Comparison between Virgin and Recycled 316L SS and AlSi10Mg Powders Used for Laser Powder Bed Fusion Additive Manufacturing

Abstract

In this study, the comparison of properties between fresh (virgin) and used (recycled) 316L stainless steel (316L SS) and AlSi10Mg powders for the laser powder bed fusion additive manufacturing (L-PBF AM) process has been investigated in detail. Scanning electron microscopy (SEM), electron-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) techniques are used to determine and evaluate the evolution of morphology, particle size distribution (PSD), circularity, chemical composition, and phase (crystal structure) in the virgin and recycled powders of both materials. The results indicate that both recycled powders increase the average particle sizes and shift the PSD to higher values, compared with their virgin powders. The recycled 316L SS powder particles largely retain their spherical and near-spherical morphologies, whereas more irregularly shaped morphologies are observed for the recycled AlSi10Mg counterpart. The average circularity of recycled 316L SS powder only reduces by ~2%, but decreases ~17% for the recycled AlSi10Mg powder. EDX analysis confirms that both recycled powders retain their alloy-specific chemical compositions, but with increased oxygen content. XRD spectra peak analysis suggests that there are no phase change and no presence of any undesired precipitates in both recycled powders. Based on qualitative comparative analysis between the current results and from various available literature, the reuse of both recycled powders is acceptable up to 30 times, but re-evaluation through physical and chemical characterizations of the powders is advised, if they are to be subjected for further reuse.

Abnormal interfacial bonding mechanisms of multi-material additive-manufactured tungsten–stainless steel sandwich structure

“…As shown in figure 5(d), a typical XRD pattern of the single γ-austenite FCC structure was observed at the SS part, similar to that of LPBF-printed SS reported in a previous study [47]. Four major peaks in the diffraction pattern (figure 5(c)) of the LPBF-printed W region was the same as the original pure BCC W powder [48].…”

Thermal Plasma Spheroidization and Characterization of Stainless Steel Powders Using Direct Current Plasma Technology

“…The tests show that the mean circularity value of the produced particles is always higher than 0.8 (see Table 6), indicating an extensive spheroidization of the powders whatever the raw powder processed (where as spheroidization is meant the percentage of particles whose circularity is over 0.8). According to the literature [24,25], it is recommended that the circularity factor required for powders to be considered for further reuse in AM would be as close to 1 as possible, or at least ≥0.7. Indeed, it is worth noting that, for example, for the A3 test, a spheroidization degree of 85% means that more than 85% of the particles can be used for AM application.…”

Insights into the assessment of spreadability of stainless steel powders in additive manufacturing

“…The PSD became narrower since finer particles pass through the gap and spread while larger ones is pushed away with the blade from the build plate. Therefore, a narrower PSD with increased number of large particles and decreased number of fine particles is achieved with recycling powders in PBF method [131].On the other hand, in some articles such as Yusuf et al it is suggested that the PSD of recycled 316L SS in SLM method is not noticeably changed compare to the virgin batch [132]. This may be due to the reason that the gap size is large enough to spread the coarse particles along with the finer ones.…”