COATINGS FOR REFRACTORY METALS, FORMED BY ANODIC TREATMENT AND BY VAPOR DEPOSITION

Technical Report · Sat Jul 01 04:00:00 EDT 1961

OSTI ID:4803628

Lamb, V A; Sligh, J L

The preparation of anodic coatings on Nb, Ta, Mo, and W was investigated. The object was to modify such coatings by anodically incorporating elements known to form oxidation protective alloys with these refractory basis metals, and to convert the mixed coatings to a high-temperature oxidation protective film by subsequent reduction and sintering. Anodizing was carried out in both aqueous solutions and in molten salts. Successful coatings were not obtained. Attempts to form aluminide coatings by diffusion of electrodeposited aluminum, followed by anodizing, were also unsuccessful. Efforts were therefore turned to the preparation of coatings by combining electrodeposition and vapor deposition. Specifically, chromium silicide coatings, formed by vapor phase siliciding of electrodeposited chromium, were investigated. Sound coatings were not obtained from hydrogen reduction of SiCl/sub 4/ due to chernical displacement reaction with the basis chromium. Siliciding with monomethyl and tetramethyl silane avoided the displacement reaction and yielded sound silicon carbide coatings. However, these coatings failed to provide good oxidation protection at 1100 deg C in air, due to spalling. The differential thermal coefficient of expansion with respect to the basis metal was the probable cause of failure. (auth)

• Research Organization: National Bureau of Standards, Washington, D.C.
• NSA Number: NSA-16-025701
• OSTI ID: 4803628
• Report Number(s): WADD-TR-61-64; AD-269132
• Country of Publication: United States
• Language: English

Related Subjects

ALLOYS
ALUMINUM
ALUMINUM ALLOYS
ANODES
CHROMIUM COMPOUNDS
COATING
DECOMPOSITION
DIFFUSION
ELECTRODEPOSITION
FAILURES
FUSED SALTS
HIGH TEMPERATURE
HYDROGEN
METALS, CERAMICS, AND OTHER MATERIALS
MOLYBDENUM
NIOBIUM
OXIDATION
PREPARATION
REDUCTION
SILANES
SILICIDES
SILICON CARBIDES
SILICON CHLORIDES
SINTERING
SOLUTIONS
STABILITY
TANTALUM
TUNGSTEN
VAPORS
WATER