The effect of grain boundary serration on creep resistance in a wrought nickel-based superalloy

摘要

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_(23)C_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_(23)C_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.