CARBIDE COATINGS ON GRAPHITE

Technical Report · Fri Jun 28 04:00:00 EDT 1957

DOI:https://doi.org/10.2172/4265033· OSTI ID:4265033

Blocher, Jr., J. M.; Ish, C. J.; Leiter, D. P.; Plock, L. F.; Campbell, I. E.

A method has been developed for the uniform coating of graphite tubes with carbides of niobium, tantalum, and zirconinm by thermal decomposition of their respective halide vapors. Conditions of coating temperature and pressure are so chosen as to prevent the deposition of metal, but to permit the formation of the carbide as rapidly as carbon can diffuse to the surface. If the carbon diffusion can be made the rate-limiting step, the coating process becomes self- regulating and uniform thickness results. The limits of the temperature-pressure range have been determined experimentally for the thermal decomposition of zirconium iodide and of the chlorides and bromides of niobium, tantalum, and zirconium. With the successful development of coating equipment and definition of conditions, 99 blowpope test specimens were coated with uniform, continuous, and adherent layers of the carbides in three ranges of thickness, light (0.001 in.), medium (0.005 in.), and heavy (0.01 in.). Determinatlons were made of the coefficient for the diffusion of carbon in zirconium carbide as a function of temperature. Exploratory work on small specimens of graphite impregnated with 7 wt.% uranium indicated that the coating results were essentially unchanged, but that loss of uranium occurred. Means of avoiding the loss of uraninm are discussed. (auth)

• Research Organization: Battelle Memorial Inst., Columbus, Ohio
• DOE Contract Number: W-7405-ENG-92
• NSA Number: NSA-13-003805
• OSTI ID: 4265033
• Report Number(s): BMI-1200
• Country of Publication: United States
• Language: English

Related Subjects

CARBON
COATING
DECOMPOSITION
DIFFUSION
GRAPHITE
HALIDES
IMPREGNATION
LAYERS
LOSSES
MATERIALS TESTING
METALLURGY AND CERAMICS
NIOBIUM CARBIDES
NIOBIUM COMPOUNDS
PIPES
PRESSURE
SURFACES
TANTALUM CARBIDES
TANTALUM COMPOUNDS
TEMPERATURE
THICKNESS
TUBES
URANIUM
VAPORS
ZIRCONIUM CARBIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM IODIDES