Nitrided component surface repair with autofrettage

Patent metadata

Field	Value
Publication number	US-9333597-B2
Application number	US-201514625273-A
Country	US
Kind code	B2
Filing date	Feb 18, 2015
Priority date	Mar 12, 2013
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A method for repairing a nitrided surface having a damaged area is disclosed. The method includes introducing the nitrided surface into a bath containing electroless material for a predetermined period of time. The method also includes coating the damaged area with a layer of the electroless material. Further the method subjects the layer to an autofrettage process. The electroless material is heat treated at a predetermined temperature for a predefined time.

First claim

What is claimed is:

1. A method for repairing a nitrided surface having a damaged area, the method comprising:
introducing the nitrided surface into a bath containing electroless material for a predetermined period of time;
coating the damaged area with a layer of the electroless material;
performing an autofrettage process on the layer; and
heat treating the electroless material at a predetermined temperature for a predefined time.

2. The method of claim 1 , wherein the autofrettage process includes:
disposing the nitrided surface in a chamber;
introducing autofrettage liquid at a predetermined pressure into the chamber;
maintaining the predetermined pressure in the chamber for a first period of time;
reducing the pressure in the bath after the first period of time has elapsed.

3. The method of claim 2 , wherein the predetermined pressure is about 150,000 psi.

4. The method of claim 2 , wherein the first period of time ranges from 0.5 to 1.0 seconds.

5. The method of claim 2 , wherein the pressure in the bath is reduced from the predetermined pressure to an atmospheric pressure over a second period of time different from the first period of time.

6. The method of claim 2 , wherein the pressure in the bath is reduced linearly.

7. The method of claim 6 , wherein the second period of time ranges from about 1 hour to about 5 hours.

8. The method of claim 1 , wherein the electroless material is configured to provide surface hardness between 60 and 70 HRC.

9. The method of claim 1 , wherein the electroless material includes at least one of nickel and phosphorus.

10. The method of claim 1 further comprising machining the electroless material to a desired finish after the heat treating.

11. The method of claim 1 , wherein the pre-determined period of time for the introduction of the nitrided surface into the bath is based on a thickness requirement of the electroless material.

12. The method of claim 1 , wherein the predetermined temperature for the heat treating lies in a range between 290 and 400° C.

13. The method of claim 1 , wherein the predefined time for the heat treating is less than 24 hours.

14. The method of claim 1 , wherein the nitrided surface includes at least a portion of a plunger for a fuel injection assembly.

15. The method of claim 1 , wherein the damaged area includes cavitation damage on the plunger.

16. A plunger for a fuel injection assembly, the plunger comprising:
an outer nitrided surface having a first hardness, the outer nitrided surface including at least one damaged area; and
an electroless material coated on the damaged area, the electroless material having a second hardness different from the first hardness, the electroless material having been subjected to an autofrettage process.

17. The plunger of claim 16 , wherein the second hardness ranges between 60 and 70 HRC.

18. The plunger of claim 16 , wherein the electroless material includes a least one of nickel and phosphorus.

19. The plunger of claim 16 , wherein the damaged area includes cavitation damage.

20. The plunger of claim 16 , wherein the outer nitrided surface has a first porosity and the electroless material has a second porosity different from the first porosity.

Assignees

• Caterpillar Inc

Inventors

• Wang Huijun
• Grant Marion B

Classifications

• C23C18/36 Primary

  using hypophosphites · CPC title

• C23C18/1605

  by masking · CPC title

• Y10T428/24802

  Discontinuous or differential coating, impregnation or bond [e.g., artwork, printing, retouched photograph, etc.] · CPC title

• F02M2200/9038

  Coatings · CPC title

• F02M2200/80

  Fuel injection apparatus manufacture, repair or assembly · CPC title