ELECTRICAL ASPECTS OF THE SPARK-PLASMA SINTERING OF TiN-TiB_2 COMPOSITE. I. EFFECT OF ELECTRICAL PARAMETERS OF SPARK-PLASMA SINTERING ON THE STRUCTURE AND PROPERTIES OF TiN-TiB_2 COMPOSITE

摘要

The electrical aspects of spark-plasma sintering (SPS) of TiH_2-BN and Ti+BN powder mixtures for the production of a TiN-TiB_2 ceramic composite material are studied, and the dependence of its properties on direct-current density at the initial stage of sintering is established. To determine the direct-current density, a method for calculating the effective cross-sectional area S_(eff) of the die-sample circuit is proposed. At the initial stage of sintering, the major portion of the current flows through the graphite die because of the resistance of the contacts and the presence of a-BN dielectric. At the final stage of sintering, the current flows mainly through the sintered sample because of the synthesis and densification of the TiN+TiB_2 composite and, consequently, the abrupt increases in the conductivity of the sintered sample. Increasing the initial direct-current density during the sintering of TiH_x hydride samples leads to an increase in relative density (conductivity), microhardness, fracture toughness, and abrasive wear resistance.