Low Melting Point Silicon Infiltration for CMC Fabrication
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Solution Overview
Problem
The existing Melt Infiltration (MI) process for producing ceramic matrix composite (CMC) materials can degrade fibers due to the high melting point of silicon-based infiltration compositions, leading to reduced mechanical properties, as the melting point exceeds the thermal stability temperature of the fibers.
Innovation Solution
A process involving the production of a consolidated fibrous preform with a coated interphase, followed by partial densification using chemical infiltration and subsequent infiltration with a composition containing silicon and nickel or germanium, which lowers the melting point to ≤1150°C, preventing fiber degradation and maintaining mechanical integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If silicon-based infiltration composition is used for MI process, then densification speed is improved, but fiber thermal stability deteriorates due to high melting point exceeding fiber thermostability
Solution Approach 1:
The patent modifies the chemical composition parameters of the infiltration composition by adding elements such as B, Al, or Ti to silicon. This changes the melting point parameter from above fiber thermostability (pure silicon) to below fiber thermostability (alloyed composition), enabling fast densification without fiber degradation.
Solution Approach 2:
The patent creates a composite infiltration composition by combining silicon with other elements (B, Al, Ti) that have lower melting points. This composite material achieves both fast densification (inherited from silicon) and low melting point (inherited from additives), resolving the contradiction between productivity and temperature.
2Productivity
If silicon-based infiltration composition is used, then densification efficiency is improved, but fiber mechanical properties deteriorate due to fiber degradation at high temperature
Solution Approach 1:
By changing the composition parameters (adding B, Al, or Ti to silicon), the melting point is reduced below fiber thermostability. This parameter change ensures that during MI process, the temperature remains safe for fibers, preventing degradation and maintaining mechanical properties while still achieving efficient densification.
Solution Approach 2:
The patent introduces intermediate elements (B, Al, Ti) as mediators between silicon and fibers. These intermediates lower the melting point of the infiltration composition, acting as a protective mechanism that enables fast densification without directly exposing fibers to degrading high temperatures.
3Temperature
If infiltration composition contains elements to lower melting point, then fiber thermal stability is improved, but deoxidation and wettability properties deteriorate
Solution Approach 1:
The patent optimizes the composition parameters by selecting specific elements (B, Al, Ti) and controlling their proportions. These elements simultaneously achieve low melting point (improving thermal stability) and maintain or enhance deoxidation and wettability properties, resolving the contradiction through multi-functional parameter optimization.
Solution Approach 2:
The patent creates a composite infiltration composition where silicon provides fast densification and the added elements (B, Al, Ti) provide low melting point and improved wettability. This composite material achieves multiple beneficial properties simultaneously, including deoxidation capability, resolving the contradiction between temperature and reliability.
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 allows for effective densification of CMC parts without fiber degradation, maintaining mechanical properties and enabling the use of MI process without risking fiber damage, while also improving resistance to oxidation and corrosion.
Implementation Method 1
infiltration of the fibrous preform with an infiltration composition containing at least silicon and at least one other element capable of lowering the melting temperature of the infiltration composition to a temperature less than or equal to 1150°C
Implementation Method 2
This densification process is known as the MI (Melt Infiltration) process
Implementation Method 3
the partial densification comprising the formation on the interphase of a first matrix phase obtained by chemical infiltration in the gas phase
Data Source
Figure 1
AI summary
The invention relates to a process for fabricating a composite part, comprising the steps of: - producing a consolidated fibrous preform, the fibres of the preform being carbon fibres or ceramic fibres and being coated with an interphase, - obtaining a consolidated and partially densified fibrous preform, the partial densification comprising the formation, on the interphase, on a first matrix phase obtained by chemical vapour infiltration, and - continuation of the densification by infiltration of the fibrous preform with an infiltration composition containing at least silicon and at least one other element capable of lowering the melting point of the infiltration composition to a temperature less than or equal to 1150°C.