Effect of cubic boron nitride grain size in the reinforcing of alpha-Sialon ceramics sintered via SPS

摘要

Utilising SPS, fully dense alpha-Sialon ceramics were obtained during sintering at temperatures as low as 1550 degrees C. This enabled the full densification alpha-Sialon composites with 10 and 100 mu m cubic boron nitride (cBN) grains. The detailed microstructural analysis of these materials with SEM and Raman spectroscopy revealed different cBN to hexagonal BN (hBN) conversion mechanisms. The smaller cBN grains only show a conversion into hBN on their surface whereas the large grains show not only conversion on the surface but also conversion at the internal grain boundaries between the twins detected inside the cBN grains. The increasing degree of formation of hBN results in decreasing hardness and increasing fracture toughness. Therefore the properties of materials with 100 mu m cBN grains are more sensitive to the sintering temperature. (C) 2014 Elsevier Ltd. All rights reserved.