| Abstract: | The isothermal oxidation behaviour of a single crystal Ni-base superalloy (CMSX2) between 900 and 1300°C in air at atmospheric pressure or in pure static oxygen at 0.2 atm. pressure has been studied for test durations between 8 to 1000 hours. The extremely low oxidation rate did not permit accurate measurements of oxidation kinetics. However, oxide scale examinations by means of SEM, EDS, TEM, X-ray diffraction, RHEED, SIMS and metallography allowed to discuss the oxidation mechanisms of the studied alloy. At temperature higher than 1100°C, the very good oxidation resistance is due to the growth of a thin Al2O3 scale while at lower temperature it may be attributed to the growth of a subscale of a complex oxide (Cr, Ti, Al) (Ti, Ta)O4 possessing a rutile structure. The effect of chemical homogeneity was studied in comparing the behaviour of as-cast and homogenized specimens. |
