ISSN 1068-798X, Russian Engineering Research, 2018, Vol. 38, No. 2, pp. 91–93. © Allerton Press, Inc., 2018.
Original Russian Text © I.I. Emaev, N.K. Krioni, R.G. Nigmatullin, L.Sh. Shuster, 2017, published in Vestnik Mashinostroeniya, 2017, No. 11, pp. 37–39.
Properties of Plastic Lubricants Modified by a Carbon Framework
I. I. Emaev*, N. K. Krioni, R. G. Nigmatullin, and L. Sh. Shuster
Ufa State Aviation-Engineering University, Ufa, Russia
Abstract—By introducing active additives, a carbon framework may be created within plastic lubricant based
on cylinder oil. The inf luence of such additives on the lubricant properties is investigated, at different tem-
Keywords: plastic lubricant, carbon framework, critical load, wear spot, adhesive strength, pressure, tem-
In moving couplings, lubricant reduces the fric-
tion, reduces the wear, and prevents seizing. In many
mechanisms today, plastic lubricant is employed.
Such lubricant is strongly retained at the frictional sur-
faces and is not dislodged by inertial forces . The
benefits of plastic lubricants may be attributed to their
structure and composition. They consist of highly
structured thixotropic dispersions of solid thickener in
liquid . The thickener forms a framework that
retains the disperse material.
As a rule, plastic lubricants consist of three compo-
nents: oil (the dispersion medium), thickener (the
disperse phase), and additives (oil-insoluble additives,
solid additives, and composites). Research shows that
if the dispersion medium is very viscous oil—for
example, cylinder oil —the plastic lubricant may
operate without thickener. Such plastic lubricants are
sometimes known as hydrocarbon lubricants; the
thickener consists of the solid hydrocarbons (such as
paraffins) present in the oil.
The use of a carbon framework as an additive,
instead of molybdenum disulfide, improves the
antiscratch properties without changing the antiwear
characteristics of the plastic lubricant, as shown in .
The carbon framework is a byproduct obtained in oil
processing and contains elements such as aluminum,
sulfur, chlorine, and carbon, in bound form. Those
elements improve the antiscratch and antiwear prop-
erties. However, it remains unclear how important it is
that the elements are present in the frictional zone in
the bound state (as composites), rather than in the
In the present work, we investigate the tribological
characteristics of plastic lubricant modified by a natu-
ral carbon framework and an artificial carbon frame-
work, taking account of the pressure and temperature
at the contact surfaces.
The antiscratch and antiwear properties of plastic
lubricants are determined on a four-ball machine for
tribological testing, in accordance with State Standard
GOST 9490–75. The antiwear properties are assessed
in terms of the diameter D
of the wear spot, calcu-
lated as the mean for the wear spots on the three lower
balls after operation for 1 h with a load F = 0.4 kN.
The lubricant performance is assessed in terms of
the antiscratch properties: the critical scratching load
, the welding load P
, and the scratch index I
The adhesion between the frictional surfaces is
investigated on the apparatus in . To determine the
dependence of the adhesive strength τ
on the pressure
in mobile frictional contact of the frictional pair, we
gradually reduce the load from the maximum, corre-
sponding to plastic deformation in the contact zone, to
the minimum possible, within the limits of measure-
The samples investigated are steel 45 disks (diame-
ter 20–25 mm, thickness 5–7 mm); the indenters are
cylinders (diameter 5 mm) with spherical ends (R
2.5 mm). The surface roughness is Ra = 0.2–0.4 μm.
The VK8 alloy indenter (a sphere of radius 2.5 mm),
compressed by plane samples, rotates around its axis.
The contact zone is heated by an electrocontact
As the research shows, reliable τ
values (at differ-
ent pressure and temperature) are obtained by repeat-
ing the experiment two or three times. The discrep-
ancy is no more than 5–8%. Before each experiment,
the surfaces of the samples and the indenter are
decreased by means of technical alcohol and a layer of
the plastic lubricant is applied with a brush. All the
experiments are repeated three times, and the mean is