Mechanisms of Topologically Close-Packed Phase Suppression in an Experimental Ruthenium-Bearing Single-Crystal Nickel-Base Superalloy at 1100 °C

Ruthenium (Ru) suppresses the precipitation of deleterious topologically close-packed (TCP) phases in high refractory content single-crystal Ni-base superalloys. The effectiveness of Ru 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...