Composite Core Structure for Complex Turbine Airfoil Passages
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Solution Overview
Problem
Conventional ceramic cores used in investment casting are fragile, prone to warpage and fracture, and result in low casting yields due to their limitations in designing complex geometries and internal cooling passages, especially in advanced gas turbine engine components.
Innovation Solution
A composite core is formed by combining refractory metal and ceramic materials, where refractory metal cores are used for reinforcement and to create complex features, and ceramic layers are applied for protection against oxidation and erosion, using a TOMO-lithographic process to create precise and durable core structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ceramic cores are used in investment casting, then the casting process can be performed, but the cores are fragile and prone to warpage and fracture resulting in low casting yields
Solution Approach 1:
The patent applies composite materials by combining refractory metal (such as molybdenum, tungsten, or niobium) with ceramic materials to create a composite core. The refractory metal provides strength and structural integrity while the ceramic provides heat resistance. This composite structure resolves the contradiction by maintaining core strength under thermal stress while preventing warpage and fracture, thereby improving casting yield.
2Adaptability or versatility
If conventional ceramic cores are used, then simple geometries can be formed, but complex internal cooling passages and intricate features cannot be created
Solution Approach 1:
The patent applies local quality by creating a master pattern with varying material properties - using rigid materials for structural sections and flexible materials for sections requiring complex geometry formation. This allows different regions of the core to have optimized properties: structural integrity where needed and flexibility where complex passages are formed, enabling intricate features while maintaining manufacturability.
Solution Approach 2:
The patent segments the core into a composite structure with refractory metal providing the structural framework and ceramic providing the heat-resistant casting surface. This segmentation allows each material to perform its optimal function, enabling complex geometries in the ceramic portion while the metal framework maintains overall structural integrity during manufacturing.
3Strength
If refractory metal cores are used for strength and complex features, then core robustness improves, but protection against oxidation and erosion is reduced
Solution Approach 1:
The patent uses composite materials where the refractory metal core provides structural strength and robustness, while the ceramic outer layer provides protection against oxidation and erosion from molten metal. This composite structure resolves the contradiction by combining materials with complementary properties - the metal framework ensures structural integrity while the ceramic coating protects against harmful environmental factors during casting.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The composite core enhances the robustness and precision of the casting process, allowing for higher casting yields and improved mechanical properties, while maintaining low production costs and enabling the creation of intricate features that would be difficult with ceramic cores alone.
Implementation Method 1
The green body is then sintered in a sintering furnace to form the refractory metal core
Implementation Method 2
The ceramic slurry is then fired at a temperature sufficient to bond the ceramic particles together and form a protective coating on the refractory metal core
Data Source
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AI summary
A method of making a composite core (220) includes forming first (222) and second (224) cores of refractory metal and ceramic material. Each of the first (222) and second (224) cores is formed with two layers of a material. The layers are bonded together to form a laminate master pattern, and a flexible mold is formed around the pattern. The pattern is removed from the flexible mold, and slurry material, either pulverulent refractory metal material or ceramic material, is poured into the flexible mold. The slurry material is sintered to form each core. The first core (222) is used as an insert while making the second core (224) to create a final composite core (220).