Patent Application
20150211372
The present disclosure generally pertains to gas turbine engines, and is more particularly directed toward a process for manufacturing gas turbine blades.
Gas turbine engines include compressor, combustor, and turbine sections. Turbine blades of a gas turbine engine are subject to high temperatures. In particular, turbine blades undergo considerable wear during operation and may require repair for continued use. Certain methods and processes may be performed during manufacture of the turbine blades to reduce the need for future repair.
U.S. Pat. No. 5,951,792 to W. Balbach et al. discloses a method for welding age-hardenable nickel-base alloys. A workpiece made from an age-hardenable nickel-base alloy is welded from filler material of the same composition as the base material. The weld metal which is formed in so doing is covered by a sealed covering layer comprising a ductile material and the workpiece is subjected to hot isostatic pressing (HIP).
The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors.
A method of manufacturing a shrouded turbine blade is disclosed. In an embodiment, the method comprises casting a shrouded turbine blade including a shrouding. The shrouding includes an abutment face. The method includes welding a coating composed of a different material than the shrouded turbine blade onto the abutment face. The method includes applying hot isostatic pressing to the abutment face after welding the coating. The hot isostatic pressing is sufficient to heal internal defects in the abutment face. The method includes machining the shrouded turbine blade after applying hot isostatic pressing.
The systems and methods disclosed herein include a method for manufacturing a shrouded turbine blade. The shrouded turbine blade may be used in a gas turbine engine including a turbine section. The method may include casting a shrouded turbine blade including a shrouding. The shrouding may be attached to an airfoil of the shrouded turbine blade, and may also include an abutment face. The method may include welding a coating composed of a different material than the shrouded turbine blade onto the abutment face. The method may include applying hot isostatic pressing to the abutment face after welding the coating. The hot isostatic pressing may be sufficient to heal internal defects in the abutment face. The method may include machining the shrouded turbine blade after applying hot isostatic pressing.
In addition, the disclosure may generally reference a center axis 95 of rotation of the gas turbine engine, which may be generally defined by the longitudinal axis of its shaft 120 (supported by a plurality of bearing assemblies 150). The center axis 95 may be common to or shared with various other engine concentric components. All references to radial, axial, and circumferential directions and measures refer to center axis 95, unless specified otherwise, and terms such as “inner” and “outer” generally indicate a lesser or greater radial distance from, wherein a radial 96 may be in any direction perpendicular and radiating outward from center axis 95.
A gas turbine engine 100 includes an inlet 110, a shaft 120, a gas producer or “compressor” 200, a combustor 300, a turbine 400, an exhaust 500, and a power output coupling 600. The gas turbine engine 100 may have a single shaft or a dual shaft configuration.
The compressor 200 includes a compressor rotor assembly 210 and compressor stationary vanes (“stators”) 250. The compressor rotor assembly 210 mechanically couples to shaft 120. As illustrated, the compressor rotor assembly 210 is an axial flow rotor assembly. The compressor rotor assembly 210 includes one or more compressor disk assemblies 220. Each compressor disk assembly 220 includes a compressor rotor disk that is circumferentially populated with compressor rotor blades. Stators 250 axially precede each of the compressor disk assemblies 220. Each compressor disk assembly 220 paired with the adjacent stators 250 that precede the compressor disk assembly 220 is considered a compressor stage. Compressor 200 includes multiple compressor stages.
The combustor 300 includes one or more injectors 310 and includes one or more combustion chambers 390.
Certain aspects of the turbine rotor assembly will be described with reference to
As illustrated in
One or more of the above components (or their subcomponents) may be made from a base material that is stainless steel and/or durable, high temperature materials known as “superalloys”. A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures, good surface stability, and corrosion and oxidation resistance.
Superalloys may include materials such as alloy x, WASPALOY, RENE alloys, alloy 188, alloy 230, INCOLOY, INCONEL, MP98T, TMS alloys, and CMSX single crystal alloys.
As shown in
Gas turbine engines may be suited for any number of industrial applications such as various aspects of the oil and gas industry (including transmission, gathering, storage, withdrawal, and lifting of oil and natural gas), the power generation industry, cogeneration, aerospace, and other transportation industries.
Turbine blades are subject to high stress and defects in the blade due to high operating temperatures. In embodiments with a shrouding, the shrouding in particular may reach the maximum velocity of the turbine blade and thus may be subject to the highest stress. Turbine blades are often routinely serviced to repair defects found internally and/or on the surface of the turbine blade. Such repair may be costly and time consuming.
In some embodiments, casting in Step 801 may be performed via a multitude of casting methods including, but not limited to, die casting, investment casting, centrifugal casting, continuous casting, and permanent mold casting. In embodiments where the shrouded turbine blade is casted by investment casting, a ceramic mold may be created from a wax mold. The wax mold may be melted and replaced with molten metal to form the shrouded turbine blade. Die casting, on the other hand, involves forcing molten metal under high pressure into a mold cavity, wherein the mold cavity consists of two hardened tool steel dies machined to a particular shape. During the casting process, varying types of casting defects may arise. Casting defects may include shrinkage defects, gas bubbles, porosity, misruns, cold shuts, tears, and spots. Casting defects may be detected by conventional surface crack detection methods. In some instances, sectioning of the shrouded turbine blade may be used to detect internal defects, particularly in heat affected zones of the shrouded turbine blade. An example of a casted shrouded turbine blade including a shrouding with an abutment face is shown in
In some embodiments, welding the weld coating in Step 802 may be performed via a multitude of welding methods including, but not limited to, arc welding, gas welding, electric resistance welding, laser beam welding, electromagnetic pulse welding, and friction stir welding. Welding joins metals together by melting a filler material and the base metal. Welding material for the weld coating may include cobalt, nickel, tungsten, chromium, molybdenum, steel, and/or aluminum. In some embodiments, the weld coating may be coated onto the abutment face by some other bonding means. An example of a weld coating applied onto an abutment face of a shrouding is shown in
In some embodiments, internal defects such as cracks or voids may exist between the weld coating and the abutment face. An example of such an embodiment can be seen by internal crack 480 in
By applying hot isostatic pressing in Step 803, defects such as internal crack 480 of
Some HIP systems may include a monolithic forged steel autoclave sealed by a threaded top closure in which the inert gas is pumped. Other HIP systems may include a multi-wall forged, relatively thin-walled vessels surrounded by tight fitting forged steel rings, or steel wire wound. In the steel wire wound system, the radial forces are taken up by a forged steel cylinder pre-stressed with high strength steel wire. The axial forces are transferred through the two moving closures to the external frame which is also pre-stressed with the wire winding. Pressure may be sealed within the vessel using Bridgman seals, metal-to-metal seals, single or double O-rings, or a combination of seals. The pre-stressing causes the pressure vessel wall to remain in residual compression even at maximum operating temperature, eliminating tensile loads, and preventing crack propagation and brittle failure.
The furnace of the HIP system may consist of resistance heater elements arranged in multiple, independently controlled zones. The choice of furnace and heater element materials may depend on the material being hot isostatic pressed and the temperature. For temperatures up to 1350° C., Fe—Cr—Al alloys may be used as heater elements. Molybdenum can be used in the temperature range 500-1600° C., and graphite for temperatures from 400 to 2200° C. or higher. For cooling, quench furnaces may be equipped with a forced convection system which circulates cooler gas through the work zone.
Machining in Step 804 may be performed to remove excess weld coating from the abutment face of the shrouding. Machining may remove any large weld beads that are left on the surface after welding in Step 803. Machining may result in a clean surface finish as shown by machined surface 482 in
In some embodiments, a heat treatment process may occur after hot isostatic pressing in Step 803. The heat treatment process may alter physical and mechanical properties of the shrouded turbine blade without changing the shape. Furthermore, the heat treatment process involves heating the shrouded turbine blade to a suitable temperature, holding it at that temperature long enough to cause one or more constituents to enter into a solid solution, and then cooling it rapidly enough to hold these constituents in solution. Subsequent precipitation heat treatments allow controlled release of these constituents either naturally (at room temperature) or artificially (at higher temperatures).
In some embodiments, the method of manufacturing a shrouded turbine blade follows a sequential order of Step 801, Step 802, Step 803, and Step 804. Alternatively, the method of manufacturing a shrouded turbine blade follows a different order. In other embodiments, the method of manufacturing a shrouded turbine blade may not include all of the Steps 801-804. Additionally, the method of manufacturing a shrouded turbine blade may repeat one or more of the Steps 801-804. Alternatively, an embodiment including some or all of the Steps 801-804 may be used to manufacture other turbine components, such as non-shrouded turbine blades, turbine disks, turbine diaphragms, or turbine nozzles.
In some instances, the method above may be used to repair turbine blades. In such instances, the used turbine blade may be repaired by welding a coating of a different material than the used turbine blade onto a high wear surface of the used turbine blade, applying HIP to the high wear surface after welding the coating, and apply final machining after applying HIP. The high wear surface may include surfaces which undergo a large amount of friction during operation. The coating welded onto the high wear surface may provide a protective layer to resist the large amount of friction. Additionally, the HIP process may heal internal cracks that may form between the coating and the high wear surface. The final machining may remove any excess material of the coating.
In instances of prior methods where Step 802 occurs before Step 803, the internal defects formed in the abutment face and the coating may not be cured before machining in Step 804. Applying the HIP process in Step 803 after Step 802 may ensure internal defects between the coating and the abutment face are cured. In instances where Step 804 occurs before Step 803, internal cracks in the abutment face after welding may open up into the exterior surface of the abutment face after machining. This may result in an ineffective HIP process if there are externally exposed cracks.
The preceding detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. The above description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles described herein can be applied to other embodiments without departing from the spirit or scope of the invention. Thus, it is to be understood that the description and drawings presented herein represent a presently preferred embodiment of the invention and are therefore representative of the subject matter which is broadly contemplated by the present invention. It is further understood that the scope of the present invention fully encompasses other embodiments that may become obvious to those skilled in the art and that the scope of the present invention is accordingly limited by nothing other than the appended claims.
