Multi-laser powder bed fusion using 808nm sources

Abstract

Laser Powder Bed Fusion (LPBF) is a disruptive manufacturing technique widely used in aerospace, automotive, and energy industries, enabling the creation of intricate structures from various metallic alloys with minimal waste. However, LPBF systems face limitations in processing efficiency, scalability, and thermal control. The main constraint is single-fibre laser productivity, hindering large-scale adoption due to galvo-scanning method limitations. Multi-laser integration shows potential but presents challenges in design and control complexity. Innovations are sought to effectively incorporate multiple lasers while ensuring efficiency and scalability. LPBF systems use high-power fibre lasers at 1064 nm wavelength, but their low material-specific absorption efficiency (<60%) demands high laser power, resulting in challenges in processing high-performance alloys with limited weldability and high crack susceptibility. Enhanced thermal management with in-situ control and slower cooling rates are necessary to mitigate these issues, although they increase production costs and time. On the other hand, low-power diode lasers are emerging as a promising alternative. They are compact, energy-efficient, and durable and emit shorter wavelengths ranging from 450 nm to 3300 nm, making them suitable for various industrial processes. Research efforts are currently focused on developing Diode Area Melting (DAM) systems where multiple diode lasers selectively melt powder beds, offering a high-resolution and energy-efficient solution. However, challenges still exist in beam quality, power output, and system design. Integrating multi-fibre coupled diode lasers as a 2D array in LPBF can offer significant advantages, including improved productivity, enhanced material absorption, and reduced energy consumption. The ability to individually control each laser allows for customized intensity distributions, enabling the fabrication of complex parts. Further research is needed to optimize system design, increase power output, and explore scalability to larger write areas suitable for production environments. The use of fibre-coupled diode laser and optical systems can potentially create efficient and scalable LPBF systems that can enhance the microstructure of final parts. This, in turn, can significantly improve the mechanical properties at an industrial level without incurring excessive costs or time investment. This research investigates the influence of laser wavelength on the efficiency and scalability of the Powder Bed Fusion (PBF) process using a 2D array head comprising a scalable, low-power (4.5 W) 808 nm fibre-coupled diode laser. The individual control of multiple short wavelengths (808 nm) diode lasers enhances absorption and processing efficiency, enabling the fabrication of intricate parts with better thermal control. The research delves into how beam profiles, laser power, scanning speed, and wavelength affect microstructure, mechanical properties, and melt pool morphology when manufacturing three-dimensional Ti6Al4V parts. The study reveals that low-power diode lasers generate energy densities comparable to traditional selective laser melting due to shorter laser wavelengths, increasing metallic powder absorption, and enhancing processing efficiency. Moreover, the investigation highlights the impact of laser wavelength on keyhole formation, melt pool characteristics, and microstructural evolution. The 2D array laser head produces parts with mechanical properties akin to those manufactured using selective laser melting systems, indicating the potential of this technique to optimize PBF manufacturing efficiency. These findings are valuable to researchers and industry professionals seeking to enhance the quality, scalability, and cost-effectiveness of the PBF process.