Surface Oxides on Gas and Water Atomized Steel Powders

Paper in proceeding, 2013

The amount of oxides, their composition and spatial distribution within a metal particle determine the usefulness and subsequent processing requirements of a powder. The present work summarizes possibilities of qualitative and quantitative analysis of powder surface chemistry by a variety of methods, starting from surface-sensitive chemical analyses by X-ray photoelectron spectroscopy (XPS), Auger spectroscopy and high-resolution scanning electron microscopy (HR SEM) coupled with energy dispersive X-ray analysis (EDX). Surface oxide characteristics for water and gas atomised steel powder grades, alloyed with elements with high sensitivity to oxygen as Cr and Mn, are summarised. The dependence of surface products composition on the alloying elements content and atomisation method is described. In all cases, the metal particles are covered by heterogeneous oxide composed of particulate features of stable oxides (Cr-Mn-Si) and homogeneous iron surface oxide layer in between.