Turbine Components with Negative CTE Structures
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Solution Overview
Problem
Gas turbine engine components face challenges in high-temperature environments due to hot corrosion and oxidation, requiring materials with improved creep and stress rupture resistance, which existing superalloys do not adequately address, especially considering the high costs and low yields of single-crystal microstructure production.
Innovation Solution
Incorporating a negative Coefficient of Thermal Expansion (CTE) structure, monolithically formed with the metallic wall of turbine components, such as a repeating two-dimensional array of hourglass-shaped cells, to offset thermal expansion and provide enhanced creep resistance, potentially reducing the need for expensive single-crystal materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If single-crystal microstructure is used to improve creep resistance, then high-temperature creep resistance is improved, but manufacturing cost increases and manufacturing yield decreases
Solution Approach 1:
The invention changes the microstructural parameters from single-crystal to directionally solidified columnar grain structure, which maintains high-temperature creep resistance while significantly improving manufacturability and reducing production costs. This parameter change allows the use of conventional casting processes rather than expensive single-crystal casting techniques.
Solution Approach 2:
The invention employs a composite microstructure consisting of directionally solidified columnar grains with controlled orientation, combining the benefits of anisotropic strength properties with improved manufacturability. The composite nature of the microstructure allows optimization of creep resistance along critical stress directions while facilitating easier manufacturing compared to single-crystal structures.
2Strength
If directionally solidified or single-crystal microstructure is used to improve creep resistance, then high-temperature performance is improved, but manufacturing complexity increases
Solution Approach 1:
The invention simplifies the manufacturing process by changing from complex single-crystal growth processes to directionally solidified columnar grain structures that can be produced using conventional casting techniques with controlled cooling rates, thereby reducing manufacturing complexity while maintaining adequate creep resistance.
Solution Approach 2:
The invention applies local quality control by directing grain growth in specific orientations (columnar grains) along the primary stress directions, providing localized strength enhancement where needed most while using simpler manufacturing processes compared to universal single-crystal structures.
3Strength
If conventional superalloys are used to meet mechanical property requirements, then creep rupture strength is achieved, but resistance to hot corrosion and oxidation is insufficient
Solution Approach 1:
The invention uses composite microstructures combining directionally solidified columnar grains with controlled chemical composition, creating a material system that simultaneously achieves creep rupture strength and enhanced resistance to hot corrosion and oxidation through synergistic microstructural and compositional design.
Solution Approach 2:
The invention applies local quality by optimizing chemical composition and microstructure in specific regions of the component, particularly at grain boundaries and surfaces, to enhance resistance to hot corrosion and oxidation while maintaining bulk creep rupture strength properties.
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 negative CTE structure enhances creep rupture and fatigue strengths, providing a safety margin against component failure and potentially allowing lesser alloys to perform in critical engine applications, while also serving as a thermal management system for improved heat transfer and cooling efficiency.
Implementation Method 1
a negative CTE structure rigidly attached to one of the surfaces... the negative CTE structure is monolithically formed with the metallic wall
Implementation Method 2
directing a beam from a directed energy source to fuse the powder in a pattern corresponding to a cross-sectional layer of the component
Data Source
Figure 1
Figure 2~4
Figure 5
AI summary
A turbine component (10) includes: a metallic wall (24, 26, 228) having opposed interior and exterior surfaces, the wall configured for directing a combustion gas stream in a gas turbine engine; and a metallic negative CTE structure (48, 50, 54) rigidly attached to one of the surfaces.