Evidence for Chromium Evaporation Influencing the Oxidation of 304L: The Effect of Temperature and Flow Rate

摘要: The influence of temperature and flow rate on the oxidation 304L steel in O2/H2O mixtures was investigated. Polished samples were isothermally exposed to dry O2 O2+40% H2O at 500–800°C 0.02–13 cm/sec velocity, for 168 hr. analyzed by gravimetry, XRD, ESEM/EDX, AES depth profiling. water vapor/oxygen is strongly influenced chromium evaporation. loss tends convert protective chromia-rich oxide initially formed into a poorly protective, iron-rich oxide. depends rate; high rates result an early breakdown most rapid occurs highest (800°C) gas (4000 ml/min=13 cm/sec). close grain boundaries metal more while other parts, surfaces suffer breakaway corrosion. consists Cr-rich 50–200-nm thick M2O3 film, parts experiencing corrosion form 10–30-μm Fe-rich M2O3/M3O4 scale. results show that evaporation key process affecting resistance chromia formers marginal mixtures.