High-temperature creep behaviour of the GTD 111 nickel-based superalloy: deformation mechanisms and activation energy analysis

The creep behavior of the cast nickel-based superalloy GTD 111 was investigated over a range of temperatures and applied stresses relevant to high-temperature turbine applications. Constant-load creep tests were performed to evaluate the evolution of creep strain, minimum creep rate and time to fracture. The dependence of creep resistance on stress and temperature was analyzed to identify the dominant deformation mechanisms governing the creep response. The experimental results reveal a pronounced sensitivity of the minimum creep rate to both applied stress and temperature. The stress exponent and apparent activation energy for creep were determined and discussed in relation to the underlying microstructural features of the alloy. The observed trends indicate that creep deformation in GTD111 is controlled by thermally activated dislocation processes, strongly influenced by the presence and stability of γ′ precipitates and grain-boundary carbides. At higher temperatures and lower stresses, a transition in the creep mechanism is suggested by changes in the stress exponent and damage evolution behavior. The results contribute to a more detailed understanding of the creep mechanisms operating in cast nickel-based superalloys and provide insight into the role of microstructural stability in controlling long-term creep performance.