Effect of alloying, rapid solidification, and surface kinetics on the high-temperature environmental resistance of niobium. Technical report, January 1987-January 1988

Technical Report · Fri Jan 08 04:00:00 EST 1988

OSTI ID:6965199

Perkins, R A; Meier, G H; Miller, R A; Chiang, K T

An improved understanding of factors governing the selective oxidation of aluminum to form continuous alumina scales on modified niobium-aluminum alloys was established. It was demonstrated that highly protective alumina scales can be formed on niobium-titanium-chromium-vanadium-aluminum alloys without transient oxidation products at temperatures of 1400 to 1600 C in air. Aluminum content was identified as the critical factor controlling single layer alumina formation. It was also shown that the N/sub Al/(crit) for the formation of a continuous alumina scale is 0.375 to 0.38 at 1400 C, decreasing slightly with increased Nb-Ti ratio in the alloy. A fourth element must be added to niobium-titanium-aluminum for effective alumina formation. It has been established that this element should be from a group that can reduce the solubility-diffusivity at 1400 - 1600 C. Alumina can be formed at 1400 C by substituting V or Ti but a liquid transient oxide is produced. A high rate of transient oxidation relative to alumina formation in this range accelerated transient oxidation and precluded alumina growth instead.

• Research Organization: Lockheed Missiles and Space Co., Inc., Palo Alto, CA (USA). Research and Development Div.
• OSTI ID: 6965199
• Report Number(s): AD-A-192093/3/XAB; LMSC/F-24660
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
CHROMIUM ADDITIONS
CHROMIUM ALLOYS
CORROSION RESISTANCE
DOCUMENT TYPES
ELEMENTS
FLUIDS
KINETICS
LAYERS
LIQUIDS
METALS
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PROGRESS REPORT
SCALING
SOLIDIFICATION
SURFACES
TITANIUM ALLOYS
TRANSIENTS
VANADIUM ADDITIONS
VANADIUM ALLOYS
VERY HIGH TEMPERATURE