Development of γ phase stacking faults during high temperature creep of Ru-containing single crystal superalloys

An unusual deformation mode involving the formation of intrinsic stacking faults in the gamma matrix of experimental Ru-containing gamma-gamma' superalloys with high Co and Re contents during high temperature creep at 950 degrees C/290 MPa has been observed. The morphology, distribution and dependence of these stacking faults on alloy chemistry has been investigated along with their formation mechanism. Additions of Re and Co substantially decrease the stacking fault energy of the 7 matrix. The observed stacking faults in the T matrix form by the dissociation of a/2 < 1 1 0 > matrix dislocations with Burgers vectors perpendicular to the loading direction in the early stages of creep. The dependence of creep properties on elemental additions that influence stacking fault energy is discussed. Published by Elsevier Ltd on behalf of Acta Materialia Inc.