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Comparison of Crystal Structures of 10 Wrought Heat Resisting Alloys at Elevated Temperatures With Their Crystal Structures at Room Temperatures

Description: Note presenting an investigation to compare the crystal structure of the predominant phase at temperatures of 1200, 1500, and 1800 degrees Fahrenheit in 10 wrought heat-resisting alloys with crystal structure observed at room temperature. The alloys investigated included S-816, S-590, Hastelloy B, 19-9 W-Mo, N-155, 16-25-6, K-42-B, Inconel X, Nimonic 80, and type 347 stainless steel.
Date: November 1947
Creator: Kittel, J. Howard
Partner: UNT Libraries Government Documents Department

Multiple Input Electrode Gap Control During Vacuum Arc Remelting

Description: Accurate control of the electrode gap in a vacuum arc remelting (VAR) furnace has been a goal of melters for many years. The size of the electrode gap has a direct influence on ingot solidification structure. At the high melting currents (30 to 40 kA) typically used for VAR of segregation insensitive Ti and Zr alloys, process voltage is used as an indicator of electrode gap, whereas drip-short frequency (or period) is usually used at the lower currents (5 to 8 kA) employed during VAR of superalloys. Modem controllers adjust electrode position or drive velocity to maintain a voltage or drip-short frequency (or period) set-point. Because these responses are non-linear functions of electrode gap and melting current, these controllers have a limited range for which the feedback gains are valid. Models are available that relate process voltage and drip-short frequency to electrode gap. These relationships may be used to linearize the controller feedback signal. An estimate of electrode gap may then be obtained by forming a weighted sum of the independent gap estimates obtained from the voltage and drip-short signals. By using multiple independent measures to estimate the gap, a controller that is less susceptible to process disturbances can be developed. Such a controller was designed, built and tested. The tests were carried out at Allvac Corporation during VAR of 12Cr steel at intermediate current levels.
Date: January 14, 1999
Creator: Beaman, J.J.; Hysinger, C.L.; Melgaard, D.K. & Williamson, R.L.
Partner: UNT Libraries Government Documents Department

Electron beam melting at high pressures with a vacuum separator/plasma lens

Description: Plasmas can be used to provide a vacuum-atmosphere interface or separation between vacua regions as an alternative to differential pumping. Vacuum-atmosphere interface utilizing a cascade arc discharge was successfully demonstrated and a 175 keV electron beam was successfully propagated from vacuum through such a plasma interface and out into atmospheric pressure. This plasma device also functions as an effective plasma tens. Such a device can be adopted for use in electron beam melting.
Date: December 31, 1995
Creator: Hershcovitch, A.
Partner: UNT Libraries Government Documents Department

Advanced Cast Austenitic Stainless Steels for High Temperature Components

Description: In July of 2002, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory (ORNL) and Caterpillar, Inc. (Caterpillar Technical Center) to develop and commercialize new cast stainless steels invented and initially tested on a prior CRADA. This CRADA is a direct follow-on project to CRADA ORNL-99-0533 for diesel engine exhaust component and gas turbine engine structural component applications. The goal of this new CRADA was to develop and commercialize the newly discovered cast stainless steels (primarily CF8C-Plus) with improved performance and reliability, as lower-cost upgrade alternatives to more costly cast Ni-based superalloys.
Date: October 9, 2008
Creator: Maziasz, P. J.; Shingledecker, J. P.; Evans, N. D. & Pollard, M. J.
Partner: UNT Libraries Government Documents Department

Land-based turbine casting initiative

Description: To meet goals for the ATS program, technical advances developed for aircraft gas turbine engines need to be applied to land-based gas turbines. These advances include directionally solidified and single crystal castings, alloys tailored to exploit these microstructures, complex internal cooling schemes, and coatings. The proposed program to scale aircraft gas turbine casting technology up to land based gas turbine size components is based on low sulfur alloys, casting process development, post-cast process development, and establishing casting defect tolerance levels. The inspection side is also discussed.
Date: December 31, 1995
Creator: Mueller, B.A. & Spicer, R.A.
Partner: UNT Libraries Government Documents Department

Partitioning behavior of alloying elements in PWA 1484

Description: Nominal composition of single-crystal PWA 1484 material is Ni-10.5 at.% Co, 6% Cr, 1.3% Mo, 2.0% W, 12.9% Al, 3.0% Ta, 0.04% Hf, and 1.0% Re. It was examined after standard heat treatment of 4 h at 1304 C, 4 h at 1079 C, and 24 h at 704 C. An atom probe field ion microscope was used. Co, Cr, Mo, W and Re partition to the {gamma} phase and Ni, Al, Ta, and Hf partition to the {gamma}` phase. Atom-by-atom data chains and statistical analysis did not show any evidence of Re clusters in the {gamma} matrix.
Date: August 1, 1996
Creator: Miller, M.K.; Lin, L.S.; Cetel, A.D.; Harada, H. & Murakami, H.
Partner: UNT Libraries Government Documents Department

Methods for preparation of extremely fine superalloy powders and fabrication to superalloy parts. Final report, October 1, 1995--February 15, 1998

Description: The use of reducing agents such as sodium borohydride have been used in a wide variety of chemical reactions from organic compounds synthesis to metal production. In order to reduce metal ions into the metallic state, the solution electrochemical potential must be sufficiently low to allow the metal to accept electrons from the reducing agent. One information source that gives important information regarding the conditions necessary for spontaneous aqueous nickel metal reduction is the electroless nickel plating literature. Although nickel is not the only desired metal, it provides an important starting point in metal reduction, and it is useful because of its resistance to corrosion. The electroless nickel plating literature indicates that sodium hypophosphite, sodium borohydride, and hydrazine are all used as reductants. Sodium hypophosphite is usually used at 30--95 C in a bath containing dissolved nickel sulfate and other additives such as oxalic acid and ammonium chloride. Sodium borohydride is usually used with sodium hydroxide in a similar temperature range. Hydrazine is also used with sodium hydroxide in a similar temperature range. However, in order to make the transition from electroless nickel deposition to spontaneous metal powder production requires different conditions. In this research program, a number of different conditions were examined to determine optimum conditions for the production of metal and metal alloy powders in aqueous solutions.
Date: July 1, 1998
Creator: Natesh, R.
Partner: UNT Libraries Government Documents Department

Nickel based superalloy with improved weldability and oxidation resistance. Fifth quarterly report for the period November 1999 - January 2000

Description: This program is part of the US Department of Energy (DOE) Energy Related Inventions Program (ERIP). The purpose of ERIP is to promote and facilitate the development of energy saving technologies that may not otherwise be developed solely by commercial enterprises. The program has been highly successful in achieving its mission. The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.
Date: February 29, 2000
Creator: Simkovich, George & Whitney, Eric
Partner: UNT Libraries Government Documents Department

Nickel Based Superalloy with Improved Weldability and Oxidation Resistance. Fourth quarterly report for the period July 1999 to October 1999

Description: The aim of this project is to determine and provide technical and economic data to a commercial end user of the alloy so that a full-scale alloy qualification program can be defined and implemented. The object of this project is to define the compositional range for a new alloy that is suitable for evaluation and qualification by a commercial enterprise. Alloy properties that will need to be determined include weldability, oxidation resistance, creep strength, resistance to thermo-mechanical fatigue, microstructure stability, and cost. Test results will be used to finalize the compositional range of an alloy that will undergo a rigorous qualification process.
Date: November 1, 1999
Creator: Simkovich, George & Whitney, Eric
Partner: UNT Libraries Government Documents Department

Microstructural development in PWA-1480 electron beam welds: An atom probe field ion microscopy study

Description: The microstructure development in PWA-1480 superalloy electron beam weld (Ni-11.0 at. % Al-11.5% Cr-1.9% Ti-5.1% Co-4.0% Ta-1.3% W) was characterized. Optical microscopy revealed a branched dendritic structure in the weld metal. Transmission electron microscopy of these welds, in the as-welded condition, showed fine cuboidal (0.05--0.5 {mu}m) L1{sub 2}-ordered {gamma}{prime} precipitates within the y grains. The average volume percentage of {gamma}{prime} precipitates was found to be {approx}5%. Atom probe analyses revealed that the composition of {gamma} matrix was Ni-4.6 at. % Al-25.5% Cr-0.4% Ti-9.4% Co-0.8% Ta-2.9% W and that of {gamma}{prime} precipitates was Ni-17.3 at. % Al-2.6% Cr-2.4% Ti-3.0% Co-7.4% Ta-1.3% W. These compositions were compared with the previous APFIM analyses of commercial PWA-1480 single crystals that had received conventional heat treatments. Small differences were found in the chromium and aluminum levels and these may be due to the nonequilibrium nature of phase transformations that occur during weld cooling. No solute segregation was detected at the {gamma}-{gamma}{prime}interface. The APFIM results were also compared with the thermodynamic calculations of alloying element partitioning between {gamma} and {gamma}{prime} using the ThermoCalc{trademark} software.
Date: December 31, 1995
Creator: David, S.A.; Miller, M.K. & Babu, S.S.
Partner: UNT Libraries Government Documents Department

Gelcasting superalloy powders

Description: Gelcasting is a process for forming inorganic powders into complex shapes. It was originally developed for ceramic powders. A slurry of powder and a monomer solution is poured in to mold and polymerized in-situ to form gelled parts. Typically, only 2-4 wt % Polymer is used. The process has both aqueous and nonaqueous versions. Gelcasting is a generic process and has been used to produce ceramic parts from over a dozen different ceramic compositions ranging from alumina-based refractories to high-performance silicon nitride. Recently, gelcasting has been applied to forming superalloy powders into complex shapes. This application has posed several challenges not previously encountered in ceramics. In particular, problems were caused by the larger particle size and the higher density of the particles. Additional problems were encountered with binder removal. How these problems were overcome will be described.
Date: December 31, 1995
Creator: Janney, M.A.
Partner: UNT Libraries Government Documents Department

Improving the Oxidation Resistance in Advanced Single Crystal Nickel-Based Superalloys for Turbine Applications

Description: The focus of this project was the examination of the role of yttrium and other alloying elements on the microstructure and oxidation performance of improved single crystal nickel-based superalloys for advanced turbine applications. The microstructure and microchemistry of both base and modified alloys and their surface oxides have been measured with state-of-the-art microanalytical techniques (atom probe field ion microscopy) and then correlated with identifying the partitioning behavior of the elemental additions in these superalloys before and after burner rig and engine-test oxidation performance. The overall technical goals included; (1) identifying the partitioning behavior of the elemental additions in these superalloys before and after burner rig and engine tests and the effect on the misfit energy between the phases in the alloys; (2) examining the oxidation performance of these newly-developed alloys; (3) identifying the influence of pre-oxidation processing on the subsequent oxidation performance; and (4) relating the microstructural and microchemical observations to the observed performance of these superalloys. The comparison of the base and modified alloys will produce a better understanding of the interaction between chemistry, structure, and performance in superalloys. In addition, it will lead to optimized alloys with improved performance including enhanced durability in the operating environments at the elevated temperature required to improve energy efficiency. The availability of alloys capable of higher temperature operation will minimize the need for expensive coatings in extreme temperature applications.
Date: July 1, 1999
Creator: Alexander, K.B.; Kenik, E.A.; Miller, M.K.; Lin, L.S. & Cetel, A.D.
Partner: UNT Libraries Government Documents Department

Final Report for Department of Energy Grant No. DE-FG02-02ER45997, "Alloy Design of Nanoscale Precipitation Strengthened Alloys: Design of a Heat Treatable Aluminum Alloy Useful to 400C"

Description: A creep resistant high temperature Al base alloy made by conventional processing procedures is the subject of this research. The Ni-based superalloys have volume fractions of cubic L1{sub 2} phase precipitates near 50%. This is not attainable with Al base alloys and the approach pursued in this research was to add L1{sub 2} structured precipitates to the Al-Ni eutectic alloy, 2.7 at. % Ni-97.3 at. % Al. The eutectic reaction gives platelets of Al{sub 3}Ni (DO{sub 11} structure) in an almost pure Al matrix. The Al{sub 3}Ni platelets give reinforcement strengthening while the L1{sub 2} precipitates strengthen the Al alloy matrix. Based on prior research and the extensive research reported here modified cubic L1{sub 2} Al{sub 3}Zr is a candidate. While cubic Al{sub 3}Zr is metastable, the stable phase is tetragonal, only cubic precipitates were observed after 1600 hrs at 425 C and they hardly coarsened at all with time at this temperature. Also addition of Ti retards the cubic to tetragonal transformation; however, a thermodynamically stable precipitate is desired. A very thorough ab initio computational investigation was done on the stability of L1{sub 2} phases of composition, (Al,X){sub 3}(Zr,Ti) and the possible occurrence of tie lines between a stable L1{sub 2} phase and the Al alloy terminal solid solution. Precipitation of cubic (Al{sub (1-x)}Zn{sub x}){sub 3}Zr in Al was predicted by these computations and subsequently observed by experiment (TEM). To test the combined reinforcement-precipitation concept to obtain a creep resistant Al alloy, Zr and Ti were added to the Al-Ni eutectic alloy. Cubic L1{sub 2} precipitates did form. The first and only Al-Ni-Zr-Ti alloy tested for creep gave a steady state creep rate at 375 C of 8 x 10{sup -9} under 20MPa stress. The goal is to optimize this alloy and add Zn to achieve a thermodynamically stable ...
Date: May 6, 2006
Creator: Fine, Morris E.; Ghosh, Gautam; Isheim, Dieter; Vaynman, Semyon; Knipling, Keith & Liu, Jefferson Z.
Partner: UNT Libraries Government Documents Department

The influence of VAR processes and parameters on white spot formation in Alloy 718

Description: Significant progress has occurred lately regarding the classification, characterization, and formation of white spots during vacuum arc remelting (VAR). White spots have been generally split into three categories: discrete white spots, which are believed to be associated with undissolved material which has fallen in from the shelf, crown, or torus regions; dendritic white spots, usually associated with dendrite clusters having fallen from the electrode; and solidification white spots, believed to be caused by local perturbations in the solidifications conditions. Characteristics and proposed formation mechanisms of white spots are reviewed and discussed in context of physical processes occurring during VAR, such as fluid flow and arc behavior. Where possible, their formation mechanisms will be considered with respect to specific operating parameters. In order to more fully understand the formation of solidification white spots, an experimental program has been begun to characterize the solidification stability of Alloy 718 and variants with respect to changes in growth rate and thermal environment. A description of the experimental program and preliminary results are included.
Date: May 1, 1994
Creator: Damkroger, B. K.; Kelley, J. B.; Schlienger, M. E.; Van Den Avyle, J. A.; Williamson, R. L. & Zanner, F. J.
Partner: UNT Libraries Government Documents Department

Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals

Description: Cast nickel-based superalloys are used for blades in land-based, energy conversion and powerplant applications, as well as in aircraft gas turbines operating at temperatures up to 1100 C, where creep is one of the life-limiting factors. Creep of superalloy single crystals has been extensively studied over the last several decades. Surprisingly, only recently has work focused specifically on the dislocation mechanisms that govern high temperature and low stress creep. Nevertheless, the perpetual goal of better engine efficiency demands that the creep mechanisms operative in this regime be fully understood in order to develop alloys and microstructures with improved high temperature capability. At present, the micro-mechanisms controlling creep before and after rafting (the microstructure evolution typical of high temperature creep) has occurred have yet to be identified and modeled, particularly for [001] oriented single crystals. This crystal orientation is most interesting technologically since it exhibits the highest creep strength. The major goal of the program entitled ''Mechanisms of High Temperature/Low Stress Creep of Ni-Based Superalloy Single Crystals'' (DOE Grant DE-FG02-04ER46137) has been to elucidate these creep mechanisms in cast nickel-based superalloys. We have utilized a combination of detailed microstructure and dislocation substructure analysis combined with the development of a novel phase-field model for microstructure evolution.
Date: March 5, 2009
Creator: Mills, Michael J.
Partner: UNT Libraries Government Documents Department

Alloys for 1000 degree C service in the Next Generation Nuclear Plant NERI 05-0191

Description: The objective of the proposed research is to define strategies for the improvement of alloys for structural components, such as the intermediate heat exchanger and primary-to-secondary piping, for service at 1000 degree C in the He environment of the NGNP. Specifically, we will investigate the oxidation/carburization behavior and microstructure stability and how these processes affect creep. While generating this data, the project will also develop a fundamental understanding of how impurities in the He environment affect these degradation processes and how this understanding can be used to develop more useful life prediction methodologies.
Date: January 15, 2009
Creator: Was, Gary S.; Jones, J.W. & Pollock, T.
Partner: UNT Libraries Government Documents Department

Design data for hollow cathode gas-fed arcs

Description: Engineering information is provided to fabricate and operate equipment for generating hollow cathode arcs. Topics include equipment selection and design, operating procedures, and operating characteristics. Hollow-cathode operating characteristics for a wide range of cathode sizes, gas-flow rates, gas types, and cathode-anode spacings are covered. (auth)
Date: December 19, 1973
Creator: Williams, D.G.
Partner: UNT Libraries Government Documents Department

Cast Alloys for Advanced Ultra Supercritical Steam Turbines

Description: Develop advanced coal-based power systems capable of 45–50 % efficiency at <$1,000/kW (in 2002 dollars). Develop technologies for capture and sequestration of CO2 that result in: • <10% increase in the cost of electricity in an IGCC-based plant • <35% increase in the cost of electricity for pulverized coal boilers Demonstrate coal-based energy plants that offer near-zero emissions (including CO2) with multiproduct production
Date: October 1, 2010
Creator: Holcomb, G. R. & Wang, P.
Partner: UNT Libraries Government Documents Department

Elastic constants of a Laves phase compound: C15 NbCr{sub 2}

Description: The single-crystal elastic constants of C15 NbCr{sub 2} have been computed by using a first-principles, self-consistent, full-potential total energy method. From these single-crystal elastic constants the isotropic elastic moduli are calculated using the Voigt and Reuss averages. The calculated values are in fair agreement with the experimental values. The implications of the results are discussed with regards to Poisson`s ratio and the direction dependence of Young`s modulus.
Date: April 1, 1997
Creator: Ormeci, A.; Chu, F.; Wills, J.M.; Chen, S.P.; Albers, R.C.; Thoma, D.J. et al.
Partner: UNT Libraries Government Documents Department

Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

Description: Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.
Date: November 1, 1996
Creator: Park, J.-H. & Cho, W.D.
Partner: UNT Libraries Government Documents Department

Mechanical and microstructural responses and microcrack formation in titanium aluminides at a wide range of strain rate and temperature

Description: Significant progress has been made in the development of titanium aluminide alloys for high temperature and high performance applications in the last decade. An extensive database on the mechanical and microstructural responses of titanium aluminides under various quasi-static loading conditions has been developed. However, knowledge of the mechanical and microstructural responses of titanium aluminides under dynamic loading conditions remains poorly understood. A systematic investigation of the strain rate and temperature effect on mechanical and microstructural responses, microcrack nucleation and microcrack propagation in three titanium aluminide alloys, a polysynthetically twinned (PST) TiAl crystal, a duplex {gamma}-TiAl alloy and a polycrystalline Ti{sub 3}Al-based alloy, was carried out in this study. The mechanical behavior observed in these three alloys will be interpreted based on the characterized deformation microstructures. Microcrack nucleation and propagation mechanisms will be discussed in detail in terms of the observed mechanical and microstructural responses of these alloys.
Date: December 31, 1996
Creator: Jin, Z.; Cady, C.; Vaidya, R.U.; Butt, D.P.; Gray, G.T. III; Kim, Y.W. et al.
Partner: UNT Libraries Government Documents Department

Weldability and microstructure development in nickel-base superalloys

Description: The integrity of nickel-base superalloy single-crystal welds depends on the weld cracking tendency, weld metal dendrite selection process, stray crystal formation, and macro- and microstructure development. These phenomena have been investigated in commercial nickel-base superalloy single crystal welds. During electron beam and laser beam welding, transverse and longitudinal weld cracking occurred. However, the weld cracking tendency was reduced with preheating. Most of the dendritic growth pattern development in these welds can be explained by a geometric model. However, the welds also contained misoriented stray crystals, which were frequently associated with weld cracks. The formation of stray crystals was related to thermal and constitutional supercooling effects. Fine-scale elemental partitioning between {gamma} and {gamma}{prime} phase was measured with atom-probe field-ion microscopy. Marked differences in partitioning characteristics in two welds were observed and are related to differences in cooling rates. In this paper, the modeling tools available to describe the above are reviewed.
Date: November 1, 1997
Creator: David, S.A.; Babu, S.S. & Vitek, J.M.
Partner: UNT Libraries Government Documents Department