Influence and analysis of defects on creep behaviors of a single crystal nickel-based superalloy

By means of creep properties measurement and microstructure observation, combined with the finite element method analysis, an investigation has been made into the influence of the cavity with/free cracks on creep behaviors of a single crystal nickel-based superalloy. Results show that during creep, the different evolution features of γ′ phase occur in the regions near the cavity with/free cracks in the single crystal nickel-based superalloy due to the various stress distributions. Therefore, the rafted γ′ phase in the region near the round cavity is transformed into the rafted structure along the direction of 45° angles relative to the stress axis, and the rafted γ′ phase in the region near the cavity-crack is arranged along the direction parallel to the round edge of the cavity in the form of the streamlined model due to the effect of the stress distribution. Compared to the stress value in the region near the round cavity, the bigger von Mises stress value is distributed in the pole b region near the cavity-cracks, and the maximum value of the stress distribution in the pole b region increases as the creep goes on, which may promote the propagation of the cracks along the direction perpendicular to the stress axis. This is thought to be the main reason for the alloy with the cavity-crack having a shorter creep life.