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Investment casting cores and methods

Investment casting cores and methods description/claims

The disclosure relates to investment casting. More particularly, it relates to the investment casting of superalloy turbine engine components.

Investment casting is a commonly used technique for forming metallic components having complex geometries, especially hollow components, and is used in the fabrication of superalloy gas turbine engine components.

Gas turbine engines are widely used in aircraft propulsion, electric power generation, and ship propulsion. In gas turbine engine applications, efficiency is a prime objective. Improved gas turbine engine efficiency can be obtained by operating at higher temperatures, however current operating temperatures in the turbine section exceed the melting points of the superalloy materials used in turbine components. Consequently, it is a general practice to provide air cooling. Cooling is provided by flowing relatively cool air from the compressor section of the engine through passages in the turbine components to be cooled. Such cooling comes with an associated cost in engine efficiency. Consequently, there is a strong desire to provide enhanced specific cooling, maximizing the amount of cooling benefit obtained from a given amount of cooling air. This may be obtained by the use of fine, precisely located, cooling passageway sections.

The cooling passageway sections may be cast over casting cores. Ceramic casting cores may be formed by molding a mixture of ceramic powder and binder material by injecting the mixture into hardened steel dies. After removal from the dies, the green cores are thermally post-processed to remove the binder and fired to sinter the ceramic powder together. The trend toward finer cooling features has taxed core manufacturing techniques. The fine features may be difficult to manufacture and/or, once manufactured, may prove fragile. Commonly-assigned U.S. Pat. Nos. 6,637,500 of Shah et al. and 6,929,054 of Beals et al (the disclosures of which are incorporated by reference herein as if set forth at length) disclose use of ceramic and refractory metal core combinations.

One aspect of the disclosure involves a method wherein a core assembly is formed. The forming includes deforming a wire, the deforming including increasing a transverse linear dimension along at least one portion of the wire. The wire is assembled to a ceramic core.

Another aspect of the disclosure involves a method wherein a core assembly is formed. The forming includes deforming a wire. The wire is assembled to a ceramic core. The assembling includes inserting an intermediate portion of the wire into a compartment of the ceramic core.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will be apparent from the description and drawings, and from the claims.

FIG. 1 is a view of a first core assembly.

FIG. 2 is a cutaway view of the assembly of FIG. 1.

FIG. 3 is a view of a shelled pattern including the assembly of FIG. 2.

FIG. 4 is a sectional view of a casting formed from the shelled pattern of FIG. 3.

FIG. 5 is a transverse sectional view of the casting of FIG. 4, taken along line 5-5.

FIG. 6 is a transverse sectional view of an alternate casting.

FIG. 7 is a view of an RMC protuberance associated with the alternate casting of FIG. 6.

FIG. 8 is a plan view of an alternate RMC.

FIG. 9 is a side cutaway view of a shelled pattern including the RMC of FIG. 8.

FIG. 10 is a sectional view of a casting formed by the shelled pattern of FIG. 9.

• Provisional Patent
• Utility Patent

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