The preparation, characterization and corrosion behaviour of ion-implanted and ceramic-coated AISI 321 steel samples

Ion Beam Techniques were used to modify near-surface layers of austenitic stainless steel AISI 321 samples in order to improve their corrosion resistance. Mg-, Y- (implantation energy: 40 keV) and Al-implantation (implantation energy: 40, 60, 80 and 200 keV), as well as Dynamic Ion Mixing (DIM) (SiC deposition and mixing with 160 keV Xe ⁺ ions) and Sputtering (Si₃N₄ deposition with 15 keV Ar⁺ ions) were applied for this purpose. The characterization of the samples was performed using Nuclear Reaction Analysis (NRA) and ⁴He-Rutherford Backscattering Spectroscopy (RBS). The corrosion behaviour was investigated in 1N H₂SO₄ using cyclovoltammetry and potentiodynamic polarization. The values of the critical and passivation current density as well as of the corrosion, passivation and repassivation potentials, showed an increase of the corrosion resistance of the treated steel samples. This improvement is connected with the properties of the modified region (thickness, adhesion, formation of oxide films). The surface morphology and microstructure of the specimens before and after the corrosion experiments were investigated by Scanning Electron Microscopy (SEM).