Creep behaviors and effect factors of single crystal nickel-base superalloys

Abstract

The creep behaviors and effect factors of the single crystal nickel-base superalloys during creep are investigated by means of the measurement of the internal friction stress, creep curve and microstructure observation. Results show that the internal friction stress of dislocations motion during steady state creep are enhanced with the increase of the refractory elements and the Ta concentration. The element Ta displays a better effect for stabilizing the volume fraction of γ′ phase than the element Ti during elevated temperature creep, and the element W possesses a better effect of the solution strengthening than the element Mo. The internal friction stress of superalloy may be obviously enhanced with the elements W and Ta concentration. Significant amount of the finer γ′ phase are precipitated in the γ matrix channels of the alloy during creep, which may effectively hinder the dislocations moving in the matrix channel to decrease the strain rate. In the later period of creep, the deformation feature of alloy 1 is 〈1 1 0〉 screw and edge super dislocations shearing into the rafted γ′ phase, but the ones of alloy 4 are 〈1 1 0〉 super dislocations and (1/2)〈1 1 0〉 partial activated in γ′ phase. The different deformation mechanisms during creep are one of the reasons for resulting in the different creep lifetimes of alloys.