Effects of Ce, Mo and Si ion implantation on the passive layer composition and high-temperature oxidation behaviour of AISI 304 stainless-steel studied by soft x-ray absorption spectroscopy

The influence of Ce, Mo and Si ion implantation on the chemical properties of AISI 304 stainless-steel passive and oxide layers was studied by means of soft x-ray absorption spectroscopy (XAS), Applying this technique at the transition metal 2p absorption thresholds, the composition and chemical state of the passive layer were determined. A surface Cr enrichment is observed for the ion-implanted samples in comparison with non-implanted samples, which can be associated with better corrosion behaviour. To investigate the effects of ion implantation on the high-temperature oxidation behaviour of AISI 304 stainless-steel, the oxide layer formed after an isothermal oxidation at 1173 K for 32 h was also investigated. The XAS data show mainly the presence of Cr and Mn oxides in the surface region of all samples, The Cr/Fe ratio-a parameter that can be associated with the protective character of the oxide scale-is higher for the Si- and Ce-implanted samples than for the as-received sample. The Mo-implanted sample has the lowest Cr/Fe ratio, suggesting a poor oxidation resistance at high temperatures in this case. Copyright (C) 2000 John Wiley & Sons, Ltd.