Bin Hu

To meet the requirement of turbine entry temperature in aircraft engines, single crystal superalloy is widely used in turbine blades and vanes. Diffusion brazing is an important technology to repair cracks and surface degradation in turbine nozzle guide vanes. In this study, single-crystal superalloy has been diffusion brazed using Ni and Co-based braze alloys. The microstructure and mechanical properties of the brazing specimens were investigated comparatively. Ni-based brazed specimens show equivalent high temperature tensile property with the Co-based brazed specimens. While the high-temperature stress rupture life of the Co-based specimens were much higher than that of the Ni-based specimens due to the oxidation resistance of Co-based braze alloy and the interfaces between the MC and γ phases.

A novel Ni₃Al-based single-crystal superalloy was subjected to creep testing at 1200°C under applied stresses ranging from 60 to 100 MPa. The stress-related deformation mechanism was elucidated through creep performance testing and examination of microstructure evolution. The results reveal pronounced stress sensitivity, with creep life decreasing from 360.5 h to 22.6 h as the stress increased from 60 to 100 MPa. Meanwhile, the creep strain during the primary creep stage rises from 0.59% to 1.68%. In contrast, during the steady-state creep stage, a decrease in applied stress from 100 MPa to 60 MPa leads to a significant reduction in the minimum creep rate, which drops from 2.77×10⁻⁷ s⁻¹ to 5.02×10⁻⁹ s⁻¹. This behavior is closely associated with the evolution of the interfacial dislocation network at γ/γ′ interfaces, whose spacing plays a critical role in controlling the steady-state creep rate. Throughout the tertiary creep stage, the degree of topological inversion is markedly enhanced with increasing applied stress. At the same time, a concomitant decline is observed in the number density of γ′ subgrains adjacent to the fracture surface. Under an applied stress of 60 MPa, the predominant creep mechanism is confirmed to be dislocation climb. At 100 MPa, the mechanism transitions to dislocation shearing of the γ′ precipitates. In summary, this study reveals the microstructural evolution and dominant deformation mechanisms under varying stress conditions at 1200℃, providing foundational data for the material selection of turbine blades in advanced aeroengines.

A novel Ni₃Al-based single-crystal superalloy was subjected to creep testing at 1200°C under applied stresses ranging from 60 to 100 MPa. The stress-related deformation mechanism was elucidated through creep performance testing and examination of microstructure evolution. The results reveal pronounced stress sensitivity, with creep life decreasing from 360.5 h to 22.6 h as the stress increased from 60 to 100 MPa. Meanwhile, the creep strain during the primary creep stage rises from 0.59% to 1.68%. In contrast, during the steady-state creep stage, a decrease in applied stress from 100 MPa to 60 MPa leads to a significant reduction in the minimum creep rate, which drops from 2.77×10⁻⁷ s⁻¹ to 5.02×10⁻⁹ s⁻¹. This behavior is closely associated with the evolution of the interfacial dislocation network at γ/γ′ interfaces, whose spacing plays a critical role in controlling the steady-state creep rate. Throughout the tertiary creep stage, the degree of topological inversion is markedly enhanced with increasing applied stress. At the same time, a concomitant decline is observed in the number density of γ′ subgrains adjacent to the fracture surface. Under an applied stress of 60 MPa, the predominant creep mechanism is confirmed to be dislocation climb. At 100 MPa, the mechanism transitions to dislocation shearing of the γ′ precipitates. In summary, this study reveals the microstructural evolution and dominant deformation mechanisms under varying stress conditions at 1200℃, providing foundational data for the material selection of turbine blades in advanced aeroengines.