Ultrahigh pressure hot isostatic pressing of TiN-coated diamond/TiN/alumina composites under thermodynamically unstable condition for diamonds

The mixtures of TiN-coated diamond, TiN and alumina were tried to be sintered by an ultrahigh pressure hot isostatic pressing (HIPing) to examine the fabrication of their composites. Though the HIPing condition (800 MPa at 1373 K for 21.6 ks) was thermodynamically unstable for the diamond, it was not transformed into graphite in the sintered composites. The composite containing 40 vol% diamond could be sintered into a sufficient density as well as the specimen with no diamond. The hardness of the composite consisting of 40 vol% diamond, 22 vol% TiN and 38 vol% alumina was about twice that without diamond.