Engineered Surface Roughness for Thermal Barrier Coating Adhesion
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Solution Overview
Problem
Existing techniques for enhancing the adhesion of ceramic thermal barrier coatings in gas turbine engines are inadequate due to variability in the mechanical interface between layers, particularly in advanced applications where random surface roughness methods are insufficient.
Innovation Solution
A method involving engineered surface roughness on substrate and bond coat materials, achieved through designed mold surfaces and precise casting processes, to create controlled mechanical interconnections between the substrate, bond coat, and ceramic thermal barrier coatings, allowing for varying physical parameters and thicknesses to optimize adhesion and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If random surface roughness methods are used to enhance adhesion, then adhesion is improved, but variability in the mechanical interface between layers increases
Solution Approach 1:
The patent transitions from random surface roughness to engineered surface roughness with controlled parameters. The mold surfaces are designed with specific roughness characteristics (amplitude, wavelength, distribution) that are replicated consistently in the coating layers, providing predictable and reliable mechanical interconnection without the variability of random roughness methods.
Solution Approach 2:
The patent applies different surface roughness characteristics to different locations and layers. The substrate mold has a first surface roughness, the bond coat mold has a second surface roughness, and these are replicated in the respective coating layers, allowing optimization of adhesion at each interface while maintaining overall system reliability.
2Strength
If traditional bond coat layers are used, then adhesion is achieved, but the thickness of ceramic layers is limited
Solution Approach 1:
The patent incorporates surface roughness engineering into the mold design before casting, creating pre-formed mechanical interconnection features in both the substrate and bond coat layers. This preliminary structuring enables thicker ceramic layers to be applied with reliable adhesion, as the mechanical interconnection is established in advance rather than relying solely on the bond coat chemistry.
Solution Approach 2:
The patent creates a composite structure combining engineered surface roughness features with coating materials. The mechanical interconnection arises from the combination of the roughened substrate surface, the bond coat material filling the roughness features, and the overlay ceramic layer, enabling thicker ceramic applications with improved adhesion.
3Strength
If spray process parameters are controlled to create surface roughness, then adhesion is improved, but manufacturing precision decreases
Solution Approach 1:
The patent uses molds to copy and replicate the desired surface roughness pattern. The mold surfaces are precisely engineered with the required roughness characteristics, and this pattern is replicated consistently in each casting operation, providing manufacturing precision that cannot be achieved through spray process control alone.
Solution Approach 2:
The patent replaces the spray deposition process (which relies on controlling spray parameters to create roughness) with a casting process using pre-engineered molds. This substitution transfers the roughness creation from a process-dependent mechanical action to a mold-based geometric replication, significantly improving consistency and precision.
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
This approach provides enhanced adhesion and durability of ceramic thermal barrier coatings, enabling thicker monolithic ceramic layers (up to 3.0 mm) on metal substrates for high-temperature applications, with improved mechanical interconnections and reduced reliance on traditional bond coat layers, enhancing performance in gas turbine engines.
Implementation Method 1
Another mold (bond layer mold) is formed to have another designed surface roughness on an interior surface. The green body is removed from the first mold and is positioned within the second mold with a small controlled space separating the green body surface from the second mold surface. A bond coat material is then cast in slurry form into the space and allowed to solidify.
Data Source
AI summary
A method of manufacturing a substrate (16) with a ceramic thermal barrier coating (28, 32). The interface between layers of the coating contains an engineered surface roughness (12, 24) to enhance the mechanical integrity of the bond there between. The surface roughness is formed in a surface of a mold (10,20) and is infused by a subsequently cast layer of material (16, 28). The substrate may be partially sintered (76) prior to application of the coating layer(s) and the coated substrate and coating layer(s) may be co-sintered to form a fully coherent strain-free interlayer.