Vibration Fatigue Properties and Fracture Mechanism of DD6 Single Crystal Superalloy

Abstract

Room Temperature vibration fatigue S-N curves of single crystal superalloy DD6 with[001] orientation was investigated and room temperature vibration fatigue limit was obtained. The fracture mechanism was studied by OM, SEM and EBSD. The results show that based on S-N method, vibration fatigue limit of DD6 single crystal superalloy with[001] orientation is estimated to be around 337.5MPa. Vibration fatigue fracture presents single or several {111} octahedral slip planes. SEM observations show that fracture has two regions:fatigue source region and the fatigue crack propagation regions, the fatigue cracks initiate at the surface or internal defect of the cross-section with the maximum stress, and exhibits a single source feature, fatigue crack propagation region exhibits quasi-cleavage fracture, no typical fatigue striation feature. Crystal plane slip along {111} is the main deformation mechanism of RT vibration fatigue fracture of single crystal superalloy DD6, quasi-cleavage propagation plane in fracture and quasi-cleavage patterns in microstructure are the main features of RT vibration fatigue fracture of single crystal superalloy DD6.

Keywords

• DD6 single crystal superalloy
• vibration fatigue
• fracture mechanism
• quasi-cleavage plane