Mechanical, structural and tribological properties of titanium nitrided by a pulsed laser

This work presents three processes for the surface nitriding of commercial purl titanium by means of a pulsed Nd-YAG laser: gas nitriding, melting of pre-deposited TiN powder and nitriding by reaction between titanium, nitrogen gas and TiN powder. Depending on the laser nitriding process. X-ray diffraction analyses always indicate formation of two phases, i.e. either (TiN, TiN0.3) or (Ti, TiN). In the laser-melted zones, metallurgical analyses by optical and scanning electron microscopies reveal dendritic microstructures. The thickness of the nitrided coatings was in the range of 30-250 mu m, depending on the nitriding process and the laser irradiation parameters. The in-depth microhardness of the nitrided zones varied between 550 and 1700 Vickers. The tribological behaviour of the laser-nitrided titanium surfaces has been investigated in room air by means of a pin-on-disk system. (C) 1998 Elsevier Science S.A.