Physicochemical and tribological characterization of titanium or titanium plus carbon implanted AISI M2 steel

Abstract

AISI M2 steel samples were implanted with 110 keV titanium ions at fluences ranging from 5 × 10 16 to 4 × 10 17 Ti cm -2. Titanium plus carbon dual implantation was also studied. Titanium distribution profiles were determined using the 48Ti(p,γ) 49V resonant nuclear reaction. The incorporation of carbon and oxygen from residual gases was studied as a function of titanium fluence and residual pressure using nuclear backscattering spectrometry at 5.7 and 7.5 MeV He + ion energies respectively. A competition phenomenon between carbon and oxygen incorporation is pointed out. Analysis of the phases formed was performed using conversion electron Mössbauer spectroscopy. Fe(Ti) solid solution, a-Fe x Ti 100− x and superficial a-Fe-Ti-C amorphous phases were identified. Tribological tests involving a ball (Al 2O 3 or 52100) and disc contact were performed to characterize the friction behaviour of the implanted surface. It is shown that titanium or titanium plus carbon implantation leads to a reduction in the friction coefficient. The wear tracks and debris were examined using scanning electron microscopy and electron microprobe cartography. For the two types of balls a reduction in the wear track width was observed together with oxidation of the wear debris. The tribological improvement observed depends not only on the presence of the superficial a-Fe-Ti-C amorphous layer but also on the surface chemical reaction during the wear process.