Methodology for Evaluating the Oxide Distribution in Water Atomized Steel Powder

Paper in proceedings, 2009

A method for characterizing the oxide composition and 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 sensitive analytical techniques (high resolution electron microscopy in combination with EDX-analysis, X-ray photoelectron spectroscopy and Auger electron spectroscopy) were used in order to study the type, composition, morphology and distribution of oxide products. The analysis revealed that the powder particles were mainly 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. Using EDX Smart-Maps tool, inclusions below 1μm in size and rich in Cr and Mn were observed rarely in the interior of the powder particles. By means of the method, the distribution of surface bound and bulk oxygen is realised.