ISSN 1070-4272, Russian Journal of Applied Chemistry, 2014, Vol. 87, No. 6, pp. 730−733. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © K.V. Murzenko, V.I. Balakai, 2014, published in Zhurnal Prikladnoi Khimii, 2014, Vol. 87, No. 6, pp. 738−741.
AND CORROSION PROTECTION OF METALS
An important role in improving the quality, reliability,
and durability of articles is played by galvanic coatings
that protect metals and alloys from corrosion, reduce the
friction coefﬁ cient of working surfaces, raise the wear
resistance and microhardness, and improve the adhesion,
outward appearance, and other properties of coatings.
Growing require ments to the reliability of equipment
under increased loads and need to protect articles from
corrosive media predetermine the increasing interest in
application of composite electrolytic coatings (CECs).
The application efﬁ ciency of CECs is largely deter-
mined by the nature and particle size of the dispersed
phase. Solid particles with sizes, as a rule, not exceeding
3–5 μm, but occasionally constituting several tens of
micrometers are introduced as the dispersed phase into
electrolytes. Composite coatings modiﬁ ed with nanosize
particles have been increasingly actively studied recently.
In contrast to ordinary ﬁ nely dispersed powders, nanopar-
ticles are more like speciﬁ c structure-forming elements,
rather than ﬁ llers.
Dispersed particles present in an electrolyte in the
suspended state are in continuous contact with the cathode
surface and their reinforcing effect is manifested both at
the instant of capture (overgrowth) by a metal and in an
impact on the cathode surface. At the instant of impact,
a particle shields the cathode by the contact surface and
thereby distorts the structure of the original electrocrys-
tallization of the metal. In this case, there occurs full or
partial loss of kinetic energy by a particle, which depends
on its velocity and angle of contact with the cathode and
leads to the strain-hardening or grinding-polishing effect
(cutout of surface microprojections). In the process, as
also in the case of particle “capture” by the metal, the
structure of a coating becomes more complex and it is
strengthened. The degree of metal strengthening depends
on the number of contacts between particles and the
cathode, and on their nature, size, density, and velocity.
The effect of the crystallographic form of particles
and their nature and size is manifested at the instant of
their capture by the metal. The smaller the particles and
the stronger the distortion of the crystal lattice of the
material and the crystallographic form of particles, the
easier their capture by the metals due to the microscopic
surface irregularities. The nature and size of particles
Dependence of Physicomechanical Properties
of a Nickel–Cobalt–Aluminum Oxide Composite
Electrolytic Coating on the Dispersity
of the Alloying Component
K. V. Murzenko and V. I. Balakai
Platov South-Russian State Polytechnic University (NPI),
ul. Bogdana-Khmel’nitskogo 141, Novocherkassk, Rostov-on-Don oblast, 346428 Russia
Received April 25, 2014
Abstract—Effect of the dispersity of aluminum oxide on the microhardness, wear, internal stresses, and porosity
of nickel–cobalt–aluminum oxide composite electrolytic coatings deposited from a chloride electrolyte and the
dependence of the content of aluminum oxide in the coating on the agitation rate and working duration of the
electrolyte were studied.