Dense Silicon Bond Coat for Low-Porosity Ceramic Composites
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Solution Overview
Problem
Existing thermal spray techniques for forming bond coats on ceramic or ceramic matrix composites result in high porosity and surface roughness, leading to reduced adhesion, increased exposure to environmental species, and decreased longevity of the substrate.
Innovation Solution
A suspension thermal spray technique using fine particle silicon-based materials with a carrier fluid to deposit a dense bond coat with low porosity and reduced surface roughness, eliminating the need for initial surface preparation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional thermal spray techniques are used to form bond coats on ceramic substrates, then the coating process is simple and fast, but the resulting bond coat has high porosity and surface roughness which reduces adhesion and increases exposure to environmental species
Solution Approach 1:
The patent applies parameter changes by using fine particle silicon-based materials (particle size <10 μm) instead of conventional larger particles, and by controlling the suspension concentration and carrier fluid properties. These parameter changes result in a dense bond coat with low porosity (<5%) and reduced surface roughness, improving adhesion while minimizing exposure to environmental species.
Solution Approach 2:
The patent uses composite materials by combining silicon-based coating material with a carrier fluid to form a suspension. This composite approach allows the coating material to be delivered in a controlled manner, forming a dense, adherent bond coat that reduces porosity and surface roughness compared to conventional thermal spray methods.
2Duration of action of stationary object
If conventional thermal spray techniques are used to form bond coats, then the coating process is straightforward, but the high porosity increases exposure to environmental species and decreases substrate longevity
Solution Approach 1:
By changing the particle size parameter to fine particles (<10 μm) and controlling suspension concentration (20-50 wt%), the patent achieves a dense bond coat with porosity <5%. This dense structure provides superior protection against environmental species penetration, thereby extending substrate longevity in high-temperature applications.
Solution Approach 2:
The bond coat acts as a sacrificial protective layer that consumes itself to protect the expensive ceramic substrate. By forming a dense, low-porosity bond coat, the protective function is enhanced, allowing the substrate to withstand harsh environments for extended periods before the bond coat requires replacement.
3Manufacturing precision
If fine particle materials are used in suspension thermal spray, then dense coating with low porosity is achieved, but the coating material requires suspension in carrier fluid and more complex deposition process
Solution Approach 1:
The patent uses hydraulic principles by suspending coating material in a carrier fluid (water or alcohol-based). This suspension can be delivered through conventional spray equipment, using the fluid dynamics of the carrier to transport and deposit the fine particle coating material uniformly, achieving dense coatings without requiring complex specialized equipment.
Solution Approach 2:
The carrier fluid acts as an intermediary between the fine particle coating material and the substrate. It enables the fine particles to be delivered uniformly through the spray system and facilitates controlled deposition, achieving dense coating formation while using relatively simple conventional spray equipment.
4Reliability
If fine particle suspension is used for coating deposition, then low porosity and reduced surface roughness are achieved, but the production time increases due to suspension preparation and deposition process
Solution Approach 1:
The suspension is prepared in advance with fine particle coating material dispersed in carrier fluid at controlled concentration (20-50 wt%). This preliminary preparation ensures uniform particle distribution and prevents agglomeration during spraying, enabling efficient deposition that achieves dense, high-quality coatings without requiring excessive processing time or multiple passes.
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 dense bond coat improves adhesion, reduces exposure to environmental species, increases substrate longevity, and lowers production costs by minimizing porosity and surface roughness.
Implementation Method 1
introducing the suspension into a heated plume formed by a thermal spray device and directing the heated plume toward the substrate to melt and deposit the coating material on the substrate
Implementation Method 2
The carrier may comprise a water-based or an alcohol-based fluid
Data Source
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AI summary
A method that includes introducing a suspension comprising a coating material and a carrier into a heated plume of a thermal spray device. The coating material may include silicon or a silicon alloy. The method further includes directing the coating material using the heated plume toward a substrate that includes a ceramic or a ceramic matrix composite and depositing the coating material to form a bond coat directly on the substrate such that the bond coat defines a porosity of less than about 3 percent by volume.