MARAGING STEEL

• US 20190309400A1
• Filed: 03/08/2019
• Published: 10/10/2019
• Est. Priority Date: 04/06/2018
• Status: Active Grant

• Current Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Original Assignee: Rolls-Royce PLC (Rolls-Royce Holdings Plc)
• Inventors: BHADESHIA, Harshad K., HILL, Paul O., RAWSON, Martin J., DZIEDZIC, Dominik J., HUANG, Zixin
• Granted Patent: US 10,995,395 B2
• Time in Patent Office: Days
• CPC Class Codes: C21D 6/004 containing Cr and Ni
• CPC Class Codes: C21D 6/007 containing Co
• CPC Class Codes: C21D 6/02 Hardening by precipitation
• CPC Class Codes: C22C 33/04 by melting
• CPC Class Codes: C22C 38/06 containing aluminium
• CPC Class Codes: C22C 38/44 with molybdenum or tungsten
• CPC Class Codes: C22C 38/46 with vanadium
• CPC Class Codes: C22C 38/48 with niobium or tantalum
• CPC Class Codes: C22C 38/50 with titanium or zirconium
• CPC Class Codes: C22C 38/52 with cobalt

Abstract

Maraging steel alloys are disclosed. The alloys are produced by microalloying of the maraging steel alloy to form carbides at prior austenite grain boundaries to increase Zener drag. A particular example alloy consists essentially of, by weight, 7.4 to 8.4 percent nickel, 7.6 to 8.6 percent chromium, 8.4 to 9.4 percent cobalt, 1.8 to 2.2 percent molybdenum, 2 to 2.6 percent tungsten, 1.6 to 2 percent aluminium, 0.05 to 0.08 percent carbon, a carbide former selected from the group consisting of: niobium at a concentration of 0.25 to 0.28 percent; titanium, at a concentration of 0.2 to 0.28 percent; and vanadium, at a concentration of 0.21 to 0.4 percent; the balance being iron and incidental impurities.

Claims

1. A maraging steel alloy consisting essentially of, by weight:

7.4 to 8.4 percent nickel;

7.6 to 8.6 percent chromium;

8.4 to 9.4 percent cobalt;

1.8 to 2.2 percent molybdenum;

2 to 2.6 percent tungsten;

1.6 to 2 percent aluminium;

0.05 to 0.08 percent carbon;

a carbide former selected from the group consisting of;

niobium, at a concentration of 0.25 to 0.28 percent;

titanium, at a concentration of 0.2 to 0.28 percent;

vanadium, at a concentration of 0.21 to 0.4 percent;

balance iron and incidental impurities.

2. The alloy of claim 1, in which the concentration of the carbide former is stoichiometric with respect to the carbon concentration.

3. The alloy of claim 1, in which nickel is provided at a concentration of:

7.85 to 7.95 percent by weight;

or

7.9 percent by weight.

4. The alloy of claim 1, in which chromium is provided at a concentration of:

8.05 to 8.15 percent by weight;

or

8.1 percent by weight.

5. The alloy of claim 1, in which cobalt is provided at a concentration of:

8.85 to 8.98 percent by weight;

or

8.9 percent by weight.

6. The alloy of claim 1 in which molybdenum is provided at a concentration of:

1.95 to 2.05 percent by weight;

or

2 percent by weight.

7. The alloy claim 1, in which tungsten is provided at a concentration of:

2.25 to 2.35 percent by weight;

or

2.3 percent by weight.

8. The alloy claim 1, in which aluminium is provided at a concentration of:

1.75 to 1.85 percent by weight;

or

1.8 percent by weight.

9. Cast or forged form of the maraging steel alloy of claim 1.

10. The method comprising applying the maraging steel alloy of claim 1 in a component part of a gas turbine engine.

11. An article comprising the maraging steel alloy of claim 1.

12. A method of producing a maraging steel alloy, comprising:

obtaining a set of constituent elements for a maraging steel alloy;

adding microalloying constituents including carbon and a carbide former;

forming the maraging steel alloy, including the formation of carbides at prior austenite grain boundaries to increase Zener drag.

13. The method of claim 12, in which the carbon and carbide former are provided at a stoichiometric concentration.

14. The method of claim 12, in which the carbide former comprises one of:

titanium;

niobium;

vanadium.