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.

Automated summary

The porosity of nickel-base single crystals (NBSXs) is a casting problem that significantly affects their fatigue life. This paper proposes a porosity-distribution-related life prediction method to quantify the porosity effect. The size distribution of porosity in a NBSX is measured and regressed, showing that Feret's diameter follows a modified logarithmic normal distribution. The proposed method expresses the relationship between applied stress, porosity size, and lifetime. The disperse band of the S-N curve is investigated based on the probability distribution of porosity size, and the predicted S-N curve agrees well with experimental data.