Analyse quantitative de la concentration d'hydrogène jouant un rôle 
dans la fragilisation par l'hydrogène des aciers haute résistance
Hydrogen embrittlement of high strength, aircraft-grade steel alloys was studied by nuclear reaction analysis (NRA) using 15N ions. We have developped an experimental setup to be able to determine hydrogen depth profiles with the sample held at a cryogenic temperature. The hydrogen concentration was seen to decrease during the NRA measurements. The interaction between the ion beam and the steel sample induced a desorption that followed second order kinetics, suggesting that the formation of molecular hydrogen was the limiting process of the desorption. We have studied the effect on absorbed hydrogen of a thermal bake after a layer of Cd had been deposited onto the steel samples by electroplating. The hydrogen concentration near the surface (less than 0.12 micrometers) was clearly higher for the plated sample than the non plated one. Deeper in the sample no difference could be observed between the samples. Annealing decreases the amount of hydrogen in steel. A 16 hour delay between the electroplating and the annealing did not affect the amount of hydrogen in retained in the steel. In spite of the higher hydrogen content of the non-annealed samples seen in the NRA measurements, none of the observed samples was embrittled. This implies that with the NRA technique and the experimental set-up established in our lab, we should be able to easily measure the hydrogen depth profile in samples that do exhibit hydrogen embrittlement.
Hydrogen Hydrogen embrittlement Nuclear reaction analysis High strength steel Hydrogen desorption