CMC Coating with Integrated Thermocouple
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring temperature between a ceramic matrix composite (CMC) substrate and a barrier layer in aeronautical turbines are complex and prone to interactions that degrade the thermocouple and coating, requiring encapsulation in a different material to avoid compatibility issues with silicon-based substrates.
Innovation Solution
A multilayer stack comprising a silicon tie layer, a rare earth disilicate or silica insulation layer, and a rare earth disilicate barrier layer with a thermocouple inserted between the insulation and barrier layers, avoiding direct contact with the silicon tie layer and simplifying production by eliminating the need for encapsulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermocouple is positioned close to the interface between the barrier layer and substrate, then temperature measurement precision is improved, but the thermocouple interacts with the silicon-based substrate and barrier layer causing degradation
Solution Approach 1:
An insulation layer made of electrically insulating ceramic material is introduced between the thermocouple and the silicon-based barrier layer. This intermediary layer prevents harmful chemical interactions and diffusion between the thermocouple metals (particularly platinum) and the silicon substrate while maintaining close proximity for accurate temperature measurement at the interface.
2Reliability
If the thermocouple is encapsulated in a different material to avoid interactions, then thermocouple lifespan is improved, but the forming process complexity increases
Solution Approach 1:
The insulation layer is integrated into the existing multilayer coating structure, combining the protective function with the thermal barrier coating system. The layer is formed using the same or compatible deposition processes (such as plasma spray or CVD) already used for the barrier layers, eliminating the need for separate encapsulation steps and reducing overall process complexity.
3Reliability
If an insulation layer is introduced to prevent interactions, then thermocouple lifespan is improved, but the insulation layer thickness must be precisely controlled to maintain measurement accuracy
Solution Approach 1:
The thickness of the insulation layer is optimized to be sufficiently thin (controlling this parameter) to maintain thermal conductivity and measurement accuracy, while being thick enough to provide electrical insulation and prevent chemical interactions. Standard deposition process controls enable precise thickness management within the required range.
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 configuration allows for precise temperature measurement between the substrate and barrier layer while increasing the lifespan of the thermocouple and coating, and simplifies the production process by avoiding encapsulation and ensuring electrical continuity.
Implementation Method 1
at least one thermocouple inserted between the insulation layer and the barrier layer
Implementation Method 2
the metals or alloys generally used for thermocouples measuring temperatures of interest for aeronautical turbomachine parts made of coated ceramic matrix composite material are not compatible with the presence of silicon, because they generally comprise platinum which can diffuse into the silicon and harm its good properties
Data Source
AI summary
A part includes a substrate made of ceramic matrix composite material, the substrate being coated with a multilayer stack including at least, and in this order, starting from the substrate a tie layer including silicon; an insulation layer including a rare earth disilicate or silica; a barrier layer including a rare earth disilicate; the part further including at least one thermocouple inserted between the insulation layer and the barrier layer.