Morphological study of a cubic boron nitride (CBN) cutting tool and characterization of its wear scenarios in abrasive machining process

Abstract

Cubic boron nitride (CBN) composites are usually fabricated by sintering abrasive particles and binder powders under certain temperature and vacuum conditions. As a result, the inherent geometrical inhomogeneity of the abrasive grains in the binding matrix becomes an important intrinsic characteristic. In abrasive machining, the surface quality of workpieces is determined, to some extent, by the morphological characteristics of the grains extruded out of cutting surfaces. Within this regard, this work aims to characterize the morphological characteristics and to assess the wear modalities of CBN grains, at the same time to find out their eventual correlations. In doing so, a commercial CBN honing tool, namely B151/L2/10/50 (B151), is chosen as target material. A 3D model of a selected volume was reconstructed by applying cross-sectioning and digital image processing methods. Based on the grain segmentation and quantification, morphological characteristics of the grains are individually and statistically analyzed. Wear scenarios of the tool were characterized after cutting tests. Grains were found to have commonalities in shape and dimension on a microscale perspective despite their inhomogeneous distribution. Wear modalities are strongly related to the morphological characteristics of the grains. Specifically, degradation commences at spikes, with fractures initiating along the grain edges by either splitting grains and binder or intruding into the grains.