Ceramic Core Removal Chemistry for Turbine Blade Surface Protection
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Solution Overview
Problem
Current methods for removing silica castings from nickel super alloy airfoils in gas turbine engines are time-consuming and can etch or mar the airfoil surfaces.
Innovation Solution
A solution comprising a strong base (potassium hydroxide, KOH) and a corrosion inhibitor (such as sodium tartrate) is used to dissolve ceramic materials, with optional addition of a solubility enhancer like Ethylenediaminetetraacetic acid (EDTA), applied at elevated temperatures and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current methods are used to remove silica castings from nickel super alloy airfoils, then the ceramic material is removed, but the process is time-consuming and may etch or mar the airfoil surfaces
Solution Approach 1:
The patent changes the chemical parameters of the removal solution by using a buffered aqueous solution with specific pH control (maintained between 2-7) and specific compositional ratios. This buffered solution removes ceramic material at an acceptable rate while preventing surface etching and marring of the airfoil, resolving the contradiction between removal speed and surface protection
Solution Approach 2:
The buffered aqueous solution acts as an intermediary medium that selectively removes ceramic material without directly attacking the metal airfoil surface. The buffering agents in the solution mediate the chemical reaction to achieve selective removal while protecting the underlying metal from harmful effects
2Productivity
If strong bases are used to dissolve ceramic materials, then the dissolution rate increases, but the airfoil surfaces may be damaged through etching or oxide formation
Solution Approach 1:
The patent modifies the parameters of the strong base solution by buffering it to maintain pH between 2-7 and controlling the concentration and composition of the solution. This buffered approach enables rapid dissolution of ceramic materials while preventing damage to the airfoil surface, thus resolving the contradiction between dissolution rate and surface integrity
Solution Approach 2:
The patent converts the potentially harmful strong base into a beneficial buffered solution. The strong base provides rapid dissolution capability, while the buffering agents convert the harmful uncontrolled pH into a controlled, protective environment that prevents surface damage while maintaining high dissolution rates
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
This method significantly reduces the time required to dissolve ceramic materials while preventing damage to the airfoil surfaces, achieving nearly threefold increase in etching attack depth without surface attack or oxide formation.
Implementation Method 1
a strong base and a corrosion inhibitor... The strong base is KOH... dissolve ceramic materials
Implementation Method 2
a corrosion inhibitor... preventing damage to the airfoil surfaces, achieving nearly threefold increase in etching attack depth without surface attack or oxide formation
Implementation Method 3
heating the vessel to an elevated temperature... holding the vessel at the elevated temperature
Implementation Method 4
increasing the pressure within the vessel to above atmospheric pressure... holding the vessel at the elevated temperature and above atmospheric pressure
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
A solution is provided comprising a strong base, a corrosion inhibitor, wherein the strong base is an alkali metal hydroxide, wherein the corrosion inhibitor is at least one of an organic acid having a-COOH functional group or an alkali metal salt one of an organic acid having a-COOH functional groups.