Creep Behaviors of DA Casting and Rolling GH4169 Superalloy

After the billet of Casting and Rolling GH4169 alloy was directly aged (DA) treated at 720℃ and 620℃, creep behavior and deformed features of the alloy were investigated by means of the measurement of creep curves and microstructure observation. Results show that the DA Casting and Rolling GH4169 Superalloy displays a lower strain rate during creep and longer lifetimes under the condition of the applied stress of 700 MPa at 650℃, the creep lifetimes of the alloy decrease to 127 h as temperature is elevated to 660℃, and therefore the alloy exhibits an obvious sensitivity of the applied temperatures. During creep, the deformation mechanism of the alloy is thought to be the twinning deformation and slipping of dislocation within the twinning regions. Thereinto, the dislocation slipping of the single and double orientations occur within the twins. As creep enters the tertiary steady state stage, the micro-crack appears on the grains boundaries along the direction vertical to the applied stress axis, and expands along the grain boundary up to fracture.