Surface texture and friction property of Ti-6Al-4V processed by rotary ultrasonic rolling

Micro-texturing on machined surface has been widely applied to improve surface friction and wear properties. This paper aimed at establishing a relationship among process parameters, machined surface texturing, and friction property of scaly surface fabricated by rotary ultrasonic rolling. Firstly, a kinematic model of the scaly surface topography formation was proposed based on motion analysis between the roller and workpiece. Secondly, the roller profile was considered in the proposed model to describe the scaly surface topography formation. Three-dimensional surface roughness characteristic parameters Sa, Sz, and Sq were adopted to evaluate the scaly surface topography. These three-dimensional surface roughness parameters can be theoretically predicted with the proposed kinematic model for the scaly surface fabricated by rotary ultrasonic rolling of titanium alloy Ti-6Al-4V. The theoretical predictions of Sa, Sz, and Sq were verified with the experimental results. Finally, the friction coefficients of scaly surfaces generated with various rotary ultrasonic rolling parameters were tested. The friction coefficient of the scaly surface was minimum at ultrasonic amplitude of 7 mu m. The results demonstrated that the surface texturing with larger scaly ridges possessed improved frictional performance under identical test conditions.