Ni-based superalloys with enhanced environmental resistance at high temperatures are crucial for advanced gas turbine engines. The new polycrystalline nickel-based superalloy has excellent mechanical properties, but as a low-Cr, high-alloying superalloy, its environmental resistance has never been investigated. The hot corrosion behavior of the nickel-based superalloy under molten salt conditions and its effect on its tensile properties were investigated in this paper. The results showed the following: The diffusion of the Cr, Al, and Ni elements governs the majority of the corrosion process, resulting in the production of an environmentally damaged organization with internal sulfidation and surface oxidation. The Wagner model predicts the inability to form a dense Al oxide scale on the surface because the crucial generation condition of external Al oxides is not met. In addition, the growth stress in the damage scales is the main cause of cracking and spalling in the isothermal corrosion process. Due to the increased local stress concentration brought on by this environmental degradation, the sulfide scale acts as a fracture source, guiding the matrix cracking and influencing the tensile properties of the alloy.

This study systematically investigated the microstructural evolution and mechanical properties of GH4780 superalloy under various solution treatment conditions. Experimental results reveal a strong temperature dependence of grain growth kinetics, with the average grain diameter increasing from approximately 20 μm to 194 μm as the solution temperature rises from 1020 °C to 1110 °C. Mechanical testing demonstrates that grain coarsening reduces the yield strength by 19% at room temperature (from 920 MPa to 743 MPa) and by 9.5% at 760 °C (from 707 MPa to 640 MPa), primarily due to decreased grain boundary density and enhanced dislocation mobility. High-temperature deformation mechanisms were characterized, showing that the reduced grain boundary area facilitates dislocation motion while compromising strength. Furthermore, a grain growth kinetic model was developed, providing a quantitative prediction of microstructural evolution. These findings offer significant guidance for improving the high-temperature performance of GH4780 superalloy by optimizing heat treatment processes.

In this paper, the as-cast microstructure, microsegregation, the kinetics of secondary precipitation phase, and thermal deformation behavior in Ta-containing GH4151 alloy (Ta-GH4151) were studied using optical microscope (OM), scanning electron microscope (SEM), electron probe (EPMA), differential scanning calorimetry (DSC), mechanical testing and simulation (MTS) and electron backscattering diffraction (EBSD). The results indicate that Ti, Ta, Nb and Mo are mainly distributed in the interdendritic region and exhibit negative segregation characteristics, while Cr and W are mainly distributed in the dendritic arm region and exhibit positive segregation characteristics. The initial dissolution temperatures for Laves phase, eutectic (γ + γ′) and η phase are 1140–1150 °C, 1150–1160 °C and 1170–1180 °C, respectively. The diffusion activation energies of Nb, Ta and W are 313 kJ/mol, 323 kJ/mol and 345 kJ/mol, respectively. The hot deformation activation energy of Ta-GH4151 alloy after homogenization is 1694.173 kJ/mol. Based on the constitutive equation and hot processing map, the optimum hot deformation temperature and strain rate range are determined to be 1160–1170 °C/0.3–1 s⁻¹. The addition of Ta not only increases the redissolution temperature of the Laves phase, eutectic (γ + γ′) and η phase but also increases the segregation of Nb, Ta and W, diffusion activation energy and homogenization. The results are expected to provide a more comprehensive understanding of the modification and accelerated application of GH4151 alloy.