Study on the oxidation behaviour of Fe, Cr and Ni in O2+ ion implanted SUS304 stainless steel by in situ SR–XPS and ex situ scanning tunnelling microscope

Abstract

The oxidation behaviour of SUS304 stainless steel implanted with 3 keV O2+ ions has been investigated by in situ synchrotron radiation X-ray photoelectron spectrocsopy (SR–XPS). For comparison, the same experiments were carried out for pure Fe, Cr and Ni metals. The oxide films on stainless steel and pure metals have also been observed by scanning tunnelling microscope (STM). It was found that the oxidized species of Cr and Ni in SUS304 were Cr2O3 and NiO, respectively. For Fe, on the other hand, the oxidized product in SUS304 changed from FeO to Fe2O3 with increase in the doses of O2+. The growth rates of the oxide of Fe and Cr on SUS304 were faster than those on the respective pure metals, while the growth rate of the oxide of Ni on SUS304 was lower than that on pure Ni. NiO was not formed on SUS304 until Fe2O3 appeared, which suggests that Fe2O3 has a special effect on the formation of NiO. The behaviour of Fe, Cr, Ni in the oxidation of SUS304 is discussed on the basis of the results of STM and SR–XPS.