OXIDATION RESISTANT COATINGS FOR TANTALUM ALLOYS AND OTHER METALS
Abstract
The effect of coating composition on structural changes and oxidation behavior was studied using a Sn-Al spray-slurry system with tantalum, tantalum alloys, columbium, tungsten and molybdenum. In tests conducted at 3000 F, it was found that increased oxidation protection was significantly related to the thickness of the tin-rich phase at the surface. Refractory metal powder additives plus excess aluminum to form aluminide particles served best to increase the thickness of this phase. Coating composition was optimized, and an extensive evaluation was carried out with Ta-10%W, Ta-30%Cb-7.5%V, and Cb-5 In oxidation tests at 1100 F to over 3000 F protective life was significantly affected by substrate composition, coating thickness and thermal cycling. Tensile and stress rupture data were obtained on coated samples at 2000 to 3000 F and correlated fairly well with data in the literature for uncoated material. Preliminary studies were made of coating stability at air pressures in the micron to millimeter range. Oxidation and diffusion effects were explored by metallographic electron probe and x-ray analysis. A brief study of Ta 10Hf-5W in contact with Al2O3 at elevated temperatures showed that this alloy was unstable in contrast to pure tantalum, Ta-10W, and Ta-30Cb 7.5V, which were quite stable.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1963
- Accession Number
- AD0403810
Entities
People
- L. Sama