Patent Application
20170216959
1. Field
The present application relates to gas turbines, and more particularly to a method of impact weld repair of hollow components. A support system for welding repair of components is also provided.
2. Description of the Related Art
Many cast gas turbine components, especially those along the hot gas path, are composed of high temperature materials as these materials can withstand an extremely hot and corrosive environment better than most other materials. However, current gas turbine components continue to get damaged from sustained exposure in the environment of the hot gas path and need either replacement or repair. These gas turbine components are not readily weld-repaired by processes that cause melting of the substrate, for example, arc welding processes and beam welding processes. Solidification and reheat cracking often result from such heat-dependent processes. Solid state welding provides an alternative to these processes such that these problems may be avoided. In solid state welding, the substrate is not melted; it produces coalescence at temperatures essentially below the melting point of the materials being joined.
Impact welding processes are solid state welding processes that produce a weld by a high velocity impact of the workpieces without a significant increase in the temperature of either workpiece. Examples of impact welding processes are magnetic pulse welding, explosion welding, vaporized foil actuator welding, and laser impact welding. Magnetic pulse welding uses magnetic forces to weld two workpieces together by accelerating one workpiece towards another workpiece. Explosion welding produces a weld by a high velocity impact of the workpieces as the result of a controlled detonation of explosives. Vaporized foil actuator welding is a process that rapidly vaporizes a consumable body generating a gas pressure. This gas pressure may accelerate a material at a high velocity which then collides with another material forming a weld. Laser impact welding joins two materials together using the energy of the laser to generate a pressure that may accelerate one material towards another at a high velocity creating a high impact weld.
Typically when explosion welding two components, a relatively thin clad layer, also known as a ‘flyer’, is welded using the impact from the controlled detonation to a relatively thick ‘backing’ plate. The flyer may be separated from the backing plate by a small gap. The explosive is placed on the flyer which may be contained in a frame. A detonator starts the process and the detonation progresses across an extent of the flyer. The pressures created from the detonation in the explosion welding process must be sustained by the ‘backing’ plate with the earth for support or using a supplemental support in order for a high impact weld to be formed.
US 2012/01213626 proposes to use explosion welding to form a gas turbine shroud by metallurgically applying a heat resistant cladding layer to a less heat resistant ribbed structure.
Impact welding is considered useful for joining of dissimilar metals and for the welding together of materials whose combination is not considered weldable by processes that melt and mix the substrates. Impact welding processes offer the possibility of welding gas turbine components comprising high temperature materials without the disadvantages of heat dependent fusion welding processes, as described above. However, welding of thin-walled components using high impact welding such as explosion welding has the disadvantage that the high pressure (in a typical range of 1.5 to 6.0 GPa) created by a high velocity impact may cause deformation of the thin walled portion of the component.
Briefly described, aspects of the present disclosure relate to a method of impact welding a flyer to a hollow component, a method of impact welding a cover plate to a component including a cavity, and a support system for welding repair of hollow components.
A method of impact welding a flyer to a hollow component is provided. The method includes providing the component comprising a first material and including a cavity where a weld site is disposed on a first side of the component. The first material is selected from the group consisting of superalloys, stainless steels, and high temperature nickel based alloys. An incompressible material is packed against a second side of the component opposite the first side facing the cavity. A flyer comprising a second is positioned onto the weld site. The flyer is then impact welded to the component. The incompressible material prevents the deformation of the component during the impact welding. The second material is selected from the group consisting of superalloys, stainless steels, and high temperature nickel based alloys.
A method of impact welding a cover plate to a component including a cavity is provided. The method includes providing a component comprising a first material selected from the group consisting of superalloys, stainless steels, and high temperature nickel based alloys and including a cavity. The cavity is filled with an incompressible material. A cover comprising a second material selected from the group consisting of superalloys, stainless steels, and high temperature nickel based alloys is positioned onto a weld site such that a surface of the cover plate abuts the incompressible material in the cavity. The cover plate is then impact welded to the component such that the cover plate closes the cavity. The incompressible material prevents the deformation of the cover plate.
A support system for welding repair of hollow components is provided. The support system includes a first component including a cavity, an incompressible material contained in the cavity, and a second material selected from the group consisting of superalloys, stainless steels, and high temperature nickel based alloys to be welded to the first component. The incompressible material prevents deformation of the first component or the second material during an impact welding procedure of the second material to the first component. A first material of the component is selected from the group consisting of superalloys, stainless steels and high temperature nickel based alloys.
To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods.
The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure.
After long exposures to the hot and corrosive environment of the hot gas path of a gas turbine, many cast components become damaged requiring them to either be scrapped and replaced or repaired. Fusion weld processes as discussed above are used with limited success. A method of welding hollow components using solid state welding as well as a support system for the welding repair of hollow components is provided.
In particular,
In order to weld the flyer 150 to the hollow turbine blade 120, an impact welding procedure may be used. In the embodiment shown, for example, an explosion welding procedure is used. However, one skilled in the art would understand that other forms of impact welding as described above may also be used. In the shown embodiment, an ignitable material 160 may be disposed on the outer surface of the flyer 150 such that it covers the flyer 150. Ignition of the ignitable material 160 creates a detonation that may start at a point on the outer surface of the flyer 150 and proceed from left to right in the two dimensional illustration. However, as only a cross section of the support system 100 is shown, it should also be noted that the detonation could also proceed into and out of the plane of
During an impact welding procedure, the incompressible material 130 may be used to support the hollow turbine blade 120. As pressures in the range of 1.5 to 6.0 GPa are common during impact welding procedures, the incompressible material 130 would be capable of sustaining pressures in this range during the impact welding procedure. A typical time frame for the length of an impact weld procedure may be 3 to 25 microseconds.
The incompressible material 130 may include a variety of materials that effectively prevent the deformation of the hollow component 120, 400 during an impact welding procedure. It would be desirable for the incompressible material 130 not to negatively react with the hollow component 120, 400. It would be advantageous for the incompressible material 130 to be readily drained out of the hollow component 120, 400 after the impact welding procedure. Some examples of incompressible materials 130 may be water, sand, dry ice, sodium potassium (NaK), oil, polymer, and wax.
The configuration of the flyer 150 with respect to the hollow component 120 may be parallel, as shown in
Similarly to the embodiment of
Referring to
In the embodiment illustrated in
Prior to the positioning, the weld site 140 may be excavated such that damaged material is removed.
In an embodiment, the flyer 150, 450 may be positioned parallel to the hollow component 120, 400. In another embodiment, the flyer 150, 450 may be positioned at a slight angle to the hollow component 120, 400. The slight angle may be in a range of 5 to 20 degrees. Such a slight angle may be used to control the direction of the weld progression during impact welding.
In the shown embodiment in
After the impact welding, the welded second material may be machined in order for the outer contour of the second material to conform to the desired contour of the hollow turbine blade 120. An embodiment of the weld 300 after a machining is illustrated in
Referring to
The detonation 470 may begin at a single point on the surface at the periphery of the cover plate 450 and proceed across the surface as shown in
In the embodiment shown in
While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.
