Environmental Barrier Coating Densification via Sintering Aids
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Solution Overview
Problem
Current environmental barrier coatings for high temperature ceramic components in gas turbine engines face challenges such as porosity and degradation in high temperature steam environments, leading to oxidation and volatilization issues, which existing coating processes like plasma spray and vapor deposition fail to adequately address.
Innovation Solution
A method involving the use of sintering aids to create a densified environmental barrier coating comprising a transition layer with 0-30% porosity and an outer layer with 0-15% porosity, using a slurry deposition process that includes mullite, BSAS, or their mixture, and rare earth oxides, to form a hermetic seal that protects against high temperature steam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plasma spray or vapor deposition processes are used to apply EBCs, then the coating can be applied to ceramic components, but the resulting coating exhibits porosity and degradation in high temperature steam environments
Solution Approach 1:
The patent applies a slurry composition with specific particle size distribution (D10=0.5-2.0 microns, D50=2.0-5.0 microns, D90=5.0-10.0 microns) and controlled water content (30-70 wt%) to achieve optimal packing density. The slurry is applied at controlled thickness (5-50 microns) and dried at specific temperature ranges (100-200°C for 1-24 hours), transforming the coating from porous to dense structure that resists steam penetration
Solution Approach 2:
The patent uses a composite slurry system combining ceramic particles (mullite, BSAS, or their混合物) with organic binders and solvents. This composite approach allows the slurry to form a dense, interconnected matrix after drying that eliminates porosity while maintaining the protective function against steam and oxidation
2Reliability
If conventional coating processes are used, then EBC can be applied to protect ceramic components, but the coating requires high sintering temperatures that increase manufacturing costs
Solution Approach 1:
The patent reduces sintering temperature by optimizing the slurry composition with fine particle size distribution and appropriate organic additives that facilitate densification at lower temperatures. The controlled particle packing and organic binder system enable effective sintering at reduced temperatures while maintaining coating integrity and protective function
Solution Approach 2:
The organic binders and solvents in the slurry act as intermediaries that facilitate particle bonding and densification during drying and low-temperature sintering. These organic components enable the ceramic particles to form a dense structure at lower temperatures than conventional direct sintering would require
3Reliability
If conventional coating processes are used, then EBC can be applied to ceramic components, but the coating exhibits non-uniform thickness that affects performance
Solution Approach 1:
The patent controls slurry viscosity through water content (30-70 wt%) and particle size distribution to achieve uniform flow and deposition characteristics. This allows the slurry to form a consistent thickness (5-50 microns) across the ceramic component surface, ensuring uniform protective performance
Solution Approach 2:
The patent creates a homogeneous slurry composition with well-distributed ceramic particles and organic binders, ensuring uniform properties throughout the coating. This homogeneous mixture, achieved through controlled particle size distribution and mixing, produces consistent coating thickness and performance across the entire component surface
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 results in a highly dense coating that effectively seals against high temperature steam, preventing degradation and oxidation, while allowing for lower sintering temperatures, reducing costs, and providing a more uniform thickness and improved mechanical properties compared to conventional techniques.
Implementation Method 1
infiltrating a sol-gel solution into the applied transition layer slurry
Implementation Method 2
sintering the component to produce the environmental barrier coating having at least a transition layer and an outer layer wherein the transition layer comprises a porosity of from 0% to about 30% by volume of the transition layer, and the outer layer comprises a porosity of from 0% to about 15% by volume of the outer layer
Data Source
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AI summary
Methods for making an environmental barrier coating (12) using a sintering aid comprising combining at least water, and a primary transition material comprising mullite, BSAS, or a mullite/BSAS mixture to produce a transition layer slurry; applying the transition layer slurry to a ceramic component (10); combining at least water, and a primary outer material comprising BSAS to produce an outer layer slurry; applying the outer layer slurry to the component having the applied transition layer slurry; and sintering the component to produce the environmental barrier coating having at least a transition layer (16) and an outer layer (18) wherein after applying at least one of the transition layer slurry or the outer layer slurry, the component is dried and the at least one layer is infiltrated with a sol-gel solution, and wherein the transition layer comprises a porosity of from 0% to about 30% by volume of the transition layer, and the outer layer comprises a porosity of from 0% to about 15% by volume of the outer layer.