US5221372A
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Fracture-tough, high hardness stainless steel and method of making same
Assignee: Northwestern University
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Filing: 1992-02-13
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Granted: 1993-06-22
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Expires: 2012-02-13
Abstract
Abstract A cryogenically-formed and tempered stainless steel is provided having improved fracture toughness and corrosion resistance at a given hardness level, such as, for example, of at least about Rc 60 for bearing applications. The steel consists essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron. The steel includes a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % post-deformation retained austenite dispersed therein and M 2 C-type carbides, where M is Cr, Mo, V, and/or Fe, dispersed in the microstructure.
Inventors
- 👤 Gregory B. Olson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:21
CPC Classifications
C; C22; C22C; C22C38/00; C22C38/18; C22C38/40; C22C38/52; C21; C21D; C21D7/00; C21D7/02; C21D7/10; C21D8/00
Claims Analysis
Total Claims: 43
Claim 1
Independent Claim
121 words
A cyrogenically-formed and tempered stainless steel having improved fracture toughness and croosion resistance at a given hardness level, said steel includign at least about 11 weight % Cr for corrosion resistance, at least about 0.28 weight % C for hardness, one or more refractory metal carbide formers in an amount selected to form M 2 C-type carbides, where M is the refractory metal(s), Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite, and the balance essentially Fe, said steel having a cyrogenically-formed martensitic microstructure tempered to include a minor, controlled amount of post-deformation retained austenite and dispersed M 2 C-type carbides.
Claim 2
Dependent Claim
121 words
A cyrogenically-formed and tempered stainless steel having improved fracture toughness and croosion resistance at a given hardness level, said steel includign at least about 11 weight % Cr for corrosion resistance, at least about 0.28 weight % C for hardness, one or more refractory metal carbide formers in an amount selected to form M 2 C-type carbides, where M is the refractory metal(s), Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite, and the balance essentially Fe, said steel having a cyrogenically-formed martensitic microstructure tempered to include a minor, controlled amount of post-deformation retained austenite and dispersed M 2 C-type carbides.
Claim 3
Dependent Claim
47 words
The stainless steel of claim 1 consisting essentially of at least about 0.28 weight % C, at least about 20 weight % Co, at least about 5 weight % Ni, and at least about 0.1 weight % Mo and 0.2 weight % V as the carbide formers.
Claim 4
Dependent Claim
25 words
The stainless steel of claim 2 wherein the tempered martensitic microstructure includes about 5 to about 10 volume % of post-deformation retained austenite dispersed therein.
Claim 5
Dependent Claim
100 words
A stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type carbides, where M is Cr, Mo, V, and/or Fe, dispersed therein.
Claim 6
Dependent Claim
100 words
A stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type carbides, where M is Cr, Mo, V, and/or Fe, dispersed therein.
Claim 7
Dependent Claim
105 words
A stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 57, consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type carbides, where M is Cr, Mo, V and/or Fe, dispersed therein.
Claim 8
Dependent Claim
105 words
A stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 57, consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type carbides, where M is Cr, Mo, V and/or Fe, dispersed therein.
Claim 9
Dependent Claim
86 words
A stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least Rc 60, consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type oarbides, where M is Cr, Mo, V, and/or Fe, dispersed therein.
Claim 10
Dependent Claim
86 words
A stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least Rc 60, consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron, said steel having a cryogenically-formed martensitic microstructure tempered to include about 5 to about 10 volume % of post-deformation retained austenite dispersed therein and including M 2 C-type oarbides, where M is Cr, Mo, V, and/or Fe, dispersed therein.
Claim 11
Dependent Claim
28 words
The stainless steel of claim 5 having a fracture toughness of at least about 40 KSI in. 1/2 at room temperature as measured by ASTM STP E399 test.
Claim 12
Dependent Claim
12 words
The stainless steel of claim 4 having a nitride surface case thereon.
Claim 13
Dependent Claim
12 words
The stainless steel of claim 5 having a nitride surface case thereon.
Claim 14
Dependent Claim
9 words
A bearing comprising the stainless steel of claim 5.
Claim 15
Dependent Claim
59 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure, consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron.
Claim 16
Dependent Claim
59 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure, consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron.
Claim 17
Dependent Claim
59 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron.
Claim 18
Dependent Claim
59 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron.
Claim 19
Dependent Claim
41 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron.
Claim 20
Dependent Claim
41 words
A stainless steel composition that is cryogenically-formable to produce a predominantly martensitic microstructure consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron.
Claim 21
Independent Claim
169 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, comprising the steps of: a) providing a stainless steel including at least about 11 weight % Cr for corrosion resistance, at least about 0.28 weight % C for temper hardness, a refractory metal carbide former in an amount selected to form M 2 C-type carbides, where M is the refractory metal, Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure that is cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite dispersed therein, and the balance essentially Fe, b) cryogenically-deforming the steel in the as-quenched condition to transform the austenitic microstructure to a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed therein, and c) tempering the cryogenically-deformed steel at an elevated temperature to control the amount of post-deformation retained austenite dispersed in the microstructure and to form the M 2 C-type carbides dispersed in the microstructure.
Claim 22
Independent Claim
169 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, comprising the steps of: a) providing a stainless steel including at least about 11 weight % Cr for corrosion resistance, at least about 0.28 weight % C for temper hardness, a refractory metal carbide former in an amount selected to form M 2 C-type carbides, where M is the refractory metal, Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure that is cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite dispersed therein, and the balance essentially Fe, b) cryogenically-deforming the steel in the as-quenched condition to transform the austenitic microstructure to a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed therein, and c) tempering the cryogenically-deformed steel at an elevated temperature to control the amount of post-deformation retained austenite dispersed in the microstructure and to form the M 2 C-type carbides dispersed in the microstructure.
Claim 23
Independent Claim
141 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, to form a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C-type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 24
Independent Claim
141 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a given hardness level, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 20 to about 30% Co, about 11 to about 13% Cr, about 5 to about 10% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, to form a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C-type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 25
Independent Claim
149 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 57, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, to form a martensitic microstructure including less than about 15 volume % of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C-type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 26
Independent Claim
149 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 57, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 21 to about 24% Co, about 11 to about 13% Cr, about 7 to about 9.50% Ni, about 0.1 to about 0.5% Mo, about 0.2 to about 0.3% V, about 0.28 to about 0.32% C, and the balance iron, to form a martensitic microstructure including less than about 15 volume % of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C-type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 27
Independent Claim
132 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 60, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron, to form a martensitic microstructure including less than about 15 volume % of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C. type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 28
Independent Claim
132 words
A method of making a stainless steel having improved fracture toughness and corrosion resistance at a hardness level of at least about Rc 60, comprising the steps of: a) cryogenically deforming an as-quenched austenitic stainless steel consisting essentially of, in weight %, about 22.5% Co, about 12% Cr, about 8.50% Ni, about 0.3% Mo, about 0.25% V, about 0.30% C, and the balance iron, to form a martensitic microstructure including less than about 15 volume % of post-deformation retained austenite dispersed in the microstructure, and b) tempering the deformed stainless steel at an elevated temperature to provide about 5 to about 10 volume % of post-deformation retained austenite dispersed in the microstructure and to form M 2 C. type carbides, where M is Cr, Fe, Mo and/or V, dispersed in the microstructure.
Claim 29
Dependent Claim
23 words
The method of claim 14 including the further step of nitriding the cryogenically deformed stainless steel to form a nitrided surface case thereon.
Claim 30
Dependent Claim
23 words
The method of claim 15 including the further step of nitriding the cryogenically deformed stainless steel to form a nitrided surface case thereon.
Claim 31
Dependent Claim
23 words
The method of claim 16 including the further step of nitriding the cryogenically deformed stainless steel to form a nitrided surface case thereon.
Claim 32
Independent Claim
18 words
The method of claims 18, 19 or 20 wherein the stainless steel is nitrided during the tempering step.
Claim 33
Dependent Claim
12 words
The method of claim 21 wherein the stainless steel is ion nitrided.
Claim 34
Dependent Claim
27 words
The method of claim 14 wherein the cryogenically deformed stainless steel is tempered to destabilize the retained austenite and the tempered stainless steel is further cryogenically deformed.
Claim 35
Dependent Claim
27 words
The method of claim 15 wherein the cryogenically deformed stainless steel is tempered to destabilize the retained austenite and the tempered stainless steel is further cryogenically deformed.
Claim 36
Dependent Claim
27 words
The method of claim 16 wherein the cryogenically deformed stainless steel is tempered to destabilize the retained austenite and the tempered stainless steel is further cryogenically deformed.
Claim 37
Dependent Claim
24 words
The method of claim 14 wherein the cryogenically deformed steel is tempered by repeatedly heating the steel to the tempering temperature and cryogenically cooling.
Claim 38
Dependent Claim
24 words
The method of claim 15 wherein the cryogenically deformed steel is tempered by repeatedly heating the steel to the tempering temperature and cryogenically cooling.
Claim 39
Dependent Claim
24 words
The method of claim 16 wherein the cryogenically deformed steel is tempered by repeatedly heating the steel to the tempering temperature and cryogenically cooling.
Claim 40
Dependent Claim
122 words
A cryogenically-formed and tempered stainless steel having improved fracture toughness and corrosion resistance, said steel including at least about 11 weight % Cr for corrosion resistance, C in an amount to achieve a hardness of at least about Rc 57, one or more refractory metal carbide formers in an amount selected to form M 2 C-type carbides, where M is the refractory metal (s), Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite, and the balance essentially Fe, said steel having a cryogenically-formed martensitic microstructure tempered to include a minor, controlled amount of post-deformation retained austenite and dispersed M 2 C-type carbides.
Claim 41
Dependent Claim
122 words
A cryogenically-formed and tempered stainless steel having improved fracture toughness and corrosion resistance, said steel including at least about 11 weight % Cr for corrosion resistance, C in an amount to achieve a hardness of at least about Rc 57, one or more refractory metal carbide formers in an amount selected to form M 2 C-type carbides, where M is the refractory metal (s), Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite, and the balance essentially Fe, said steel having a cryogenically-formed martensitic microstructure tempered to include a minor, controlled amount of post-deformation retained austenite and dispersed M 2 C-type carbides.
Claim 42
Independent Claim
181 words
A method of making a stainless steel having miproved fracture toughness and corrosion resistance, comprising the steps of: a) providing a stainless steel including at least about 11 weight % Cr for corrosion resistance, C in an amount to achieve a temper hardness of at least about Rc 57, a refractory metal carbide former in an amount selected to form M 2 C-type carbides, where M is the refractory metal, Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure that is cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite dispersed therein, and the balance essentially Fe, b) cryogenically-deforming the steel in the as-quenched condition to transform the austenitic microstructure to a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed therein, and c) tempering the cryogenically-deformed steel at an elevated temperature to control the amount of post-deformation retained austenite dispersed in the microstructure and to form the M 2 C-type carbides dispersed in the microstructure, said tempered microstructure having a hardness of at least about Rc 57.
Claim 43
Independent Claim
181 words
A method of making a stainless steel having miproved fracture toughness and corrosion resistance, comprising the steps of: a) providing a stainless steel including at least about 11 weight % Cr for corrosion resistance, C in an amount to achieve a temper hardness of at least about Rc 57, a refractory metal carbide former in an amount selected to form M 2 C-type carbides, where M is the refractory metal, Cr and/or Fe, Co and Ni in amounts selected to provide an as-quenched austenitic microstructure that is cryogenically-deformable to a martensitic microstructure including a minor amount of post deformation retained austenite dispersed therein, and the balance essentially Fe, b) cryogenically-deforming the steel in the as-quenched condition to transform the austenitic microstructure to a martensitic microstructure including a minor amount of post-deformation retained austenite dispersed therein, and c) tempering the cryogenically-deformed steel at an elevated temperature to control the amount of post-deformation retained austenite dispersed in the microstructure and to form the M 2 C-type carbides dispersed in the microstructure, said tempered microstructure having a hardness of at least about Rc 57.
References Cited (Backward Citations)
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| 7.5 Years (Year 8) | 2000-06-21 | 2000-12-21 | 2001-06-22 | $3760.00 | Window Closed / Lapsed |
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