Patent Application
20170370221
The present invention generally relates to methods for repairing an airfoil of an engine and, more particularly, to methods of rebuilding the component to include film holes not present in the original component.
In order to increase the efficiency and the performance of gas turbine engines so as to provide increased thrust-to-weight ratios, lower emissions and improved specific fuel consumption, turbine engines are tasked to operate at higher temperatures. The components operating within the hot gas sections of the gas turbine engines are subjected to oxidation and thermo-mechanical fatigue amongst other life reducing causes, resulting in repair needs and issues. Typically, components that are damaged beyond repair are replaced with a new component, thereby increasing down-time and costs.
Various components within the gas turbine engine, including certain stator vanes (e.g., turbine nozzles) and rotor blades (e.g., turbine blades), are film cooled across certain areas of the component. Even still, areas of the component can be damaged over time forming distressed areas on the component over time during use. However, the replacement component, in operation, would be subjected to the same fate after its use in the engine. Thus, additional repair and replacement would be required.
Accordingly, it is desirable to provide improved repair methods for turbine components that enable improved cycle times and reduced costs without sacrificing component performance or durability.
Objects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
Methods are generally provided for repairing a component having a damaged region. In one embodiment, the method includes removing the damaged portion from the component to form an intermediate component, wherein the damaged portion has an original geometry; and applying using additive manufacturing a repaired portion onto the intermediate component to form a repaired component. Generally, the repaired portion has a repaired geometry that includes at least one film hole absent in the original geometry, with the film holes being fluidly connected to a cooling supply of the repaired component.
Other features and aspects of the present invention are discussed in greater detail below.
The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:
Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.
Reference now will be made to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of an explanation of the invention, not as a limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as one embodiment can be used on another embodiment to yield still a further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only, and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied exemplary constructions.
Methods are generally provided for repairing a component having a damaged region, particularly for a component of an engine (e.g., a gas turbine engine). In one embodiment, a damaged portion of the component is first removed to form an intermediate component, and then repaired using additive manufacturing to form a repaired portion on the intermediate component. The repaired portion has a geometry that includes at least one film hole absent in the original damaged geometry (previously removed), with the film holes being fluidly connected to a cooling supply of the repaired component. Generally, the repaired portion is formed via additive manufacturing to include the film hole(s) without any additional drilling or other hole forming operation due to the layer by layer formation additive manufacturing process. As such, the component can be repaired to include additional film holes not present in the original component in order to serve as a corrective action to relieve the causation of the original damaged region.
Referring to the drawings,
The component 5 of
Generally, the damaged portion 10 has an original geometry that was present in its pre-damaged state, which may or may not be the same as the geometry of its damaged state (e.g., a damaged geometry). In certain embodiments, the original geometry is substantially free from cooling holes (e.g., film holes) within the damaged portion 10 (as shown), although other embodiments may include film holes within the damaged geometry.
In one embodiment, the airfoil 6 of the turbine blade 5 of
The airfoil 6 of the turbine blade 5 of
Referring to
As such, it can be ensured that the entire damaged portion 10 can be removed to form the intermediate component 20. For example, other material can be removed in order to result in the intermediate component 20 having known dimensions, particularly having known dimensions defining the cavity 22. For example, the intermediate component 20 can have a predetermined height from which the repaired component 30 of
In one embodiment, the damaged portion 10 of the component 5 is cleaned prior to removing the damaged portion 10 in order to first remove any coatings or other external layers present. For example, thermal barrier coatings (TBC) 18 may be removed from the damaged portion 10.
In particular embodiments, removal of the damaged portion 10 can be achieved by machining the component 5 around the damaged portion 10 to result in the intermediate component 20 of
Referring to
In order to form the repaired component 30, the repaired portion 31 is formed via an additive manufacturing process, either directly onto the intermediate component 20 (e.g., applied layer by layer directly onto the surfaces 24 of the cavity 22) or formed separately from the intermediate component 20 and subsequently bonded onto the surfaces 24 of the cavity 22. In either method, the use of additive manufacturing allows for the repaired portion 31 to have a repaired geometry that is different than the original geometry of the component 5 and/or of the damaged geometry of the damaged portion 10. For example, in the particular embodiment shown in
The repaired portion 31 may be formed from a material that has a substantially identical composition than the material of the component 5 (e.g., the same superalloy). Alternatively, the repaired portion 31 may be formed from a material that is different in composition than the material of the component 5 (e.g., different superalloy). However, when using different materials, the coefficient of thermal expansion (CTE) should be tailored to be close to each other to keep the material from spalling during use in the operating conditions of a turbine engine.
In one embodiment, the repaired portion 30 is formed via a direct metal laser fusion process, which is a laser-based rapid prototyping and tooling process utilizing precision melting and solidification of powdered metal into successive layers of larger structures, each layer corresponding to a cross-sectional layer of the 3D component. As known in the art, the direct metal laser fusion system relies upon a design model that may be defined in any suitable manner (e.g., designed with computer aided design (CAD) software). The model may include 3D numeric coordinates of the entire configuration of the component including both external and internal surfaces of an airfoil, platform and dovetail, as well as any internal channels and openings. In one exemplary embodiment, the model may include a number of successive 2D cross-sectional slices that together form the 3D component. Particularly, such a model includes the successive 2D cross-sectional slices corresponding to the turbine component from the machined height. For example, the intermediate component 20 can be imaged to create a digital representation of the intermediate component 20 after removal of the damaged portion 10, and a CAD model can be utilized to form the repaired portion 32 thereon.
Any suitable laser and laser parameters may be used, including considerations with respect to power, laser beam spot size, and scanning velocity. The build material may be formed by any suitable powder, including powdered metals, such as a stainless steel powder, and alloys and super alloy materials, such as nickel-based or cobalt superalloys. In one exemplary embodiment, the build material is a high temperature nickel base super alloy. The powder build material may be selected for enhanced strength, durability, and useful life, particularly at high temperatures. Each successive layer may be, for example, between 10 μm and 200 μm, although the thickness may be selected based on any number of parameters.
As noted above, the repaired component 30 includes internal cooling passages that deliver a cooling flow to the film holes 32. The cooling passages may be relatively complex and intricate for tailoring the use of the limited pressurized cooling air and maximizing the cooling effectiveness thereof and the overall engine efficiency. However, the successive, additive nature of the laser fusion process enables the construction of these passages.
Although the direct metal laser fusion process is described above, other rapid prototyping or additive layer manufacturing processes may be used to apply and form the repaired portion 32, including micro-pen deposition in which liquid media is dispensed with precision at the pen tip and then cured; selective laser sintering in which a laser is used to sinter a powder media in precisely controlled locations; laser wire deposition in which a wire feedstock is melted by a laser and then deposited and solidified in precise locations to build the product; electron beam melting; laser engineered net shaping; direct metal laser sintering; and direct metal deposition. In general, additive repair techniques provide flexibility in free-form fabrication and repair without geometric constraints, fast material processing time, and innovative joining techniques.
Other post processing may be performed on the repaired component 30, such as stress relief heat treatments, peening, polishing, hot isostatic pressing (HIP), or coatings.
Although described above and in
These and other modifications and variations to the present invention may be practiced by those of ordinary skill in the art, without departing from the spirit and scope of the present invention, which is more particularly set forth in the appended claims. In addition, it should be understood the aspects of the various embodiments may be interchanged both in whole or in part. Furthermore, those of ordinary skill in the art will appreciate that the foregoing description is by way of example only, and is not intended to limit the invention so further described in the appended claims.
