Machinable Silicon Coating on CMC Combustor Liners

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Solution Overview

Problem

Ceramic matrix composite (CMC) components face challenges in achieving precise dimensional control and surface finish due to the reinforcement fibers, limiting their application in high-temperature environments where accurate machining and secondary operations are necessary.

Innovation Solution

A layer of hardenable silicon material is applied to the CMC surface, which can be machined to achieve desired dimensions and surface finish, using methods like plasma spraying or physical vapor deposition, without compromising the mechanical properties of the CMC.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If fiber reinforcement layer is included to improve durability, then mechanical properties and durability are improved, but surface finish becomes rough and dimensional control becomes inconsistent

Engineering Contradiction:

ImprovedurabilityVSAvoiddimensional control

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The component is divided into two distinct parts: a CMC substrate providing durability and a hardenable coating layer providing precision. The coating layer is applied as a separate functional segment that can be independently machined, allowing the substrate to maintain its fiber reinforcement for durability while the coating provides the precise dimensional control needed for mating surfaces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention creates a composite structure combining CMC material with a hardenable coating material (such as metallic or ceramic coating). This composite approach allows each material to contribute its superior properties: the CMC provides high-temperature resistance and durability, while the hardenable coating provides machinability and dimensional precision.

Inventive Principle:

Principle #40Composite materials

2Strength

If fiber reinforcement layer is included to improve durability, then mechanical properties are improved, but surface finish becomes rough

Engineering Contradiction:

Improvemechanical propertiesVSAvoidsurface finish

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The surface functionality is segmented from the structural functionality. The fiber-reinforced CMC substrate provides structural strength and durability, while a separate hardenable coating layer is applied to the surface specifically to provide the required surface finish and dimensional accuracy for mating surfaces.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hardenable coating acts as an intermediary layer between the rough CMC surface and the mating component. This intermediate layer can be machined to provide the required surface finish, effectively mediating between the structural requirements of the CMC and the surface requirements of the assembly.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Temperature

If CMC material is used for high temperature applications, then thermal properties are improved, but dimensional tolerances beyond fabrication capabilities cannot be achieved

Engineering Contradiction:

Improvethermal propertiesVSAvoiddimensional tolerances

Core Design Contradiction:

TemperatureVSManufacturing precision

Solution Approach 1:

The dimensional precision function is segmented from the thermal performance function. The CMC substrate maintains the thermal properties for high-temperature applications, while a separate hardenable coating layer is applied specifically to provide the precise dimensional tolerances needed for machining and assembly.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the physical state of the coating material from a soft, machinable state during fabrication to a hardened state after coating. This parameter change allows the coating to be easily machined to precise tolerances and then maintain those tolerances under service conditions, effectively bridging the gap between CMC fabrication capabilities and final dimensional requirements.

Inventive Principle:

Principle #35Parameter changes

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 process enables CMC components to be used in a wider range of applications by providing precise dimensional tolerances and improved surface finishes, maintaining the thermal and mechanical properties of the CMC while allowing for machining without disturbing the matrix composition.

Implementation Method 1

using methods like plasma spraying or physical vapor deposition

Methodology Applied

Scientific EffectPlasma spraying: Plasma Spray

Implementation Method 2

using methods like plasma spraying or physical vapor deposition

Methodology Applied

Scientific EffectPhysical vapor deposition: Physical Vapour Deposition

Data Source

PatentEP2366678B1High tolerance controlled surface for ceramic matrix composite component

Publication Date: 2020.07.29 RTX CORP

Figure 1
Figure 2~4

AI summary

A ceramic matrix composite (CMC) component (20) includes a fibre reinforced portion (22) to which is applied a layer of a hardenable material (38) that can be machined to provide a desired dimension and surface finish. The hardenable material may be silicon. The component may be a combustor liner, where the fibre reinforced portion contacts the hot gases and the hardenable material layer is machined to shape to allow the component to be properly mounted. The invention also extends to a method of fabricating the component.