Flux effect on the ion-beam nitriding of austenitic stainless-steel AISI 304L

Abstract

The effect of flux and Ar pretreatment during ion-beam nitriding of austenitic stainless steel is investigated. The ion energy and temperature were 1.2keV and 400°C, respectively, the ion current densities were 0.5, 0.67, and 0.83mAcm−2. The nitrogen distribution profiles were measured using nuclear reaction analysis. The obtained nitrogen distribution profiles were analyzed by the means of the nitrided layer thickness evolution due to sputtering and diffusion and the model of trapping–detrapping. Both approaches could fit well the experimental results, however, different diffusion coefficients have to be assumed for each current density. In addition, the diffusion coefficients are higher for higher current densities. On the other hand, it is shown that the pretreatment with Ar-ion beam at nitriding temperatures produces only a thermal effect without any other influence on the following nitrogen diffusion. The results are discussed in relation with surface and temperature effects and atomic transport mechanisms.