U.S. patent number 3,702,573 [Application Number 04/808,590] was granted by the patent office on 1972-11-14 for cermet product and method and apparatus for the manufacture thereof.
This patent grant is currently assigned to Kennametal Inc.. Invention is credited to Bela J. Nemeth.
United States Patent |
3,702,573 |
Nemeth |
November 14, 1972 |
CERMET PRODUCT AND METHOD AND APPARATUS FOR THE MANUFACTURE
THEREOF
Abstract
The invention relates to a cermet product and a method and
apparatus for the manufacture thereof in which carbonaceous
material is placed in a cell in the presence of metal and converted
to diamond form. The converted charge upon removal from the
apparatus is shaped and mounted on a tool holder and it is then
adapted for use as a turning tool. The invention contemplates
conversion of the carbon-metal charge in a shaped cavity to reduce
the amount of shaping required after the charge is removed from the
chamber in which it is converted.
Inventors: |
Nemeth; Bela J. (Greensburg,
PA) |
Assignee: |
Kennametal Inc. (Latrobe,
PA)
|
Family
ID: |
25199198 |
Appl.
No.: |
04/808,590 |
Filed: |
March 19, 1969 |
Current U.S.
Class: |
76/115; 75/243;
407/113; 407/119; 423/446 |
Current CPC
Class: |
B23P
15/28 (20130101); B01J 3/062 (20130101); B01J
2203/062 (20130101); Y10T 407/23 (20150115); B01J
2203/0655 (20130101); Y10T 407/27 (20150115); B01J
2203/0625 (20130101) |
Current International
Class: |
B23P
15/28 (20060101); B01J 3/06 (20060101); B21k
021/00 () |
Field of
Search: |
;76/11R,11A
;23/209.1 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Stickney; Bernard
Claims
What is claimed is:
1. In the manufacture of sharp edge cutting elements, a method for
simultaneously making a plurality of said elements comprising:
confining in a cell a plurality of charges on non-diamond carbon
and matrix metal and a carbon solvent metal in alignment and
separating individual charges into discrete bodies separated by
alumnia oxide divider members, developing conditions of pressure
and temperature on said charges which are in the thermodynamically
diamond stable region of the carbon equilibrium diagram when in the
presence of said solvent metal thereby to cause conversion of the
carbon to diamond, removing the converted charge from the cell,
separating said discrete bodies at said divider members, and
shaping at least a part of each body so separated to the form of a
cutting element having at least one cutting edge thereon, said
elements being adapted for mounting on holders to permit said
cutting edges of the elements to be presented to work to be cut
thereby.
Description
This invention relates to diamond products and to methods of, and
apparatus for, manufacturing such products.
Diamonds are a crystalline form of carbon and it has been found
that nondiamond form of carbon can be converted to diamond form by
subjecting the carbon to certain conditions of heat and pressure.
The term carbon as employed herein is intended to mean
substantially any material containing carbon in nondiamond form.
Thus, materials which are partly carbon, or which contain carbon in
the form of carbon compounds are included within the scope of the
term carbon as employed herein. For practical reasons, the carbon
employed is as nearly pure carbon as possible, with certain
physical specifications, because any other material included
therewith is merely excess and reduces the efficiency of any
conversion cycle.
Different methods can be employed for establishing the conditions
of pressure and temperature at which carbon converts to the diamond
form but the present invention is concerned with the process
wherein the carbon is confined within a cell and is subjected to
mechanical pressure and to the development of heat within the cell
by passing an electric current therethrough. It has been found that
the process referred to operates with much greater efficiency and
at the lowest temperatures and pressures when a metal is included
in the cell with the carbon. A number of metals have been found
suitable for this purpose such as one or more metals selected from
the class consisting of iron, cobalt, nickel, rhodium, ruthenium,
palladium, osmium, iridium, chromium, tantalum, manganese, and
alloys thereof. Other metals such as titanium, zirconium, and
copper can be included in the metal component in the cell if so
desired. It is essential that at least one of the metals be a
solvent for carbon because it is believed that, when the carbon
converts from the nondiamond state thereof to its diamond state,
the carbon is dissolved in the metal solvent therefor and, inasmuch
as the conditions of heat and pressure are those at which the
crystalline diamond form of carbon is stable, the carbon
immediately, following the dissolving thereof in the metal,
precipitates from the metal in the form of diamond. The pressures
employed in such cells range upwardly to 50,000 atmospheres and
more and temperatures established within the cell range from
1,000.degree. to 2,000.degree. Centigrade. Under these conditions
of heat and pressure, the metal in the cell becomes molten and, as
mentioned above, the carbon in the cell goes into solution in the
metal and precipitates therefrom as diamond crystals. The carbon in
the cell, whether in the form of one or more solid pieces, or in
the form of powder. Excellent results have been obtained from the
use of carbon having a density of from about 1.7 to about 1.9 but
higher and lower density carbon is not excluded. This permits the
metal to infiltrate throughout the carbon and promotes efficient
conversion of the carbon to diamond.
According to the present invention it is desired for the metal
included in the cell with the nondiamond form of carbon to be a
tough high melting point material and it has been found that alloys
of iron, nickel, and chromium of the class of alloys referred to as
Inconels are suitable for this purpose either with or without the
addition of small amounts of other metals such as manganese,
tantalum, titanium, zirconium, and copper.
In the usual manner in which diamonds are manufactured, the charge
is removed from the cell in which the diamonds are formed, and the
diamond crystals are recovered by a complex and lengthy physical
and chemical processing which results in completely freeing the
diamond crystals from all the other material in the cell. The now
clean diamonds are then sized and are ready for use as the abrasive
component in abrading devices such as diamond wheels, drills, saws,
and the like or for incorporation in lapping compounds.
Diamonds of a size sufficient to form large single point tools have
not heretofore been produced by any manufacturing method because
synthetic diamonds have always been recovered from the cell in
which they are made in the manner referred to and which, as
mentioned, will produce only small diamond crystals ranging in size
from about 40 mesh down to micron sizes.
Examination of a charge from a cell of the nature referred to after
conversion thereof will reveal that there are diamond crystals in
the charge prior to crushing which are substantially larger than
any of the diamond crystals which can be recovered from a cell by
the aforementioned recovery process. The diamond crystals in the
charge are of random sizes and random orientation and in
intertwined relation and tend to break at the weak section or
sections thereof when the charge in the cell is crushed thereby
leading to the relatively small size crystals that are recovered by
the aforementioned lengthy and time consuming chemical and physical
recovery process. The diamonds recovered by such a process are
similar to natural diamonds, with respect to hardness and can be
employed for any cutting or abrading operations for which natural
diamonds are employed.
The present invention is based on the observation that the
converted charge in a cell consists of the diamond crystals and the
metal in the cell and an insignificant amount of unconverted carbon
all intimately bonded together and with the diamond crystals having
random orientation. Sometimes no unconverted carbon at all can be
found in the converted charge. In particular, the bond between the
diamonds and the metal, and which is referred to herein as the
"matrix metal," is particularly intimate because the diamonds are
precipitated from the metal-carbon melt and, thus, at the interface
where each diamond crystal engages the matrix metal there is a bond
which forms, and which is, of course, the most intimate possible
bond between the diamond and metal and one which is not possible to
establish except when the diamond is in a thermodynamically stable
state. This bond is destroyed by the lengthy process ordinarily
employed for the recovery of diamonds.
The diamond crystals, once recovered from the charge and cleaned of
all adherent metal, cannot again have such an adherent metal
coating applied thereto for the reason given above. It has been
attempted to plate diamonds in various manners, such as by
electrolytic plating, and by vapor plating, and the like, but no
process known to applicant can reproduce the intimate molecular
bond existing between the diamond and metal which is formed while
the diamond is under conditions in which the diamond is
thermodynamically stable.
Tests and experiments performed on the charge material following
conversion reveal that the charge exhibits considerably physical
strength in the form of compressive strength and in resistance to
abrasion. It appears that the charge material, compacted at the
extremely high pressures employed during the conversion process
produces an extremely solid material in which the matrix metal and
diamonds support one another and wherein the diamonds have random
orientation so that the converted material in the charge presents
the possibility for use as cutting and abrading material without
recovering the diamonds in a completely clean form and thereafter
forming a useful abrading material by again combining the diamond
with a supporting substance or matrix therefor. For the material of
the charge to be employed as a cutting material, however, it is
required that, in addition to the matrix material possessing a high
compressive strength and physically supporting the diamonds, it be
resistant to high temperatures and tough so that it will withstand
conditions that are encountered in cutting operations.
With the foregoing in mind, a principal objective of the present
invention is the provision of a diamond product and a method of
making the diamond product in which the customarily followed
process for recovery of the diamonds in clean form is
eliminated.
A particular object of the present invention is the provision of a
diamond product and a method of, and apparatus for, making the
product in which the charge in the cell in which the diamonds are
produced is formed directly into cutting members such as cutting
inserts for use in metal forming operations and the like.
A still further object of the present invention is the provision of
a diamond product and a method of, and apparatus for, making the
product in which end products can be obtained at greatly reduced
costs over anything that has been possible heretofore.
A still further object of the present invention is the provision of
a diamond product and a method of, and apparatus for, manufacturing
the product in which the diamond product, as removed from the cell
in which the diamonds are formed, requires the absolute minimum in
forming operations to convert it into a cutting insert.
The nature of the present invention will be more clearly understood
upon reference to the following detailed specification taken in
connection with the accompanying drawings in which:
FIG. 1 is a sectional view showing a typical apparatus employed for
effecting the conversion of nondiamond carbon to diamond;
FIG. 2 illustrates the charge in a cell after conversion and with
the outer sleeves of the cell removed;
FIG. 3 is a fragmentary perspective view showing a cutting element
made from the charge of FIG. 2 and mounted on a holder;
FIG. 4 is a view showing various cross sectional shapes possible
for the cell in which the charge is converted;
FIG. 5 is a photomicrograph of a section through a typical charge
shown at 200 times natural size;
FIG. 6 is a view like FIG. 5 but at 500 times natural size;
FIGS. 7, 8, 9, and 10 are perspective views showing still other
tools that can be manufactured using the cutting elements according
to the present invention;
FIG. 11 shows a cell in vertical cross section in which divider
members separate the charge into discrete portions;
FIG. 12 is a cross sectional view of the cell of FIG. 11 and is
indicated by line XII--XII on FIG. 11; and
FIG. 13 is a perspective view of a typical discrete portion of the
cleavage in the cell of FIGS. 11 and 12 after conversion and
removal from the cell.
FIG. 1 shows one type of apparatus in which nondiamond graphite or
carbon can be converted to diamond under proper conditions. In FIG.
1, reference numeral 10 is a ring, such as a ring of cemented
tungsten carbide material, which is press fitted into a heavy
surrounding steel ring in order to withstand the stresses to which
it is subjected. Pressure pistons enter the ring 10 from opposite
ends to exert pressure on the charge therein. One such piston is
indicated at the top of the cell by reference numeral 12, with the
not-shown piston at the bottom of ring 10 being identical to piston
12. The prepared cell containing the charge comprises an inner
sleeve 16 of alumina, a tube 18 of graphite surrounding tube 16,
and a further insulating tube 20, of alumina, for example,
surrounding tube 18.
Within tube 16, in the particular cell arrangement shown in FIG. 1,
there is placed body 22 of carbon which preferably has a density of
from about 1.7 to 1.9. Holes are drilled into the body 22 of carbon
from the opposite ends thereof with each hole receiving a rod or
wire 24 of the metal or metal alloy in which the carbon goes into
solution during the conversion process. The holes in the block or
body 22 of carbon, one of said holes being indicated at 25, are
laterally offset from each other so that the rods or wires 24
therein do not interfere with movement of the pressure pistons
toward each other during conversion of the charge.
Each end of tube 16 has therein a pair of alumina discs 26 in
closing relation to the ends of the tube. Larger metal discs 28
extend over the ends of the cell the full diameter of outer tube 20
and are in electrically conductive engagement with the adjacent end
of graphite tube 18. Graphite tube 18 is a heater tube and becomes
hot by passing an electric current therethrough which is conveyed
to and from tube 18 by discs 28.
A metal ring 29 may be provided resting on an adjacent disc 28 and
inside ring 29 is an alumina plug 31. Ring 29 brings the adjacent
pressure piston into electrically conductive relation with the
adjacent disc 28.
Disposed between the cell and the ring 10 and between the pressure
pistons and the ring 10 are sealing sleeves 30 which are of an
electrical insulating material which are, and have the
characteristics of, pyrophyllite, or talc. Advantageously, sleeves
30 are of the shape illustrated with a metal sleeve 32 disposed
therebetween. The material of the sleeves 30 is such that they will
become somewhat deformed under the pressure exerted thereon by the
piston 12 at the top of the cell and the corresponding pressure
piston at the bottom of the cell so as to permit the pressure
pistons to advance toward the cell as the charge in the cell
reduces in volume during conversion, but will not extrude between
ring 10 and the pressure pistons which would cause the pressure on
the cell to be lost.
After the cell as described has been placed in the apparatus shown,
the pressure pistons are pressed toward each other to develop a
certain pressure on the material within the cell while
simultaneously electric current is passed through the cell between
the pressure pistons and through tube 18 whereby the tube 18
becomes heated quickly and material in the cell also becomes
heated. When the conditions of pressure and temperature in the cell
reach the diamond stable region, there is a sudden conversion of
the carbon in the cell to diamond. The conditions of pressure and
temperature and other parameters established in the cell and
leading to the conversion of the carbon to diamond, might, for
example, be 50,000 to 75,000 atmospheres, and 1,200.degree. to
2,000.degree. Centigrade. The metal of the rods or wires becomes
molten under the conditions at which diamonds will form and this
molten metal infiltrates the carbon in the cell and dissolves the
carbon to form a metal carbon melt and it is from this molten mass
that the carbon converts or crystallizes into diamond form with
simultaneous precipitation from the melt.
When the cell is removed from the die, it has somewhat the
appearance as shown in FIG. 2 except that the sleeves 16, 18, and
20 still have at least fragments in place on the converted material
when it is removed from the cell. FIG. 2, more exactly, shows the
appearance of the converted charge after the outer sleeves of the
cell have been removed. This converted charge, shown in ideal form
in FIG. 2 consists of relatively solid member 40.
In view of the fact that the metal becomes molten and dissolves the
carbon, there is sufficient migration of the metal and carbon that
there is uniform distribution of metal in member 40.
The present invention takes advantage of the fact that diamond
crystals are grown in a matrix of metal, and are tightly adherent
to the metal, to produce novel diamond products having particular
merit in respect of the forming of cutting tools.
What is proposed by the present invention is the forming of the
converted charge into one or more inserts for mounting on holders
so that the inserts can be employed as turning tools. It has been
found that inserts or cutting elements manufactured in this manner
have extremely long life and can be employed in substantially any
situation in which single point natural diamond tools are now
utilized.
Single point diamond tools, as is known, are tools having a single
large natural diamond mounted on a holder, by brazing, for example,
and sharpened. Such tools are employed for shaping green carbide
compacts, alumina, other ceramics, and similar materials which are
so hard and abrasive that ordinary cutting tools cannot be used.
Single point diamond tools, however, are expensive and are limited
as to size, shape, and availability, and are extremely difficult
and expensive to resharpen once they become dull.
Inserts or cutting tips made from the material removed from the
cell in accordance with the teachings of the present invention can
be roughly shaped as by a silicon carbide wheel and finish shaped
by using a diamond wheel of from 180 grit to 300 or 400 grit. While
the inserts or cutting elements according to the present invention
can be shaped relatively simply, they nevertheless are possessed of
extreme resistance to wear and can exhibit length of life and a
quality of performance as good as that of a single point diamond
tool.
Returning to FIG. 2, the compact taken from the cell may have weak
regions or cleavage planes therein, as at 44 and if a portion is
broken off from member 40, it will be a rather roughly formed disc.
This small disc can be shaped by grinding to form a cutting element
45 that can be mounted on a holder 46 as shown in FIG. 3 as by
brazing. Alternatively, the cutting tip can be clamped to the
holder by any conventional insert clamping arrangement. The final
grinding of the insert or cutting tip can take place after it is
mounted on the holder if so desired. Such final shaping might take
the form of finishing the top and periphery of the insert or
cutting tip to provide it with a sharp edge, or grinding the tool
to provide it with a clearance angle.
Alternatively, a piece can be cut from member 40 and then shaped to
a cutting element. The cell illustrated in FIG. 1 is circular in
cross section so that member 40, after conversion, is roughly
cylindrical, but other cross sectional configurations are possible
as shown in FIG. 4. FIG. 4, for example, shows a triangular form at
48, a square form at 50 and a somewhat elliptical form at 52. Round
cells, and cells of the configurations shown in FIG. 4, are quite
practical, as well as other cell shapes so long as the loading
imposed at the pressure pistons does not cause the pistons to tilt
and interfere with development of uniform pressure on the entire
charge in the cell.
FIG. 1 shows the charge in the cell placed therein in the form of a
block or rod of carbon with metal wires inserted therein but it is
also quite practical to insert the carbon charge into the cell in
the form of powder. The metal can also be in the form of powder
and, further, the carbon and metal powder can be admixed in the
proper proportions and then charged into the cell. In a cell
charged with admixed carbon and metal powders, it is possible to
induce the formation of cleavage planes by the introduction of
layers of material within the cell which will not interfere with
the conversion process in any way and which will part freely from
the connected charge. Further, as will be seen hereinafter, the
charge in the cell can be placed therein in such a manner that,
after conversion, it is in the form of discrete members of
predetermined size and shape. Still further, the charge can be made
up of discs of carbon and metal arranged in alternating relation in
the cell.
The nature of the charge removed from the cell shows that there is
growth of diamond crystals, therein of substantial size and some of
which are relatively complex in shape. The space between the
individual diamond crystals, and, even sometimes regions inside the
diamond crystals, are filled with the matrix metal that is charged
into the cell with the carbon and which matrix metal, as mentioned,
is tightly adherent to the diamond crystals.
FIGS. 5 and 6 demonstrate the structural nature of the material
when it is taken from the cell. FIG. 5 is a photograph 200 times
natural size of a sample of material taken from the cell and ground
to a smooth finish. FIG. 6 is a photograph of a portion of FIG. 5
but at 500 times natural size and has been etched to sharpen the
contrast between the diamond crystals and the matrix metal in which
the crystals are embedded and bound.
The conversion of the carbon in the cell is often as high as 95 per
cent or better to diamond and a fully converted charge is thus
substantially completely diamond with a metal matrix completely
filling the space between the diamonds and integrally bonded to the
diamonds. The diamond crystals are thus extremely tightly and
strongly supported and inserts formed of this material are
extremely strong and wear resistant.
The bond of the metal to the diamond crystals in the charge as
removed from the cell is different in kind from the bond of metal
to diamond that can be obtained from any known plating process. The
metal is intimately bonded to all exposed surfaces of the diamond
crystals and can be removed therefrom only by prolonged chemical
and physical treatment. If the charge is crushed, the diamonds tend
to break before the diamond to metal bond breaks, indicating the
strength of this bond.
In FIG. 5 the areas indicated by reference numeral 80 are the
diamond crystals and the regions indicated at 82 are the matrix
metal. It will be noted that the diamond crystals have various
shapes and that they are intertwined. In the normal procedure for
recovering diamonds from a cell of the type disclosed, and wherein
the diamond crystals are completely separated from all of the metal
in the cell, the diamond crystals will break at the smaller
sections thereof and the result will be rather small diamond
crystals having absolutely clean surfaces to which it is difficult
to cause any sort of binding or bonding material to adhere.
It the converted charge, when removed from the cell, is not
subjected to treatment to remove the matrix metal from the
diamonds, the diamonds remain imbedded in the matrix metal so that
the metal forms a supporting and enclosing and tightly adherent
matrix. The diamond crystals retain their integrity and are
supported by the matrix metal and do not break or fracture at the
small cross sectional portions thereof. The result seems to be
that, while the article removed from the cell can relatively easily
be formed as by grinding with a silicon carbide or diamond grit
wheel, for example, the articles nevertheless are extremely
resistant to wear when used as turning tools or the like. The
diamonds have more or less random orientation and no particular
care need be taken in locating the cutting edge on the article as
in the case with large natural diamond crystals that are presently
employed for turning tools. Such natural diamond crystals must be
carefully oriented in a certain manner to obtain the best
results.
Furthermore, the random orientation of the diamond crystals in the
matrix metal insures a strong cutting edge on any part of the
insert so finished. The inserts can, therefore, be indexed and
inverted and will always present a good edge to the work.
It will be seen in FIG. 5 that the matrix metal completely fills
the space between adjacent diamond crystals and some is embodied
within the limits of diamond crystals so that the diamond crystals
are completely supported by the matrix metal in all directions.
FIG. 6 is a view similar to FIG. 5 but is enlarged to 500 times
normal and has been etched so as better to develop the contrast
between the diamond crystals and the matrix metal. In FIG. 6 the
regions marked 84 are the diamond crystals and the regions marked
86 are the metal regions. Due to the etching carried out on the
sample, FIG. 6 more clearly illustrates the great preponderance of
diamonds in the material than does FIG. 5. Substantially 83 per
cent by volume of the sample is diamond and the remainder is matrix
metal.
The tool shown in FIG. 3 is a simple tool using a circular cutting
element taken from a conventional cylindrical cell. FIGS. 7, 8, 9,
and 10 show certain other types of turning tools that can be made
according to the present invention. FIG. 7, for example, shows a
holder 90 having a pocket 92 formed therein in which is disposed an
insert 94, according to the present invention, which is
substantially rectangular. Insert 94 can be made in a rectangular
cell and thereafter finished by grinding on the top and bottom and
the four edges, as it can be cut from any other shape of connected
charge. An insert finished in this manner has four indexed
positions and can be inverted and thus has eight effective cutting
regions thereon. Furthermore, the insert can be sharpened when it
becomes dull and restored to original cutting condition. Insert 94
in FIG. 7 is loosely disposed in the recess and is clamped therein
by clamp member 96 which may also hold a chip breaker 98 in place
on top of the insert. A shim 100 may be disposed in the pocket
beneath the insert if so desired according to conventional
practices followed with cutting inserts.
In FIG. 8 the holder 102 is formed with a slot 104 and disposed in
the slot in end to end relation are cutting inserts 106 according
to the present invention. These inserts may be brazed or cemented
in position in the slot. Brazing of the inserts in position is a
relatively simple matter because the matrix metal easily fuses with
the brazing material. For cementing, an epoxy cement is an ideal
material. The tool of FIG. 8 could be used for boring operations,
for example.
FIG. 9 shows a tool similar to that illustrated in FIG. 3 except
that the insert 108 brazed on the holder 110 is triangular and may
be made in a triangular cell.
FIG. 10 shows a fragment of a saw, a cement saw, for example,
having teeth 214 and tips 216 made according to the present
invention and brazed to the teeth.
The tools illustrated in FIGS. 3 and 7 to 9 utilize relatively
large cutting inserts but it will be understood that cutting
inserts substantially smaller in cross sectional area than the
charge in the cell could be made and brazed or clamped on holders
according to the present invention.
FIG. 11 shows in vertical cross section a cell for the formation of
articles of a predetermined shape whereby machining time required
for reducing the articles to a useable condition is greatly
reduced. The cell arrangement is shown in transverse cross section
in FIG. 12 and a typical work member as removed from the cell is
shown at FIG. 13. Referring more particularly to FIGS. 11 and 12,
the outermost sleeve 200 of the cell is in the form of an aluminum
oxide member cylindrical on the outside and having a substantially
square hole 202 extending axially therethrough. Closely fitted in
hole 202 is a square graphite sleeve 204 and within graphite sleeve
204 is a thinner aluminum oxide sleeve 206. The inner and outer
alumina sleeves and the intervening graphite sleeve are assembled
as shown in FIGS. 11 and 12 and the innermost sleeve 206 receives
the charge which is in the form of individual bodies 208 consisting
of nondiamond carbon and metal. Disposed between the individual
bodies 208 are high density aluminum oxide divider members 210.
When the cell illustrated in FIGS. 11 and 12 is subjected to heat
and pressure in the diamond stable range of the
pressure-temperature equilibrium diagram for carbon, the carbon
goes into solution in the metal and substantially immediately
precipitates therefrom in the form of diamond crystals so that each
body 208 forms, in effect, an individual charge which is converted
in the aforesaid manner.
After conversion, the cell is broken open and the converted bodies
208 are removed therefrom. One such body is indicated at 212 in
FIG. 13 and it will be seen to comprise a slightly irregular block
which is a solid mass of matrix metal and diamonds of the nature
which has been described previously. Block 212 in FIG. 13 required
only a small amount of machining to finish off the several faces
thereof whereupon it can be used as a cutting insert by attaching
it to suitable holder therefor. The blocks 212 can be made to any
desired shape and need not be square as shown in FIG. 13. Any
dimensional size can be made within the limits of cross sectional
area on which the necessary pressure can be developed.
The blocks 212 can be used as cutting inserts or, if made to
relatively small sizes could be brazed on the tips of teeth 214 of
a saw as indicated at 216 in FIG. 10. Other uses for the diamond
products as disclosed herein will suggest themselves to those
skilled in the art.
When the diamond products according to the present invention are to
be employed as cutting inserts, it is important for the metal
forming the matrix in which the diamond crystals are imbedded to be
a tough high melting point material of the nature of Inconels
previously referred to, or other alloys possessing high
strength.
Another characteristic of the diamond product manufactured
according to the present invention is that it has an extremely high
coefficient of heat conductivity. Natural diamonds, for the reason
that they have such an extremely high coefficient of heat
conductivity, are employed for heat sinks and the like where it
might be necessary, for example, to maintain an electrical
component such as a transistor within relatively close temperature
limits. The high heat conductivity of a natural diamond enables it
to be employed to stabilize the temperature of a transistor more
efficiently than other materials.
The material of the present invention, consisting principally of
diamond crystals intimately bonded to a solid metal matrix has a
coefficient of heat conductivity which, while somewhat less than
that of solid natural diamond, is nevertheless substantially
greater than that of metal. Thus the diamond product according to
the present invention can also find a use as a heat sink or the
like.
In cases where the diamond product is employed for purposes where
its heat conductivity is the important characteristic, the matrix
metal would not, of course, be required to be a tough heat
resistant material such as Inconel. Conversion of the nondiamond
carbon to diamond form in the presence of metal or alloy, even
where the metal, or alloy, is not required to be tough or high
melting point, or both, still requires, of course, that the metal
or alloy include a carbon solvent. For example, when the diamond
product is manufactured for use as a heat sink, copper, which is
not a carbon solvent, might be included with the metal or alloy
with which the carbon is converted for the reason that copper
itself has a high heat conductivity.
In the specification and claims, the term "metal" includes a carbon
solvent metal and alloys or mixtures thereof with other metals
which may or may not be carbon solvents.
The invention includes modifications and adaptations within the
scope of the appended claims.
* * * * *