Effect of sintering temperature and Y2O3 content on the comprehensive performance of Sialon‒TiB2‒AlN‒cBN composites

Abstract

This study focuses on the design of Sialon‒TiB₂‒AlN composite ceramics with thermal expansion coefficients matched to that of cubic boron nitride (cBN), used as binders to synthesize PcBN composites in situ under conditions of ultra-high pressure (5.5 GPa) and high temperature (1400°C‒1600°C). The effects of sintering temperature and Y₂O₃ content on the phase composition, microstructure, and mechanical properties of PcBN composites were systematically investigated. The results show that the phase compositions of the composites with different sintering temperatures are the same. A moderate addition of Y₂O₃ enhances the formation of Sialon within the system and promotes an increase in its aspect ratio. When the Y₂O₃ content is 2%, both long columnar Sialon and needle-like (or plate-like) TiB₂ coexist, with the aspect ratio of Sialon ranging from 4:1 to 5:1. At this composition, the interface bonding is optimal. Under these conditions, the Polycrystalline cubic boron nitride (PcBN) composite exhibits the best overall performance, achieving flexural strength of 990.72 MPa, hardness of 28.49 GPa, fracture toughness of 7.8 MPa·m¹/², and a maximum wear ratio of 1602.