Corrosion and creep resistant high Cr FeCrAl alloys

Patent metadata

Field	Value
Publication number	US-10883160-B2
Application number	US-201916283359-A
Country	US
Kind code	B2
Filing date	Feb 22, 2019
Priority date	Feb 23, 2018
Publication date	Jan 5, 2021
Grant date	Jan 5, 2021

Abstract

An alloy includes in weight % based upon the total weight of the alloy: 28-35% Cr; 2.5-4% Al; 0.8-2% Nb; 5.5-7.5% W; 0-0.5% Mo; 0-0.3% Ti; 0.1-0.3% Zr; 0.1-1% Si; 0-0.07% Y; 0-2% Mn; 0-1% Ni; 0-0.05% C; 0-0.015% B; 0-0.02% N; 0.02-0.04 Ce; balance Fe. The alloy includes a recrystallized, equi-axed grain structure, and forms an external alumina scale, and has strengthening particles including Fe2M (M: Nb, W, Mo, and Ti) type C14 Laves-phase, and a BCC ferritic matrix microstructure from room temperature to melting point with less than 1% FCC-phase, less than 1% martensite phase, less than 0.5 wt. % of carbides (MC and M23C6), and at least 1% tensile elongation at room temperature. The alloy provides a creep resistance of greater than 3000 to 15000 h creep rupture life at 750° C. and 50 MPa, or greater than 500 to 5000 h creep rupture life at 700° C. and 100 MPa.

First claim

We claim:

1. An alloy comprising in weight % based upon the total weight of the alloy:
28-35% Cr
2.5-4% Al
0.8-2% Nb
5.5-7.5% W
0-0.5% Mo
0-0.3% Ti
0.1-0.3% Zr
0.1-1% Si
0-0.07% Y
0-2% Mn
0-1% Ni
0-0.05% C
0-0.015% B
0-0.02% N
0.02-0.04 Ce
balance Fe, the alloy comprising at least 99% recrystallized, at least 99% equi-axed grain structure with an average grain size of 10 to 100 μm, wherein the alloy forms an external continuous scale comprising alumina, and has nanometer scale sized strengthening particles with 5 to 500 nm in size and mole fraction of 5 to 10%, distributed throughout the microstructure, the particles comprising at least one composition selected from the group consisting of Fe 2 M (M: Nb, W, Mo, and Ti) type C14 Laves-phase, and a stable essentially single-phase BCC ferritic matrix microstructure from room temperature to melting point, the ferritic matrix being less than 1% FCC-phase, less than 1% martensite phase, less than 0.5 wt. % of carbides (MC and M 23 C 6 ), with at least 1% tensile elongation at room temperature, and wherein the alloy has an oxidation resistance of a positive specific mass change less than 0.5 mg/cm 2 after 5000 h exposure at 800° C. in air with 10 volume percent H 2 O, an ash-corrosion resistance of a positive specific mass change less than 2 mg/cm 2 after 1000 h exposure at 700° C. in a synthetic ash and gas environment, and a creep resistance of greater than 3000 to 15000 h creep rupture life at 750° C. and 50 MPa, and/or greater than 500 to 5000 h creep rupture life at 700° C. and 100 MPa.

2. The alloy of claim 1 , wherein Cr is 30-35 wt. %.

3. The alloy of claim 1 , wherein Al is 3-4 wt. %.

4. The alloy of claim 1 , wherein Nb is 1-2 wt. %.

5. The alloy of claim 1 , wherein W is 6-7.5 wt. %.

6. The alloy of claim 1 , wherein Si is 0.15-1 wt. %.

7. The alloy of claim 1 , wherein Y is 0.01-0.07 wt. %.

8. The alloy of claim 1 , wherein Ce is 0.03-0.04 wt. %.

9. The alloy of claim 1 , wherein Mn is 0.4 to 2 wt. %.

10. The alloy of claim 1 , wherein C is <0.035 wt. %.

11. The alloy of claim 1 , wherein B is 0.01 to 0.015 wt. %.

12. The alloy of claim 1 , wherein N is 0 to 0.005 wt. %.

13. The alloy of claim 1 , wherein the average grain size is 10-50 μm.

14. The alloy of claim 1 , wherein the strengthening particles are 5-300 nm.

15. The alloy of claim 1 , wherein the mole fraction of the particles is 6-8%.

16. The alloy of claim 1 , wherein the alloy consists essentially of:
28-35% Cr
2.5-4% Al
0.8-2% Nb
5.5-7.5% W
0-0.5% Mo
0-0.3% Ti
0.1-0.3% Zr
0.1-1% Si
0-0.07% Y
0-2% Mn
0-1% Ni
0-0.05% C
0-0.015% B
0-0.02% N
0.02-0.04 Ce
balance Fe and no more than 1% of trace elements.

17. The alloy of claim 1 , wherein the alloy consists of:
28-35% Cr
2.5-4% Al
0.8-2% Nb
5.5-7.5% W
0-0.5% Mo
0-0.3% Ti
0.1-0.3% Zr
0.1-1% Si
0-0.07% Y
0-2% Mn
0-1% Ni
0-0.05% C
0-0.015% B
0-0.02% N
0.02-0.04 Ce
balance Fe.

18. A method of making an alloy, comprising the steps of: providing an alloy precursor composition comprising
28-35% Cr
2.5-4% Al
0.8-2% Nb
5.5-7.5% W
0-0.5% Mo
0-0.3% Ti
0.1-0.3% Zr
0.1-1% Si
0-0.07% Y
0-2% Mn
0-1% Ni
0-0.05% C
0-0.015% B
0-0.02% N
0.02-0.04 Ce
balance Fe; and,

heating the alloy precursor composition to form an alloy, and subjecting the alloy to a controlled thermomechanical treatment consisting of a combination of hot-forging and -rolling with total deformation more than 70% and multiple re-heating process steps at an intermediate temperature between 800 and 1000° C. during hot-forging and -rolling, followed by recrystallization through annealing at a temperature between 1150 to 1250° C., to achieve a fully recrystallized, equi-axed grain structure with the average grain size of 10 to 100 μm, and at least 1% tensile elongation at room temperature.

19. The method of claim 18 , wherein the annealing temperature is 1200° C.

20. The method of claim 18 , wherein the average grain size is 10 to 50 μm.

Assignees

• Ut Battelle Llc

Inventors

• Yamamoto Yukinori
• Pint Bruce A
• Brady Michael P

Classifications

• C21D8/02

  during manufacturing of plates or strips (C21D8/12 takes precedence) · CPC title

• C21D8/0273

  Final recrystallisation annealing · CPC title

• C22C38/001

  containing N · CPC title

• C22C38/54 Primary

  with boron · CPC title

• C22C38/005

  containing rare earths, i.e. Sc, Y, Lanthanides · CPC title