An in-situ ToF-LEIS and AES study of near-surface modifications of the composition of EUROFER97 induced by thermal annealing

Abstract

Surface segregation and diffusion of W, Ta, Cr, O and S after thermal annealing of EUROFER97 were studied in-situ. The sample was prepared by polishing, annealing up to 300°C and 3 keV Ar sputtering. In-situ measurements with time-of-flight low energy ion scattering using 8 keV Ne ions and Auger electron spectroscopy were carried out close to room temperature after each annealing, in sequence, to 425°C, 675°C, 400°C, 675°C, 900°C, and 925°C. Surface segregation/diffusion of chromium and tungsten and/or tantalum can be observed in the ion scattering spectra. The segregation of sulfur was clearly observed in Auger electron spectroscopy. The energy converted time-of-flight low-energy ion scattering spectrum after the first annealing to 675°C was compared to Monte-Carlo simulations using the TRBS code. The most compatible simulation indicates a layer enriched in W + Ta of 1 ± 0.3 nm featuring 0.0276 combined relative concentration of tungsten and tantalum to total metal content which is considerably higher than the bulk value of 0.0042.

Keywords

• EUROFER97
• ToF-LEIS
• AES
• In-situ
• Annealing
• Segregation