| Method of removal of cores from niobium-based part -> Monitor Keywords |
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Method of removal of cores from niobium-based partRelated Patent Categories: Metal Founding, Process, Shaping Liquid Metal Against A Forming Surface, Removing Article From Forming Surface, Core RemovalMethod of removal of cores from niobium-based part description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20070181278, Method of removal of cores from niobium-based part. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] The present invention relates generally to turbine parts, and more particularly, to a cast part having passages cast therethrough. [0002] Due to the harsh environment associated with operation of a turbine engine, the parts thereof must consist of materials which can withstand the fluid speeds, temperatures, and stresses created during operation of a turbine engine. The turbine parts, especially the blades, must be constructed to satisfy minimums associated with oxidation resistance, intermediate-temperature pulverization resistance, fracture toughness, fatigue resistance, and impact resistance. Understandably, these are but a few of many design considerations which are addressed to determine the operability of a part formed of a selected material. Additionally, due to the exacting nature associated with the assembly of the turbine engine, casting performance, manufacturability, and machinability are also important considerations to the selection of a part material. [0003] It is well understood that the operating temperature of a turbine is one aspect of a turbines operating efficiency. Advanced turbine engine designs require parts formed of materials which can withstand ever-increasing operating temperatures to attain improvements in engine performance. Refractory-metal intermetallic in-situ composite materials, such as Niobium and molybdenum based silicides, possess a useful range of mechanical properties, such as low-temperature toughness as well as high-temperature strength and creep resistance. Understandably, these alloys are but two examples of refractory-metals which have been found to satisfy the ever increasing material, mechanical, and thermal demands of turbine parts. [0004] In addition to the high temperatures and pressures associated with turbine operation, a turbine generally includes a plurality of parts with relatively complex geometries. For example, a turbine often includes several cast blades, fins, and/or vanes which individually have a generally airfoil shaped cross-section. Due to the temperature associated with operation of the turbine, these parts often include cooling passages which are integrally formed in the part, usually through casting. Casting a part with integral cooling passages requires providing a mold and a core such that the passages are formed during casting of the part. Once the part is removed from the mold, the core material must be removed from the cooling passages. Several considerations must be addressed in removing the core material from the cast part. [0005] The process of removing a core material from a cast part often includes subjecting the cast part to a caustic bath. That is, when the part is formed of a nickel-based, and/or other "super-alloy", materials, the cores used for casting such parts are often formed from ceramic-based materials which including alumina, zircon, and/or silica. The material of these cores is substantially non-reactive with the material of the part during the casting process and thereby, does not detrimentally affect the quality of the part being formed. After the material of the cast part solidifies and cools, to remove the core from the part, the cores are chemically dissolved and drained from the passages of the part. [0006] The time required to chemically remove the cores significantly affects process efficiencies. The time required to remove these cores with an acidic solution is often too long to prove feasible in a dynamic processing environment. Furthermore, it has been shown the quality of the part can be adversely affected when the cores are removed with certain acidic solutions. Caustic solutions, particularly KOH and NaOH, have proven to be particularly efficient at dissolving the material of the ceramic-based cores without detrimentally affecting the quality of the nickel-based, and/or other super-alloy, parts. [0007] Parts cast from refractory-metal intermetallic in-situ composite materials such as niobium-based and molybdenum-based silicides, have been shown to possess desirable characteristics of oxidation resistance, intermediate-temperature pulverization resistance, fracture toughness, fatigue resistance, and impact resistance. Accordingly, producing parts of such materials increases the operable range of a device so equipped. However, the ceramic-based cores of silica, alumina and/or zircon usable for casting the nickel-based or other super-alloy parts reacts with these niobium-based materials during the casting process and thereby detrimentally affect the quality of the cast part. Accordingly, a core material other than the ceramic-based core material of silica, alumina and/or silica must be utilized when casting a niobium-based part. Furthermore, removal of the core material must be expeditious to allow for economical production of parts and must be accomplished without detrimentally affecting the properties of the cast part. [0008] Therefore, it would be desirable to design a system and method of producing a niobium-based material part having removable cores wherein removal of the cores is relatively rapid and does not adversely affect the quality of the part. BRIEF DESCRIPTION OF THE INVENTION [0009] The present invention provides a system and method of producing a part from a niobium-based material that solves the aforementioned problems. The system and method includes removing an yttria-based core material from the niobium-based part with any of acetic acid, hydrochloric acid, nitric acid, phosphoric acid, nitric/phosphoric acid, sulfuric acid, and/or any combination thereof. The yttria-based core material is rapidly removed from the niobium-based part and the process of removing the cores does not detrimentally affect the quality of the part. [0010] According to one aspect of the present invention, a method of removing an yttria-based core from a niobium-based part is disclosed. The method includes the step of contacting the yttria-based core with an effective amount of a composition which comprises at least one acid selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, nitric/phosphoric acid, sulfuric acid, and acetic acid. [0011] Another aspect of the present invention includes a method of casting a part. The method of casting the part includes positioning an yttria-based core within a mold, introducing a molten niobium-based alloy into the mold to cast a part, and dissolving the yttria-based core with at least one acid selected from the group consisting of acetic acid, hydrochloric acid, nitric acid, phosphoric acid, nitric/phosphoric acid, and sulfuric acid. [0012] A further aspect of the present invention includes a method of forming a turbine blade. The method of forming the turbine includes casting a blade having at least one passage defined by a core formed of an yttria-type material by pouring a niobium-type material into a mold and removing the core from the blade by contacting the core with an acid which comprises at least one acid selected from the group consisting of acetic acid, hydrochloric acid, a nitric acid, a phosphoric acid, a nitric/phosphoric acid, and a sulfuric acid. [0013] Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS [0014] The drawings illustrate one preferred embodiment presently contemplated for carrying out the invention. [0015] In the drawings: [0016] FIG. 1 is a perspective view of a turbine in partial cross-section having a plurality of cast parts according to the present invention. [0017] FIG. 2 is a perspective view of a cast blade usable with a turbine such as that shown in FIG. 1. [0018] FIG. 3 is an elevational view of a cross-section of a mold for forming a cast part such as that shown in FIG. 2. [0019] FIG. 4 is a partial cross-sectional view of the cast part along line 4-4 shown in FIG. 2. [0020] FIG. 5 is a graphical representation of the weight loss of an yttria-based core material when exposed to various acids and various acid concentrations in accordance with the present invention. [0021] FIG. 6 is a graphical representation of the removal rate of a niobium-based material when exposed to various acids and various acid concentrations in accordance with the present invention. Continue reading about Method of removal of cores from niobium-based part... Full patent description for Method of removal of cores from niobium-based part Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Method of removal of cores from niobium-based part patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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