Binderless Layered BN Toughened cBN for Ultra-precision Cutting

Abstract

Poor toughness and high synthesis pressure of binderless cBN limits its application in the field of cutting tool. To enhance the toughness of binderless cBN, an advanced layered BN toughened cBN (Lt-cBN) bulk was developed under industrial pressure. Then, the cutting performance and wear resistance of Lt-cBN was analyzed based on the unique microstructure during tungsten carbide cutting. It is found that the Lt-cBN reaches a high fracture toughness of 8.5MPa• m 1/2 , and is capable of realizing ultra-precision cutting of tungsten carbide with smooth surface of roughness lower than Ra 10nm.The layered BN at the intersection of cBN grains within Lt-cBN contributes to the enhanced toughness, which further slow down the transformation of amorphization as well as the wear rate of surface layer. Thus Lt-cBN exhibits better cutting performance and wear resistance with compared to commercial binderless pure cBN material. The wear of Lt-cBN can be understood as that the soft partially amorphous layer formed on the flank surface is rubbed and continuously removed in the form of abrasive wear.