The Effect of cBN Powder with Matched Particle Size on the Properties of PcBN Composites with Ti₃AlC₂ System

Polycrystalline cubic boron nitride (PcBN) composites were prepared via high-temperature and high-pressure sintering. The cubic boron nitride (cBN) powder with matching grain sizes of 0-0.5 µm, 0.5-1 µm, and 1-2 µm was used as the raw material, and Ti₃AlC₂ served as the binder. The impact of matched cBN powder content on the phase composition, microstructure, and mechanical properties of PcBN composites was explored. The rearrangement and filling of the particles inside the matched cBN powder allowed the composites to reach their optimal stacking condition. Furthermore, the decomposition products of Ti₃AlC₂ reacted with cBN to form TiC, TiB₂ and AlN, thereby improving the bond between cBN grains as well as ensuring the optimal density and mechanical properties of PcBN composites. The maximum relative density (99.5%), flexural strength (556 MPa), Vickers hardness (42.8 GPa), and abrasive ratio (7350) of PcBN composites were attained at 80 wt.% cBN powder content. Additionally, the highest fracture toughness of PcBN composites (9.18 MPa m^1/2) was enriched at 75% wt.% cBN content.