Influence of Solution Temperature and Cooling Route on High-Temperature Tensile Deformation and Fracture of a Novel Fourth-Generation Powder Metallurgy Ni-Based Superalloy at 830 °C

Fourth-generation powder metallurgy (PM) Ni-based superalloys are being developed for advanced turbine disks requiring high strength, damage tolerance, and elevated service temperatures. Rational heat-treatment design is required to reconcile high-temperature strength and tensile ductility to satisfy the ever-increasing service demands of aero-engines. This work investigates the influences of solution temperature and cooling route on 830 °C tensile behavior of a novel fourth-generation PM Ni-based superalloy under three heat-treatment schedules followed by identical aging. The results show that the 1190 °C/OQ condition achieves the highest mean elongation of 17.00 ± 0.00% and a UTS of 1093.2 ± 2.0 MPa. Increasing the solution temperature to 1210 °C under OQ raises the mean UTS to 1194.7 ± 7.3 MPa, while the mean elongation decreases to 6.67 ± 2.02%. The 1190 °C/AC condition exhibits a mean elongation of 3.83 ± 0.29% and a UTS of 1066.3 ± 7.3 MPa. EBSD and TEM reveal distinct deformation modes: grain-boundary-localized damage for 1190 °C/AC, broadly distributed intragranular plasticity for 1190 °C/OQ, and band-type strain localization for 1210 °C/OQ. The differences in tensile ductility are associated with the spatial distribution of plastic strain and grain-boundary damage resistance; neither average γ′ size nor the slip-compatibility factor m′ alone reproduces the measured ductility ranking. These findings provide a mechanistic basis for heat-treatment control of this novel fourth-generation PM superalloy.