Rare Earth Silicate Environmental Barrier Coating
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current environmental barrier coatings for silicon carbide-based composites, such as those used in jet engine combustion chambers, face degradation in aqueous environments and high temperatures, with existing coatings like silica, mullite, and barium strontium aluminosilicate showing limited resistance to humid air, necessitating the development of more effective protective coatings.
Innovation Solution
A feed powder composed of highly circular, spherical silicate particles of specific elements like Zr, Y, and Er, with a narrow particle size distribution and high relative density, is used for plasma spraying to form a dense and homogeneous environmental barrier coating, which exhibits improved resistance to hot and humid conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional environmental barrier coatings (silica, mullite, BSAS) are applied to protect silicon carbide-based composites, then protection against oxidation is improved, but resistance to humid air and water vapor degradation remains insufficient
Solution Approach 1:
The patent applies composite materials by combining multiple silicate phases (monosilicates and disilicates of rare earth metals) with specific dopants to create a multi-phase coating system. This composite structure provides both oxidation resistance from the silicate matrix and enhanced moisture resistance from the specific phase composition and dopant elements, resolving the contradiction between oxidation protection and humid air resistance.
Solution Approach 2:
The patent changes the chemical composition parameters by specifying precise ratios of monosilicates to disilicates (70-95 wt% monosilicate, 5-30 wt% disilicate) and incorporating specific dopants (0.1-5 wt%). These parameter changes optimize the coating's resistance to both oxidation and humid air degradation, transforming the performance characteristics beyond conventional single-phase coatings.
2Reliability
If silica-based coatings are used to protect composites in oxidizing environments, then oxidation resistance is improved, but volatilization occurs under extreme conditions
Solution Approach 1:
The patent creates a composite coating system combining monosilicates and disilicates with specific dopants. This composite structure reduces silica volatilization by creating a more stable multi-phase system where the dopants and disilicate phases suppress vapor pressure and enhance thermal stability, while maintaining oxidation resistance through the silicate matrix.
Solution Approach 2:
The patent incorporates dopants in small quantities (0.1-5 wt%) that act as stabilizing agents to prevent volatilization. These minor additives significantly extend the service life and stability of the coating under extreme conditions without compromising the primary oxidation protection function.
3Ease of manufacture
If feed powder with wide particle size distribution is used for plasma spraying, then manufacturing simplicity is maintained, but coating homogeneity and density are reduced
Solution Approach 1:
The patent specifies precise particle size distribution parameters (D10: 3-10 μm, D50: 10-20 μm, D90: 20-40 μm) to optimize both sprayability and coating quality. This controlled parameter range ensures homogeneous coating deposition and high density while maintaining compatibility with standard plasma spraying equipment and processes.
Solution Approach 2:
The patent requires feed powder particles to have high sphericity (circularity ≥ 0.85). This spherical shape improves flow characteristics and plasma spray deposition uniformity, enabling homogeneous coating formation with consistent density while working effectively with conventional plasma spraying manufacturing processes.
4Use of energy by moving object
If feed powder with low relative density is used, then particle fusion during spraying is improved, but coating porosity increases reducing protection efficacy
Solution Approach 1:
The patent specifies a relative density range of 90-98% for the feed powder particles. This optimized density parameter ensures sufficient particle fusion during plasma spraying to create dense, low-porosity coatings while maintaining adequate energy absorption and melting characteristics for effective coating formation.
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 resulting environmental barrier coating demonstrates enhanced resistance to humid air and high temperatures, maintaining integrity in environments exceeding 1200°C, with a high degree of purity and low porosity, facilitating efficient plasma spraying and protecting ceramic-matrix composite materials.
Implementation Method 1
plasma spraying of an underlayer of yttrium silicate using a Y2Si2O7 powder, then deposition of an outer layer of mullite and of yttrium silicate
Data Source
AI summary
A powder formed of fused particles. More than 95% by number of the feed particles exhibiting a circularity of greater than or equal to 0.85. The powder contains more than 88% of a silicate of one or more elements chosen from Zr, Hf, Y, Ce, Sc, In, La, Gd, Nd, Sm, Dy, Er, Yb, Eu, Pr, Ho and Ta, less than 10% of a dopant, as percentage by weight based on the oxides. The powder has a median particle size D50 of less than 15 μm, a 90 percentile particle size, D90, of less than 30 μm, and a size dispersion index (D90-D10)/D10 of less than 2. The powder has a relative density of greater than 90%. The Dn percentiles of the powder are the particle sizes corresponding to the percentages, by number, of n %, on the cumulative distribution curve of the size of the particles of the powder. The particle sizes are classified in increasing order.