cBN-TiN, cBN-TiC composites: chemical equilibria, microstructure and hardness mechanical investigations

This paper summarizes theoretical and experimental studies of cBN-TiN and c BN-TiC of cBN:TiN/TiC molar ratio 1:1 and 2:1. Theoretical calculations sho w that, at temperatures between 1000 and 1400 degrees C, TiN reacts with BN forming one new phase, TiBx, and that TiC reacts with cBN forming two new phases, TiB2 and TiC0.8N0.2. Experimental cBN-TiC/TiN composites were prepa red by high pressure hot pressing and the samples were subsequently heat tr eated. After heat treatment, sinters of cBN-TiN/TiC were characterized using trans mission electron microscopy and X-ray diffraction. The samples exhibited a dense polycrystalline structure, and a thin layer of fine TiB2 was visible at the BN-binder interface. It was found that hardness decreased significan tly after heat treatment. (C) 1999 Elsevier Science S.A. All rights reserve d.