MI-CMC Infiltration Repair to Limit Void Formation
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Solution Overview
Problem
Conventional reactive melt infiltration manufacturing practices for ceramic matrix composites (CMCs) result in void formation during re-working, repairing, or joining processes due to the back-drawing of silicon alloy through capillary actions in carbon wicks, leading to defects in already-infiltrated MI-CMC components.
Innovation Solution
The use of pre-saturated wicks and strategically arranged infiltrant feedstocks with controlled melting points to prevent the back-drawing of silicon alloy, ensuring continuous alloy supply and minimizing void formation in MI-CMC components during secondary melt infiltration steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of repair
If conventional reactive melt infiltration processes are used to repair or join CMC components, then the components can be re-worked or joined, but void formation occurs due to silicon alloy drainage through capillary actions in carbon wicks
Solution Approach 1:
The carbon wicks are pre-saturated with silicon alloy before the repair process begins. This preliminary saturation ensures that the wicks have a reservoir of alloy to supply during infiltration, preventing the wicks from drawing alloy away from the repair area through capillary action and thus preventing void formation
Solution Approach 2:
The melting point of the infiltrant feedstock is controlled to be lower than or equal to the melting point of the silicon alloy already present in the CMC component. This parameter change ensures that the infiltrant melts and flows into the repair area before any back-drawing can occur, maintaining continuous alloy supply and preventing voids
2Productivity
If silicon alloy is allowed to drain through carbon wicks during infiltration, then the infiltration process can proceed, but voids are formed in the CMC component
Solution Approach 1:
The carbon wicks are pre-saturated with silicon alloy before infiltration begins. This creates an initial reservoir of alloy in the wicks that prevents them from acting as drainage paths during the infiltration process, thereby maintaining component integrity while allowing the infiltration to proceed
Solution Approach 2:
The pre-saturated carbon wicks act as an intermediary between the infiltrant feedstock and the CMC component. They control the flow of silicon alloy, ensuring it moves into the component rather than draining away, thus maintaining reliability while enabling the infiltration process
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 approach effectively limits void formation in MI-CMC components by maintaining a consistent alloy supply, thereby enhancing the integrity and density of the components without introducing additional porosity.
Implementation Method 1
the drainage of silicon alloy through capillary actions in the carbon wicks
Implementation Method 2
the molten phase reacts with a solid phase in the targeted area of the MI-CMC component
Data Source
AI summary
A method for limiting void formation in a melt-infiltrated ceramic matrix composite (MI-CMC) component includes arranging one or more infiltrant feedstocks in fluid communication with a targeted area of the MI-CMC component. The one or more infiltrant feedstocks have a nominal melting point at or below a nominal melting point of an alloy within the MI-CMC component. The method includes heating the one or more infiltrant feedstocks to a first temperature at or above the nominal melting point of the one or more infiltrant feedstocks to form a molten phase. The method also includes infiltrating the targeted area of the MI-CMC component with the molten phase. As such, the molten phase reacts with a solid phase in the targeted area of the MI-CMC component. Further, the method includes cooling the MI-CMC component to a second temperature that is below the first temperature to solidify the molten phase.