Ferritic nitrocarburized part and methods of making and using the same

Patent metadata

Field	Value
Publication number	US-10870910-B2
Application number	US-201815866814-A
Country	US
Kind code	B2
Filing date	Jan 10, 2018
Priority date	Jan 10, 2018
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A number of variations may include a ferritic nitrocarburized part comprising steel, wherein the ferritic nitrocarburized steel has a tensile strength exceeding the parent steel material and sufficient ductility, bendability, and flangeability to support subsequent flanging and press-fitting of bushings. Exact strength increases and bendability will be dependent on exact process and alloy combinations.

First claim

What is claimed is:

1. A product comprising:
a ferritic nitrocarburized part including a parent steel material that is subcritically annealed;
wherein the ferritic nitrocarburized part has a tensile strength exceeding that of the parent steel material, and the ferritic nitrocarburized part has characteristics of ductility, bendability, and flangeability to support subsequent flanging and press-fitting of bushings; and
wherein the ferritic nitrocarburized part includes a compound zone and a surface at an outer edge of the compound zone, wherein the surface is configured for engagement with a corresponding friction material, and wherein the compound zone includes a nitride layer having epsilon iron nitride, Fe 2-3 N and gamma prime iron nitride Fe 4 N.

2. The product as defined in claim 1 wherein the ferritic nitrocarburized part includes a structural component for a vehicle.

3. The product as defined in claim 2 wherein the structural component defines a hole, and further includes an insert disposed in the hole.

4. The product as defined in claim 1 wherein the nitride layer includes an outer surface.

5. The product as defined in claim 1 wherein the compound zone further includes an iron oxide layer overlying the nitride layer, and the iron oxide layer includes an outer surface.

6. The product as defined in claim 1 wherein the nitride layer has a depth of at least 10 microns.

7. A product comprising:
a parent steel that is cold-rolled and subcritically annealed;
a compound zone disposed on the parent steel to form a ferritic nitrocarburized part, and the compound zone includes a nitride layer disposed on the parent steel;
wherein the nitride layer includes epsilon iron nitride, Fe 2-3 N, and gamma prime iron nitride Fe 4 N; and
wherein the ferritic nitrocarburized part has a tensile strength that exceeds that of the parent steel.

8. The product as defined in claim 7 wherein the ferritic nitrocarburized part includes a structural component for a vehicle.

9. The product as defined in claim 8 wherein the structural component defines a hole, and further includes an insert disposed in the hole.

10. A method comprising:
providing a part that includes a parent steel material;
preheating the part to about 400° C. 500° C. for about 2-4 hours;
subcritically annealing the part that includes heating that part to about 500° C. 725° C. for about 1-5 hours and cooling the part to about 350° C.-500° C.;
heating the part to about 500° C.-650° C.;
ferritic nitrocarburizing the part at about 500° C.-650° C. to form an iron nitride layer on a surface of the part;
cooling the part to provide a ferritic nitrocarburized part that includes the parent steel material, wherein the ferritic nitrocarburized part has a tensile strength exceeding that of the parent steel material, and the ferritic nitrocarburized part has characteristics of ductility, bendability, and flangeability to support subsequent flanging and press-fitting of bushings; and
wherein ferritic nitrocarburizing the part includes forming a compound zone and a surface at an outer edge of the compound zone, wherein the surface at the outer edge is configured for engagement with a corresponding friction material, and wherein the compound zone includes a nitride layer having epsilon iron nitride, Fe 2-3 N and gamma prime iron nitride Fe 4 N.

11. The method as defined in claim 10 wherein ferritic nitrocarburizing includes a gas nitrocarburizing process, a plasma nitrocarburizing process, a fluidized bed nitrocarburization process, or a salt bath nitrocarburizing process.

12. The method as defined in claim 10 wherein the ferritic nitrocarburized part includes a structural component for a vehicle.

13. The method as defined in claim 10 wherein the nitride layer includes an outer surface.

14. The method as defined in claim 10 wherein ferritic nitrocarburizing the part further includes forming an iron oxide layer in the compound zone overlying the nitride layer, wherein the iron oxide layer includes an outer surface.

15. The method as defined in claim 14 wherein the iron oxide layer includes oxidized nitrocarburized iron having a formula of Fe 3 O 4 .

16. The method as defined in claim 10 wherein the nitride layer has a depth of at least 10 microns.

17. The method as defined in claim 10 wherein ferritic nitrocarburizing the part further includes heat treatment of the part in an atmosphere rich in nitrogen and carbon in a mixture.

Assignees

• Gm Global Tech Operations Llc
• Woodworth Inc

Inventors

• Holly Michael L
• Deciechi Dennis
• Gentile James J
• Cummings David M
• Enloe Charles M

Classifications

• C23C8/38

  Treatment of ferrous surfaces · CPC title

• C23C8/32

  of ferrous surfaces · CPC title

• B62D29/007 Primary

  predominantly of special steel or specially treated steel, e.g. stainless steel or locally surface hardened steel · CPC title

• C21D1/26

  Methods of annealing · CPC title

• C23F17/00

  Multi-step processes for surface treatment of metallic material involving at least one process provided for in class C23 and at least one process covered by subclass C21D or C22F or class C25 (coating for obtaining at least two superposed coatings either by methods not provided for in a single one of main groups C23C2/00 - C23C26/00, or by combinations of methods providedfor in subclasses C23C and C25D, C23C28/00) · CPC title