Sintering transition metal borides

Cemented borides with a metallic matrix have also been fabricated successfully from the ternary transition metal borides of so-called x-, ip- and ca-types since these composites can easily be liquid phase sintered with metallic melts. 

Tables 1 to 5 summarize the sintering eharaeteristies of borides of groups III A to VIA transition metals.

Fligh-temperature equilibria of the extraordinarily hard borides with metallic melts bring about the opportunity for a pressureless liquid phase sintering and the fabrication of hard and simultaneously tough composites similar to hard metals but are also of interest in ceramic systems or coatings. In this section emphasis is put on binary and ternary borides which are in equilibrium with transition metals. 

In order to achieve lower sintering temperatures, also many other metallic additives such as Ni, Co, and Cr, or borides of these elements have been used at higher concentrations to allow liquid phase sintering of TiB2- These transition metals... 

In a similar multiphase system, transition metal carbides were used as additives for pressureless sintering of TiB2, yielding composites of binary and ternary borides [218,296]. Attrition milled powder mixtures of TiB2 with 3-10 mass-% Co or Ni and 20-35 mass-% WC have been sintered in a vacuum at temperatures between... 

Subsequently, the most relevant data emerged from the investigations on Zr-, Hf- and Ta-carbides or borides are discnssed in order to understand the sintering mechanisms and the crucial role of MoSi or TaSi during densifieation. The interae-tion between carbides and borides with the two sdicides will be treated separately. For simplicity, Zr, Hf and Ta will be referred to as transition metal, TM. 

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