Fabrication of Stainless Steel/Alumina Composite Powders by Spray Granulation and Plasma Spheroidization

This work presents a new approach for the fabrication of 316L/Al2O3 composites, based on a combination of spray granulation, radio frequency (RF) plasma spheroidization and spark plasma sintering (SPS). Initially, a suspension containing 316L and alumina powders is formulated by precisely adjusting the pH and selecting an appropriate dispersant, thereby ensuring homogeneous dispersion of the constituents. The spray granulation process then produces granules with controlled size and morphology. RF plasma spheroidization, carried out using a TekSphero-40 system, is investigated by varying parameters such as the power, gas flow rates, injection position and feed rate, in order to optimize the formation of spherical and dense particles. The analysis reveals a marked sensitivity to heat transfer from the plasma to the particles, with a tendency for fine particles to segregate, which underscores the necessity for precise control of the processing conditions. Finally, SPS densification, performed under a constant pressure and a rigorously controlled thermal cycle, yields composites with excellent density and hardness characteristics. This study thus demonstrates that the proposed hybrid process offers an optimal synergy between a uniform distribution of alumina and a controlled microstructure, opening up promising avenues for the design of high-performance composite materials for demanding applications.