LASER MELTING OF PLASMA-NITRIDED TI-6AL-4V ALLOY

A laser surface modification technique can be used as a part of a dubl ex treatment process to improve the surface properties of Ti-6Al-4V al loy. The present study is conducted to investigate the surface propert ies of the Ti-6Al-4V alloy due to laser melting prior to a plasma nitr iding process. Consequently, nitriding is carried out to obtain the de pth of the nitride zone of 30 mu m. A CO2 laser with 1.6 kW output pow er was used to melt the nitride layers. The wear properties of the pla sma nitrided and nitrided/melted surfaces were investigated using pin- on-disc equipment while the friction coefficient was determined using a ball-on-disc machine. The nitride depth profile was measured using a nuclear analysis reaction and elemental distribution in the melted zo nes was investigated using mu-PIXE. Scanning electron microscopy and o ptical microscopy were carried out to analyze the microstructures deve loped before and after the laser melting process. In addition, heating and cooling rates were predicted through the electron-kinetic theory approach. (C) 1997 Elsevier Science S.A.