CMC Part Manufacturing via Molten Silicon Infiltration

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Solution Overview

Problem

Existing methods for manufacturing ceramic matrix composite (CMC) parts using the melt-infiltration process face challenges in achieving low porosity, especially in thick parts greater than 5 mm, due to poor wetting of SiC particles by molten silicon.

Innovation Solution

The method involves producing a fibrous preform from silicon carbide (SiC) fibers, consolidating it through gas-phase chemical infiltration, and then injecting a slurry containing SiC particles with an organic binder. The organic binder is pyrolyzed to form an amorphous carbon residue, which reduces the silica or silicon oxycarbide on the SiC particles, improving their wettability by molten silicon.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a slurry without organic binder is used for SiC particle injection, then the infiltration process is simpler, but the SiC particles are poorly wetted by molten silicon causing porosity in thick parts

Engineering Contradiction:

Improvematerial healthVSAvoidprocess complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The organic binder is introduced into the slurry before injection, and its carbon residue is formed by pyrolysis before infiltration to pre-condition the SiC particle surfaces for improved wetting during subsequent molten silicon infiltration

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The carbon residue from pyrolyzed organic binder acts as an intermediary substance that facilitates the interaction between molten silicon and SiC particles, improving wetting by reducing the contact angle through chemical reduction of silica/SiOC layers

Inventive Principle:

Principle #24Intermediary (Mediator)

2Length of stationary object

If the part thickness is increased beyond 5 mm, then the structural capability is improved, but porosity appears in the core of the part

Engineering Contradiction:

Improvepart thicknessVSAvoidmaterial health

Core Design Contradiction:

Length of stationary objectVSReliability

Solution Approach 1:

The chemical composition and surface properties of SiC particles are modified through carbon reduction of silica/SiOC layers, changing the wettability parameters to enable proper infiltration even in thick parts where infiltration path is longer

Inventive Principle:

Principle #35Parameter changes

3Stability of the object's composition

If SiC particles with silica or SiOC surface layers are used, then the particle stability is improved, but the wettability by molten silicon deteriorates due to contact angle greater than 90°

Engineering Contradiction:

Improveparticle stabilityVSAvoidwetting ability

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The surface chemical composition of SiC particles is changed by reducing silica/SiOC layers through reaction with carbon from pyrolyzed organic binder, transforming the surface from hydrophobic (contact angle >90°) to hydrophilic for molten silicon wetting

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The silica/SiOC surface layers that initially cause poor wetting are converted into beneficial SiC surface layers through carbon reduction, transforming the harmful effect into a beneficial one while maintaining particle stability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 reduces porosity in thick CMC parts, ensuring good material health and densification, even in parts thicker than 5 mm, by enhancing the wetting and infiltration of molten silicon into the preform.

Implementation Method 1

a step of forming an amorphous carbon residue by pyrolysing the organic binder

Methodology Applied

Scientific EffectPyrolysis: Pyrolysis

Implementation Method 2

a step of carbon reduction of the silicon oxycarbide and silica present on the surface of the silicon carbide particles by the carbon residue

Methodology Applied

Scientific EffectCarbon reduction: Reduction

Implementation Method 3

infiltrating the preform with a composition based on molten silicon

Methodology Applied

Scientific EffectMelt infiltration: Melting

Data Source

PatentUS20250091959A1Method for manufacturing a thick part made of CMC composite material

Publication Date: 2025.03.20 SAFRAN CERAMICS SA

AI summary

A method for manufacturing a part made of ceramic matrix composite (CMC) material includes producing a fibrous preform from silicon carbide fibres; consolidating the fibrous preform by gas-phase chemical infiltration; injecting a slurry including a silicon carbide particle powder into the consolidated fibrous preform; and densifying by infiltrating the preform with a composition based on molten silicon to give a part made of CMC material. The slurry further includes at least one organic binder. The method includes, prior to the infiltrating of the preform with a composition based on molten silicon, pyrolysing the organic binder so as to form a carbon-containing residue in the fibrous preform.