Effect of aging temperature on the fatigue properties of shot-peened single crystal superalloy at intermediate temperature

•Surface recrystallization occurs after shot-peening/aging, leading to a significant decrease in surface hardness.•The recrystallized structure makes the fatigue performance lower than unpeened sample.•Aging increases the dispersion of the fatigue lives of shot-peened specimens of the single-crystal superalloy. After shot peening, single crystal superalloy specimens were subjected to thermal aging at different temperatures for 4 h. The surface layer structures were observed, and the rotary bending fatigue performances with the notched structure at 650 °C were tested. The results showed that the deformed structure of the shot-peened single crystal superalloy surface recovered after aging at 870 °C, exhibiting a little strengthening effect on the fatigue performance. After aging at 1000−1200 °C, recrystallization structures appeared on the surface, and the depth and size of recrystallized grains increased with the aging temperature, decreasing the surface layer hardness. The recrystallized structure introduced by aging at 1200 °C decreased the notch fatigue life of single crystal superalloys by 68.2%.