Fatigue crack growth in Ti-6Al-4V EBMed samples: impact of powder recycling

Within the powder bed fusion electron beam (PBF-EB) category, due to the high cost of material feedstock, the unused powder can be reused in subsequent production cycles, thereby reducing the costs associated with powder production. However, since the impact of recycling processes on the metallurgical and mechanical properties has not been fully investigated in the scientific literature, this study aimed to analyze fatigue crack growth propagation by examining three types of compact tension (CT) specimens. The specimens were manufactured using the Electron Beam Melting (EBM) process with three different batches of Ti-6Al-4V powder particles: virgin, recycled five times, and recycled more than 100 times. The results reveal that the oxygen content increases with each cycle, indicating the potential effects of recycling. Furthermore, from a mechanical testing perspective, the obtained results did not indicate any significant effects of powder reuse on the investigated CT samples, as the obtained curves exhibited a high degree of similarity. This can be attributed to the presence of numerous internal defects, such as porosity and Lack of Fusion, and thus, it is believed that the effect of powder recycling has been overshadowed by the influence of these defects.