MECHANICAL, STRUCTURAL AND TRIBOLOGICAL PROPERTIES OF TITANIUM NITRIDED BY A PULSED-LASER

This work presents three processes for the surface nitriding of commer cial purl titanium by means of a pulsed Nd-YAG laser: gas nitriding, m elting of pre-deposited TiN powder and nitriding by reaction between t itanium, 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 zo nes, metallurgical analyses by optical and scanning electron microscop ies reveal dendritic microstructures. The thickness of the nitrided co atings was in the range of 30-250 mu m, depending on the nitriding pro cess and the laser irradiation parameters. The in-depth microhardness of the nitrided zones varied between 550 and 1700 Vickers. The tribolo gical behaviour of the laser-nitrided titanium surfaces has been inves tigated in room air by means of a pin-on-disk system. (C) 1998 Elsevie r Science S.A.