CMC Coating Repair Using Plasma Torch Slurry Application
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Solution Overview
Problem
Ceramic matrix composite (CMC) substrates used in gas turbine engines face challenges in repairing coatings damaged by penetrations or CMAS infiltration, which can lead to thermal and mechanical mismatch issues.
Innovation Solution
A method involving the application of a slurry repair material followed by heating with a plasma torch is used to repair damaged layers on CMC substrates. This method can include plasma spray repair and the use of materials like hafnium dioxide (HfO2) and silicon oxycarbide, with optional depthwise gradations of calcium magnesium alumino-silicate (CMAS).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional repair methods are used for damaged coating layers on CMC substrates, then the repair process is simple, but thermal and mechanical mismatch issues occur leading to poor repair durability
Solution Approach 1:
The patent applies parameter changes by carefully controlling the plasma torch processing parameters (temperature, exposure time, gas composition) to activate the repair material and promote proper bonding. This resolves the contradiction by optimizing physical-chemical parameters to achieve durable repairs without requiring overly complex multi-step processes
Solution Approach 2:
The patent uses composite repair materials that combine multiple functional components (e.g., reactive powders, binders, and CMC-compatible materials) in a single repair application. This creates thermally and mechanically matched repairs that durably bond to the substrate while maintaining a relatively simple single-step repair process
2Stability of the object's composition
If the coating layers are fully restored to original composition, then thermal and mechanical mismatch is eliminated, but the repair process becomes more complex and time-consuming
Solution Approach 1:
The patent applies partial action by restoring only the essential functional composition of the coating layers rather than attempting to perfectly replicate every original parameter. The repair material is applied to achieve sufficient thermal and mechanical stability without requiring complete compositional restoration, thereby reducing repair time while maintaining adequate performance
3Strength
If reactive powders are used to form a bonding layer, then strong adhesion is achieved, but the process requires additional steps and controls
Solution Approach 1:
The patent merges multiple functions into a single integrated step: the reactive powders serve both as bonding agents and as part of the final coating composition, while the plasma torch simultaneously heats the substrate, activates the reactive powders, and facilitates bonding. This combination approach achieves strong adhesion without requiring separate sequential steps for each function
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 method effectively repairs damaged coatings on CMC substrates by restoring the original layer structure and composition, addressing thermal and mechanical mismatch issues and ensuring the durability and performance of the engine components.
Implementation Method 1
heating the repair material with a plasma torch
Implementation Method 2
plasma spray repair
Data Source
AI summary
In a method for repairing a coated article, the article has: a ceramic matrix composite (CMC) substrate; and a coating system having a plurality of layers. A damage site at least partially penetrates at least one of the layers. The method includes: applying a slurry of a repair material to the damage site for repairing a first of the penetrated layers; and after the applying, heating the repair material with a plasma torch.