Ta-containing Fe-Ni based superalloys with high strength and oxidation resistance for high-temperature applications

1. A Fe—Ni based alloy comprising, in weight percent;

Ni 30-35

Cr 12-14

Al 3-5

Ti 0-2

Ta 2-8

C<=0.05

B<=0.005

Zr<=0.2

Si<0.5

Cr/(Cr+Fe+Ni)=0.125-0.145

Al/(Al+Ti+Ta)=0.15-0.5

Fe≥Ni

Fe/Ni=1.0-2.0

balance Fe, the alloy having a face-centered cubic (fcc) matrix with from 25 to 30 vol. % of L1 2 -type γ′-Ni 3 M (M=Al, Ta, Ti and mixtures thereof) precipitates, wherein a majority volume fraction of the precipitates are L1 2 -type γ′-Ni 3 M precipitates and the combined volume fraction of other precipitate phases is less than 3%, based on the total volume of the alloy.

2. The Fe—Ni based alloy of claim 1 , wherein the L1 2 -type γ′-Ni3M precipitates have a mean radius of from 5 to 10 nm and number density in the order of 1×10 23 to 1×10 24 #/m 3 .

3. The Fe—Ni based alloy of claim 1 , wherein the L1 2 -type γ′-Ni 3 M precipitates have a composition of (Ni+Fe+Cr)≅75 at % and (Al+Ti+Ta)≅25 at % and the matrix have a composition of (Fe+Cr+Ni)≥95 at % and (Al+Ti+Ta)≤5 at %.

4. The Fe—Ni based alloy of claim 1 , wherein the alloy is free of precipitates other than L1 2 -type γ′-Ni 3 M precipitates.

5. The Fe—Ni based alloy of claim 1 , wherein lattice mismatch of the L1 2 -type γ′-Ni 3 M precipitates and the fcc matrix is less than 0.05%.

6. The Fe—Ni based alloy of claim 1 , wherein the alloy has high temperature yield strength greater than or equal to 800 MPa at 700° C. and greater than 500 MPa at 800° C.

7. The Fe—Ni based alloy of claim 1 , wherein the oxidation rate constant at 800° C. in air+10% water vapor is in the order of from 1×10 −13 to 1×10 −14 (g 2 /cm 4 ·s).