Mechanical and Thermal Load Effects of Novel MWFs Delivery Method in Milling of Ti–6Al–4V

Abstract

This work mainly focuses on the effectiveness of both rake and flank face application of the different metal working fluid (MWF) strategies such as liquid CO2, minimal quantity lubrication (MQL), and emulsion in face milling of Ti–6Al–4V alloy. Modified CoroMill 600 cutter via internal channels to both rake and flank faces of the inserts with PVD coated inserts were used for the studies. This novel approach of delivery of MWFs has been investigated on effective thermo-mechanical loads; in terms of the evolution of cutting temperature, cutting forces, and residual stresses. The hardness of the machined surfaces and chip microstructure analysis were also conducted to understand more about the mechanical and thermal load effects in machined material and observed parameters. It has been found that the effectiveness of both rake and flank application of the liquid CO2 machining is a better alternative for the emulsion and MQL strategies. Low thermal deformation of the material, higher magnitude of compressive residual stresses, and lower thermal load throughout the machining cycle have been observed. However, an increase in the mechanical load was observed because of the cold strength hardening of the Ti–6Al–4V workpiece at the liquid CO2 environment. These effects are negligible at room temperature after machining. Overall results show that the cryogenic machining offers best and lower thermal load effects over MQL and emulsion strategies for both rake and flank applications.