Oxydation a l'air de deux alliages refractaires (nicral d et hastelloy x) a 900 et 1100° c

Abstract

The oxidation in air of two refractory alloys (Nicral D and Hastelloy X) has been studied at 900 and 1100° C, by means of recording thermobalances and microscopic cross section examination. At 900 °C, the surface oxidation rates of the two alloys are quite similar, but at 1100° C the alloy Nicral D oxidizes faster than the alloy Hastelloy X. On the other hand, after heating at 1100° C for 150 hours, Nicral D shows both intergranular oxidation and a small amount of internal oxidation, whereas Hastelloy X is especially subject to internal oxidation. In addition, two descaling methods were compared: an electrolytic method, in a sodium hydroxide- sodium carbonate bath, and a chemical method using a sodium nitrate-sodium peroxide bath; the latter appears suitable only for Hastelloy X.