Fabrication of TiB-TiC, TiB-TiN and TiB₂-TiC Composites and Their Bonding to Ti-6Al-4V Alloy by Spark and Resistance Sintering

Abstract

Mixture of TiB₂, Ti and TiC or TiN powder as well as TiB₂ and TiC powder were spark- and resistance-sintered to obtain TiB-TiN, TiB-TiC and TiB₂-TiC composites. In addition, the plates of these composites were bonded to Ti-6Al-4V alloy substrate by the resistant-sintering. The Vickers hardness and the bending strength of TiB-TiC and TiB-TiN composites reach their maxima at about 20 mol% of TiN or TiC, while those of TiB₂-TiC composite take the maxima at about 70 mol% of TiC. The bending strength of the TiB₂-70 mol%TiC composite is larger than that of the TiB-20 mol%TiC composite when the sintering temperature is 1973 K. However the bending and adhesion strengths of TiB-20 mol%TiC composite layer bonded on Ti-6Al-4V alloy are larger than those of the TiB₂-70 mol%TiC layer when the bonding temperature is 1673 K. The bending strength of the TiB-20 mol%TiC bond layer increases with decreasing ratio of bond layer thickness to substrate thickness, which can be explained by the existence of residual stress introduced during cooling after bonding at high temperature.