Note: Descriptions are shown in the official language in which they were submitted.
:~98131
The invention relates to a composite material containing
hard metal carbide particles. Further, the invention relates
to a method for producing such composite material and for
production of a body consisting of such material.
Composite materials containing particles of hard metal carbide
(such as tungsten carbide, titanium carbide and molybdenum carbide)
bonded together by a softer binder have been used over already
a long period in the manufacture of oil field drill bits, machine
tools and similar articles which are subjected during operations
to considerable erosion and/or wear such as abrasive and/or mechanical
wear.
Such composite ~aterials are normally produced by placing hard
metal carbide particles in a suitable mould, vibrating the mould to
obtain a closely pa,cked mass of particles therein, adding pellets of
a binder metal capable of wetting the metal carbide particles in the
molten state, and thereafter heating the mould and its contents to an
infiltration temperature above the meltine point o~ the binder metal.
As it approaches this temperature, the molten binder flows downwardly
into the interstices between the metal carbide particles. As a result
thereof, a bond is formed at the surfaces of the particles between
the binder and the particles. The composite material obtained after
cooling and solidification of the binder consists of a mass of
particles bonded together by a continuous binder phase. Since
the particles have a high density and are moreover closel~ packed,
the composite material thus obtained is of high density. These
materials generally show a good resistance against erosion as
well as against mechanical and/or abrasive wear.
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However, compsite ma~eTials have at present to be used under extreme
conditions where tlle available types of materlals fail to meet the require-
ments on resistance against erosion and/or wear.
An object of the invention is a composite material that shows
a remarkable resistance against erosion and/or wear.
A further object of the invention is a method for the production
of such a material.
According to the invention, such method comprises the steps of
filling a mould with a mass of hard metal carbide particles of a first sieve
fraction, vibrating the mould to compact the mass of particles, adding on top
of the compacted mass of particles a mass of hard metal carbide particles of
a second sieve fraction, the particles of the second sieve fraction being
smaller than the particles of the first sieve fraction to an extent sufficient
to allow them to infiltrate the interstices of the compacted mass of particles
of the first sieve fraction when vibrating the mould, vibrating the mould to
infiltrate said interstices with the particles of the second sieve fraction,
and thereafter infiltrating the interstices of the mass of particles thus
compacted with a molten binder, and cooling the mould and the contents there-
of, wherein prior to adding the particles of the second sieve fraction a
perforated plate is pressed on top of the compacted mass of the particles
of the first sieve fraction.
The first sieve fraction may be between 100 mesh and 3 mesh,
whereas the nominal diameter of the particles of the second fraction may be
between 10 3 millimetres and 0,5 millimetres. By "nominal diameter" of a
particle is herein to be ~mderstood the diameter of a sphere having the same
volume as the particle.
In an attractive embodiment of the invention, the first sievc
fraction is between 20 mesh and 10 mesh, whereas the second sieve fraction
is between 270 mesh and 100 mesh.
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The smallest particles of the first sieve fraction may have
a size that is at least four times the size of the largest
particles of the second sieve fraction.
A third, fo~rth or even a fifth sieve fraction may be used.
Each following sieve fraction consists of particles that are smaller
than the particles of the preceding sieve fraction. The smallest
particles of the se~ond sieve fraction may have a size that is at
least three times the size of the largest particles of the third
sieve fraction.
For improving the degree of compaction of the particles,
the mould may be vibrated horizontally and consecutively in a
plurality of directions.
The composite material obtained by the method according
to the invention comprises a compacted mass of large-sized
particles of the first sieve fraction, said mass having the
interstices thereof filled up with a compacted mass of
small-sized particles of the second sieve fraction. The volume
not occupied by particles i8 filled up by metal binder.
The composite material of the invention shows an extremely
high carbide-density since the consecutively compactin~ of two
separate sieve fractions of particles leads to an extremely high
final compaction, which may well be over 80%. This material with
high carbide-density has been found to show an improved resistance
to erosion as compared to composite materials having the hard metal
carbide particles incorporated therein belonging to a single sieve
fraction only.
8~31
A body of composite material according to the invention
and havine a wall with large resistance to abrasive and/or
mechanical wear may be obtained by grinding at lea~t part of
that wall of the composite material body that has faced a wall
of the mould, ove~ a depth equalling about 10 to 50% of the
mean value of the widi;hs of the maximum mesh and the minimum
mesh of the first sieve fraction. The ground surface exposes a
cro6s-section over particles, the area of the cross-section
being at least 75% of the area of the surface. It will be
lo appreciated that this large percentage of` the area occupied
by the hard metal increases the resistance to erosion and
wear to a great extent. Consequently, such surface is ideal
for forming a slidable barrier between two zones of different
pressure, as is required in pumping equipment, etc.
The invention will now be described by way of example
in more detail with reference to some EXAMPLES and to the
arawing which shows a magnification of a top view on a surface
of a composite material according to the invention.
Where the fractio~ of the particles are within the ASTM-range,
they are indicated in this range. In those cases where one of the
boundaries is outside the ASTM-range, the boundaries will be
indicated by the nominal diameter of the smallest and the largest
particle of the fraction. By "nominal diameter" of a particle
is herein to be understood the diameter of a ~phere having the
same volume as the particle.
Further, it will be appreciated that without departing from
the scope of the invention, a small percentage (say 5 to 10%) of
the particles of a fraction may be outside the fraction boundaries
indicated.
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~C~98~3~L
EXAMPLE I
A mass Or tlmesten carbide particles of a first sieve fraction
ranging from 20 to 1~ mesh, and weighing 265 grams is deposited
in a mould consisting of compressed carbon powder (and having
an inner volume of about 27 cm ).
After the mould has been filled with the particles, the
mould is horizontally vibrated at about 50 vibrations/second
during about 5 minutes. The main direction of vibration is
varied several times during this vibration operation, which
finally results in an apparent density of the mass of particles
(also referred to as tap density) of about 58%.
Subsequently, a mass of tungsten carbide particles of smaller
dimensions (sieve fraction ranging from 120 to 100 mesh) and
weighing 70 grams is deposited on the compacted mass of relatively
large particles, and the mould is again horizontally vibrated during
about 30 minutes. The direction of vibration is changed several
times and the small-sized particles enter into the interstices of
the already compacted mass of large-sized particles. Since the
vibration movements are in a horizontal plane, the already compacted
mass stays compacted and the small-sized particles are distributed
over the interstices of the large-sized particles and form a compacted
mass therein. The apparent density of the compacted mass of tungsten
carbide particles thus obtained is found to be ~5%. It is observed
that the smallest particles of the first sieve fraction have a size
that is at least four times the size of the largest particles of the
second sieve fraction.
The mould with the particles is thereafter placed in a furnace,
whereafter a metal binder (consisting of a composition of Ag, Cu, Zn and
Cd and having a temperature of 650 C) is allowed to flow into the
1~98131
interstices of the particles (said interstices having a volume
of 25%). Upon removal Or the mould from the furnace, the
composite material is allowed to coo] down, whereafter the
body i.s removed from the mould. The composite material
has a density of about 14.2. The resistance to erosion is
testecl by impingement of a hieh velocity mud jet perpend.icular
to the surface of the body during a pre-determined time interval.
The susceptibility of the body aeainst erosive action is defined
by the depth of the hole resulting f.rom the jet action.
Test data: jet nozzle diameter3 mm
distance between body and
nozzle outlet 3 mm
pressure drop over nozzle 155 ke/cm2
ambient pressure45 kg/cm
exposure time15 minutes
Mud composition: 1000 litre water
400 kg Limburgia (sand)
60 kg bentonite
Test result : average hole depth 0.35 mm
.
EXAMPLE II
A moul~ filled with compacted tungsten carbide particles having
sieve fractions ranging between 14 and 10 mesh (first sieve fraction),
and between 60 and 50 mesh (second sieve fraction) is made up in
the manner described with reference to EXAMPLE I. Since the size
of the smallest particles of the first sieve fraction is more than
four times the size of the largest particles of the second sieve
iO98131
fraction, infiltration time of the second sieve fraction into
the compacted first sieve fraction is not excessively long.
Prior to heating the mould and its contents, a third amount
of tungsten carbide particles of a sieve fraction from 2~0
to 200 mesh is infiltrated by vibration into the interstices
of the compacted particles of the other two fractions. Since
the size of the smallest particles of the second sieve fraction
is more than three times the size of the largest particles of
the third sieve fraction, infiltration time will not be too
long. The mould is vibrated horizontally in various directions,
and an interstice volume is reached that is 20-15% of the total
volume of the packed particles. AYter heating and addition of
molten binder (a Cu-Mn12 composition), a specific density of
about 15 of the body of composite material is obtained. Erosion
tests carried out in the manner described with reference to
EXAMPLE I gave an average hole depth of 0.25 mm.
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EX1~PLE _II
The body of composite material described in this example
is in particular adapted for use at locations where high requirements
are set for the resistance against abrasive forces. Such body
is manufactured by grinding a wall (such as the bottom surface)
of the body of composite material obtained by the method described
in EXAMPLE II. The bottom surface of the body has faced the bottom
of the mould during the period over which the mould has been vibrated.
As a result of such vibration, the particles of the first sieve fraction
are positioned on the bottom of the mould in a manner such that
the degree of contact between the surfaces of these particles is
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i~98~31
highest in the region that is situated at a distance from said
bottom that is between 10 and 50% of the mean value of the widths
of the maximum mesh and the minimum mesh of the first sieve fraction.
Thus by grinding the bo~tom surface of the body away over a depth
that is between 10 and 'jO% of said mean value, the cross-sectional
~urface thus exposed shows a relatively laree area thereof occupied
by cross-sections of th~ large-sized tunesten carbide particles.
A ~agnification of a top view of this surface is schematically shown
in the drawing. Particles of the first sieve fraction are indicated
by reference numeral 1, whereas particles of the second and third
sieve fractions are indicated by numerals 2 and 3, respectively.
In this example, the surface has been ground over a depth
of about 20% of the said mean value. The area of the cross-sections
of the particles 1 forms 78% of the total area of the ground part
of the body surface. Further, 12% of the total area is formed by
the cross-sections of the particles 2 and 3, whereas the remaining
10~ is a cros~-section over the bind0r metal.
It will be appreciated that a surface comprisin~ such an
extremely large carbide area will show an excellent resistance
against abrasive and/or mechanical wear. Such surface will therefore
be useful for application in equipment comprising surfaces that
should form a slidable seal to separate zones of different pressure
and containing abrasive fluids.
Further, the resistance to erosive action of the ground surface
is extremely high. An average hole depth of 0.25 mm was measured
under test conditions equal to those,described i.n Example I.
10913131
Improved resistance against abrasive and/or mechanical
wear of a surface of a body according to the invention may
also be obtained by grinding a surface or a plane other than
the 6urface or plane of the body that has faced the bottom of the
mould thereof. However, the top plane is not suitable for this
purpose. These other planes or surfaces are then ground over a
depth equal to 10-50~ of the mean value of the widths of the
maximum mesh and the minimum mesh of the first sieve fraction,
in the same manner as described with reference to the bottom
surface. However, the results obtained are not as good as
reached when grinding the bottom plane or surface over an
equal depth.
~.e improved resistance to erosive action of the composite
material according to the invention is made clear by the tests
referred to in the examples. It is believed that this improved
erosion resistance may be explained as follows. As a result of
the consecu~ive compaction of the ma~ses of particles of
diminishing particle sizes, a high carbide density and consequently
a small pore volume is obtained However, the number of pores
has increased greatly by the use of the particles of the second
and further sieve fractions, The individual pores have a slender
configuration, and consequently any liquid jet trying to dislodge
particles from the mass that is bonded together by the binder
metal in the pores, has to erode this binder metal from slender
pores, which due to this configuration destroy the jet-energy
before the jet can protrude beyond the separate particles to
dislodge them from the composite material. The erosion of
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~9813~
the metal binder then 6tops and the resistance to erosion is
solely dictated by ~he hard metal partic]es.
The resistance to erosion of a composite material differing
from the material of EXAMPLE I only in that the hard metal particles
were o~ a sieve fractio~ between 120 and 18 mesh was found to be
considerably lower than the erosion resistance of the material
according to EXAMPLE t. It is observed that this single sieve
fraction spans all particle sizes between the smallest mesh size
of the first sieve fraction and the largest mesh size of the
second sieve fraction of the particles applied in EXAMPLE I. The
particles of this single sieve fraction were compacted in the
mould by vertical vlbration. Comparative erosion tests showed an
average depth of about 3 mm of the single sieve fraction material
against 0.35 mm of the EXAMPLE I-material.
Similar low erosion resistance was found in a body made of a
composite material comprising the sieve fractions as used in
EXAMPLE III, which sieve ~ractions, however, had been vertically
vibrated in the mould simultaneously for compaction purposes.
The area of the ground plane that was occupied by binder metal
was found to be 35% of the total area of the ground plane. The
erosion resistance was found to be about 3 mm in the tests similar
to those described with reference to EXAMPLE III.
All types of hard metals may be applied in the present invention.
The same applies for the binder metal, provided that this metal (or
composition of metals) has the ability to wet the surfaces of the
particles, to infiltrate into the interstices thereof, and to form
a bond with the particles. ~he melting temperature should be sufficiently
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~09~3131
low to prevent destruction of the desirable properties of the
hard metal. Also, if the composite material should be applied
for hard surfacing metal bodies, the above properties of
the binder metal should also apply to the metal or metal
compositions of which the metal body is made.
One important advantage of the extremely high grade of
compaction that can be obtained by the method of the invention
should still be mentioned. This advantage relates to the
extremely low amount o.~ shrinkage of the composite material
that occurs during cooling down of the mould. This may
be explained by the following. The metal binder has a large
coefficient of contraction when cooling down and therefore
induces reorientation of the particles in those composite
materials wherein the large-sized particles are inadequately
compacted. In the composite material of the present invention,
however, these particles are compacted in such a manner that
they are immobile. Moreover, per unit length, only a small
number of large-sized particles will be in contact with each
other. Consequently no significant re-orientation of the large-
sized particles will occur during cooling down of the binder
metal and shrinkage will be negligible.
A composite material with an attractively low shrinking
coefficient will be obtained when applying large-sized particles
in the first sieve fraction that are larger than about 0.3 mm
(5 mesh) .
A hard composite material with low-shrinking coefficient
will be extremely useful in forming an abrasive resistant outer
body layer of a diamond bit, in which layer diamonds have to be
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1~98131
placed, Damage of dianonds by crackin~ due to shrink of the
body layer during manufacture is then obviated. The life of the
diamonds will further be prolonged by applying a binder material
with low melting temperatures. Such composite material will be
described in the following example.
EXAMPLE IV
Tungsten carbide particles of a first sieve fraction between
18 and 14 mesh are vibrated horizontally in a mould made of
compressed graphite. Diamonds have been glued in the mould at
appropriate places prior to vibrating the mould. The mould
is vibrated horizontally in a direction that is varied several
times to increase the degree of compaction of the particles.
Subsequently, a perforated plate (or sieve) is pressed on the
upper surface of the particles in the mould, the perforations
having a diameter of a size between the first and the second
sieve fractions. A batch of small-sized tungsten carbide particles
of the second sieve fraction i~ then placed on the plate, and the
assembly is vibrated in a plurality of directions consecutively,
these directions not particularly lying in a horizontal plane.
The small-sized particles (of a sieve fraction between 80 and
60 mesh) infiltrate into the interstices of the compacted mass
of relatively large-sized particles, until the desired degree
of compaction is obtained in the interstices. The remainder of the
small-sized particles left on top of the perforated plate is
thereafter removed (together with the plate), and a metal binder
consisting of a composition of silver, copper, zinc and cadmiu~ is
subsequently placed in small lumps on the top of the particle
pack in the mould. Heating the mould and its contents in a furnace
up to a temperature of 670 C and subsequent cooling results in a
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31
body of composite material having the diamonds embedded therein
and showing no si~nificant shrinkage.
Coatine on the particle surfaces by nickel, copper or cobalt
is imperative to reach the required bond between the particles
and the binder metal. In this particular example, the particles are
coated by a nickel layer of about 0.2 micron by an electrolytic
process. However, the invention is not considered to be
limited to such a manner of coating.
The properties of the diamonds are not negatively affected
by applyine the present technique of producine a matrix material,
since the material did not show shrink during its manufacture
which manufacture moreover took place at a moderate temperature
(below 800 C).
The method according to the invention further includes the
application of additional sieve fractions (say a fourth and a
fifth sieve fraction) of diminishing particle sizes, that are
consecutively added to the compacted mass of particles of larger
size, me particles of each followine sieve fraction should be
smaller than the particles of the preceding sieve fraction and
be chosen to infiltrate the interstices of the preceding sieve
fractions upon vibration of the mould with a reasonable time.
Further, the hard metal carbide particles used may
be a mixture of different compositions. Also, the compositions
of the various sieve fractions may differ from each other.
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iO98~31
Finally, an erosion-resistant, abrasive material can be
obtained by application of the present invention by replacing at
least part of the hard metal carbide particles of the second
(and/or a further) sieve fraction by diamond particles of sizes
that are within the range of said sieve fraction( 8 ) . The diamond
particles are then distributed by vibration over the interstices
of the compacted mass of hard metal carbide particles of larger
dimensions and the body obtained after infiltration with a molten
binder followed by cooling, will in addition to abrasive properties,
~lso show a resistance against erosion. This allows the body when
applied for cutting purposes, to be subjected to the erosive action
of high-velocity liq~id jets for cooling and removal of cuttines
from the cutting edge of the body.
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