ENVIRONMENTALLY-ENHANCED CAVITY GROWTH IN NICKEL AND NICKEL-BASED ALLOYS

Environmental factors have a strong effect on the elevated-temperature failure behavior of nickel-based alloys. It has been proposed that th is effect is due to the reactions of oxygen with carbon in the interio r of creep cavities. Such reactions can lead to quite high internal ga s pressures, sufficient to result in substantial increases in the cavi ty growth rates. This hypothesis is investigated by carrying out detai led calculations for a simple system which take into account the coupl ed effects of oxygen diffusion into the cavity and concurrent cavity g rowth. The results show that creep cavity growth may or may not be aff ected by internal, gas-producing reactions, depending upon the nature of the carbon-containing particle, the ratio of the grain boundary oxy gen diffusivity to the self-diffusivity of nickel, and upon other fact ors as well. Copyright (C) 1996 Acta Metallurgica Inc.