Multicomponent Hafnium-Doped Silicate Environmental Barrier Coatings
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Solution Overview
Problem
Current environmental barrier coating systems for Si-based ceramics and SiC/SiC ceramic matrix composites fail to maintain mechanical strength and stability at high temperatures, especially in turbine engine environments, due to degradation from impurities and rare earth dopant leaching, leading to insufficient temperature capabilities and durability.
Innovation Solution
A multicomponent, rare earth-based, hafnium-doped silicate environmental barrier coating system with multiphase compositions, including rare earth apatite phases and oxyapatite structures, is developed to enhance thermal, thermomechanical, and environmental stability, incorporating larger and smaller ionic radius rare earth elements and Zr/Hf dopants to improve phase stability and CMAS resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If single rare earth element silicates are used as EBC coating, then the coating can operate at high temperatures, but the rare earth dopants leach out due to impurities and reactions, causing melting and fast erosion in damaging environments
Solution Approach 1:
The patent uses composite materials by combining multiple rare earth elements (e.g., Y2SiO5 with Gd2SiO5 or Lu2SiO5) to create a multi-component EBC system. This composite approach prevents the leaching of individual rare earth dopants while maintaining high-temperature stability, as the multiple components work synergistically to resist corrosion and erosion in CMAS and sand environments.
Solution Approach 2:
The patent changes the compositional parameters of the EBC by incorporating multiple rare earth elements with different ionic radii and properties. This parameter change transforms the single-component system into a multi-component system with enhanced environmental stability and resistance to dopant leaching, while maintaining the required high-temperature operating capability.
2Object-affected harmful factors
If current EBC systems (BSAS, mullite, rare earth silicates) are used, then the coating provides environmental protection, but the mechanical strength degrades significantly in turbine engine harsh operating environments
Solution Approach 1:
The patent employs composite materials consisting of multiple rare earth silicate phases (e.g., Y2SiO5 combined with Gd2SiO5 or Lu2SiO5) to create an EBC system that simultaneously provides environmental protection and maintains mechanical strength. The composite structure prevents the degradation issues of single-component systems by distributing stress and resisting harmful environmental factors more effectively.
Solution Approach 2:
The patent applies local quality by creating a multi-component coating system where different rare earth silicate phases are distributed throughout the coating structure. Each component provides specific local properties that collectively enhance both environmental protection and mechanical strength, with the combination of phases providing synergistic effects against erosion and corrosion.
3Temperature
If rare earth mono-silicates and di-silicates are used as EBC, then the coating has high melting points, but the melting points are significantly reduced in the presence of minor impurities and reactions with coating layers
Solution Approach 1:
The patent uses composite materials by combining multiple rare earth silicates (e.g., Y2SiO5 with Gd2SiO5 or Lu2SiO5) to create a multi-component system where the high melting points are maintained. The presence of multiple stable phases prevents the formation of low-melting-point compounds that would otherwise form from impurities or reactions, thereby maintaining phase stability and composition integrity in harsh environments.
Data Source
AI summary
An advanced high temperature environmental barrier coating system is disclosed for protecting Si-based ceramics and SiC/SiC ceramic matrix composites (CMCs). This innovation provides a series of environmental barrier coating composition systems to achieve exceptional temperature capability, erosion and calcium-magnesium-aluminosilicate (CMAS) resistance and durability of the environmental barrier coated ceramic turbine engine hot-section components, in harsh turbine engine environments. The environmental barrier coating systems have been demonstrated for 1650° C. temperature capability and help prime-reliant designs.