Temperature dependent surface modification of T91 steel under 3.25 MeV Fe-ion implantation

Highlights: • Surfaces of T91 samples were modified by 3.25 MeV Fe ions at different temperatures. • Positron annihilation and nano-indentation tests are used to study the implanted samples. • All the implanted samples were hardened and harnesses increased with increasing temperature. • Impact of decreased open-volume defects on implantation hardening is inconspicuous. - Abstract: Ion implantation is an established technique for modifying the surface properties of a wide range of materials. In this research, temperature dependent surface modification induced by Fe-ion implantation in T91 steel was investigated. The T91 samples were implanted with 3.25 MeV Fe-ions to fluence of 1.7 × 10¹⁶ ions/cm² at room temperature, 300 and 450 °C, respectively. After implantation, the T91 samples were characterized by means of positron annihilation Doppler broadening spectroscopy (PADBS) and nano-indention technology (NIT). It was found that the concentration of open-volume defects in T91 samples decreased with increasing implantation temperature. From NIT analysis, it was found that all the samples were hardened after implantation and the hardness of the implanted T91 samples increased with increasing implantation temperature