|About this Abstract
||2017 TMS Annual Meeting & Exhibition
||Gamma (FCC)/Gamma-Prime (L12) Co-Based Superalloys II
||Influence of Replacement of Ta by Nb in a γ/γʹ- structure Co Base Superalloys
||Alex Costa, Marcus Salgado, Eder Lopes, Carlos Nunes, Andre Tschiptschin
|On-Site Speaker (Planned)
The microstructural effects of replacement of Ta by Nb in Co-40Ni-3Ta superalloy with γ/γʹ structure was studied. In the as-cast condition, the Co-40Ni-3Nb alloy showed a dendritic γ-Co grain structure. Inside the γ-Co grains fine γʹ spheroidal precipitates with 15 to 20 nm radius, were identified. Primary precipitates of ” - Co7W6 phase and a Chinese script γ+NbC eutectic structure were found in the interdendritic regions. The alloy was heat-treated by two steps (1250 șC/ 72 h and 1000 șC/ 168 h) that resulted in the precipitation of ” - Co7W6, with different morphologies and sizes, embedded in the γ/γʹ structure. The Nb modified alloy showed greater microstructural heterogeneities. Coarsening of the ” - Co7W6 was also observed when ageing was performed at 1250 șC.