Abstract
Hot compression tests were conducted using a Gleeble 3500 thermomechanical simulator at temperatures ranging from 1,000 to 1,200°C with the strain rate ranging from 0.1 to 10 s−1. Electron backscatter diffraction (EBSD) technique was employed by investigating the microstructure evolution during hot deformation. Microstructure observations reveal that deformation temperatures and strain rates have a significant effect on the DRX process. It is found that the fraction and grain size of DRX increase with the decreasing deformation temperature, along with the increasing high-angle grain boundaries (HAGBs). The fraction of DRX first decreases and then increases with the increase of strain rates. It is noted that there are both the nucleation mechanisms of discontinuous dynamic recrystallization (DDRX) and continuous dynamic recrystallization (CDRX) during the DRX process for Co–Ni–Cr–W–based superalloys. DDRX and CDRX are the primary and subsidiary nucleation mechanisms of DRX, respectively. It is also found that deformation temperatures and strain rates have almost no effect on the primary and subsidiary nucleation mechanisms of DRX. At the temperature above 1,150°C, the complete DRX occurred with the average grain sizes of about 25.32–29.01 μm. The homogeneity and refinement of microstructure can be obtained by selecting the suitable hot deformation parameters.
Highlights
The Co–Ni–Cr–W–based superalloy has excellent ductility, outstanding strength at high temperatures, good resistance to hostile environments, and weldability
Microstructure observations reveal that deformation temperatures and strain rates have a significant effect on the DRX process
The grain boundaries with misorientation angles below 10° are defined as low-angle grain boundaries (LAGBs)
Summary
The Co–Ni–Cr–W–based superalloy has excellent ductility, outstanding strength at high temperatures, good resistance to hostile environments, and weldability It is suitable for various assembly applications in the aerospace industry. It is widely used in the combustion tank, transition tube, and afterburner of military and commercial gas turbine engines (Haynes International, 2020; Bhanu et al, 1997). In order to obtain excellent properties, it is very important to control the microstructure of the alloy during hot deformation (Cai et al, 2007). The control of the microstructure is of great significance to optimize the final properties of products
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