Patent Application
20070218300
This application relates generally to applying a coating to articles, and more specifically, to an improved method of applying a coating to an article, which alleviates oxide formation and minimizes interface contamination.
Coatings capable of wear resistance and reducing the effects of high temperatures are applied to components exposed to harsh operating conditions. Application of wear resistant and environmental resistant coatings provides for improved reliability and longer component life by reducing wear of the base material and maintaining material properties at increased temperatures.
Commonly these coatings are applied by thermal spraying processes, which include detonation gun deposition, high velocity oxy-fuel deposition (HVOF) and its variants such as high velocity air-fuel, plasma spray, flame spray, and electric wire arc spray. In most thermal coating processes a material in powder, wire, or rod form (e.g., metal) is heated to near or somewhat above its melting point and droplets of the material are accelerated in a gas stream. The droplets are directed against and impinge on the surface of an article to be coated where they adhere and bond to the article.
While such processes as exemplified above do result in the coating of a target component, they also tend to facilitate interface contamination and oxide formation within the coating due to the high temperatures experienced by the casting and/or components being coated. Interface contamination and oxide formation results in reduced effectiveness and shorter life of the coating, which can contribute to premature failure and shortened effective operating life of the underlying component.
Further to the foregoing, thermal spraying processes require large fixtures, machinery and dedicated facilities, along with skilled technicians to set up and operate them. Without the ability to perform these operations in the field, valuable schedule time and added costs associated with transporting the components to a coating facility are incurred when a coating operation is desired. Additionally, some thermal spraying processes require a subsequent heat treatment for stress relieving purposes, which also requires large equipment (i.e. ovens). Resultingly, current processes do not allow coating operations to be performed in the field rather requiring the aforesaid transportation of the component to an overhaul or maintenance facility.
Accordingly, there is a need for developing a simplified coating application process that alleviates oxide formation within the coating and minimizes interface contamination.
Disclosed herein is a method of applying a coating to an article. A coating material is disposed on an article. The coating material is accelerated towards the article. And, a solid-phase bond is formed between the coating material and the article.
Further disclosed herein is a method of applying a coating to an article. A coating material is disposed on an article. The coating material is accelerated towards the article at room temperature. And, a bond is formed between the coating material and the article.
Yet further disclosed herein is a coated article having an interface between the coating and article substantially devoid of contaminants. The coated article is produced by loosely wrapping the article in a coating material. A magnetic field is created in the coating material. The coating material is accelerated toward the article with the magnetic field. And the article is impacted with the coating material to thereby fuse the coating material to the article.
Referring to the drawings wherein like elements are numbered alike in the several Figures:
Protective coatings are applied to articles exposed to harsh operating environments. These coatings provide the article with improved heat and corrosion resistance and greater wear resistance without the loss of strength. The ability to apply these coatings to articles without introducing harmful contaminants or excessive heat to the coating material allows for these coatings to remain effective throughout the planned life cycle of the articles they protect.
The method of applying coatings to articles pursuant to this disclosure is useful with a wide variety of parts and components, for example articles comprising a variety of metals and metal alloys. In various embodiments, these parts and components are operated at, or are exposed to extreme conditions, as found in, for example, but not limited to, aerospace and power generation applications. These parts and components can include turbine airfoils such as blades and vanes, combustor components such as liners and deflectors, and the like. The application of these coatings can also be performed on a portion or the entire article. For example, with regard to airfoils such as blades, the coatings can be used to protect portions of the airfoil rather than the entire airfoil, for example the coating can cover the leading and trailing edges and other surfaces of the airfoil, but not the attachment area where the airfoil is attached to a hub. While the following discussion of the method for applying coatings will be with reference to metal articles which form parts and components used in aerospace and power generation applications, it should be understood that the method of applying these coatings is useful with other articles that operate at, or are exposed to, harsh operating conditions.
A schematic representation of an airfoil is shown in
Solid-state processes, such as magnetic pulse welding, are those, which through a combination of deformation and/or diffusion allow joining to be accomplished without molten and re-solidified material in the bond area. Magnetic pulse welding is performed at room temperature conditions, without the need for heat inputs (i.e. flame, torch, electric arc, etc.) common to conventional thermal spraying processes. The high velocity impact between the two materials to be magnetic pulse welded produces a series of progressive shock waves that deform the mating surfaces at the moment of impact resulting in a solid-phase bond (that is, a bond where there is no occurrence of melting) between the two materials.
Significant advantages in coating durability are attained by applying coatings at room temperature conditions. Referring to
Still referring to
Referring to
Another significant advantage attained by the disclosed method is that a subsequent heat treatment of the coated article in not required. High temperature processes may induce stress in the application regions and therefore require a stress relieving operation. The room temperature field applicable method disclosed herein does not induce stress and thus simplifies the overall coating process. Further, the simplification of the coating process provides for reduced cycle times and lower cost.
While the invention has been described with reference to a preferred embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.
