Multi-Layer Coating for Gas Turbine Thermal Management
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Solution Overview
Problem
High-performance gas turbine engine components, especially secondary seals, face excessive thermal loading due to increased temperatures from hot exhaust gases and infrared radiation, leading to potential melting and warpage, as existing thermal barrier coatings like YSZ are insufficient in protecting against these heat loads.
Innovation Solution
A multi-layer coating system comprising an infrared radiation interaction layer that reflects or absorbs IR, a performance layer with microspheres for thermal insulation, and a compliance layer to mitigate thermal mismatch between the substrate and performance layer, effectively reducing heat transfer and infrared penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If YSZ thermal barrier coating is used, then thermal insulation is provided, but infrared radiation penetrates through the coating causing substrate heating
Solution Approach 1:
The patent applies a composite coating system consisting of multiple layers with different materials and properties. The outer layer contains infrared-interactive particles (such as pigments or ceramics) that absorb or reflect infrared radiation, while the inner layer provides thermal barrier protection. This composite structure addresses both the thermal insulation requirement and the infrared radiation protection requirement that a single YSZ layer cannot satisfy alone.
Solution Approach 2:
The coating system applies different material properties at different locations and depths. The outer portion of the coating has optimized infrared interaction properties, while the inner portion focuses on thermal barrier performance. This local differentiation of material qualities allows the coating to simultaneously handle infrared radiation and thermal heat transfer effectively.
2Temperature
If coating thickness is increased to improve thermal protection, then thermal insulation improves, but thermal stress and coating delamination risk increase
Solution Approach 1:
The patent modifies the coating structure by introducing intermediate layers with graded properties between the substrate and the thick outer coating layer. These intermediate layers have thermal expansion coefficients and mechanical properties that gradually transition between the substrate and the outer coating, reducing thermal stress concentration and preventing delamination even when the total coating thickness is increased for better thermal protection.
Solution Approach 2:
The thick coating is segmented into multiple thinner layers with different functions and properties. Instead of applying one thick coating layer, the system divides it into several layers including primer layers, intermediate layers, and top coats, each optimized for specific requirements. This segmentation reduces the stress burden on any single layer and improves overall coating reliability.
3Object-affected harmful factors
If multiple coating layers are added to protect against infrared radiation, then infrared protection improves, but coating complexity increases
Solution Approach 1:
The coating system is designed so that each layer performs multiple functions. For example, the outer layer not only interacts with infrared radiation but also provides erosion resistance and oxidation protection. The intermediate layers serve both as stress buffers and as additional thermal barrier layers. This multi-functionality reduces the need for separate specialized layers, thereby limiting the increase in complexity while maintaining comprehensive protection.
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 significantly reduces substrate temperature by up to 150°F compared to standard thermal barrier coatings, minimizing incipient melting and warpage, and can be tailored for specific thermal protection needs by varying the thickness and composition of its layers.
Implementation Method 1
The outer portion may be a low emissivity portion (low-E) that reflects incident IR away from the component
Implementation Method 2
or a high emissivity portion (high-E) that absorbs incident radiation and dissipates the absorbed incident radiation as heat
Implementation Method 3
The performance portion comprises at least one layer that includes microspheres
Implementation Method 4
The compliance portion comprises at least one layer of high temperature material that has a coefficient of thermal expansion (CTE) intermediate the performance layer and the substrate
Data Source
AI summary
A coating system that includes a plurality of portions, each portion comprising one or more layers. The coating system includes an outer portion, which is an infrared radiation (IR) interaction portion, that dissipates incident (IR). Underlying this outer portion is a performance portion. The performance portion comprises at least one layer that includes microspheres. Between the substrate and performance portion is a compliance portion. The compliance portion comprises at least one layer of high temperature material that has a coefficient of thermal expansion (CTE) intermediate the performance layer and the substrate. The compliance portion thus reduces any high temperature thermal mismatch between the substrate and the performance portion.