Uma revisão crítica sobre a reutilização de pó metálico na manufatura aditiva

Abstract

The present review work addresses the feasibility of metallic powder reuse in additive manufacturing (AM), exploring various crucial aspects influencing the process. It was motivated by a lack of similar studies, seeking to examine and consolidate the impact of multiple printing cycles on various powder aspects. Additionally, the study aimed to investigate the results of the printing sequences on the mechanical properties of the manufactured parts. Powder reuse significantly influences particle morphology and size distribution. It was identified that these changes in morphology and particle size distribution generally occur with an increase in the number of cycles, directly affecting the quality of the material deposited during additive manufacturing. It was also observed that reuse can compromise powder packing and flow, influencing the ease of layer formation and homogeneity of the deposited layer, resulting in potential process failures. These changes are not directly caused by process factors but by powder characteristics such as roughness, oxidation content, morphology, and size distribution, as well as more specific factors like magnetic phases present in the powder. Defects also occur in AM-obtained parts, such as increased density and size of porosities, compositional variations mainly due to oxidation, and an increase in defects such as lack of material fusion and voids due to uneven powder distribution. The spattering phenomenon, in which significant portions of the powder are ejected from the metal bed, also significantly alters the powder that will be reused and generates defects in the parts manufactured in the current print, such as voids and layer discontinuities. All these issues could lead to a significant deterioration in local and global mechanical properties of parts manufactured from reused material that has not been rigorously studied, controlled, and treated. This treatment involves stages of sieving between cycles to remove agglomerates and spatters, thus mitigating negative effects caused by these phenomena resulting from the decline in powder quality. Finally, this review emphasizes the complexity of metallic powder reuse in additive manufacturing, highlighting the importance of carefully monitoring powder characteristics between each print cycle to ensure better results. Understanding the impact on the properties of manufactured parts is crucial for establishing viable recycling limits, balancing economic efficiency with the quality of the final product. Regarding expectations for advances in research in this area, studies of different alloys and other additive manufacturing processes are included, investigating properties beyond just mechanical ones. In addition, an advanced study of the effect of reuse on microstructure and formed phases and the impact on the quality of the surface finish of manufactured parts is anticipated.