Coaxial Dual-Laser Heating for Melt Pool Cooling Control
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Solution Overview
Problem
Direct Metal Laser Melting (DMLM) processes in gas turbine engine component fabrication and repair face challenges with high temperature gradients and cooling rates that lead to internal part stress and cracking, particularly in nickel base superalloys, due to the complexity of coordinating two independent laser systems.
Innovation Solution
A method involving a first laser beam to form a melt pool and a coaxially aligned second laser beam that is laterally offset to control the cooling rate, using a reflector and beam combiner to heat without melting, allowing for dynamic control of the cooling zone and reduced stress in the part.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a second laser is used in proximity to the melt pool to alter the cooling rate, then the cooling rate can be controlled to reduce stress and cracking, but the system complexity and cost increase due to requiring two independent sets of optics and scanners
Solution Approach 1:
The patent combines two laser beams into a single coaxial path using beam combiner optics. The first laser beam creates the melt pool while the second laser beam, traveling through the same optical path, controls the cooling rate. This merging eliminates the need for separate optics and scanner systems, reducing system complexity while maintaining the ability to control cooling rates and prevent cracking
Solution Approach 2:
The shared optical system serves multiple functions: it directs both the melting laser and the cooling control laser to the same location on the powder bed. The single scanner system simultaneously controls both laser beams, making the system multi-functional rather than requiring dedicated systems for each laser, thereby reducing complexity
2Reliability
If custom inductive heaters are used to reach required temperatures for crack-free fabrication, then the cooling rate can be controlled, but the system complexity and cost increase
Solution Approach 1:
The patent replaces the mechanical/custom inductive heating system with an optical-based solution. Instead of using physical inductive heaters to control temperature and cooling rates, the invention uses a second laser beam delivered through the existing optical system to provide the necessary thermal control. This substitution eliminates custom heating hardware while achieving the same crack-prevention objective
3Manufacturing precision
If two independent laser systems are used to control cooling rate, then precise cooling control is achieved, but the coordination difficulty and system cost increase
Solution Approach 1:
The patent merges the optical paths of two laser systems into a single coaxial beam path using beam combiner optics. Both lasers are directed through the same scanner system, which synchronizes their positioning. This combining maintains precise cooling rate control capability while eliminating the coordination difficulties and costs associated with managing two completely independent laser systems
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 reduces stress and cracking in parts by allowing precise control of cooling rates, enabling crack-free fabrication and improved mechanical properties, while simplifying the system configuration and reducing costs by eliminating the need for custom optics and scanners.
Implementation Method 1
directing a first laser beam on the powder bed to form a melt pool
Implementation Method 2
the second laser beam heats but does not melt powder within the focus spot
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
A method of controlling the cooling rate of a melt pool of a powder bed includes directing a first laser beam (5) on the powder bed to form a melt pool; coaxially aligning a second laser beam (6) with the first laser beam (5); and laterally offsetting a focus spot (26) of the second laser beam (6) with respect to the melt pool, wherein the second laser beam (6) heats but does not melt powder within the focus spot.