70 巻 (2006) 8 号 p. 678-681
In order to develop new superalloy which can reach higher temperature capabilities beyond Ni-base superalloys, Ni-Al and Ni-Al-Ta superalloys were mixed with a Rh-Nb refractory superalloy which has a higher γ/γ′ eutectic of about 1900°C, and the phase relationships of the Ni-base and Rh-Nb superalloy mixtures were investigated. Three phases of fcc, L12-Ni3Al and B2-AlRh were determined in the alloys of (Rh-17 at%Nb alloy) : (Ni-15.8 at%Al-6.5 at%Ta alloy)=20 : 80 molar proportion at 1300°C. Four phases of fcc, L12-Ni3Al, L12-Rh3Nb and B2-AlRh were confirmed in the alloys of (Rh-17 at%Nb alloy) : (Ni-15.8 at%Al-6.5 at%Ta alloy)=20 : 80 molar proportion at 1100°C. The detected phases of (Rh-17 at%Nb alloy) : (Ni-22 at%Al alloy)=50 : 50 molar proportion both at 1100°C and 1300°C are fcc, L12-Rh3Nb, D022-((Ni, Rh)3Nb) and B2-AlRh. The above three-phase equilibrium system of fcc, L12-Ni3Al and B2 may be applicable to EQ (Equilibrium) bond coat system, since Al in B2 phase has a good oxidation resistance.