IV - Rôle de la microstructure sur l’entrée de l’hydrogène cathodique dans l’Alliage 600

Conséquences sur les propriétés mécaniques

Influence of the microstructure on cathodic hydrogen diffusion in alloy 600, consequences on mechanical properties

Abstract

The role of hydrogen on the intergranular stress-corrosion cracking of alloy 600 in primary water is suspected. The purpose of this study is to characterize the role of the microstructure of the alloy on hydrogen diffusion and the consequences on the mechanical properties. The main experimental observations can be summarized as follows:

- Deuterium diffusion profiles obtained with Secondary Ion Mass Spectroscopy after cathodic charging (5 mn 293 K, 15 mn 415 K) are in agreement with those calculated assuming a fickian diffusion process.

- Hydrogen diffusion (absorption or desorption) is slower in the mill-annealed microstructure than in the recrystallized microstructure (1 hour 1243 K) presumably because of enhanced hydrogen trapping on carbide precipitates.

- Hydrogen charged tensile samples exhibit a significant ductility loss with an intergranular fracture mode. The hydrogen embrittlement sensitivity of the recrystallized microstructure is higher than those of the mill-annealed alloy in agreement with the role of the microstructure on hydrogen diffusion.