Ceramic Matrix Composite Substrate With Creep-Resistant Outer Layer
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Solution Overview
Problem
Current ceramic matrix composites (CMCs) face limitations in mechanical properties and creep resistance, especially at high temperatures, due to residual porosity and free silicon content, which affects their performance in applications like gas turbines.
Innovation Solution
A ceramic matrix composite article is formed with a dense substrate and a creep-resistant outer layer, where the substrate is made by melt infiltration and the outer layer is created using a different process, such as polymer impregnation and pyrolysis, to reduce free silicon content and increase porosity, thereby enhancing creep resistance and temperature capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If melt infiltration is used to form CMC substrate, then density is improved (residual porosity reduced to near zero), but free silicon content increases which limits temperature capability
Solution Approach 1:
The CMC article is divided into two distinct parts: a dense substrate formed by melt infiltration and an outer layer formed by chemical vapor infiltration. This segmentation allows each part to have optimized properties for its specific function, with the substrate providing structural integrity and the outer layer providing high-temperature creep resistance.
Solution Approach 2:
Different regions of the CMC article are given different material compositions and structures. The substrate region has high density with near-zero porosity but contains free silicon, while the outer layer has lower density with controlled porosity and minimal free silicon, creating local quality variations that optimize overall performance.
2Temperature
If chemical vapor infiltration is used to form CMC, then free silicon content is reduced (improving temperature capability), but residual porosity increases to 10-15 percent which reduces mechanical properties
Solution Approach 1:
The CMC article is divided into two distinct parts: a dense substrate formed by melt infiltration and an outer layer formed by chemical vapor infiltration. This segmentation allows each part to have optimized properties for its specific function, with the substrate providing structural integrity and the outer layer providing high-temperature creep resistance.
Solution Approach 2:
Different regions of the CMC article are given different material compositions and structures. The substrate region has high density with near-zero porosity but contains free silicon, while the outer layer has lower density with controlled porosity and minimal free silicon, creating local quality variations that optimize overall performance.
3Manufacturing precision
If CVI is used for outer layer formation, then porosity is reduced in outer portion, but inner portion retains high porosity creating non-uniform structure
Solution Approach 1:
The CMC article is divided into two distinct parts: a dense substrate formed by melt infiltration and an outer layer formed by chemical vapor infiltration. This segmentation allows each part to have optimized properties for its specific function, with the substrate providing structural integrity and the outer layer providing high-temperature creep resistance.
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 approach results in a CMC article with improved mechanical properties and increased temperature capability, extending the temperature limit by up to 150°C (300°F) above the melting point of silicon, reducing fuel consumption, and enhancing performance in high-stress, high-temperature environments.
Implementation Method 1
one approach includes melt infiltration (MI), which employs a molten silicon to infiltrate into a fiber-containing perform
Implementation Method 2
CVI is a process whereby a matrix material is infiltrated into a fibrous preform by the use of reactive gases at elevated temperature
Implementation Method 3
the outer layer is created using a different process, such as polymer impregnation and pyrolysis
Data Source
Figure 1
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AI summary
A ceramic matrix composite article 10 includes a melt infiltration ceramic matrix composite substrate 20 comprising a ceramic fiber reinforcement material in a ceramic matrix material having a first free silicon proportion, and a melt infiltration ceramic matrix composite outer layer 50 comprising a ceramic fiber reinforcement material in a ceramic matrix material having a second free silicon proportion disposed on an outer surface of at least a portion of the substrate, or a polymer impregnation and pyrolysis ceramic matrix composite outer layer comprising a ceramic fiber reinforcement material in a ceramic matrix material having a second free silicon proportion disposed on an outer surface of at least a portion of the substrate. The second free silicon proportion is less than the first free silicon proportion.