Influence of Ta content on microstructure and creep behavior of a Ni-Co base disc superalloy

Abstract This study investigated the influence of Ta content (i.e. 0 wt.%, 2 wt.%, and 4 wt.%) on microstructure and creep behavior of a Ni-Co base disc superalloy at 760 °C/480 MPa. It was found that creep rupture life and the minimum creep strain rate showed a trend of first increase and then decrease with the increase of Ta content. The microstructure observations indicated that Ta addition promoted the increase of volume fraction of γ′, the precipitation of MC carbide and η-phase, but inhibited the growth of γ′ and the precipitation of M23C6 carbide at grain boundaries during creep. The mechanisms related to creep behavior were discussed, and it was deemed that the higher γ′ volume fraction, finer size of γ′, larger γ/γ′ misfit, lower atomic diffusion rate, inhibited M23C6 carbide and the palisade-like distribution of η-phase may be responsible for the enhancement of the primary and tertiary creep resistance.