Effect of Al[sbnd]Ti content on mechanical properties of in-situ synthesized PcBN composites

Abstract

The polycrystalline cubic boron nitride (PcBN) was synthesized in situ under the condition of high pressure (5.5 GPa) and high temperature (1400 °C) with AlTi as the cubic boron nitride (cBN) binder. The influence of AlTi binder content on the phase composition and micro-structure of the PcBN composites were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results of density and mechanical properties test showed the content of AlTi is too small, the reinforcing phase in the sample is less, resulting in insufficient bonding between cBN particles and lower density. The AlTi content is too much, bulk Al3Ti is formed in the sample, the binder phase is agglomerated seriously, and the relative density and mechanical properties are decreased. However, when the content of AlTi binder is 15–20%, the reinforced phase rod-like TiB2 content in the sample is more, the aspect ratio is moderate, and PcBN can obtain better comprehensive mechanical properties.