Collaborative Research: Additive Manufacturing of Crack-Free Tungsten Using Ultrashort Pulsed Lasers

Additive manufacturing (AM) with lasers is a method of creating 3-dimensional structures by fusing layers of material together. However, building with tungsten using traditional continuous lasers often leads to cracking because these lasers generate too much heat over a large area. Initial experiments show that using ultrashort pulsed lasers, which release energy in tiny bursts, can prevent cracking by limiting the heat to a very small area. While this approach looks promising, more research is needed to fully understand how it works. This project will conduct experiments and develop strategies to eliminate cracking when working with high-temperature materials. These improvements are vital for advancing technologies in aerospace, automotive, energy, and healthcare industries. In addition, the team plans to create educational programs and outreach activities to train future engineers, equipping them with the skills needed to lead in advanced manufacturing. The overarching goal of this project is to achieve crack-free additive manufacturing (AM) of tungsten using a femtosecond (FS) laser. The high ductile-to-brittle transition temperature of tungsten makes the metal vulnerable to cracking, particularly in AM processes. Based on the hypothesis that the thermal response to FS laser can induce tungsten conditions favorable for crack-free AM, the team will conduct a combination of experiments and physics-based simulations to identify such conditions for crack-free AM. This project will clarify the key factors, such as laser scanning velocity, layer thickness, and hatching spacing, focusing on the thermal and mass transfer processes induced by nonequilibrium photonic sources, and identify the optimal FS laser processing conditions of laser powder-bed fusion for achieving desirable thermal and mechanical profiles. The findings will enable the team to develop a mechanistic understanding of the thermal, metallurgical, and mechanical responses of tungsten to the localized heating of FS laser that can eliminate tungsten cracking during fusion-based processing. The project activities also provide learning opportunities to diverse populations. 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.