Preparation and characterization of mechanically alloyed, yttria containing steel powder for additive manufacturing of dispersion strengthened steels: Semester project – A. Cavaliere

Abstract

Oxide-dispersion-strengthened (ODS) steel is a material that is being studied for its potential in high-temperature and high-irradiation applications, such as nuclear fusion reactors or IV generation fission reactors. Its properties derive from the presence of nano-dispersed oxide particles that act as a barrier against the movement of dislocations, hence reducing susceptibility to creep, and as sinks for irradiation-induced defects, thus reducing the stress in the metal matrix itself. In this study, a powder for additive manufacturing is produced with mechanical alloying (MA) in a planetary ball mill; seven sets of powders are produced in this study, each with a different set of milling parameters, so that the best-suited specimen for the chosen manufacturing process may be selected. The powder is studied with a Scanning Electron Microscope (SEM) imaging and optical microscopy in order to characterize the formation of the oxides with an acceptable level of detail and to determine the size distribution of the powder particles. The results show the choice of acetic acid and ethanol as process control agents for dry grinding of the powders does not improve the characteristics of the end product to a significant extent. An increase in the grinding time seems more effective in increasing the yield and reducing the average size of the particles to an acceptable range, but it may result in a compromise in terms of the powder’s flowability.