Titanium alloys like Ti6Al4V are often used due to their high specific strength and good corrosion resistance combined with relatively low density. It is the poor tribological performance that limits their use in many applications. In case of aircraft landing gears, system weight could be reduced by replacing steel parts with Ti6Al4V, leading to higher efficiency and payload of the airplane.
It is the aim to manufacture tribologically optimized surfaces. In this study the tribological performance of Ti6Al4V discs turned with different process parameters resulting in different surface integrities is investigated. In these investigations, tool geometry (macro and micro), as well as cutting speed and feed rate were kept constant at 160 m/min and 0.1 mm/rev, respectively. Cutting depth was varied between 0.005 and 0.3 mm. Microstructures of the machined discs were analyzed with regard to thickness of the nanocrystalline layer and subsurface plastic deformation using a Scanning Electron / Focused Ion Beam dual beam system. For tribological characterization, pin-on-disc tests under unidirectional sliding were conducted. Pins were composed of a metal-polymer-compound bearing material. An aviation hydraulic fluid was used as lubricant. Contact pressure was varied from 1 to 10 MPa and sliding velocity between 0.05 and 3 m/s. Stribeck curves for all four variations of machining were recorded and correlated to the microstructure of the surface layers.
Joint Project “FAWIBO”: supported by German Federal Ministry for Economic Affairs and Energy (BMWi) according to a decision of the German Federal Parliament.