New Hardmetals Based on TiB2

Sintering of TiB2-hardmetals with ferrous binders results in the
formation of parasitic Fe2B which consumes a good part of the ductile
binder. Besides Fe2B, Ti2O3 is formed during sintering. Thermodynamic
considerations, dilatometry and X-ray analysis show that the impurities
in commercially available TiB2-powders are responsible for the
development of these phases. It is possible to avoid Fe2B by adding
metals with a higher affinity to boron than iron.
Based on these investigations, TiB2-hardmetals with single phase
Fe-Cr-Ni binders or two phase Fe2B-Fe-Cr-Ni binders were produced. The
binder content was varied between 5 and 20 vol.%. These TiB2-hardmetals
show better hardness-fracture toughness combinations than conventional
WC-Co-hardmetals or Ti(C,N)-cermets and excellent hot hardness. These
properties are very promising at the present state of development, and
it appears that the full potential of the system has probably not yet
been reached. Further progress seems to be possible, when fine grained
TiB2-powders with low O and C content and little excess boron become
available. Such powders are expected to improve sintering behaviour,
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microstructure and mechanical properties of TiB2-hardmetals.