Use of oxygen isotope to study the transport mechanism during high temperature oxide scale growth

The examination of high temperature (HT) oxide scale growth mechanisms was performed using secondary ion mass spectrometry (SIMS) and secondary neutral mass spectrometry (SIMS), in conjunction with O-16(2)/O-18(2) HT oxidation experiments. Cr2O3, NiO, ZrO2 and Al2O3 were studied because they constitute excellent representative thermally grown oxide scales: they grow by cationic diffusion (Cr2O3, NiO), anionic diffusion (ZrO2) or mixed anionic-cationic diffusion (Al2O3). The oxidation tests were performed first in O-16(2) and subsequently in O-18(2) at several temperatures (600-1000degreesC for NiO, 600degreesC for ZrO2, 1000degreesC for Cr2O3 and 1100degreesC for Al2O3). The oxygen isotope distribution observed by SIMS and SNMS profiles are discussed and related with the HT oxidation mechanisms proposed in the literature.