Abstract
The precipitation and evolution of γ′ precipitates for various aging heat treatment regimes are studied experimentally in Ni-based single crystal superalloys for both standard heat treatment and long-term aging samples. The focus of this paper is to explore the influence of aging heat treatment on the evolution of the morphology and the distribution of γ′ precipitates. It is demonstrated that the splitting and shrinkage phenomena appear at low aging heat treatment temperatures, and the passivation phenomenon occurs at a high aging temperature of 1200°C. The uniform cubic γ′ particles can be obtained at 1100°C/4 h for the standard heat treatment samples and 1150°C/8 h for the long-term aging ones. This research is beneficial for the study of the rejuvenation aging heat treatment in re-service nickel-based superalloys.
Highlights
As the most important high temperature structural materials, Ni-based single crystal superalloys have excellent high temperature mechanical properties and are widely used as turbine blade materials of modern aviation gas turbine engines
The focus of this paper is to explore the influence of aging heat treatment on the evolution of the morphology and the distribution of γ′ precipitates
The precipitation of a high volume fraction of the long-range ordered L12 type γ′ phase occurs as cubes coherently are embedded in the face-centered cubic Ni-rich phase (γ matrix)
Summary
As the most important high temperature structural materials, Ni-based single crystal superalloys have excellent high temperature mechanical properties and are widely used as turbine blade materials of modern aviation gas turbine engines. A large number of influences of heat treatment on the microstructure of the Ni-based single crystal superalloys have been reported, the systematic research of the effect of temperature and time of the aging heat treatment on the evolution of the microstructure has hitherto been relatively scarce. The microstructure evolution of the DD6 alloy with various working conditions, such as long-term aging, creep, and thermomechanical fatigue, has been deeply studied by the researchers, but the research on the rejuvenation heat treatment process of the DD6 alloy after internal structure degradation is still comparatively rare. For the sake of extending the lifetime of the turbine blades, the microstructure evolution of the DD6 alloy at various aging temperatures and hold times during the rejuvenation heat treatment process is investigated in this paper
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