Multi-Constituent Environmental Barrier Coating With Self-Healing
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Solution Overview
Problem
Environmental barrier coatings (EBCs) in turbines and engine components suffer from microcracks that act as pathways for oxidant flux, leading to degradation of ceramic matrix composites (CMCs) due to the presence of microcracks and potential delamination.
Innovation Solution
A multi-component bond coat layer comprising an oxide matrix with dispersed oxidant gettering, crystalline, and self-healing amorphous phases, which form silicon oxide upon reaction with oxidants, allowing the amorphous phase to soften and flow into cracks at predetermined temperatures, thereby reducing oxidant flux and enhancing durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bond coat layer is used to limit oxidant flux to CMC, then the durability of EBC is improved, but microcracks develop in the bond coat that act as pathways for oxidants and as flaws for delamination growth
Solution Approach 1:
The patent changes the physical-chemical parameters of the bond coat by incorporating a glass phase with specific composition (SiO2, Al2O3, CaO, MgO) and controlling its viscosity characteristics. The glass phase undergoes viscosity reduction at service temperatures, enabling it to flow and seal microcracks dynamically, thus adapting the coating's protective properties to operational conditions.
Solution Approach 2:
The bond coat is designed as a composite material system comprising multiple phases: crystalline phases (mullite, zircon, hafnon), amorphous glass phase, and metal intermetallics. This composite structure combines the crack-resistance of crystalline phases with the self-healing capability of the glass phase, creating a synergistic effect that addresses both durability and microcrack prevention.
2Object-affected harmful factors
If the bond coat is designed to limit oxidant flux, then protection of CMC is achieved, but microcracks form that serve as pathways for oxidants and initiation sites for delamination
Solution Approach 1:
The glass phase in the bond coat performs self-service by automatically sealing microcracks through viscous flow at service temperatures. This self-healing mechanism occurs without external intervention, where the glass material flows into crack openings and solidifies, maintaining coating integrity and continuing to protect the substrate from oxidant ingress.
Solution Approach 2:
The patent converts the harmful effect of microcrack formation into a beneficial self-healing process. Instead of viewing microcracks solely as defects, the design allows them to trigger the glass phase's viscous flow, which then seals the cracks. The microcracks become the very mechanism that activates the repair process, transforming a failure mode into a protective mechanism.
3Reliability
If a multi-component bond coat is used to improve self-healing capability, then durability is enhanced, but the coating system complexity increases
Solution Approach 1:
The glass phase serves multiple functions simultaneously: it acts as a binder holding the coating together, provides self-healing by sealing microcracks through viscous flow, and contributes to oxidant resistance. This multi-functionality reduces the need for separate components for each protective mechanism, simplifying the overall system despite the multi-component nature of the bond coat.
Solution Approach 2:
The patent merges several protective functions into a single integrated bond coat layer rather than using separate layers for oxidation resistance, crack resistance, and self-healing. The multi-phase composite structure combines crystalline phases for mechanical strength, metal intermetallics for oxidation resistance, and glass phase for self-healing, all within one unified coating 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 self-healing mechanism improves the durability of EBCs by minimizing oxidant ingress through microcracks, thus reducing the degradation rate of underlying substrates like silicon-containing materials.
Implementation Method 1
an amorphous oxide phase, which is a self-healing phase having the ability to soften or melt and flow into cracks formed in the oxide matrix at predetermined temperatures
Implementation Method 2
the amorphous oxide phase comprises an alkaline earth alumino-silicate glass... viscosity between 200 and 20,000 Pa•s at 1300 °C
Implementation Method 3
an oxidant gettering phase that forms silicon oxide, i.e., that forms SiO2 upon reaction with oxidants
Implementation Method 4
an oxidant gettering phase that forms silicon oxide, i.e., that forms SiO2 upon reaction with oxidants
Implementation Method 5
having the ability to soften or melt and flow into cracks formed in the oxide matrix at predetermined temperatures that are below the melting temperature of the oxide matrix
Implementation Method 6
an amorphous oxide phase, which is a self-healing phase
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
Environmental barrier coatings or coating systems (100) that contain a bond coat (120), the bond coat (120) containing an oxide matrix (128), and dispersed throughout the oxide matrix (128) an oxidant gettering phase (122), a SiO2 based phase, that may be amorphous or crystalline, a crystalline phase (124), and an amorphous oxide phase (126), which is a self-healing phase (128) having the ability to soften or melt and flow into cracks formed in the oxide matrix (128) at predetermined temperatures that are below the melting temperature of the oxide matrix (128), where the amorphous oxide phase (126) contains an alkaline earth alumino-silicate, and the crystalline phase (124) contains Al6Si2O13, ZrSiO4, HfSiO4, Ca2ZrSi4O12, Ca2HfSi4O12, CaAl2Si2O8, CaSiO3, Al2TiO5 ,Mg2Al4Si5O18, BaAl2Si2O8 , BaZrSi3O9, Y2Si2O7, Yb2Si2O7, and/or Al2O3, and methods for protecting ceramic matrix composite materials (130).