[T1] Powder Production

[15C-T1-21] Quantitative Characterization of the Chemistry of Oxides Formed on the Surface of Water-Atomized Steel Particles According to Their Production Stages

*G. Laramée¹, S. Gélinas¹, P. Plamondon², G. L'Espérance², C. Blais¹ (1.Université Laval, 2.Polytechnique Montréal, Canada)

Keywords:Surface oxides, Water atomization, Transmission electron microscope

Water-atomized (WA) steel powders are inevitably oxidized due to the chemical reaction between molten metal and water vapor. Minimization of surface oxides is essential to ensure formation of strong metallic bonds during sintering. However, the efficiency of H₂-annealing is strongly dependant on oxide chemistry, which is rarely made of pure/stoichiometric species. The objective of this work was to perform an in-depth characterization of the oxides found on WA steel particles to understand their behaviour during H₂-annealing. It investigates the relationship between the nominal chemical composition of pre-alloyed steels (Cr, Mn, Si), the chemical composition of the surface oxides and their modification due to H₂-annealing. Experiments were performed on individual particles using state-of-the-art Ga-Focussed Ion Beam, scanning and transmission electron microscopies coupled with X-ray energy dispersive and electron energy loss spectrometries. Characterization at different stages of production provided insights into the dynamics of oxides reduction as a function of powder chemistry.