Abstract
Grain boundary serration, as a function of heat treatment parameters, and its effect on creep resistance have been investigated in a wrought nickel-based superalloy Nimonic 263. Grain boundary serration occurs in the absence of adjacent γ′ particles or M 23C 6 when a specimen is slow-cooled from solution treatment temperature. The average amplitude and wavelength of serrations can be controlled without a significant change in grain size and γ′ size by adjusting the heat treatment parameters of solution treatment time and cooling rate. Grain boundary serration leads to changes in M 23C 6 carbide characteristics: from granular to planar morphology, a lowered density, and the coherency pattern to two neighboring grains from consistent to zigzag. Creep resistance improvement due to serration is associated with a lower rate of cavitation and crack propagation through the modification of carbide characteristics, as well as grain boundary configuration.
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