Environmental Barrier Coating via Porous Infiltration
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Solution Overview
Problem
Existing methods for forming environmental barrier coatings (EBCs) on silicon-based ceramic materials for high-temperature components, such as gas turbine engines, are inefficient due to the need for multiple deposition and sintering steps, leading to lower productivity and longer cycle times, and these coatings can suffer from rapid recession in combustion environments.
Innovation Solution
A method involving the disposal of a powder-based coating on a substrate, followed by heat-treating to form a porous coating with surface-connected pores, infiltrating these pores with an infiltrant material, and then sintering at a higher temperature to create a thick, hermetic EBC, utilizing a multimodal distribution of particles to control porosity and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If standard slurry-based coating processes are used to achieve desired EBC thickness, then the coating provides protection, but multiple deposition and sintering steps are required which lead to lower productivity and longer cycle time
Solution Approach 1:
The coating process is divided into distinct stages: initial slurry deposition forming a porous green coating, followed by separate infiltration and sintering steps. This segmentation allows each stage to be optimized independently, achieving thick hermetic coatings in fewer overall cycles compared to conventional repeated thin-layer deposition
Solution Approach 2:
The invention changes key process parameters by using a two-stage thermal treatment (initial heating to form porous structure, then final sintering at higher temperature) instead of multiple incremental sintering steps. This parameter change enables thicker coatings to be formed without requiring multiple deposition cycles, thereby improving productivity
2Reliability
If standard slurry-based coating processes are used to achieve desired EBC thickness, then the coating provides protection, but multiple deposition and sintering steps are required which lead to longer cycle time
Solution Approach 1:
The initial slurry deposition and low-temperature heating create a porous green coating structure in advance, preparing the framework for subsequent infiltration and sintering. This preliminary action eliminates the need for multiple incremental deposition cycles, significantly reducing total cycle time while maintaining coating integrity
Solution Approach 2:
The invention merges multiple functions into fewer process steps: the initial deposition creates both the coating framework and the porous structure needed for infiltration, while the final sintering step simultaneously densifies the coating and achieves hermetic seal. This merging reduces the total number of cycles required compared to conventional sequential processes
3Reliability
If thick EBCs are formed using conventional methods, then sufficient protection is achieved, but the process complexity increases due to multiple deposition and sintering steps
Solution Approach 1:
The complex process of forming thick hermetic coatings is segmented into distinct functional stages: slurry deposition, drying, infiltration, and final sintering. Each stage has a specific purpose and can be independently controlled, simplifying the overall process complexity compared to conventional methods requiring multiple repeated deposition and sintering cycles
4Temperature
If silicon-based ceramic materials are used for high temperature components, then desirable high temperature characteristics are achieved, but rapid recession occurs in combustion environments due to volatilization
Solution Approach 1:
The EBC is formed as a composite structure combining the silicon-based ceramic substrate with a multi-layer coating system including porous green coating, infiltrant material, and sintered outer layer. This composite structure provides the high temperature characteristics of silicon-based ceramics while the coating layers protect against volatilization by creating a barrier to reactive species
Solution Approach 2:
The porous green coating layer acts as a transition structure that allows controlled infiltration of protective materials while maintaining thermal shock resistance. The porosity enables the coating to accommodate thermal expansion differences between substrate and coating materials, preventing cracking that would compromise protection against volatilization
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
This method enables the efficient formation of thick, hermetic EBCs with improved thermal and chemical resistance, reducing recession and maintaining adhesion, while simplifying the process and reducing cycle time compared to conventional slurry-based methods.
Implementation Method 1
heat-treating the coating at a temperature greater than 800°C and less than 1200°C to form a porous coating
Implementation Method 2
infiltrating at least some of the surface-connected pores of the porous coating with an infiltrant material
Implementation Method 3
sintering the infiltrated coating at a temperature greater than 1200°C and less than 1500°C to form the environmental barrier coating
Data Source
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AI summary
Methods of forming an environmental barrier coating (20) are disclosed. A method includes disposing a powder-based coating on a substrate (12), heat-treating the powder-based coating at a temperature greater than 800°C and less than 1200°C to form a porous coating that includes surface-connected pores, infiltrating at least some of the surface-connected pores of the porous coating with an infiltrant material to form an infiltrated coating, and sintering the infiltrated coating at a temperature greater than 1200°C and less than 1500°C to form the environmental barrier coating (20) on the substrate (12).