Surface integrity of ultra-precision diamond turned Ti (commercially pure) and Ti alloy (Ti-6Al-4V)

The machinability of titanium and its alloys is generally considered as poor owing to characteristics such as low thermal conductivity, high strength at high temperatures, and low Young's modulus. In order to determine the behaviour of Ti and Ti-6Al-4V alloy, several samples were face diamond turned on an ultra-precision lathe (10 nm resolution). A mist of cutting fluid was used. The characterization techniques used were: scanning electron microscopy, optical microscopy, and contact and non-contact profilometry. The surface damage observed owing to interaction between tool and workpiece was associated with a phenomenon known as 'delamination'. The smallest values of roughness were 590 nm R-t for Ti and 416 nm Rt for Ti-6Al-4V under the same conditions. The results showed that the ultra-precision diamond turning is a viable option for the finish of Ti and Ti-6Al-4V.