Evaluation of Cryogenic CNC Milling of Ti-6Al-4V Titanium Alloy

Machining titanium alloys is always considered difficult due to special material properties of these alloys and their strange behaviour during machining operations. Cryogenic cooling by using liquid gases has attracted considerable research since the early 20th century and is acknowledged as an effective technique for controlling the cutting temperature and improving machinability. Despite announcement of the industrial use of cryogenic milling systems, there are limited scientific studies on the effects of cryogenic cooling in CNC milling of titanium alloys. This paper presents one of the very first scientific attempts to study the effects of cryogenic cooling in CNC milling of the Ti-6Al-4V titanium alloy in comparison with dry machining. A series of machining trials have been conducted at the University of Bath and it has been proven that cryogenic machining has the potential to significantly improve the machinability of titanium alloys in CNC milling with considerable reductions in surface roughness and improved tool life. Investigations revealed that the introduction of liquid nitrogen as a coolant resulted in 2.5 times improvement in surface roughness of the machined parts as compared to dry machining while a maximum increase of 1.9% in power consumption was recorded.