Titanium alloys like Ti6Al4V are often used due to their high specific strength and excellent corrosion resistance combined with relatively low density. Their wear behavior is governed by metallic adhesion and material transfer, which results in high wear rates, limiting the use of these alloys mostly to non-tribological applications.
In order to improve tribological behavior, we used a ns-pulsed Yb:YAG-fiber laser to create dimple- and channel-textures on the Ti6Al4V surface. Tribological tests were performed under fretting conditions as well as under unidirectional sliding. The fretting experiments were conducted with a normal force of 20 N, frequency of 20 Hz and stroke length of 0.2 mm using a greased line contact. For unidirectional pin-on-disc experiments, oil lubrication and sliding speeds between 0.1 and 2.5 m/s at a pressure of 1 MPa were chosen. It became apparent that certain laser textures prevent adhesive wear and therefore greatly reduce wear rates compared to the untextured reference samples. Especially the redeposited material on the edges of the textures proved to be tribologically significant. This melt debris was further examined by light microscopy, focused ion beam-, scanning (transmission) electron microscopy and energy dispersive x ray spectroscopy. Different physical mechanisms will be discussed concerning the tribological behavior of the laser textures.
Ti6Al4V discs with similar channel textures were prepared using an innovative turning process. Textures were produced by moving the cutting tool backwards across the disc, perpendicular to the prior cutting direction and prospective sliding direction. Tribological testing was performed in unidirectional sliding under the same experimental parameters as for the laser textures. Again, adhesive wear was inhibited and wear rates decreased greatly compared to the reference surfaces.
Machined and laser textures will be compared and underlying mechanisms will be discussed.