The oxidation of industrial FeCrMo steel

Fe-9Cr-1Mo steel is used as a corrosion resistant alloy in pressurised wate r reactors. The high steam temperature and pressure inside the reactors res ult in erosion corrosion. The steel's hardness and resistance to various fo rms of corrosion are determined by the composition of the oxide layer forme d on the alloy at elevated temperatures. Samples were taken from pieces of pipe removed after failure and have an operation history in excess of 20 ye ars in a local power generation facility. The samples were oxidised in UHV for 1000 L between 157 degrees C and 758 degrees C. AES (Auger electron spe ctroscopy) and XPS (X-ray photo electron spectroscopy) depth profiles of th e oxide layer were obtained at room temperature, At high oxidation temperat ures the layer forms a duplex structure consisting of Fe oxide at the gas/o xide interface and Cr oxide at the oxide/metal interface, The ratio between these oxides is temperature dependent. Below 400 degrees C the oxide layer consists mainly of Fe2O3 and a small amount of Cr2O3 at the metal/oxide in terface. Between 400 degrees C and 600 degrees C the oxide layer consists o f a mixture of FeO, Fe2O3 and Cr2O3 and above 600 degrees C the layer consi sts mainly of Cr2O3 No influence of Mo or Ni on the oxidation process was m easurable with the techniques used. (C) 2000 Elsevier Science Ltd. All righ ts reserved.