A new method for assessing the recyclability of powders within Powder Bed Fusion process

Abstract

Recycling metallic powders used in the additive manufacturing (AM) process is essential for reducing the process cost, manufacturing time, energy consumption, and metallic waste. In this paper, the focus is on pore formation in recycled powder particles of stainless steel 316L during the selective laser melting process. We have introduced the concept of optimizing the powder bed's printing area in order to see the extent of the affected powders during the 3D-printing process. X-ray Computed Tomography (XCT) is used to characterize the pores inside the particles. The results from image processing of the tomography (rendered in 3D format) indicate a broader pore size distribution and a higher pore density in recycled powders compared to their virgin counterparts. To elucidate on this, the Electron Dispersion spectroscopy (EDX) analysis and Synchrotron-based Hard X-ray Photoelectron Spectroscopy (HAXPES) were performed to reveal the chemical composition distribution across the pore area and bulk of the recycled powder particles. Higher concentrations of Fe, Cr, and Ni were recorded on the interior wall of the pore in recycled particles and higher Mn, S and Si concentrations were recorded in the outer layer around the pore area and on the surface of the recycled particle. The pore formation in recycled powder is attributed to out-diffusion of Mn, S and Si to the outer surface as a result of the incident laser heat during the AM process due to higher electron affinity of such metallic elements to oxygenation. HAXPES analysis shows a higher MnO concentration around the pore area which impedes the in-diffusion of other elements into the bulk and thereby helps to creates a void. The inside wall of the pore area (dendrites), has a higher concentration of Fe and Cr oxide. We believe the higher pore density in recycled powders is due, at least in part to composition redistribution, promoted by laser heat during the AM process. Nanoindentation analyses on both virgin and recycled powder particles shows a lower hardness and higher effective modulus in the recycled powder particles attributed to the higher porosity in recycled powders.

Dimensional Accuracy of Dental Casting Patterns Fabricated Using Consumer 3D Printers

“…In contrast, a grid pattern, which could be attributed to laser scanning, was visible on the cervical and ceiling surfaces of DW ( Figure 2 c). Moreover, on the marginal surface of MA and DW, laminated layers were observed, but no such layers were found on NB and DP ( Figure 2 d) [ 23 ].…”

Experiment and Numerical Simulation for the Compressive Buckling Behavior of Double-Sided Laser-Welded Al–Li Alloy Aircraft Fuselage Panel

“…The fabricated panel was inspected using non-destructive testing approaches such as visual inspection, dye penetrant inspection, and X-ray detection [ 29 ]. All the welds passed the dye penetrant inspection and X-ray detection testing according to the international standard [ 30 ].…”

“…All the welds passed the dye penetrant inspection and X-ray detection testing according to the international standard [30]. During The fabricated panel was inspected using non-destructive testing approaches such as visual inspection, dye penetrant inspection, and X-ray detection [29]. All the welds passed the dye penetrant inspection and X-ray detection testing according to the international standard [30].…”

Sustainability Assessment for Manufacturing Operations

“…At the process stage, optimized technical changes are required to reduce energy and resource usage, hazardous wastes, workplace hazards, etc., to enhance product life by controlling process-induced surface integrity. For example, recycling of metal powder in metal additive manufacturing processes can optimize the resource consumption in three-dimensional (3D) printing technology [36,37]. Sustainable manufacturing can be accomplished by more energy-efficient technologies.…”