HIGH TEMPERATURE BEHAVIOUR OF LOW ENERGY HIGH FLUX NITRIDED Ni AND Ni20Cr SUBSTRATES

International audience; Nitridation at low energy- high flux implantation-diffusion has been performed on pure Ni and Ni20Cr substrates in order to study their high temperature oxidation behaviour at 700 and 800° C in synthetic air. The nitridation treatment has led to significant sputtering on pure Ni, but no implanted nitrogen has been detected. On the contrary, the Ni20Cr substrates are able to incorporate nitrogen, with less sputtered surfaces. Porosity is anyhow found on both substrates after the nitridation treatment. No particular difference is found to occur on the oxidation kinetics of Ni specimens but on their scales morphology. On the contrary, in Ni20Cr specimens, oxidation is enhanced mainly upon the first exposure times owing to trapping of chromium by the implanted nitrogen. Furthermore, the expanded austenite γN layer formed on the nitrided Ni20Cr samples is stable up to 700°C for 24 h, after which evolution towards the nitride precipitation occurs.