High strength, high fracture toughness structural alloy

Claim 2

An age hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.2-0.33 Chromium 2-4 Nickel 10.5-15 Molybdenum 0.75-1.75 Cobalt 8-17 ______________________________________ and the balance is essentially iron.

Claim 3

An alloy as set forth in claim 1 containing at least about 0.21% carbon.

Claim 4

An alloy as set forth in claim 1 containing at least about 10.75% nickel.

Claim 5

An alloy as set forth in claim 1 wherein a) %Co≦35-81.8(%C).

Claim 6

An alloy as set forth in claim 4 wherein b) %Co≧25.5-70(%C).

Claim 7

An alloy as set forth in claim 5 wherein when %Mo>1.3, %C is not more than the median %C for a given %Co as defined by relationships a) and b).

Claim 8

An alloy as set forth in claim 4 wherein c) %Co ≧26.9-70(%C).

Claim 9

An alloy as set forth in claim 7 wherein when %Mo>1.3, %C is not more than the median %C for a given %Co as defined by relationships a) and c).

Claim 10

An alloy as set forth in claim 1 containing about 0.05% max. manganese.

Claim 11

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.20-0.31 Chromium 2.25-3.5 Nickel 10.75-13.5 Molybdenum 0.75-1.5 Cobalt 10-15 ______________________________________ and the balance is essentially iron.

Claim 12

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.20-0.31 Chromium 2.25-3.5 Nickel 10.75-13.5 Molybdenum 0.75-1.5 Cobalt 10-15 ______________________________________ and the balance is essentially iron.

Claim 13

An alloy as set forth in claim 10 containing at least about 0.21% carbon.

Claim 14

An alloy as set forth in claim 10 containing at least about 11.0% nickel.

Claim 15

An alloy as set forth in claim 10 wherein a) %Co≦35-81.8(%C).

Claim 16

An alloy as set forth in claim 13 wherein b) %Co≧25.5-70(%C).

Claim 17

An alloy as set forth in claim 14 wherein when %Mo>1.3, %C is not more than the median %C for a given %Co as defined by relationships a) and b).

Claim 18

An alloy as set forth in claim 10 containing about 0.05% max. manganese.

Claim 19

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.21-0.27 Chromium 2.5-3.3 Nickel 11.0-12.0 Molybdenum 1.0-1.3 Cobalt 11-14 ______________________________________ and the balance is essentially iron.

Claim 20

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.21-0.27 Chromium 2.5-3.3 Nickel 11.0-12.0 Molybdenum 1.0-1.3 Cobalt 11-14 ______________________________________ and the balance is essentially iron.

Claim 21

An alloy as set forth in claim 17 wherein a) %Co≦35-81.8(%C).

Claim 22

An alloy as set forth in claim 18 wherein b) %Co≧25.5-70(%C).

Claim 23

An alloy as set forth in claim 17 containing about 0.05% max. manganese.

Claim 24

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.21-0.27 Manganese 0.1 max. Silicon 0.1 max. Phosphorus 0.008 max. Sulfur 0.004 max. Chromium 3 Nickel 11 Molybdenum 1.2 Cobalt 13.5 ______________________________________ and the balance is essentially iron, said alloy being further characterized such that in the aged condition it provides tensile strength of at least 280 ksi and K IC fracture toughness of at least 100 ksi √in.

Claim 25

An age-hardenable, martensitic steel alloy which provides high strength and high fracture toughness, said alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.21-0.27 Manganese 0.1 max. Silicon 0.1 max. Phosphorus 0.008 max. Sulfur 0.004 max. Chromium 3 Nickel 11 Molybdenum 1.2 Cobalt 13.5 ______________________________________ and the balance is essentially iron, said alloy being further characterized such that in the aged condition it provides tensile strength of at least 280 ksi and K IC fracture toughness of at least 100 ksi √in.

Claim 26

An alloy as set forth in claim 21 which contains about 0.24% carbon.

Claim 27

An article having high strength and high fracture toughness, said article being formed of an age-hardenable, martensitic steel alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.2-0.33 Chromium 2-4 Nickel 10.5-15 Molybdenum 0.75-1.75 Cobalt 8-17 ______________________________________ and the balance essentially iron.

Claim 28

An article having high strength and high fracture toughness, said article being formed of an age-hardenable, martensitic steel alloy consisting essentially of, in weight percent, about ______________________________________ wt. % ______________________________________ Carbon 0.2-0.33 Chromium 2-4 Nickel 10.5-15 Molybdenum 0.75-1.75 Cobalt 8-17 ______________________________________ and the balance essentially iron.

Claim 29

An article as set forth in claim 23 wherein the alloy contains at least about 0.21% carbon.

Claim 30

An article as set forth in claim 23 wherein the alloy contains at least about 10.75% nickel.

Claim 31

An article as set forth in claim 23 wherein a) %Co≦35-81.1(%C).

Claim 32

An article as set forth in claim 26 wherein b) %Co≧25.5-70(%C).

Claim 33

An article as set forth in claim 27 wherein when %Mo>1.3, %C is not more than the median %C for a given %Co as defined by relationships a) and b).

Claim 34

An article as set forth in claim 23 wherein the alloy contains not more than about 0.05% manganese.