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The necessary conditions for
the use of the RVS Technology® and the control methods of
the physical and user properties of friction pairs with the use of the RVS Technology® The improvement of the
exploitation parameters is not carried out by simply adding RVS
compound in the lubricant of a friction pair but by changing the physical and
chemical parameters of the surface layer of the metal and growing
metalceramic material layer on it. The volume and weight of the metalceramic
formation are in some cases significantly higher than the volume and weight
of the RVS Compound added in the lubricant, which means that the RVS material
is not enough for the construction of the metalceramic layer, and the
surrounding material (organic lubricant and metallic particles from erosion
of the surface) are a constitutional part of the process. Such significant reconstruction
of the surface is possible only if there is long enough a stage of the
reconstruction of the surface, which depends on the materials, lubricants,
temperatures, and pressures on the contact surfaces of the friction pair. The
necessary duration of every concrete case is defined by experience in
accordance with the criterion of the stabilisation of the physical parameters
of the friction pair or the exploitation parameters of the mechanism as a
whole. According to our experience the necessary time for total modification
of the friction surfaces of an internal combustion engine of passenger cars
is 3 to 15 hours (in temperatures of 60ºC< t <80ºC and pressure of
σ > 1.5MPa). The methods and standard tests
used in tribology today are directed to studying the physical
characteristics of the different oil films that are formed on friction
surfaces by using different oils and additives. The use of the methods described
above for testing the RVS Geoactivator is possible only if the following
preparing measures are undertaken: 1. The contact surfaces
of the test parts and the comparative parts are finished at stable load
without the geoactivator until the friction coefficient stabilises on a
certain level and the contact area can be defined 2. The RVS Geoactivator
is added in the area of the interaction of the test parts and it is run in
for 3 to 15 hours at a constant load until permanent friction coefficient
figures can be determined, which means that a monocrystallic layer has been
modified on the surfaces The undergoing of the preparing procedures
is a indispensable precondition of the tests on the RVS Geoactivator. For instance, an FZG test carried out by
Fortum Oil & Gas, Finland, did not give positive results due to the
reason that the recommendations concerning the preparing phase were not taken
into account. The geoactivators are not additives to oils, they do not react
with them, and they do not change their properties. As mentioned above, the
time needed for a full modification of metal surfaces is at least 3 to 15
hours. That is why it is understandable that the time of load stages of the
duration of 15 minutes is simply not enough for the formation process of the
ferrosilicate. We give recommendations for a test focused
on the changes of the friction coefficient that can be carried out in any
type of friction machine with changeable friction pairs. The experimentally detected method
crystallises in the fact that in all tests the nature of the change of the
friction coefficient is similar irregardless of the duration of the test and
the used lubricants. The alteration of the figures of the
parameters of the oils and the test parts (hardness, roughness) affects only
the absolute initial figures of the friction coefficient but not the relative
change of the friction coefficient if
we take the 5-percent accuracy tolerance into account. We have used a friction machine SMTs 2 with
a “roller-shoe” friction pair. The test parts were heat treated after they
were mechanically manufactured to the right sizes, after which they were
mechanically finished so that they had the hardness and roughness figures
that are characteristic of parts installed in real equipment. The
run-in of the friction parts installed in the friction machine is made with
clean oil (without adding RVS compound in it) by smoothly adding the load
from 0 to the nominal load of the test. σ =
(0,25 ÷ 0,5) × σfb, where е σfb
is the fatigue breakdown limit of the steel (alloy) type given in manuals The grinding-in of
every pair is continued until the stabilisation of the friction coefficient
and the contact area. If the gauges of the
friction machine show stable figures for 10 to 15 minutes, and σ = σtest,
the grinding-in of the friction pair is stopped. After the grinding-in
stage a suspension of RVS compound and oil is added to the lubricating system
(dropper, lubricator, etc.) of the friction parts and the registering system
of the friction machine is switched on. When the RVS Geoactivator
is added to the friction area, it can be seen from the curves that the
friction coefficient begins to change within 10 to 20 minutes: sometimes
it rises even by 10 percent for 15 to 20 minutes, but after 2.5 to 3
hours it practically stabilises at a certain figure that is significantly
lower than the initial figure of friction coefficient of the material. |