# US 10,119,175 B2 · Case hardening method for high performance long life martensitic stainless steel bearings

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 10,119,175 B2
- Document ID: US10119175B2
- Status: Granted
- Kind: B2
- Application number: 15/038,828
- Filed: 2014-11-24
- Published: 2017-01-19
- Granted: 2018-11-06
- Earliest claimed: 2013-11-25
- Assignees: United Technologies Corporation
- Applicants: United Technologies Corporation
- Inventors: Herbert A Chin; David A Haluck; William P Ogden; Michael A Moulin
- Web page: https://patentgrep.com/patent/US10119175B2

## CPC

- C21D 9/38: for roll bodies
- C21D 1/06: Surface hardening
- C21D 7/13: by hot working
- C21D 9/32: for gear wheels, worm wheels, or the like
- C22C 38/02: containing silicon
- C22C 38/44: with molybdenum or tungsten
- C22C 38/46: with vanadium
- C22C 38/50: with titanium or zirconium
- C22C 38/52: with cobalt
- C23C 8/02: Pretreatment of the material to be coated (C23C8/04 takes precedence)
- C23C 8/22: of ferrous surfaces
- C23C 8/32: of ferrous surfaces
- F16C 33/32: Balls
- F16C 33/34: Rollers; Needles
- F16C 33/62: Selection of substances
- C21D 6/002: {containing Cr (C21D6/004 takes precedence)}
- C21D 2211/008: Martensite
- F16C 2204/72: with nickel as further constituent, e.g. stainless steel
- F16C 2223/12: with carburizing
- F16C 2223/16: with carbo-nitriding
- C21D: MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING (surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by this subclass C23F17/00; unidirectional solidification of eutectic materials or unidirectional demixing of eutectoid materials C30B)
- C22C: ALLOYS (treatment of alloys C21D, C22F)
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- F16C: SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS

## Abstract

A method for cost effectively case hardening a component formed from a martensitic stainless steel material with a desired metallurgical condition for high temperature, high rolling contact fatigue, corrosion and spall initiation and propagation resistance bearing performance. The method describes a method to significantly reduce the carburization or carbo-nitriding process times for appreciable reduction in manufacturing cost. The Method includes the steps of: forming the component from a martensitic stainless steel material having an ASTM grain size of 9 or finer; and subjecting the component to one of a carburization and a carbo-nitriding treatment with significantly lower case hardening times for manufacturing cost-effectiveness.

## Claims

### Claim 1

A method for case hardening a component formed from a martensitic stainless steel material, which method comprises the steps of:
forming said component from a martensitic stainless steel material having an ASTM grain size of 9 or finer; and
subjecting said component to a carbo-nitriding treatment.

### Claim 2 (depends on 1)

The method of claim 1, wherein said component forming step comprising providing a martensitic stainless steel material having an ASTM grain size of at least 5 and thermo-mechanically processing said martensitic stainless steel material to have an ASTM grain size of 9 or finer.

### Claim 3 (depends on 2)

The method of claim 2, wherein said thermo-mechanically processing step comprises subjecting said martensitic stainless steel to a first reduction of at least 50%, a second reduction of at least 60% and a third reduction of at least 70%.

### Claim 4 (depends on 3)

The method of claim 3, wherein each of said first, second, and third reductions is performed by forging or ring rolling at an elevated temperature using a strain rate in the range of 5.0×10-1 inch/inch/second or higher.

### Claim 5 (depends on 3)

The method of claim 3, wherein said first reduction is performed at a higher temperature of 1900 to 1850 degrees Fahrenheit of said martensitic stainless steel material, said second reduction is performed at a temperature range of 1850 to 1775 degrees Fahrenheit, and said third reduction is performed at a temperature above the recrystallization temperature of the martensitic stainless steel material and below the temperature at which the second reduction is performed.