Spark plasma sintering of Al2O3–cBN composites facilitated by Ni nanoparticle precipitation on cBN powder by rotary chemical vapor deposition

Al2O3–cBN/Ni composites were consolidated by spark plasma sintering (SPS) using α-Al2O3 and Ni nanoparticle precipitated cBN (cBN/Ni) powders. The Ni nanoparticles, 10–100 nm in diameter and 0.5–2.2 mass% in content, were precipitated on cBN powder by rotary chemical vapor deposition. The effect of sintering temperature (TSPS) and Ni content (CNi) on the densification, phase transformation, microstructure and hardness of the Al2O3–cBN/Ni composites were investigated. The highest relative density of Al2O3–30 vol% cBN composite was 99% at TSPS = 1573 K and CNi = 1.7 mass%. At TSPS = 1673 K, the relative density decreased due to the phase transformation of cBN to hBN. The Vickers hardness of Al2O3–30 vol% cBN/Ni at TSPS = 1573 K and CNi = 1.7 mass% showed the highest value of 27 GPa.