TiB₂ must be used in a composite form having a high mechanical strength for use in application. When Ni4B3, (or NiB, or CoB) was added to TiB₂, they were found to compose a strong cermet. However, it is still not clear how the sintering conditions effect the mechanical properties of the alloys.
This paper describes, firstly, the effects of the sintering temperatures on the mechanical properties of TiB₂-8.8%Ni₄B₃, TiB₂-l1%NiB, TiB₂-11.3%CoB, and TiB₂-10.4%FeB sintered alloys; secondary, the effect of the sintering conditions such as the amount of binders and sintering time on those of TiB₂-NiB and TiB₂-Ni₄B₃ sintered alloys; finally, the additive effects of metal-diboride on the mechanical properties of compacts in the case of using a direct flow method of electric current. The results were as follows:
1. NiB is the best binder for TiB₂-binder alloys.
2. When a TiB₂-binder mixed powder sample is sintered and well compacted, TiB₂ grains grow markedly. Therefore, the transverse rupture strength of these alloys showed a marked decreased.
3. Additive metal-diborides restrain the growth of the TiB₂ grains with the following composites, TiB₂-5%VB₂-1%CoB, TiB₂-5%VB₂-1%FeB, TiB₂-5%NbB₂-1%NiB, TiB₂-5%NbB₂-1%CoB, TiB₂-5%NbB₂-1 %FeB, TiB₂-5%TaB₂-1%NiB, TiB₂-5%TaB₂-1%CoB, TiB₂-5%TaB₂-1%FeB, TiB₂-5%CrB₂-1%CoB, TiB₂-5%MoB₂-1%NiB and TiB₂-5%MoB₂-1%CoB. Therefore these compacts have a high transverse rupture strength and a high density. 4. These three component system sintered alloys have a Vickers hardness (300 g load) Hv of 900-1100 kg/mm² at 700°C.