Surface Oxides on Gas and Water Atomized Steel Powders

Paper in proceeding, 2014

The amount of oxides, their composition and spatial distribution within a 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, high-resolution scanning electron microscopy (HR SEM) coupled with energy dispersive X-ray analysis (EDX) and modern thermoanalytical techniques. Surface oxide state for a number of a water and gas atomised steel powders, alloyed with elements with high sensitivity to oxygen as Cr and Mn, is summarised. Dependence of surface products composition on the alloying elements content and atomisation method is described. In all cases powder particles are covered by heterogeneous oxide composed of particulate features of stable oxides (Cr-Mn-Si) and homogeneous iron surface oxide layer in between.