Milling and turning of titanium aluminides by using minimum quantity lubrication

When machining difficult-to-cut materials, the high temperature in the cutting area is one of the dominating phenomena affecting tool wear and process capability. Hence, cutting fluids are profusely used for cooling and lubrication purposes, in order to obtain satisfactorily process performances. The use of conventional fluids creates several problems, such as the environmental pollution due to chemical disassociation at high cutting temperatures, water pollution, soil contamination during disposal, and biological problems to operators. The implementation of green machining strategies to accomplish the increasing pressures for sustainability is therefore an open challenge for manufacturers and researchers. Aim of this paper is to evaluate the influence of the lubrication strategy on tool wear, surface quality and environmental impact when milling and turning Ti-48Al-2Cr-2Nb (at. %) intermetallic alloys. The workpieces were obtained by means of two production processes: vacuum arc remelting and electron beam melting (EBM). Coated carbide tools were used in cutting tests under different lubrication conditions. The results of dry cutting are compared to that of wet and minimum quantity lubrication (MQL) conditions. Overall, the experimental tests show that dry machining requires a sensible reduction of process parameters to preserve a stable process, although limiting the energy consumption and reducing to zero the lubricant consumption. Under the chosen cutting conditions, MQL appears to be an advantageous solution for milling, whilst in turning wet cutting is the best choice for reducing the tool wear, since the higher process temperatures require the higher cooling effect of the emulsion.