Effects of Heat Treatment on the Mechanical Behavior of Udimet 720 Nickel-Based Superalloy

The microstructure formation influences the mechanical properties of the nickel-based superalloys. The presence of gamma' in the matrix leads to dramatic changes in mechanical properties. The characteristics of gamma', including volume fraction, size, and morphology, help determine the strength of the superalloys. The alloy's preparation methods and the heat treatment cycles can alter the characteristics of the gamma' and influence the mechanical properties of the alloys. In the present study, various heat treatment conditions are applied for Udimet 720 to investigate their effect on the properties. The tensile and creep properties of the hot isostatic pressed Udimet 720 are evaluated with several heat treatment conditions. The heat treatment conditions of 800 degrees C for a 1000h cycle were applied to investigate the microstructural and mechanical properties. Mainly, the tensile and creep-rupture properties were obtained up to 704 degrees C. It was observed that the thermal exposure influenced the microstructure characteristics and affected accordingly that the tensile and creep-rupture properties have deteriorated. It is due to the presence of the sigma phase (sigma), which consumed and descended the portion of the foremost strengthening precipitate gamma'. Also, the creep strain rate and the minimum creep rate were reduced by forming the sigma phase in the heat-treated substrates. The acoustic emission system was used to detect the stability of the creep stress of the alloy at different heat treatment conditions and to predict the early failure cracks.