Effects of heat treatment on mechanical properties of ODS nickel-based superalloy sheets prepared by EB-PVD

A Y₂O₃ dispersion strengthened nickel-based superalloy sheet (0.15 mm thick) was prepared by electron beam physical vapor deposition (EB-PVD) technology. Different heat treatments were used to improve the mechanical properties of the alloy sheet. Differential thermal analysis (DTA) was used to examine the thermal stability of the as-deposited sheet. Element contents, phase composition and microstructure investigations on as-deposited and heat treated specimens were performed by X-ray fluorescence spectrometer (XRF), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Tensile tests were conducted at room temperature on specimens as-deposited and heat treated. The results show that the as-deposited sheet is composed of equiaxed grains on the substrate side and columnar grains on the evaporation side. The as-deposited sheet shows poor ductility due to micropores between columnar grains. The strength and ductility can be improved effectively by annealing at 800°C for 3 h. For samples treated at 1100°C, the strength drops down due to the precipitates of Y₃Al₅O₁₂ (YAG).