Thermal Barrier Coating with Perovskite Top Layer for CMAS Resistance
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Solution Overview
Problem
Thermal barrier coatings in turbomachines, particularly aircraft engines, face failure due to penetration of dust and sand particles, leading to stress and mechanical instability, as existing solutions like sacrificial oxide layers alter mechanical properties and introduce thermal expansion issues.
Innovation Solution
A thermal barrier coating system comprising a fully or partially stabilized zirconium oxide ceramic layer with an oxide top layer containing free α-aluminum oxide, lanthanum, magnesium, silicon, and calcium, with a porosity of 5-30% by volume, providing enhanced corrosion resistance and mechanical stability by reacting with CMAS deposits and maintaining mechanical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an outer aluminum oxide layer is provided on the thermal barrier coating to prevent CMAS penetration, then corrosion resistance is improved, but thermal expansion mismatch causes stresses that lead to coating failure
Solution Approach 1:
The patent applies composite materials by creating a top coat layer containing LaMgAl11O19 perovskite phase with embedded free α-Al2O3 crystals. This composite structure combines the corrosion resistance of aluminum oxide with the thermal expansion compatibility of the perovskite matrix, resolving the contradiction between protection and stability.
Solution Approach 2:
The patent changes the chemical composition parameters of the top coat layer by incorporating lanthanum and magnesium in specific proportions to form the LaMgAl11O19 perovskite phase. This parameter change adjusts the thermal expansion coefficient to match the underlying YSZ layer, eliminating stress-induced failure while maintaining corrosion protection.
2Reliability
If the oxide top layer contains high aluminum oxide content for CMAS resistance, then corrosion protection is improved, but mechanical properties deteriorate due to low thermal expansion
Solution Approach 1:
The patent creates a composite top coat layer where free α-Al2O3 crystals (providing corrosion resistance) are embedded within the LaMgAl11O19 perovskite matrix (providing mechanical stability and thermal expansion compatibility). This composite approach allows both functions to coexist without compromising either property.
Solution Approach 2:
The patent applies local quality by distributing free α-Al2O3 crystals throughout the top coat layer at specific concentrations (at least 20 vol%). This localized presence of high-corrosion-resistance material provides CMAS protection where needed while the surrounding perovskite matrix maintains overall mechanical stability.
3Duration of action of stationary object
If a sacrificial oxide layer is provided to prevent damage to thermal barrier coating, then service life is extended, but layer system complexity increases and mechanical properties change
Solution Approach 1:
The patent applies multi-functionality by designing the LaMgAl11O19 perovskite top coat layer to simultaneously provide corrosion resistance against CMAS, thermal insulation, stress buffering due to matched thermal expansion, and mechanical stability. This single layer performs multiple functions that would otherwise require separate layers, reducing overall system complexity.
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 proposed coating system offers improved service life and corrosion resistance under high-temperature and corrosive conditions, preventing CMAS infiltration and mechanical stress, while maintaining mechanical stability and operational reliability.
Implementation Method 1
reacts with CMAS deposits
Implementation Method 2
the oxide cover layer (5) has a porosity of 5 to 30% by volume
Implementation Method 3
provided with thermal insulation layers on the other hand in order to keep the effective operating temperatures for the metallic materials used low
Data Source
AI summary
The present invention relates to a thermal barrier system for components of a turbomachine, in particular components of a turbomachine subjected to high temperatures or hot gases, comprising a ceramic layer (4) of fully or partially stabilized zirconium oxide and an oxide cover layer (5) comprising aluminium, wherein the oxide cover layer (5) further comprises at least one element from the group consisting of lanthanum, magnesium, silicon, calcium and sodium, wherein the aluminium oxide is present at least partially as free α-AL2O3, and a method for producing a corresponding thermal barrier system.