Creep behavior of powder metallurgy Ni-based superalloys with minor scandium

Abstract

The creep behavior of two PM superalloys, U720Li and RR1000, each alloyed with trace amount of Sc, was systematically investigated. Findings reveal that RR1000 alloy with 0.064 wt.% Sc (R-0.064) demonstrates superior creep resistance compared to U720Li alloy with 0.043 wt.% Sc (U-0.043), at 650 °C and 1000 MPa, and the primary creep mechanisms in both alloys are identified as dislocation shearing and precipitate bypassing. When tested at 700 °C and 700 MPa, the U-0.043 alloy predominantly exhibits micro-twinning and dislocation bypassing, while the R-0.064 alloy engages in extended stacking fault shearing of γ′ precipitate, dislocation bypassing and climb. At 750 °C and 460 MPa, dislocation bypassing and climb emerge as the main creep mechanisms for both alloys.