Investigations on characterization and machining performance of cryotreated single point cutting tools

Abstract

Today s metal cutting industry necessitates a never-ending demand for high productivity. The life of cutting tools plays a major role in increasing productivity and consequently is an important economic factor. Therefore, focusing research on innovative techniques for prolonging the tool life is the need of hour. One such technique is the cryogenic treatment of cutting tools. Cryogenic treatment has a great potential to increase the cutting life by many folds through slowing down the wear phenomenon of the cutting tools. With better understanding of the cryogenic process, a wider acceptance of cryogenic treatment is possible. It is therefore, necessary to focus research efforts on complete understanding of cryogenic treatment process and its influence on metallurgical and mechanical properties of tool materials. Cryogenic treatment of cutting tools has been in use for many years but is still in its infancy when compared to conventional heat treatment processes. It was revealed in 1930 s and 1940 s that this treatment can improve the performance of cutting tools. Cryogenic treatment is not, as it is often mistaken for, a substitute for good heat treatment, rather it is an add-on or supplemental process to conventional heat treatment to be done before tempering. A typical cryogenic treatment cycle consists of a slow cool-down rate (0.5 1 °C/min) from room temperature to the temperature of liquid nitrogen. When the tool material temperature reaches approximately at 196 °C, it is soaked for an appropriate time generally 18 38 h. Then the tool is brought back to room temperature from the liquid nitrogen temperature at a predefined rate. Single tempering cycle is usually performed after cryogenic treatment to improve impact resistance, but sometimes double or triple tempering cycles are also used. After 70 years of important applications of cryogenic treatment of tool materials, the elucidation of metallurgical principles responsible for improved mechanical properties has not yet found a uniform interpretation.