Note: Descriptions are shown in the official language in which they were submitted.
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POLYCRYS T ALLiNE DIAMOND
S
Field
The invention relates to polycrystalline diamond (PCD) material, a method for
making same and tools comprising same, particularly but not exclusively for
use in boring into the earth.
Background
Polycrystalline diamond (PCD) material comprises a mass of inter-grown
diamond grains and interstices between the diamond grains. PCD may be
made by subjecting an aggregated mass of diamond grains to a high pressure
and temperature in the presence of a sintering aid such as cobalt, which may
promote the inter-growth of diamond grains. The sintering aid may also be
referred to as a catalyst material for diamond. Interstices within the
sintered
PCD material may be wholly or partially filled with residual catalyst
material.
PCD may be formed on a cobalt-cemented tungsten carbide substrate, which
may provide a source of cobalt catalyst material for the PCD.
PCD material may be used in a wide variety of tools for cutting, machining,
drilling or degrading hard or abrasive materials such as rock, metal,
ceramics,
composites and wood-containing materials. For example, tool inserts
comprising PCD material are widely used within drill bits used for boring into
the earth in the oil and gas drilling industry. In many of these applications,
the
temperature of the PCD material may become elevated as it engages rock or
other workpiece or body with high energy. Unfortunately, mechanical
properties of PCD material such as abrasion resistance, hardness and
strength tend to deteriorate at elevated temperatures, which may be promoted
by the residual catalyst material within it.
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Akaisi ll GL at. U L,LtJ5e III the Iivater iall SCieliCe QI RI EilJJ, II,eaI
Mg A (1 9ci~),
volume 05i 4i (Jt , numbers bers i and 2, pages 541 ` to 523, a wail-sintered
diamond
With a 'fi1lP_-flr?i.riP_r! hamorlPC1Pnns minrnsiriirfiire i11/hirh was
sx/nthP__CiR ci al
7 7 (GPa and 9 Q0n degrees centiorarie when diamo d
n nowder with 4 to 5
volume percent Co or Ni additive was used as the starting material.
European patent publication number EP 1 931 594 discloses a method for
producing a polycrystalline diamond (PCD) body with an arithmetic mean as-
sintered grain size less than 1 micron, wherein the catalyst metal comprises
an iron group metal such as cobalt and the sintering pressure is between
about 2.0 GPa and 7.0 GPa.
United States patent application publication number 2005/0133277 discloses
PCD made using a sintering pressure and temperature at 65 kbar and 1,400
degrees centigrade.
There is a need for polycrystalline diamond material having enhanced
abrasion resistance. -
Summary
An aspect of the invention provides a polycrystalline diamond (PCD) material
comprising diamond grains having a mean diamond grain contiguity of greater
than about 60 percent, greater than 60.5 percent, at least about 61.5 percent
or even at least about 65 percent. In some embodiments of the invention, the
diamond grains have a mean diamond grain contiguity of at most about 80
percent or at most about 77 percent. In one embodiment of the invention, the
mean diamond grain contiguity may be in the range from 60.5 percent to
about 77 percent, and in one embodiment, the mean diamond grain contiguity
may be in the range from 61.5 percent to about 77 percent.
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In some embodiments of the invention, the standard deviation of the diamond
grain contiguity may be at Mast about ' percent contiguity, at most about 3
percent contiguity or at most about 2 percent contiguity.
/--. In some embodiments of the `t`ention. the volume of the P D riatnr'Sl "Y'
be at least about 0.5 mm2, at least about 75 mm2, at least about 150 mm2 or
at least about 300 mm2.
In one embodiment of the invention, the diamond grains may have the size
distribution characteristic that at least about 50 percent of the grains have
an
average size of greater than about 5 microns. In some embodiments, at least
about 15 percent or at least about 20 percent of the grains have an average
size in the range from about 10 microns to about 15 microns.
In one embodiment of the invention, the PCD material may comprise diamond
grains having a multi-modal size distribution.
In some embodiments of the invention, the diamond grains may have an
average size of greater than 0.5 microns or greater than 1 micron, and at most
about 60 microns, at most about 30 microns, at most about 20 microns, at
most about 15 microns or at most about 7 microns. In some embodiments of
the invention, the PCD material may comprise diamond grains having a mean
size of at most about 15 microns, less than about 10 microns or at most about
8 microns. In some embodiments of the invention, the diamond grains may
have an average size in the range from about 0.5 microns to about 20
microns, in the range from about 0.5 microns to about 10 microns, or in the
range from about 1 micron to about 7 microns.
In some embodiments of the invention, the content of the diamond in the PCD
material may be at least about 88 volume percent, at least about 90 volume
percent or at least about 91 volume percent of the PCD material. In one
embodiment, the content of the diamond may be at most about 99 volume
percent of the PCD material. In some embodiments of the invention, the
diamond content of the PCD material may be in the range from about 88
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volume percent to about 99 volume percent, or in the range from about 90
volume percent to about 96 volume percent of the PCD material.
in one embo . menf Me PCDD material may corn.-rise cataavst naterria! for
.l:n.rr......-I .-.rxJ .-.~ _.v.hn-l:z........~ 4L._ ~ F.-.rt rf OM.. ....a
i., a .,~ ....i F.-.~
:ei :E.2 ,.. d:.. .,. -i_.-... +
diamond may be at most about 9 volume percent of the PCD material. In one
embodiment, the content of the catalyst material for diamond may be at least
about 1 volume percent of the PCD material. In some embodiments of the
invention, the PCD material may comprise catalyst material for diamond in the
range from about 1 volume percent to about 10 volume percent, in the range
from about 1 volume percent to about 8 volume percent, or in the range from
about I to about 4 volume percent of the PCD material.
In some embodiments of the invention, the PCD may have an average
interstitial mean free path of at most about 1.5 microns, at most about 1.3
microns or at most about 1 micron. In some embodiments of the invention,
the PCD may have an average interstitial mean free path of at least about
0.05 microns, at least about 0.1 micron, at least about 0.2 microns or at
least
about 0.5 microns. In some embodiments, the PCD may have an average
interstitial mean free path in the range from 0.05 micron to about 1.3 micron,
in the range from about 0.1 micron to about 1 micron or in the range from
about 0.5 micron to about 1 micron.
In some embodiments of the invention, the standard deviation of the mean
free path may be in the range from about 0.05 microns to about 1.5 micron, or
in the range from about 0.2 micron to about 1 micron.
In some embodiments of the invention, the PCD material may have a mean
interstitial size of at least about 0.5 micron, at least about 1 micron or at
least
about 1.5 microns. In some embodiments of the invention, the PCD material
may have a mean interstitial size of at most about 3 microns or at most about
4 microns. In some embodiments, the standard deviation of the size
distribution may be at most about 3 microns, at most about 2 microns or even
at most about 1 micron.
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III one eI I IUUUII I iei IL UI LI IG II IVCI LIUI I, U le ;BCD I I Ic L I IdI
may II CIiJde a 1111e1
material comprising a ternary carbide of the formuia Mx M'y Cz, M being at
yeast one eiement selected from the nronn consis n o ;tip frarlSltinli meta Is
r r d fhr. -=re _-tr#h ef, k,= !i' !helm, -+-= nfemc of <-41e;+
ML~ Ãrn hn r rr ,
consisting of Al, Ga, In, Ge, Sn, Pb, TI, Mg, Zn and Cd; x being in the range
from 2.5 to 5.0; y being in the range from 0.5 to 3.0; and z being in the
range
from 0.1 to 1.2; and the PCD comprising diamond grains having average size
in the range from 0.5 microns to 10 microns. In some embodiments, M may
be selected from the group consisting of Co, Fe, Ni, Mn, Cr, Pd, Pt, V, Nb,
Ta,
Ti, Zr, Ce, Y, La and Sc. In one embodiment, x may be 3. In one
embodiment, y may be 1.
In some embodiments, the filler material may comprise at least about 30
volume percent or at least about 40 volume percent of ternary carbide
material. In one embodiment, the filler material may comprise only ternary
carbide material and one or more other inter-metallic compounds, such that
no free or unbound M is present in the filler material. In some embodiments,
the filler material may further comprise free or unreacted catalyst material
or
further carbide formed with Cr, V, Nb, Ta and / or Ti, or both the free or
unreacted catalyst material and the further carbide. In one embodiment, the
filler material may comprise at least about 40 volume percent or at least
about
50 volume percent tin-based inter-metallic or ternary carbide.
In some embodiments of the invention, the PCD material may have an
oxidation onset temperature of at least about 800 degrees centigrade, at least
about 900 degrees centigrade or at least about 950 degree centigrade.
PCD material according to the invention may be made by a method including
forming a plurality of diamond grains into an aggregated mass and subjecting
the aggregated mass of diamond grains to a pressure treatment at a pressure
of greater than 6.0 GPa, at least about 6.2 GPa or at least about 6.5 GPa in
the presence of a metallic catalyst material for diamond at a temperature
sufficiently high for the catalyst material to melt, and sintering the diamond
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grains to form PCD material; the diamond grains in the aggregated mass
I iavi[ 19 tl le size disc IIUtion cl I~ract rl.^7L14 I that at least 0V per
lei i i of U ie 9I Il Is
nave an average size or greater ti an about 5 microns. in some
P_mnnriFrn of at iP Ct .Nhni Et 15 Cler( n.f or at k z 'aN' r1 C11 !'f 2 1
:IPP'!'PY'1fi n the
gmino aan averag si?. it the rann fV !? 'aa..hV ! t 10+=+ km ~ d.
In some embodiments of the invention, the pressure is at most about 8 GPa,
lower than 7.7 GPa, at most about 7.5 GPa, at most about 7.2 GPa or at most
about 7.0 GPa. This method is an aspect of the invention.
In one embodiment of the invention, the method may include introducing an
additive material into the aggregated mass, the additive material containing
at
least one element selected from V, Ti, Mo, Zr, W, Ta, Hf, Si, Sn or Al. In
some embodiments, the additive material may comprise a compound or
particles containing at least one element selected from V, Ti, Mo, Zr, W, Ta,
Hf, Si, Sn or Al.
in one embodiment of the invention, the method may include introducing into
pores or interstices within the aggregated mass a metal other than the
catalyst
material for diamond. In one embodiment, the metal may not be a catalyst for
diamond. In one embodiment, the catalyst material may comprise Co and the
metal may be Sn.
In one embodiment of the method, the catalyst material may be a metallic
catalyst material. In some embodiments of the invention, the catalyst material
may comprise Co, Fe, Ni, and Mn, or alloys including any of these.
In some embodiments of the method, the PCD material may be sintered for a
period in the range from about 1 minute to about 30 minutes, in the range
from about 2 minutes to about 15 minutes, or in the range from about 2
minutes to about 10 minutes.
In some embodiments of the method, the temperature may be in the range
from about 1,400 degrees centigrade to about 2,300 degrees centigrade, in
the range from about 1,400 degrees centigrade to about 2,000 degrees
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centigrade, in the range from about 1,450 degrees centigrade to about 1,700
UGglees lel lt[g IGIUC, or II i Ll le range 11 UI I a bOU L I ,45V UG9I eeS
cCn LlgIc1UG Lo
about 1,650 degrees centigrade.
In some eml-inrisments cf he `-'ention the me hod ma include subiec in--- thee-
L: Z PCD material to a heat treatment at a temperature of at least about 500
degrees centigrade, at least about 600 degrees centigrade or at least about
650 degrees centigrade for at least about 30 minutes. In some embodiments,
the temperature may be at most about 850 degrees centigrade, at most about
800 degrees centigrade or at most about 750 degrees centigrade. In some
embodiments, the PCD body may be subjected to the heat treatment for at
most about 120 minutes or at most about 60 minutes. In one embodiment,
the PCD body may be subjected to the heat treatment in a vacuum.
Embodiments of the method of the invention include subjecting the PCD
material to a further pressure treatment at a pressure of at least about 2
GPa,
at least about 5 GPa or even at least about 6 GPa. In some embodiments,
the further pressure treatment may be applied for a period of at least about
10
seconds or at least about 30 seconds. In one embodiment, the further
pressure treatment may be applied for a period of at most about 20 minutes.
In one embodiment of the invention, the method may include removing
metallic catalyst material for diamond from interstices between the diamond
grains of the PCD material.
An embodiment of the invention provides a PCD structure for cutting, boring
into or degrading a body, at least a part of the PCD structure comprising a
volume of an embodiment of PCD material according to an aspect of the
invention. In some embodiments, at least part of the volume of the PCD
material may have a thickness in the range from about 3.5 mm to about 12.5
mm or in the range from about 4 mm to about 7 mm.
In one embodiment of the invention, the PCD structure may have a region
adjacent a surface comprising at most about 2 volume percent of catalyst
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material for diamond, and a region remote from the surface comprising
greater tl lal lI about 2 volume percent of catalyst i Iia e ial for uian IV!
lu. {i I
some embodiments, the region adjacent the surface may extend to a depth Of
at !east about 2.0 microns at !east aboiu 80 macrons at least about 100
m. ! - even pt Ieasf abo t Ann m icrions f "_B fhe uurF2` In
a-r, ~Sa;.S Ek= .~^a sy: e'-.r'~ - -" one
embodiment, at least a portion of the region adjacent the surface may be in
the general form of a layer or stratum.
An embodiment of the invention provides a too[ or tool component for cutting,
boring into or degrading a body, comprising an embodiment of a PCD
structure according to an aspect of the invention. In some embodiments, the
tool or tool component may be for cutting, milling, grinding, drilling, earth
boring, rock drilling or other abrasive applications, such as the cutting and
machining of metal. In one embodiment, the tool component may be an insert
for a drill bit, such as a rotary shear-cutting bit, for boring into the
earth, for
use in the oil and gas drilling industry. In one embodiment, the tool may be a
rotary drill bit for boring into the earth.
In one embodiment, an insert comprises an embodiment of PCD material
according to the invention, the material bonded to a cemented carbide
substrate and the insert being for a drill bit for boring into the earth.
In one embodiment of the invention, the tool component may comprise an
embodiment of a PCD structure bonded to a cemented carbide substrate at
an interface. In one embodiment, the PCD structure may be integrally formed
with the cemented carbide substrate. In one embodiment, the interface may
be substantially planar. In one embodiment, the interface may be
substantially non-planar.
Drawings
Non-limiting embodiments will now be described with reference to the
drawings of which:
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FIG 1 shows a schematic drawing of the microstructure of an embodiment of
rCD I l1cU i lql.
Fir- 9 shows a processed imGinp of a rnk rnrtra,n i-i n* 9 F1ni cth Pri
cerrinrl of an
crmle. dam r: ~. orn mu+'rin!
FIG 3 shows the frequency distribution of diamond grain contiguity of an
embodiment of PCD material, with a fitted normal curve superimposed on the
distribution.
FIG 4 shows a number frequency graph of equivalent circle diameter (ECD)
grain size, shown on the horizontal axis, for an embodiment of PCD material.
FIG 5 shows a schematic drawing of an embodiment of an insert a rotary drill
bit for boring into the earth.
The same reference numbers refer to the same features in all drawings.
Detailed description of embodiments
As used herein, "polycrystalline diamond" (PCD) material comprises a mass of
diamond grains, a substantial portion of which are directly inter-bonded with
each other and in which the content of diamond is at least about 80 volume
percent of the material. In one embodiment of PCD material, interstices
between the diamond gains may be at least partly filled with a binder material
comprising a catalyst for diamond. As used herein, "interstices" or
"interstitial
regions" are regions between the diamond grains of PCD material. In
embodiments of PCD material, interstices or interstitial regions may be
substantially or partially filled with a material other than diamond, or they
may
be substantially empty. Embodiments of PCD material may comprise at least
a region from which catalyst material has been removed from the interstices,
leaving interstitial voids between the diamond grains
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In the field of quantitative stereography, particularly as applied to cemented
carbide material, 11cUILIgUILy Is UIIUeI LUUU LU Idle a LUaIILILative measure
of
inter-phase contact. It is defined as the internal surface area of a priase
shared with grains of the same phase in a subs antially turn-nhace
-U~fr Ct re fl !rider ood-, C "Quart+:f "rte Ctar~cnraohV' A di on
Wesley, Reading MA 1970; German, R.M. "The Contiguity of Liquid Phase
Sintered Microstructures", Metallurgical Transactions A, Vol. 16A, July 1985,
pp. 1247-1252). As used herein, "diamond grain contiguity" is a measure of
diamond-to-diamond contact or bonding, or a combination of contact and
10 bonding within PCD material.
As used herein, a "metallic" material is understood to comprise a metal in
unalloyed or alloyed form and which has characteristic properties of a metal,
such as high electrical conductivity.
As used herein, "catalyst material" for diamond, which may also be referred to
as solvent I catalyst material for diamond, means a material that is capable
of
promoting the growth of diamond or the direct diamond-to-diamond inter-
growth between diamond grains at a pressure and temperature condition at
which diamond is thermodynamically stable.
A filler material is understood to mean a material that wholly or partially
fills
pores, interstices or interstitial regions within a polycrystalline structure.
The size of grains may be expressed in terms of equivalent circle diameter
(ECD). As used herein, the "equivalent circle diameter" (ECD) of a particle is
the diameter of a circle having the same area as a cross section through the
particle. The ECD size distribution and mean size of a plurality of particles
may be measured for individual, unbonded particles or for particles bonded
together within a body, by means of image analysis of a cross-section through
or a surface of the body.
As used herein, the words "average" and "mean" have the same meaning and
are interchangeable.
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` ith reference to rl 1 and PiC 2, art embodiment of PCD rndLerial iu
comprises diamond grains 12 having a mean diamond grain contiguity of
Vc
renter man 60.5 tierce t he d among Grams E form c l mass
,t'vu~vt
F A-r... v -4--44- n+ ._. ..4 4 .-J .....:~.. 4 I~..F.., -... i4; ~.... T4..,
r=~':e rx^G
.:vi..... .. .:. i. r.,, u i;: .,-~. a,..,. atÃcei;r - F,aa :@i'x ~r^+e; ~.
.:~7,; -- U;-, ;_
lengths of lines passing through all points lying on all bond or contact
interfaces 16 between diamond grains within a section of the PCD material
are summed to determine the diamond perimeter, and the combined lengths
of lines passing through all points lying on all interfaces 18 between diamond
and interstitial regions within a section of the PCD material are summed to
determine the binder perimeter.
As used herein, "diamond grain contiguity" K is calculated according to the
following formula using data obtained from image analysis of a polished
section of PCD material:
x = 100 * [2*(S -(3)]/[(2*(S - (3))+6], where S is the diamond perimeter, and
i3 is
the binder perimeter.
As used herein, the diamond perimeter is the fraction of diamond grain
surface that is in contact with other diamond grains. It is measured for a
given
volume as the total diamond-to-diamond contact area divided by the total
diamond grain surface area. The binder perimeter is the fraction of diamond
grain surface that is not in contact with other diamond grains. In practice,
measurement of contiguity is carried out by means of image analysis of a
polished section surface. The combined lengths of lines passing through all
points lying on all diamond-to-diamond interfaces within the analysed section
are summed to determine the diamond perimeter, and analogously for the
binder perimeter.
Images used for the image analysis should be obtained by means of scanning
electron micrographs (SEM) taken using a backscattered electron signal.
Optical micrographs may not have sufficient depth of focus and may give
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substantially different contrast. The method of measuring diamond grain
contiguity requires that distilI L ulailUI U 91 I IIJ Ind contact Yi~iui or
bol ueu to
each other can be distinguished from single diamond grains. Adequate
rnntrast hct.ween the riia.mnnrt r rains anr1 the hnl ln! a-,t rPflinnc
9letween them
F r!,~~. he ;!nn rtnnf f". fhb rnea<-!!M of "f!r!,!h! e;n?-n hf !'rrlnr; c
between grains may be identified on the basis of grey scale contrast.
Boundary regions between diamond grains may contain included material,
such as catalyst material, which may assist in identifying the boundaries
between grains.
FIG 2 shows an example of a processed SEM image of a polished section of
a PCD material 10, showing the boundaries 16 between diamond grains 12.
These boundary lines 16 were provided by the image analysis software and
were used to measure the diamond perimeter and subsequently for
calculating the diamond grain contiguity. The non-diamond regions 14 are
indicated as dark areas and the binder perimeter was obtained from the
cumulative length of the boundaries 18 between the diamond 12 and the non-
diamond or interstitial regions 14.
With reference to FIG 3, the measured mean diamond grain contiguity of the
embodiment of PCD material, the processed image of which is shown in FIG
2, is about 62 percent. The measured data are shown fitted with a normal or
Gaussian curve, from which the standard deviation of the diamond grain
contiguity may be determined.
As used herein, the "interstitial mean free path" within a polycrystalline
material comprising an internal structure including interstices or
interstitial
regions, such as PCD, is understood to mean the average distance across
each interstitial between different points at the interstitial periphery. The
average mean free path is determined by averaging the lengths of many lines
drawn on a micrograph of a polished sample cross section. The mean free
path standard deviation is the standard deviation of these values. The
diamond mean free path is defined and measured analogously.
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The homogeneity or uniformity of a PCD structure may be quantified by
conducting a statistical evaluation using a 'large number of micrographs of
polished sections. The distribution of the tier phase, which is easily
rlictinni ilclhalhlA trom ti at of the clamenr Dnase lichen ele'trnr, M-crosco-
v.
(see also W02007/110770). This method allows a statistical evaluation of the
average thicknesses of the binder phase along several arbitrarily drawn lines
through the microstructure. This binder thickness measurement is also
referred to as the "mean free path" by those skilled in the art. For two
materials of similar overall composition or binder content and average
diamond grain size, the material that has the smaller average thickness will
tend to be more homogenous, as this implies a finer scale distribution of the
binder in the diamond phase. In addition, the smaller the standard deviation
of
this measurement, the more homogenous is the structure. A large standard
deviation implies that the binder thickness varies widely over the
microstructure, i.e. that the structure is not even, but contains widely
dissimilar
structure types.
With reference to FIG 4, which shows one non-limiting example of a multi-
modal grain size distribution for the purpose of illustration, a multimodal
size
distribution of a mass of grains is understood to mean that the grains have a
size distribution with more than one peak 20, each peak 20 corresponding to a
respective "mode". Multimodal polycrystalline bodies are typically made by
providing more than one source of a plurality of grains, each source
comprising grains having a substantially different average size, and blending
together the grains or grains from the sources. Measurement of the size
distribution of the blended grains may reveal distinct peaks corresponding to
distinct modes. When the grains are sintered together to form the
polycrystalline body, their size distribution is further altered as the grains
are
compacted against one another and fractured, resulting in the overall
decrease in the sizes of the grains. Nevertheless, the multimodality of the
grains may still be clearly evident from image analysis of the sintered
article.
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Unless otherwise stated herein, dimensions of size, distance, perimeter, ECD,
1 E Zeal free path and so I I U I rGI LII Ig to grains an u II ILGrsi1LGJ V
iil'i ii 1 1
material, as wel, as the grain contiguity, refer to the t mensions as measured
on a surface of, or a sect ors through a body comprising PC mater.ai and no
stereogra hin corredllon has heeen applier1 For exam Is_ the size
distrib'~":tioons
of the diamond grains as shown in FIG 4 were measured by means of image
analysis carried out on a polished surface, and a Saltykov correction was not
applied.
In measuring the mean value and deviation of a quantity such as grain
contiguity, or other statistical parameter measured by means of image
analysis, several images of different parts of a surface or section are used
to
enhance the reliability and accuracy of the statistics. The number of images
used to measure a given quantity or parameter may be at least about 9 or
even up to about 36. The number of images used may be about 16. The
resolution of the images needs to be sufficiently high for the inter-grain and
inter-phase boundaries to be clearly made out. in the statistical analysis,
typically 16 images are taken of different areas on a surface of a body
comprising the PCD material, and statistical analyses are carried out on each
image as well as across the images. Each image should contain at least
about 30 diamond grains, although more grains may permit more reliable and
accurate statistical image analysis.
Catalyst material may be introduced to an aggregated mass of diamond
grains for sintering in any of the ways known in the art. One way includes
depositing metal oxide onto the surfaces of a plurality of diamond grains by
means of precipitation from an aqueous solution prior to forming their
consolidation into an aggregated mass. Such methods are disclosed in PCT
publications numbers W02006/032984 and also W02007/110770. Another
way includes preparing or providing metal alloy including a catalyst material
for diamond, such as cobalt-tin alloy, in powder form and blending the powder
with the plurality of diamond grains prior to their consolidation into an
aggregated mass. The blending may be carried out by means of a ball mill.
Other additives may be blended into the aggregated mass.
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ill one eI I Ibodi Iel [t, the aggregated mass of diamol d grains, including
any
catalyst material particies or additive material particles that may have been
introduced, rnaa' U he formed into an unbonded or loosely bonded structurP
r, which magi h...a olace'"i onto a cemented carbide substrate The ceniente'd
carbide substrate may contain a source of catalyst material for diamond, such
as cobalt. The assembly of aggregated mass and substrate may be
encapsulated in a capsule suitable for an ultra-high pressure furnace
apparatus capable of subjecting the capsule to greater than 6GPa. Various
10 kinds of ultra-high pressure apparatus are known and can be used, including
belt, torroidal, cubic and tetragonal multi-anvil systems. The temperature of
the capsule should be high enough for the source of catalyst material to melt
and low enough to avoid substantial conversion of diamond to graphite. The
time should be long enough for sintering to be completed but as short as
15 possible to maximise productivity and reduce costs.
PCT publication number W02009/027948 describes polycrystalline diamond
material comprising a diamond phase and a filler material, the filler material
comprising ternary carbide, and PCT publication number W02009/027949
describes polycrystalline diamond material comprising inter-grown diamond
grains and a filler material comprising a tin-based inter-metallic or ternary
carbide compound formed with a metallic catalyst.
PCD material according to the invention has the advantage of enhanced
abrasion resistance. It may also have the advantage of enhanced strength
and enhanced thermal stability. Any or all of these advantages may result
from the enhanced diamond contiguity of the PCD material. If the mean
diamond grain contiguity is substantially less than about 60 percent, enhanced
abrasion resistance, strength or thermal stability, or a combination of these
properties, may not be exhibited. In some embodiments of the invention,
enhanced diamond grain contiguity may arise from the use of diamond grains
having a multimodal size distribution in which the grain size distribution
characteristics are selected according to an embodiment of the invention. If
the standard deviation of the diamond grain contiguity is substantially
greater
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6
than about 4 percent contiguity, then the advantages arising from having high
mean teal In lgJ. iQII contiguity may ue Subsian tially ieL._1L,Geu. If the
uiaihind grail1
contiguity is substantaiiy greater than about 80 percent or ever, greater than
annti d ! percenT men the rraC T! !I P_ 1 es sta 1C a C7T me f 'l matef a! may
oe 100
low- if the volume of the PM m aterial is substantia!!e lass than about n 5
mm2, then it may be too small for practical use in certain cutting or drilling
operations.
Embodiments of the invention have enhanced strength, abrasion resistance
and thermal stability. Enhanced contiguity and inter-grain bonding may result
in increased strength, abrasion resistance and thermal stability. While
wishing
not to be bound by theory, increased thermal stability or resistance may be
due to reduced interfacial area between catalyst material and diamond within
the microstructure.
Embodiments of PCD material according to the invention exhibit enhanced
diamond contiguity and enhanced inter-grain bonding, more homogeneous
spatial distribution of the diamond grains, less porosity and lower overall
catalyst content, all of which may generally be regarded as beneficial.
Improved homogeneity may result in less variability in the performance of the
PCD in use.
In some embodiments of the invention, the combination of high contiguity and
1 or high homogeneity and 1 or reduced content of metallic catalyst within the
PCD on the one hand, and a size distribution comprising at least two peaks or
modes, or at least three peaks or modes, on the other may result in
substantial improvement in wear resistance and other properties of the PCD,
and consequently enhanced working life and cutting or penetration rate of the
polycrystalline diamond element in rock drilling or earth boring applications,
and shear cutting rock drilling in particular. This combination of features
may
be synergistic.
Metallic catalyst materials for diamond may result in excellent inter-grain
diamond bonding and sintering, and consequently in PCD material having
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17
high abrasion resistance and strength. However, residual metallic catalyst
material may remain within the sintered PCD, located within interstices
between the diamond grains, and may reduce the thermal stability of the PCD
rnaateria;. "Thermal stability" refers to the relative insensitivity of ::e`,:
of PCD --+4 :a! _ ch as abrasion re&sta`'cc nd
15.%:1=v
strength, as a function of temperature, particularly to temperatures up to
about
700 degrees centigrade or even up to about 800 degrees centigrade.
Sintering PCD material using pressures greater than 6.0 GPa may tend to
enhance the thermal stability PCD comprising metallic filler material.
Reduced content of catalyst material in the sintered PCD may enhance
thermal stability. This may be because catalyst material may promote the re-
conversion of diamond to graphite at the elevated temperatures and ambient
pressure that typically prevail in use. Such re-conversion may significantly
weaken the PCD material. In addition, metallic catalyst material generally has
much higher thermal coefficient of expansion than diamond and its presence
may increase internal stresses within the PCD as the temperature increases
or decreases, which may weaken the material. Metallic catalyst material is
may also be vulnerable to oxidation, which may further increases internal
stresses.
Embodiments of tools according to the invention have enhanced performance.
In particular, earth boring drilling bits equipped with inserts comprising PCD
with enhanced diamond grain contiguity and sintered using a pressure of
greater than 6 GPa may exhibit superior performance in oil and gas drilling
applications. Similar benefits may also be derived where other catalyst
materials are used.
If the pressure used to sinter the PCD material is less than about 6 GPa, the
diamond grain contiguity and may not be high enough, and certain
mechanical properties such as abrasion resistance, thermal stability and
strength may not be substantially enhanced. In embodiments of the method
of the invention, it may be desirable for the pressure to be as low as
possible,
but still greater than 6 GPa, in order to permit larger reaction volumes to be
used and consequently larger articles to be sintered. Use of lower pressures
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may reduce costs and engineering complexity. In some embodiments of the
method of the invention where the diamond grains have an average size of 1
micron or less, a sintering pressure of greater than about 7.0 GPa may result
in .mnrr d s nF rinn of ceuev_menrcn vinMC)nr1 nruirl5
v~vr....e .
Embodiments of the method of the invention have the advantage that higher
temperatures can be used to form the PCD material by sintering, which may
be beneficial for the properties of the material; especially where the filler
material and / or catalyst material used has a relatively high melting point.
Embodiments of the method of the invention may be particularly beneficial
where the polycrystalline diamond material includes a filler material
comprising ternary carbide material, and the thermal stability of the PCD
material in particular may be enhanced. This may arise because ternary
metal carbide may be relatively inert with respect to diamond. Embodiments
of the method of the invention may be particularly beneficial for a type of
PCD
material that includes a filler material comprising a tin-based inter-metallic
or
ternary carbide compound formed with a metallic catalyst for diamond.
Embodiments of the method of the invention may be particularly beneficial for
making PCD material having a filler material comprising cobalt and tin,
particularly in which the average diamond grain size is less than about 10
micron, and in which at least some of the filler material is introduced by
infiltration. Embodiments of the method of the invention have the advantage
of substantially reducing the incidence of defects associated with poor
sintering, which tend to occur near the upper surface of a PCD structure.
Consequently fewer PCD elements may be rejected, resulting in improved
process economics. The PCD material may tend to have enhanced strength,
abrasion resistance and thermal stability, including oxidation resistance.
The thermal stability of embodiments of PCD material according to the
invention, particularly the oxidation onset temperature as measured by means
of thermo-gravimetric analysis (TGA), may be substantially enhanced.
Embodiments such as these may be thermally stable and exhibit superior
performance in applications such as oil and gas drilling, wherein the
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temperature of a PCD cutter element can reach above about 700 degrees
centigrade. Oxidation onset temperature is measured by means of thermo-
gravimetric analysis (Ti GA) in the presence of oxygen, as is known in the
art.
C A +...-.I ... r.~ ~~n --4---;-l _rrJS_ Is. f h~ .t 44 .t_ h
z
advantageous for the cutting or machining of metal, owing to the enhanced
thermal stability and resistance of the PCD material.
Examples
Embodiments of the invention are described in more detail with reference to
the examples below, which are not intended to limit the invention.
Example 1
An aggregated mass of diamond grains having a mean size of about 8
microns was formed by blending diamond powder from two sources having
respective mean grain sizes in the range from about 1 micron to about 4
microns and in the range from about 7 microns to about 15 microns. The
blended diamond grains were treated in acid to remove surface impurities that
may have been present. Vanadium carbide (VC) powder and cobalt (Co)
powder were introduced into the diamond powder by blending particles of VC
and Co with the diamond powder using a planetary ball mill. The mean size of
the VC particles was about 4 microns and the content of the VC in the
aggregated mass was about 3 weight percent. The aggregated mass was
then formed into a layer on a substrate comprising Co-cemented tungsten
carbide (WC) and encapsulated within a capsule for an ultra-high pressure
furnace to form a pre-sinter assembly, which was then out-gassed in a
vacuum to remove surface impurities from the diamond grains, as is known in
the art. The diameter of the substrate was a little greater than about 13mm
and the height was about 10mm.
The pre-sinter assembly was subjected to a pressure of about 6.8 GPa and a
temperature of about 1,600 degrees centigrade in an ultra-high pressure
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furnace to sinter the diamond grains and form a PCD compact comprising a
layer of PCD material integrally formed with the carbine substrate. The PCD
layer was about 2mm thick. During the sintering process, molten cobalt from
or both in sol:.~~.rin enfi tr ted
the substrate and containing tlsso:.'e~. AI or WC
A section was cut from the PCD material and a section surface was polished.
Sixteen digital images of microscopic areas were obtained at different
respective positions on the section surface by means of scanning electron
10 micrography (SEM) using a backscattered electron signal. The resolution of
the images was 0.04717 micrometers per pixel. Each of the images was
subjected to image analysis to measure the mean diamond grain contiguity,
the mean diamond grain ECD, the mean interstitial ECD, the diamond grain
mean free path and the interstitial mean free path, as well as the standard
15 deviations of each of these quantities. These quantities were then averaged
over those obtained for all the images. In the case of the diamond grain and
interstitial ECD size measurement, the size distribution was characterised
more fully, as described below. In performing the image analysis, the contrast
between the diamond grains and the boundary regions between diamond
20 grains was adjusted to emphasise boundaries between grains on the basis of
grey scale contrast.
The image analysis was performed using software having the trade name
analySiS Pro from Soft Imaging System GmbH (a trademark of Olympus
Soft Imaging Solutions GmbH) may be used. This software has a "Separate
Grains" filter, which according to the operating manual provides satisfactory
results if the structures to be separated are closed structures. Therefore, it
is
important to fill up any holes before applying this filter. The "Morph. Close"
command, for example, may be used or help may be obtained from the
"Fillhole" module. In addition to this filter, the "Separator" is another
powerful
filter available for grain separation. This separator can also be applied to
color- and gray-value images, according to the operating manual.
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Results of the image analysis are summarised in Tables 1 and 2. The content
of diamond was measured to be about 90.8 volume percent, the diamond
grain contiguity was about 68.4 percent and the mean size of the sintered
dia nd grains, was s about lA41t 6 i t-I Ird N in trm 01 es~riuaiva iens a
role .~.aiamecar.
41R sRf el/1 Ãl.1 .Y V-wl R? ~ R 'e~rl MO - .
r TLV -- - --- r-t-r.-t:t_ia1 __ r..=_ _at.- .I the lDr+r1 1 1
( 0.46) micron.
The data relate to two dimensional measurements taken from image analysis
of a scanning electron micrograph, and has not been corrected for three
dimensions. For example, the quoted mean diamond grain size is the mean
size corresponding to the cross-sectional areas of diamond grains. The
diamond and interstitial sizes are calculated as equivalent circle diameters
(ECD), by determining the cross-sectional area and calculating the diameter
of a circle having the area. The statistical parameters d10, d50, d75 and d90
refer to the sizes (ECD) for which 10 percent, 50 percent, 75 percent and 90
percent, respectively, of grains are less than. The maximum size is the size
for which substantially no grains are greater. The parameters "Lower (95
percent)" and "Upper (95 percent)" refer to the size values for which 5
percent
of grains are less than and greater than, respectively.
Mean, Standard d10, d50, d75, d90, Maximum,
microns deviation, microns microns microns microns micron
microns
Diamond 6.30 2.52 2.77 6.17 8.06 9.10 12.40
grain size
Interstitial 1.75 0.90 0.63 1.63 2.26 2.94 3.98
size
Diamond
grain MFP` 4.51 4.96 0.33 2.74 6.65 11.04 49.25
Interstitial 0.52 0.46 0.09 0.38 0.71 1.13 4.72
MFP'"
*MFP is mean free path
Table 1
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Mean, percent Standard deviation Lower Upper
(95 percent? !95 rercent)
Diamond content,
:3 0. osn t =.a
1 interstitial, percent area 9.25 i 0.55 i 8.95 9.55
Diamond contiguity, 68.0 1.15 67.4 68.6
percent
Table 2
Example 2
An aggregated mass of diamond grains having a mean size of about 10
microns was formed by blending diamond powder from five sources having
respective mean grain size in the range from about 0.5 micron to about 3
microns, in the range from about 2 microns to about 5 microns, in the range
from about 4 microns to about 9 microns, in the range from about 7 microns to
about 15 microns and in the range from about 10 microns to about 30
microns. The blended diamond grains were treated in acid to remove surface
impurities that may have been present. Vanadium carbide (VC) powder and
cobalt (Co) powder were introduced into the diamond powder by blending
particles of VC and Co with the diamond powder using a planetary ball mill.
The mean size of the VC particles was about 4 microns and the content of the
VC in the aggregated mass was about 3 weight percent. The aggregated
mass was then formed into a layer on a substrate comprising Co-cemented
tungsten carbide (WC) and encapsulated within a capsule for ultra-high
pressure furnace to form a pre-sinter assembly, which was then out-gassed in
a vacuum to remove surface impurities from the diamond grains, as is known
in the art. The diameter of the substrate was a little greater than about 13mm
and the height was about 2mm.
The pre-sinter assembly was subjected to a pressure of about 8GPa and a
temperature of about 1,700 degrees centigrade in an ultra-high pressure
furnace to sinter the diamond grains and form a PCD compact comprising a
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layer of PCD material integrally formed with the carbide substrate. The PCD
layer was about 2mm thick. During the sintering process, molten cobalt from
the substrate and containing dissolved W or WC, or both, in solution
infiltrated
Into the aggregate mass of diamond ains_
SEM images of the PCD material were obtained as described in Example 1,
except that the resolution of the images was 0.09434 micrometers per pixel.
Results of image analysis of the images are shown in Table 3 and Table 4
below. The content of diamond was about 90.7 volume percent, the diamond
grain contiguity was about 70.3 percent and the mean size of the sintered
diamond grains was about 7.4 microns in terms of equivalent circle diameter.
Mean, Standard d10, d50, d75, d90, Maximum,
deviation,
microns microns. microns microns microns micron
microns
Diamond 7.4 3.4 2.8 6.9 9.9 12.0 14.2
grain size
Interstitial 2.95 1.41 1.0 2.9 3.9 4.8 5.9
size
Diamond 5.0 6.1 0.23 2.7 7.2 13.0 58.9
grain MFP*
Interstitial 0.66 0.68 0.09 0.42 0.89 1.5 7.04
MFP'"
*MFP is mean free path
Table 3
Mean, percent Standard deviation Lower (95 percent) Upper (95 percent)
Diamond content, 90.7 0.56 90.4 91.0
percent area
Interstitial, percent area 9.2 0.56 8.9 9.55
Diamond contiguity, 70.3 1.9 69.2 71.3
percent
Table 4
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The PCD compact was processed to form a test PCD cutter insert, which was
subjected to a wear test. The wear test involved using the insert in a
vertical
turret milling apparatus to cut a length of a workpiece material comprising
i i1 riii hr- Viii fe ;u& ir e ti eifo r ,;,t
v~~.iivvv v`v i::.V u.v ....,G.. rsuv '..: ~:: -v:: i... ...-.: ...eu :..u9
...
indication of expected working life in use. The cutting distance achieved with
the test insert was about 75 percent greater than that achieved using a
control
PCD cutter insert, which had been sintered at a pressure of about 5.5GPa and
which contained no VC additive. The abrasion resistance of the test cutter
insert was observed to be substantially enhanced.
Example 3
Test and control PCD material samples were prepared using sintering
pressures of 6.8 GPa and 5.5 GPa, respectively. In all other respects the test
and control samples were made in the same way. Raw material diamond
powder was prepared by blending diamond grains from three sources, each
source having a different average grain size distribution. The size
distribution
of the grains within the resulting blended powder had the size distribution
characteristic that 9.8 weight percent of the grains had average grain size
less
than 5 microns, 7.6 weight percent of the grains had average size in the range
from 5 microns to 10 microns, and 82.6 weight percent of the grains had
average grain size greater than 10 microns. The blended diamond grains had
an average size of approximately 20 micron.
Cobalt and tin were deposited onto the surfaces of the diamond grains by
means of a method including depositing cobalt and tin oxides onto the
surfaces from an aqueous solution. The cobalt-tin accounted for about 7.5
percent of the coated diamond mass, and was found to be dispersed over the
grain surfaces as nano-scale formations.
The cobalt-tin coated diamond grains were formed into an aggregated mass
on a surface of a cobalt-cemented tungsten carbide substrate, and this
assembly was encapsulated within a refractory metal jacket to form a pre-
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compact assembly, from which air was subsequently removed. The pre-
compact assembly was loaded into a capsule for a high-pressure high
temperature furnace.
cvi i j iZ2ve iai ..u3 .3 i:: `wivv.v... .,.. ,... F.;..., .. ... r:~:.. .~.
.,.. ....
temperature of 1,550 degrees centigrade for about 9 minutes to form a
compact comprising a sintered PCD mass bonded to a tungsten carbide
substrate.
10 The control material was subjected to a conventionally used pressure of
about
5.5 GPa and a temperature of about 1,450 degrees centigrade for about 9
minutes to form a compact comprising a sintered PCD mass bonded to a
tungsten carbide substrate.
15 The compacts were substantially cylindrical in shape, having a diameter of
about 16 mm. The compacts comprised a layer of PCD integrally bonded
onto a cobalt-cemented tungsten carbide (WC) substrate, the PCD layers
being 2.2 mm thick. The diamond content of the PCD layer was about 92
percent by volume, the balance being cobalt and minor precipitated phases
20 such as WC. The diamond grains within the PCD thus produced had a
multimodal size distribution having the characteristic that 34.7 weight
percent
of the grains had average grain size less than 5 microns, 40.4 weight percent
of the grains had average size in the range from 5 microns to 10 microns, and
24.9 weight percent of the grains had average grain size greater than 10
25 microns. The grain size distribution of the sintered PCD is different from
that
of the input grains due to mutual crushing of the grains at high pressure, in
addition to the shift towards coarser grain sizes that normally occurs during
the sintering process.
The control and test compacts were analysed. Both were found to comprise
PCD with the following phases present in the interstices: Co3Sn2, Co3SnCp.7,
CoSn, Co and WC. The major phase was Co3SnCo.7, and it is believed that
this phase plays a major role in improving the thermal stability of the PCD.
The other phases were present in trace quantities.
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image analysis was used to analyse the inter-growth of the diamond grains as
well as the homogeneity of their spatial distribution within the PCD. A higher
degree of diamond gain inter-growth was observed :.rthen the PCD of the test
ll~_.~ I.L.= ..-....1..r.! _ _.-.1 TL.. ...r.
intergrowth and contact can be expressed in terms of diamond grain
contiguity, the average contiguity of the test PCD being 62.0 percent ( 1.9
percent), compared to the control PCD average contiguity of being 59.2
percent ( 1.4 percent), the figure in brackets being the standard deviation).
Statistically, this absolute difference of 2.8 percent may be substantial,
since
an absolute difference in contiguity of 0.8 percent corresponds to a
confidence
interval of 95 percent.
The average interstitial mean free path of the test PCD was about 0.74
( 0.62) micron, compared to the control PCD average of 1.50 ( 2.53)
micrometers.
More cobalt was present in the test PCD than in the control PCD, the
additional cobalt having infiltrated from the cobalt-containing substrate, it
is
believed. This resulted in the test PCD having a higher content of Co3SnC0.7
than the control PCD. Additionally, the content of WC was higher in the test
PCD, which contained a greater quantity of re-crystallised WC "plume"
formations near the interface with the substrate.
Results of image analysis of the test material are summarised in Tables 5 and
6. The data relate to two dimensional measurements taken from image
analysis of a scanning electron micrograph, and has not been corrected for
three dimensions. The parameters in the table have the same meaning as
described in Example 1.
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Mean, Standard
d10, d50, d75, d90, Maximum,
deviation, microns .. U.
1 I C F i d
grain size 11.4L 4.3:3 :5.4:5 ( y.lU j 1.S.U9 1O.V4 19.23
Interstitial 219 108 0.80 2.01 3.42 3.5 5.48 [
size
Diamond 5.94 7.09 0.38 3.11 8.3 15.47 67.92
grain MFP*
Interstitial 0.68 0.60 0.19 0.47 0.94 1.42 6.51
MFP*
*MFP is mean free path
Table 5
Mean, percent Standard deviation Lower (95 percent) Upper (95 percent)
Diamond content, 90.54 0.57 90.24 90.84
percent area
Interstitial, percent area 9.46 0.57 9.16 9.76
Diamond contiguity, 62.05 1.86 61.06 63.04
percent
Table 6
Both the control and test samples were processed to form inserts suitable for
rock boring, and subjecting the inserts to a wear test that involved using the
inserts to machine a granite block mounted on a vertical turret milling
apparatus. This test involved machining a granite block over a number of
passes and measuring the size of the wear scar formed into the PCD as a
result of abrasive wear against the granite. After 50 passes, wear scar of the
test PCD was about 30 percent smaller than that of the control PCD, and
lasted at least another 100 passes in working condition.
When several more samples of test and control PCD were manufactured, it
was found that the quality of the test PCD was much more consistent than
that of the control PCD, and the reject rate was much lower.
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it has been found that the use of a method according to the first aspect of
the
invention permits thick PCD structures to be sintered. T nicker PCB structures
have Greater strenoth. all else beina eauaf. than thinner PCD structures.
Example 4
Several samples of Co-Sn-based PCD sintered onto a cemented carbide
substrate were prepared. In each case, tin powder was pre-reacted with
cobalt metal powder to produce a CoSn alloy I intermetallic of specific atomic
ratio 1:1. This pre-reacted source was then introduced into an unsintered
diamond powder mass by either pre-synthesis admixing or in situ infiltration.
The 1:1 CoSn pre-reacted powder mixture was prepared by milling the Co and
Sn powders together in a planetary ball mill. The powder mixture was then
heat- treated in a vacuum furnace (600 degrees centigrade to 800 degrees
centigrade) to manufacture reacted CoSn material. This pre-reacted material
was then further crushed I milled to break down agglomerates and reduce the
grain size. The diamond powder size distribution had an average grain size of
less than about 10 microns. A chosen amount of this CoSn material
(expressed as a weight percent of the diamond powder mass) was then
brought into contact with the unsintered diamond powder within an ultra-high
pressure furnace reaction volume. This was either as a discrete powder layer
adjacent to the diamond powder mass (which would infiltrate the diamond
during ultra-high pressure treatment after melting, i.e. in situ infiltration)
or the
CoSn material was admixed directly into the diamond powder mixture before
the canister was loaded. The diamond powder 1 CoSn assembly was then
placed adjacent a cemented carbide substrate such that the binder metallurgy
was then further augmented by the infiltration of additional cobalt from the
cemented carbide substrate at the ultra-high pressure conditions. The
assembly was subjected to a pressure of about 6.8 GPa and a temperature
above the melting point of cobalt. In this way, a range of Co : Sn ratio
binder
systems and resultant PCD materials was produced.
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Example 5
A mono-modal PCD test material was prepared by blending cobalt powder
,11h diamond ara,ns be means of a olanetarv ball m-HI and sinte."ino the
c c.~ ^^! ^! -^^sz+ r .,s r " ~ :~"
f -7 -7 r'Q-^- 'f ^h^,'+ `7 inn
degrees centigrade for a period of about 60 seconds. The diamond grains
had average size in the range from 3 micron to 6 micron. The weight ratio of
cobalt to diamond in the blended powder mix was 18 : 82. Free-standing,
unsupported sintered PCD samples having diameter of 13.7 mm and height of
4 mm were produced.
A control PCD material was made similarly to the test material, except that i)
the cobalt was introduced by infiltration from a cemented tungsten carbide
substrate, as is conventional, resulting in a weight ratio of cobalt to
diamond
was 26 : 74, and ii) a sintering pressure of 5.5 GPa and temperature of about
1,450 degrees centigrade was used.
A scanning electron micrograph of a polished section of the sintered test PCD
was obtained using backscattered electrons, and image analysis was carried
out on the micrograph. Results of image analysis of the test material are
summarised in Tables 7 and 8, the parameters having the same meaning as
defined in Example 1.
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Standard
Mean, d10, d5D, d75, d9Q, Maximum,
deviation, 1' C: aoS M IC f:
microns
D, e o à i t
grain size 4.13 i 2.22 i 1.81 4.86 j f.12 7.33 j y.U9 i
Interstitial 1.11 0.58 0.41 0.98 [ 1.49 1.68 3.14
size
Diamond
grain MFP* 3.63 3.30 0.47 2.74 4.74 8.23 46.18
Interstitial 0.32 0.31 0.05 0.23 0.47 0.74 3.40
MFP*
*MFP is mean free path
Table 7
5
Mean, percent Standard deviation Lower (95 percent) Upper (95 percent)
Diamond content, 9124 0.35 91.05 91.43
percent area
Interstitial, percent area 8.76 0.35 8.57 8.95
Diamond contiguity, 73.54 0.67 73.19 73.90
percent
Table 8
The test and control samples were formed into cutting inserts by conventional
10 processing and subjected to a wear test involving the milling of granite. A
depth of cut of 1 mm depth was used. The output of the wear test is a cutting
length, which is the distance of granite milled before the cutter is deemed to
have failed. The cutting length of the test PCD was about 5,100 mm, which is
significantly greater than the control PCD cutting length of about 1,200 mm.
15 This indicates that the abrasive wear resistance of the test PCD is several
times greater than that of the control PCD.
