (CER) technique were used to study localized corrosion behavior of UNS S30403 type stainless steel in simulated paper mill environments at pH 3 or 5 (55 or 65°C).
TL;DR: In this article, the deformation microstructure consisted of twins, elongated faulted loops, and lath and twin martensite phase, and it was shown that twinning was the predominant deformation mode at slower strain rate.
TL;DR: In this paper, the influence of different gas compositions on the structure and phase composition of the layers is examined and compared with results from pure nitrogen and methane, and the results provide further information about expanded austenite (S-phase) which is formed during the low temperature nitriding of austenitic stainless steels.
Abstract: Plasma immersion ion implantation has been used for simultaneous implantation of carbon and nitrogen into austenitic stainless steel X5CrNi189 at 400°C. Duplex layer structures are formed with a nitrogen-rich layer close to the surface and a carbon-rich layer at greater depth. The influence of different gas compositions on the structure and phase composition of the layers is examined and compared with results from pure nitrogen and methane. The results provide further information about ‘expanded austenite’ (S-phase) which is formed during the low temperature nitriding of austenitic stainless steels.
TL;DR: In this paper, the effects of strain-induced grain boundaries on the internal stresses and the related lattice distortions evolved in these grain interiors are discussed in detail, and a submicron-scale substructure evolution in a 304 type stainless steel caused by severe warm deformation at 0.5 T{sub m}.