CMAS Resistant Thermal Barrier Coating with Activated Reactive Layer
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Solution Overview
Problem
The durability and maximum temperature capability of thermal barrier coatings in gas turbine engines are limited by calcium-alumino-silicate (CMAS) deposits, which melt and penetrate the coating, causing spallation and reducing component durability.
Innovation Solution
A CMAS-resistant reactive layer with known reaction kinetics is deposited over the thermal barrier coating, formed from a powder mixture containing SiO2, CaO, MgO, and Al2O3, and activated through heat treatment before service, to prevent CMAS penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an extra layer is deposited over the thermal barrier coating, then the coating structure is enhanced, but the CMAS resistance is insufficient because the layer is not activated prior to service
Solution Approach 1:
The reactive layer is activated through heat treatment before the component enters service, so that when CMAS is encountered, the layer is already prepared to react and resist penetration. This preliminary activation ensures reliable CMAS resistance from the start of service.
Solution Approach 2:
The reactive layer's properties are changed through heat treatment at specific temperatures (1000-1200°C) to activate it. This parameter change transforms the layer from an inactive state to an active state capable of resisting CMAS penetration effectively.
2Reliability
If the reactive layer is activated prior to service, then the CMAS resistance is improved, but the manufacturing process complexity increases
Solution Approach 1:
The activation heat treatment is combined with existing service preparation processes or performed during initial component processing. By integrating the activation step into the overall manufacturing or preparation workflow, the additional process complexity is minimized while achieving reliable CMAS resistance.
3Reliability
If the reactive layer composition is optimized for known CMAS reaction kinetics, then the CMAS resistance is enhanced, but the adaptability to different CMAS compositions is reduced
Solution Approach 1:
The reactive layer is designed with specific local compositions optimized for the most likely CMAS compositions encountered in service. By tailoring the layer's chemical composition to match expected CMAS types, the coating achieves superior resistance for those specific conditions while maintaining adequate performance for other CMAS variations.
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 activated reactive layer significantly increases the durability of the thermal barrier coating by preventing CMAS penetration and spallation, enhancing the turbine engine component's performance and reducing maintenance costs.
Implementation Method 1
activating the reactive layer prior to the component being placed in service, wherein said activating step comprises subjecting said reactive layer to a heat treatment at a temperature in the range of 1149°C to 1204°C (2100°F to 2200°F)
Implementation Method 2
a thermal barrier coating deposited on the substrate
Implementation Method 3
These deposits melt and wet the material, typically yttria-stabilized zirconia, used as the thermal barrier coating, causing it to be drawn by capillarity into all of the open void space
Data Source
Figure 1~4
AI summary
A process for forming a coating system on a turbine engine component comprises the steps of providing a substrate, depositing a thermal barrier coating on the substrate, depositing a reactive with known CMAS reaction kinetics on the thermal barrier coating, and activating the reactive layer prior to the component being placed in service. As a result of the foregoing process, there is provided a turbine engine component which has a substrate, a thermal barrier coating deposited on the substrate, a reactive layer deposited on the thermal barrier coating, which reactive layer has known CMAS reaction kinetics and is activated prior to the turbine engine component entering into service.