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

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 degrees 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 gamma', the precipitation of MC carbide and eta-phase, but inhibited the growth of gamma' 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 gamma' volume fraction, finer size of gamma', larger gamma/gamma' misfit, lower atomic diffusion rate, inhibited M23C6 carbide and the palisade-like distribution of eta-phase may be responsible for the enhancement of the primary and tertiary creep resistance.

Automated summary

This study found that increasing Ta content influences the creep behavior of a Ni-Co base disc superalloy, leading to a trend of first increasing and then decreasing creep rupture life and minimum creep strain rate. Ta addition promoted the increase of gamma' volume fraction while inhibiting the growth and precipitation of certain carbides.