Sustainable production of dry-ultra-precision machining of Ti–6Al–4V alloy using PCD tool under ultrasonic elliptical vibration-assisted cutting

Abstract

The Ti–6Al–4V alloy is regarded as a typical hard-to-machine material owing to its small thermal conductivity and low deformation coefficient. Large amounts of cutting fluids are required and consumed in the traditional ultra-precision machining of the Ti–6Al–4V alloy to reduce the cutting temperature and inhibit tool wear. Negative effects, such as environmental pollution and hazards to operator, follow behind owing to the use of cutting fluids. Dry machining is considered as the ideal environmentally friendly machining strategy. However, traditional dry-ultra-precision cutting (TDUC) of Ti–6Al–4V alloy is not practical because of the rapid deterioration of surface integrity and tool life induced by extremely high cutting temperature. In this paper, a novel machining technology known as ultrasonic elliptical vibration-assisted cutting (UEVC) was adopted for overcoming the machining difficulties in the TDUC process of Ti–6Al–4V alloy. Moreover, the commercial polycrystalline diamond (PCD) tool was employed to achieve more economical and sustainable production. Thanks to the effects of UEVC technology, the cutting and friction forces were significantly reduced, and the generated cutting heat quickly dissipated, which caused a great reduction of the cutting temperature. Thus, the pressure of tool damage was relieved. The experimental results indicated that, when the UEVC technology applied in the TDUC process, the tool wear was observably suppressed, the surface integrity was significantly improved. And an undamaged ultra-precision finished surface with a roughness value less than 30 nm was produced. Besides, the shorter, regular and breakable chips were obtained, and achieving a better chip control. Conversely, the TDUC process provoked poor surface quality, severe tool wear, and long, irregular, and unbreakable chips. Therefore, the proposed machining technology minimizes the negative effects induced by the use of cutting fluids, and provides sustainable process for dry-ultra-precision machining of Ti–6Al–4V alloy in practical application.