Effect of Cryogenic Treatment on Electric Discharge Machining of Titanium and Its Alloys

Abstract

Titanium is recognized as a difficult-to-machine material using the traditional machining processes, resulting in higher tooling costs. Economical machining of titanium alloys has become important for industrial products and research work. Although titanium alloy can be machined economically using the nontraditional or nonconventional machining processes, the selection of the suitable machining process and its parameters for higher machining rate and dimensional accuracy is a challenging task. Electric discharge machining (EDM) is one of the nonconventional machining method that has unique advantages over other machining methods. Therefore, its use is increasing for machining of any type of electrically conductive hard, high-strength, and temperature-resistant materials in a contactless mode especially when complex geometries are required. Due to its favorable characteristics and advantages, EDM process is extensively used for machining of titanium alloys. As it is well known that titanium alloys have high electrical resistivity, ie, low conductivity and poor thermal conductivity, this makes the machining difficult by the EDM process. In EDM, the overall performance of the machining process very much depends upon the thermoelectrical properties of both the electrodes (tool and workpiece). Cryogenic treatment (CT) has a history of improving the properties of the materials, ie, mechanical, electrical, and thermal. The CT process consists of a slow cooling from room temperature to the liquid nitrogen temperature, soaking for an suitable time at this temperature, and after that the materials are heated up to room temperature. In the CT process the cooling rate and heating rate are critical factors that affect the properties of the materials. In the present study an attempt has been made to investigate the effect of CT on the machinability of titanium alloys.