The creep and fracture behaviour of the cast, nickel-based superalloy, IN100

Abstract

The creep and fracture properties of the cast, multiphase alloy IN100 have been studied over the temperature range 1150–1250 K. The creep behaviour is discussed in terms of the extent to which the γ′ precipitates (∼50–55 vol.%) and carbide particles (∼3–5 vol.%) impede dislocation movement in the γ matrix at various stress levels. The initial acceleration in creep rate during the tertiary stage is shown to be a consequence of changes in the size and distribution of particles during creep. Since the rate of crack development during creep is controlled by the deformation behaviour of the material, a 3-fold improvement in the creep lives of IN100 may be obtained by periodically re-heat-treating the test pieces to re-establish the original particle distribution. Cracks then propagate only at rates characteristic of the initial particle dispersion rather than at the enhanced rates associated with the modified structures developed in uninterrupted tests. However, indefinite lives cannot be achieved since fracture eventually occurs by propagation of oxidized surface-nucleated cracks which cannot be annealed out by reheat-treatment procedures.