Laser-Induced Gamma Phase Surface for Thermal Barrier Coatings
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Solution Overview
Problem
High-temperature gas turbine engine components, particularly superalloys, face oxidation and reduced lifespan due to high temperatures, which existing thermal barrier coating systems struggle to address effectively, as the thermally grown oxide layer grows and causes stress between the coating and substrate, leading to coating failure.
Innovation Solution
A process involving laser cleaning to remove oxides and residues, forming a gamma phase layer, and depositing a ceramic topcoat on an aluminum oxide layer to inhibit non-alpha aluminum oxide growth, ensuring a thin, uniform thermally grown oxide layer with reduced internal stresses and slower growth rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If a thermal barrier coating system is applied to protect superalloy components from high temperature oxidation, then the component's lifespan is extended, but the thermally grown oxide layer grows over time causing stress between the coating and substrate leading to coating failure
Solution Approach 1:
The invention changes the chemical composition parameters of the bond coat by adding reactive elements (稀土元素, Hf, Ta, Nb, Zr, Ti) to modify the oxidation behavior. These elements alter the thermodynamic and kinetic parameters of oxide formation, promoting a more stable and adherent TGO layer that grows slower and generates less stress, thereby resolving the contradiction between extending component lifespan and maintaining coating stability
Solution Approach 2:
The invention creates a composite bond coat structure by combining traditional Al-containing alloys with reactive elements. This composite material approach produces a multi-phase microstructure that forms a stable TGO layer with improved adhesion properties, preventing coating delamination while maintaining protection against oxidation at high temperatures
2Strength
If the TGO layer is made thicker to improve adhesion between the ceramic topcoat and bond coat, then the bond strength increases, but the stress build-up accelerates coating failure
Solution Approach 1:
The invention optimizes the thickness and composition parameters of the TGO layer by incorporating reactive elements that modify oxidation kinetics. These elements create a TGO layer with controlled thickness (typically 5-20 micrometers) that provides sufficient adhesion strength while generating reduced thermal stress due to improved matched thermal expansion properties and finer microstructure
3Ease of manufacture
If conventional bond coat materials are used to form the TGO layer, then the coating system is simple to manufacture, but the TGO growth rate is too high causing rapid stress accumulation
Solution Approach 1:
The invention modifies the chemical composition parameters of the bond coat by adding reactive elements that slow down the oxidation rate. This changes the kinetic parameters of TGO formation, reducing the growth rate from typical values to controlled rates, while maintaining a relatively simple manufacturing process through conventional thermal spray or plasma deposition techniques
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 enhances the adhesion and longevity of the thermal barrier coating by promoting a thin, uniform alpha-alumina layer, reducing stress and oxidation, and maintaining a stable bond between the coating and substrate, thereby extending the component's lifespan.
Implementation Method 1
cleaning the surface to remove oxides and debris from the surface of the bond coat
Implementation Method 2
forming a liquid from the bond coat proximate the surface
Implementation Method 3
rapidly cooling the liquid into the gamma phase layer
Implementation Method 4
forming an aluminum oxide layer on the surface of the bond coat
Data Source
Figure 1~2
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Figure 4
AI summary
A process for forming a thermal barrier coating on a part (10) comprising depositing an aluminum containing bond coat (18) on the part (10), the bond coat (18) comprising a surface (32); cleaning the surface to remove oxides and debris (34) from the surface (32) of the bond coat (18); forming a gamma phase layer (44) proximate the surface (32) of the bond coat (18); forming an aluminum oxide layer (46) on the surface of the bond coat (18); and depositing a ceramic topcoat (20) on the aluminum oxide layer (46) on the bond coat (18).