REFRACTORIES IN HEATING UNITS
EXPERIENCE OF USING SILICA-FREE ALUMOX BINDER
IN TECHNOLOGY FOR PREPARING COMPOSITE CERAMIC INVESTMENT
CASTING MOLDS FOR SUPERALLOY DIRECTIONAL SOLIDIFICATION
T. F. Baranova,
S. A. Valiakhmetov,
G. V. Gogolev,
N. I. Shunkina,
M. S. Varfolomeev,
G. I. Shcherbakova,
and G. A. Vartanyan
Translated from Novye Ogneupory,No.8,pp.3–9,August, 2016.
Original article submitted May 19, 2016.
Silica-free binder ALUMOX is tested under conditions of the AO NPTs Gas Turbine Construction Salyut
casting shop conditions. A method is developed for preparing composite ceramic molds for investment casting
of critical superalloy components by directional solidification. Use of these molds makes it possible to prepare
castings by high-gradient directional solidification answering component drawing specifications and technical
conditions. The protective layer of the composite mold based on ALUMOX binder significantly reduces
chemical interaction of the mold working layer with components of superalloy ZhS26-VI during pouring and
cooling compared with the degree of interaction of a standard mold based on ÉTS-40 binder.
Keywords: silica-free binder ALUMOX, combined ceramic mold, superalloys, directional solidification.
A new generation of nickel-base superalloys brings for-
ward special requirements for component casting technology
with directional solidification: shell mold heating to 1700°C,
deformation stability, inertness towards a melt at high tem
perature, and prolonged contact of melt with a shell mold
[1, pp. 462 – 474; 2]. In mass production during casting aero
engine components ceramic molds are used prepared by
layer-by-layer deposition of refractory coating by generally
accepted technology; dipping – sprinkling – layer-by-layer
drying. Cast component quality depends on mold quality,
which is provided with use in manufacture of refractory ma
terial suspensions: binder and filler. Siliceous binders are
used currently in casting workshops. For example, hydro
lysed ethyl silicate (ÉTS-40) of Russian production [1 – 3],
and also silica gel (water-based binder grade Ludox SK from
Dupont, USA, and grade Primcote Plus from Ransom
Randolph, USA .
With use of ethyl silicate ceramic molds for casting gas
turbine engine (GTE) blades it is necessary to consider for-
mation of burn-on and casting geometry instability, which
leads to a requirement for increasing casting tolerances. Tol
erance is subsequently removed by sand blasting treatment
and metal cleaning, as a result of which at the surface of sin
gle-crystal blades there is formation of a recrystallized layer.
It should also be noted that with use of silica molds a consid
erable amount of silicon compounds forms on superalloy that
prevents use of recycled charges in preparing critical compo
nents, and requires carrying out an expensive procedure for
alloy refining, which significantly affects casting cost.
Practice has shown that use of molds with the binders in
dicated above is expedient in casting superalloys in the pro
cess of preparing components with an equiaxed structure, for
example alloy ZhS6U-VI with a pouring temperature of
In these cases the temperature of casting mold warm-up
before pouring is low and is 950 – 1050°C, mold strength is
adequate, and the working surface is hard and smooth. Mold
material sintering is provided by formation of a glass phase
from silica binder and impurities of electrocorundum filler,
and correspondingly depends on the degree of suspension
Refractories and Industrial Ceramics Vol. 57, No. 4, November, 2016
1083-4877/16/05704-0335 © 2016 Springer Science+Business Media New York
AO NPTs Gas Turbine Construction Salyut, Moscow, Russia.
GNTs RF AO GNIIKhTÉOS, Moscow, Russia.
FGBOU VPO D. I. Mendeleev Russian Chemical Technology
University, Moscow, Russia.