Influences of Binders on the Mechanical Properties of TiB₂-TaB₂ Based Cermets

Abstract

This paper describes, firstly, the effects of the sintering temperature on the mechanical properties of TiB₂-5%TaB₂-1%CoB, TiB₂-5%TaB₂-1%NiB, TiB₂-5%TaB₂-1%FeB and TiB₂-5%TaB₂-1%Co alloys; secondary, the effects of the amount of binders on those of TiB₂-5%TaB₂-CoB, TiB₂-5%TaB₂-NiB and TiB₂-5%TaB₂-FeB alloys. The results were as follows:
1. CoB was the best binder for TiB₂-TaB₂ based cermets. The TiB₂-5%TaB₂-1%CoB alloys sintered at the temperature of 1700 to 1900°C for 28 min under 200 kg/mm² in a vacuum had the transverse rupture strength of 95 kg/mm², and scarcely had pores.
2. In the cases of CoB, NiB and FeB binders, TiB₂-TaB₂ based cermets had a solid solution between TiB₂ and TaB₂. However, TiB₂-5%TaB₂-1%Co sintered body scarcely had the solid solution between TiB₂ and TaB₂.
3. The binder phases of TiB₂-5%TaB₂-1%CoB alloy and TiB₂-5%TaB₂-1%FeB alloy may be CoB and FeB, respectively. The binder phases of TiB₂-5%TaB₂-1%NiB alloy may consist of NiB and monoclinic Ni₄B₃ and unknown phases. Also TiB₂-5%TaB₂-1% CoB alloy may have the binder phases of CoB and Co₂B.