The effects of temperature and oxygen pressure on the initial oxidation of stainless steel 441
The oxidation behavior of the stainless steel 441 in the initial 2 h was investigated gravimetrically at 600 °C–950 °C under various oxygen pressures. The morphology, composition and the growth stress of the scale on the oxidized alloy were analyzed by SEM/EDS and Raman spectra. It was found that the performances of the scale degraded with the temperature and oxygen pressure increasing. The oxidation of stainless steel 441 presented a multi-stages behavior. It was suggested that the first chemical reaction determining stage was the nonselective oxidation of steel surface. The following stage in pure oxygen ambient was the formation of chromium-oxide-mainly-containing layer. Kinetic mechanism of second stage oxidation changed from diffusion determining step (600–800 °C) to interface... chemical reaction (900–950 °C) due to the decline of the protection of the oxides layer. Only linear rate law was obeyed in the lower oxygen pressure atmospheres at 800 and 900 °C within the initial 2 h.