3. Thermal-Assisted Machining of Titanium Alloys

Titanium alloys are used in a variety of engineering applications, especially in automotive, aerospace and nuclear fields due to their high strength and excellent corrosion resistance. Nevertheless, titanium alloys have extreme mechanical properties making them very difficult to machine with low thermal conductivity and high chemical reactivity at high temperature. Hence, titanium alloys are required to machine at low cutting speed and feed rate but that increases the cost of production of the components made by these alloys at large. Thermal-assisted machining (TAM) is an effective approach for conventional machining whereby titanium workpiece is locally softened before/during machining with external heating. Localized reduction in workpiece hardness facilitates higher material removal rate (MRR) and extended cutting tool life whilst resulting in better surface finish. This chapter compares and analyzes the merits of different heating techniques for machining of titanium alloys. The techniques under consideration are heating by laser beam, plasma torch heating and heating with the use of induction coil. The laser beam and plasma torch tend to produce more intense localized heating compare to that by induction coil. Moreover, the laser technique offers very controllable process heating compared to other two techniques. Laser-assisted machining (LAM) also largely reduces cutting forces leading to better surface finish. Thus, laser-assisted technique is recognized to be more cost-effective and productive for improving machinability of titanium alloys than rest of the heating techniques.