Laminated Single-Crystal Superalloys for Complex Shape Manufacturing
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Solution Overview
Problem
The manufacturing of single crystal superalloys for aerospace applications is challenging due to the sensitivity of casting processes, high costs, and limitations in controlling orientations, leading to mis-orientations, lower yields, and high scrap rates, especially in creating complex internal shapes using traditional investment casting methods.
Innovation Solution
A laminated object manufacturing (LOM) approach using field-assisted sintering (FAST) to combine and recombine layers of single crystal and polycrystalline materials with controlled orientations and compositions, eliminating the need for grain selectors and enabling the formation of complex geometries and properties not achievable through conventional casting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If investment casting is used to cast single crystal components, then the manufacturing process can produce single crystal structures, but the process is sensitive and requires careful control over melting and solidification, leading to higher costs and lower yields
Solution Approach 1:
The single crystal component is divided into multiple layers that can be manufactured separately and then assembled. Each layer can be cast independently with controlled crystal orientation, and the layers are joined using friction stir welding to create the final multi-layer single crystal component. This segmentation reduces the sensitivity of the casting process and improves manufacturing ease.
2Shape
If traditional investment casting is used for complicated internal shapes, then the desired geometries can be achieved, but complicated casting arrangements are required resulting in high scrap rates
Solution Approach 1:
The component with complex internal shapes is segmented into multiple layers that can be manufactured using additive manufacturing techniques. This allows complex geometries to be built layer-by-layer with material only where needed, eliminating the need for complicated casting arrangements and significantly reducing scrap rates associated with traditional investment casting.
Solution Approach 2:
The manufacturing approach transitions from conventional 3D casting to layer-by-layer additive manufacturing. By building the component in the vertical dimension through sequential layer deposition, complex internal shapes can be achieved without the limitations of traditional casting methods, reducing material waste and scrap rates.
3Stability of the object's composition
If conventional casting processes are used, then single crystal components can be produced, but certain orientations cannot be explicitly controlled, leading to mis-orientations and lower yields
Solution Approach 1:
The component is divided into multiple layers, each of which can be cast with a specific crystal orientation. By controlling the orientation of each individual layer during the casting process and then assembling them with precise orientation control through friction stir welding, the final component achieves explicit orientation control that cannot be achieved with conventional single-step casting.
4Stability of the object's composition
If grain selectors are used in casting processes, then single crystal growth can be controlled, but the cost increases and inherent limitations remain
Solution Approach 1:
The manufacturing process is segmented into multiple casting steps, each producing a layer without requiring expensive grain selectors. By controlling crystal orientation through the casting parameters of each layer and assembling them with precise orientation control, single crystal growth is achieved without the need for costly grain selector equipment.
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 method simplifies the fabrication of aerospace alloys, reduces scrap rates, and allows for tailored mechanical properties by varying crystal orientations and compositions, enhancing the strength and functionality of components while maintaining or exceeding conventional casting standards.
Implementation Method 1
A prior art method having the features of the preamble to claim 1 is disclosed in US 5,902,687
Implementation Method 2
The process involves heating and cooling the layered structure to combine layers
Data Source
Figure 1~3
Figure 2~4B
Figure 5~6
AI summary
An embodiment of a method includes fabricating a first single crystal boule (24;124A) having a uniform composition and grain orientation. The first uniform single crystal boule (24;124A) is divided into a first plurality of layered shapes (20A;120A;220A;320A). The shapes of the first plurality (20A;120A;220A;320A) are stacked with at least a second plurality of layered shapes (20B;120B;220B;320B) along a first axis. The second plurality of layered shapes (20B;120B;220B;320B) have at least one physical aspect differing from at least one corresponding physical aspect of the first plurality of layered shapes (20A;120A;220A;320A). The first plurality of layered shapes (20A;120A;220A;320A) and at least the second plurality of layered shapes (20B;120B;220B;320B) are joined via a field assisted sintering technique (FAST) to form a bulk component.