CAREER: Advancing Laser Powder Bed Fusion with Non-Spherical Powder

This Faculty Early Career Development (CAREER) award will support research that intends to address the limitations of current additive manufacturing (AM) practices that primarily use expensive and energy-intensive spherical powdered materials. The cold mechanically driven method employs attrition milling with a reciprocating cutter, achieving precise powder size distribution, leading to the production of pore-free metal powders with reduced energy input. The project aims to: (1) enhance powder-spreading dynamics through multimodal particles and a hybrid powder dispenser, and (2) improve laser-powder interaction and microstructure control. If successful, the project outcomes may expand material choices, making production more cost-effective and sustainable across various AM processes such as binder jetting and laser/electron beam powder bed fusion. The project provides research opportunities to a diverse pool of undergraduate students, including those from underrepresented groups and veterans. Through hands-on research experiences, outreach activities, and the creation of video animations, the project will engage underrepresented communities and high school students in the field of metal additive manufacturing. The CAREER research project aims to address three fundamental research problems: (1) Non-spherical powder characteristics, such as morphology and size, impact powder-powder interactions, potentially leading to lower packing density and non-uniform powder beds. This will be addressed by developing a deposition mechanism using multimodal powder sizes and an innovative non-contact electrostatic powder spreader. (2) Laser-powder interaction is affected by characteristics such as shape, morphology, and size distribution. The shift in the stable/unstable keyhole mode due to the shadowing effect of non-spherical powder at higher laser scan speeds will influence the process map, and mechanical interlocking of particles. Comprehensive investigations into laser-powder interactions will be undertaken, using in-situ observations such as synchrotron X-ray imaging and multi-physics modeling. This approach aims to unravel the underlying physics and formulate processing strategies to effectively address anticipated defects. (3) Locally reduced cooling rates from the shadowing effect influence solidification, impacting microstructure and resultant mechanical properties. This will be addressed by adjusting process parameters and applying post-heat treatments, such as hot isostatic pressing, which is expected to achieve equiaxed grain structures for improved strength and ductility comparable to wrought alloys. The research outcomes have the potential to bridge the gap between fundamental understanding and practical applications, fostering a sustainable future for additive manufacturing. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.