CMC Part Inserts Control Silicon Nodule Migration
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Solution Overview
Problem
The existing methods for manufacturing ceramic matrix composite (CMC) parts, such as turbine ring sectors, face challenges with silicon nodules forming during the densification process, which affect dimensional accuracy and adhesion of surface coatings, and are costly and labor-intensive to remove.
Innovation Solution
Incorporating inserts made from a different material than the reinforcement and matrix within the intermediate CMC part to promote the migration of liquid silicon, allowing nodules to form in non-sensitive areas, thereby reducing the need for machining or sandblasting and minimizing material waste.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If liquid silicon is used for densification, then the densification effectiveness is improved, but silicon nodules form on the part surface causing dimensional inaccuracies and coating adhesion problems
Solution Approach 1:
The harmful silicon nodules are extracted and concentrated into specific sacrificial zones rather than being distributed across the entire part surface. The inserts create localized regions where excess silicon migrates and solidifies, separating the harmful effect from the functional surfaces.
Solution Approach 2:
Inserts made of material different from both the reinforcement and matrix act as intermediaries to control silicon migration. These inserts mediate between the liquid silicon and the final part structure, directing silicon flow into designated areas.
2Manufacturing precision
If sandblasting or machining is used to remove nodules, then the surface quality is improved, but the process is slow, laborious, and expensive
Solution Approach 1:
The harmful silicon nodules are converted into a controlled feature by directing their formation into sacrificial zones. Instead of trying to eliminate nodules entirely, the method accepts their formation but controls where they appear, transforming a harmful byproduct into a manageable aspect of the process.
Solution Approach 2:
The inserts are placed in advance during preform preparation to pre-determine where silicon nodules will form. This preliminary action guides the subsequent densification process to concentrate nodules in predetermined sacrificial zones rather than allowing random distribution.
3Ease of repair
If a sacrificial layer of ceramic slurry is applied around the intermediate part, then the reinforcement is protected during nodule removal, but raw material consumption increases significantly
Solution Approach 1:
The part is segmented into functional zones and sacrificial zones. The inserts define boundaries between these zones, allowing differential treatment during densification and post-processing. Functional surfaces remain free of nodules while sacrificial zones absorb them.
Solution Approach 2:
Different regions of the final part have different quality requirements. The inserts enable local quality control by directing silicon migration away from functional surfaces and into sacrificial zones, allowing each region to have the appropriate surface quality for its function.
4Manufacturing precision
If multiple temperature zones are used to control the cooling front, then the silicon migration is improved, but the oven complexity and cost increase
Solution Approach 1:
The inserts themselves perform the function of controlling silicon migration during cooling. Rather than requiring a complex multi-zone oven to control the cooling front, the inserts passively guide silicon flow based on their placement and material properties, making the system self-regulating.
Solution Approach 2:
The inserts act as intermediaries that translate thermal gradients into controlled silicon migration patterns. They mediate between the thermal field and the silicon flow, providing control without requiring complex thermal management equipment.
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 controls the formation and location of silicon nodules, reducing manufacturing costs and cycle time while maintaining the part's performance and coating integrity.
Implementation Method 1
at least one insert, which is made from a material different from that of the reinforcement and the matrix and which is designed to promote migration of liquid silicon within the intermediate part during a step of densifying the intermediate part
Implementation Method 2
the silicon being denser in the solid state than in the liquid state, its cooling and its solidification leads to the exit of a portion of the liquid silicon in the form of drops solidifying on the surface of the part
Data Source
AI summary
Method for manufacturing a part made from CMC for improving control of the step of densifying the part, and intermediate part for implementing said method, the intermediate part comprising a reinforcement, a matrix comprising a ceramic material, and at least one insert, which is made from a material different from that of the reinforcement and the matrix and which is designed to promote migration of liquid silicon within the intermediate part during a step of densifying the intermediate part.