On the Recycling of Water Atomized Powder and the Effects on Properties of L-PBF Processed 4130 Low-Alloy Steel

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.

Texturing and Phase Evolution in Ti-6Al-4V: Effect of Electron Beam Melting Process, Powder Re-Using, and HIP Treatment

The research demonstrates microstructural changes and development of specific texture in Ti-6Al-4V specimens produced by electron beam melting (EBM) under different conditions. The effect of two factors, namely, raw material (powder) recycling and hot isostatic pressing (HIP), on the EBM produced samples structure and properties, has been explored. The as-printed and treated samples were investigated using electron backscattered diffraction (EBSD) analysis. Modification of mechanical properties after the EBM and HIP are explained by the EBSD data on microstructural phenomena and phase transformations. The work is devoted to assessing the possibility of reusing the residual titanium alloy powder for the manufacture of titanium components by the combination of EBM and HIP methods.

Selective Laser Sintering (SLS), a New Chapter in the Production of Solid Oral Forms (SOFs) by 3D Printing

3D printing is a new emerging technology in the pharmaceutical manufacturing landscape. Its potential advantages for personalized medicine have been widely explored and commented on in the literature over recent years. More recently, the selective laser sintering (SLS) technique has been investigated for oral drug-delivery applications. Thus, this article reviews the work that has been conducted on SLS 3D printing for the preparation of solid oral forms (SOFs) from 2017 to 2020 and discusses the opportunities and challenges for this state-of-the-art technology in precision medicine. Overall, the 14 research articles reviewed report the use of SLS printers equipped with a blue diode laser (445–450 nm). The review highlights that the printability of pharmaceutical materials, although an important aspect for understanding the sintering process has only been properly explored in one article. The modulation of the porosity of printed materials appears to be the most interesting outcome of this technology for pharmaceutical applications. Generally, SLS shows great potential to improve compliance within fragile populations. The inclusion of “Quality by Design” tools in studies could facilitate the deployment of SLS in clinical practice, particularly where Good Manufacturing Practices (GMPs) for 3D-printing processes do not currently exist. Nevertheless, drug stability and powder recycling remain particularly challenging in SLS. These hurdles could be overcome by collaboration between pharmaceutical industries and compounding pharmacies.

XPS and SEM characterization for powder recycling within 3d printing process

In recent years, recycling the powder leftover within the additive manufacturing process has been attractive for both research, development and industry production. Powder recycling can significantly enhance the sustainability of the manufacturing process, reduce the cost and avoid producing metallic waste as a potential environmental hazard. The first step in reusing the recycled powders in the 3D printing process is to characterize the microstructure and surface quality of the powder for oxidation and impurity analysis. Here, scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) have been used for the morphology and surface composition analysis of the 316L powders within the Aconity 3D printer. A new powder collection strategy has been introduced to collect powders from different locations in the powder bed: from the top most and surface of the parts and powder bed after the print terminated, from between the printed parts at different heights. The XPS measurements revealed that oxidation is a common in all the powders compared to virgin powder and more oxidation was detected from the powders collected on the very top of the leftover powder and from surface of the bed. The size of the particles does not change much but larger particles remained at the topmost surface. This finding would help in designing a protocol for collecting the recycled powder from the powder bed and it is suggested to follow a a procedure of collecting powders from the different sections of the powder bed in order to avoid mixing the most and least affected particles.

Topological, Mechanical and Biological Properties of Ti6Al4V Scaffolds for Bone Tissue Regeneration Fabricated with Reused Powders via Electron Beam Melting

Cellularized scaffold is emerging as the preferred solution for tissue regeneration and restoration of damaged functionalities. However, the high cost of preclinical studies creates a gap between investigation and the device market for the biomedical industry. In this work, bone-tailored scaffolds based on the Ti6Al4V alloy manufactured by electron beam melting (EBM) technology with reused powder were investigated, aiming to overcome issues connected to the high cost of preclinical studies. Two different elementary unit cell scaffold geometries, namely diamond (DO) and rhombic dodecahedron (RD), were adopted, while surface functionalization was performed by coating scaffolds with single layers of polycaprolactone (PCL) or with mixture of polycaprolactone and 20 wt.% hydroxyapatite (PCL/HA). The mechanical and biological performances of the produced scaffolds were investigated, and the results were compared to software simulation and experimental evidence available in literature. Good mechanical properties and a favorable environment for cell growth were obtained for all combinations of scaffold geometry and surface functionalization. In conclusion, powder recycling provides a viable practice for the biomedical industry to strongly reduce preclinical costs without altering biomechanical performance.