Study of the high-temperature oxidation behaviour of Ti and Ti4Nb with SNMS using tracers

Abstract

The effect of niobium and water on the high‐temperature oxidation behaviour of pure titanium and Ti4Nb (at.%) was studied. An oxidation apparatus was designed that allowed not only the performance of two‐stage oxidation experiments using synthetic air isotopically enriched in 18O2 and 15N2 but also the control of humidity using either H2 16O or H2 18O. Oxidation experiments were performed in dry and humid atmospheres at 800 °C. The oxide scales formed were analysed by secondary neutral mass spectrometry. The results obtained show that niobium significantly reduced the oxidation rate of titanium and also suppressed the influence of water. Moreover, the presence of niobium stabilizes the formation of a nitride layer formed at the scale/metal interface. In humid atmospheres water is the main oxygen source for the oxidation process. This phenomenon has to be taken into consideration when interpreting two‐stage oxidation experiments and discussing oxidation mechanisms. Copyright © 2000 John Wiley & Sons, Ltd.

Nitrogen quantification and tracking during high temperature oxidation in air of titanium using 15N isotopic labelling

“…The Figure 9 presents the in-depth analyses by SIMS for the three samples over 40 x 40 µm 2 . The profiles of the signals of 14 N in S1 and 15 N in S2 are very similar. They display a peak, which coincides with the decrease of the signal of 16 O, which points out that the nitrogen is located at the oxide/metal interface.…”

“…For the sample S3, the distribution of the isotope 14 N shows an intense and broad peak for a sputtering time of about 5500 seconds, and a weak bump at about 3200 seconds. The profile obtained for the isotope 15 N shows similar features, but the intensity of the main peak is quite lower, which agrees with the short exposition time of sample S3 to 15 Nlabelled air compared to regular air.…”

“…The profile obtained for the isotope 15 N shows similar features, but the intensity of the main peak is quite lower, which agrees with the short exposition time of sample S3 to 15 Nlabelled air compared to regular air. It is important to notice that the location of the both maximum pics of 14 N and 15 N in S3 sample are the same despite the fact that each isotope was introduced at different times within the sample. The peak of nitrogen concentration is correlated with a decrease in the oxygen signal, but the nitrogen seems to spread deeper than the oxygen.…”

“…Nuclear reaction analysis (NRA) is further used for this purpose. the 14 N(d,1) 12 C and 15 N(d,0) 13 C reactions which have been used to determine the amount of 14 N, respectively 15 N isotopes inserted in the oxidized samples. Dashed vertical lines correspond to the energy of the different emitted particles when the reactions occur at the very surface of the sample (without any energy loss i.e.…”

“…Carpene et al [13] studied laser nitridation of titanium under nitrogen atmosphere with 15 N isotope. Göbel et al [14] exploited isotopic tracers to study the oxidation of titanium and Ti-Nb alloy at 800°C under dry and humid air and used secondary neutral mass spectrometry to find the distribution of nitrogen and oxygen as a function of depth.…”