Effect of Alloying, Rapid Solidification, and Surface Kinetics on the High Temperature Environmental Resistance of Niobium.
Abstract
An improved understanding of factors governing the selective oxidation of aluminum to form continuous alumina scales on modified niobium-aluminum alloys has been established. It has been 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 has been identified as the critical factor controlling single layer alumina formation. It also has been shown that the N sub Al(crit) for the formation of a continuous alumina scale is 0.375 - 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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 08, 1988
- Accession Number
- ADA192093
Entities
People
- Gerald H. Meier
- K. T. Chiang
- R. A. Perkins
- Rachel A. Miller
Organizations
- Lockheed Martin Missiles and Space