Effect of heat treatment on mechanical property and microstructure of a powder metallurgy nickel-based superalloy

In this study, single and multi-step aging treatments (SAT and MAT) following a super-solvus solution treatment were employed to tailor the mechanical property of a prototypical powder metallurgy (PM) nickel-based superalloy. Vickers hardness and tensile test at room temperature were used to evaluate the mechanical properties after different heat treatments. Microstructural evolution after heat treatments and tensile tests were revealed through scanning electron microscope (SEM) and electron backscatter diffraction (EBSD) techniques. Our results show that the MAT with a stabilization at 650 degrees C for 24 h between the solution and aging assists to achieve the highest strength corresponding to microstructure of bimodal distribution of y' precipitates. The associated mechanism for variation in microstructures and mechanical properties are discussed based on thermodynamic calculations and precipitation strengthening theory. In addition, an empirical relationship between Vickers hardness and tensile strength of nickel-based superalloys is examined which is believed to be assistance for rapid evaluating mechanical response of materials with different microstructures.