RESEARCH ON PHYSICAL AND CHEMICAL PRINCIPLES AFFECTING HIGH TEMPERATURE MATERIALS FOR ROCKET NOZZLES. Quarterly Progress Report

Technical Report · Sun Sep 30 00:00:00 EDT 1962

OSTI ID:4794942

Lowrie, R

7 7 5 5 6 : 7 7 : 9 K 6 9 9 : / 2/, TaC, and TaB/sub 2/ by slowly flowing CO/sub 2/-Ar mixtures was studied at 2250 deg C. From these experiments and similar data on tungsten several generalizations were made. Tungsten showed the lowest linear corrosion rate in the range of CO/sub 2/ partial pressure studied (50 to 400 Torr). From 100 to 400 Torr of CO/sub 2/ HfC had the next lowest linear corrosion rate, The formation and accumulation of nonvolatile oxide coatings on zirconium and hafnium carbides and borides decreased their corrosion rates below those of the other hard metals, Decreasing the porosity also decreased the corrosion rate of all these refractory metals. Progress was made in identifying the solid reaction products remaining on the sample after oxidation by CO/sub 2/ or H/sub 2/O. A single-surface specimen was developed for study of corrosion at high rates of gas flow, under which conditions it would not be possible to maintain quasi-homogeneous conditions around a six-sided sample. A large increase was found in the rate of corrosion of ZTA graphite by a CO/sub 2/Ar mixture on changing the flow conditions approximately from 20 cm/sec to 10,000 cm/sec. At the high velocity there appears to be a chemical attack on the binder phase and physical erosion of the more resistant particles. An analysis was made of the oxidation of tungsten by CO/sub 2/CO-Ar mixtures on the assumptions that the rate is limited by the attainment of chemical equilibrium at the tungsten surface and by the rates of supply and removal of reactants and products. Results for this system, including the inhibition by CO, are in agreement with the analysis. Future work on inhibition by CO is planned using a nozzleshaped sample in an engine simulator. Study of the reactions of hydrogen with graphite and with carbides is proceeding. The results for graphite are concordant with first-order kinetics for the formation (first-order in H/sub 2/) and decomposition (first-order in CH/sub 4/) of methane at the hot carbon surface. Experiments with TiC and NbC were confusing, apparently as a result of contamination of the specimens by oil during grinding, However, in all of the TiC runs and many of the NbC runs no acetylene was detected. This was a very significant difference in behavior from that of graphite, which on reacting with hydrogen under similar conditions produces one hundred times the minimum detectable concentration. The production of other hydrocarbons from these carbides is of the same order of magnitude as from graphite. The mass-spectrometric study of the vaporization of ZrB/sub 2/ was completed. A source of error was detected in the presence of temperature gradients along the crucible, and these were eliminated. All the pressure- temperature data used in the calculations were obtained on the mass spectrometer, so that the instrumental constants cancel out. The average heat of formation of ZrB/sub 2/, assuming DELTA S = DELTA Cp = 0, was near -59 kcal/mole. Large- grained specimens of polycrystalline TiC, which are completely brittle at room temperature, exhibited remarkable ductility in long-term creep tests in the range 1800 to 1700 deg C. One specimen, pulled to fracture, necked to over 90% reduction in area just like a very ductile metal, Stresses of the order of 5000 psi were required to produce creep at a measurable rate near 1600 deg C. Progress was made on the design and construction of apparatus for zone-refining tungsten and for testing it in tension at high temperature without contamination. The thermal expansion of TiC was measured up to 2080 deg C, at which temperature the expansion is 1.80%. Measurements of galvanomatmetic properties were made on NbC/ sub 0.5/N/sub 0.5/, ZrB/sub 2/, and HfB/sub 2/. The Hall coefficient of NbC/sub 0.5/N/sub 0.5/ was found to be smaller than that of NbC, in accord with the view that nitrogen contributes more electrons than does carbon to the energy bands. Considerable effort was devoted to the preparation of solid solutions between carbides. It was demonstrated that solid solutions are formed much more

• Research Organization: Union Carbide Corp. Research Inst., Tarrytown, N.Y.; and Union Carbide Corp. Parma Research Center, Ohio
• DOE Contract Number: DA-30-069-ORD-2787
• NSA Number: NSA-17-000416
• OSTI ID: 4794942
• Report Number(s): NP-12130
• Resource Relation: Other Information: Orig. Receipt Date: 31-DEC-63
• Country of Publication: United States
• Language: English

Related Subjects

METALS, CERAMICS, AND OTHER MATERIALS
ACETYLENES
ARGON
BRITTLENESS
CARBON
CARBON DIOXIDE
CARBON MONOXIDE
CHEMICAL REACTIONS
COATING
CORROSION
CREEP
CRUCIBLES
CRUSHING
DECOMPOSITION
DENSITY
DIFFRACTION
DUCTILITY
ELECTRONS
ENERGY LEVELS
EVAPORATION
EXPANSION
FAILURES
GAS FLOW
GRAPHITE
HAFNIUM BORIDES
HAFNIUM CARBIDES
HALL EFFECT
HEAT TREATMENTS
HIGH TEMPERATURE
HYDROGEN
IMPURITIES
LABORATORY EQUIPMENT
MASS SPECTROMETERS
MATERIALS TESTING
METHANE
NIOBIUM CARBIDES
NIOBIUM NITRIDES
NITROGEN
NOZZLES
OILS
OXIDATION
OXIDES
PLANNING
POROSITY
POWDERS
PREPARATION
PRESSURE
REACTION KINETICS
SOLID SOLUTIONS
STRESSES
SURFACES
TANTALUM BORIDES