Analytical and experimental study on laser assisted machining of Ti6Al4V at low cutting speeds

Difficult-to-cut materials like Ti6Al4V find wide applications in the aerospace and biomedical industries because of their high strength-to-weight ratio, corrosion resistance, and biocompatibility. However, conventional machining of Ti6Al4V needs high cutting power owing to the high strength of the alloy. Laser assisted machining (LAM) is a hybrid machining process that can reduce cutting power while machining Ti6Al4V. During the process, a laser heating source constantly precedes the tool. Consequently, the material plasticity increases because the dislocations gain energy from the laser and move rapidly. The increase in plasticity is reflected in the reduced flow stress and cutting power. In this study, a non-dimensional thermal solution for the temperature rise in the shear zone because of laser tracing was first derived. Subsequently, the thermal solution was coupled with the unequal division shear zone model to determine the cutting power during LAM. However, three improvements were made to the unequal division shear model to improve the accuracy of the results. First, the constant shear zone thickness assumption was replaced with Grzesik’s expression for shear zone thickness. Secondly, constant specific heat at the shear zone was replaced by temperature-dependent specific heat of the material. Finally, instead of maximum shear stress at the shear zone, the average shear stress was utilized for cutting force calculation. Modeling was followed by validation experiments. Cutting velocities of 15, 22.5, and 30 m/min; feed of 0.1 mm/rev; width of cut of 1.5 mm; laser power of 100 and 300 W; and laser spot size of 0.5 mm were the parameters used for the experiments. A maximum of 23% reduction in cutting power was observed in LAM compared to conventional machining at a cutting velocity of 15 m/min. Moreover, tool wear studies were done using scanning electron microscopy (SEM) images. A cutting speed of 22.5 m/min was found to be optimal from a tool wear perspective.