Plasma spray coating for sealing a defect area in a workpiece

• US 10,041,163 B1
• Filed: 02/03/2017
• Issued: 08/07/2018
• Est. Priority Date: 02/03/2017
• Status: Active Grant

• Current Assignee: Ge-Hitachi Nuclear Energy Americas LLC (GE Vernova, Inc.)
• Original Assignee: Ge-Hitachi Nuclear Energy Americas LLC (GE Vernova, Inc.)
• Inventors: Offer, Henry Peter, Keck, David Jonathan, Horn, Ronald Martin
• Primary Examiner(s): Culbert, Roberts
• Application Number:
  US15/423,954
• Publication Number:
  US 20180223410A1
• Time in Patent Office: 550 Days
• Field of Search: None
• CPC Class Codes: C23C 4/01 Selective coating, e.g. pattern coating, without pre-treatment of the material to be coated
• CPC Class Codes: C23C 4/02 Pretreatment of the material to be coated, e.g. for coating on selected surface areas
• CPC Class Codes: C23C 4/08 containing only metal elements C23C4/073 takes precedence
• CPC Class Codes: C23C 4/134 Plasma spraying
• CPC Class Codes: C23C 4/18 After-treatment
• CPC Class Codes: H01J 2237/3341 Reactive etching
• CPC Class Codes: H01J 37/3233 using charged particles
• CPC Class Codes: H01J 37/32889 Connection or combination with other apparatus

Abstract

A method for applying a coating to a defect area of a reactor component includes forming a patch on the reactor component at the defect area using a plasma-spray coating process. The plasma-spray coating process includes grounding the reactor component and a power supply of a plasma gun to a common ground such that a potential difference exists between the reactor component and a cathode of the plasma gun, and concurrently directing an ion-etching stream and a coating stream towards the region of the reactor component using the plasma gun while maintaining a desired distance between the plasma gun and the region of the reactor component. The directing the ion-etching stream includes heating the region of the reactor component using a plasma stream exiting a spray nozzle of the plasma gun. The coating stream includes droplets of a coating material.

Claims

1. A method for applying a coating to a defect area of a reactor component, the method comprising:

arranging a plasma gun to face a region of the reactor component that includes at least a portion of the defect area such that the plasma gun and the region of the reactor component are separated by a desired distance;

forming a patch on the reactor component at the defect area using a plasma-spray coating process, the plasma-spray coating process including,

grounding the reactor component and a power supply of the plasma gun to a common ground such that a potential difference exists between the reactor component and a cathode of the plasma gun,

directing an ion-etching stream and a coating stream towards the region of the reactor component using the plasma gun while maintaining the desired distance between the plasma gun and the region of the reactor component,

the directing the ion-etching stream and the coating stream being performed concurrently,

the directing the ion-etching stream including heating the region of the reactor component using a plasma stream exiting a spray nozzle of the plasma gun, and

the directing the coating stream including transferring droplets of a coating material injected into the plasma gun to impinge the region of the reactor component.

2. The method of claim 1, wherein

a thickness of the patch is in a range of 0.1 mm to 100 mm,

a width of the patch is in a range of 1 mm to 250 mm.

3. The method of claim 1, wherein the forming the patch is performed without at least one of using a fusion-welding process and forming a gas shroud.

4. The method of claim 1, wherein

the reactor component is an internal reactor component for use inside a nuclear reactor, and

the reactor component has been highly irradiated.

5. The method of claim 1, wherein the coating material includes at least one metal.

6. The method of claim 5, wherein the at least one metal includes a noble metal.

7. The method of claim 5, wherein

the forming the patch includes performing the plasma spray process so the directing the ion-etching stream heats the reactor component to a temperature below a melting point of the reactor component.

8. The method of claim 5, wherein

the reactor component includes at least one of stainless steel, carbon steel, nickel-based steel, low-alloy steel, chromium-based steel, austenitic steel, or duplex steel,

the forming the patch includes,

forming a primer layer that connects to the reactor component and extends over the defect area, and

forming a first coating layer on the primer layer using the plasma-spray coating process and a first coating material, the first coating material is at least a part of the coating material,

the primer layer is formed using a material that has a high bond strength to a material of the reactor component,

the first coating material includes a material that has greater strain compliance than the primer layer, and

the material of the primer layer is different than the first coating material.

9. The method of claim 8, wherein the forming the patch includes forming the primer layer using a non-plasma method without using a fusion-welding process.

10. The method of claim 9, wherein the forming the patch includes forming the primer layer using a friction-welding process.

11. The method of claim 8, wherein

the forming the patch includes forming a second coating layer on the first coating layer using the plasma-spray coating process and a second coating material,

the second coating material is at least a part of the coating material, and

the first coating material and the second coating material have different compositions.

12. The method of claim 11, wherein

the first coating material includes first particles and the second coating material includes second particles, and

a size of the first particles is greater than a size of the second particles.

13. The method of claim 1, wherein

the defect area is one of a crack, a gap, and a hole defined in the reactor component, and

the forming the patch includes forming the patch to have a pattern that corresponds to a shape of the defect area.

14. The method of claim 1, wherein

the region of the reactor component includes a higher density of defects compared to a portion of the reactor component outside of the region of the reactor component, and

the forming the patch includes forming the patch on an external surface of the region of the reactor component without forming the patch on an external surface of the portion of the reactor component outside of the region.

15. The method of claim 1, wherein the desired distance is in a range of about 10 mm to about 20 mm.

16. The method of claim 1, wherein the reactor component is one of a shroud or a steam separator.

17. The method of claim 1, further comprising:

performing a stress mitigation process on the patch, wherein

the stress mitigation process includes improving a surface finish of the patch using one of, a sanding, and a surface-treatment process.

18. A method for applying a coating on a workpiece using a plasma gun to reduce leakage through a defect area defined in the workpiece, the method comprising:

grounding the workpiece and a power supply of the plasma gun to a common ground such that a potential difference exists between the workpiece and a cathode of the plasma gun;

arranging the plasma gun to face a region of the workpiece that is separated by a distance sufficiently short that the plasma gun is configured to generate a plasma stream that exits the plasma gun during plasma gun operation and will impinge directly on a surface of the region of the workpiece, the region of the workpiece including at least a portion of the defect area;

ion etching the surface of the region of the workpiece by heating the surface with the plasma stream exiting a spray nozzle of the plasma gun to transform oxide-forming atoms on the surface of the region of the workpiece into positive ions,

the distance separating the plasma gun and the workpiece being such that the positive ions leave the surface of the region of the workpiece under the influence of the potential difference between the region of the workpiece and the cathode; and

splattering the surface of the region of the workpiece with droplets of coating material injected into the plasma gun, the ion etching and splattering the surface being performed concurrently with maintaining the potential difference between the workpiece and the cathode.