SUMMARY OF THE SEVENTH MEETING OF THE REFRACTORY COMPOSITES WORKING GROUP
Information on refractory composites for use above 2500 deg F is summarized. Reports are concerned with protective coatings, insulating ceramics, materials for rocket thrust chambers, dispersion strengthening of metals, joining of refractory materials, and testing techniques. The problem of accelerated failure of silicide coatings under conditions of very low air pressure at high temperatures is studied. Although the maximum temperature capability of most silicide coatings is reduced about 50 theta deg at low air pressures, several coatings can protect molybdenum for 1/2 hr at 2800 to 3000 deg F under these conditions. The tin-aluminum coating also is susceptible to early failure at reduced pressure. An evaluation of the mechanical properties of 6-mil foils of D- 36, B-68, and TZM coated with commercial coatings demonstrated that some coatings seriously degrade substrate mechanical properties. Research on thermal- protection systems for re-entry vehicles whose surface temperatures reach from 3300 to 5500 deg F has resulted in agreement upon oxide coatings and thick metal- reinforced oxide composites. Simple plasmaarc-sprayed oxide coatings have demonstrated adequate oxidation resistance, but their structural stability in cyclic thermal exposure is inferior to metal-reinforced oxide. Thin unreinforced oxide coatings tend to spall in tests involving cyclic heating. A metal- reinforced oxide composite (reinforcement welded to substrate) has survived cyclic tests such as five 3-minute exposures at 4500 deg F without failing. A new carbon material called glassy carbon has demonstrnted better oxidation resistance than pyrolytic graphite at very high temperatures. The erosion resistance of pyrolytic graphite coatings on regular graphite in rocket firing tests using solid propellants is encouraging. There is considerable interest in fabricating small radiation-cooled rocket thrust chambers by plasma arc spraying. The design concept of internal reinforcement of sprayed-metal rocket chambers with wrought ductile wife appears impractical because of poor bonding and porosity around the wire. (auth)
- Research Organization:
- Battelle Memorial Inst. Defense Metals Information Center, Columbus, Ohio
- NSA Number:
- NSA-17-034320
- OSTI ID:
- 4679543
- Report Number(s):
- DMIC-184
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ALUMINUM
CARBON
CERAMICS
COATING
DISPERSIONS
EROSION
FAILURES
GRAPHITE
HEAT TREATMENTS
HIGH TEMPERATURE
JOINTS
MECHANICAL PROPERTIES
METALS
METALS, CERAMICS, AND OTHER MATERIALS
MOLYBDENUM
OXIDES
PRESSURE
PYROLYSIS
RADIATIONS
REFRACTORIES
ROCKETS
SILICIDES
SPACE VEHICLES
SPUTTERING
TESTING
THERMAL INSULATION
TIN