EFFECT OF Ti-ION IMPLANTATION ON THE MECHANICAL AND CORROSION PROPERTIES OF THE FeCrNi SUPER ALLOY

Ion implantation is widely used for surface treatment to modify the near surface properties of materials especially semiconductors without changing their bulk properties. In this work an investigation on the effect of implantation by Ti-ion on the mechanical properties and the wet corrosion of the high Cr and Ni content FeCrNi alloy was performed. Because of its superior properties this alloy is also well known as super alloy and often used as structure material in nuclear reactors. The alloy was fabricated at BATAN in Bandung containing 55.98 wt.% Fe , 23.46 wt.% Cr, 18.23 wt.% Ni and small amount of other metal elements. The alloy sample was subjected to Ti-ion implantation in an ion generator with theoretical doses varied between 0.89x1016, 2.68x1016, 3.58x1016 and 10.75x1016 ion/cm2 respectivelly. The hardness measurement was conducted with Vickers method and the corrosion resistance test was carried out in the borax acid (HBO3) environment. The microstructure of the material after implantation was characterized and analyzed by means of the Scanning Electron Microscopy (SEM) equipped with the Energy Dispersive X-Ray Detector (EDX) while the surface crystal structure was idenfied using X-Ray Diffraction (XRD). The result showed that the Ti implantation improved the surface hardness when the dose was higher than 3.58x1016 ion/cm2, while the corrosion resistance increased abruptly at all ion doses. However, no microstructure change could be observed on the cross section. A thin layer which is indicated by BSE image contrast was observed in the top most surface. Analysis on the EDS spectrum revealed that the layer could be considered to be the titanium oxide elucidating the increasing of hardness and exceptionally higher resistance to wet corrosion.