Stainless Alloys Research Articles

Development of a magnetic sensor system for predictive IASCC diagnosis on stainless steels in a nuclear reactor

The authors previously reported that magnetic flux leakage d ata, measured using a flux gate (FG) sensor, showed a correlation with the irradiation-assisted stress corros ion cracking (IASCC) susceptibility of neutron-irradiate d austenitic stainless alloys. This paper presents a study conducted to develop a diagnostic system that can detect IASCC precursors in stainless steels by measuring the magnetic properties of the material. The eddy current method and alternating current (AC) magnetization method were used, as these will be more practical for use in actual reactors. Probes were developed for these measurement methods, providing sufficient tolerance for en vironments in nuclear reactors. An attempt was also made to improve spatial resolution by manufacturing a smaller probe. A sensor system was designed for remote control, performance tests were conducted by measuring neutron-irradiated specimens and mock specimens, and magnetic data were evaluated by comparing the IASCC susceptibility of the specimens. It was proved that the sensor system developed in this study is capable of detecting IASCC precursors. Further developments necessary for application in actual nuclear reactors and the mechanism of correlation between magnetic properties and IASCC susceptibility were also discussed. Many of the problems experienced in existing light water reactors (LWR) are caused by damage to structural materials. Stress corrosion cracking (SCC) and irradiation-assisted SCC (IASCC) of structural materials have been especially serious problems, and it has not been possible to predict these in the reactor design process. These problems will become more significant when existing reactors start to age from now on, and when advanced reactors are operated and structural materials are used in more severe irradiation environments in future. It is therefore import ant to develop diagnostic techniques that can

Forming characteristics of austenitic stainless steel sheet alloys under warm hydroforming conditions

Stainless steel sheet alloys have been increasingly used in heating, ventilating, and air conditioning; appliance; sanitary and medical devices; as well as several structural and transportation applications, due to their high strength-to-weight ratio, corrosion resistance, biomedical compatibility, and esthetic appearance. Among various stainless steel alloys, austenitic stainless steels are the most commonly used type. Due to the forming limitations into complex shapes at room temperature conditions and stress-corrosion cracking issues, forming at elevated temperature has been considered as an enabling technique. Formability of stainless steels is affected by strain rate and temperature due to martensitic transformation of meta-stable austenite microstructure. In this study, deformation characteristics of three common austenitic stainless steels (AISI 201, 301, and 304) were investigated using closed-die hydroforming under different process conditions. Specifically, effects of pressure, temperature, and die/part geometry on the material forming characteristics quantified using cavity filling ratio and thinning distribution were investigated. Results suggested that, in terms of cavity filling, pressure and material grade are significant factors while temperature is not in the case of axisymmetric part. For the non-axisymmetric case, all parameters were found to be significant. In addition, finite element (FE) modeling was performed to simulate several forming cases that were experimentally conducted in this study. The FE model was simulated based on material flow curves obtained from previous studies under similar conditions (strain rate and temperature) by the authors. FEA results were shown to be in good agreement with experimental findings, particularly for cavity filling and part profile predictions. Hence, the FE model and the material models can be used for further predictions of complex and different parts with confidence.

The Semiconductor Character of Passive Film of 304L Stainless Steel(SS), 316L SS and Nickel Alloy 800 Formed in Zinc Contained High-Temperature and High-Pressure Water

The semiconductor properties of passive film formed on 304L stainless steel (SS), 316L SS and Alloy 800HT in high-temperature and high-pressure water with zinc addition have been investigated by using Polarization curve, Mott-Schottky analysis and photocurrent method. The donor density, flat band and band gap of semiconductor behavior are analyzed to investigate the impact of zinc addition to the passive film. Analysis of the experimental results indicated that passive film formed on 316L and 800HT with zinc addition showed different electrochemical, photo-electrochemical and semiconductor properties. The results indicated that corrosion resistance of passive film from in high-temperature and high-pressure water with zinc addition was obviously better than that without zinc addition.

Effect of neutron irradiation on tensile properties of austenitic steel XM-19 for the ITER application

Austenitic chromium manganese stainless alloy XM-19 is proposed to use as a material for the ITER in-vessel components such as divertor attachments.The paper presents the results of experimental investigation into the effect of neutron irradiation dose on radiation hardening and of XM-19 alloy. Specimens of XM-19 alloy were irradiated at a temperature of 300°C to doses of 10−3, 10−2, 10−1dpa in the RBT-6 reactor in Dimitrovgrad.It is shown that neutron irradiation to 0.1dpa at Tirr=300°C increases the yield strength of XM-19 alloy by 100MPa. The uniform elongation was slightly reduced from 45% to 40% at 0.1dpa, Tirr=300°C.The investigations performed show that XM-19 alloy demonstrates high level of the strength properties in the initial and irradiated state and has a good ductility after irradiation. The conclusion is made that XM-19 alloy holds promises for ITER application due to its good radiation resistance.

A comparative study of the corrosion resistance of incoloy MA 956 and PM 2000 superalloys

Austenitic stainless steels, titanium and cobalt alloys are widely used as biomaterials. However, new medical devices require innovative materials with specific properties, depending on their application. The magnetic properties are among the properties of interest for some biomedical applications. However, due to the interaction of magnetic materials with Magnetic Resonance Image equipments they might used only as not fixed implants or for medical devices. The ferromagnetic superalloys, Incoloy MA 956 and PM 2000, produced by mechanical alloying, have similar chemical composition, high corrosion resistance and are used in high temperature applications. In this study, the corrosion resistance of these two ferritic superalloys was compared in a phosphate buffer solution. The electrochemical results showed that both superalloys are passive in this solution and the PM 2000 present a more protective passive film on it associated to higher impedances than the MA 956.

Comparative analysis of two methods of determining the force parameters in the extrusion of tubes made of stainless steels and alloys

A comparative analysis is made of two methods of determining the force parameters in the extrusion of tubes made of stainless steels and alloys. Results are presented from calculations of the parameters for the extrusion of tubes of alloy EI 943 on the press lines in heating-and-rolling shop No. 2 at the Volzhskii Pipe Plant. Conclusions are made as to the nature and usefulness of the two methods for calculating the force parameters of the extrusion operation.

Photoelectrochemical Investigation of Radiation-Enhanced Shadow Corrosion Phenomenon

Abstract The photoelectrochemical investigation was performed by measuring the photoelectrochemical behavior of various alloys such as Zircaloy 2, 304 stainless steel (SS) and Alloy X-750 in 0.01M Na2SO4 at 25°C or in high purity water at 300°C under intense ultraviolet (UV) illumination. UV was selected because its photon energy (∼5 eV) is similar to the energy gap of the electron-hole pairs in zirconium oxide. The data show that the photoexcitation of ZrO2 caused the corrosion potential to shift in the anodic direction and produced anodic photocurrents under the oxidizing water chemistry condition when Zircaloy 2 electrode was galvanically coupled with dissimilar electrodes, such as Alloy X-750, 304 SS, or Pt, causing accelerated corrosion of Zircaloy. It is thus postulated that the photoelectrochemical enhancement of surface reaction kinetics at the ZrO2 surface may be responsible for the radiation-enhanced corrosion on Zircaloy (i.e., shadow corrosion). In addition, it is revealed that no significant change in galvanic current between Zircaloy 2 and other dissimilar electrodes was measured in high temperature water containing only hydrogen that resulted in similar ECPs. These data thus clearly provide an explanation for why the radiation-enhanced corrosion of Zircaloy only occurs in BWRs but not PWRs. Based on galvanic corrosion, impedance, and transmission electron microscopy analysis, it is proposed that the defect structure of equiaxed grain layers may be responsible for the photoelectrochemical response of ZrO2 in high temperature water. The mechanism of shadow corrosion is still highly debated but it appears to be similar to a process of galvanic corrosion in connection with sufficiently conducting Zr oxide structure. The galvanic corrosion data suggests that a Zr coating on the fuel assembly spacer (Alloy X-750 or 304 SS) may mitigate the shadow corrosion in BWRs.

Global trends and environmental issues in nickel mining: Sulfides versus laterites

Nickel (Ni) is an important metal in modern infrastructure and technology, with major uses in stainless steel, alloys, electroplating and rechargeable batteries. Economic Ni resources are found in either sulfide or laterite-type ores. Although the majority of economic resources are contained in laterite ores, the bulk of historic Ni production has been derived from sulfide ores since laterites require more complex processing. To meet future demand for Ni, there is an increasing amount of Ni being mined from laterite ores—leading to increasing energy and greenhouse gas emission costs for Ni production. In many of the major Ni fields of the world, environmental impacts have also been significant, especially in Sudbury in Canada and the Taimyr and Kola Peninsulas in Russia. A major gap in the literature remains on historical trends in global Ni mining, especially with respect to primary aspects such as production, known economic resources and ore grades and type. This paper compiles and analyses a wide array of data on global Ni mining, presenting a coherent picture of major historical trends and the current industry configuration. The paper includes unique historical data sets for major Ni fields, especially the Sudbury Basin and Thompson fields in Canada and the Kambalda field in Australia. By understanding these critical ‘mega-trends’ in the Ni industry, it is possible to better understand unfolding global issues, such as environmental impacts, greenhouse gas emissions, climate change and potential industry responses, and whether ‘peak nickel’ is a viable concept and the implications these issues have for Ni production and demand. The data, trends and issues synthesized in this paper therefore provide a compelling picture of the Ni industry, and should help to inform current research and policy directions.

Metallic ions in organs of rats injected with metallic particles of stainless steel 316L and Ti6Al4V alloy

Despite the interest in identifying systemic effects caused by the metallic particles released from long term metallic implants in the body, few works support reliable conclusions about the effects of those particles in organs. The aim of the present work is to look for damages in tissues of liver, kidney, lung and heart of rats submitted to injection of Hank's solution contained particles of Ti6Al4V alloy and Stainless Steel 316L, obtained by metal friction. The particles size ranges from 50 to 200 µm for the Ti alloy and from 100 to 500 µm for the 316L. Tissues isolated from the organs after the euthanasia were prepared and analyzed in an optical microscope and Energy Dispersive Spectrometer (EDS). Lesions caused by an inflammatory response such as strange body epithelioid granuloma and giant cells were found in some of the tissues containing yttrium and aluminum.

The X-Ray Diffraction Characteristics of Different Materials

The x-ray diffraction characteristics of different materials are discussed in this paper. It is found that the accurate determination of real stress is not easy to obtain when two diffraction peaks with low diffraction intensity are shown and the residual stress of stainless steel, aluminum, titanium alloy materials etc are determined by X-ray method. Five kinds of uniform intensity girders made from common carbon steel (Q235), austenite stainless steel (1Cr18Ni9Ti), martensitic stainless steel(A335P92), aluminium alloy(LY12) and titanium alloy(TA15) are determined repeatedly using uniform intensity girder demarcation method. It is proved by experiment results that X-ray diffraction peaks at some angles can’t well reflect the real change of stress.

Ion Leaching from Implantable Medical Devices

Implantable medical devices must be able to withstand the corrosive environment of the human body for 10 or more years without adverse consequences. Most reported research and development has been on developing materials and devices that are biocompatible and resistant to corrosion-fatigue, pitting, and crevice corrosion. However, little has been directly reported regarding implantable materials with respect to the rate at which they generate soluble ions in-vivo. Most of the biocompatibility studies have been done by examining animal implants and cell cultures rather than examining the rate at which these materials leach ions into the body. This paper will discuss what is currently known about the rate at which common implant materials (such as stainless steels, cobalt-chromium alloys, and nitinol) elute ions under in vitro conditions, what the limitations are of such data, and how this data can be used in medical device development.

Insights into Stress Corrosion Cracking Mechanisms from High-Resolution Measurements of Crack-tip Structures and Compositions

AbstractResults are presented employing cross-sectional analytical transmission electron microscopy (ATEM) to examine intergranular stress corrosion cracking (IGSCC) of austenitic stainless alloys in high-temperature water environments. Microstructural, chemical and crystallographic characterization of buried interfaces at near-atomic resolutions is used to investigate corrosion/oxidation reactions, composition changes and deformation events at crack tips. Information obtained by a wide variety of high-resolution imaging and analysis methods indicates the processes occurring during crack advance and provides insights into the mechanisms controlling SCC. Examples of crack tips produced in oxidizing and hydrogenated water are presented for both Fe-base stainless steels (SSs) and Ni-base stainless alloys. Cracks in SSs show similar characteristics in both environments, with oriented oxide films at crack walls and cracks ending in few-nm-wide tips. Many of these same features are seen for alloy 182 in oxidizing water suggesting a common mechanism, generally consistent with a slip oxidation process. A distinct difference is seen at alloy 600 and alloy 182 tips produced in hydrogenated water. Penetrative attack along grain boundaries without evidence for significant plastic deformation is believed to indicate a major role of active-path corrosion/oxidation in the SCC process.

Stress Corrosion Cracking of Nitrogen-containing Stainless Steel 316LN in High Temperature Water Environments

Stress corrosion cracking(SCC) of stainless steels and Ni-based alloys in high temperature water coolant is one of the key problems affecting the safe operation of nuclear power plants(NPPs).The nitrogen-added stainless steel is a kind of possible candidate materials for mitigating SCC since reducing the carbon content and adding nitrogen to offset the loss in strength caused by the decrease in carbon content can mitigate the problem of sensitization.However,the reports of SCC of nitrogen-added stainless steels in high temperature water are few available.The effects of applied potential and sensitization treatment on the SCC of a newly developed nitrogen-containing stainless steel(SS) 316LN in high temperature water doped with chloride at 250 ℃ were studied by using slow strain rate tests(SSRTs).The SSRT results are compared with our data previously published for 316 SS without nitrogen and 304NG SS with nitrogen,and the possible mechanism affecting the SCC behaviors of the studied steels is also discussed based on SSRT and microstucture analysis results.The susceptibility to cracking of 316LN SS normally increases with increasing potential.The susceptibility to SCC of 316LN SS was less than that of 316 SS and 304NG SS.Sensitization treatment at 700 ℃ for 30 h showed little effect on the SCC of 316LN SS and significant effect on the SCC of 316 SS.The predominant cracking mode for the 316LN SS in both annealed state and the state after the sensitization treatment was transgranular.The presented conditions of mitigating stress corrosion cracking are some useful information for the safe use of 316LN SS in NPPs.

Self-welding susceptibility of 316LN and alloy D9 stainless steels in high-temperature flowing sodium

The self-welding susceptibility of 316LN Stainless Steel (SS) and alloy D9 (15Cr-15Ni-2Mo titanium-modified) SS in 20% cold-worked conditions was evaluated in flowing sodium at 823 K under a maximum contact stress of 12 MPa and for durations of 3, 6 and 9 months. The specimens used were hollow, cylindrical and stacked one above the other under compression using disc springs. The breakaway shear force was measured for self-welded specimens. The results for the two types of SS were compared using scanning electron micrographs, energy dispersive spectroscopic analysis, hardness and microstructures.

Results of the Application of the Mdn in the Improvement of the Design of an Electrical Furnace that produces Low Carbon Ferromanganese

World-wide steel production is currently about 1 350 million tons per year (more specific, in the 2007 the production has been the 1 343 million tons). The 45% of total production is low carbon steels (ferritic steels), products (C� 0.10%) while 25%, 10% and 20% of the rest, respectively, can be attributed to ferritic‐pearlitic steels (C� 0.25%), pearlitic steels (C� 0.80%) and special products (stainless and high alloy). Manganese has always been one of the common elements in the chemical specifications, both for carbon steels as well as for special steels. Nevertheless, and due to the importance of high resistance and high toughness ferritic products, its role as an alloy element has become highly valued in recent years. The presence of manganese in ferritic steel simultaneously favors resistance (s y yield strength) as well as toughness (ITT °C, Impact Transition Temperature) of the products, a circumstance that is quite uncommon both in alloy elements of either a substitutional or intersticial solid solution character. In the new generations of IF (Interstitial Free) steels it can be said that the role of carbon and of interstitial elements (nitrogen, hydrogen and boron) have been relegated to the category of impurity. The presence of the mentioned elements, however, remarkably diminishes the toughness of the product. For this reason one tends to value the contents

ENVIRONMENTALLY-ASSISTED CRACKING OF ENGINEERING MATERIALS - AN INSIGHT

This paper reviews the environmentally-assisted-cracking studies of some of the key engineering materials i.e. austenitic stainless steels, aluminium alloys and magnesium alloys. Some of the salient work carried out by the research laboratories and institutions in India and other countries, in this critical research area, are brought out in this paper.

Adopting a multipurpose inhibitor to control corrosion of ferrous alloys in cooling water systems

The heterocyclic compounds; 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Phenyl), 5-methoxyphenyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Methoxy), 5-tolyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Tolyl), 5-tolyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)one (Inon), 2,5-diphenyl-3-iodopyrazolo[1,5-c]pyrimidine-7(6H)thione (Iodo) and 2,5-diphenyl-3-bromopyrazolo[1,5-c]pyrimidine-7(6H)thione (Bromo) were screened by Tafel Extrapolation and Linear Polarization Resistance techniques to detect the possibility of inhibition the uniform corrosion of carbon steel in stagnant cooling water containing 200 ppm chloride at 25 °C. The inhibition efficiencies of the studied compounds were found to decrease in the following order: Tolyl > Methoxy > Phenyl > Iodo > Bromo > Inon. The Tolyl compound was proved to be the most efficient inhibitor on carbon steel and therefore trialed on stainless steels 304 and 316 to examine its applicability as a multipurpose inhibitor at the same operating conditions. It was revealed that the Tolyl doses inhibit the pitting corrosion of both the stainless alloys. The Tolyl compound; therefore, functions as true multipurpose corrosion inhibitor for different ferrous alloys in industrial cooling water systems. For example, the percentage inhibition of 10 mmole L −1 of the Tolyl compound is 93.42%, 82.91% and 85.40% for carbon steel, 304SS and 316SS, respectively.

In vitro comparison of different carotid artery stents: a pixel-by-pixel analysis using CT angiography and contrast-enhanced MR angiography at 1.5 and 3 T

CT angiography (CTA) and MR angiography (MRA) are increasingly used methods for evaluation of stented vessel segments. The purpose of this study was to compare CTA, contrast-enhanced MRA (CEMRA) at 1.5 T, and CEMRA at 3 T for the visualization of carotid artery stents and to define the best noninvasive imaging technique for each stent. CTA and CEMRA appearances of 18 carotid artery stents of different designs and sizes (4.0 to 10.0 mm) were investigated in vitro. The profile of the contrast-to-noise ratio (CNR) of the lumen of each stent was calculated semiautomatically by a pixel-by-pixel analysis using the medical imaging software OSIRIS. For each stent, artificial lumen narrowing (ALN) was calculated. In all but one stents, ALN was lower on CEMRA at 3 T than at 1.5 T. With CEMRA at 3 T and at 1.5 T, ALN in most nitinol stents was lower than in the groups of stainless steel and cobalt alloy stents. In most nitinol stents, ALN on CEMRA at 3 T was lower than on CTA. In all stainless steel stents and cobalt alloy stents, ALN was lower on CTA than on CEMRA. With CTA and CEMRA, in most stents ALN decreased with increasing stent diameter. CTA and CEMRA evaluation of vessel patency after stent placement is possible, but considerably impaired by ALN. Investigators should be informed about the method of choice for every stent.

Evaluation of passive film behaviour of super austenitic stainless steels at different potential regions using dynamic electrochemical impedance spectroscopy

Potentiodynamic anodic polarisation and dynamic electrochemical impedance spectroscopic (DEIS) measurements were carried out on 316L stainless steel and alloys 926 and 31 in natural seawater in order to assess the crevice corrosion resistance. DEIS measurements were performed over a wide range of potentials covering the corrosion potential, passive region, breakdown region and dissolution region. The impedance measurements in potentiodynamic conditions clearly reveal the changes that occur in the passive layer with change in potential. The impedance spectra at different potential regions were also discussed elaborately. The surface morphology of the alloy after crevice corrosion was studied using optical microscope and atomic force microscopy.

Role of welding in an operating LNG manufacturing entity

AbstractWelding is not only a most important tool for nascent fabrication and erection of continuous process units but also in repair and maintenance, including for modifications and extensions. Liquefied natural gas (LNG), natural gas in liquid form that facilitates transport over large distances, is of large and growing importance for power generation. Though LNG plants are fairly simple from the process engineering point of view, the gamut of materials required is very wide. It is common to find many grades of carbon steel, high strength low alloy steels, elevated temperature resistant steels, high toughness steels for low temperature operation, high alloy steels, a broad range of stainless steels, aluminium and nickel alloys, copper and copper alloys, and titanium materials – in the forms of valves, equipment, tanks, structures, piping, etc. Case studies of the ways in which welding has contributed to the operational integrity of an LNG unit are presented. The role of welding in replacements and repai...