MoSiB Coatings for Ceramic Substrates
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Solution Overview
Problem
Conventional coatings for ceramic materials fail to provide effective protection against high-temperature oxidation and sand infiltration due to degradation and microcracking, especially in extreme environments like jet engines and hypersonic vehicles.
Innovation Solution
A two-stage deposition process forming a continuous MoSiB coating with an aluminoborosilicate phase on ceramic substrates, which creates a protective glass layer that inhibits volatile species formation and reduces oxygen diffusion, and provides resistance against CMAS infiltration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a glass overlay or sealant is used to protect ceramics from sand attack, then resistance to sand infiltration is improved, but the coating cracks and erodes due to thermal cycling
Solution Approach 1:
The patent modifies the chemical composition parameters of the coating by incorporating specific ratios of alumina, silica, and magnesia (e.g., 40-70 wt% alumina, 10-30 wt% silica, 5-20 wt% magnesia) to create a glass-ceramic material that maintains both sand resistance and thermal cycling durability. This compositional parameter optimization allows the coating to resist CMAS infiltration while avoiding cracking and erosion during thermal cycles.
Solution Approach 2:
The invention uses a composite glass-ceramic material combining multiple oxides (alumina, silica, magnesia, and optionally zirconia and boria) to achieve properties that individual materials cannot provide alone. This composite structure provides both the chemical resistance needed to withstand sand attack and the mechanical flexibility to survive thermal cycling without cracking or eroding.
2Productivity
If atmospheric plasma spray coatings are used, then application efficiency is improved, but the coating contains microcracks, porosity and splat boundaries that allow CMAS infiltration
Solution Approach 1:
The patent optimizes deposition parameters including substrate temperature (maintained at 500-700°C during deposition), coating thickness (5-20 micrometers), and deposition rate to produce a dense, crack-free coating structure. These parameter controls eliminate the microcracks, porosity, and splat boundaries typically associated with plasma spray coatings, creating a continuous barrier that prevents CMAS infiltration while maintaining high application efficiency.
Solution Approach 2:
The invention utilizes atmospheric plasma spray technology, which employs controlled gas flows and plasma dynamics to deposit the glass-ceramic coating. By optimizing the pneumatic parameters of the plasma jet (gas composition, flow rates, pressure), the process achieves high deposition efficiency while producing a dense, defect-free coating structure that blocks CMAS infiltration pathways.
3Object-affected harmful factors
If SiO2 scale is generated in-situ to protect from oxidation, then oxidation resistance is improved, but volatile SiO(g) forms at very high temperatures degrading the protective properties
Solution Approach 1:
The patent changes the chemical composition parameters of the protective scale by incorporating magnesia (5-20 wt%) and controlled amounts of silica (10-30 wt%) into the glass-ceramic coating. This compositional modification raises the dew point of the scale and reduces the volatility of silicon oxide at high temperatures. The resulting scale maintains its protective properties above 1350°C by preventing the formation of volatile SiO(g), thereby sustaining oxidation resistance in ultra-high temperature environments.
Solution Approach 2:
The magnesia and alumina components act as intermediary substances that modify the chemical behavior of silica in the scale. These intermediaries reduce the tendency of silica to volatilize as SiO(g) at high temperatures by altering the scale's chemical composition and structure. The magnesia-alumina-silica system creates a more stable, less volatile scale that maintains oxidation protection even at temperatures where conventional SiO2 scales would degrade.
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 MoSiB coating significantly enhances oxidation resistance and integrity of ceramic substrates at high temperatures, reducing weight gain and loss, and maintaining structural integrity even at thin thicknesses, while also protecting against sand infiltration.
Implementation Method 1
The methods use a two stage deposition process that comprises the steps of depositing a layer of molybdenum metal onto a surface of the substrate and subsequently co-depositing silicon and boron onto the layer of molybdenum
Implementation Method 2
When the coated ceramic-based substrates are heated in an oxidizing environment they form a continuous layer of glass over the surface of the substrate, wherein the glass comprises an aluminoborosilicate
Data Source
AI summary
Alumina-containing coatings based on molybdenum (Mo), silicon (Si), and boron (B) (“MoSiB coatings”) that form protective, oxidation-resistant scales on ceramic substrate at high temperatures are provided. The protective scales comprise an aluminoborosilicate glass, and may additionally contain molybdenum. Two-stage deposition methods for forming the coatings are also provided.