Thermal Barrier Coating CMAS Blocking via Selective Infiltration
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Solution Overview
Problem
Gas turbine engine components with thermal barrier coatings (TBCs) are prone to premature spallation due to infiltration by molten environmental contaminants like CMAS, which causes strain energy leading to coating failure, and existing testing methods involve high temperatures that induce spallation during thermal processing.
Innovation Solution
A process involving the selective infiltration of a blocking material, such as a CMAS compound within a polymer resin carrier, into the TBC to form a multi-phase pre-reacted surficial region, using techniques like Suspension Plasma Spray, to enhance strain tolerance and prevent spallation, combined with a bond coat and yttria-stabilized zirconia top coat.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal processing at temperatures greater than 2150°F (1177°C) is used to infiltrate environmental contaminants into the TBC for testing, then the actual contaminant infiltration can be achieved, but the TBC experiences spallation including complete separation from the metallic substrate due to thermal expansion mismatch and low ceramic toughness
Solution Approach 1:
A blocking material is applied to the TBC surface before thermal processing to preemptively prevent contaminant infiltration and subsequent spallation during high-temperature testing
Solution Approach 2:
A blocking material serves as an intermediary layer between the environmental contaminants and the TBC, preventing direct harmful interaction while allowing thermal processing to proceed
2Reliability
If the TBC is exposed to molten environmental contaminants like CMAS during service, then the contaminants penetrate the strain tolerant porosity of the TBC microstructure, but upon cooling the penetrated layer stiffens and induces strain energy leading to premature TBC spallation
Solution Approach 1:
The blocking material is applied in advance to counteract the harmful effect of contaminant infiltration before it can occur during service or testing
Solution Approach 2:
The blocking material converts the harmful infiltration process into a beneficial pre-sealing action, where the controlled application and thermal processing creates a protective state that prevents future damage
3Reliability
If rare earth zirconates are used to react with encroaching CMAS melt, then the depth and rate of infiltration is decreased and strain energy is reduced, but the formation of this reaction layer is not readily controllable in service due to extrinsic factors
Solution Approach 1:
The blocking material is applied and activated in advance under controlled conditions, eliminating the need for complex in-service control of reaction layer formation
Solution Approach 2:
The blocking material approach changes the process parameters from relying on uncontrolled in-service reactions to a controlled pre-application and thermal activation process
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 effectively mitigates damage from environmental contaminants, improves temperature capability, and allows for the evaluation of mechanical properties without inducing premature spallation, thereby extending the lifespan of TBCs on gas turbine engine components.
Implementation Method 1
selective infiltration of a blocking material, such as a CMAS compound within a polymer resin carrier, into the TBC to form a multi-phase pre-reacted surficial region
Implementation Method 2
using techniques like Suspension Plasma Spray
Implementation Method 3
The carrier is then removed to leave behind the blocking material
Data Source
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AI summary
A process for coating a component (42) including applying a thermal barrier coating material (48) to a bond coat (44) and selectively infiltrating a blocking material (50) into the thermal barrier coating material (48).