Case Hardening Method for High Performance Long Life Martensitic Stainless Steel Bearings

Patent metadata

Field	Value
Publication number	US-2017016084-A1
Application number	US-201415038828-A
Country	US
Kind code	A1
Filing date	Nov 24, 2014
Priority date	Nov 25, 2013
Publication date	Jan 19, 2017
Grant date	—

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.

First claim

What is claimed is:

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 one of a carburization and a carbo-nitriding treatment.

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

3 . 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%.

4 . 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.

5 . The method of claim 3 , wherein said first reduction is performed at a higher temperature of 1900 to 1850 F of said martensitic stainless steel material, said second reduction is performed at a temperature range of 1850 to 1775 F, 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.

6 . The method of claim 1 , wherein said subjecting step comprises subjecting said component to a carburization process.

7 . The method of claim 1 , wherein said subjecting step comprises subjecting said component to a carbo-nitriding process.

8 . A method for forming a martensitic stainless steel material comprising the steps of:
providing a martensitic stainless steel material; and thermo-mechanically processing said martensitic stainless steel material to have an ASTM grain size of 9 or finer.

9 . The method of claim 8 , 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%.

10 . The method of claim 9 , 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.

11 . The method of claim 9 , wherein said first reduction is performed at a higher temperature of 1900 to 1850 F of said martensitic stainless steel material, said second reduction is performed at a temperature range of 1850 to 1775 F, 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.

12 . A component comprising:
a core formed from a martensitic stainless steel material having a grain size of 9 or finer in the as processed condition and a coarser grain size in the final harden and temper heat treat condition; and a case hardening structure surrounding said core.

Assignees

• United Technologies Corp

Inventors

• Chin Herbert A
• Haluck David A
• Ogden William P
• Moulin Michael A

Classifications

• C23C8/32

  of ferrous surfaces · CPC title

• C21D2211/008

  Martensite · CPC title

• F16C33/32

  Balls · CPC title

• C21D1/06

  Surface hardening · CPC title

• F16C2223/16

  with carbo-nitriding · CPC title