Surface modifications of AISI 420 stainless steel by low energy Yttrium ions

Dipartimento di Matematica e Fisica “E. De Giorgi”, Università del Salento - Lecce, Via Provinciale Lecce-Monteroni, 73100 Lecce – Italy, Tel. +39 0832 297495, Fax. +39 0832 297482, vincenzo.nassisi@le.infn.it

^* Corresponding author: vincenzo.nassisi@unisalento.it

Published online: 9 January 2018

Abstract

In this work, we study surface modifications of AISI 420 stainless steel specimens in order to improve their surface properties. Oxidation resistance and surface micro-hardness were analyzed. Using an ion beam delivered by a Laser Ion Source (LIS) coupled to an electrostatic accelerator, we performed implantation of low energy yttrium ions on the samples. The ions experienced an acceleration passing through a gap whose ends had a potential difference of 60 kV. The gap was placed immediately before the samples surface. The LIS produced high ions fluxes per laser pulse, up to 3x10¹¹ ions/cm², resulting in a total implanted flux of 7x10¹⁵ ions/cm². The samples were characterized before and after ion implantation using two analytical techniques. They were also thermally treated to investigate the oxide scale. The crystal phases were identified by an X-ray diffractometer, while the micro-hardness was assayed using the scratch test and a profilometer. The first analysis was applied to blank, implanted and thermally treated sample surface, while the latter was applied only to blank and implanted sample surfaces. We found a slight increase in the hardness values and an increase to oxygen resistance. The implantation technique we used has the advantages, with respect to conventional methods, to modify the samples at low temperature avoiding stray diffusion of ions inside the substrate bulk.