Cooling approaches and cutting temperatures in cryogenic machining of Ti-6Al-4V

Cryogenic machining is an environmentally safe alternative to conventional emulsion cooling. In this study, liquid nitrogen (LN2) is applied to cutting Ti-6Al-4V, a difficult-to-machine but widely used material in aerospace industry. With the goal of identifying the cooling approach for most effectively and economically using cryogenic machining, this study evaluated cutting temperatures obtained under various cooling conditions. In addition to analyzing cooling approaches reported in previous cryogenic machining literatures (i.e., precooling the workpiece and conductive remote cooling), this paper introduces an innovative and economical dispensing method that directs LN2 through micro jets to the flank, the rake, or both near the cutting edge. The cutting temperatures were theoretically estimated by finite element method and the influence of cutting speed was analyzed. They were experimentally verified using the thermocouple imbedded at the carbide insert. Temperatures in cryogenic machining were compared with conventional dry cutting and emulsion cooling. Findings showed that a small amount of liquid nitrogen applied locally to the cutting edge is superior to emulsion cutting in lowering the cutting temperature. The study found that cooling approaches in order of effectiveness (worst to best) to be: dry cutting, cryogenic tool back cooling, emulsion cooling, precooling the workpiece, cryogenic flank cooling, cryogenic rake cooling, and simultaneous rake and flank cooling. (C) 2001 Elsevier Science Ltd. All rights reserved.