Resumen: 

The reusing of metal powders, along with debinding and sintering, is a critical process in additive
manufacturing using Binder Jetting (BJ) technology. The main purpose of this work is to analyze
and optimize the BJ additive manufacturing process for stainless steels, focusing on the
fundamental mechanisms of powder degradation and sintering kinetics. Within the framework of
the 3D-MetJet project, this research addresses the industrial need for high-quality components by
evaluating how powder reuse and thermal processing parameters affect final part performance.

The results obtained during this first year demonstrate that while powder morphology remains
stable after multiple reuse cycles, high-resolution analysis with Transmission Electron Microscopy
(TEM) reveals a significant thickening and increased irregularity of the surface oxide layer.
Regarding the sintering stage, a «step-sintering» methodology using X-ray Computed Tomography
(XCT) successfully tracked the densification process, showing an increase in relative density from
85.9% to 95.5% in three different stages of the sintering process and a progressive spheroidization
of internal pores. Furthermore, microstructural characterization identified a critical thermal
threshold at 1331 °C, where the formation of a liquid phase triggers a transition from equiaxed to
elongated grain structures. These findings establish a direct correlation between raw material
integrity, sintering protocols, and the final mechanical properties, providing a robust scientific
basis for the industrialization of Binder Jetting technology.