Reactions and stresses in polycrystalline diamond-metal and diamond-carbide compacts

The kind of bonding phase has a significant influence on the microstructure and mechanical properties of diamond compacts. Microstructural studies of diamond with 5% wt. Ti and 5% wt. TiC (and also 30% wt. TiC) were carried o ut with a Transmission Electron Microscope. The TEM microstructural observa tions show differences between the metal and metal carbide bonding phase in diamond compacts. The mismatch of thermal expansion coefficients between d iamond acid the bonding metal or the compound induces significant internal stresses and may generate micro-cracks in polycrystalline diamond compacts. Twins and dislocations are the important details of microstructures in dia mond crystals after HPHT sintering. They can appear as a result of residual stress relaxation. Results of measurements of residual stresses on a diamo nd compact surface by means of the "sin(2)psi" X-ray diffraction method are reported.