Abstract
The surface of gas atomized ferritic powder, Fe–25Cr, was studied by ESCA and Auger spectro- scopy. During atomization reaction products are formed on the surface of the powder. Due to the very low oxygen potential in the atomizer only oxides of the strong oxide forming elements Cr, Mn, and Si are formed during cooling of the metal particles. These oxides are precipitated as particles on the surface of the metal powder. At low temperature, when the sample is exposed in air, Fe oxide is formed between the oxide islands. The average thickness of the Cr and Mn oxide is estimated to be about 15 nm. The thin Fe oxide is found to be about 3 nm. From the surface analyses, distribution of the metal particle size, and measurements of the total oxygen content it was found that 60% of the total amount of oxygen is bound in the surface oxide. Carbides and nitrides are also formed on the surface. It is suggested that these products occur as carbonitride. These particles are coarser than the oxide particles but cover the surface to a much lower extent than the oxides. Chromium is the dominating metal element in the carbonitride. PM/0361
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