Abstract
The microstructure and mechanical properties of a 4130-grade steel processed by L-PBF using a feedstock of low-cost water atomized powder have been investigated considering the effects of powder recycling. Chemical analysis of the recycled powder showed a constant amount of alloying elements with a slight reduction in oxygen content. The as-built microstructure was mainly composed of a martensitic structure separated by a high fraction of low-angle grain boundaries, suggesting the application of a direct tempering treatment starting from the as-built condition as a cost-effective post-process thermal treatment rather than the conventional quench and tempering treatment. Moreover, the degree of anisotropy generated by L-PBF in as-built specimens could be reduced after performing either the direct tempering or the quench and tempering treatments. The possible degradation of powder properties on the steel performance was also investigated. After various powder recycling events, no significant deterioration in tensile properties was measured, indicating that the water atomized powder could be a sustainable feedstock candidate for L-PBF.
Highlights
The laser powder bed fusion (L-PBF) process offers several advantages to the additive manufactured (AM) metallic components, such as the ability to fabricate complex-shape objects with outstanding properties
The current study aims to investigate the microstructure and tensile properties of a 4130 low-alloy steel fabricated by L-PBF, starting from a low-cost water atomization (WA) powder, and evaluating the effects of several recycling events on the achievable steel properties
It is observed that the C content of the recycled WA powder remained substantially constant, while a minor reduction in the amount of O content was detected when increasing the number of recycling runs, considering that the O content in the virgin powder was 0.29%
Summary
The laser powder bed fusion (L-PBF) process offers several advantages to the additive manufactured (AM) metallic components, such as the ability to fabricate complex-shape objects with outstanding properties. It should be noted that investigations on recycling have been carried out on GA powder so far, while no information is available from the open literature on the behavior of recycled WA powder during L-PBF In this context, the current study aims to investigate the microstructure and tensile properties of a 4130 low-alloy steel fabricated by L-PBF, starting from a low-cost WA powder, and evaluating the effects of several recycling events on the achievable steel properties. The current study aims to investigate the microstructure and tensile properties of a 4130 low-alloy steel fabricated by L-PBF, starting from a low-cost WA powder, and evaluating the effects of several recycling events on the achievable steel properties Another aspect of this investigation is the proposal of a single-step treatment consisting of a Materials 2022, 15, x FOR PEER REVIdEiWrect tempering of the as-built specimens, as a cost-effective alternative to the conventio3noafl quench and tempering treatment. Selected specimens were investigated after Q & T or just after tempering, starting from as-built condition (AB & T)
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