Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 5, pp. 851−856.
Pleiades Publishing, Ltd., 2009.
Original Russian Text
V.I. Balakai, V.V. Ivanov, I.V. Balakai, A.V. Arzumanova, 2009, published in Zhurnal Prikladnoi Khimii, 2009, Vol. 82, No. 5,
AND CORROSION PROTECTION OF METALS
Analysis of the Phase Disorder
in Electroplated Nickel–Boron Coatings
V. I. Balakai, V. V. Ivanov, I. V. Balakai, and A. V. Arzumanova
South-Russian State Technical University (Novocherkassk Polytechnic Institute), Novocherkassk,
Rostov-on-Don oblast, Russia
Received December 11, 2008
Abstract—Probable state of the phase disorder in electroplated nickel–boron coatings was analyzed. The
electrical resistivity of the coatings and the microhardness and wear resistance of their surface was modeled.
The calculated parameters of the nickel–boron coatings were analyzed in comparison with the corresponding
The high cost of noble metals (silver, gold, platinum,
etc.) as materials for electric contacts restricts their
use in electronic devices. At present, it is suggested
to fabricate low-current sliding contacts that switch
low-power currents under sliding friction conditions
from nickel-based alloys having a comparatively low
and stable-in-time contact electrical resistance, high
electrical conductivity, and enhanced corrosion stability
and mechanical wear resistance [1, 2].
A promising alloy for use in low-current sliding
contacts is an electroplated nickel–boron alloy [1–3].
Despite that the resistivity and the contact resistance
of a nickel–boron electroplated coating (EC) is 1.4–1.8
times lower than those of electroplated silver, their wear
resistance and microhardness of nickel–boron coatings are
4.5–5 times those of silver . The corrosion resistance
of nickel–boron ECs exceeds that of nickel by a factor
of 2.0–2.5. The experimentally recorded improvement
of the electrical and mechanical properties of thermally
treated nickel–boron ECs, compared with nickel, was
attributed in  to formation of boron-containing phases
B and Ni
B. However, the higher, compared with
nickel, resistivity and the nature of the dependence of this
quantity on the boron content of a coating indicate that
the phase composition is not the only factor determining
the electrical properties of ECs.
In this context, analysis of the qualitative and
quantitative phase composition of thermally treated ECs,
performed with allowance for the possible chemical
modiﬁ cation processes and the distribution of phases
throughout the coating volume, is necessary for a more
precise interpretation of the known experimental data.
It is noteworthy that the analytical method for solving
this phase problem for ECs is nearly the only possible,
as, e.g., in the case of ECs subjected to a tribological
treatment [4, 5].
An analysis of the probable state of the phase disorder
in thermally treated nickel–boron ECs, a modeling of the
resistivity, microhardness, and wear resistance, and the
subsequent analysis of the phase disorder on the basis of
experimental evidence about the corresponding properties
of the coatings is the aim of this study.
We deposited electroplated coatings based on the nick-
el–boron alloy from a chloride electrolyte of composition
): nickel chloride hexahydrate 200–300, nickel
sulfate 2.5–5.0, boric acid 25–45, chloramine B 0.5–1.5,
potassium dicarboundecarborane 0.5–4.0, at pH 1.0–5.0,
temperature of 18–40°C, and cathode current density of
0.5–9 A dm
[6, 7, 8].
In accordance with , we name the state of a nickel–
boron EC that is spontaneously formed under the action
of external factors (thermal treatment, triboactivation)
through chemical modiﬁ cation and physicochemical