Roles of implantation parameters on the formation of expanded austenite

High-current ion implantation of nitrogen into austenitic stainless steel (AISI 316Ti) at temperatures about 400°C results in the formation of a surface layer, called expanded austenite. A tensor of nitrogen ion energies (1.2, 2.0 and 2.8 keV), ion fluxes (0.2 and 1.0 mA/cm2) and times (2, 10 and 40 min.) has been selected to investigate the roles of the implantation parameters: ion energy, current density and treatment time. In addition, a temperature series has been performed over the range from 280°C to 480°C at fixed processing conditions of 1.2 keV, 0.5 mA/cm2 and 20 min. Nitrogen content and layer thickness have been determined by nuclear reaction analysis. Structural and micromechanical analyses have been performed by X-ray diffraction and microhardness measurements.