FIBROUS NANOCORUNDUM PRODUCTS
FOR USE IN A HIGH-TEMPERATURE GAS FLOW
V. N. Sokov
and V. V. Sokov
Translated from Novye Ogneupory, No. 11, pp. 29 – 33, November, 2012.
Original article submitted April 23, 2012.
Results are presented from a study of the structure and kinetics of formation of a protective nano-inoculated
coating on a fibrous substrate. The article examines the erosion resistance of the materials at 1600 – 1800°C in
a gasdynamic unit with electric-arc heating (in an aerodynamic system with a sectional plasmotron). The gas
eous medium consisted of products of the combustion of kerosene in air. Flow velocity ranged up to
Keywords: fibrous nanocorundum products, fibrous structure, erosion resistance, protective coatings, gas
dynamic unit, nano-inoculant, fracture toughness.
One distinguishing feature of a new fibrous corun-
dum-based refractory that has been developed [1 – 4] is its
irreversible expansion after firing (its volume increases by
10 – 15%). This characteristic makes it necessary to select a
covering layer that will bond strongly with the material of
the refractory, study the kinetics of formation of the protec-
tive coating on the fibrous material, determine the optimum
firing regime, and examine the structure and durability of the
coating in high-temperature gas flows.
STUDY OF THE STRUCTURE
OF THE PROTECTIVE COATING
The structure of the protective coating was studied with
the use of a “JEOL JSM-840” scanning electron microscope.
The results of the study are shown in Figs. 1 and 2. It is ap
parent from the results that at low temperatures the coating is
a conglomerate with a scaly structure. With an increase in
temperature, the particles comprising the layer gradually be
come rounded, increase in volume, and grow together. At
limitingly high temperatures, the covering material is con
verted to aluminum oxide that has a porous-spherical struc
ture throughout the thickness of the resulting coating. The
surface of the coating appears uneven and hillocky when
viewed at high magnifications (see Fig. 1, a-h).
Examination of the transitional zone (the zone between
the coating proper and the fibrous substrate — see Fig. 2)
shows that the character of the surface of the fibers and the
covering material are the same throughout the investigated
temperature range. This can be taken as indirect proof that
the covering material and the fibrous substrate are formed at
the same time.
STUDY OF THE EROSION RESISTANCE
OF THE FIBROUS CORUNDUM-BASED
MATERIAL WITH A PROTECTIVE COATING
IN A HIGH-TEMPERATURE GAS FLOW
As was noted earlier , one of the main criteria used to
determine the service life of materials that are exposed to
high-temperature gas flows is the amount of mass that they
lose due to destruction of the surface layer. The amount of
mass lost by the material is significantly affected by its
thermophysical and mechanical properties (particularly the
condition of its surface layer) and by the aggressiveness of
the gas flow (its temperature, velocity, etc.).
To evaluate the mass loss and the changes in the proper
ties of the material when it is acted upon by a high-tempera
ture gas flow, we prepared fibrous specimens in the form of
hollow cylinders. This is the type of specimen that most fully
conforms to the established requirements — a uniform tem
perature distribution over the specimen’s cross section, uni
formity of the gas flow’s effect over the entire surface
washed by it, and constancy of the thermophysical parame
ters for the entire length of the test zone. A protective layer of
a covering material with a new composition was applied to
Refractories and Industrial Ceramics Vol. 53, No. 6, March, 2013
1083-4877/13/05306-0379 © 2013 Springer Science+Business Media New York
Moscow State University of Construction (Moscow, Russia).