Effect of a high hafnium content on the high temperature oxidation of chromium-rich cast alloys. Part 2: Isothermal oxidation and scale spallation of Fe-based alloys

Author(s): Patrice Berthod, Elodie Conrath

The chromium-rich iron-based alloys, the oxidation behaviour at heating of which was characterized in the first part of this work, were subjected to characterization of their average isothermal oxidation rate as well as of their resistance against oxide spallation during cooling. The isothermalmass gains at 1000°C and 1100°C during 46 hours and the exploitation of the cooling parts of the thermogravimetry curves led to observations about the effect of the high contents in hafniumof these other oxidation parameters. It appeared that the effect of these high amounts in hafniumon the isothermal oxidation was not the same depending on the stage temperature. Concerning their influence on the resistance to scale spallation at cooling from1000 or 1100°C, the good behaviours of the ternary alloys was not deteriorated by the presence of this element in too high quantities to keep maybe the good behaviour generally observed at lower Hf contents. To summarize, so high Hf contents, which allow developing reinforcing HfC carbides, did not significantly threaten the oxidation behaviour of the alloys, neither during the isothermal oxidation, nor during cooling and probably thermal cycling.

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