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Development of materials resistant to metal dusting degradation.

Description: Metal dusting corrosion has been a serious problem in the petroleum and petrochemical industries, such as reforming and syngas production systems. This form of deterioration has led to worldwide material loss for 50 years. For the past three years, we have studied the mechanism of metal dusting for Fe- and Ni-base alloys. In this report, we present a correlation between the weight loss and depth of pits that form in Ni-base alloys. Nickel-base alloys were also tested at 1 and 14.8 atm (210 psi), in a high carbon activity environment. Higher system pressure was found to accelerate corrosion in most Ni-base alloys. To reduce testing time, a pre-pitting method was developed. Mechanical scratches on the alloy surface led to fast metal dusting corrosion. We have also developed preliminary data on the performance of weldments of several Ni-base alloys in a metal dusting environment. Finally, Alloy 800 tubes and plates used in a reformer plant were examined by scanning electron microscopy, energy dispersive X-ray, and Raman spectroscopy. The oxide scale on the surface of the Alloy 800 primarily consists of Fe{sub 1+x}Cr{sub 2-X}O{sub 4} spinel phase with high Fe content. Carbon can diffuse through this oxide scale. It was discovered that the growth of metal dusting pits could be stopped by means of a slightly oxidized alloy surface. This leads to a new way to solve metal dusting problem.
Date: April 24, 2006
Creator: Natesan, K. & Zeng, Z.
Partner: UNT Libraries Government Documents Department

Calculations on the compatibility of refractory metals in a tritium environment and cold trapping method for tritium removal from a lithium blanket

Description: From joint meeting of the American Nuclear Society and the Atomic Industrial Forum and Nuclear Energy Exhibition; San Francisco, California, USA (11 Nov 1973). Thermodynamic calculations were made on the distribution of hydrogen and tritium between various refractory metals and liquid lithium as a function of temperature. The limiting tritium pressures that can be attained by cold trapping of secondary liquid metals such as Na, K, and NaK were calculated. In the absence of tritium breeding, these pressures are 2.5 x 10/sup -5/, 2 x 10/ sup -7/ and 1.2 x 10/sup -10/o torr for Na, K, and NaK, respectively, and these correspond to tritium concentrations in lithium of 45, 4, and <1 ppM, respectively, at 700 deg C. For a thermonuclear reactor of 1000 MW(t) thermal power with a tritium breeding rate of 150 g/day, a tritium recovery system that incorporates a separate lithium purification loop with niobium as the permeable membrane, NaK as the secondary heat transport fluid and with tungsten cladding on the IHX tubes seems to yield tritium pressures of ~10/sup -9/ torr or less in the secondary system. This leads to tritium release rate of ~10/sup -6/g/ hr to the steam system for a steam generator clad with tungsten and operating at ~600 deg C. This corresponds to activity release rate of~300 Ci/yr. (17 figures, 61 references) (auth)
Date: January 1, 1973
Creator: Natesan, K. & Smith, D.L.
Partner: UNT Libraries Government Documents Department

Corrosion and Mechanical Behavior of Materials for Coal Gasification Applications

Description: A state-of-the-art review is presented on the corrosion and mechanical behavior of materials at elevated temperatures in coal-gasification environments. The gas atmosphere in coal-conversion processes are, in general, complex mixtures which contain sulfur-bearing components (hydrogen sulfide, SO2, and COS) as well as oxidants (carbon dioxide/carbon monoxide and water/hydrogen). The information developed over the last five years clearly shows sulfidation to be the major mode of material degradation in these environments. The corrosion behavior of structural materials in complex gas environments is examined to evaluate the interrelationships between gas chemistry, alloy chemistry, temperature, and pressure. Thermodynamic aspects of high-temperature corrosion processes that pertain to coal conversion are discussed, and kinetic data are used to compare the behavior of different commercial materials of interest. The influence of complex gas environments on the mechanical properties such as tensile, stress-rupture, and impact on selected alloys is presented. The data have been analyzed, wherever possible, to examine the role of environment on the property variation. The results from ongoing programs on char effects on corrosion and on alloy protection via coatings, cladding, and weld overlay are presented. Areas of additional research with particular emphasis on the development of a better understanding of corrosion processes in complex environments and on alloy design for improved corrosion resistance are discussed.
Date: May 1980
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Corrosion performance of structural alloys.

Description: Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.
Date: July 15, 1999
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Corrosion performance of structural alloys in oxygen/sulfur/chlorine-containing environments.

Description: Component reliability and long-term trouble-free performance of structural materials are essential in power-generating processes that utilize coal as a feedstock. The combustion environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional systems to air-deficient conditions in low-NO{sub x} systems. Apart from the environmental aspects of the effluent from coal combustion, one concern from the systems standpoint is the aggressiveness of the combustion environment toward boiler structural components such as waterwall tubes and steam superheaters. The corrosion tests in this program address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded boiler materials exposed to air-deficient and excess-air combustion conditions. Data in this paper address the corrosion behavior of structural materials such as Type 347 stainless steel, Alloys 800, 825, 625, 214, and Hastelloy X when exposed at 650 C to excess-air combustion conditions with and without HCl. Thermodynamic calculations were made to evaluate the gas chemistries formed from coal combustion. The results of such calculations, coupled with oxygen/sulfur/chlorine thermochemical diagrams, were used to select the gas environments for the laboratory test program. Results are presented for weight change, thickness loss, microstructural characteristics of corrosion products, mechanical integrity and cracking of scales, and the mechanistic understanding gained on the role of sulfur and chlorine in the corrosion process.
Date: June 22, 1998
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Fabrication and performance of AIN insulator coatings for application in fusion reactor blankets

Description: The liquid-metal blanket concept for fusion reactors requires an coating on the first-wall structural material to minimize the magnetohydrodynamic pressure drop that occurs during the flow of liquid metal in a magnetic field. Based on the thermodynamics of interactions betwen the coating and the liquid lithium on one side and the structural V-base alloy on the other side, an AIN coating was selected as a candidate. Detailed investigations were conducted on the fabrication, metallurgical microstructure, compatibility in liquid Li, and electrical characteristics of AIN material obtained from several sources. Lithium compatibility was studied in static systems by exposing AIN-coated specimens to liquid Li for several time periods. Electrical resistance was measured at room temperature on the specimens before and after exposure to liquid Li. The results obtained in this study indicate that AIN is a viable coating from the standpoint of chemical compatibility in Li, electrical insulation, and ease of fabrication; for these reasons, the coating should be examined further for fusion reactor applications.
Date: September 1, 1995
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Surface modification: advantages, techniques, and applications

Description: Adequate performance of materials at elevated temperatures is a potential problem in many systems within the chemical, petroleum, process, and power-generating industries. Degradation of materials occurs because of interaction between the structural material and the exposure environment. These interactions are generally undesired chemical reactions that can lead to accelerated wastage and alter the functional requirements and/or structural integrity of the materials. Therefore, material selection for high-temperature applications must be based not only on a material strength properties but also on resistance to the complex environments prevalent in the anticipated exposure environment. As plants become larger, the satisfactory performance and reliability of components play a greater role in plant availability and economics. However, system designers are becoming increasingly concerned with finding the least expensive material that will satisfactorily perform the design function for the desired service life. This present paper addresses the benefits of surface modification and identified several criteria for selection and application of modified surfaces in the power sector. A brief review is presented on potential methods for modification of surfaces, with the emphasis on coatings. In the final section of the paper, several examples address the requirements of different energy systems and surface modification avenues that have been applied to resolve the issues.
Date: March 1, 2000
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Characterization of deposits and effect of deposits on corrosion of materials for MHD balance-of-plant applications

Description: Candidate heat exchanger materials tested in the Low Mass Flow Train at the Coal-Fired Flow Facility (CFFF) at Tullahoma, TN, were analyzed to evaluate their corrosion performances. Tube specimens obtained at each foot of the 14-ft-long U-bend tubes were analyzed for corrosion-scale morphologies, scale thicknesses, and internal penetration depths. Results developed on 1,500- and 2,000-h exposed specimens were correlated with exposure temperature. In addition, deposit materials collected at several locations in the CFFF were analyzed in detail to characterize the chemical and physical properties of the deposits and their influence on corrosion performance of tube materials.
Date: December 1, 1993
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Corrosion performance of iron aluminides in single- and multioxidant environments.

Description: Iron aluminide intermetallics are being developed for use as structural materials and/or as cladding for conventional engineering alloys. In addition to their strength advantages, these materials exhibit excellent resistance to corrosion in single- and multioxidant environments at elevated temperatures through the formation of slow-growing, adherent alumina scales. Even though these intermetallics develop protective oxide scales in single-oxidant environments, the simultaneous presence of several reactants in the environment (typical of practical systems) can lead to development of oxide scales that are nonprotective and that undergo breakaway corrosion, or to nonoxide scales that are detrimental to the performance of the underlying alloy. This paper describes the corrosion performance of Fe-Al intermetallics in environments that contain sulfur, carbon, chlorine, and oxygen and that are typical of fossil energy systems. Emphasis is on mechanisms of scale development and breakdown, performance envelopes for long-term usage of these materials, and approaches to modifying the surfaces of engineering alloys by cladding or coating them with intermetallics to improve their corrosion resistance.
Date: June 22, 1998
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Effect of oxidation/sulfidation on creep behavior of alloy 800

Description: Metallic components within or immediately adjacent to gasifiers, such as gas distributors, thermowells, transfer lines, and cyclones, are subjected to particularly severe conditions of temperature, pressure, and hostile multicomponent gas environments. In addition, metallic heat exchangers/waste-heat boilers that are resistant to sulfidation, corrosion, and erosion in low- and medium-Btu gas environments are essential components in large-scale gasification schemes in both dry-ash and slagging-type gasifiers. Components of these schemes must generally be resistant to corrosion, erosion, and high-temperature creep. Refractory linings are conventionally employed to mitigate corrosion and erosion; in some cases, internal cooling has been considered a way to avoid problems associated with the interaction of high-temperature creep and fatigue. Contrary to the codes and standards that exist for vessel and piping design, no guidance in the form of a code or standard exists for internal and long-life external vessel components, especially for service in corrosive-erosive environments at elevated temperatures. The purpose of the present work is to examine the high-temperature creep behavior of Alloy 800, a high-chromium alloy that is widely used in coal conversion systems, after exposure to oxygen and oxygen/sulfur mixed-gas environments over a wide temperature range. In addition, data on the creep behavior of the alloy under various pretreatment and test exposure conditions are used to establish performance envelopes for the alloy in fossil energy applications.
Date: May 1, 1995
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Study of metal dusting phenomenon and development of materials resistant to metal dusting.

Description: The deposition of carbon from carbonaceous gaseous environments is prevalent in many chemical and petrochemical processes such as reforming systems, syngas production systems, iron reduction plants, and others. One of the major consequences of carbon deposition is the degradation of structural materials by a phenomenon known as metal dusting. There are two major issues of importance in metal dusting. First is formation of carbon and subsequent deposition of carbon on metallic materials. Second is the initiation of metal dusting degradation of the alloy. Details are presented on a research program that is underway at Argonne National Laboratory to study the metal dusting phenomenon from a fundamental scientific base involving laboratory research in simulated process conditions and field testing of materials in actual process environments. The project has participation from the US chemical industry, alloy manufacturers, and the Materials Technology Institute, which serves the chemical process industry.
Date: March 13, 2002
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

High-temperature corrosion in power-generating systems.

Description: Several technologies are being developed to convert coal into clean fuel for use in power generation. From the standpoint of component materials in these technologies, the environments created by coal conversion and their interactions with materials are of interest. Coal is a complex and relatively dirty fuel that contains varying amounts of sulfur and a substantial fraction of noncombustible mineral constituents, commonly called ash. Corrosion of metallic and ceramic structural materials is a potential problem at elevated temperatures in the presence of complex gas environments and coal-derived solid/liquid deposits. This paper discusses the coal-fired systems currently under development, identifies several modes of corrosion degradation that occur in many of these systems, and suggests possible mechanisms of metal wastage. Available data on the performance of materials in some of the environments are highlighted, and the research needed to improve the corrosion resistance of various materials is presented.
Date: May 22, 2002
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Generalized method of computing carbon-diffusion profiles in austenitic stainless steels exposed to a sodium environment

Description: Numerous experimental observations on the carburization-decarburization behavior of austenitic stainless steels in hightemperature flowing sodium have been reported; however, quantitative predictions of carbon diffusion in the steels under specific environmental conditions have been difficult. A mathematical analysis for the process has been developed that incorporates (1) the thermodynamic and kinetic information for carbon in the alloys, (2) the thermal-mechanical treatment of the material (solution annealed versus cold worked) that influences the microstructure, and (3) the carbon concentration in sodium and its dependence on sodium-system parameters. Carbon concentrationdistance profiles in Types 304 and 316 stainless steel were generated as a function of time, temperature, and carbon concentration in sodium and compared with experimental data. The analysis was used to evaluate the carburization -- decarburization behavior of Type 316 stainless steel fuel cladding exposed to sodium and to develop carbon-diffusion profiles in Type 304 stainless steel intermediate-heat-exchanger piping upon exposure to primary- and secondary-system sodium for periods to 30 y. (auth)
Date: June 1, 1973
Creator: Snyder, R.B.; Natesan, K. & Kassner, T.F.
Partner: UNT Libraries Government Documents Department

Effect of oxidation on tensile properties of a V-5Cr-5Ti alloy

Description: Oxidation studies were conducted on V-5Cr-5Ti alloy specimens at 5000{degrees}C in an air environment to evaluate the alloy`s oxygen uptake behavior as a function of temperature and exposure time. Oxidation rates, calculated from measurements of thermogravimetric testing, are 5, 17, and 27 {mu}m after a 1-yr exposure at 300, 400, and 5000{degrees}C, respectively. Uniaxial tensile tests were conducted on preoxidized specimens of the alloy to examine the effects of oxidation and oxygen migration on tensile strength and ductility. Microstructural characteristics of several of the tested specimens were characterized by electron-optical techniques. Correlations have been developed between the tensile strength and ductility of the oxidized alloy and microstructural characteristics such as oxide thickness, depth of hardened layer, depth of intergranular fracture zone, and transverse crack length.
Date: May 1, 1995
Creator: Natesan, K. & Soppet, W.K.
Partner: UNT Libraries Government Documents Department

Corrosion and its effect on mechanical properties of materials for advanced combustion systems

Description: Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high-temperature furnaces and heat transfer surfaces that can operate at temperatures much higher than those prevalent in current coal-fired power plants. The combination of elevated temperatures and hostile combustion environments necessitates development and application of advanced ceramic materials in these designs. The objectives of the present program are to evaluate (a) the chemistry of gaseous and condensed products that arise during combustion of coal; (b) the corrosion behavior of candidate materials in air, slag and salt environments for application in the combustion environments; and (c) the residual mechanical properties of the materials after corrosion. The program emphasizes temperatures in the range of 1000-1400{degrees}C for ceramic materials and 600-1000{degrees}C for metallic alloys. Coal/ash chemistries developed on the basis of thermodynamic/kinetic calculations, together with slags from actual combustors, are used in the program. The materials being evaluated include monolithic silicon carbide from several sources: silicon, nitride, silicon carbide in alumina composites, silicon carbide fibers in a silicon carbide- matrix composite, and some advanced nickel-base alloys. The paper presents results from an ongoing program on corrosion performance of candidate ceramic materials exposed to air, salt and slag environments and their affect on flexural strength and energy absorbed during fracture of these materials.
Date: May 1, 1996
Creator: Natesan, K.; Freeman, M. & Mathur, M.
Partner: UNT Libraries Government Documents Department

Corrosion performance of ceramic materials in slagging environments

Description: Conceptual designs of advanced combustion systems that use coal as feedstock require high-temperature furnaces and heat transfer surfaces that can operate at temperatures much higher than in current coal-fired power plants. Combination of elevated temperatures and hostile combustion environments requires advanced ceramics. Objectives of this program are to evaluate the (a) chemistry of gaseous and condensed products arising during coal combustion, (b) corrosion behavior of candidate materials in air, slag, and salt environments, and (c)residual mechanical properties of the materials after corrosion. Temperatures in the range of 1000-1400 C for ceramics and 600-1000 C for metallic alloys are emphasized. Coal/ash chemistries developed on the basis of thermodynamic/kinetic calculations, together with slags from actual combustors, are used. Materials being evaluated include monolithic Si carbides from several sources: Si nitride, Si carbide in alumina composites, Si carbide fibers in a Si carbide-matrix composite, and some advanced Ni-base alloys. This paper presents results from an ongoing program on corrosion performance of candidate ceramic materials exposed to air, salt, and slag environments and their effect on flexural strength and energy absorbed during fracture of these materials. 10 figs, 4 tabs, 8 refs.
Date: October 1, 1996
Creator: Natesan, K.
Partner: UNT Libraries Government Documents Department

Oxidation performance of V-Cr-Ti alloys

Description: Vanadium-base alloys are being considered as candidates for the first wall in advanced V-Li blanket concepts in fusion reactor systems. However, a primary deterrent to the use of these alloys at elevated temperatures is their relatively high affinity for interstitial impurities, i.e., O, N, H, and C. The authors conducted a systematic study to determine the effects of time, temperature, and oxygen partial pressure (pO{sub 2}) in the exposure environment on O uptake, scaling kinetics, and scale microstructure in V-(4--5) wt.% Cr-(4--5) wt.% Ti alloys. Oxidation experiments were conducted on the alloys at pO{sub 2} in the range of 5 x 10{sup {minus}6}-760 torr (6.6 x 10{sup {minus}4}-1 x 10{sup 5} Pa) at several temperatures in the range of 350--700 C. Models that describe the oxidation kinetics, oxide type and thickness, alloy grain size, and depth of O diffusion in the substrate of the two alloys were determined and compared. Weight change data were correlated with time by a parabolic relationship. The parabolic rate constant was calculated for various exposure conditions and the temperature dependence of the constant was described by an Arrhenius relationship. The results showed that the activation energy for the oxidation process is fairly constant at pO{sub 2} levels in the range of 5 x 10{sup {minus}6}-0.1 torr. The activation energy calculated from data obtained in the air tests was significantly lower, whereas that obtained in pure-O tests (at 760 torr) was substantially higher than the energy obtained under low-pO{sub 2} conditions. The oxide VO{sub 2} was the predominant phase that formed in both alloys when exposed to pO{sub 2} levels of 6.6 x 10{sup {minus}4} to 0.1 torr. V{sub 2}O{sub 5} was the primary phase in specimens exposed to air and to pure O{sub 2} at 760 torr. The implications of the increased O concentration are ...
Date: April 3, 2000
Creator: Natesan, K. & Uz, M.
Partner: UNT Libraries Government Documents Department

Oxidation behavior of molybdenum silicides and their composites

Description: A key materials issue associated with the future of high-temperature structural silicides is the resistance of these materials to oxidation at low temperatures. Oxidation tests were conducted on Mo-based silicides over a wide temperature range to evaluate the effects of alloy composition and temperature on the protective scaling characteristics and testing regime for the materials. The study included Mo{sub 5}Si{sub 3} alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi{sub 2}-Si{sub 3}N{sub 4} composites that contained 20--80 vol.% Si{sub 3}N{sub 4} were evaluated at 500--1,400 C.
Date: April 3, 2000
Creator: Natesan, K. & Deevi, S. C.
Partner: UNT Libraries Government Documents Department

Development of electrically insulating coatings for service in a lithium environment

Description: Several experiments were conducted to develop electrically insulating CaO coatings on a V-4Cr-4Ti alloy for application in an Li environment. The coatings were developed by vapor phase transport external to Li, and also in-situ in an Li-Ca environment at elevated temperature. In the vapor phase study, several geometrical arrangements were examined to obtain a uniform coating of Ca on the specimens, which were typically coupons measuring 5 to 10 x 5 x 1 mm. After Ca deposition from the vapor phase, the specimens were oxidized in a high-purity argon environment at 600 C to convert the deposited metal into oxide. The specimens exhibited insulating characteristics after this oxidation step. Several promising coated specimens were then exposed to high-purity Li at 500 C for 48--68 h to determine coating integrity. Microstructural characteristics of the coatings were evaluated by scanning electron microscopy and energy-dispersive X-ray analysis. Electrical resistances of the coatings were measured by a two-probe method between room temperature and 700 C before and after exposure to Li.
Date: May 17, 2000
Creator: Natesan, K.; Uz, M. & Wieder, S.
Partner: UNT Libraries Government Documents Department

Corrosion performance of materials for advanced combustion systems

Description: Conceptual designs of advanced combustion systems that utilize coal as a feedstock require high-temperature furnaces and heat transfer surfaces capable of operating at much higher temperatures than those in current coal-fired power plants. The combination of elevated temperatures and hostile combustion environments requires development and application of advanced ceramic materials for heat exchangers in these designs. This paper characterizes the chemistry of coal-fired combustion environments over the wide temperature range of interest in these systems and discusses some of the experimental results for several materials obtained from laboratory tests and from exposures in a pilot-scale facility.
Date: May 1995
Creator: Natesan, K.; Freeman, M. & Mathur, M.
Partner: UNT Libraries Government Documents Department