Nuclear microprobe study of stress-oxidation of nickel

In order ot study the stress oxidation, a specific device has been designed to perform mechanical loadings under controlled temperature and oxygen pressure. Time-dependent strain-stress curves may be recorded according to the usual modes: creep, fatigue and fatigue-creep. A set of two sorption pumps allows to alternate oxygen-16 and oxygen-18. Oxygen-18 diffusion profiles have been measured by SIMS (Secondary Ion Mass Spectroscopy) and by nuclear microprobe, by means of the 18 O(p, α) 15 N nuclear reaction to characterize selected areas. For the purpose of further investigations on nickel-based alloys, initial experiments have been performed on pure nickel to obtain knowledge of the fundamental properties of nickel. Because of complex relationships between mechanical behaviour, microstructure modifications and oxygen diffusion, both polycrystalline and monocrystalline samples have been investigated.