Wear of CBN tool in turning of silicon nitride with cryogenic cooling

This paper reports the wear characteristics of a CBN tool in the turning of an advanced structural ceramic (silicon nitride) under dry cutting and cryogenic cooling conditions. A cooling system is designed to control the cutting temperatures on the tool by circulating cryogenic coolant through a reservoir built on the top of the cutting tool. This arrangement maintains the tool's hot-strength at its desirable range to resist tool wear in the cutting process. Experiments show that the tool wear significantly reduces with cryogenic cooling. Finite element analysis is used to estimate cutting temperatures on the tool and to reveal the reasons for different wear characteristics in the two cases. The analysis shows that the maximum temperature on the tool falls from 1153 degrees C (without liquid nitrogen cooling) to 829 degrees C (with liquid nitrogen cooling). (C) 1997 Elsevier Science Ltd.