Understanding the role of beam shape in laser materials processing, considering thermal field evolution

• Applicant: Lova Chechik, Ph.D.
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548990686

This project aims to improve understanding of the effect of beam shape on the thermal field during laser materials processing and its effect on the final component. New beam shapes will be designed and tested specifically for laser powder bed fusion (PBF-LB/M) using a combination of computational and experimental techniques with process monitoring used for process quantification. Two aspects of PBF-LB/M will be targeted, process productivity and microstructural control. By controlling the shape of the molten pool, both the hatch distance and the layer thickness can be increased, reducing the build time required for bulk sections in PBF-LB/M – leading to substantial cost savings. By controlling the thermal gradient directly behind the molten pool, both the scale and the morphology of the microstructure can be influenced, which can be used to tailor the mechanical properties. The main objectives from the computational side are to improve the accuracy of low-fidelity simulation and to validate results when using complex beam shapes. Optimisation techniques will determine which low-fidelity simulations need to be run; new beam profiles will be designed with a targeted melt pool area increase of 50%. Next, these newly designed beam shapes must be experimentally tested to demonstrate direct applicability to laser materials processing. A spatial light modulator to create the desired beam shapes; a key objective is to create accurate beam shapes with feature size of ≤20 µm. To demonstrate the broad applicability of this work, experiments are performed on materials with varying thermal properties as thermal fields will develop differently in different materials. These experiments will be extended to perform tests with a single layer of metal powder, as a replica of PBF-LB/M. Process monitoring (both high speed and thermal) will be used to observe the process dynamics and to enhance understanding of the underlying mechanisms. The productivity increase using the new beam shapes can be quantified in comparison to the current state of the art (Gaussian and ring/spot beam shapes) whilst aiming to retain ≥99.7 % component density. The microstructure of components will be analysed, demonstrating the possibility of microstructural control in PBF-LB/M by changing beam shape.

• DFG Programme: Research Grants
• Co-Investigator: Professor Dr.-Ing. Michael Schmidt