Sacrificial Layer Protects CMC Coating During Laser Drilling
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Solution Overview
Problem
Existing methods for forming holes in ceramic matrix composite (CMC) components with environmental barrier coatings (EBCs) face issues due to silicon liquid metal splatter deposition during laser drilling, which damages the EBC coating.
Innovation Solution
A sacrificial layer of rare earth oxide particles is applied over the EBC, allowing spatter from drilling to deposit on it, and then the layer is removed along with the spatter, protecting the underlying coating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If laser drilling is used to form holes in CMC components with EBC coating, then film cooling holes can be formed for high-temperature operation, but silicon liquid metal splatter deposits on the EBC surface causing coating damage
Solution Approach 1:
A sacrificial layer is applied to the EBC coating surface before laser drilling. This preliminary action prepares the surface to capture silicon splatter that will be generated during subsequent drilling operations, preventing direct contact between the splatter and the EBC coating.
Solution Approach 2:
The sacrificial layer acts as an intermediary between the laser drilling process and the EBC coating. It intercepts the silicon liquid metal splatter, absorbing the harmful effect before it can reach and damage the underlying EBC coating.
2Reliability
If a sacrificial layer is applied to protect the EBC coating during drilling, then coating integrity is maintained, but an additional manufacturing step is required
Solution Approach 1:
The sacrificial layer is designed as a temporary, disposable protective layer that is applied before drilling and then removed after drilling. This disposable approach protects the valuable EBC coating during the drilling process while accepting that the sacrificial layer itself will be discarded.
Solution Approach 2:
After the sacrificial layer has served its protective function during drilling, it is removed from the component surface along with any captured splatter. This discarding step recovers the clean EBC coating surface while eliminating the protective layer that has completed its mission.
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 method effectively prevents damage to the EBC coating by containing and removing the splatter, ensuring the integrity of the CMC components in high-temperature environments.
Implementation Method 1
drilling a hole into the coated component such that any spatter formed during drilling deposits onto the sacrificial layer
Implementation Method 2
film holes may be formed in the CMC component via laser drilling
Data Source
AI summary
Methods for forming a hole in a coated component are provided. The method may include forming a sacrificial layer over a ceramic barrier coating of a substrate, drilling a hole into the coated component such that any spatter formed during drilling deposits onto the sacrificial layer, and removing the sacrificial layer along with the spatter deposited thereon. The sacrificial layer may include a rare earth oxide (e.g., rare earth oxide particles). Intermediate ceramic matrix composite (CMC) component are also provided. The intermediate CMC may include a CMC body, an environmental barrier coating on the bond coating, and a sacrificial layer on the environmental barrier coating, with the sacrificial layer including particles of a rare earth oxide dispersed in a polymeric matrix.