Patent Application
20240084457
The present disclosure relates generally to composite articles and more particularly to application of metallic coatings thereupon.
Electroplating techniques are not able to produce strongly adherent coatings on composites. Thermal spray processes are generally too hot and can degrade certain types of composite articles. Current pre-plating surface treatment techniques for composite substrates rely on creation of an anchoring mechanism via chemical or mechanical means (e.g., abrasion, grit blasting, chemical etching, etc.) to alter the article surface to provide areas which are more susceptible to intermolecular bonding. Such techniques are considered satisfactory for their intended purpose. However, a need exists for improved techniques resulting in stronger adhesion of plating materials to composite articles.
A method of forming a coated composite article comprises treating a surface of a composite article to form a treated composite article having a plurality of voids in the surface, applying an expansive interface coating to the surface and plurality of voids of the treated composite article to form an intermediate composite article, the expansive interface coating comprising an expansive alloy, and applying a metallic coating to the intermediate composite article using one of electroless plating, electrolytic plating, and thermal spraying. Each void of at least a subset of the plurality of voids comprises an opening at the surface that is narrower than an inward dimension of the respective void.
A treated composite article comprises an outer surface and a plurality of voids formed in the outer surface. Each void of at least a subset of the plurality of voids comprises an opening at the outer surface that is narrower than an inward dimension of the respective void.
While the above-identified figures set forth one or more embodiments of the present disclosure, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope and spirit of the principles of the invention. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features and components not specifically shown in the drawings.
A method of producing a composite article with a metallic coating is disclosed herein. The method includes treating the article's surface to form voids therein, coating the treated surface with an expansive interface coating, and applying a protective and/or decorative metallic coating over the expansive interface coating.
The composite article (e.g., composite articles 120, 220 shown and labeled in
At step 14, an expansive interface coating can be applied to the treated composite article (e.g., articles 120 and/or 220), forming an intermediate composite article. Suitable coatings can be conductive compounds forming spacious crystal lattices (e.g., with tetrahedral coordination) such that they expand upon cooling to room temperature. Exemplary coating materials can include SAC305 (an alloy of 95.5% tin, 3% silver, and 0.5% copper), bismuth alloys, and other expansive solder alloys, to name a few non-limiting examples. Expansive interface coating material can be applied to the treated surface by soldering using a wire of the coating material, by pouring a molten material onto the surface, by cold spraying using a powder of the coating material, or by thermal spraying of a powder of the coating material, to name a few, non-limiting examples. For composites exhibiting thermal risk, such as those formed from certain polymers, molten materials should be below the glass transition temperature (T g) of the composite to avoid composite destruction. For composites with higher thermal stability, such as ceramic matrix composites, higher temperature regimes may be reached with the molten materials of the expansive interface coating. The coating material ideally fills voids (i.e., voids 124, 224) in the surface and also coats the surface. Upon cooling, the material expands, exerting a force on the walls of the voids creating an interference fit between the expansive interface coating and the composite article. Because the voids tend to be narrower at the opening than elsewhere within the void, the expansive interface coating essentially becomes anchored to the composite article by its voids. It should be understood that the expansive interface coating need not occupy each void in the surface, nor does it need to fully occupy individual voids to have the intended anchoring effect.
At step 16, the intermediate composite article can be coated with a protective and/or decorative metallic coating (i.e., plating). Such coating can be applied using an electroless or electrolytic plating technique, thermal spray (e.g., high velocity oxygen fuel or high velocity air fuel), etc. Exemplary coatings can include one or a combination of chromium, cobalt, cobalt-phosphorous, copper, nickel, nickel-phosphorous, nickel-tungsten, tungsten carbide-cobalt, tungsten carbide-cobalt chromium, etc., in a single or multi-layer arrangement. The expansive interface coating of the intermediate composite article creates a more attractive (i.e., conductive) surface, relative to the composite material, upon which the metallic coating materials can deposit.
At step 18, any desired, but optional post-processing operations can be carried out on the coated article (e.g., coated articles 130, 230). Such operations can include grinding, lapping, machining, and polishing of the metallic coating, the application of additional protective coatings, etc. The disclosed method can be used to coat composites for various purposes, including aerospace, industrial, and other transportation applications.
The following are non-exclusive descriptions of possible embodiments of the present invention.
A method of forming a coated composite article comprises treating a surface of a composite article to form a treated composite article having a plurality of voids in the surface, applying an expansive interface coating to the surface and plurality of voids of the treated composite article to form an intermediate composite article, the expansive interface coating comprising an expansive alloy, and applying a metallic coating to the intermediate composite article using one of electroless plating, electrolytic plating, and thermal spraying. Each void of at least a subset of the plurality of voids comprises an opening at the surface that is narrower than an inward dimension of the respective void.
The method of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In the above method, the step of treating the surface can include at least one of a chemical etching process and a mechanical etching process.
In any of the above methods, the step of applying the expansive interface coating can include one of soldering using a wire of the expansive alloy, pouring the expansive alloy in a molten form, cold spraying the expansive alloy as a powder, and thermal spraying the expansive alloy as a powder.
In any of the above methods, a temperature of the expansive alloy in the molten form can be less than a glass transition temperature of the composite article.
In any of the above methods, the step of applying the expansive interface coating can further include allowing the expansive interface coating to cool such that it expands and exerts a force against walls of each of the plurality of voids.
In any of the above methods, the expansive alloy can include SAC305 or a bismuth alloy.
In any of the above methods, the metallic coating can include one or a combination of cobalt, cobalt-phosphorous, copper, nickel, nickel-phosphorous, nickel-tungsten, tungsten carbide-cobalt, or tungsten carbide-cobalt chromium.
In any of the above methods, the composite article can be formed from a polymer-based material.
A treated composite article comprises an outer surface and a plurality of voids formed in the outer surface. Each void of at least a subset of the plurality of voids comprises an opening at the outer surface that is narrower than an inward dimension of the respective void.
The treated composite article of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:
In the above treated composite article, each void of at least the subset of the plurality of voids can further include at least one straight wall normal to or at an angle relative to the outer surface.
In any of the above treated composite articles, each void of at least the subset of the plurality of voids can have a columnar geometry.
In any of the above treated composite articles, each void of at least the subset of the plurality of voids can further include at least one curved wall.
In any of the above treated composite articles, each void of at least the subset of the plurality of voids can have a different geometry than a remainder of the plurality of voids.
In any of the above treated composite articles, the composite can be a polymer-based material.
In any of the above treated composite articles, the composite can be a ceramic or glass material.
An intermediate composite article can include any of the above treated composite articles and an expansive interface coating applied to the outer surface and the plurality of voids. The expansive interface coating can include an expansive alloy.
In the above intermediate composite article, the expansive interface coating can exert force on at least one wall of each of the plurality of voids.
In any of the above intermediate composite articles, the expansive alloy can include SAC305 or a bismuth alloy.
A coated composite article can include any of the above intermediate composite articles and a metallic coating applied to the expansive interface coating.
In the above coated composite article, the metallic coating can include cobalt, cobalt-phosphorous, copper, nickel, nickel-phosphorous, nickel-tungsten, tungsten carbide-cobalt, or tungsten carbide-cobalt chromium.
While the invention has been described with reference to an exemplary embodiment(s), 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(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
