US20150197840A1

US20150197840A1 - Systems and methods for removing overspray

Info

Publication number: US20150197840A1
Application number: US14/575,395
Authority: US
Inventors: Mario P. Bochiechio; Brian T. Hazel; Jessica L. Serra
Original assignee: United Technologies Corp
Current assignee: RTX Corp
Priority date: 2014-01-10
Filing date: 2014-12-18
Publication date: 2015-07-16

Abstract

Systems and methods are disclosed for removing overspray from a substrate. A coating material may be plasma sprayed on a substrate utilizing Suspension Plasma Spray or Solution Precursor Plasma Spray. The plasma spray may deposit loosely adhered overspray on the substrate. A pressurized gas may be directed at the overspray to remove the overspray from the component.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional of, and claims priority to, and the benefit of U.S. Provisional Application No. 61/925,875, entitled “SYSTEMS AND METHODS FOR REMOVING OVERSPRAY,” filed on Jan. 10, 2014, which is hereby incorporated by reference in its entirety.

FIELD

The present disclosure relates generally to plasma spraying. More particularly, the present disclosure relates to systems and methods for removal of overspray.

BACKGROUND

Suspension Plasma Spray (SPS) and Solution Precursor Plasma Spray (SPPS) processes may be used to apply a coating to components in various industries, including components for gas turbine engines. The coating may adhere to the components primarily by mechanical forces. During SPS and SPPS processes, overspray generated during the processes may loosely adhere to portions of the components. The overspray may have a weak bond to the underlying material, such that when additional coating is applied over the overspray, the additional material may be weakly bonded to the component due to the weak bond between the component and the overspray. Overspray bonding may be sufficiently weak that the coating may prematurely spall during processing or during operation, resulting in diminished performance of the component.

SUMMARY

A method of removing overspray may comprise plasma spraying a substrate with a coating material. The plasma spraying may deposit overspray on the substrate. The method may further include directing a separate pressurized gas at the overspray, wherein the pressurized gas carries a media.
A system for coating a substrate may comprise a plasma torch and a gas nozzle. The plasma torch may be configured to deposit a coating material on a substrate. The gas nozzle may be configured to remove overspray from the substrate.
A method of plasma spraying a substrate may comprise depositing a first plasma sprayed coating on a first portion of the substrate. The method may comprise depositing overspray on a second portion of the substrate. The method may comprise directing pressurized gas at the first portion of the substrate and the second portion of the substrate. The pressurized gas may remove the overspray from the second portion of the substrate. The method may further comprise depositing a second plasma sprayed coating on the second portion of the substrate.
The foregoing features and elements may be combined in various combinations without exclusivity, unless expressly indicated otherwise. These features and elements as well as the operation thereof will become more apparent in light of the following description and the accompanying drawings. It should be understood, however, the following description and drawings are intended to be exemplary in nature and non-limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter of the present disclosure is particularly pointed out and distinctly claimed in the concluding portion of the specification. A more complete understanding of the present disclosure, however, may best be obtained by referring to the detailed description and claims when considered in connection with the drawing figures.

FIG. 1 illustrates a component with a layer of coating material in accordance with various embodiments;

FIG. 2 illustrates a component with a portion of overspray removed in accordance with various embodiments;

FIG. 3 illustrates an overspray removal system in accordance with various embodiments;

FIG. 4 illustrates a control system with a cam follower in accordance with various embodiments;

FIG. 5 illustrates gas nozzle coupled to a plasma torch in accordance with various embodiments; and

FIG. 6 illustrates a flow diagram of a process for removing overspray in accordance with various embodiments.

DETAILED DESCRIPTION

The detailed description of various embodiments herein makes reference to the accompanying drawings, which show various embodiments by way of illustration. While these various embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosure, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the spirit and scope of the disclosure. Thus, the detailed description herein is presented for purposes of illustration only and not of limitation. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented. Furthermore, any reference to singular includes plural embodiments, and any reference to more than one component or step may include a singular embodiment or step. Also, any reference to attached, fixed, connected, or the like may include permanent, removable, temporary, partial, full, and/or any other possible attachment option. Additionally, any reference to without contact (or similar phrases) may also include reduced contact or minimal contact.
Systems and methods are disclosed herein for removing overspray from a component. A plasma torch may deposit a coating material onto a component. During deposition of the coating material, a portion of the deposited material termed “overspray” may be loosely adhered to the component. The overspray may be loosely adhered to the component adjacent to an intended coating surface.
The overspray may be a result of fine particles or media present in the SPS or SPPS processes. The trajectory that fine particles take in the process may be influenced by the plasma gases more so than with heavier particles in traditional plasma spray processes. As the plasma gases approach the component, the plasma gases may spread out and/or deflect away from the target point of the plasma torch. The plasma gases at the edges of the plasma jet may follow a longer mean path before contacting the surface of the component. Fine particles carried by the plasma gases at the edges of the plasma jet may thus interact with the atmosphere for longer time and cool off disproportionately compared to fine particles in the center of the plasma jet. The fine particles may therefore be cooler at the point of contact with the component and may be less able to deform and bond with the target surface. The result may be a weak bond to the component at locations farther away from the center of the plasma jet. The overspray may additionally be caused by a lack of entrainment of the particulate within the plasma plume. The fine particles may not penetrate the plume effectively and may flow along the outside of the plasma plume.
A gas nozzle may direct pressurized gas at the component in order to remove the overspray. The pressurized gas may carry solid particles which may contact the component. Once the overspray is removed, the plasma torch may deposit additional coating material to the cleaned surface which may sufficiently adhere to the component.
Referring to FIG. 1, a component 100 with a layer of coating material 110 is illustrated according to various embodiments. A plasma spray system may deposit coating material 110 onto component 100. Component 100 may comprise any type of component for which a plasma sprayed coating may be desirable. In various embodiments, component 100 may comprise a component of a gas turbine engine, such as a turbine blade, turbine vane, blade outer air seal, or combustor component. However, components suitable for use with the present disclosure may be found in many industries and are not limited to those recited herein.
Coating material 110 may improve properties of component 100. In various embodiments, coating material 110 may comprise a thermal protective layer. Various coating materials may improve functional performance of component 100, improve the component life by reducing abrasion or corrosion, and may allow higher cost materials with advantageous properties to be utilized on a lower cost material which forms the structure of component 100.
In various embodiments, coating material 110 may be deposited onto component 100 using a Suspension Plasma Spraying (“SPS”) process. SPS involves dispersing a ceramic feedstock into a liquid suspension prior to injecting the feedstock into a plasma jet. In various embodiments, coating material 110 may be deposited using a Solution Precursor Plasma Spray (“SPPS”) process, in which a solution of coating precursors is atomized and injected into a direct current (DC) plasma jet. The precursor droplets may evaporate and breakup in the plasma. Various materials may be plasma sprayed onto component 100. In various embodiments, coating material 110 may comprise a rare earth partially-stabilized zirconia, such as yttria-stabilized zirconia, a rare earth stabilized zirconia, such as gadolinium stabilized zirconia, or any other material suitable for plasma spraying onto component 100.
During deposition of coating material 110, overspray 120 may be deposited onto component 100 adjacent to coating material 110. Overspray 120 may be loosely adhered to component 100, and removal of overspray 120 may be desirable prior to depositing additional coating material in the area of overspray 120.
Referring to FIG. 2, component 100 is illustrated with a portion of overspray 120 removed. In various embodiments, overspray 120 may be removed by directing a pressurized gas at component 100. The pressurized gas may contact component 100 at a kinetic energy sufficiently high to remove overspray 120, yet sufficiently low to not remove coating material 110. In various embodiments, the kinetic energy may be sufficiently higher than the amount of energy to bond the overspray to the underlying surface, but less than the energy to bond the target material to the underlying surface so as to preferentially remove the material from the overspray region. As illustrated in FIG. 2, pressurized gas has been directed across area 210, such that overspray 120 is removed from component in area 210, and such that coating material 110 remains on component 100 in area 210.
In various embodiments, the pressurized gas may comprise at least one of carbon dioxide, nitrogen (N₂), argon, other noble gases, water vapor, compressed air, or any other suitable gas. In various embodiments, the pressurized gas alone may be sufficient to remove overspray 120. However, in various embodiments, the pressurized gas may carry a media to add kinetic energy or otherwise assist in removing the overspray. In various embodiments, the media may exist as a gas at standard temperature and pressure (STP), such that removal of the media may not be required after removal of the overspray. In various embodiments, the media may comprise dry ice (carbon dioxide) particles which may sublimate after removal of the overspray. In various embodiments, the media may comprise liquid nitrogen which may evaporate after removal of the overspray.
In various embodiments, the media may comprise a liquid. The pressurized gas may be at a higher temperature than the boiling point of the liquid. In various embodiments, the media may comprise water droplets, and the pressurized gas may be at a temperature higher than 100° C. (212° F.). The water droplets may be in the pressurized gas for a short time before contacting the component, such that the water droplets contact the component prior to evaporating, and evaporate after removing the overspray.
In various embodiments, the pressurized gas may comprise particulate matter such as polymer beads, alumina powder, silicon carbide powder, glass beads, walnut shells, sodium bicarbonate, sodium bicarbonate/alumina blend, or any other suitable abrasive media that may remove the overspray but not significantly alter dimensions of the component, interfere with coating adhesion, or alter the bond coat surface finish.
Referring to FIG. 3, an overspray removal system 300 is illustrated according to various embodiments. Overspray removal system may comprise a gas nozzle 310 or series of nozzles directed at the overspray to be removed. Gas nozzle 310 may direct pressurized gas 312 toward a component 320. Gas nozzle 310 may be positioned with a control system 330. In various embodiments, control system 330 may comprise robotics and/or one or more servo motors or cam followers. Control system 330 may be designed to optimize the standoff distance of gas nozzle 310 from the surface of which the overspray is to be removed. In various embodiments, overspray removal system 300 may comprise a plurality of gas nozzles 310, and a plurality of solenoid valves which may turn gas nozzles 310 on/off as necessary to target the appropriate surfaces of component 320 and to maximize the effectiveness of overspray removal while controlling and/or reducing gas usage in the process.
In various embodiments, control system 330 may comprise a distance meter 340. In various embodiments, distance meter 340 may comprise a laser distance meter. As component 320 rotates about axis of rotation 322, a standoff distance D between gas nozzle 310 and component surface 324 may change. Distance meter 340 may detect a change in distance and may transmit the information to control system 330. In response, control system 330 may move gas nozzle 310 such that standoff distance D remains substantially constant. In various embodiments, control system 330 may comprise two axis control of gas nozzle 310, three axis control of gas nozzle 310, or any number of axes.
In various embodiments, a pressure of the pressurized gas 312 may depend on a variety of factors, such as the standoff distance D, the type of gas and/or particulate matter being used, and a nozzle size. In various embodiments, gas carrying dry ice particles may be pressurized to between 20 psi-90 psi (140 kPA-620 kPa), and a standoff distance D may be between 4 inches-15 inches (10 cm-38 cm). A nozzle diameter may be between 0.2 inches-1.0 inches (0.51 cm-2.5 cm). In various embodiments, the pressurized gas may exit gas nozzle 310 at speeds of between about Mach 1.5-Mach 2.5 (510 m/s-850 m/s). However, in various embodiments, any combination of pressure, standoff distance, gas type, and nozzle size may be used wherein the kinetic energy of the pressurized gas is sufficient to remove overspray yet not remove the coating material.
Referring to FIG. 4, in various embodiments, control system 400 may comprise a cam follower 410. Cam follower 410 may comprise a shaft 412 coupled to a roller 414 in contact with the component 320 being coated. Component 320 may be rotated on a turntable or carousel. As component 320 rotates, contact between component 320 and roller 414 may force shaft 412 away from the axis of rotation 322 of component 320. A spring may be coupled to shaft 412 which maintains pressure on shaft 412 in the direction of axis of rotation 322 of component 320.
In various embodiments, gas nozzle 310 may be coupled to shaft 412. Gas nozzle 310 may be coupled to shaft 412 at an optimized standoff distance D from component 320. Thus, as component 320 rotates, gas nozzle 310 may move with shaft 412 and maintain the desired standoff distance from component 320.
Referring to FIG. 5, in various embodiments, gas nozzle 310 may be coupled to plasma torch 500. Plasma torch 500 may be controlled by a robotic system 510 in order to deposit coating material. Gas nozzle 310 may be located at a fixed distance D2 from plasma torch 500. In various embodiments, plasma torch 500 and gas nozzle 310 may simultaneously deposit coating and remove overspray, respectively. However, in various embodiments, plasma torch 500 may deposit coating material, and robotic system 510 may subsequently direct gas nozzle 310 to remove overspray deposited by plasma torch 500. Plasma torch 500 may then deposit additional coating material where gas nozzle 310 has cleaned overspray from component 320.
Referring to FIG. 6, a flowchart of a process 600 for removing overspray is illustrated according to various embodiments. A first layer of coating material may be plasma sprayed onto a substrate (step 610). The plasma spray may further deposit overspray on the substrate. A pressurized gas may be directed at the overspray (step 620). The pressurized gas may remove the overspray from the substrate. A second layer of coating material may be plasma sprayed where the overspray was removed (Step 630).
Benefits, other advantages, and solutions to problems have been described herein with regard to specific embodiments. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent exemplary functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosure. The scope of the disclosure is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” Moreover, where a phrase similar to “at least one of A, B, or C” is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, B and C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C. Different cross-hatching is used throughout the figures to denote different parts but not necessarily to denote the same or different materials.
Systems, methods and apparatus are provided herein. In the detailed description herein, references to “one embodiment”, “an embodiment”, “various embodiments”, etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiments.
Furthermore, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112(f) unless the element is expressly recited using the phrase “means for.” As used herein, the terms “comprises”, “comprising”, or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Claims

1. A method of removing overspray comprising:

plasma spraying a substrate with a coating material, wherein the plasma spraying deposits an overspray on the substrate; and

directing a separate pressurized gas at the overspray, wherein the pressurized gas carries a media.

2. The method of claim 1, wherein the pressurized gas removes the overspray from the substrate.

3. The method of claim 1, wherein the plasma spraying comprises at least one of a suspension plasma spray and a solution precursor plasma spray.

4. The method of claim 1, wherein the pressurized gas comprises at least one of carbon dioxide, nitrogen, argon, water vapor, and compressed air.

5. The method of claim 1, wherein the media comprises at least one of dry ice particles, water, liquid nitrogen, polymer beads, alumina powder, silicon carbide powder, glass beads, walnut shells, sodium bicarbonate, and sodium bicarbonate/alumina blend.

6. The method of claim 1, wherein the pressurized gas contacts the substrate with a kinetic energy sufficient to remove the overspray and insufficient to remove the coating material.

7. The method of claim 1, further comprising plasma spraying the substrate after directing the pressurized gas at the overspray.

8. The method of claim 1, further comprising determining a standoff distance between a gas nozzle and the substrate.

9. The method of claim 1, wherein the media at least one of sublimates and evaporates at standard temperature and pressure.

10. The method of claim 1, wherein the coating is deposited with a plasma torch, and wherein the pressurized gas is sprayed with a gas nozzle.

11. The method of claim 10, wherein the gas nozzle is coupled to the plasma torch.

12. A system for coating a substrate comprising:

a plasma torch configured to deposit a coating material on a substrate; and

a gas nozzle configured to remove overspray from the substrate.

13. The system of claim 12, further comprising a positioning control system coupled to the gas nozzle.

14. The system of claim 12, wherein the plasma torch is configured to utilize at least one of a suspension plasma spray and a solution precursor plasma spray.

15. The system of claim 12, further comprising a gas supply coupled to the gas nozzle.

16. The system of claim 15, wherein the gas supply comprises at least one of carbon dioxide, nitrogen, argon, water vapor, and compressed air.

17. The system of claim 12, wherein the gas nozzle is configured to direct dry ice particles at the substrate.

18. The system of claim 12, further comprising a control system, wherein the control system is configured to maintain a standoff distance between the gas nozzle and the substrate.

19. The system of claim 12, wherein the gas nozzle is one of a plurality of gas nozzles configured to remove overspray from the substrate.

20. A method of plasma spraying a substrate comprising:

depositing a first plasma sprayed coating on a first portion of the substrate;

depositing overspray on a second portion of the substrate;

directing pressurized gas at the first portion of the substrate and at the second portion of the substrate, wherein the pressurized gas removes the overspray from the second portion of the substrate; and

depositing a second plasma sprayed coating on the second portion of the substrate.