Study on the Evolution of the γ′ Phase and Grain Boundaries in Nickel-Based Superalloy during Interrupted Continuous Cooling

Haiping Wang,Hai Wang,Dong Liu,Haodong Rao,Longxiang Wang,Yanhui Yang,Jungang Nan,Jianguo Wang

doi:10.3390/cryst11121464

Abstract

The formation of the irregular γ′ precipitates in the nickel-based superalloy Waspaloy was investigated during the continuous cooling, which is relevant to the cooling rates and interrupted temperature. The morphology of the γ′ precipitates was observed to change from a dispersed sphere to the flower-like one with the decreasing of the cooling rates. It was found that there are three modes of transportation of the solute atoms involved in relation to the γ′ precipitates: dissolution from the small γ′ precipitates to the γ matrix, diffusion to the large γ′ precipitates from the matrix, and the short distance among γ′ precipitates close to each other. Meanwhile, the slower cooling rates tend to result in the serrated grain boundaries, and the wavelength between successive peaks (λ) and the maximum amplitude (A) are larger with the decreasing of the cooling rates. The content of the low ΣCSL boundaries increases with the decreasing of the cooling rates, which is of great benefit in improving the creep property of the Waspaloy.

Highlights

Waspaloy is widely used in high-temperature applications, such as turbine disks and blades, as well as the nonrotation high-temperature structural parts, such as aero engine casing and rotating parts
The following under continuous cooling from the supsolvus solution temperature (Tsup sup)
The solute atoms that constitute the γ′ precipitates may involve the process of dissolution from the small γ′ precipitates to the γ matrix, diffusing to the large γ′ precipitates from the matrix, and the short distance among γ′ precipitates close to each other

Summary

The Morphology of the γ0 Precipitates under Different Cooling Rates

It exhibits that the γ0 precipitates were randomly and homogenously distributed throughout the γ matrix. It shows that the morphology changes from the spherical to irregular-shaped temperatures are below the Tsup, and the nucleation of the γ′ precipitates takes place flower-like one. (a) 10 °C/min, (b) 5 °C/min, (c) 1 °C/min, (d) 0.25 °C/min

The Morphology of the γ0 Precipitates at Different Interrupt Temperatures

The Morphology of the Grain Boundaries under Different Cooling Rates

The Morphology of the Grain Boundaries under Different Coo

Conclusions