Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02311516 2000-11-28
1 "METHOD FOR ENHANCING HARD MATERIAL MOUNTING SURFACES"
2
3 FIELD OF THE INVENTION
4 The present invention relates to means for affixing natural diamond
to a substrate such as metal or other materials, particularly for tool
supports or
6 holders. More specifically, a process is disclosed for machining a diamond,
7 ceramic or hard metal mounting surface with a laser and the unique product
8 resulting therefrom.
9
BACKGROUND OF THE INVENTION
11 Non-gem quality diamond has unsurpassed wear resistance and is
12 appropriately used in industrial applications such as machining and earth
drilling.
13 Natural diamond has many disadvantages which have resulted in a shift to
the
14 use of engineered polycrystalline forms. Some of the disadvantages of using
natural diamond include its relatively brittle characteristics, and its.size
limitation.
16 An alternative to natural diamond is the engineered polycrystalline diamond
and
17 man-made thick film diamond.
18 Polycrystalline diamonds are referred to in the industry as
19 polycrystalline diamond compact or PDC. PDC diamonds are formed of a matrix
of diamond grains, often mixed with powdered binder or silica. While PDC
21 diamonds are more readily mounted to metal, they are not as strong and
durable
22 as naturally occurring diamond.
23 Man-made thick film diamond is made using a technique called
24 Chemical Vapour Deposition or CVD wherein chemicals are deposited on the
bonding surface in a gas and, under ideal conditions, crystals formed are
grown
26 to create a thick film.
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1 PDC used for industrial purposes is formed into polycrystalline
2 structures. Single crystal diamonds are problematic as they have structural
3 planes of cleavage which result in fracture when large or sudden force is
applied
4 in the direction of one of its planes of cleavage. Consequently, when single
crystal diamond is fixedly set into a metal matrix, limitations are imposed
upon
6 the angles at which it can be used. This problem is not limited to
applications
7 where single crystal diamond is set into a metal matrix. Rather it is a
problem in
8 substantially all industrial applications where single crystal diamond is
used.
9 PDC diamond, in its polycrystalline form, has an added toughness
over single crystal diamond due to the random distribution of the crystals
which
11 results in a lack of distinct planes of cleavage. Therefore,
polycrystalline diamond
12 is frequently the preferred form of diamond in many drilling, turning,
cutting or
13 similar operations and has been directly substituted for single crystal
diamond for
14 use in a metal matrix.
Thick film diamond, has a controllable toughness compared to
16 single crystal diamond. The random distribution of the crystals, caused by
re-
17 nucleation during the ,process, and the crystal-type of each individual
crystal
1$ results in a lack of distinct planes of cleavage. Therefore, thick film
diamond is of
19 increasing interest for use in drilling, turning, cutting or similar
operations.
Brazilian natural diamond, called carbonado, is a naturally occurring
21 random diamond structure and, like PDC, does not have cleavage weakness. It
is
22 found in large enough diamonds to be useful for tool insert manufacture ~
and is
23 stronger than PDC diamond, however it has all of the mounting problems
24 associated with natural diamond.
2
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1 Natural and polycrystalline forms of diamond are typically affixed to
2 a tool holder or insert made from metal or other appropriate materials to be
used
3 for drilling or cutting purposes. The difficulty in affixing the diamond to
the insert
4 has been of particular interest and has resulted in the development of
several
mounting techniques.
6 One system of mounting is to surround the diamond in a supportive
7 matrix. This system is wasteful as it requires a substantial quantity of
diamond to
8 be unexposed and useless. for cutting or drilling purposes. The
impracticality of
9 this system has resulted in a turn of the technology towards PDC. PDC
provides
greater opportunity for affecting a superior mounting surface than has
previously
11 been known or available for natural diamond:
12 For instance, in US patent 4,629,373 to Hall and incorporated
13 herein by reference, a PDC diamond is disclosed which has a mounting
surface
14 which has been enhanced for improved mechanical attachment. Various forms
of parallel and linear channels or an array of pits are formed in the mounting
16 surface so as to enhance the mechanical connection to the substrate. It is
known
17 to manufacture PDC diamond in a press in which grains of diamond and other
18 starting materials are subjected to ultrahigh pressure and temperature
conditions.
19 Hall discounts the use of natural diamonds for a variety of reasons and
goes on
to describe the elimination of several proposed methods of affixing PDC to
tools.
21 However, Hall describes further difficulties in mounting even PDC, such as
lack of
22 adhesives which bond PDC or natural diamonds to a substrate, residual
thermal
23 stresses placed on a cemented tungsten carbide backing with brazing, and
the
24 wasteful use of a metal matrix mount.
3
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1 In the face of the described problems, Hall's approach was to
2 enhance the mounting surface of the PDC. Due to the method of manufacture,
3 Hall's PDC is formed under pressure to create the enhanced surface,
including
4 one in which diamond grains are placed in a dovetail mold, and pressed to
form
PDC having a plurality of parallel dovetail grooves. Because of the
interlocking
6 nature of the dovetails, the only way to expose the PDC enhanced surface is
to
7 acid dissolve the mold out of the grooves.
8 This technique cannot be applied to natural diamond as natural
9 crystalline diamond cannot be pressed into a mold. Hall discloses that
machining
techniques are possible for post-press cycle formation of these surfaces, such
11 techniques including laser or electric discharge machining.
12 However, even if machined rather than pressed, Hall's substantially
13 linear, parallel grooved surfaces highly weaken natural crystal, subject to
14 breakage along cleavage lines.
It is also known to use lasers to remove inclusions, bore linear
16 holes through and etch indicia on the surface of gem quality diamonds. If
applied
17 to the surface of industrial diamonds these linear alterations have the
same
18 problems as those identified with Hall's grooved surfaces.
19 Therefore, there is demonstrated a need for an effective mechanical
bonding surface which can be utilized with natural diamonds or thick film
21 diamonds so as to take advantage of the superior strength of diamond
without
22 risk of fracture. Such techniques are further advantageous if also
applicable to
23 PDC diamond to form a stronger bonding surface.
24
4
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1 SUMMARY OF THE INVENTION
2 In a preferred form of the invention a laser-machining process is
3 disclosed which is capable of cutting an enhanced mounting surface in the
plane
4 surface of a superhard material such as diamond. The term cutting is to be
interpreted broadly as resulting in a void being left in the material and can
6 include: melting and blowing molten material out of the void, melting and
boiling
7 material away, and vaporizing material away. The enhanced planer mounting
8 surface has superior mechanical interlocking and bonding capability when
9 mounted as cutting elements to tool substrates. In another form of the
invention,
a tool substrate can be similarly laser-machined for producing a superior
11 mounting surface on a tool insert for the application of PDC or thick film
diamond
12 material.
13 Accordingly, in one broad form of the invention, the mounting
14 surface which is to be laser-machined is temporarily mounted for rotation
about
an axis perpendicular to its surface. A laser beam is directed along an axis
which
16 is at an angle to the surface's rotating axis. The laser beam axis
intersects the
17 rotating mounting surface for cutting an undercut void in the mounting
surface as
18 it rotates. The position, form and size of the undercut varies depending
upon
19 how often and where the laser beam is directed onto the rotating surface.
By
repositioning the laser beam with respect to the rotating surface, a plurality
of
21 different undercut voids can be formed.
22 In another aspect of the invention, the laser beam can be pulsed
23 and synchronized with the speed of rotation of the surface for cutting a
pattern of
24 undercut voids in the surface.
5
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1 The process is suitable for enhancing cutting elements and tool
2 inserts alike for producing superior cutting tools.
3 One form of apparatus suitable for enhancing the planer mounting
4 surface of a hard material comprises: a rotating plate to which the material
is
temporarily affixed, the planer surface being arranged perpendicular to the
plate's
6 axis of rotation, a drive for rotating the plate and affixed mounting
surface, a laser
7 which emits a laser beam along an axis which intercepts the mounting surface
8 and which is angled from the plate's axis of rotation. A two dimensional
actuator
9 controls the relative coordinates of the intercept of the laser beam and
mounting
surface, preferably to enable intercept of substantially the entire mounting
surface
11 by the laser beam. A one dimension actuator controls the focus of the laser
12 beam. Preferably the laser beam is pulsed and the drive is variable speed
for
13 ensuring the surface speed of the mounting surface intercepted by the laser
14 beam is maintained at or below a predetermined speed.
6
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1 BRIEF DESCRIPTION OF THE DRAWINGS
2 Figure 1 is a perspective view of a cutting material mounted to a
3 tool insert, the mounting surface of the material having been enhanced in
4 accordance with the present invention;
Figure 2 is a perspective schematic and somewhat fanciful view of
6 a diamond, ceramic or hard metal disc affixed to a rotary plate movable on a
two
7 axis table, and a single axis moving laser used for implementing an
embodiment
8 the invention, shown oriented in three-dimensional Cartesian coordinates.
9 Figure 3 is a perspective schematic of one form of a 3-axis system
for relative positioning of the surface and the laser;
11 Figures 4a and 4b are a side view and a partial close-up side view
12 of the formation of a void using incremental advancing of the X-Y table;
13 Figures 5a,5b,5c,5d are a plan view of the disc, a cross-sectional
14 side view and a close up partial views of an undercut void, respectively.
The
views illustrate the results of a plurality of DY step translations of the
disc, relative
16 to the laser beam, from the lower portion of the rotating mounting surface
to its
17 center;
18 Figures 6a,6b,6c,6d are views according to Figs 5a - 5d illustrating
19 the results of a plurality of subsequent DY step translations of the
mounting
surface, relative to the laser beam for the second half of the mounting
surface
21 from its center to the upper portion top of the semicircle;
22 Figures 7a,7b,7c,7d are views according to Figs. 6a - 6d illustrating
23 the results of a plurality of additional OX step translations of the
mounting surface
24 across its diameter;
7
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1 Figures 8a,8b,8c,8d are views according to Figs. 7a - 7d illustrating
2 the results of a plurality of diagonal OX, 0Y step translations of the
mounting
3 surface across its diameter;
4 Figures 9a,9b,9c,9d are views according to Figs. 5a - 5d illustrating
the results of a plurality of combined ~X, ~Y step translations of the
mounting
6 surface resulting in an elliptical translation of the laser beam across the
mounting
7 surface for forming a plurality of conical undercuts;
8 Figures 1 Oa,10b,10c are a plan view of the disc, a cross-sectional
9 side view and a perpendicular face on view of the mounting surface
illustrating a
pattern of voids formed by a pulsing of the laser beam at a plurality of ~X,DY
step
11 translations of the mounting surface, relative to the laser beam;
12 Figures 11 a and 11 b illustrate a cross-section through the
13 centerline of a diamond disc illustrating a plurality of the preferred
dovetail voids
14 and a fanciful perspective representation of their orientation distributed
in a
discrete and discontinuous fashion on an inclined disc;
16 Figure 12a illustrates a cutting element laser-machined according to
17 the first embodiment of the invention and bonded to a tool insert; and
18 Figure 12b illustrates a cutting element mounted to a laser-
19 machined tool insert according to the second embodiment of the invention.
8
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1 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
2 Having reference to Figs. 1, 12a and 12b, a laser-machining
3 process is applied to a mounting surface 10 of a hard or superhard material
11
4 for improving mechanical bonding at the interface to a second material.
In a first embodiment, the hard material 11 is diamond disc D
6 mounted to a tool substrate, holder or insert 12, such that used for a
7 subterranean drill bit. The surface 10 of the diamond is laser-machined for
8 enhancing its surface. The disc D can then be mechanically bonded to the
tool
9 insert 12. In this first embodiment, the invention is described for
applications
involving the mounting of natural or other diamond to a metal substrate or
other
11 tool insert 12 through laser-machining of the diamond's mounting surface
10.
12 However, the invention is equally applicable to laser-machining of the
mounting
13 surface of the tool insert 12 for the subsequent mounting of PDC, thick
film
14 diamond and ceramics.
In a simple form, in the first embodiment and the result of which is
16 shown in Fig. 12a, the diamond material 11 has a cutting surface 13 which
may
17 have one of many cutting surfaces, often merely being a planer disc D (as
shown
18 in Fig. 1 ). The diamond disc D has a mounting surface 10 for eventual
mounting
19 to the tool insert 12. The diamond's mounting surface 10 is machined for
forming
one or more voids having an undercut feature, thereby enhancing the mechanical
21 interlocking ability of the diamond material 11 to be bonded to the tool
insert 12.
22 In the simplest respect, the machining is directed to forming voids
(described
23 below) through and into the mounting surface 10 and leaving at least an
interface
24 which forms a mechanical, interlocking undercut at the entrance to the
void.
9
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1 In a second embodiment and the result of which is shown in Fig.
2 12b and alternatively, by applying the same laser-machining technique to the
3 hard metal material 11 of a carrier-substrate tool insert 12 such as
tungsten
4 carbide, an ideal interlocking bonding surface is formed upon which diamond
can
be grown using thick film Chemical Vapor Deposition (CVD) techniques or to
6 which pressure-form polycrystalline diamond compact (PDC) or other ceramic
7 material is mounted during its plastic production phase.
8 Having reference to Figs. 2 and 3, apparatus for laser-machining
9 comprises a rotary plate 14 upon which the hard material 11 is temporarily
affixed
with a suitable compound so that the planer mounting surface 10 is exposed and
11 is perpendicular to the rotational axis R. The rotational axis is set along
the R
12 vector, the angle between the R-vector and the Z-axis determines the angle
of
13 the void's undercut 40. For permitting automation of the laser-machining
14 process, the mounting surface 10 must be substantially planer so that it
may be
rotated in its plane during laser-machining.
16 A 5 Watt, 3500 Hz, Yttrium-Aluminum-Garnet (YAG) laser 20 emits
17 a beam 21 along a Z-axis, shown in Fig. 2 as being vertical. The laser beam
21
18 has a focal point F which can be focused through incremental translation
(Oz) of
19 the laser 20 along the Z-axis, illustrated fancifully by a movable carriage
22
driven by a microstepper motor 31z. The axis of rotation R of the plate is
21 divergent from the laser's Z-axis (at an non-zero angle) so that the
mounting
22 surface 10 is not perpendicular to the laser's Z-axis. The plate's
rotational axis R
23 is along an R-vector angled generally upwardly in the Z direction and along
the X-
24 axis. The Y-axis is perpendicular to the X and Z-axes.
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1 The rotating plate 14 is driven with a variable speed controllable
2 servo motor 23. The rotational speed range of the servo motor 23 and plate
14 is
3 sufficient to achieve surface speeds over the majority of the mounting
surface 11
4 of about twelve mm/second (the critical speed) for natural diamond material
11.
A critical speed of twelve mm/s is based on a 5W YAG laser and is both laser
6 and material dependent. The optimal surface speed can be predetermined,
7 empirically or through other means. Other critical speeds can be
predetermined
8 and are applicable for different lasers, power settings and substrate
materials. At
9 speeds faster than critical, less cutting is achieved and multiple passes
are
required. At slower speeds, the hard material substrate 10 is at risk of
damage
11 due to excessive heat build-up.
12 In one embodiment, the rotating plate 14 and servo motor 23 are
13 movable (Ox,Dy) on an X-Y table 30 (Fig. 3) using X-Y actuators or
microstepper
14 motors 31xy for repositioning the rotating plate 14 and mounting surface 11
under
the beam 21 of the laser 20. Alternatively, but not shown, the laser 20 could
be
16 translated in X and Y over the rotating plate 14. The laser 20 is movable
in the Z-
17 axis using another actuator or microstepper motor 31z so that the laser
beam
18 focus F can be adjusted (Oz) as the rotating plate 14 translates and the
mounting
19 surface 10 approaches and falls away from the laser beam focal point F.
If the laser 20 is pulsed, then a plurality of circumferentially spaced
21 voids V are formed shown in Fig. 10a - 10c. By translating the X-Y table 30
so
22 that the laser beam 21 is focused at a point F on the lower semicircle
portion of
23 the mounting surface 10 (above the rotational axis), a first path is cut
forming a
24 radially outward directed voids V in the material's surface 10.
11
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1 By actuating and translating the X-Y table 30 so that the laser beam
2 21 is focused at a point on the upper semicircle portion of the mounting
surface
3 10 (above the rotational axis), a second path is cut forming a radially
inward
4 directed void in the material's surface 10. Again, by having passed the axis
of
rotation R, successively translating ~x the table 30 in the X-axis while
cutting, the
6 undercut 40 is adjusted to provide a second undercut.
7 For a continuous laser beam 21, the resulting circumferentially
8 extending void is curved and, while it may cross a cleavage, such as in a
natural
9 diamond, it will not weaken it. Further, the void has an undercut formed in
one or
more planes which, when filled with a bonding material prevents its separation
11 without failure of the bonding materials.
12 More preferably however, during machining, the laser beam 21 is
13 pulsed in synchrony with the material's rotation. The formerly continuous
void is
14 now broken up into discrete, discontinuous voids (Fig. 10a-10c). As long as
the
discrete voids are shifted sufficiently radially and the timing of the pulses
is
16 sufficiently long, the voids are separated by continuous substrate material
11,
17 thereby providing strength to the material 11 and minimizing stress
raisers.
18 Referring back again to Fig. 2, to coordinate the machining process,
19 a high speed microcomputer 25, such as that powered by an Intel Pentium 166
MHz or higher processor, is employed to numerically control the servo 23,
21 microstepper motors 31xyz and laser pulsing. Controls are provided for
22 controlling the machining to obtain a pre-determined pattern of voids in
the
23 mounting surface 10. The microcomputer 25 directs the X-Y table 30 and
24 microcontrollers 31xy to grossly position the mounting surface 10 under the
laser
beam 21 and to finely position (0x) the laser 20 for forming a void V. The
laser
12
CA 02311516 2000-11-28
1 beam focus F is dynamically manipulated by changing ~z in response to X-axis
2 changes in the mounting surface 10 being machined.
3 The rotational speed w of the servo motor 23 is computer-controlled
4 to ensure the critical speed is maintained. Note that for a given rpm, when
the
laser 20 is cutting a void at the radial periphery of the mounting surface 10,
that
6 the surface speed is much higher than at the inside radius. Accordingly, the
rpm
7 must be adjusted to ensure that the surface speed is maintained at about
8 12mm/s where the laser beam intercepts the mounting surface it is currently
9 cutting. Thus the rotation speed and the X and Z-axis positions must be
known
and compensated for.
11 As shown in Figs. 4a and 4b, with the laser beam 21 focused at
12 coordinates CA in the lower semicircle portion of the mounting surface 10
(below
13 the rotational axis), a first path is laser-machined or cut to form one or
more
14 shaped voids V in the material 11. The laser beam 21 ablates a portion of
the
hard material 11 to form the void V. Due to the divergent axes of the laser
beam
16 21 (Z-axis) and rotational plate 14 (R-vector), the voids V form an
undercut 40 in
17 the mounting surface 10.
18 As shown in Fig. 4b, by successively translating Ox the table in the
19 X-axis while cutting, the void V can be widened. If the laser 20 is
substantially
continuous (which is relative depending upon the surface speed and laser pulse
21 cycles) then a continuous void is formed. If the plate 14 is translated
fully under
22 the laser beam 21, and without further machining, a parallelogram void is
formed.
23 Sufficient angle must be set between the R-vector and the Z-axis to account
for
24 the conical beam of the laser and still form an undercut void.
13
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1 As shown more clearly in Figs. 4a and 4b, the laser beam 21 is
2 directed at desired first coordinates CA, located low on the rotating plate
14 and
3 in the material 11. The laser beam 21 is focused at point F in the material
11
4 cutting the a first void, the base of which is illustrated as B. The void V
is angled
outwardly to the periphery of the mounting surface 10. The table 30 can be
6 actuated to shift along the X-axis an increment 0X. The laser beam 21 is
7 refocused (0Z) higher on the rotating plate 14 and material 10 for cutting
an
8 additional void V having a new base at B'. If the OX is small, the voids
overlap
9 forming an even larger void. Similarly as shown later in Figs. 7a-7d,
shifting the
table in the Y-axis permits alternate positioning of the laser beam on the
11 uprotation edge and down rotation edges of the substrate 10 forming the
radially
12 angled voids and respectively.
13 Figs 4a and 4b further illustrate how successive steps of the X-axis
14 microstepper 31x motor from A to A' to A" to A"' result in successive voids
having
bases at B, B', B", and B"' respectively. The voids V are formed through the
16 surface 10 and into the materials 11. Best seen in Fig. 4b, the voids V
have their
17 base B,B' ... located within the material 11 and an entrance E formed at
the
18 surface 10. Each base B has a peripheral extent which is at a different
position
19 than the peripheral extent of the entrance E, thereby creating a lip or
undercut 40.
This means that at least one edge of the peripheral extent of the base is
shifted
21 radially from the peripheral extent of the entrance E (as in the case of
Figs.
22 4b,5a-5d) or circumferentially from the peripheral extent of the entrance E
(as in
23 the case of Figs. 6a-6d).
24 In recognition of the aforementioned cleavage issue with natural
diamonds, it is important to avoid a lining up of the voids. Accordingly, for
voids
14
CA 02311516 2000-11-28
1 V formed in natural diamonds with cleavage, the preferred voids would be
small
2 and discontinuous, or continuous but curved.
3 If the laser beam 21 were continuous, then a continuous circular
4 and annular void V would result (Fig. 2). Preferably, a plurality of
concentric
annular voids are provided for maximal mechanical bonding. Another pattern of
6 void V is a sector appearance of radially and circumferentially bounded and
7 spaced voids, each of which is discontinuous from their radial and
circumferential
8 neighboring voids (Fig. 11 b). This requires a pulsing of the laser beam 21
at a
9 rate synchronous with the speed of rotation of the surface 10 so that each
cut is
performed substantially coincident with the desired pattern.
11 Various forms of voids V can be formed by manipulating the
12 coordinates of the laser beam 21 with respect to the mounting surface 10.
As
13 shown in Figs. 5a - 5d, incremental 0X translation of the surface 10 from
14 coordinates CA low on the rotating disc to its midpoint CO produces
outwardly
angled voids Va. As shown in Figs. 6a - 6d, continuing the incremental NC
16 translation of the surface 10 from the center CO to coordinates CB high on
the
17 rotating mounting surface 10 produces inwardly angled voids Vb, the
ultimate
18 cross-section of which resembles a parallelogram or dovetail. Note that due
to
19 the rotation of the mounting surface 10, the void cross-section becomes
mirrored
on the diametrically opposing side of the material 11. The form of the
21 parallelogram is not precise. Due to the actual conical shape of the
focused laser
22 beam 21, one cut of the laser beam 21 produces a more conical void V as
shown
23 in Fig. 4b.
24 More elaborate voids V can be formed by translating the rotating
plate 14 and surface 10 in both X and Y axes. As shown Figs. 7a - 7d, a
knotted
CA 02311516 2000-11-28
1 pyramidal void is formed by addition of 0Y translations of the surface 10
across
2 the diameter of the surface 10 from coordinates CC - CD which have been
3 previously already machined with a plurality of OX translations (Figs. 6a-
6d). As
4 shown in Figs. 8a - 8d, the addition of diagonal translations CE'-CE" and
CF'=CF", in both OX and ~Y, will form larger voids
6 Using a 5W, 3500 Hz YAG laser, voids having a base dimension of
7 0.06 mm and a smaller surface entrance opening of 0.01 mm at the surface 10
8 are possible, machined for instance into 4mm to 25mm diameter discs of
9 diamond.
In summary, as shown in Figs. 1, 12a and 12b, a diamond disc
11 cutting element D can be produced for use on an earth boring drill bit or
other
12 tool, such as a rotary drag bit. The cutters are predominately comprised of
a
13 diamond cutting structure attached to either a reduced-volume substrate or
14 directly to a bit body, optionally using a carrier structure mounted to the
bit body.
In the case of the first embodiment (Fig. 12a), the method consists of
preparing
16 and enhancing the bonding surface of the diamond with a laser to obtain an
17 improved bond between the a substrate material and diamond. In the second
18 embodiment (Fig. 12b), one can prepare the bonding surface of the tool
insert
19 metal with a laser and then grow a sufficiently thick diamond film on top
of it.
As described above, the laser 20 is operated to generate voids in
21 the particular hard surface 10 permitting allowing bonding materials under
high
22 pressure or temperature to penetrate the mounting surface or in the case of
23 growing a diamond film, starting the crystal nucleation in the voids and
extending
24 these crystals on top of the surface, resulting in a permanent mechanical
anchoring befirveen the material and the surface. The design or the shape of
16
CA 02311516 2000-11-28
1 these voids, as well as the preparation of these voids by metal powder
2 impregnating or metal containing compounds, are critical to achieve the
proper
3 anchoring. The undercut design of these voids is such that the cross
sectional
4 dimension inside the void exceeds the average cross section of the entrance
to
these voids.
6 When bonding a PDC or other formable material, a mechanical
7 anchoring or bonding results when material penetrates the voids under
plastic
8 conditions and returns or sets to non-plastic conditions. To achieve this,
high
9 mechanical pressure and increased temperature, under near vacuum conditions,
are crucial to improve the contact affinity between the intruding metal (such
as
11 braze of tungsten, copper and nickel or tungsten, copper and silicon) and
the
12 diamond and certain organo-metallic agents can be applied, containing
Silver,
13 Nickel, Lead, Silicon or Titanium.
14 When growing a diamond film on a laser-prepared bonding surface,
a mechanical anchoring results when a gas such as methane, under crystal
16 generating chemical vapour deposition conditions, enters the voids. The
17 nucleating crystals grow to fill the void and extend to the surface
resulting in a
18 continuous diamond face of sufficient thickness to allow its use as a tool
or drill
19 bit insert.
17
