Note: Descriptions are shown in the official language in which they were submitted.
9347
,, ~
~ Z~88
The present invention relates to the hard
facing of substrates. More particularly, the present
invention relates to the hard facing of substrates using
as the hard-facing material a vanadium carbide-containing
composition to provide improved wear and impact resistance. ~ :
Hard facing of substrates, e.g. metal surfaces*,
is a common industrial practice, for example, cast
particulate tungsten carbide (W2C-WC) or cobalt bonded
WC, usually encased in a steel tube, is d~sited by hard
facing techniques on iron base alloys in making wear
resistant cutters, earth moving equipment and the like. -
It has been found, however, that due possibly to the
inherently different physical properties of base metal
and tungsten carbide, the hard facing material has a
tendency to become unevenly distributed in the molten
portion of the metal substrate and as a result, undesired
variations in hardness can occur in the resulting solidified
hard-faced surfaces.
Also, during the deposition of both cast and
cobalt-bonded tungsten carbide on iron and steel substrates,
the molten iron in the substrate dissolves some of the
tungsten carbide and upon cooling resul~s in the precip-
itation of the mixed carbides (FeW)6C and Fe3W3C according `
to the~formula 3WC~9Fe ~ Fe3W3G~2Fe3C, thus resulting
in substantial depletion of the deposited ~ungsten into
less wear resistant phase.
. .
:` *The Oxy-Acetylene Handbook, 11th Edition, Linde Air
Products Division of Union Carbide Corporation, also
Welding Handbook Third Edition, American Welding Society.
2. : ~ .
9347
~Z288
In instances where tungsten carbide is employed
in hard facing, due to the high density of tungsten carbide,
a relatively large weight of tungsten carbide is required
for adeauate hard facing.
It is accordingly an object of the present
invention to provide a hard-facing method using vanadium
carbide-containing material to produce a hard-faced
surface having wear-resistant properties at least
comparable to those provided by the use of conventional
tungsten carbide.
Other objects will be apparent from the following
description and claims taken in conjunction with the drawing
; in which Flgure 1 illustrates a known phase diagram for
vanadium, tungsten, carbon, and
Figure 2 shows the same phase diagram as Figure 1
utilizing weight per cent instead of atomic per cent for
defining vanadium-tungsten-carbon compositions.
The present invention is directed to an imProvement
. in conventional methods of hard-facing substrates which
comprises employing as the hard facing material a solid
material consisting essentially of at least one vanadium
carbide, and tungsten, when Present, in solid solution
with each vanadium carbide in said composition in an amount
up to the solid solubility limit of tungsten in each such
vanadium carbide, the aggregate amount of vanadium carbides
in said material being at least about 10% by weight, and
cobalt being present in an amount to about 50% by weight
of the aggregate vanadium, carbon and tungsten in said
3. ~ .
9347
~04~21!~
composition. :
The aforementioned material can be formed of
one of the vanadium carbides, or-in the form of a
mixture of two or more of such vanadium carbides, e.g.
VC type, V2C type and intqrmediate carbides. When
tungsten is present in the material, tungsten is in
-` solid solution with the vanadium carbide or carbides
in an amount ranging up to the solid solubility limit
of tungsten in such carbide or carbides. By way of
example, if the vanadium carbide in the material is
entirely VC type, tungsten can be in solid solution with
the VC in an amount up to about 25 atomic per cent of
the VC (region 100 in the Figure of the drawing) which is
~` the solid solubility limit of tungsten in VC type carbide.
Where the vanadium carbide in the material is entirely V2C
type, tungsten has unlimited solubility (region 200 in the
Figure o the drawing), however, the material in accordance
with the present invention is required to contain a minimum
; amount of vanadium carbide as previously mentioned. By way
2n of example, where a material is formed of both VC-type andV2C-type carbides, such as indicated at I in the phase
diagram of the drawing, the maximum amount of tungsten
in solution would be about 63.5% by weight; in such
material, of this percentage, about 23.7% would be in
.:. :
solid solution with VC-type carbide and about 39.8%
would be in solid solution with V2C type carbide.
` The foregoing solid solubility limit values
for tungsten are and the cornposition of specific V-W-C
;~
` ` 4
.~` \ j '.
; .`; . ! ;
- ~ 9347
~ 42 ~
materials for use in accordance with the present
in~ention determinable from the phase diagram of Fig-
~re 1 of the drawing which is known to the art.
In preparing a material such as indicated
at I in F~gure 1, the pe~centages determinable from
the phase diagram of the drawing for V, C, and W can
be used as the percentages of these materials in a
starting mixture containing elemental V, C and W.
The mixture can thereaf~er be processed as hereinafter
described. Alternatively, precombined vanadium and
carbon and precombined tungsten and carbon, providing
the same percentages in the starting mixture can also
be used. Also, where the starting materials are oxides,
e.g. V203, W03, additional carbon is provided in the
starting mixture to reduce the oxides to metal, e.g.
according to the general reaction:
M0 ~ C ~ MC ~ C0
In general, the starting mixture constituents
can vary within about 5% by weight of the aim values, an
additional amount, e.g. up to 5% by weight, carbon being
prov;ided when considered important to ensure removal of
incidental oxygen combined with the vanadium and/or
.~''`' ' ~.
~
.~i ~'''., ',.
,,, ~ ~ ,: ,
,
Y~/4
-` lV4Z~88
tungsten constituents of the starting material. For
particular processing apparatus and conditions, appropriate
spPcific starting material proportions can be routinely
determined.
As noted hereunder, when more than one vanadium
carbide type is present in the material, the tungsten can
be in solid solution in each of the vanadium carbides in
an amount up to the solid solubility limit of the respective
vanadium carbides, reference being ta~en of the requirement
that the material employed in the present invention has at
least a defined minimum amount of vanadium carbide. Tungsten
present in the material above the solubility limit or limits
will combine with carbon to form tungsten carbide, sufficient `~
carbon being used in the preparation of the material to
ensure that the material is substantially free, i.e. not
; more than 5% by weight, of elemental tungsten. Iron, nickel
and cobalt can be present in the above mentioned material
in an amount customarily used in the preparation of cemented
carbides and higher, e.g. up to about 50% by weight in the ;
aggregate, and preferably in the range of 0 to 18%
The hard facing material of the present invention
,` can alternatively be described as a composition consisting -
essentially of chemically combined vanadium and carbon and
: tungsten, where present, in solid solution with said chemically;
combined vanadium and carbon in an amount of from 0% by weight
of the composition up to th~ s~olid solubility limit of
tungsten in said chemically combined vanadium and carbon, and
up to about 50~/O by weight in the aggregate of cobalt, nickel
and iron, said chemically combined vanadium and carbon being
in an amount of at least 10% by weight of said composition.
- 6-
9347
' ``
~04ZZ8~3
The above described hard facing material for
use in the method of the present invention can also
adventitiously con~ain a relatively small amount, e.g.
up to about 5% by weight in the aggregate of incidental
materials such as free carbon, vanadium and tungsten.
While any known technique can be used for
producing the above described hard facing material from
conventional starting materials, including elemental
vanadium, tungsten and carbon, and vanadium and tungsten
oxides, the preferred form of Lhe hard facing material
for use in the method of the present invention is a
particulated cold pressed and sintered material
illustrated by examples in the present specification.
In these examples, the starting vanadium, carbon, tungsten
, . .
and cobalt materials are blended, compacted and sintered
under a hydrogen atmosphere at elevated temperatures, e.g.
about 1200-1600C and for periods, e.g. 1/2 to 3 hours,
sufficient to produce materials as aforedescribed.
A particular embodiment of the present invention
comprises a hard facing rod in conventional form for use ;
in hard facing metal substrates, e.g. iron,steel, cobalt,
nickel, aluminum, copper, magnesium and alloys of such
metals. Such a hard facing rod comprises a metallic
sheath or tube formed of the usual metals for such -
~: .
purpose such as iron, stee:L, aluminum, copper and the
` like containing therein a hard facing composition as
'~, ! .: ,
;~ previously described. ~-
. . .
,
7-
,,, , .;~.',',
9347
1(~4Z~38
The hard facing method of the present invention
can be used with known gas and electric welding techniques,
e.g. gas welding, arc we~ding and other practices described
in the "Master Chart of Welding Processes"-American Welding
Society (1969), using conventional fluxes. In the resulting
hard faced articles substantially all, 80~/o by weight or
more, of the applied vanadium carbide material and any -
dissolved tungsten is present in this form, i.e. vanadium
carbide containing tungsten in solid solution. That is
to say there is only a relatively slight, 5-20%, disso-
lution, i.e. depletion of the vanadium carbide or its
dissolved tungsten into the surface metal.
The hard facing method of the present invention
can also be used with known plasma flame spraying or
coating techniques ~'Flame Spray Handbook" Volume III
-METC0 INC. (1965).
In the hard facing of metal substrates in
accordance with the present invention by the above-noted
conventional techniques the metal substrate and the applied
hard facing material become metallurgically bonded. -
In a further embodiment of the present invention,
the herein described hard-facing material is bonded to
` non-metallic substrates using conventional adhesives such
as natural or synthetic rubber~like or resinous materials, `
e.g. thermosetting materials such as phenolics, polyesters,
~ crosslinked styrenated polyesters, thermoplastic materials
; such as polysulfones, epoxys, and cross-linked elastomeric
materials, e.g~ natural or synthetic rubbers. -~
.
, . . . . . . ~
9347
~)42~8~3
With reference to Figure 2 of the drawing,
which has been prepared for purposes of convenience by
converting ~he atomic weight per cent scales of Figure 1
to weight per cent, vanadium-tungsten-carb~n material for
use in the present invention at least 95% by weight of which
is in the fonm of vanadi~m carbide, and tungsten, when
present in solid solutiong and containing at least about
10% of a vanadium carbide is found in the region designated
A comprising regions 100', 200', 300', 900 and 1000. A
particularly preferred material is that defined by region
j 100' wherein tungsten, when present, is in solid solution
with VC type carbide. In region 200', tungsten when present,
` is in solid solution with V2C type carbide and in region
300' tungsten, when present, is in solid solution with VC
; and/or V2C ~ype carbides. Compositions somewhat outside
of region A are also suitable for use in the practice of
; the present invention. For example, a composition in
region 600', slightly above region 100', would contain
uncombined carbon and provided that this uncombined carbon
does not exceed about 5% by weight of the material, is
suitable for the practice of the present i~vention.
.~ ,
`, Similarly, compositions of regions 700', 800', 900' or
1000, 1200, 1300 and 1490 containing not more than about
.j ,,
5% by weight uncombined, C, WC, W and/or V are suitable
for use in the practice of the present invention.
A V-W-C composition found to be particularly
advantageous for use in accordance with the present invention
contains from about 10 to 67 per cent by weight
tungsten in solid solution.
' ' 9
; ~:
^. ~ ` 93~7
,Z288
The following examples illustrate materials
for use as hard-facing compositions in accordance with
the present invention:
Example I
The following materials were used to obtain a
cold press~d sintered hard-facing composition of VC type -
material having about 50-60 weight per cent tungsten in
solid solution and containing about 6% by weight cobalt
for use in the process of the present invention:
(a) 1978.4g of a commercially available
material (Union Carbide Corporation) containing
mixed V2C+VC, sized 65 mesh and finer having the
following analysis:
82.26% V
14.24 C
` 0.70 0
0.50 Fe
Balance moisture and incidental impurities.
(b) 1412.0g UCAR* tungsten powder, deagglomerated,
:' 20 F.S.S. - 2.0 microns.
(c) 192.0g Acheson* brand G39 graphite powder, -
sized finer than 100 mesh.
; (d~ 242.49 cobalt powder, extra fine grade from African
Metals Corp. :
--.. . -
The powders were placed in a ball mill (8-in.
diameter x 11 in. high, 48.4 lb. of 1/2-in. dia. balls)
; and turned at 52 RPM for 48 hours. After forty-eight
hours milling, the material was cold pressed by pelletizing
in a 1-1/2-in. dia. die at abou~ 38,000 psi.
.
`~ *Trademark of Union Carbide Corporation.
10 . .
. .~ ' .
9347
~ 8~
The compacts (apparent density ~ 5.14gr/cc) were crushed
in a pulverizer and sized to 12 X 20 mesh. The resulting
granules were placed in graphite boats and sintered in a
pure hydrogen push through molybdenum-wound heat-treating
furnace. The sintering cycle was as follows: The graphite
boat was placed inside the furnace door for 1/2 hour, to
diffuse out residual atmospheric gases. The boat then was
advanced to a 900-1200C. zone to allow the reduc~ion of
any residual oxides and ~he removal of the reduction
products. Thenthe boat was advanced into the hot zone
at 1400C. for 1-1/2 hr. to provide sintering of the cold
pressed material. The boat was then pushed out of the
hot zone into a water-cooled chamber and brought to
room temperature in 12 minutes. The granules were lightly
bonded together but were easily separated in a jaw crusher.
~, Aside from the contained cobalt, at least about 95% by -
weight of the material was formed of chemically combined
vanadium and carbon having tungsten in solid solution. `~
The cold pressed and sintered material as ;
prepared in the foregoing example was sized 12 X 32 mesh
in a jaw crusher and employed as a hard-facing material
in the following manner. ;
i; The granules were packed into a 12-in. length
of 1/4-in. O.D. by nominal .l90-in. I.D. mild steel tubing.
.
`.: . '" '
11. : ..:
; ~ .
. , ., , -. .... , .. . . ~ .
., , , . . . : . . , . ~ . . . . ..
9347
: L04Z2~8
The granules composed about 45% by weight of the rod.
The rod then was deposi~ed on a plain carbon mild
steel substrate using an o~y acetylene torch. The flame
was acetylene-rich to prevent decarburization At
the starting point, the metal substrate was brought to
sweating temperature, i.e. the surface was brought to the
melting point, and the rod deposited with a minimum of
penetration of the substrate. The melted metal casing
bonded the granules to the substrate and a metallurgical
1~ bond was formed between the hard facing material and
substrate upon solidification of the molten metal.
The resulting hard-faced surface was found to
be at least comparable in wear resistance to that obtained
using cast ~tungsten carbide as the hard-facing material.
A particular advantage of using the above-
described material in hard-facing practices is that the
amount o~ vanadium carbide can be varied from essentially
100% in the form of combined vanadium and carbon to a
material containing up to 90% by weight WC while providing
excellent wear resistance, impact resistance,and hardness -
at least comparable to conventional tungsten carbide.
' Thus the ratio of combined vanadium and carbon, and tungsten
can be varied to adjust the density of the material so as
to be substantially the same as the density of the fused
portion o~ the metal substrate to be hard faced. Consequently
even with light metal substrates such as aluminum, the density
of hard-~acing material in accordance with the present inven-
tion will not have to be more than about 50% greater than
12.
9347
1~4 2'~
the molt~ surface. As a result, a uniform distribution
of the hard-facing material in the melted portion of the
substrate is greatly facilitated. Alternatively, the density
of the hard-facing material can be readily adjusted, if
desired, so that more hard-facing material will be in
the lower portion of the melted substrate and vice versa.
A further advantage of the present invention is ;
that in using vanadium carbide material,in place of tungsten
carbide,as a hard facing material, the weight of the ;;
hard facing material used in a given application can be
reduced by as much as 65% as compared to conventional
cast tungsten carbide.
The following Table I shows various density
values for exemplary materials in accordance with the
practice of the present invention having the empirical
Gompositions. The measured density for cast tungsten
,.
carbide is also shown in the Table. ;
' ~,', :
: :
'.
' '~
".
... ... . .
:
~ i ~. . .
13.
" :
9347
1(~42~8~
a
a~ bO
00
~q C~l
a
X ~ .
g ~ ~ .
.,
~ C~
.,,
~g ~
o :,
o :, ,
- - :
" ~ .,
,: :
, "
C~ U U
C~
~n
p~
~ ~1bO ~ 00 4 '
,~ ~n r~ I~ o~ 1~
r~ oo oO ~ ' '
.
~1
o,
r~ ~)
~rl
~n ~ , . .
o
` ~ 3 ~ :
U~ o o
~~ ~ ~ .
+ +
o ~ ~ P ;'-
.'j
!
.,, ! \
.' ~
, .
14.
,, .
~, . . .
9347
,
~ 4ZZ88
Example II
A mixture of mixed VC+V2C material, elemental
tungsten, and graphite was prepared to obtain a cold ;
pressed and sintered hard facing composition of VC
type material having about 50-60% by weight tungs~en in
solid solution for use in the method of the present invention. -~
The tungsten was UCAR* tungsten powder having an average
particle size 2.5 microns; the vanadium carbide mater~al
~commercially available from Union Carbide Corp.) was
sized 65 mesh and finer; the graphite was Acheson* G39
; 10 powder, sized 200 mesh and finer. The amounts of W,
vanadium carbide material and graphite in the mixture were:
(a) Tungsten759.95g ~
~:.... ................ .............. ........................ . :.:'.' -'
i` J12 5.3/oC 1130.4g
C 0.86%
0.50%Fe
~Balance moisture and incidental
impurities
(c) Graphite 136.4g
The above constituents were charged to a
stainless steel ball-mill, 5-3/4-in. high having an
inner diameter of 6 in. The milling media was 8100g
., .
;, of steel 1/2-in. diameter balls. The mill was turned at
' 76RPM for a total milling time of 100 hr. The blended
~ mixture wa8 cold pre~qed into compactq at 38 ,non pqi . rhe
compAct~ h~d dlmen~lon~ of 1-1/4 lnch dlnmeter l~y I Jn~h
thick. Density of the cold pressed material was 5.028g/cc.
^ The cold pressed material was granulated to 40 X 200 mesh
; *Trademark of Union Carbide Corporation.
; 15. -
9347
~ ~2'~8
by crushing and screening. The resulting granules were
placed in graphite boats and furnaced in pure hydrogen ln
a molybdenum element push-throu~h furnace. The boats
were introduced into a 900-1200C. zone and held there
for 1/2 hr. to cause reduction of any incidental metal
oxides. After this the boat was pushed into the hot zone ;
and sintered at 1400C. for 1.5 hours. The boat was then
pushed into a water-cooled chamber and brought to room
temperature in about 12 minutes. The granules were easily
separated into a size of 48 to 250 mesh by passing through
a jaw crusher. At least 95% by weight of the material
; was formed of chemically combined vanadium and carbon
having tungsten in solid solution. The apparent density
of the sintered cold pressed material was 6.45g/cc.
Example III
A mixture of mixed VC+V2C material, elemental
tungsten, elemental cobalt and graphite was prepared to
obtain a cold pressed and sintered hard ~acing composition
of ~C type material having about 50-60 weight per cent
tungsten in solid solution and containing about 1% by
weight cobalt. The tungsten was UCAR* tungsten powder
having an average particle size of 2.5 microns. The
vanadium carbide material was sized 65 mesh and finer
(commercially available from Union Carbide Corporation).
, The cobalt powder was extra fine grade from African Metals
Corporation having an average particle size of 1.31
microns. The graphite was Acheson* G39 powder (available
.' '
*Trademark of Union Carbide Corporation.
.~
` 16
. ~, . . . .
9347
~0 4 2 ~8 ;
from Union Carbide Corporation), sized 200 mesh and finer.
~ The amounts of W, Co and graph~te in the mixture were
as follows:
~a) Tungsten 750.96g
(b) Mixed VC+V2C ~85. 90~/DV 1130.4g
1 12.53%C
C~ 0.50~/OFe ::~
1 0.86%0
~Balance moisture and
incidental impurities
(c) Graphite 136.4g ~ -
(d) Cobalt 20.2g
The above constituents were charged to a
stainless stee~l ball-mill, 5-3/4 in. high having an
inner diameter of 6 inches. The milling media was
8100g of steel 1/2-in. diameter balls. The mill was
turned at 76 RPM for a total milling time of 100 hrs.
The blended mixutre was cold pressed by roll compacting ~
into sheet. A bar pressed at 31~200 p~i from the `,
, 20 sheet had a green density of 5.323g/cc. The cold
compacted sheet material was granulated to 10 x 28 mesh
and the ~ranules were placed in a graphite boat and
furnaced in pure hydrogen in a molybdenum element push-
.. ; ~ .
through furnace. The boats were introduced into a
200C. zone and held there for 1/2 hr. to eliminate
, I I - i,,,, . ~.. .
air and moisture. The boats were advanced into a 900- `
,' 1100C. zone and held there for 1/2 hr. to cause reduction
of any incidental metal oxides. After this the boat was -
placed in the hot zone and the material sintered at 1400C.
~i ~or 1.5 hr. The boat thenwas pushed into a water-cooled
:. '.
17.
: .
~ 9347
:
~Z Z~8
chamber and brought to room temperature in about 12
minutes. The granules were easily separated by passing
through a jaw crusher and sized 12 to 30 mesh. Aside
from the contained cobalt at ~east g5% by weight of the
material was formed of chemically combined vanadium and
carbon having tungsten in solid solution. The apparent
density of the sintered cold compacted material was
6.4g/cc.
- EXAMPLE IV
A mixture of mixed VC+V2C material, elemental
cobal~ and graphite was prepared to obtain a cold pressed
and sintered hard facing composition having an empirical
composition of VC~3%Co for use in the process of the
presen t invention. The vanadium carbide material was ~-
~ ''
sized 65 mesh and finer (commercially available from
Union Carbide Corporation). The cobalt powder was extra
fine grade from African Metals Corporation having an
average particle size of 1.31 microns; the graphite
was Acheson* G39 powder, sized 200 mesh and finer. The
proportions were such as to produce a final product
containing vanadium, carbon and cobalt in the empirical
~-` relationship of VC+3%Co. The amounts of vanadium ,
carbide material, cobalt and graphite in the mixture
were as follows:
(a) Mixed VC+V2C ~85. 90D/oV 10 lbs.
12.53%C
~ 0.86~/~
., O . 50~/OFe
~Balance moisture and
inciden~al impurities
` (b) Co 0.330 Lb.
(c) Graphite 0.836 Lb.
*Trademark of Union Carbide Corporation
18.
, .
,
,
9347
~ ``
~ 2~ ~
The above constituents were charged to a
stainless steel ball 5-3/4 in. high having an inner
diameter of 6 inches. The milling media was 6000 grams
of steel l/2-in. diameter balls. The mill was turned
at 76RPM. Milling was continued for a total milling
time of 48 hours. The green density of the compacts
cold pressed from the mixture at 38,000 psi was measured
.
at 3,678 grams/cc. The blended mix was cold pressed by roll
compacting into sheet and granulated to 10 X 28 mPsh.
The granules were placed in a graphite boat and furnaced
in pure hydrogen in a molybdenum element push-through
sintering furnace. The boats were introduced into a
200C. zone and held there for 1/2 hr. to eliminate air
and moisture. The boats then were advanced into a
900-1100C. zone and held there for 1/2 hr. to cause
reduction of any incidental metal oxides. After this
the boats were pushed into the 1300C. zone for 1-1/2 ;
hours to ~inter the cold compacted material. The
. ~
sintered material was then pushed into a water-cooled
chamber and cooled to room temperature in about 12 minutes.
The granules were easily separated by passing through a
:~ ~ ., .:
jaw crusher and sized to 12 x 30 mesh. At least 95% by
weightof the material was in the form of vanadium
monocarbide (VC).
`: , ':
' ~' .
,` 19. .'
93~7
.
~4Z~8
EXAMPLE V
A mixture of V203, elemental cobalt and graphite
wasprepared. The V203, had an average particle size of
200 mesh and finer; the cobalt powder was extra -Eine grade
from African Metals Corporation, having an average particle
size of 1.31 microns; the graphite was Acheson* G 39. The
proportions were such as to produce a cold pressed and
sintered hard facing composition final product
having an empirical composition o~ VC-3Co for use in the ~'
method of the present inventicn. The amounts of V203,
, cobalt and graphite in the mixture were as follows:
(a) V203 1814.4g
, (b~ Co 46.6g
(c) Graphite 723.0g
The V203, cobalt and graphite constituents
, were charged to a stainless steel ball mill, 8.0-in.
high having an inner diameter of 9.75 in. The milling
media was 15.5 lb. of tungsten 1/2-in. dia. balls. The
mill was turned at 64 RPM. The mix was ball milled for
16 hrs. The milled mix was roll compacted to sheet
. ,
, . ....
(density 2.428grams/cc) and granulated to 8 X 12 mesh.
The granulas were packed in graphite boats and furnaced
in pure hydrogen in a platinum-wound tube furnace. The
boats were heated to 1150C. and held for 2 hrs. in
flowing hydrogen. The temperature was increased to
*Trademark of Union Carbide Corporation
,, .
20.
';
- , : ,
9347
. ,
~04Z~38
to 1300C. and held for 2.5 hrs. The granules were
easily separated by passing through a jaw crusher and
sized to 12 X 30 mesh.The material was in the form of
vanadium monocarbide, VC type,~resent as somewhat spherical
crystals in a relatively soft cobalt matrix and contained in
addition to combined vanadium and carbon, 2.73% free carbon.
EXAMPLE VI
':
A mixture of mixed VC+V2C (commercially
available from Union Carbide Corporation) material,
elemental iron and graphite was prepared to obtain a
. , .
cold pressed and sintered hard facing composition having
an empirical composition of VC+2~/OFe. The amounts of
vanadium carbide material, iron and graphite in the
mixture were as follows~
~a) Mixed VC~V2C r83. 66~/oV 200g. l `
14.14%C
O ~ 88~/oO
alance moisture and incidental
impurities
(b) Fe 4.27g.
(c) Graphite 12.48g.
The above constituents were placed in a 2-qt. !
.j . . . . .
ball mill together with 10.25 lb. of 112-in. diameter
steel balls. The mill was turned for 16 hrs. at 105
., 1. .. .
RPM. The powder was removed, roll-compacted and
granulated to 10 X 28 mesh with a bulk density of
.: 1, .
31.80g/in. 3. The granules were placed in a graphite boat ~ ~
' !:. . .
and sintered in pure hydrogen in a molybdenum element push
through furnace for 1.5 hrs. at 1300C. The sintered
30 material was then pushed into a water-cooling chamber
1'
21.
.:
- . . .. , . , : . , - ~ .,~ .: ., : - . ., -
, 9347
~4Z28~3
and bro~ght ~o room tem~erature in about 12 min. The
sintered granules were lightly bonded but easily
broken down in a jaw crusher. The bulk density of the
sintered granules, sized 12 x 32 mesh was 42.91g/in.3.
The vanadium and carbon in the cold pressed and sintered
,material were combined in the form of monocarbide (VC).
EXAMæLE VII
A mixture of V203, W03, elemental cobalt and
graphite was prepared to obtain a cold pressed and
sintered hard facing composition of VC type material having
about 20-25 weight per cent tungsten in solid solution
' and containing about 13.5% by weight cobalt for use in
the method of the present invention. The V203 had an
average particle size of 200 M x D; the W03 had an
average particle size of 100 mesh and finer; the cobalt
powder was extra fine grade from African Metals Corporation,
having an average particle size of 1.31 microns; the
graphite was Acheson* G39 powder, sized 200 mesh and
iner. The amounts of V203, W03 cobalt and graphite in
the mixture were as follows:
(a) V203 299.80g
(b) W03 96.0g
(c) Co 53.0g
(d~ Graphite 137.85g
The V203, W03 cobalt and graphite constituents
; were charged to a 2 quart mill. The milling media was
6.25 lb. of steel 1/2 inch diameter balls. The mill was
.: .
' *Trademark of Union Carbide Corporation.
2~.
: . . . . . .
.. . . . .
9347
~4 ~Z~ 8
turned at 95 R~M. The mix was ball milled for 24 hrs.
The milled mix was cold pressed by roll compacting to
pelletsl" dia. by 1/2" thick (density 3.04 grams/cc).
The pellets were packed in graphite boats and ~urnaced
- in pure hydrogen in a platinum-wound tube furnace. The
boats were heated to 1000C. and held for 4 hrs. in
flowing hydrogen. The temperature was increased to 1400C.
, and held for 2 hrs. The sintered pellets were crushed to
32 x 48 mesh. The resulting material had an apparent '
density of 5.82g/cc and a bulk density of 44.5g/in.3.
The tungsten, vanadium and carbon in the material were
in the form of a solid solu~ion of W in VC and the
,:' . : - .
material contained 13.5% Co.
1, l :
EXAMPLE VIII
The following materials were used to obtain a
1 cold pressed sintered hard-facing composition of VC
; type material having about 20-25 weight per cent tungsten
in solid solution and containing about 3% by weight cobalt
for use in the process of the present invention:
(a) 69.152 lbs.of a commercially available
material (Union Carbide Corporation) containing
mixed V2C+VC, sized 65 mesh and finer having the
following analysis:
; ~84.69% V
13.20 C
' ' 1. 10 0
0.50 Fe
; Balance - moisture and incidental impurities.
23-
.. . . . .. ..
9347
:~ .
.
~4~Z~
; (b) 22.763 lbs. UCAR* tungsten powder,
deagglomerated, F.S.S. - 2.0 microns.
(c) 5.422 lbs. Acheson* brand G39 graphite
powder, sized finer than 100 mesh.
j (d) 3 lbs. cobalt powder, extra fine grade from African
Metals Corp.
The powders were placed in a 2 cubic foot ball mill
with 500 lbs. of 1/2 in. diameter steels balls, and
turned at 36 RPM for 48 ho~rs. After forty-eight hours
milling, ~ portion of the material was cold pressed at
about 38,000 psi; the cold pressed material had a density
of 4.219gr/cc. The material was roll compacted to sheet
and crushed and sized in a pulverizer to 10 x 20 mesh.
The apparent density was ~ 5.14gr/cc. l`he resulting
granules were placed in graphite boats and sintered in a
pure hydrogen push through molybdenum-wound heat-treating
furnace. The sintering cycle was as ollows: The
graphite boat was placed inside the furnace door for 1/2
hour, to diffuse out residual atmospheric gases. The
boat then was advanced to a 900-1200C zone to allow the
reduction of any residual oxides and the removal of the
reduction products. men the boat was advanced into the
hot zone at 1550C. for 1 1/2 hrs. to provide sintering
.'!
of the cold pressed material. The boat was then pushed out
~ of the hot zone into a water-cooled chamber and brought
; to room temperature in 12 minutes. The granules were
lightly bonded together but were easily separated in a
jaw crusher. Aside from t~e contained cobalt, at least
*Trademark of Union Carbide Corporation.
` 24-
. ~ . . .
9347 -
~ 4 Zz8 ~
about 95% by weight of ~he material was formed of
chemlcally combined vanadium and carbon having tungsten
in solid solution.
The material prepared in the foregoing ~-
example was sized 12 x 32 mesh in a jaw crusher for use
as a hard-facing materlal.
The chemical analysis ~yweight of the material
was as follows:
13.40% C
56.24% V
23.55% W
3.46% Co , ;
1.26% ~e* ~ -
Considering only the V, C and W constituents the percentages
are as follows: `
C 14.37% by weight 47.46 Atomic %
W 25.27% by weight 5.46 Atomic %
V 60.34 % by weight 47.06 Atomic %
_ .. . . . . . _ . . . . .
In a particular embodiment of the present
invention an additional amount of finely divided tungsten
and carbon is used in the preparation of the hard facing
material as a constituent of the starting material mixture,
so that in addition to a solid solution of tungsten in
one or more vanadium carbides, the hard facing material
':! . :
can also contain in an intimate sintered admixture therewith,
.'
.i
` ~increase in iron content from grinding equipment used.
' 25
~ 9347
3L~42~8
up to 90% by weight of tungsten carbide. This material can
be used in the hard facing method of the present invention
to accomodate a desired density in the hard facing material
which may be advantageous in hard facing particular metal
substrates.
~ In another embodiment of the present invention,
,, the hard facing material of the present invention contains
up to 90% by weight chromium carbides. This is achieved
by including chromium metal or chromium oxide together
with additional carbon in the preparation of the hard
facing material as a constituent of the starting material
mixture, or by admixing chromium carbide with separately
prepared hard facing material in accordance with the
;~ present invention as hereabove described.
; The mesh sizes referred to herein are Tyler
series.
.,. :
.' , .
.
26.
,: :
- . . . . ~ . . , ... , . . , ~ . ~ .
