Low-cost cast creep-resistant austenitic stainless steels that form alumina for high temperature oxidation resistance

1. An air castable Fe-based stainless steel alloy comprising in weight % based on the total weight of the alloy:

18-22% Cr

15-22% Ni

3.25-6% Al

0.5-5% Mn

1.05-3.5% W

3.05-5% Cu

0-2% Si

1-2.5% Nb

0.3-0.6% C

<0.1% N

balance Fe

wherein, Cu+W+Si=4.1-10.5%, and the alloy provides an oxidation resistance of −2<mass change <+2 mg/cm 2 after 300 one hour cycles at 950° C. in 10% water vapor.

2. The alloy of claim 1 , further comprising 0-2% Ta.

3. The alloy of claim 2 , wherein Ta+Nb<4.0%.

4. The alloy of claim 2 , wherein Ta/Nb=0-0.75.

5. The alloy of claim 1 , further comprising 0.1-5.0% Co.

6. The alloy of claim 1 , wherein the alloy is non-magnetic and free of alpha or delta ferrite phases, and does not form a thermal or strain induced martensite phase.

7. The alloy of claim 1 , wherein the Cu/W ratio is 0.87-1.67.

8. The alloy of claim 1 , wherein Nb/C is from 2-5.

9. The alloy of claim 1 , wherein Cr/Al is 4.7-6.77.

10. The alloy of claim 1 , wherein the Cr/(Al+Si) ratio is 2.25-6.15.

11. The alloy of claim 1 , wherein the alloy provides an oxidation resistance of −0.5<mass change <+2 mg/cm 2 after 400 one hour cycles at 900° C. in 10% water vapor.

12. The alloy of claim 1 , wherein the alloy provides creep rupture resistance of 863 hours at 950° C., 35 MPa and 469 hours at 1050° C., 10 MPa.

13. The alloy of claim 1 , wherein the alloy provides a yield strength of 41.6 Ksi and tensile strength of 84.1 Ksi at room temperature.

14. The alloy of claim 1 , wherein the alloy provides an elongation of 11.1% at room temperature and 39% at 1000° C.