The porosity distribution of nickel-base single-crystal superalloy DD5 and its fatigue life property

The porosity of nickel-base single crystals (NBSXs) is still an unavoidable casting problem that has a significant influence on the fatigue life of NBSXs. In order to quantify the porosity effect, a porosity-distribution-related life prediction method is proposed in this paper. The porosity size in a NBSX was measured, and the size distribution was regressed. The results show that the porosity size that is characterized by Feret's diameter follows a modified logarithmic normal distribution. The relation among the applied stress, porosity size, and lifetime is expressed by using the proposed method. The disperse band of S–N curve is investigated based on the probability distribution of the porosity size. The results show that the predicted S–N curve agrees well with the experimental data.