LASER NITRIDING OF PURE TITANIUM WITH NI, CR FOR IMPROVED WEAR PERFORMANCE

Titanium and its alloys suffer from galling, seizing, ploughing and ad hesion during sliding contacts. A laser nitriding method to improve th e tribological properties of pure titanium was investigated in this st udy. Before laser nitriding, a layer of nickel and chromium was plasma sprayed onto the surface of pure titanium in order to prevent the for mation of cracks and pores during laser treatment. A scanning electron microscope (SEM) and image analyser were used to optimize the laser p rocessing parameters and analyse the coating microstructure. X-ray dif fraction (XRD), a Talysurf 5 tester and microhardness tester were used to analyse the phase crystallinity, surface roughness and microhardne ss of the laser treated coating. A ball-on-flat reciprocating wear mac hine was used to evaluate the sliding and fretting wear behaviours of both untreated and laser treated specimens. Results showed a substanti al improvement in wear resistance after laser treatment which can be a ttributed to a significant improvement in hardness and corrosion resis tance as well as a decrease in friction properties of nitrided layers. (C) 1998 Elsevier Science S.A.