PREPARATION OF MULLITE–TiC–ZrC-CERAMIC MATERIALS
BY A PLASMA-ARC METHOD AND THEIR PROPERTIES
A. V. Hmelov
Translated from Novye Ogneupory, No. 12, pp. 36 – 41, December, 2016.
Original article submitted September 16, 2016.
The phase composition for synthesized titanium carbide TiC and zirconium carbide ZrC powders is provided,
and development of the crystal phases, microstructure, relative density, open porosity, true shrinkage, hard
ness, strength in compression of mullite–TiC–ZrC-specimens with a different ratio of TiC and ZrC sintered by
a plasma-arc method in the range 1200 – 1500°C is demonstrated. Synthesized TiC and ZrC powders have in
tense crystallization of TiC and ZrC phases, and sintered specimens with a different ratio of TiC and ZrC have
different mullitization in the range 1200 – 1500°C and degree of TiC and ZrC phase development at up to
1500°C. Above 1500°C there is development of TiC or ZrC phases in relation to the ratio of TiC and ZrC
within sintered materials. Specimens with a higher TiC concentration have a denser sintered microstructure
compared with specimens containing a greater amount of ZrC. This facilitates an increase in relative density,
linear shrinkage and a reduction an open porosity, formation of harder specimens with uniform indentation
impression without damage formation around it, and with the best strength indices in compression.
Keywords: mullite–TiC–ZrC-ceramic materials, plasma-arc sintering, properties.
Mullite and mullite–ZrO
-ceramic specimens, sintered
by a traditional method, are highly recommended as quite
dense hard materials with relatively good physicomechanical
indices. Specimens have developed crystallization of corre
sponding phase which is only achieved at high temperature
[1, 2]. In order to obtain similar property indices at lower
temperature, and also to improve their values with an in
crease in temperature, a number of approaches are used: in
troduction of various artificial additives  or natural origin
component (clay) ; use of finely dispersed powders pre
pared by milling ; use of contemporary forms of sintering,
for example plasma-arc ; control of particle sizes through
various synthesis methods [7, 8].
A contemporary area making it possible to improve sig
nificantly the physicomechanical properties of different
forms of oxide ceramic, in particular mullite or corundum, is
plasma-arc sintering of appropriate oxide powder with a rela
tively small amount of powder of an oxygen-free substance
[9 – 11]. As a result of this crystal phases develop in materi-
als, there is an increase in particle sintering intensity, espe-
cially for powder of oxygen-free substances, and there is an
improvement in material physicomechanical properties
[9, 11]. This makes it possible to prepare number different
oxide-oxygen-free ceramic materials, for example corun
dum — BN , mullite — BN , and mullite — TiC .
An increase in concentration of oxygen-free substance
powder, in particular boron nitride and titanium carbide,
within a mixture with oxide powder, leads to a reduction in
relative density, linear shrinkage, hardness, and strength in
compression with an increase in temperature [9 – 11]. Phase
transformation also gives rise to a reduction in values of
these physicomechanical properties, for example in boron
nitride with an increase in sintering temperature [9, 10].
The aim of the work is preparation of mul
lite–TiC–ZrC-specimens with a different ratio of titanium
carbide TiC and zirconium carbide ZrC by a plasma-arc
method in the range 1200 – 1500°C from prepared mixtures
, TiC, and ZrC powders, determination of syn
thesized TiC and ZrC powder composition, a study of the
composition of crystal phases, microstructure, relative den
sity, open porosity shrinkage, hardness, and strength in com
pression of specimens with a different TiC and ZrC ratio.
Refractories and Industrial Ceramics Vol. 57, No. 6, March, 2017
1083-4877/17/05706-0645 © 2017 Springer Science+Business Media New York
Institute of Silicate Materials of Riga Technical University, Riga,