Strain Tolerant Thermal Barrier Coating for Gas Turbines
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Solution Overview
Problem
Existing thermal barrier coatings for gas turbine engine components like combustor panels and fuel nozzles suffer from sintering and accelerated stress buildup due to local hotspots, leading to reduced durability and shortened service life, as they have low thermal conductivity and are prone to spallation and thermal fatigue.
Innovation Solution
A thermal barrier coating system comprising a single crystal superalloy substrate with a gamma-gamma prime bondcoat and a ceramic composition layer deposited using electron beam physical vapor deposition, creating a columnar microstructure for enhanced strain tolerance and resistance to sintering, with specific composition ranges and processing conditions to achieve optimal thermal conductivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If plasma spray process is used to create porosity for low thermal conductivity, then thermal insulation is improved, but resistance to sintering at hotspots deteriorates
Solution Approach 1:
The invention changes the microstructural parameters of the thermal barrier coating by controlling crystal grain size and phase composition. The coating contains a mixture of crystalline phases (perovskite, pyrochlore, and/or spinel) with specific grain size ranges (0.5-5.0 micrometers) that provide both thermal insulation and sintering resistance. This parameter optimization resolves the contradiction by achieving low thermal conductivity through controlled porosity while maintaining structural integrity at hotspots through appropriate phase selection and grain size control.
Solution Approach 2:
The invention creates a composite ceramic coating system containing multiple phases (perovskite, pyrochlore, and/or spinel) with distinct properties. The perovskite phase provides thermal insulation, while the pyrochlore and spinel phases contribute to sintering resistance and structural stability. This composite approach allows the coating to simultaneously achieve low thermal conductivity and high resistance to sintering at local hotspots.
2Temperature
If low thermal conductivity coating is applied to reduce metal temperature, then component durability is improved, but stress buildup at hotspots is accelerated
Solution Approach 1:
The invention optimizes the microstructural parameters of the coating, specifically controlling porosity distribution, crystal grain size (0.5-5.0 micrometers), and phase composition. These parameter changes create a coating that maintains low thermal conductivity for heat protection while the fine-grained multiphase structure provides stress distribution and crack deflection mechanisms that reduce stress buildup at hotspots, preventing accelerated damage.
Solution Approach 2:
The invention utilizes a controlled porous structure in the thermal barrier coating with optimized porosity levels and distribution. The porous structure provides thermal insulation by trapping air pockets that reduce heat conduction, while the controlled pore size and distribution prevent stress concentration and facilitate stress relaxation, thereby reducing stress buildup at hotspots despite the low thermal conductivity.
3Loss of energy
If plasma sprayed coating is used to achieve low thermal conductivity, then thermal insulation is improved, but coating life is significantly shortened due to sintering
Solution Approach 1:
The invention employs a composite ceramic coating system containing perovskite, pyrochlore, and/or spinel phases that work synergistically. The perovskite phase provides the necessary thermal insulation with low thermal conductivity, while the pyrochlore and spinel phases contribute to high-temperature stability and sintering resistance. This composite composition maintains both excellent thermal insulation properties and extended coating life by preventing sintering degradation at local hotspots during prolonged service.
Solution Approach 2:
The invention optimizes critical microstructural parameters including porosity (10-40%), crystal grain size (0.5-5.0 micrometers), and phase composition ratios. These parameter changes create a coating structure that achieves low thermal conductivity for thermal insulation while the fine-grained multiphase microstructure provides resistance to sintering, thereby extending coating life significantly compared to conventional plasma-sprayed coatings.
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 coating system provides improved resistance to sintering and thermal fatigue, allowing for higher operating temperatures without accelerated damage accumulation, resulting in extended part life and increased engine performance by minimizing stress buildup and CMAS penetration.
Implementation Method 1
a ceramic composition coating applied over said substrate... depositing a ceramic composition layer using an electron beam physical vapor deposition technique
Implementation Method 2
The coating deposited in the foregoing manner has a low thermal conductivity since the plasma spray process can be parameterized to produce porosity that is oriented predominantly perpendicular to the direction of the flow of heat through the coating
Data Source
Figure 1~2
Figure 3a~3c
Figure 3d~3f
AI summary
A method for forming a thermal barrier coating on a combustor panel or a fuel nozzle comprises the steps of: providing a component selected from the group consisting of a combustor panel, a bulkhead heat shield, and a fuel nozzle; optionally depositing a first layer of a metallic alloy onto the component; and depositing a ceramic composition layer using an electron beam physical vapor deposition technique. If the component is formed from a yttrium or other active element doped single crystal superalloy, the first layer may be omitted and the ceramic composition layer may be deposited directly onto a surface of the component.