Abstract
The stress-strain curves for nickel-based superalloy were obtained from isothermal hot compression tests at a wide range of deformation temperatures and strain rates. The material constants and deformation activation energy of the investigated superalloy were calculated. The accuracy of the constitutive equation describing the hot deformation behavior of this material was confirmed by the correlation coefficient for the linear regression. The distribution of deformation activation energy Q as a function of strain rate and temperature for nickel-based superalloy was presented. The processing maps were generated upon the basis of Prasad stability criterion for true strains ranging from 0.2 to 1 at the deformation temperatures range of 900–1150 °C, and strain rates range of 0.01–100 s−1. Based on the flow stress curves analysis, deformation activation energy map, and processing maps for different true strains, the undesirable and potentially favorable hot deformation parameters were determined. The microstructural observations confirmed the above optimization results for the hot workability of the investigated superalloy. Besides, the numerical simulation and industrial forging tests were performed in order to verify the obtained results.
Highlights
The hot deformation of nickel-based superalloys is often associated with the difficulty of selecting optimal parameters of processing
The main difficulties with processing such alloys at low deformation temperatures are connected with excessively high flow stresses while high deformation temperatures are accompanied by rapid grain growth [1]
Chang et al [9] noted a noticeable decrease in the strength of this alloy at the temperature of 760 ◦ C because of the solution of γ0 phases and good strength stability at the temperatures not exceeding 649 ◦ C
Summary
The hot deformation of nickel-based superalloys is often associated with the difficulty of selecting optimal parameters of processing. The main difficulties with processing such alloys at low deformation temperatures are connected with excessively high flow stresses while high deformation temperatures are accompanied by rapid grain growth [1]. One such superalloy is Waspaloy, characterized by high resistance to creep fatigue, corrosion resistance, and high strength at high temperatures. Yao et al [10] indicated insignificant changes in γ0 precipitations in the microstructure of Waspaloy at 650 ◦ C and their partial dissolution with the instability of the secondary γ0 at 700 ◦ C during stress rupture testing. Kearsey et al [11] noted the dwell
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