Rotary Bending High Cycle Fatigue Behavior of Single Crystal Superalloy DD499 in <111> Orientation

Abstract:

Smooth and notched specimens of single crystal superalloy DD499 in <111> orientation were subjected to rotary bending high cycle fatigue loading at temperatures of 700 and 900 oC in ambient atmosphere. The results show that both fatigue strength and notch sensitivity of smooth specimens of <111>-oriented DD499 alloy are increased at elevated temperature; the fatigue strength of smooth specimens are 355 MPa at 700 oC, and 400 MPa at 900 oC. High cycle fatigue failure of smooth specimens of DD499 alloy at different temperatures is in the form of cleavage fracture with multiple crack initiation sites, which was evidently observed along {111} glide plane. However, for the notched specimens, the cracks propagate towards the central area from notched roots at 700 oC, and cleavage rupture characteristics is just like that of the smooth specimens at 900 oC.