Dense Environmental Barrier Coatings via Molten Silicate Glass Infiltration
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Solution Overview
Problem
Ceramic and ceramic matrix composite substrates used in high-temperature mechanical systems, such as gas-turbine engines, are vulnerable to chemical attack by water vapor and excessive oxidation, leading to damage and compromised mechanical integrity due to porosity in environmental barrier coatings (EBCs), which allow gaseous species like oxygen to penetrate.
Innovation Solution
Infiltrating the EBC layer with molten silicate glass to reduce porosity and increase density, thereby preventing the transport of oxygen and other gaseous species, and enhancing the mechanical bond between the EBC and bond layers by forming a silicate glass layer on the EBC surface and melting it to fill pores.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an EBC layer is formed on the substrate to protect against chemical attack, then the substrate is protected from environmental damage, but the EBC layer exhibits porosity that allows gaseous species like oxygen to penetrate
Solution Approach 1:
The patent applies porous EBC materials (such as hollow sphere particles) to provide protection against chemical attack while managing porosity. The porous structure is intentionally designed to allow controlled interaction with the environment while maintaining protective functions.
Solution Approach 2:
The patent uses composite EBC layers combining different materials (e.g., hollow spheres, glass particles, ceramic matrices) to achieve both protection against chemical attack and reduced penetration of gaseous species. The composite structure allows optimization of both protective and barrier properties.
2Stability of the object's composition
If the EBC layer has porosity to accommodate thermal expansion and stress, then the coating remains intact under thermal cycling, but the porosity allows excessive oxidation of the substrate
Solution Approach 1:
The patent applies different local properties to different regions of the EBC system. The outer EBC layer maintains porosity for stress accommodation, while the inner EBC layer or bond coat is densified to prevent oxidation. This local differentiation allows simultaneous achievement of thermal stability and oxidation protection.
Solution Approach 2:
The EBC system is segmented into multiple functional layers with distinct porosity characteristics. The outer layer provides thermal stress relief through porosity, while inner layers provide oxidation barrier functions, dividing the protective function into specialized zones.
3Object-affected harmful factors
If a dense EBC layer is formed to prevent oxygen penetration, then oxidation is reduced, but the coating becomes more susceptible to thermal stress and cracking
Solution Approach 1:
Different density properties are assigned to different layers: the inner EBC layer is densified to block oxygen, while the outer EBC layer maintains porosity to accommodate thermal expansion and reduce stress concentration, preventing cracking.
Solution Approach 2:
The EBC system uses composite structures where dense ceramic phases provide oxidation barrier properties while porous phases or glass matrices provide stress relief capabilities, combining contradictory properties in a unified protective system.
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 reduced porosity of the EBC layer effectively prevents excessive oxidation and maintains the mechanical integrity of the substrate, enhancing the bond strength and chemical stability, thus protecting the substrate from environmental damage.
Implementation Method 1
melting the silicate glass on the surface of the EBC layer to infiltrate the EBC layer with the molten silicate glass to decrease the porosity
Implementation Method 2
melting the silicate glass on the surface of the EBC layer
Data Source
AI summary
In some examples, method including forming an EBC layer on a substrate, wherein the EBC layer exhibits an initial porosity; forming a layer of silicate glass on a surface of the EBC layer; and melting the silicate glass on the surface of the EBC layer to infiltrate the EBC layer with the molten silicate glass to decrease the porosity of the EBC layer from the initial porosity to a final porosity.