Initial oxidation stage of yttrium-implanted pure iron at 700 °C by in situ high temperature X-ray diffraction

Oxidation study, at 700 °C and under controlled atmosphere (oxygen partial pressure: 0.04 Pa) for 24 h, of unimplanted or yttrium implanted pure iron specimens was carried out using in situ X-ray diffraction to observe the yttrium implantation effect. In situ X-ray diffraction analyses performed on unimplanted pure iron clearly show the formation of FeO (wustite) and Fe₃O₄ (magnetite) compounds at the beginning of the oxidation test whereas the formation of Fe₂O₃ (hematite) is only detected after 1h30 of oxidation. In situ X-ray diffraction analyses performed with the same experimental conditions on yttrium implanted pure iron show the presence of two Mayn yttrium-iron mixed oxides (i.e. FeYO₃ and Fe₂YO₄) in combination with wustite, magnetite and hematite structures. The presence of the Fe₂YO₄ compound is important because several authors have reported its anticorrosion properties at high temperature. X-ray diffraction results also show that the formation of FeYO₃ and Fe₂YO₄ is Maynly reinforced at the gas-oxide interface which suggests an outward yttrium diffusion through the oxide layer from implanted pure iron.