TCP suppression in a ruthenium-bearing single-crystal nickel-based superalloy

Abstract

Ruthenium suppresses the precipitation of deleterious topologically close-packed (TCP) phases in high refractory content single-crystal nickel-based superalloys. The effectiveness of ruthenium as a TCP suppressant appears to be the net effect of its limited solubility in the TCP phase, a lower density of structural growth ledges for atomic attachment at the TCP/matrix interface, and destabilization of the γ′ phase at elevated temperatures. These characteristics combine to limit the growth rates of TCP precipitates and decrease the driving force for their precipitation. Destabilization of the γ′ phase upon the addition of ruthenium is particularly potent due to the sensitivity of the rhenium content in the γ matrix to changes in the γ′ volume fraction.