Pressure Sintering Environmental Barrier Coatings on Textured Ceramic Substrates
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Solution Overview
Problem
Ceramic materials used in gas turbine engines undergo erosion due to reactive water vapor, leading to reduced engine efficiency, and existing environmental barrier coatings (EBCs) often delaminate due to silica layer formation during sintering in air atmospheres, limiting their protective effectiveness.
Innovation Solution
A method of pressure sintering an environmental barrier coating with rare earth silicate on a textured ceramic substrate in an inert or nitrogen atmosphere, eliminating the silica layer and ensuring direct contact for enhanced adhesion and protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sintering is done in an air atmosphere on a silicon nitride ceramic material, then the environmental barrier coating can be applied, but a silica layer forms on the top surface of the ceramic material under the coating which prevents intimate contact and leads to delamination
Solution Approach 1:
The patent applies an inert or reducing atmosphere (such as nitrogen, argon, or hydrogen) during the sintering process to prevent oxidation of the silicon nitride ceramic substrate. This eliminates the formation of the silica layer that would otherwise form in air atmosphere, allowing the environmental barrier coating to make intimate contact with the substrate surface and achieve strong adhesion without delamination.
2Manufacturing precision
If standard slurry-based coating processes are used, then environmental barrier coating can be deposited, but multiple deposition and sintering steps are required to achieve desired thickness without cracking which leads to lower productivity and longer cycle times
Solution Approach 1:
The patent combines multiple coating deposition and sintering steps into a single continuous process. By using a specialized slurry formulation and applying it in one or two stages followed by a single sintering operation in inert atmosphere, the method achieves the desired coating thickness without the need for multiple separate deposition and sintering cycles, thereby improving productivity and reducing cycle times.
3Temperature
If ceramic materials are exposed to combustion environments with water vapor, then they can operate at high temperatures, but the water vapor reacts with the ceramic to cause erosion known as recession which reduces engine efficiency
Solution Approach 1:
The environmental barrier coating serves as an intermediary layer between the ceramic substrate and the combustion environment. This coating barrier prevents direct contact between the water vapor in the combustion gases and the silicon nitride or silicon carbide ceramic material, thereby preventing the chemical reactions that cause erosion and recession while allowing the ceramic to operate at high temperatures.
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 achieves an adhesion of greater than 1,000 psi after 2,000 hours of steam exposure and maintains less than 50% debit in flexural strength, outperforming conventional EBCs by preventing silica layer formation and ensuring robust coating-substrate interaction.
Implementation Method 1
etching a surface of the ceramic substrate to texture the surface
Implementation Method 2
pressure sintering the environmental barrier coating on the etched surface of the ceramic substrate
Implementation Method 3
pressure sintering the environmental barrier coating on the etched surface of the ceramic substrate in an inert or nitrogen atmosphere at a pressure of greater than atmospheric pressure
Implementation Method 4
pressure sintering the environmental barrier coating on the etched surface of the ceramic substrate in an inert or nitrogen atmosphere
Implementation Method 5
the step of pressure sintering produces a mass of the environmental barrier coating including from about 0.1 to about 20 weight percent of liquid glass and the liquid glass is disposed in the texture of the surface of the ceramic substrate
Data Source
AI summary
A method of pressure sintering an environmental barrier coating on a surface of a ceramic substrate to form an article is provided. The method includes the steps of etching the surface of the ceramic substrate to texture the surface, disposing an environmental barrier coating on the etched surface of the ceramic substrate. The environmental barrier coating includes a rare earth silicate, and pressure sintering the environmental barrier coating on the etched surface of the ceramic substrate in an inert or nitrogen atmosphere such that at least a portion of the environmental barrier coating is disposed in the texture of the surface of the ceramic substrate thereby forming the article.