Patent Application
20190033138
The present disclosure relates generally to plasma spraying and, more particularly, to equipment for workpiece temperature control during plasma spraying.
Superalloy components in various industries, including components for gas turbine engines are often protected by thermal barrier coatings (TBCs). Driven in part by higher inlet temperature requirements of modern gas turbine engines, high volume production of TBC components has attracted greater attention.
The TBC is often applied by plasma spray coating processes such as suspension plasma spray (SPS) and solution precursor plasma spray (SPPS). Substrate temperature plays a significant role in the coating microstructure as well as substrate adherence. The coating material is typically deposited by a torch “scan” over the substrate. The torch makes passes over the substrate at a predefined distance to control both deposition and temperature in the application area. In many plasma deposition applications, workpieces are attached to a turntable that is rotated as the plasma torch is vertically scanned. This configuration facilitates deposition and temperature distribution as the distance can be adjusted continuously to reduce thermal shock. This may be advantageous due to the thermal expansion mismatch between the ceramic coating application on a metallic substrate.
Multi-layer coatings provide enhanced capability as certain materials and microstructures may be designed for each layer based on application requirements with regard to coating spall. The deposition of different materials is achieved by switching between materials for each layer. At each switch, sufficient time needs to be apportioned for the torch to reach a desirable steady state to minimize coating process defects. Allotting the required time may result in a non-uniform substrate temperature decrease due to the workpiece complexities. This may disadvantageously affect the coating microstructure and increase the potential for thermal shock during application.
A plasma spray system according to one disclosed non-limiting embodiment of the present disclosure includes a temperature sensor operable to determine a temperature of a workpiece in a measurement zone; a heater operable to selectively heat the workpiece in a heating zone downstream of the measurement zone; a plasma spray subsystem operable to plasma spray the workpiece in an application zone downstream of the heating zone; and a control in communication with the plasma spray subsystem, the temperature sensor, and the heater, the control operable to control the heater to heat the workpiece in the heating zone in response to the temperature of the workpiece in the measurement zone such that the workpiece in the application zone is at a desired temperature to receive the plasma spray.
A further aspect of the present disclosure includes a turntable to which the workpiece is mounted.
A further aspect of the present disclosure includes a turntable operable to move the workpiece with respect to the temperature sensor, the heater, and the plasma spray subsystem such that the workpiece sequentially traverses through the measurement zone, the heating zone, then the application zone.
A further aspect of the present disclosure includes wherein the application zone is about 0.5 inches (12.7 millimeters) in diameter on the workpiece.
A further aspect of the present disclosure includes wherein the temperature sensor is an infrared camera.
A further aspect of the present disclosure includes wherein the heater is an infrared heater.
A further aspect of the present disclosure includes a chiller in communication with the control, the chiller operable to selectively cool the workpiece in a cooling zone downstream of the measurement zone.
A further aspect of the present disclosure includes wherein the chiller includes a compressed air system to spray cool air.
A further aspect of the present disclosure includes wherein the compressed air is sprayed onto a backside of the workpiece to define a cooling zone upstream of the application zone opposite the heating zone.
A further aspect of the present disclosure includes wherein the measurement zone is upstream of the heating zone.
A further aspect of the present disclosure includes wherein the measurement zone is upstream of the heating zone and the heating zone if upstream of the application zone.
A method for plasma spraying a workpiece according to one disclosed non-limiting embodiment of the present disclosure includes sensing a temperature in a measurement zone on a workpiece; heating the workpiece in a heating zone downstream of the measurement zone to a desired temperature in response to the sensing; and applying a plasma spray coating to the workpiece downstream of the heating zone such that the workpiece in the application zone is at a desired temperature to receive the plasma spray.
A further aspect of the present disclosure includes moving the workpiece to sequentially traverse the workpiece with respect to the measurement zone, the heating zone, and then the application zone.
A further aspect of the present disclosure includes maintaining a sequential relationship of the measurement zone, the heating zone, and the application zone on the workpiece.
A further aspect of the present disclosure includes sizing the measurement zone, the heating zone, and the application zone on the workpiece to be equivalent.
A further aspect of the present disclosure includes cooling a cooling zone on the workpiece downstream of the measurement zone to a desired temperature in response to the sensing.
A further aspect of the present disclosure includes wherein the cooling zone is on a backside of the workpiece opposite the heating zone, either the heating or cooling being performed to obtain the desired temperature in response to the sensing.
A further aspect of the present disclosure includes wherein the measurement zone, the heating zone, and the application zone are about the same size.
A further aspect of the present disclosure includes wherein the measurement zone, the heating zone, and the application zone are arranged horizontally.
A further aspect of the present disclosure includes wherein the measurement zone, the heating zone, and the application zone are each about 0.5 inches (12.7 millimeters) in diameter.
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 of the invention will become more apparent in light of the following description and the accompanying drawings. It should be appreciated, however, that the following description and drawings are intended to be exemplary in nature and non-limiting.
Various features will become apparent to those skilled in the art from the following detailed description of the disclosed non-limiting embodiments. The drawings that accompany the detailed description can be briefly described as follows:
In various embodiments, the plasma coating may be deposited onto the workpiece W with a suspension plasma spraying (“SPS”) process. SPS involves dispersing a ceramic feedstock into a liquid suspension prior to injection into a plasma torch. The coating material may be deposited, for example, by a solution precursor plasma spray (“SPPS”) process, in which a solution of coating precursors is atomized and injected into a direct current (DC) plasma torch. SPPS refers to a specific process where the feedstock is a solution of salts in a solvent. The solution is injected into the plasma stream and the droplets go through chemical and physical changes, including pyrolization, to form particles and deposit the coating. SPS refers to the use of a solution where nanometer sized particles are suspended in a fluid, either solvent or water based. The solution is then injected into the plasma and the fluid carrier is burned off and the particles become molten or semi-molten and build up to form the coating. The feedstocks of the two coatings may thus be different. It should be appreciated that the plasma spray system 20 can be used for other materials as well as blended materials, either two dissimilar ceramics or a metallic and ceramic.
The plasma spray system 20 generally includes a suspension bay 22, a feeder bay 24 and at least one spray booth 26. It should be appreciated that various other arrangements as well as additional or alternative bays will also benefit herefrom.
The suspension bay 22 generally stores containers 30 of materials in a space segregated within the plasma spray system 20. Although illustrated as two different materials in two different supplies for a multi-layer thermal barrier coating, it should be appreciated that any number of different material supplies will benefit herefrom. The feedstock materials for the thermal barrier coating are stored within the suspension bay 22 and may include an ethanol-based or water-based system for a plasma sprayed thermal barrier coating that includes, for example, yttria-stabilized zirconia (YSZ) which is a zirconium-oxide based ceramic powder, gadolinium zirconate (GdZ) and an ethanol (Eth) carrier. The feedstock materials may be, for example, fully premixed outside of this system into a single container or as separate parts in separate containers then mixed in the mixing units 32 before communication to the feeder bay 24.
The feeder bay 24 generally includes pumps 40 and a feeder system 42 for each spray booth 26 to supply materials thereto and provide individual control. The spray booth 26 generally includes a plasma spray subsystem 50, a turntable subsystem 52, a wash subsystem 54, a collection subsystem 56, and a control subsystem 58. It should be appreciated that various other architectures to receive various other workpieces will also benefit herefrom.
The plasma spray subsystem 50 includes a robotic manipulated plasma spray torch 60 operated by the control subsystem 58. The plasma spray torch 60 is operable to apply a plasma sprayed thermal barrier coating supplied from the suspension bay 22 by the feeder bay 24. The plasma spray torch 60 may use axial, radial, and other combinations of injection modes to coat the workpieces W as the turntable subsystem 52 rotates about axis T to provide relatively high manufacturing rates at significant deposition efficiencies.
The turntable subsystem 52 generally includes a multiple of turntables 62, each of which is operable to position the multiple of workpieces W with respect to the plasma spray torch 60. That is, one turntable 62A supports the workpieces W for the plasma spray operation while one or more other turntables 62B, 62C undergo workpiece W load/unload operations. The plasma spray torch 60 is thereby essentially always in operation to maximize production capacity and efficiency.
With reference to
With reference also to
The heater 74 is operable to selectively heat the workpiece W at a heating zone 94 in response to the control 70 determining the temperature of the workpiece W in the measurement zone 92. The heating zone 94 is downstream of the measurement zone 92. The heater 74 may be, for example, an infrared heater with a parabolic reflector 100 to locally heat the heating zone 94 on a front side 200 of the workpiece W that is being coated. The heater 74 may be robotically manipulated in conjunction with the plasma spray torch 60 by the control subsystem 58 to maintain a sequential relationship between the heating zone 94, the measurement zone 92, and the application zone 90. That is, the spatial relationship between the measurement zone 92, the heating zone 94, and the application zone 90 may be maintained relative to each other as the workpiece W is moved by the turntable 62 with respect thereto. The measurement zone 92 is upstream of the heating zone 94, and the heating zone 94 is upstream of application zone 90. Alternatively, the spatial relationship of the measurement zone 92, the heating zone 94, and the application zone 90 may be adjusted by the control 70 to optimize application. The heating zone 94, for example may be about 0.5 inches (12.7 millimeters) in diameter on the workpiece W.
The chiller 76 is operable to selectively cool an area of the workpiece W at a cooling zone 96 in response to the control 70. The chiller 76, for example, may be a compressed air system to spray cool air onto a backside 202 of the workpiece W from an air jet 110 to define the cooling zone 96. The chiller 76 may also be robotically manipulated in conjunction with the plasma spray torch 60 by the control subsystem 58 to maintain a sequential relationship between the cooling zone 96, the heating zone 94, the measurement zone 92, and the application zone 90. The cooling zone 96, for example, may be about 0.5 inches (12.7 millimeters) in diameter on the workpiece W. The cooling zone 96 may be directly opposite the heating zone 94 to affect an opposite side of the workpiece W. Typically, only the chiller 76 or the heater 74 will be operational at one time to adjust the temperature of the workpiece W upstream of the application zone 90 but downstream of the measurement zone 92. The control 70 is operable to determine the necessary cooling or heating to assure that that application zone 90 is at an optimal temperature to receive the plasma spray in the application zone 90 of an area of the workpiece W at application of the thermal barrier coating.
With reference to
Initially, in one embodiment, the workpiece W may begin (302;
Next, the entire workpiece W is preheated (304;
Next, the plasma spray torch 60 applies (306;
As the first layer of a multi-layer ceramic coating is applied to the preheated workpiece W, the temperature of the workpiece W remains relatively stable and uniform during application of the first layer. The workpiece W typically has a relatively complicated geometry. The complicated geometry results in the workpiece W cooling in a non-uniform manner which may potentially result in a temperature gradient (204:
With reference to
Next, as the second layer of the coating is then being applied (308;
In one embodiment, an infrared heater can emit light at different wavelengths. To heat the surface of the ceramic layer, a relatively longer wavelength may be utilized. To heat the substrate through the ceramic layer, a relatively shorter wavelength may be utilized such that the ceramic layer would essentially be transparent to the heater 74.
The plasma spray torch 60 then applies (408) the plasma coating in the application zone 90 which has been temperature adjusted. The process then continues as the turntable 62 is rotated about an axis T to move the workpiece W with respect to the temperature sensor 72, the heater 74, the chiller 76, and the plasma spray torch 60. The temperature sensor 72, the heater 74, the chiller 76, and the plasma spray torch 60 may then be traversed vertically to proceed across the next horizontal scan of the workpiece as the turntable rotates.
Although the different non-limiting embodiments have specific illustrated components, the embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from any of the non-limiting embodiments in combination with features or components from any of the other non-limiting embodiments.
It should be appreciated that relative positional terms such as “upstream,” “aft,” “upper,” “lower,” “above,” “below,” and the like are with reference to the normal operational attitude of the vehicle and should not be considered otherwise limiting.
It should be appreciated that like reference numerals identify corresponding or similar elements throughout the several drawings. It should also be appreciated that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom.
Although particular step sequences are shown, described, and claimed, it should be appreciated that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present disclosure.
The foregoing description is exemplary rather than defined by the limitations within. Various non-limiting embodiments are disclosed herein, however, one of ordinary skill in the art would recognize that various modifications and variations in light of the above teachings will fall within the scope of the appended claims. It is therefore to be appreciated that within the scope of the appended claims, the disclosure may be practiced other than as specifically described. For that reason the appended claims should be studied to determine true scope and content.
