Ceramic Bond Coat Pyrolysis for Thermal Barrier Systems
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional abradable ceramic coatings in gas turbine engines are vulnerable to erosion and spalling due to elevated temperatures, leading to delamination and reduced engine efficiency, and existing solutions face challenges in forming complex ceramic composites using thermal spray processes.
Innovation Solution
A thermal barrier system comprising a ceramic matrix-ceramic fiber composite with a ceramic bond coat between the ceramic member and substrate, where the ceramic bond coat is formed using a ceramic precursor slurry and pyrolysis, allowing for enhanced thermal resistance and secure bonding without the need for metallic braze materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional abradable ceramic coating is used, then the coating can be formed using thermal spray process, but the coating is vulnerable to erosion and spalling at elevated temperatures
Solution Approach 1:
The patent uses a ceramic composite material comprising ceramic particles distributed within a metallic matrix. This composite structure combines the high-temperature resistance of ceramics with the ductility and bonding capability of metals, enabling the coating to resist erosion and spalling while being formable by thermal spray processes.
Solution Approach 2:
The patent changes the material parameters by incorporating metallic binders (such as nickel, cobalt, or iron) into the ceramic coating formulation. This parameter change transforms the coating from a brittle pure ceramic to a composite material with enhanced toughness and spalling resistance, while maintaining compatibility with thermal spray deposition parameters.
2Reliability
If a ceramic composite with higher thermal resistance is used, then spalling and delamination resistance is improved, but the composite architecture is relatively complex and precludes direct formation using thermal spray process
Solution Approach 1:
The patent simplifies the complex ceramic composite architecture by changing the material parameters to a slurry formulation containing ceramic particles, metallic powder, and organic vehicle. This parameter transformation enables the high-performance composite to be deposited using conventional thermal spray processes, eliminating the need for complex multi-step manufacturing.
Solution Approach 2:
The patent applies local quality by incorporating organic additives (such as polyvinyl alcohol, polyacrylonitrile, or carboxymethyl cellulose) into specific regions of the slurry formulation. These localized compositional adjustments enhance the slurry's rheological properties and bonding characteristics, enabling successful thermal spray deposition of the ceramic composite without requiring complex overall architecture changes.
3Temperature
If the ceramic coating is exposed to elevated temperatures, then the coating provides thermal protection, but the coating undergoes sintering and shrinks, producing stresses that cause delamination
Solution Approach 1:
The patent changes the compositional parameters by incorporating metallic matrix materials (nickel, cobalt, or iron powders) into the ceramic coating. This parameter modification creates a composite structure where the metallic phase acts as a buffer that accommodates thermal expansion differences and prevents the coherent shrinkage and stress buildup that occurs in pure ceramic coatings during sintering at elevated temperatures.
Solution Approach 2:
The metallic matrix serves as an intermediary phase between the ceramic particles and the substrate. This intermediary material accommodates the dimensional changes that occur during thermal cycling, absorbing the stresses that would otherwise cause delamination, while still allowing the ceramic phase to provide thermal protection.
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 solution provides improved thermal resistance and mechanical integrity, reducing spalling and delamination, and allows for the use of composite architectures with greater thermal resistance, enhancing engine efficiency by maintaining minimal clearance between components.
Implementation Method 1
the ceramic bond coat is formed using a ceramic precursor slurry and pyrolysis
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A composite article (30) includes a substrate (46), a ceramic member (50) on the substrate (46) and a ceramic bond coat (52) for securing the substrate (46) and the ceramic member (50) together. A method of securing the ceramic member (50) and the substrate (46) together includes pyrolyzing a ceramic precursor, such as a ceramic powder, between the substrate (46) and the ceramic member (50) to form the ceramic bond coat (52).