Oxidation of Udimet 500

Abstract

The oxidation behavior of a nickel-cobalt base alloy containing 19% chromium and 3% aluminum was studied in the temperature range of 760–1200°C. The oxidation process at a given temperature was interrupted after 4, 16, and 64 hr, and every 100 hr thereafter, and the specimens were air-cooled, weighed, and subsequently reheated. The weight gain followed the parabolic law, and the activation energy was 58.8 kcal/mole. The oxide scale consisted of a chromium-rich continuous outer layer and aluminum-rich discontinuous internal oxides at both low and high temperatures. At an intermediate temperature, about 1090°C, the internal oxides became continuous, accompanied by a reduction in oxidation rate. The experimental results are discussed and compared with the information available in the literature.