Production of carbide laden consumables in a graphite mold

A carbide laden consumable is produced using a mold having at least one U-shaped groove running along the surface thereof, the consumable being produced by charging a first layer of a powdered self-fluxing alloy into the groove, a second layer of a powdered refractory carbide on said first layer and a third layer of said self-fluxing alloy on the carbide layer, and the charged mold then passed through a heating furnace under a reducing atmosphere to produce by melting and cooling a consumable of markedly improved quality.

This invention relates to a method for producing carbide laden consumables 
of improved quality in the form of composite rods comprising particles of 
refractory carbide, such as tungsten carbide, distributed through a matrix 
of a self-fluxing alloy. 
STATE OF THE ART 
Refractory carbides of various particle sizes are used as additives to 
certain alloys for use in producing hard face coatings on metal substrates 
which in use are subjected to wear and abrasion. Such hard face coatings 
may be used to provide cutting edges, or the consumable may be employed in 
the mining or oil industries for applying the refractory carbide-matrix 
alloy composite structure to parent materials, for example, rotary cutting 
bits, fishing tools, and other working parts. Generally speaking, the 
cutting and/or wear and abrasion surfaces produced by these refractory 
carbides find use in equipment used for drilling, boring, reaming, earth 
removing, burning shoes, core tools, bucket teeth for excavation 
equipment, and the like. 
It would be desirable to have a consumable which has good quality as to 
cleanliness and which can be handled fairly roughly in the field without 
breaking easily. One method for producing a composite rod comprised of 
carbides distributed through a matrix alloy is disclosed in U.S. Pat. No. 
3,523,569 dated Aug. 11, 1970. In this patent, the composite rods are 
produced by distributing loose particles of a refractory carbide linearly 
along a holding surface, e.g. along the internal V-groove of an angle 
iron, and then applying a molten self-fluxing matrix alloy over the 
refractory carbide layer by successive passes thereover with a flame 
torch, the spraying being continued until substantially all of the carbide 
particles are surrounded and at least partially embedded in the matrix 
alloy. 
While the foregoing method was particularly applicable to the production in 
the field of carbide-containing consumables, the rods produced had to be 
handled with care to avoid breakage during use. Apparently, in producing 
the rods by the foregoing method using a flame torch for applying the 
matrix metal, the material tended to oxidize, due to the fact that a 
slightly oxidizing flame was employed. Moreover, the composite rods 
produced did not always exhibit a uniform distribution of the carbide in 
the matrix alloy which is desirable. 
OBJECTS OF THE INVENTION 
It is thus an object of the invention to provide a method for producing a 
carbide-containing consumable of high quality. 
Another object is to provide a carbide-containing consumable in the form of 
a composite rod of high quality.

STATEMENT OF THE INVENTION 
One embodiment of the invention is directed to a method of producing a 
carbide laden consumable in the form of a rod comprising, providing a 
graphite mold having at least one elongated U-shaped groove therein 
containing a charge of fusible ingredients comprising a first layer of 
powdered self-fluxing matrix metal alloy at the bottom of the groove, a 
second layer of particulate metal carbide on top of said first layer and a 
third layer of said matrix metal alloy on top of the second layer. The 
composition of the matrix metal alloy and the refractory carbide taken 
together as charged in the mold ranges by weight from about 80% to 30% of 
the metal alloy and 20% to 70% of the refractory metal carbide. The 
self-fluxing matrix metal alloy employed is selected from the group 
consisting of Ni-base, Ni-Cu-base, Fe-base and Co-base alloys containing 
by weight at least one element selected from the group consisting of about 
0.1% up to 6% silicon (e.g. at least about 0.5%) and about 0.1% to 5% 
boron (e.g. at least 0.5%) having a melting point ranging up to about 
1370.degree. C., the refractory metal carbide being selected from the 
group consisting of carbides of W, Mo, Cr, Zr, Ti, Hf, Nb, Ta, V, B and Si 
and mixtures of at least two of said carbides. The self-fluxing alloy also 
includes nickel silver alloys. 
The mold is then passed through a furnace maintained at a temperature above 
the melting point of the matrix alloy, the furnace atmosphere being 
reducing and preferably comprising a hydrogen-containing atmosphere. 
Following melting and infiltration of the matrix alloy into the 
interstices of the carbide layer, the mold enters a cooling zone where the 
melted matrix alloy is immediately solidified. 
It is preferred that the mold be charged with the powdered ingredients in 
the manner described hereinabove. For example, if the refractory carbide 
particles are placed at the bottom of the U-shaped groove as similar to 
the method described in U.S. Pat. No. 3,523,569, and the matrix metal 
powder then placed on top of the carbide particles and the charged mold 
passed through a furnace on a conveyor, the composite rod produced will 
tend to have a bend in it, for example, a one and one-half inch bend for 
an 18 inch rod. 
On the other hand, if the charge is prepared by placing a portion of the 
self-fluxing matrix metal powder at the bottom of the U-shaped groove, the 
carbide particles on top and the carbide particles in turn covered by the 
remaining self-fluxing matrix metal powder, and the charge then melted by 
passing the mold through a conveyor furnace, a straight composite rod is 
obtained of improved strength and high quality as evidenced by a good 
clean composite structure. 
DETAILS OF THE INVENTION 
As stated earlier, a horizontal graphite mold is used with U-shaped grooves 
machined into the surface of the mold. A mold made of amorphous graphite 
has been found very satisfactory. An advantage of using the graphite mold 
is that it is a good conductor of heat. Being a black body, it absorbs 
heat quickly as it passes through the heating zone of the furnace whereby 
the charge is melted, the molten self-fluxing alloy penetrating the layer 
of refractory carbide via the interstices between the particles from below 
and above said carbide layer by which capillary and gravity flow. Since 
the melting of the self-fluxing alloy is fast and efficient, segragation 
of the carbide particles is substantially inhibited, the molten alloy 
penetrating the spaces between the carbide particles to form a 
substantially uniform structure. Thus, when the charged mold following 
melting soon after reaches the cooling zone, the molten matrix alloy 
immediately solidifies to provide a good clean composite rod of high 
quality in which the carbide particles are strongly anchored. 
For the self-fluxing alloys referred to, the melting temperature may range 
up to about 1370.degree. C. and generally from about 900.degree. C. to 
1250.degree. C. (e.g. about 900.degree. C. to 1150.degree. C.). 
A reducing atmosphere is employed, the furnace preferably having a flame 
curtain at the inlet end and one at the outlet end to prevent as much as 
possible air from bleeding into the furnace. 
Preferably, the reducing atmosphere in the furnace is a hydrogen-containing 
atmosphere, for example, hydrogen mixed with a substantially inert gas, 
such as nitrogen. Thus, the atmosphere may contain about 10% to 75% by 
volume of hydrogen and the balance nitrogen. Cracked ammonia is 
particularly preferred containing about 25% N.sub.2 and 75% H.sub.2 by 
volume. 
By using a hydrogen-containing atmosphere, such as cracked ammonia, no 
fluxing is necessary during the melting of the matrix metal and, moreover, 
hydrogen reduces any oxides in the powder. Because the atmosphere is 
inherently deoxidizing, the metal powder is cleaned up during melting and 
good sound composite rods are produced of high quality. In the case where 
the matrix metal is a nickel silver alloy, the hydrogen prevents the 
oxidation of the zinc, which is important since zinc oxide tends to be 
volatile. 
The more detail aspects of the invention will be clearly apparent by 
referring to the drawing and, in particular, FIGS. 1 to 4 which illustrate 
a typical embodiment of a graphite mold having utility in carrying out the 
invention. 
Thus, referring to FIG. 1, a mold 10 of amorphous graphite is shown in plan 
view which may be about 95 to 97 millimeters (mm) wide (approximately 3.8 
inches), about 506 to 508 mm long (approximately 20 inches long) and about 
25 to 30 mm thick (approximately 1.1 inches), the mold having 4 U-shaped 
grooves 11 therein which may be 456 to 458 mm long (approximately 18 
inches). Referring to FIG. 4, the dimensions of the U-shaped groove 11A 
are shown by the letters "A" (width) and "B" (depth). In keeping with the 
dimensions stated hereinabove, the width and depth may be 14 and 14 mm 
(approximately 0.55 inch). The term "U-shaped groove" is meant to cover 
V-shapes and variations thereof. 
Smaller sized grooves may be employed as follows in producing composite 
rods of about 18 inches long, with the width "A" and depth "B" of the 
U-shaped grooves being as follows: 
______________________________________ 
A B 
______________________________________ 
(1) 3 mm 3 mm 
(2) 5 5 
(3) 7 7 
______________________________________ 
The ends of the groove in FIG. 3 are provided with a radius R.sub.1, e.g. 
15 mm, the bottom of the U-shaped groove having a radius R.sub.2. Where 
the width and depth of the grooves are 14.times.14 mm, the radius R.sub.2 
may be 15 mm. 
As stated hereinbefore, in charging the grooves in the mold with the 
particulate ingredients (not FIG. 5), it is preferred that the ingredients 
be stratified so that in effect three layers are used, a first layer 12 of 
self-fluxing matrix metal on the bottom, a second layer 13 of particulate 
refractory carbide on top of the first layer, and a third layer 14 of the 
remaining self-fluxing alloy on top of the refractory carbide layer. 
It is preferred, however, that the U-shaped grooves be first provided with 
a mold wash to assure long life of the mold and to enable easy releasing 
of the cast composite rod from the mold. Fine pure aluminum oxide is 
preferred, although other refractory oxide mold washes can be employed, 
such as SiO.sub.2, MgO, CaO and the like. The mold wash material should be 
less than 200 mesh and at least 75% less than 325 mesh. Precipitated 
aluminum oxide of particle size less than 1.0 micron is preferred. A 
slurry of the oxide is produced in water and applied to the mold in 
several steps with drying in between until the desired coating has been 
obtained. 
Following application of the aluminum wash to the grooves in the mold, the 
grooves are charged with the particulate ingredients as shown in FIG. 5 
and the mold 10A placed on a conveyor 15 and passed through the heating 
chamber 17 of furnace 16, the matrix metal caused to melt in the heating 
zone or chamber 17 following which the mold 10A enters the cooling zone or 
chamber 18 where it reaches substantially ambient temperature and the mold 
10A unloaded as it exits from the cooling chamber. 
The furnace is preferably electrically heated, the cooling chamber being 
water cooled via heat exchanger tubes through which water is continuously 
passed. 
A typical composite rod 19 is shown in FIG. 7, a cross section thereof 
being shown in FIG. 8 comprising refractory carbide particles 20 of, for 
example, tungsten carbide, distributed through the self-fluxing matrix 
metal alloy 21. 
As stated hereinabove, a wide variety of self-fluxing alloy compositions 
may be employed, such as Ni-base, Ni-Cu-base, Co-base, and Fe-base alloys 
and certain of the nickel silver alloys, so long as the alloys contain at 
least one of the elements selected from the group consisting of by weight 
about 0.1% to 6% silicon and about 0.1% to 5% boron. Typical refractory 
carbides which may be employed include WC, MoC, Cr.sub.7 C.sub.3, ZrC, 
TiC, HfC, NbC, TaC, VC, B.sub.4 C, SiC, among others. The term "refractory 
carbide" is meant to include the foregoing and other refractory carbides. 
The carbides may be used alone or in combination of two or more. 
The foregoing self-fluxing alloys have good wetting properties and 
penetrate the layer of carbide easily. 
The compositions of such alloys are selected to provide a melting point not 
exceeding about 1370.degree. C., and preferably falling within the range 
of about 900.degree. C. to 1250.degree. C., e.g. 900.degree. C. to 
1150.degree. C. 
An alloy matrix containing predominately a metal of the iron-cobalt-nickel 
group has been found useful according to this invention. A suitable 
example of this type of base alloy is as follows: 
______________________________________ 
NICKEL-BASE MATRIX ALLOY 
Range in 
Percent 
Constituent by Weight Example 
______________________________________ 
Silicon 1.5-5.0 3.0 
Boron 1.5-5.0 2.0 
Chromium 0-20 1.0 
Molybdenum 0-7 0.2 
Nickel (1) (1) 
______________________________________ 
(1) Essentially the Balance 
The above alloy may be substituted in nickel content by cobalt or iron. The 
following matrix alloy is illustrative of cobalt-base compositions found 
useful. 
______________________________________ 
COBALT-BASE MATRIX ALLOY 
Range in 
Percent 
Constituent by Weight Example 
______________________________________ 
Nickel 1.0-5.0 3.0 
Chromium 26.0-32.0 28.0 
Silicon 0.5-3.0 1.0 
Boron 1.0-3.0 2.0 
Carbon 0.8-2.0 1.0 
Tungsten 3.5-7.5 4.5 
Molybdenum 0.0-0.5 3.0 
Cobalt (1) 57.5 
______________________________________ 
(1) Essentially the Balance 
Again, nickel or iron may be substituted in the above formulation for a 
like amount of cobalt. The iron alloy is harder and more resistant than 
the other but is more subject to corrosion and oxidation during 
deposition. 
A particularly preferred nickel-copper-base matrix alloy containing no zinc 
which has been found useful has the following constituents in percentages 
by weight as indicated: 
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NICKEL-COPPER-BASE ALLOY 
Intermediate 
Constituent Broad Range Range 
______________________________________ 
Nickel (1) (1) 
Silicon 1.0-5.0 3.0-4.0 
Boron 0.15-2.50 0.25-0.5 
Manganese 0.20-2.00 0.5-1.0 
Copper 15.0-40.0 20.0-28.0 
______________________________________ 
(1) Essentially the Balance 
As an example of a matrix alloy within the above ranges, there may be 
mentioned: 
______________________________________ 
Constituents Percent by Weight 
______________________________________ 
Nickel 23.00 
Silicon 3.45 
Boron 0.47 
Manganese 0.75 
Copper (1) 
______________________________________ 
(1) Essentially the Balance 
As stated hereinbefore, nickel silver is particularly desirable as a matrix 
alloy and may range broadly in composition by weight from about 2% to 20% 
nickel, 28% to 58% zinc, 0.1% to 1.0% silicon, 0.0 to 1.0% silver and the 
balance essentially copper (e.g. about 40% to 65%). 
The above illustrated iron, cobalt, copper-nickel-base and nickel silver 
alloys are particularly useful because they melt at relatively low 
temperatures. Thus, by using these low temperature matrix alloys, the heat 
initially used in the melting of the alloys is low and the individual 
particles are not subject to contact with extremely high heat. 
Additionally, these compositions firmly bind the carbide particles to the 
parent material following brazing. When the composite rod is ultimately 
deposited, a hard, shockproof surface is provided and the particles are 
not easily dislodged. 
The foregoing self-fluxing matrix alloys are sometimes referred to as 
follows: NiCrSiB, NiSiB, CoCrSiB, CoSiB, FeCrSiB, etc. 
The final composite rod may range in composition from about 20% to 70% by 
weight of refractory carbide and 80% to 30% by weight of matrix metal. 
Preferably, the refractory carbide may range from about 45% to 55% and the 
matrix metal from about 55% to 45% by weight. 
In producing the layered charge, between about 25% to 50% by weight of the 
total weight of the self-fluxing matrix metal powder is preferably placed 
as the first layer in the mold, with all of the particulate carbide placed 
on the first layer and the remainder of 75% to 50% of the total matrix 
metal added as the third layer. 
The particle size of the matrix metal alloy may range up to about 80 mesh 
in size (e.g., up to 50% below 325 mesh and ranging up to about 200 mesh). 
The size of the particulate refractory carbide may range from about 5 
microns to as high as 3/4 inch (19 mm) e.g., plus 60 mesh to 3/8 inch 
(about 10 mm). Where coarse carbides are employed, the cross sectional 
dimensions of the rod should be sufficient to anchor at least one-half the 
average thickness of the particles. 
As illustrative of the various embodiments of the invention, the following 
examples are given. 
EXAMPLE 1 
A mold of the type shown in FIGS. 1 to 3 having U-shaped grooves therein 
with a cross section of about 14 mm .times.14 mm and approximately 456 to 
458 mm long (about 18 inches) is coated with an alumina mold wash. The 
mold is then charged with the ingredients to provide a composition 
containing 50% by weight of tungsten carbide of particle size of about 
plus 100 mesh (U.S. Standard) to one-eighth size and 50% by weight of a 
nickel-base matrix alloy of minus 100 mesh containing by weight 3% 
silicon, 2% boron, 1% chromium, 0.2% molybdenum and the balance 
essentially nickel. 
About 40% by weight of the total matrix alloy powder is placed at the 
bottom of the grooves, followed by a layer of tungsten carbide and the 
remaining matrix alloy powder (60% by weight of the total matrix metal) 
placed on top of the carbide layer. 
The graphite mold with the charge is placed on a conveyor made of a heat 
resistant alloy (e.g. an alloy containing about 15% Cr, 7% iron and the 
balance essentially nickel and known in the trade by the designation 
Inconel) and passed through the furnace (FIG. 6) into a heating chamber 17 
maintained at a temperature (e.g. 1250.degree. C.) above the melting point 
of the matrix alloy using cracked ammonia as the atmosphere. The speed of 
the conveyor is such that the mold is in the heating chamber for about one 
hour. The nickel-base alloy below and above the carbide layer melts and 
flows into the interstices of the carbide layer by both capillary and 
gravity flow. 
The mold with the fused contents (mold 10A) then enters the cooling chamber 
18 where the matrix alloy is substantially immediately solidified and 
provides uniform distribution of the carbide in the matrix. The mold exits 
from the cooling chamber as shown in FIG. 6 through a protective curtain 
of burning natural gas to provide a straight composite rod of high quality 
and good strength. 
EXAMPLE 2 
A composite rod may be formulated using the method similar to Example 1, 
except that the carbide material is TiC with a particle size ranging from 
about -60 mesh to plus 100 mesh, the matrix alloy being a self-fluxing 
cobalt-base alloy containing 3% Ni, 28% Cr, 1% Si, 1% B, 4.5% W, 3% Mo, 
57.5% Co and the balance residuals. 
Half of the matrix metal powder of particle size substantially between 325 
mesh and 200 mesh is placed in the bottom of U-shaped grooves having cross 
sectional dimensions of about 7 mm wide by 7 mm deep, the grooves being 
about 457 mm long (about 18 inches). 
The carbide and matrix metal are proportioned together to provide a 
composite rod containing about 30% by weight TiC and 70% by weight of the 
matrix metal. The charged graphite mold with a previously applied mold 
wash coating is passed through the furnace as in Example 1 using an 
atmosphere of cracked ammonia, the temperature of the heating chamber 
being at about 1250.degree. C., that is, above the melting point of the 
self-fluxing cobalt-base matrix alloy. When the mold reaches the cooling 
chamber, the fused matrix alloy is rapidly cooled to provide a clean 
straight composite rod of good strength. 
EXAMPLE 3 
Another formulation which may be produced using the method of the invention 
comprises a commposition containing about 60% by weight NbC of particle 
size ranging from plus 60 mesh to one-eighth inch and balance a 
self-fluxing nickel-copper-base matrix metal containing about 23% Ni, 
3.45% Si, 0.47% B, 0.75% Mn and the balance essentially copper, the matrix 
metal having a particle size with up to 25% passing through 325 mesh 
screen and ranging up to about 200 mesh. 
As in example 2, half of the matrix powder is placed in the bottom of the 
U-shaped grooves of the mold having cross sectional dimensions of about 10 
mm wide by 10 mm deep and about 457 mm long (about 18 inches). 
The composite rod may be produced as in Example 2, to produce a clean rod 
of good quality and strength. 
Examples of other composite formulations for use in producing composite 
rods in accordance with the inventon are as follows: 
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Carbide % Weight MATRIX METAL % Wt 
______________________________________ 
SiC 20 3% Ni, 2% B, 1% Cr, 
0.2% Mo and balance Ni 
80 
Sintered WC 
60 48% Cu, 10.5% Ni, 0.5% 
40 
Fragments Si, 0.05% P, 0.3% Ag 
and balance Zn 
Cr.sub.7 C.sub.3 
45 0.7% C, 15% Cr, 4% Si, 
55 
3.2% B, 4% Fe and balance 
Ni 
______________________________________ 
Although the present invention has been described in conjunction with 
preferred embodiments, it is to be understood that modifications and 
variations may be resorted to without departing from the spirit and scope 
of the invention as those skilled in the art will readily understand. Such 
modifications and variations are considered to be within the purview and 
scope of the invention and the appended claims.