TITLE:
Experimental Study and Thermodynamic Analysis of High Temperature Interactions between Boron Carbide and Liquid Metals
AUTHORS:
Michael Aizenshtein, Natalya Froumin, Nachum Frage
KEYWORDS:
Boron Carbide, Titanium Diboride, Silicon Carbide, Metals, Wetting, Interface
JOURNAL NAME:
Engineering,
Vol.6 No.13,
December
8,
2014
ABSTRACT: Fabrication of MCCs
(Metal Ceramic Composites) and ceramic brazing requires improved wetting properties
are often absent in various ceramic/metals systems. This report summarizes a comprehensive
study concerning the wetting properties of boron carbide in contact with non-reactive
metals such as Cu, Au, Ag, and Sn. In order to improve wetting, three different
reactive elements were added to the melts; Si, which has relatively high affinity
to C, leads to SiC formation and changes the stoichiometric boron carbide composition
(B4C) towards lower carbon content; Ti, which displays high affinity
to B, leads to TiB2 formation and free carbon precipitation at the interface; and finally, Al, which forms borocarbide phases at the interface. It was
found that Cu is unusual with respect to boron carbide compared the other non-reactive
metals. The most important difference is its ability to dissolve ~25 at% of B,
which makes B adequate as an additive to Cu in addition to Si, Ti, and Al. When
boron was used as an alloying element, its effect on wetting behavior was attributed
to altering the boron carbide composition in contact with boron-containing melts.
It was concluded that the most important properties of boron carbide that affect
wetting phenomena are the relatively low chemical stability and the existence of
a wide composition range (B4C-B10C). The first property determines
the possibility of boron carbide to react with liquid metals (by dissolution or
formation of new phases) and the second offers an additional degree of freedom to
improve its wetting by changing the composition of the ceramic phase.