Abstract

Study of some characteristics describing the oxidation of a {m,m�?�?�?�?�?�?�?�?}-based {30Cr, 1C, 15Ta} containing alloy during heating up to high temperature and the oxide scales behavior during post-{isothermal stage} cooling. part 2: {m, m�?�?�?�?�?�?�?�?}={Co, Fe}

Author(s): Kevin Duretz, Ga�?�?�?�?�?�?�?«l Pierson, Thierry Schweitzer, Elodie Conrath, Patrice Berthod

An alloy based on cobalt and iron in equal parts, rich in chromium and containing a dense TaC network in itsmicrostructure was tested in oxidation at high temperature in dry synthetic air. The thermogravimetry tests were performed at 1000, 1100 and 1200°C during 40 hours. The mass gain files were plotted versus temperature and exploited to specify the oxidation start during heating and spallation start during cooling temperatures as well as the successive parts of mass gain achieved during heating and during the isothermal stage. The mass gain kinetic at 1000°C is quite parabolic and the rate rather low. Themass gain curves obtained at 1100 and 1200°C are much more perturbed, with presence of successive high jumps and a tendency to liner oxidation at the end of the isothermal stage. The oxidation start temperature of this CoFe-based alloywas generally lower than for the NiCobased alloys studied in the first part, and the overall oxidation during heating a little faster. The isothermalmass gain was itself a little higher but the scale spallation behaviour of this CoFe-based alloy during cooling was similar to the NiCo-based alloy one, as is to say not good.