Wear Behaviour of Steel and Titanium Treated by Pulsed IoN Implantation

Abstract

Ion beams generated by plasma guns operated in detonation mode follow the energy spectral lawdN/dE ≍ E^–3·5(number of ions N with energy E), with E in the range 20–500 keV, and a time duration ∆t of 200-400 ns. These pulsed ion beams were used to implant nitrogen ions into steel and pure Ti. The results show a reduction in the wear rate of stainless steel by a factor of 10, and of high speed steel by a factor of 2, and also a reduction in friction coefficient. In addition, in autotempering steel and Ti, an increase in Vickers microhardness by a factor of between 2 and 3 was measured. The XPS and X-ray diffraction measurements also show high nitrogen concentration in the surface layers, with the nitriding producing the desired stoichiometry for tribological purposes. A studyof the temperature evolution of the substrate owing to the pulsed nature of the beams (heating rate around 15 K ns^–1, temperature gradients of around 1500 K μm^–1, and peak temperatures near the melting point) shows that it plays an important role in the surface modification process.