The evolution of η phase in Ni-Co base superalloys

The evolution of a eta phase (Ni(3)Ti) in Ni-Co base superalloys with different Co and Ti content has been investigated. The results showed that the eta phase existed in the samples with 23.1 wt.%Co and 5.4 wt.%Ti (TMW-3) and also the samples with 28.6 wt.% Co and 7.4 wt.%Ti (TMW-5) heat-treated at the temperature ranges of 1100-1140 degrees C, but not in the samples with 26.3 wt.%Co and 6.0 wt.%Ti (TMW-4). Even in TMW-3 and TMW-5, higher solution temperature (1180 degrees C) can fully reduce the formation of the eta phase. The evolution of the eta phase is complicated and may be related to the Ti content, Ti/Al ratio and alloy's composition. (C) 2007 Elsevier B.V. All rights reserved.