Austenite modification of AISI 316L SS by pulsed nitrogen ion beams generated in dense plasma focus discharges

Abstract

We present the results of surface modification of AISI 316L stainless steelby surface irradiation with high energy, pulsed nitrogen ion beams generatedwith 0.8 kJ Dense Plasma Focus. The surface characterization was doneusing GAXRD, Auger electrons spectroscopy, TEM and optical microscopy.After the irradiation, we found a modification of a 1 μm thick surface layer,on which a gradual lattice expansion of the austenite with the number ofirradiation pulses, i.e. with the total nitrogen ion fluence, was observed.In addition, on the »40 nm close to the surface layer, a disordered latticestructure had been observed through TEM analysis. Those results canbe explained in terms of the extreme thermal effect induced on the surfacethrough the fast high energy release during the pulsed ion interaction withthe steel surface, followed by an also rapid cooling down process which limitsthe nitrogen diffusion to the bulk.