Textured SiC Barrier Layer for CMC Oxide Control
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Solution Overview
Problem
Ceramic matrix composite (CMC) materials used in high-temperature mechanical systems, such as gas turbine engines, react with environmental elements like water vapor, leading to damage and reduced mechanical properties due to thermally grown oxide (TGO) formation, which compromises the component's lifespan.
Innovation Solution
A coating system is developed with a textured silicon carbide barrier layer and an overlying environmental barrier coating, where the barrier layer is textured using laser ablation to improve adhesion and prevent impurity migration, maintaining TGO in an amorphous phase and reducing crystallization-induced cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a smooth barrier layer is used, then the manufacturing process is simpler, but the adhesion between layers is insufficient leading to TGO crystallization and cracking
Solution Approach 1:
The barrier layer surface is textured before applying the overlying layer, creating a predetermined pattern of cells that will enhance adhesion. This preliminary surface modification ensures that when the overlying layer is applied, it bonds strongly to the textured surface, preventing TGO crystallization and cracking at the interface.
Solution Approach 2:
The barrier layer is given a porous or cellular structure with a pattern of cells having specific geometries. This cellular structure increases the surface area and creates mechanical interlocking with the overlying layer, significantly improving interfacial adhesion strength while maintaining the protective barrier function.
2Reliability
If a textured barrier layer is created, then adhesion is improved and TGO crystallization is reduced, but the manufacturing process becomes more complex
Solution Approach 1:
Traditional mechanical texturing methods are replaced with laser-based surface modification. The laser process can create the desired cellular pattern directly on the barrier layer surface without complex mechanical tooling, reducing manufacturing complexity while achieving the required surface texture for improved adhesion and reliability.
Solution Approach 2:
The manufacturing process controls the cellular structure parameters (cell size, shape, depth, and distribution) through process variables such as laser parameters or deposition conditions. By adjusting these parameters, the desired surface texture is achieved systematically, making the complex texturing process controllable and repeatable.
3Duration of action of stationary object
If the barrier layer prevents impurity migration, then TGO formation is reduced extending component life, but the surface texture requires additional processing steps
Solution Approach 1:
The barrier layer formation and surface texturing operations are combined into a single integrated process step. The cellular structure is created during the barrier layer deposition or immediately afterward in the same processing sequence, eliminating separate texturing steps and reducing overall manufacturing cycle time while maintaining the impurity migration barrier function.
Solution Approach 2:
The textured barrier layer structure serves multiple functions simultaneously: it acts as an impurity migration barrier, provides enhanced adhesion for the overlying layer, and maintains protective coating integrity. This multi-functionality reduces the need for additional separate processing steps, improving productivity while extending component life.
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 textured barrier layer enhances adhesion and reduces TGO crystallization, thereby maintaining interfacial strength and extending the component's usable life by preventing impurity migration and oxidation, while minimizing heat-induced damage and material degradation.
Implementation Method 1
The barrier layer may reduce migration of material from the substrate into the one or more overlying layers to reduce formation of thermally grown oxide (TGO) phases
Implementation Method 2
the barrier layer is textured using laser ablation to improve adhesion and prevent impurity migration
Data Source
AI summary
In some examples, the disclosure describes an article and a method of making the same that includes a substrate defining an outer surface, a barrier layer on the outer surface of the substrate, the barrier layer defining a textured surface having a plurality of cells, each cell having a geometry and a depth, and an overlying layer formed on the textured surface of the barrier layer. The barrier layer may be configured to reduce migration of material from the substrate to the overlaying layer to reduce or prevent formation of cristobalite phase thermally grown oxide.