Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to abrasive materials
and more specifically to abrasive materials with coated grains.
The invention can be advantageously used for process
ing diamonds and other hard-to-treat materials by the grains of
an abrasive material in a free state, as well as for manufactur-
ing abrasive tools based on organic, ceramic and metal adhesives.
At present, for grinding, dressing, cutting and boring
purposes tools are used made of various abrasive materials the
grains of which have a coating on their surface.
It is well known that the binder in an adhesive does
not always ensure strong binding of abrasive particles in the
matrix, therefore, various coatings are applied to the surface
of abrasive particles.
Such coatings must meet a number of requirements.
First, the coating must be strongly bound with the
surface of an abrasive.
Such binding is ensured only by the chemical interaction
between the components of said coating and abrasive. The energy
-~ of such interaction may amount to tens or even hundreds of grand
calories, whereas the energy of the physical interaction (the
Van der Walls forces) amounts to fractions or units of grand
calories.
Second, the coating must enhance the strength of an
abrasive grain, especially when the grain is in a free state.
It is also known that the strength of an abrasive
material can be increased through greater plasticity of the
coating, as can be inferred from the Griffiths-Irwin-Orovan theory:
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: ~e ~ = (6~-~ fGye)
( ~e ~ - ultimate breaking load)
where ~ -~ - the surface energy of a solid body on the
boundary with a medium, erg ; ;~
cm
~p e - the energy of plastic flow, erg
- cm2
- hal-length of a crack nucleus;
~- E - modulus of elasticity.
Third, the material of said coating must be conducive
to an increase in the efficiency of the surface of the material ~-~
being treated.
As it follows from the Griffiths theory, the breaking
load for the material being treated depends on the value of its -
free surface energy ~5-~ . This value can decrease under
the action of chemical reactions occurring at the interface
between the material being treated and the abrasive material,
which leads to an increase in the efficiency of processing the
surface of the material to be treated. - ~ ;
Fourth, the material of the coating must interact ~
chemically with the components of the binder (a mass meant for -
binding abrasive particles in the process of manufacturing a -
tool which mass, toge~ther with said-particles, forms the body
- of said tool-matrix). The interaction must occur at temperatures,
under pressures, and in media, which are envisaged by the tool-
making technological processes. At the same time, the physical-
mechanical properties of th`e matrix must not deteriorate.
; The coating must be corrosion- and heat-,resistant,
and must preserve its initial properties in long-term storage.
The process of producing such coatings must be easily effected,
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without using complicated equipment and costly materials.
- Metals and non-metals, t'heir carbides, borides or
oxides, or their mixtures can be used as grain coatings.
It is known that coatings applied to diamond grains
' consist of one or several metals c'hosen from the group' ~i, Co,
Ag, Cu, Mo, Ti, Al, Mu, Cd, Sn, Pb, Zn, Cr, Au, W, Tn, Fe,
Zr, Pt,'Ro, Pd, or alloys and mixtures thereof which contain
at least one of said metals.
Said coatings, however, are inadequate, as they are
insecurely bound with the surface of diamond grains because
metals are applied to diamond at low temperatures (160-200C).
In this case, no chemical bond is formed. The metallic film
is kept on the surface of said diamond grain mechanically
due to the microroughness of the diamond or by the weak forces
of the physical interaction.
Diamond grains with said coatings are used in discs
where only resins (organic adhesives) act as binders. In spite
of a certain improvement in the interaction between the coating
material and the binder (as compared to a pure uncoated diamond),
the effect of increasing the durability of holding the diamond
grains in the matrix is not great because of a poor cohesion
between the diamond and said coating.
Known in the art is a method for metallization of
abrasive grains, which consists in applying a coating of silicon
or such metals as: Fe, ~i, Be, B, Co, Nb, Cr, Mo, or alloys ;
such as: Fe-~b, Fe-Cr, Fe-V, Fe-Si, by way of evaporation coating,
cathode sputtering or decomposition of carbonyls of correspond-
ing metals.
However, evaporation coating of metals is applicable
on an industrial scale for a limited number of metals, chiefly
fusible metals.
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Cathode sputtering is difficult to control and regulate
and demands the use of complicated equipment, therefore, it
- is not economical in large-scale production.
The use of metal carbonyls for the purpose necessitates
strict accident-prevention measures, which considerably adds
up to the cost of the metallization process.
- Known in the art are abrasive materials whose grains
have at least a two-component coating comprising silicon. The
other component of this coating is carbon.
When applying such coating to diamond grains, the
latter are placed in a gas medium which contains volatile
compounds of silicon, for example, cyanogen chloride, and of
carbon, for example, methane.
Silicon carbide is formed as a result of the reaction
between said compounds and deposits itself on the diamond sur- -
face. In this case, the formation of strong chemical bonds
between the coating and diamond is impeded, as in the deposited
compound the silicon is already chemically bonded with the
carbon, therefore all the bonds are saturated, and the possibi-
lity of silicons reacting with the diamond carbon is but small.
Also known in the art is an abrasive material the grains
whereof have at least a two-component coating which includes `-
silicon and at least one more metal chosen from the group con-
sisting of copper, silver, gold, aluminium and transition metals
of the 4th-8th groups of the periodic system.
Silicon is known to actively interact with diamond, the
wetting angle is close to zero, and addition of small quantities
(up to 5 weight percent 3 of silicon to metals (Cu, Ag, Ni,
Al, Sn, etc). which insufficiently wet the diamond, sharply
improves the wetting of the diamond surface (the wetting angle
diminishes from 120 to 5). Therefore, silicon is a suitable
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element ensuring the strength of cohesion between a coating and
diamond.
The selection of a second component from said group
of metals is mainly determined by the components of the adhesive
of a tool.
All the above-mentioned metals chemically interact
with silicon. The diagram of the "silicon - metal" state is well
known. Due to this fact, it is always possible to choose such
components of coating which actively interact with the binder
- 10 of a tool and which possess the required physical-mechanical
- properties.
In this case, the chemical interaction of a coating
with an abrasive is ensured by the presence of silicon in the
coating, while the chemical interaction with a binder is ensured
by the presence in the coating of a second component which has
chemical affinity with the adhesive material.
This abrasive material can be produced by different
methods. ;~
Experience has shown that the most economical method
for producing such an abrasive material is joint caking of the
powders of an abrasive and the components of a coating in
vacuum, resulting in the formation of an alloy liquid phase, ~-
which phase adequately wets the surface of the abrasive, or of
a coating layer formed by solid-phase caking at a temperature
of more than 1,200C, or a coating layer formed by caking at
a temperature of less than 1,200C, but with a silicon content
over 50 weight percent.
Investigations have shown, however, that the heating
of diamond powders above 1,200C in a vacuum of at least 5-10 5
torr reduces the strength of both synthetic and natural
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diamond powders, and the presence in the coating material or
more than 50 weight perecent of silicon leads to an increase in
the brittleness of the abrasive material.
The above factors limit the possibility of producing
an abrasive material by the method of joint caking of powders
of an abrasive material and components of a coating.
The principal object of the present invention is to
provide an abrasive material the grains whereof have a coating
of such a silicon-base alloy that will ensure high plasticity
of the coating and strengthen the abrasive material.
Another no less important object of the invention is
to provide an abrasive material the grains whereof have a coat-
ing of such a silicon-base alloy that will ensure its lower
- melting temperature, as compared to the prior art abrasive
materials.
Still another object of the present invention is to pro-
vide an abrasive material, similar to the above-mentioned
material, but with such coating of its grains that will help
- to increase the efficiency of processing the surface of the
material to be treated, as compared to the prior art abrasive
materials.
These and other objects are achieved by providing an
abrasive material the grains whereof have a coating of a i
silicon-base alloy which comprises, taken separately or in a
combination, copper, silver, gold, aluminium, and transition
metals of the 4th-8th groups of the periodic system, wherein,
according to the invention, the alloy also comprises gallium,
indium, thallium, germanium, tin, lead, phosphorus, antimony,
tellurium and sulphur, taken separately or in a combination,
in a quantity of from 2 to 80 weight percent of the total
weight of said coating.
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We have found that introduction into the coating of
an element chosen from the group consisting of gallium, indium,
thallium, germanium, tin, lead, phosphorus, antimony, tellurium
and sulphur (~usible elements), and taken separately or in
a co~bination in a quantity of from 2 to 80 weight percent of
the total weight of the coating, makes it possible to strength-
en the abrasive material, as this leads to a greater coating
plasticity and, consequently, to a higher abrasive strength,
and also results in a lower melting temperature of the coating
material, which, in turn, increases the durability of said
coating on the abrasive.
In addition, the interaction of said fusible elements
/ with the surface of the material being treated leads to a
reduction in the value of the free surface energy of said
material, which increases the efficiency of processing the ~-
material.
The abrasive material, according to the invention, is
most effective in processing hard-to-treat materials, for
example, diamond, owing to the fact that elements incorporated
in the composition o~ its coating have the ability to accelerate
- chemical reactions on the surface of the material being
treated and to reduce its free surface energy, while the abrasive
- material itself possesses a higher strength, as compared
to the known similar abrasive materials.
By properly selecting alloy components one can substan-
tially improve the characteristics of the material.
The appropriate thickness of a coating varies from
0.01 to 1000 microns.
It is known that the thinner a coating, the lower the ~
stresses occurring in the area of contact between the coating ~;
and abrasive material.
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sesides, the ability of components to react in thin
coating (films), e.g., the diffusion coefficient, is substantially
higher than that in a compact material. Therefore, in the case
when the temperatures specified in the tool-manufacturing
technology are not great ( c 700C) and cannot ensure a sufficient
chemical interaction between the components of a coating and
a binder, ~or example, in manufacturing tools on an organic
binder, the use of thin coatings of the order of 1 mu is
effective.
In case of using abrasive-coated grains for tools the
manufacturing technology of which stipulates the use of liquid
metals (during soaking and baking in the presence of a liquid
phase or duringsoldering), the thickness of coatings must be
- substantially higher than 1 mu.
For manufacturing monocrystal abrasive tools the thick-
ness of a coating must be of the order of 1,000 mu.
For manufacturing a wide range of tools on various
binders made from the proposed abrasivematerial, it is advisable
to use the following experimentally selected compositions
of the grain coating.
: For manufacturing diamond pastes it is recommended to
use an abrasive material with a coating which comprises (in
weight percent):
silicon 20-40
iron 40-60
tin 10-30,
- and which has an optimum thickness of 1 to 20 mu.
Said abrasive material is most effective in treating
hard alloys.
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It has been found experimentally that for making pastes
meant for processing steels it is expedient to use an abrasive
material with a coating which comprises (in weight percent):
silicon 10-50
- titanium 45-85
indium 2-5
and which has an optimum thickness of 0.01 to 1.00 mu, since
these pastes are intended for finishing operations.
For manufacturing diamond cloths meant for processing
steels it is advisable to use an abrasive material with a
coating which comprises (in weight percent):
silicon 64-92
- vanadium 5-30
tin 2-6
and which has an optimum thickness of 1 to 40 mu.
In discs based on an organic binder, it is expedient
to use an abrasive material in the form of coated grains, the -~
coating comprising (in weight percent):
silicon 10-50
molybdenum 45-85
~ sulphûr 2-10 -
~` and which has an optimum thickness of 5 to 150 mu.
For manufacturing discs based on an organic binder,
meant for processing hard alloys, it is recommended to use an
abrasive material with a coating which comprises (in weight per~
cent):
silicon 10-45
manganese 50-85
gallium 2-~
and which is of 100 to 400 mu thick.
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For diamond honing tools an abrasive material is
recommended with a coating which comprises (in weight percent):
silicon 10-50
- cobalt 40-80
phosphorus 5-10
and which is from 50 to 80 mu thick.
For processing hard-to-treat materials, for example
diamond, it is appropriate to use an abrasive material with a
coating which comprises (in weight percent):
silicon 15-70
- nickel 10-80
tin 2-40
and which has an optimum thickness of 0.1 to 10 mu.
For manufacturing tools on a metallic binder it is
expedient to use an abrasive material with a coating which
; compris~s (in weight percent):
silicon 0,3_3,0
copper 17-60
~` tin 30-80
and which is from 50 to 1,000 mu thick. ~ ~ :
For manufacturing tools on a ceramic binder it is
- expedient to use an abrasive material with a coating which
.
comprises (in weight percent):
silicon 20-60
aluminium 10-70
phosphorus 2-30
and which is from 150 to 400 mu thick.
It is expedient that an alloy also contain yttrium,
lanthanum, or cerium, taken in a quantity of 0.01 to 25.00
weight percent.
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~6)65616
Said elements present in the composition of the coating
raise the heat resistance of the proposed abrasive material and
also protectedthe grain of said abrasive from oxidation in the
process of operation in a free state, or in a tool in the case
when high local temperatures appear at the points of contact
between the abrasive material and the material being treated.
Thus, the proposed abrasive material can be effectively
-~ used in processing diamonds and other hard-to-treat materials
by the grains of an abrasive material in a free state, as well
- 10 as for manufacturing abrasive tools on organic, ceramic and metal-
- lic binders, in such a case, the coating for abrasive grains is ~ ~ :
a silicon-base alloy which includes at least one element exhibit-
ing chemical af~inity with the components of the adhesive. -
The abrasive material according to the invention com-
prises a coating of such a silicon-base alloy that ensures its
high plasticity, lower melting temperature and also high heat
resistance, the coating protects the grains from oxidation and
helps to increase the efficiency of processing the surface of
the material under treatment, as compared to the prior art
abrasive materials. ~
- The invention will now be explained in greater detail ~-
with reference to specific examples of its embodiments.
Coating of the grains of an abrasive material can be
effected by any conventional method suitable for the purpose,
however, it is preferable to use the method of joint caking of
abrasive grains and coating components in vacuum.
Example 1.
A coating made of an alloy comprising 30 weight percent
of silicon, 50 weight percent of iron and 20 weight percent of
tin and having a thickness of 10 mu is applied in vacuum to `
the grains of synthetic diamonds by way of joint caking of the -~
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diamond grains and the powdered components of the coating.
The abrasive material thus obtained is used for making
a diamond paste.
The performance of this paste in treating ceramics is ~;
1.5 times higher than that of a paste made from the prior art
abrasive materials.
Example 2.
A coating comprising 12 weight percent of silicon, 85'
weight percent of titanium, 3 weight percent of indium and
having a thickness of 0.01 mu is applied in vacuum to the
grains of natural diamonds by way of joint caking of the dia-
mond grains and the powdered components of the coating.
The abrasive material thus obtained is used for making
a diamond paste. -
The performance of this paste in treating hard alloys
is 20 percent higher than that of a paste made from the prior
art abrasive materials.
Example 3.
A coating comprising 92 weight percent of silicon, 6
weight percent of vanadium, 2 weight percent of tin and having
a thickness of 1 mu is applied in vacuum to the grains of boron
nitride by way of joint caking of the diamond grains and
the powdered components of the coating.
The abrasive material thus obtained is used for making
diamond cloths for treating steels.
The performance of said cloths is 30 percent higher than
that of cloths made from the prior art abrasive materials. ;
Example 4.
A coating comprising 25 weight percent of silicon, 73
weight percent of molybdenum, 2 weight percent of sulphur and
having a thickness of 5 mu is applied in a protective atmosphere
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under a pressure of 1.5 atm. to the grains of synthetic diamonds
by way of caking of the diamond grains and the powdered com-
- ponents of the coating.
The abrasive material thus obtained is used for making
discs based on organic binders.
The performance of these discs is 50 percent higher than
that of discs made from the prior art abrasive materials.
Example 5. ;
A coating comprising 12 weight percent of silicon 82
weight percent of manganese, 6 weight percent of gallium and
- having a thickness of 100 mu is applied in vacuum to the grains
of synthetic diamonds by way of joint caking of the diamond ~ -
grains and the powdered components of the coating.
- The abrasive material thus obtained is used for making
discs based on an organic binder.
The performance of these discs in treating hard alloys -
is 30 percent higher than that of discs made from the prior art
abrasive materials.
Example 6.
A coating comprising 30 weight percent of silicon, 63
weight percent of cobalt, 7 weight percent of phosphorus and
having a thickness of 500 mu is applied in a protective atmo-
sphere under a pressure of 1.5 atm. to the grains of synthetic
diamonds by way of caking of the diamond grains and the powder- `
ed components of the coating. -
The abrasive material thus obtained is used for making
honing tools.
The performance of these honing tools is 50 percent
. higher, than that of tools made from the prior art abrasive
materials.
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11~656~6
Example 7.
A coating comprising 50 weight percent of silicon, 30
weight percent of nickel, 20 weight percent of tin and having a
thickness of 7 mu is applied in vacuum to the grains of synthetic
- diamonds by way of a joint caking of the diamond grains andthe powdered components of the coating. ,
- The abrasive material thus obtained is used for process-
ing hard-to-treat materials, for example, diamond with the
aid of grains in a free state.
The performance of this abrasive material is 1.5 times
higher than that of the prior art abrasive materials. `
Example 8.
A coating comprising 1 weight percent of silicon, 19
weight percent of copper, 80 weight percent of tin and having
a thickness of 1,000 mu is applied in vacuum to the grains of
synthetic diamonds by way of joint caking of the diamond grains
and the powdered components of the coating.
The abrasive material, thus obtained is used for making
abrasive tools on a metallic binder.
The performance of these tools is 40 percent higher
than that of tools made from the prior art abrasive materials.
Example 9.
` A coating comprising 48 weight percent of silicon, 50
- weight percent of aluminium,2 weight percent of phosphorus
and having a thickness of 200 mu is applied in a protective
atmosphere under a pressure of 1.5 atm. to the grains of
synthetic diamonds by way of caking of the diamond grains and
the powdered components of the coating.
- The abrasive material thus obtained is used for making
. .
abrasive tools on a ceramic binder.
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The performance of these tools is 50 percent higher ~-
than that of tools made from the prior art abrasive materialsO
Example 10.
A coating comprising 3 weight percent of silicon, 90
weight percent of chrome, 5 weight percent of tin, 2 weight
percent of yttrium and having a thickness of 10 mu is applied
in vacuum to the grains of synthetic diamonds by way of joint
caking of the diamond grains and the powdered components of
the coating.
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The abrasive material thus obtained is used for making
- discs based on a metallic binder.
- The performance of discs in processing glass is two
times higher than that of discs made from the prior art abrasive
materials.
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