Diode Laser Fiber Array for Controlled Solidification in Additive Manufacturing
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Solution Overview
Problem
Current Direct Metal Laser Melting (DMLM) systems face challenges with rapid cooling rates that lead to cracking of alloys and difficulties in achieving desirable grain morphology, and the process is time-consuming due to scanning requirements.
Innovation Solution
A diode laser fiber array is used to simultaneously melt powder layers with controlled thermal gradients and solidification velocities, allowing for rapid melting times and precise control over cooling rates to achieve columnar, equiaxed, or directionally solidified microstructures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a single laser beam is used to scan the powder layer, then the equipment complexity is low, but the processing time is excessively long (70-100 seconds per layer)
Solution Approach 1:
The single laser beam is segmented into multiple independent laser beams arranged in an array configuration. Each laser beam can independently scan and melt powder in different regions of the build plate simultaneously, thereby increasing the overall processing speed without requiring a single complex high-power laser system.
Solution Approach 2:
Multiple low-power laser beams are merged into a coordinated array system that operates simultaneously. The combined effect of multiple lasers scanning different areas at the same time achieves the productivity of a high-power single laser while using simpler, more manageable laser components.
2Productivity
If rapid cooling is used after laser melting, then the processing efficiency is high, but cracking occurs in certain alloys
Solution Approach 1:
The laser array enables different regions of the powder bed to be melted and cooled at different rates simultaneously. By controlling the power and scanning patterns of individual laser beams, the system can create localized thermal gradients that promote desirable grain structures in critical areas while maintaining faster cooling in non-critical areas, thereby preventing cracks in crack-sensitive alloys.
Solution Approach 2:
The system performs preliminary heating of the powder bed and controlled cooling before final solidification. By pre-heating the substrate and controlling the cooling rate through the laser array configuration, the material undergoes a more gradual thermal transition that reduces thermal stress and prevents cracking while still maintaining high processing efficiency.
3Manufacturing precision
If conventional casting technologies are used to form airfoils, then the manufacturing process is simple, but the required complex geometries cannot be achieved
Solution Approach 1:
The laser array system provides dynamic control over the melting and solidification process, allowing the formation of complex three-dimensional geometries layer by layer. The independent control of each laser beam enables the creation of varying cross-sections, internal channels, and surface features that are impossible to achieve with conventional static casting molds, while maintaining additive manufacturing efficiency.
4Productivity
If fast scanning is used to reduce processing time, then the productivity increases, but the cooling rate becomes too rapid causing cracking
Solution Approach 1:
The laser array system acts as an intermediary between the heat source and the powder bed, distributing thermal energy across multiple zones. This intermediate distribution allows for controlled cooling rates even at high scanning speeds, as the thermal gradient can be managed across multiple laser zones rather than concentrated in a single scanning beam, preventing crack formation while maintaining high productivity.
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 significantly reduces processing time, prevents cracking, and enables the formation of desired grain structures, improving mechanical properties and surface finish of components like airfoils for gas turbine engines.
Implementation Method 1
a first, second, and third portion of the layer are simultaneously melted by a diode laser fiber array
Implementation Method 2
a first, second, and third portion of the layer are simultaneously solidified... to achieve columnar, equiaxed, or directionally solidified microstructures
Data Source
Figure 1A
Figure 1B
Figure 1C
AI summary
A method of method of forming or repairing a superalloy article having a columnar or equiaxed or directionally solidified or amorphous or single crystal microstructure includes emitting a plurality of laser beams (120) from selected fibers (109) of a diode laser fiber (101) array corresponding to a pattern of a layer of the article onto a powder bed (130) of the superalloy to form a melt pool; and controlling a temperature gradient and a solidification velocity (V) of the melt pool to form the columnar or single crystal microstructure.