Oxide Distribution in Prealloyed Water Atomized Steel Powder

Paper in proceeding, 2010

A method for evaluation of the oxygen distribution in both the surface and the interior of water-atomized powder was developed. Pre-alloyed powder with 3wt.% Cr and 0.5 wt.% Mo was chosen as the model material. Surface chemical composition with regard to composition, morphology, size and distribution of surface oxides was studied by means of surface analytical techniques (XPS, Auger, SEM and EDX). The analysis revealed that the powder particles are covered by a homogeneous (~6 nm thick) Fe-oxide layer and some spherical particulate features with size up to 200 nm that were complex Fe-Cr-Mn-Si-oxides, surface coverage of which is <10%. About 45% of total oxygen content is in the form of easily-reducible iron oxide layer. Remaining oxygen is linked to the surface stable oxides and internal complex oxides. Study of the internal oxides using EDX Smart-Maps tool reveals presence of inclusions below 1μm in size and rich in Cr and Mn.