The role of bioxidant corrodents on the lifetime behaviour of FeCrAl(RE) alloys

Studies have been undertaken to investigate the oxidation behaviour of industrial iron-chromium-aluminium alloys with reactive element additions in exhaust contaminant simulating atmospheres at temperatures between 1100 and 1300 C. The model atmospheres have been air + 3.2 vol.% H2O (moist air), N-2 + 5 vol.% H-2 + 630 vppm H2O, N-2 + 5000 vppm NO, simulated exhaust gas, simulated combustion gas, air + 0.3 vol.% SO2 and air + 50 vppm HCl. The temperature was cycled between room temperature and test temperature with periods of 20 h or 100 h. The test results were compared to those gained in parallel tests performed in laboratory air. The nitrogen-containing environments act as a shielding atmosphere and the retardation of oxide growth appears to be dependent on the partial oxygen pressures. Earlier breakaway is induced by moist air and by additions of 0.3% SO2 to air and completely different oxide growth behaviour is found in air + 500 ppm HCl. This can be attributed to the formation of volatile specimens, which deteriorate the alumina scale.