Search NASA⌕ Search

SEARCH · Search NASA

Results for “High-temperature behavior”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Superalloy eutectic composites with the VI A refractory elements - Cr, Mo and W

The paper discusses the phase equilibria for the ternary systems NiAlCr, NiAlMo, and NiAlW, with emphasis on reactions from the liquid state, although some of the solid state reactions are mentioned. It is shown that eutectics in the Ni-Al-refractory element (Cr, Mo, W) systems offer the potential for high-temperature turbine blade and vane applications. In particular, it is shown that the phase diagrams of these ternary systems can be manipulated to alter the eutectic phases and morphologies by simple quaternary alloying modifications. The resultant combination of chemistry and structure can be controlled to ensure a behavior that is well-matched to hot section component materials requirements.

Jackson, M. R.↗
NASA NTRS1978

Emission-line spectra of two active regions on the solar limb - 1175-1940 A

Skylab emission-line spectra (1175 to 1940 A) of two active regions on the solar limb are examined. Electron densities for the active regions are derived using the intensity ratios of selected intersystem and allowed lines. The intensity ratios in the active regions are compared with those observed previously in quiet-sun and coronal-hole regions. The behavior of coronal forbidden lines relative to transition-zone lines is discussed along with the solar continuum intensities near and above the limb. These continuum intensities are then compared with those at similar slit positions for the quiet sun and the previously studied coronal hole. The active-region data are found to be consistent with either (1) multithermal loops with the high-temperature plasma occupying the tops of the loops or (2) nearly isothermal loops with the hotter loops extending to higher altitudes.

Feldman, U.↗
NASA NTRS1974

The effects of composition on mechanical properties of W-4Re-Hf-C alloys

Studies were made of the effects of alloy composition on the mechanical behavior of as-worked W-4Re-Hf-C alloys containing up to about 0.8 mol % Hfc. Extracted second-phase particles were analyzed and related to alloy composition and creep strength. While strengthening is attributed to HfC particles, the presence of excess hafnium or carbon (above the calculated amounts for stoichiometric HfC) in swaged W-4Re-Hf-C alloys generally causes a reduction of the high-temperature (1930 C) tensile strength; maximum creep strength is, however, indicated for alloys with a slight (about 0.05 to 0.1 at. %) excess of hafnium. Particle strengthening is reduced by WC in solid solution with HfC for allow compositions with an excess of carbon. The low-temperature ductility of worked W-4Re-Hf-C alloys appears to be far more dependent on the amount of excess C or Hf present than on the HfC particle content in the range studies.

Witzke, W. R.↗
NASA NTRS1980

Parametric study of an acoustic levitation system

The performance of an acoustic levitation system designed for the containerless processing of materials and consisting of a St. Clair generator and a reflector arranged in a six-axis configuration, is examined in order to define critical parameters of high-temperature systems and limitations of earth-based devices. The fields and forces along the axis of the system are measured and the forces are plotted versus body volume. It is found that for a range of shapes and sizes the levitation force is roughly proportional to body volume until the characteristic 'diameter' reaches a value of about lambda/2. A significant (i.e., factor of four) enhancement in the levitation force is obtained by curving the faces of the driver and reflector. In addition, the behavior of liquid materials in the acoustic fields is studied, and the radius at which the deformation of a levitated drop occurs is calculated.

Oran, W. A.↗
NASA NTRS1975

Behavior of some singly ionized, heavy-ion impurities during compression in a theta-pinch plasma

The introduction of a small percentage of an impurity gas containing a desired element into a theta-pinch plasma is a standard procedure used to investigate the spectra and atomic processes of the element. This procedure assumes that the mixing ratio of impurity-to-fill gases remains constant during the collapse and heating phase. Spectroscopic investigations of the constant-mixing-ratio assumption for a 2% neon and argon impurity verifies the assumption only for the neon impurity. However, for the 2% argon impurity, only 20 to 25% of the argon is in the high-temperature compressed plasma. It is concluded that the constant-mixing-ratio assumption is not applicable to the argon impurity.

Jalufka, N. W.↗
NASA NTRS1978

Static and dynamic cyclic oxidation of 12 nickel-, cobalt-, and iron-base high-temperature alloys

Twelve typical high-temperature nickel-, cobalt-, and iron-base alloys were tested by 1 hr cyclic exposures at 1038, 1093, and 1149 C and 0.05 hr exposures at 1093 C. The alloys were tested in both a dynamic burner rig at Mach 0.3 gas flow and in static air furnace for times up to 100 hr. The alloys were evaluated in terms of specific weight loss as a function of time, and X-ray diffraction analysis and metallographic examination of the posttest specimens. A method previously developed was used to estimate specific metal weight loss from the specific weight change of the sample. The alloys were then ranked on this basis. The burner-rig test was more severe than a comparable furnace test and resulted in an increased tendency for oxide spalling due to volatility of Cr in the protective scale and the more drastic cooling due to the air-blast quench of the samples. Increased cycle frequency also increased the tendency to spall for a given test exposure. The behavior of the alloys in both types of tests was related to their composition and their tendency to form scales. The alloys with the best overall behavior formed alpha-Al2O3 aluminate spinels.

Barrett, C. A.↗
NASA NTRS1972

Ar40-Ar39 systematics in rocks and separated minerals from Apollo 14.

The Ar40-Ar39 dating technique has been applied to separated minerals (plagioclase, pyroxene, quintessence and an 'ilmenite' concentrate), and whole rock samples of Apollo 14 rocks 14310 and 14073. Plagioclase shows the best gas retention characteristics, with no evidence of anomalous behavior and only a small amount of gas loss in the initial release. Ages determined from the plagioclase of 14310 and 14073 are (3.87 plus or minus 0.05) and (3.88 plus or minus 0.05) AE respectively. Low apparent ages at low release temperatures, which are frequently observed in whole rock Ar40-Ar39 experiments on lunar basalts, are shown to be principally due to gas loss in the high-K interstitial glass (quintessence) phase, confirming earlier suggestions. The decrease in apparent ages in the high-temperature release previously observed in several total rock samples of Apollo 14 basalts has been identified with the pyroxene. Plagioclase is also found to be the most suitable mineral for the determination of cosmic ray exposure ages, and exposure ages of 280 and 113 m.y. are found for 14310 and 14073, respectively, indicating that these rocks, which are very similar in many respects, have different exposure histories.

Turner, G.↗
NASA NTRS1972

Viscous flow behavior of lunar compositions 14259 and 14310.

The flow characteristics of lunar compositions 14310 and 14259 have been determined over a wide range of viscosity. The temperature ranges covered by the measurements are 1270 to 1440 C and 700 to 825 C for the 14310 composition and 1154 to 1431 C and 700 to 820 C for the 14259 composition. Reliable data could not be obtained over the intermediate ranges of temperature because of the occurrence of crystallization. The apparent activation energies for viscous flow in the high-temperature and low-temperature regions are respectively about 60 and 160 kcal/gm at for the 14310 composition and 60 and 170 kcal/gm at for the 14259 composition.

Cukierman, M.↗
NASA NTRS1974

Oxidation behavior of TD-NiCr in a dynamic high temperature environment

The oxidation behavior of TD-NiCr has been studied in static and high-speed flowing air environments at 1100 and 1200 C. It has been found that the stable oxide morphologies formed on the specimens exposed to the static and dynamic environments were markedly different. The faceted crystal morphology characteristic of static oxidation was found to be unstable under high-temperature, high-speed flow conditions and was quickly replaced by a porous NiO 'mushroom' type structure. Also, it was found that the rate of formation of CrO3 from Cr2O3 was greatly enhanced by high gas velocity conditions. The stability of Cr2-O3 was found to be greatly improved by the presence of an outer NiO layer, even though the NiO layer was very porous. An oxidation model is proposed to explain the observed microstructures and overall oxidation behavior of TD-NiCr alloys.

Tenney, D. R.↗
NASA NTRS1976

The case for an unfractionated Pu-244/U-238 ratio in high-temperature condensates

The coarse-grained, Ca-rich inclusions in the Allende meteorite are the highest-temperature condensates from the cooling solar nebula and, as such, the oldest solid objects in the solar system. All refractory elements with condensation points above the accretion temperature of the inclusions whose concentrations in them have been measured are seen to be present in the inclusions in unfractionated proportion to one another relative to Cl chondrites when data are averaged for a large number of inclusions. Observational data for U and theoretical data for both U and Pu suggest that these elements exhibited refractory behavior in the solar nebula. An experiment is proposed in which fissiogenic Xe and U contents are measured in a suite of these inclusions to obtain the Pu-244/U-238 ratio of the solar system at the time of initial condensation with an uncertainty of plus or minus 15%.

Ganapathy, R.↗
NASA NTRS1978

Coronal gas in the Galaxy. I - A new survey of interstellar O VI

Ultraviolet spectra of 40 O- and B-type stars have been intensively scanned in the vicinity of the O VI transitions at 1032 and 1038 A with the Copernicus satellite. This survey of the high-temperature (log T about 5.5) phase of interstellar gas is an extension of the earlier observations of interstellar O VI by Jenkins and Meloy (1974), bringing the total coverage up to 72 stars. Except for a few distant stars, the overall quality of the present data surpasses that of the earlier work. Plots of absorption optical depths versus radial velocity are presented for both transitions in each star. Total column densities (or their upper limits), velocity centroids, and velocity widths have been extracted from the profiles and tabulated, with the results of Jenkins and Meloy (1974) included. Qualitatively, the highly variable O VI densities and velocities seem to exhibit no systematic patterns or regional trends; there is no recognizable correlation in the behavior of coronal gas with pronounced features of galactic structure.

Jenkins, E. B.↗
NASA NTRS1982

Overview of high-temperature materials for high-energy space power systems

The current state of technology and some of the more pressing research needs and challenges associated with the possible use of high temperature materials in future high energy space power systems are discussed. Particularly, emphasis is on the need to improve and quantify the fundamental understanding of the effects of the following: (1) fast neutron radiation on the properties and behavior of nuclear reactor fuels and claddings; and (2) long term, high temperature, space (vacuum) exposure on the properties of refractory metals considered for use as structural materials in various power conversion systems.

Saunders, N. T.↗
NASA NTRS1984

Materials for high-temperature thermoelectric conversion

The development of materials for high temperature thermoelectric energy conversion devices was investigated. The development of new criteria for the selection of materials which is based on understanding of the fundamental principles governing the behavior of high temperature thermoelectric materials is discussed. The synthesis and characterization of promising new materials and the growth of single crystals to eliminate possible problems associated with grain boundaries and other defects in polycrystalline materials are outlined.

Feigelson, R. S.↗
NASA NTRS1983

Tungsten-fiber-reinforced superalloy composite, high-temperature component design considerations

Tungsten fiber reinforced superalloy composites (TFRS) are intended for use in high temperature turbine components. Current turbine component design methodology is based on applying the experience, sometimes semiempirical, gained from over 30 years of superalloy component design. Current composite component design capability is generally limited to the methodology for low temperature resin matrix composites. Often the tendency is to treat TFRS as just another superalloy or low temperature composite. However, TFRS behavior is significantly different than that of superalloys, and the high environment adds consideration not common in low temperature composite component design. The methodology used for preliminary design of TFRS components are described. Considerations unique to TFRS are emphasized. Previously announced in STAR as N82-21259

Winsa, E. A.↗
NASA NTRS1984

Elevated temperature compressive steady state deformation and failure in the oxide dispersion strengthened alloy MA 6000E

The compressive flow strength-strain rate behavior of the oxide-dispersion-strengthened alloy MA 6000E has been studied in the temperature range 1144-1366 K, with strain rates ranging from 2.1 x 10 to the -5th to 2.1 x 10 to the -7th per s. It is found that the inherent strength of the alloy is essentially the same in all test directions and that the low strength observed in tensile tests results from the inability of grain boundaries to support high tensile stresses. The failure of MA 6000E under high-temperature, slow plastic flow conditions is shown to be the result of concentrated slip. Slow plastic deformation in MA 6000E can be described by a threshold stress model of creep where threshold stresses are calculated from relatively fast testing procedures and the effective stress exponent for creep is assumed to be 3.5.

Whittenberger, J. D.↗
NASA NTRS1984

Nonlinear analysis for high-temperature multilayered fiber composite structures

A unique upward-integrated top-down-structured approach is presented for nonlinear analysis of high-temperature multilayered fiber composite structures. Based on this approach, a special purpose computer code was developed (nonlinear COBSTRAN) which is specifically tailored for the nonlinear analysis of tungsten-fiber-reinforced superalloy (TFRS) composite turbine blade/vane components of gas turbine engines. Special features of this computational capability include accounting of; micro- and macro-heterogeneity, nonlinear (stess-temperature-time dependent) and anisotropic material behavior, and fiber degradation. A demonstration problem is presented to mainfest the utility of the upward-integrated top-down-structured approach, in general, and to illustrate the present capability represented by the nonlinear COBSTRAN code. Preliminary results indicate that nonlinear COBSTRAN provides the means for relating the local nonlinear and anisotropic material behavior of the composite constituents to the global response of the turbine blade/vane structure.

Hopkins, D. A.↗
NASA NTRS1985

Experimental observation of transition behavior on a flat plate

In studying transition behavior a shock tube and tunnel were used to produce high temperatures, and thin-film platinum heat gauges were used to measure local heat flux as well as to detect the transition of the laminar boundary layer over a flat plate and a cone. Initial investigations were conducted in the hypersonic shock tunnel to obtain high-temperature information for the development of an ICBM nose cone. Shock Mach numbers as large as 50 with a temperature of 15,000 K after the incident wave were produced in the driven tube. Shock tubes are used to investigate the heat transfer over various surfaces to 2500 K for the development of future gas turbines.

Nagamatsu, H. T.↗
NASA NTRS1985

Lewis' enhanced laboratory for research into the fatigue and constitutive behavior of high temperature materials

Lewis Research Center's high temperature fatigue laboratory has undergone significant changes resulting in the addition of several new experimental capabilities. New materials testing systems have been installed enabling research to be conducted in multiaxial fatigue and deformation at high temperature, as well as cumulative creep-fatigue damage wherein the relative failure-life levels are widely separated. A key component of the new high-temperature fatigue and structures laboratory is a local, distributed computer system whose hardware and software architecture emphasizes a high degree of configurability, which in turn, enables the researcher to tailor a solution to the problem at hand.

Mcgaw, Michael A.↗