About
Xibo Qin
Postgraduate Researcher
DCU
Xibo Qin is a PhD researcher at I-Form, based at Dublin City University (DCU), focusing on the Laser Powder Bed Fusion (L-PBF) manufacturing of nitinol. He completed his undergraduate degree in Materials Science and Engineering at Swansea University, followed by a Master’s degree in Advanced Materials Science at Imperial College London, where his research focused on forging microtexture in titanium alloys. His current research explores the optimisation of L-PBF process parameters, the sustainability of the printing process, and the effects of powder oxidation during the build.
Technical Summary
Powder utilisation in Laser Powder Bed Fusion (L-PBF) is often limited to approximately 50%, primarily due to oxide formation during processing, which can significantly degrade the fatigue strength and toughness of printed components. From both sustainability and economic perspectives, improving powder reuse throughout the process is essential. This research project was designed to quantify the extent of oxidation in nitinol powder during L-PBF and evaluate the practicality of powder recycling.
The study simulates the recycling process by heating nitinol powder samples in controlled argon environments with varying oxygen concentrations, exposure times, and temperatures. A Box-Behnken design of experiments was implemented to systematically investigate the influence of these parameters on the powder's behaviour. During the heating process, powder characterisation involved the use of pyrometry, optical spectral response measurements, and visual imaging. Post-treatment characterisation was conducted using a combination of analytical techniques, including Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDX), microhardness and nanohardness testing, X-ray Photoelectron Spectroscopy (XPS), and Optical Emission Spectroscopy (OES) to accurately assess changes in oxygen content.
The results indicate that powder particle size affects the optical energy reflected during processing. A correlation has been established between processing temperature and the degree of oxide formation. Furthermore, the conditions typical of L-PBF have been shown to significantly alter the chemical composition and physical properties of the nitinol powder particles.