Effects of cryogenic cooling by liquid nitrogen jets on tool wear, surface finish and dimensional deviation in turning different steels

High production machining at high cutting velocity and feed generates large amount of heat and high cutting temperature, which shortens the tool life and deteriorates the job quality. This problem becomes more acute when the jobs are difficult to machine and are to be used under dynamic loading. The conventional cutting fluids are not that effective in such high production machining particularly in continuous cutting of materials like steels. Further, the conventional cutting fluids are not environment friendly. The disposal of the cutting fluids often leads to local water pollution and soil contamination. Recycling and reuse of conventional cutting fluids are problems in the future. In this decade, with increased environmental awareness, the researchers are striving to develop environment friendly machining technology; one such technology is to use cryogenic cooling with liquid nitrogen. This paper deals with experimental investigation in the role of cryogenic cooling by liquid nitrogen jets on tool wear, surface finish and product quality in turning of Ni–Cr steel, and 42CrMo4 steel at different cutting velocities and feeds by two types of carbide inserts of different geometry. Compared to the dry machining, cryogenic machining performed much superior mainly due to substantial reduction in cutting zone temperature enabling favourable chip formation and chip–tool interaction. It also provides reduction in cutting forces and substantial reduction in tool wears, which enhanced the tool life, dimensional accuracy and surface finish. Furthermore, it provides environment-friendliness and improves the machinability characteristics.