HOT DYNAMIC CONSOLIDATION OF HARD CERAMICS

Diamond and cubic boron nitride powders were shock compacted at high temperature (873 and 973 K) by using a planar impact system at 1.2 and 2.0 km s-1. Silicon, graphite or a mixture of titanium and carbon powders were added to enhance the bonding of these superhard materials. Hot-consolidated specimens exhibited fewer surface cracks as compared with the specimens shock consolidated at room temperature. Diamond compacts having microhardness values over 55 GPa were obtained by subjecting porous mixtures of diamond crystals (4-8 mum) plus 15 wt% graphite (325 mesh) to an impact velocity of 1.2 km s-1 at 873 K. Well-consolidated c-BN samples, with microhardnesses (starting powders with 10-20 and 40-50 mum) over 53 GPa were obtained.