Insights in improving creep resistance of low-cost 2nd-generation nickel based single crystal superalloys at intermediate temperature

Abstract

Generally, interactions of stacking faults (SF) have been considered to have a strengthening effect for single crystal (SX) superalloys during creep at intermediate temperatures. However, results in this work show that V-like SF interactions are more effective than T- or X-like interaction in preventing further expansion of SFs in the experimental Re-low and Re-free SX superalloys. Under the creep condition of 760 °C/780 MPa, dislocations entanglement near concave γ/γ′ interfaces, enrichment of Re atoms along SFs and more V-like SF interactions within γ′ phase are conductive to lowering the creep rate of the Re-low alloy. Finally, based on interface and two-phase evolution, configurations of matrix dislocations as well as the expansion and interactions of SFs, we propose new understandings to improve intermediate-temperature creep resistance for SX superalloys.