RESEARCH ON DISPERSION STRENGTHENED COBALT-BASE ALLOYS.
Summary rept. 15 Feb 65-14 Feb 66,
DU PONT DE NEMOURS (E I) AND CO WILMINGTON DE
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Cobalt-base alloys containing fine ThO2 dispersions were processed to round bar by powder metallurgy techniques and evaluated for physical and mechanical properties. The ThO2 dispersion increased the sluggishness of the allotropic transformation in cobalt. Strength at elevated temperature was improved by 1 increased ThO2, 2 a minor 0.2 zirconium addition, and 3 increasing amount of secondary work. Oxidation resistance of the Co-ThO2 and Co-Ni-ThO2 alloys was similar to pure cobalt with scaling rates an order of magnitude greater than TD Nickel at 2200F. A chromium addition improved oxidation behavior. Preliminary evaluation on the chromium-containing alloys gave 2000 F tensile strengths of 10,000 psi or less, lower than on the alloys without chromium. Certain of these alloys with chromium recrystallized on high temperature annealing, and this was accompanied by an increase in 2000 F tensile strength. Author
- Properties of Metals and Alloys