Ceramic Metallic Core Attachment Slurry
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Solution Overview
Problem
In investment casting, the binders of ceramic adhesives often react adversely with refractory metal cores, necessitating a more reliable method for securing ceramic and metallic core assemblies, particularly in aerospace applications like gas turbine engine parts.
Innovation Solution
A specialized slurry comprising zircon and aqueous colloidal silica in a specific weight ratio, along with a surfactant and polydimethyl siloxanes, is used to attach metallic and ceramic casting cores, which are vibrated to ensure infiltration and hardening, facilitating the formation of stable core assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If ceramic adhesive binders are used to secure refractory metal cores to ceramic cores, then the cores can be attached together, but the binders react adversely with the refractory metal cores causing mechanical failure
Solution Approach 1:
A nickel-based intermediate coating is applied to the refractory metal core surfaces before assembly. This intermediate layer acts as a barrier between the ceramic adhesive binder and the refractory metal core, preventing adverse chemical reactions while maintaining strong attachment. The nickel coating is specifically chosen for its chemical compatibility with both the ceramic binder and refractory metal, resolving the contradiction between attachment strength and chemical compatibility.
2Manufacturing precision
If vibration is applied during slurry introduction, then infiltration between cores is improved, but the process complexity increases
Solution Approach 1:
A vibration mechanism is integrated into the assembly press to apply ultrasonic or high-frequency mechanical vibrations during slurry introduction. This vibration agitates the slurry, improving its infiltration into the interface between ceramic and metallic cores, eliminating air pockets, and ensuring complete coverage. The vibration is automatically controlled and synchronized with the pressing operation, achieving precise infiltration without significantly increasing overall process complexity.
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 slurry effectively secures core assemblies, preventing adverse reactions and ensuring mechanical integrity during the casting process, while maintaining thermal compatibility and reducing the risk of mechanical failure due to drying shrinkage.
Implementation Method 1
The metallic casting core and ceramic casting core are vibrated during the introducing
Implementation Method 2
The slurry may be heated to harden
Data Source
Figure 1
Figure 2~4
Figure 3
AI summary
A slurry is used to secure a metallic casting core (212) to a ceramic casting core (210). The slurry may be introduced between the metallic and ceramic casting cores (212,210) and hardened. The slurry may comprise zircon and aqueous colloidal silica. Preferably the cores (210,212) are vibrated during the introduction, e.g. by a shaker table (202) which receives a fixture (204) for the cores (210,212).