Oxidation kinetics and mechanisms of Ni-base alloys in pressurised water reactor primary conditions: Influence of subsurface defects

► Ni-base alloy uniform corrosion in primary medium of Pressurised Water Reactor. ► Influence of alloy subsurface defects created by ion implantation on oxide layer. ► Defects in the alloy modify the crystallinity and the nucleation rate of the oxides. ► These modifications are linked to the change of oxidation kinetic curves. Oxidation of Alloy 690 in PWR primary water conditions has been investigated, considering particularly the role played by subsurface structural defects. To simulate a defective surface state, Xe implantation has been set up on samples. Corrosion experiments were thereafter performed in a corrosion loop simulating the PWR medium with durations between 24 h and 1000 h. Microstructural observations and NRA measurements underlined the role played by defects on the crystallinity of the continuous oxide spinel layer, on the nucleation of Cr 2O 3 nodules and on the oxidation rate. The higher defects concentration seemed to modify the oxygen diffusion in the oxide scale.