Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
87~9~0
The present invention relates to the deposition
of ruthenium, in particular by the so-called chemical vapor
deposition method.
In a chemical vapor deposition method ruthenium
may be deposited on a surface of a substrate by heating the
surface and decomposing the vapor of a ruthenium compound
on the hot surface. Various ruthenium compounds, such as
ruthenium carbonyl chloride, ruthenium~penta ~trifluorophos-
phine) [Ru (PF3)5] and ruthenocene have been proposed as
sources of the vapor. However, these compounds are unsuit-
able for general use because the rates of deposition of
ruthenium that can be obtained are very low, i.e., of the
order of 0.2 ~m (micro-meters) average thickness per hour
(~m/h), and so can only really be used to deposit thin
coatings. Indeed, it is often difficult to produce from
these compounds even thin deposits which adhere to the sub-
strate. Furthermore, the compounds are often difficult or
expensive to prepare, and some of them corrode the sub-
strate. For example, ruthenocene and ruthenium penta
(trifluorophosphine) are both difficult, and therefore ex-
pensive to prepare. Ruthenium carbonyl ahloride corrodes
some substrates and is also difficult to prepare because it
is difficult to obtain a consistent product, and this lack
of consistency in the product can show up as a substantially
involatile form of the carbonyl chloride, which decomposes
before it can volatilize.
Because of the foregoing difficulties in chemical
vapor depositing ruthenium, attempts have been made to de-
posit ruthenium by other routes, for example, by electro-
depositio~. It has been proposed to electrodeposit ruthenium,
~L~137~4C3
osmium, or an alloy of these two elements on to at least
the surfaces adjacent ~o the cutting edge or each such
edge of a tool suitable for cutting metal or other material,
such as rock, to increase the cutting life of the tool.
However, electrodeposition has the disadvantage that the
surface to be coated has to be thoroughIy cleaned and,
usually, etched. Further, because many ruthenium electro-
platinq baths are very acid, it may be necessary to protect
the surface to be coated by first giving it a flash coating
of an acid-resistant metal, such as gold or palladium. The
gold or palladium does not substantially add to the cutting
life of the tool, but does add to the expense of the process.
The coating of ruthenium on the tool should
generally be at least 2 ~m (micro-meters) in average thick-
ness. The methods of chemical vapor deposition referred to
hereinbefore are unsuitable for depositing such a coating,
especially as the deposition rates are too low for the thick-
ness re~uired.
However, we have surprisingly found a process for
depositing ruthenium, which makes it possible to deposit
ruthenium on a substrate at a rate which can be at least three
times faster than earlier processes and is great enough to
be suitable for commercial manufacture of relatively thick,
even coatings of ruthenium over all faces of a substrate.
It is an object of the present invention to pro-
vide a novel process for vapor depositing ruthenium.
Another object of the present invention is to pro-
vide a process for rapidly depositing ruthenium from a vapor
containing a chemically combined form of ruthenium.
-- 2 --
:~1370~(3
A still further object of the invention is to pro-
vide novel improved cutting tools having a hard, cobalt-
bonded carbide substrate and a superficial layer enriched
in ruthenium deposited by the process of the present invention.
Other objects and advantages will become apparent
from the following description taken in conjunction with the
drawing which shows a schematic diagram of experimental appa-
ratus used to carry out the process of the present invention.
According to the present invention there is provided
a process in which metallic ruthenium is deposited on a hot
substrate by decomposing thereon, in a substantially static
partial vacuum, vapor of a complex of ruthenium with a 1, 3
dione compound of formula Rl-CO-CHR2-CO-R3, wherein each of
Rl and R3, which may be the same or different, is an alkyl,
haloalkyl, alkoxy, aryl, (e.g., phenyl), or alkyl-, nitro- or
halo-substituted aryl (e.g., phenyl) group and R2 is a
hydrogen atom or an alkyl or haloalkyl group.
The 1, 3 dione compound (alternatively known as a
~ dicarbonyl compound) from which the complex is derived must
have at least one hydrogen atom on the 2-carbon atom, as can
be seen from its formula. Preferably the Rl and R3 groups
are alkyl or haloalkyl, especially alkyl or perfluoroalkyl.
Preferably R2 is a hydrogen atom. In an especially preferred
1, 3 dione compound for complexing with the ruthenium Rl and
R3 are the same and are both methyl groups, and R2 is a hy-
drogen atom, the compound being acetylacetone (pentan-2,
4-dione~, which is readily available and relatively inexpen-
sive. Other preferred 1, 3 dione compounds are trifluoro
(acetylacetone) (CF3.CO.CH2.CO.CF3) and hexa-fluoro (acetyl-
acetone) ~CF3.CO.CH2.CO.CF3).
~87~4~
The complex of ruthenium with these 1, 3 dione
colnpounds usually can be considered as containing one ru-
thenium (III) ca-tion ~ith three anions derived from thc
1, 3 dione compound, the three anions usually being the same.
For example, the complex of ruthenium with three molecu]es
of acetylacetone is tris(acetylacetonato) ruthenium III,
which is hereinafter referred to as Ru (acac)3.
These complexes may genera]ly be readily ~repared.
For example, Ru (acac)3 mav be prepared as a red crystalline
powder by reacting acetylacetone with ruthenium (III) chlo-
ride, as described by G. A. Barbieri, in A-tti. Acad. Linc .,
23, (5) I, 336, (1914). It>may be necessary to purify the
complex, e.g., by recrystallization, as the presence of
certain impurities may lead to the formation of non-adherent
deposits of ruthenium. For example, the deposit formed at
first may be black and not adhere to the substrate, and
~lthou~h this black deposit can be coated with a metallic
coating, the deposit as a whole does not adhere to the sub-
strate. Alternatively, it is sometimes possible to carrv
out a dummy run until the black deposit is no longer formed,
and then coat a fresh substrate with a deposit, which is
metallic and adheres to the substrate.
In the process of the present invention there are
interactions between the nature of the complex, the pressure
used in the substantially static partial vacuum, and the
temperatures of the source and of the substrate. These in-
teractions will be described in more detail hereinafter.
In a preferred embodiment of the process of the
present invention, the vapor of the ruthenium complex is
provided by subliming a solid complex, which acts as a
::
~370~0 -
ruthenium source. As heating the complex can cause it to
decompose without vaporising, the heating should preferably
be carried out so that the solid complex is sublimed substan-
tially without decomposition. If the complex may melt, care
should be taken to reduce or avoid loss of the complex by
liquid low.
The vapor obtained by heating the complex must be
decomposed in a substantially static partial vacuum. ~ par-
tial vacuum can be static or dynamic. A static partial vacuum
may be produced by pumping a vessel down to a desired pressure
and then turning off the pump, for example, by closing a
valve between the vessel and the pump, so that the vacuum is
not pumped during deposition of ruthenium. A dynamic partial
vacuum may be produced by pumping a vessel down to a desired
pressure and continuing the pumping during deposition of the
ruthenium to try to maintain the desired pressure or lower ;
il: further. By a "substantially static partial vacuum" is
meant either a static partial vacuum or a dynamic partial
vacuum ln which the conditions are in substance the same as
in a static partial vacuum; for example, the pumping is only
very gentle. Preferably the partial vacuum is a static par-
tial vacuum, which is not pumped at all during deposition of
ruthenium. A dynamic partial vacuum either produces no
deposit or one very slowly, so that in practice only thin
coatings can be obtained using a dynamic partial vacuum. If
a dynamic partial vacuum is used the throwing power of the
deposition process is very poor and most of any deposit formed
appears on faces of the substrate nearest to the source of
the vapor. In contrastl if a static vacuum is used, the
throwing power is good and a more or less uniform coating
~87~
is d~posited over all faces of the substrate. It is believed,
but the applicants do not wish to be bound by this belief,
that it is impressed motion of the vapor past the substrate
caused b~ the pumping that is important. The smaller this
impressed motion is the better; in an unpumped partial vacuum
it will be substantially nil.
Pressures quoted in this specification were measured
in the following manner. The volume was pumped down to the
required pressure and the pressure taken as that measured by
a McLeod gauge just before the volume was closed and before
heating commenced. A McLeod gauge is a vacuum pressure gauge
in which a sample of low-pressure gas is compressed in a known
ratio until its pressure can be measured reliably. For
pressures high enough to be reliably measured directly by a
mercury manometer, the McLeod gauge can be replaced by a mer-
cury manometer. Other methods of meaSuring the pressure may
be used, in which case allowance must be made for any way
in which these measurements may diEfer from those obtained
with a McLeod gauge (or mercury manometer) and unheated gas.
The maximum pressure that can be used in the substan-
tially static partial vacuum depends upon the volatility of
the complex and its decomposition temperature. The lower the
decomposition temperature, the lower is the temperature that
should be used for the volatili2ation. At a given volatill-
zation temperature, the lower the pressure used, the greater
is the volatilization of the complex. Therefore, the pressure
must be chosen so as to give, at a temperature below the
decomposition temperature, a volatilization rate for the com-
plex sufficient to provide a ruthenium deposit on the substrate
at the desired rate. For example, with Ru (acac)3 a visible
--6--
~, ~ !,;; . '. , ' ' ' ' , , ' ,
~ 87~
deposit is slowly formed at a pressure of about 100 mm
(millimeters) of mercury (100 torr) using a volatilisation
temperature of 210C and substrate (decomposition) tempera-
ture of 580C. At a pressure of 10 torr the rate is, under
otherwise the same conditions, about 4 ~m/h. The pressure
is preferable no more than 0.5 torr and is preferably 10 2
to 10 3 torr as under a pressure of about 10 2 torr, and
otherwise the same conditions, a coating rate of about
15 ~m/h can be obtained. There is no lower limit to the .
pressure, but the vacuum is always only partial as there is
always some vapor of ruthenium complex present during deposi~
tion. With a more volatile complex it would probably be
possible to operate at an even higher pressure than 100 torr.
Apart from vapor of the complex, inert gases, such as nitrogen,
may be present and also low pressures of gases such as air
may be present. For example, at pressures of about 10 1 to
10 3 torr, air may be present with the vapor.
As regards vaporization of the source, the more
volatile the complex used as source, the lower can be the
temperature of the source. For a given ruthenium source and
pressure there is usually a range o suitable source tempera-
tures to provide the necessary volatilization, and for a given
volatilization temperature there is an upper limit to the
suitable pressures as can be seen hereinbefore with respect
to Ru(acac)3 at a source temperature of 210C. The maximum
source temperature depends on how much decomposition can be
tolerated, as well as on the pressure and the complex used.
The deposition rate increases with increase in
volatilization. For example, using a Ru(acac)3 source, a
pressure of 10 2 to 10 3 torr and a substrate temperature of
7~
about 500C, a source temperature of about 140C produces
detectable vaporization, but insufficient to form a deposit.
Usinq the same pressure, substrate temperature and source,
source temperatures of about 150 to 180C give moderate de-
position rates of 1 to 2 ~m/h (micrometers average thickness ~-
per hour). The op~imum source temperature is from 200 to
210C, e.g., 200 to 205~C, which at a substrate temperature
for example of 500C can give a deposition rate of up to
15 ~m/h, e.g., up to 6 ~m/h, respectively. Preferably, the
conditions of the deposition are chosen so as to produce a
coating rate of at least 10 ~m/h. At about 215C the Ru(acac)3 ~;
shows signs of melting and of decomposing. Higher tempera-
tures can be used but there is an increasing penalty incurred
by decomposition of the source. The optimum temperature for
Ru(acacl3 is about 210C at which the rate is about. 15 ~m/h
or higher. The complex Ru(CH3.CO.CH2CO.CF3)3 is more volatile
than Ru(acac)3 and so a lower source temperature can be used,
the optimum temperature being about 130 to 150C. Source
temperatures quoted in this specification are as measured by
a thermocouple placed outside the vessel containing the
source and close to the source within the heated space.
The vapor produced by the source diffuses to the
substrate down a concentration gradient between the source
and the substrate. During diusion the vapor may come into
contact with a wall of the containing vessel, where it may
condense or even decompose. The wall is preferably maintained
at a suitable temperature so that the vapor neither condenses
nor decomposes on the wall.
The vapor of the complex should decompose on the
surface of the substrate if the ruthenium formed is to form
..~
-8-
;. ~ , , .. ,: .
~37~40 `~
part of an adherent coating. To promote adherence of the
coating, the substrate should be clean and free o~ grease.
This cleaning may be readily done with carbon tetrachloride,
for example.
The temperature of the substrate must be high
enough to be capable of decomposing the vapor o~ the complex
and thus depends on the thermal stability of the complex. ~ -
Generally speakin~, the higher the substrate temperature,
the faster is the decomposition of the complex, but there is,
however, an upper limit to the substrate temperature. This
upper l;mit arises because~ when the substrate becomes too
hot, it can decompose the vapor before the vapor reaches the
surface o~ the substrate. Ver~ little, if any, o the ru-
thenium formed in this was away from the sur~ace becomes
incorporated in an adherent coating on the substrate. Conse-
quently, the upper limit of substrate temperature is reached
when such decomposition away ~rom the substrate surface pre-
vents su~fic~ent vapor from reaching the sur~ace to form a
deposit at the desired rate. Preferably, the substrate tem-
peXature is such that decomposition away from the surface is
minimized or nil, i.e., substantially all the ruthenium in
the vapor of the ruthenium complex decomposed by the substrate
is deposited on the substrate. The suitable range o~ substrate
kemperatures depends on the complex and substrake used. For
Ru(acacl3, the preferred range is 550 to 650C, with the opti-
mum temperature be~ng about 580C. For the complex
Ru(CH3.CO.CH2CO.CF3)3, wh~ch is thermally more stable than
Ru(acac)3, a higher substrate temperature is required, the
optimum being about 700 to 750C. The suitability of a given
substrate temperature depends to some extent on the apparatus.
~"
~87~4(;~
The closer the wall of the apparatus is to the substrate,
thc cooler should be the substrate to avoid heating the wall
to a temperature high enough to decompose the complex on the
wall. For this reason, the substrate is usually suspended
in the apparatus so that it is away from the wa}ls.
The temperature of the substrate should usually be
higher than that of the wall and so the substrate should be
heated accordingly. With wall of glass or other material
not heated by radio-frequency induction and a substrate of
metal, e.g., a sintered carbide tool insert, or of other
material capable of being heated by radio-frequency induction,
a preferred method of heating the substrate is by radio-
frequency induction heating, as this does not heat the walls
substantially. The temperature of the substrate is conven-
niently measured by an infra-red thermometer.
The deposit of ruthenium produced by the decomposi-
tion of the complex is metallic in appearance and adheres to
the substrate, provided, as has been mentioned hereinbefore,
the complex is substantially pure.
The thickness of the deposit, which is usually
substantially uniform, is usually measured as an average by
a weighing method. The substrate is weighed before and aEter
coating, the difference being the weight of ruthenium de-
posited. To give the average thickness of the deposit, this
weight may then be divided by the density of ruthenium
~12.~ kilograms/cubic decimeter, kg/dm ) (gives the volume
of ruthenium) and by the area coated. The process of the
present invention may be used to produce coatings up to 10 um
average thickness, or even thicker.
The decomposition of the complex produces decom-
--10--
87~
position products derived from the or~anic part of the com- -
plex. These decomposition products contaminate the partial
vacuum but do not, in general, interfere with the deposition
although -they do raise the pressure. Pressures referred to
in this specification in the substantially static vacuum are
initial pressures, no account, generally being taken of
changes in pressure caused by the decomposition. The pumping
out of the apparatus in preparation for another deposition ~ ;~
run is generally sufficient to prevent the decomposition pro-
ducts from interfering with the deposition. If necessary,
the apparatus may be purged, for example with nitrogen, to
remove them.
Any substrate, which is solid at the temperature
used in decomposing the complex, ma~ be used, for example
glass or diamond. However, the substrate is preferabl~ metal,
cspecially a metallic face or faces adjacent to a cutting
edge, or each cutting edge, of a cutting tool. Such tools ;~
include drills, such as rock drills, cutting tips, e.g., for
cutting metals, or any other tools having one or more cutting
edges, and are hereinafter referred to as "cutting tools"
for simplicity. The cutting edge and parts of rake and flank `
faces oE a cutting tool are worlcing surfaces which are sub-
ject in use to considcrable wear, which limit~ the cutting
li~e of the tool.
It has now been found surprisingly that such cutting
tools when coated by the process of the invention show, in
use, less flank wear than tools coated with ruthenium by the
electrodeposition process referred to hereinbefore.
Because of this reduced flank wear, tools coated
by the present process are expected to show, under equivalent
~L~87~4~
working conditions, longer life than tools coated by the
electrodeposition process, as flank wear is often a cause of
failure of tools coated by electrodeposition, and, also, of
uncoated tools. Similarly, tools coated by the present pro-
cess are expected to be able to withstand, for a given life,
more stringent operating conditions than tools coated by
electrodeposition.
The cutting tool or, frequently, only its metallic
cutting part, may be made of hard metal, high speed steel or
any other suitable material. The hard metal contains a car-
bide or carbides which ma~ be an~ of those commonly used in
the production of tools, for example those hard metal grades
consisting of substantially only tungsten carbide and cobalt,
and those grades using a mixture of carbides in a cobalt `
m~ltrix, e.g., a mixture of tungsten and titanium carbides in
cob~lt, and a mixture of tungsten and titanium carbides with ~-
a mixed carbide of tantalum and niobium in cobalt.
Hard metal tools coated by the present process may
be heat treated, to cause some diffusion to occur between
the coating and the substrate. Diffusion may be obtained at
a temperature of from 1250 to 1400C, but a temperature of
Erom 1300 to 1350C is preferred as diffusion is slow below
1300C, and above 1350C some degradation of the carbide may
occur. The heat treatment is preferably carried out in
another apparatus from that used to deposit the ruthenium.
The tool life oE the coated tool is further increased by the
heat treatment, e.g., by up to 3 times.
The beneficial effect of the ruthenium coating in
electro-coated tools is more pronounced when cutting hard
materials than with softer materials, where the beneficial
~87~40
effect is less. With tools coated by the present process -?
the flank wear is reduced by a factor o~ up to about 3, or
even more, and so tool-life is increased, ~or both types of
material, although, again, the benefits are greater for
cutting harder rather than softer materials.
Substrates coated by the present process are
pre~erably substantially non-porous.
Further examples of substrates that may be coated
by the present process are those which, like cutting tools,
may be subject to wear and become heated in use. Examples
of these other substrates are wire drawing dies. powder com-
pacting or forming dies and some journal bearings.
Another possible substrate is titanium metal in
the form of an electrode. A ruthenium coated titanium elec-
trode obtained by the process of the present invention may
be used as an insoluble anode in a nickel electrowinning pro-
cess. For such a use the coating may be about 1 ~m thick
and is preferably superficially oxidized by, for example,
the anodic oxidation process described in U.S. patent No.
3,763,002.
Other uses of the ruthenium coatings are ruthenium-
coated soldering irons and ruthenium-coated electrical con-
tacts, e.g., in reed switches. The coating may also be used
decoratively, or to impart corrosion-resistance and wear-
resistance.
Once deposition of ruthenium has been completed it
is possible to remove the substrate, for example by dissolv-
ing it chemically. This method can be used to prepare
ruthenium crucibles.
The present invention is illustrated by the follow-
ing ExamplesO
~87~40
EXAMPLE_I
An apparatus that can be used, for example, on the
laboratory scale is shown in the sole Figure of the accom-
panying drawing.
Referring to the drawing, some red crystalline
Ru(acac)3, as ruthenium source 1, was placed in the closed
end 2 of a glass tube 3. Above the ruthenium source 1, a
substrate 4, which was a sintered carbide tool insert, was
suspended by a copper wire 14 from a glass support rod 5.
~he rod 5 was held in a cap 6 air-tightly fitted
in the open end of the tube 3. From the cap 6, tubing 7 led
via a turn-cock 8 to a rotary vacuum pump and a McLeod gauge
(both not shown).
The region of the tube 3 containing the ruthenium
source 1 was surrounded by a furnace 9 which contained some
glass wool 10 on which the tube 3 rested. The temperature
of the furnace and ruthenium source 1 was measured by a ther-
mocouple 11 which was connected via wires 12 to a digital
voltmeter (not shown).
The substrate 4 was heated by a heating coil 13 of
a kilowatt induction furnace (not shown). The temperature of
the substrate 4 was measured by an infra-red thermometer
(not shown) which was focused on the substrate from outside
the tube 3.
At the start of the run the furnace 9 was in a
lowered position, i.e., withdrawn from the tube 3 and below
the position illustrated in the accompanying drawing.
With the turn-cock 8 open, the apparatus was pumped
with the rotary vacuum pump down to an initial pressure of
10 2 torr, as measured by the McLeod gauge, and the turn-
~704~
cock 8 was then closed. The substrate was then heated to a
temperaturc of about 500C. The furnace 9 was heated to
200~ and then raised to surround the tube region containing
the ruthenium source 1.
A smooth adherent coating of metallic ruthenium was
formed on the substrate 4 at a rate of about 6 ~m average
thickness/h to a final average thickness of 10 ~m.
If the Ru(acac)3 had been prepared sometime ago,
e.g., several years ago, the deposit was initially black and
did not adhere to the substrate. Provided that all deposi-
tion of black deposit was over, if this black coated substrate
was replaced by another one, the deposit then obtained was
smooth, adherent and metallic.
EXAMPLE 2
This Example compares using the apparatus shown in
the accompanying drawing, the results obtained using a static
partial vacuum according to the invention, with those obtained
by using a dynamic partial vacuum or atmospheric pressure.
Using a static partial vacuum, i.e., one which was
not pumped, an initial pressure of 0.~ torr, a Ru(acac)3
source at a temperature of 150C and a substrate temperature
of about 500C produced by radio frequency induction heating,
a smooth, adherent metallic coating was produced on a sintered
carbide substrate at a rate of about 1 ~m/hour (~m/h) to a
final average thickness of 3 ~m.
In comparison, as an example of the use of a dynamic,
i.e., continuously-pumped, partial vacuum, a reaction vessel
was continuously pumped at a pressure of less than 10 3 torr,
and a Ru(acac)3 source was found to evaporate under this
pressure at temperatures above about 140C, the evaporation
87~0
rate being considerable at 160C. Despite this considerable
evaporation rate and using substrate temperatures in the range
of from 400 to 600C, it was not found possible to produce
a metallic coating on a sintered carbide substrate.
As an example of atmospheric operation, a Ru(acac)
source was vaporized at a temperature of from 190 to 200C
in a flowing hydrogen (11 millimeters per minute, ml/min)
carrier gas. The substrate (a sintered carbide tool insert)
was heated to about 500~C, and although the coating obtained
was bxight, clean and metallic, it was only about 0.3 ~m
thick after one hour. Furthermore, during this time the
source was completely reduced to metallic ruthenium, and so ;
the process was ineEficient in its use of the complex. The
substrate is, accordingly, given a quicker coating in a
static partial vacuum.
EX~MPLE 3 -
Uslng the apparatus shown in the accompanying
drawing, a Ru(acac)3 solid source at a temperature of 210C
produced, on a sintered carbide substrate at a temperature
of 580C and under an inital pressure of 10 2 torr, a ru- ~ `~
thenium coating of average thickness 5 ~m in only 20 minutes,
i.e., a coating rate of 15 ~m/h.
EX~MPLE
-
UsincJ the apparatus shown in the accompanying draw-
ing a Ru(CH3.CO.CH2CO.CF3)3 source was used at a temperature
of 130C. The initial pressure in the static vacuum was
10 1 torr and the temperature of the substrate was about 700C.
A good deposit of ruthenium with an average thickness of ;~
Q.8 ~m was produced in 20 minutes, i.e., a rate of 2.4 ~m/h.
- 16 -
~, .
.. . , :
,
~7~
EXAMPLE 5
This Example and Example 6 illustrate the reduction
in flank wear obtained on tools coated by the process of the
present invention, as compared with tools coated by electro-
deposition. The coatea tools were used to machine work-bars
of two steels, designated by British Standard Type Nos.
080 A 40 (formerly called En 8) and 835 M 30 (formerly called
En30B). Type 080 A 40 has a composition, in weight ~, of
0.4 carbon, 0.05 - 0.35 silicon, 0.8 manganese, 0.06 sulfur,
0.06 phosphorous, balance iron, and a Hardness-Vickers (Hv)
of 175. Type 835 M 30 has a composition, in weight ~, of
4.1 nickel, 1.2 chromium, 0.3 carbon, 0.1 silicon, 0.5 manga-
nese, 0.05 sulfur, 0.05 phosphorous, balance iron, and a
Hardness-Vickers of 500.
The tools used were coated as follows:
A precision ground mixed carbide tool insert of
composition WC/TiC/TaNbC/Co, grade P30, was cleaned with
carbon tetrachloride and then coated with ruthenium by the
process of the invention using the apparatus in the accom-
panying drawing to an average thickness of 2 ~m using a
Ru(acac)3 source at 200C, a substrate temperature of 600C
and a pressure of 10 2 torr~ The coated tool was heat treated
in vacuum in a graphite boat with a lid, at a temperature of
1325C for 1 hour, and allowed to cool.
For comparison, a carbide tool insert of the same
composition as used for the chemical vapor deposition was
cleaned and electroplated with gold to an average thickness
of 1 ~m using a proprietary gold cyanide electrolyte and then
electroplated with ruthenium to an average thickness of 4 ~m
using an electrolyte containing (NH4)3[Ru2NC18(H2O)
- 17
~:t87~40
~30 g/l(grams/liter)) and ammonium sulphamate (10 g/l) at
pH 1.8 at a temperature of 70C and a cathode current density
of 1 A/dm (ampere/square decimeter). The electroplated tool
was then heat treated as described for the tool coated by
chemical vapor deposition.
These two coated inserts were used to machine a
work bar of Type 835 M 30 steel and their performance was
compared with that of an uncoated tool. The machining con-
ditions were 41 surface meters/minute (mpm), 0.3 millimeters/
revolution (mm/rev) and 2.0 millimeters (mm) depth of cut.
The average life of an uncoated insert was about
8 minutes whereas the two coated inserts were still machining
after 12 minutes. However, the average flank wear after 12
minutes with the insert coated by the process of the invention
was only 0.1 mm, as compared with about 0.45 mm for the
electro-coated insert.
Other machining trials were conducted with other
inserts of the same composition and coated in the same way
but using a cutting speed of 215 mpm and a Type 080 A 40
steel work bar. Here the electro-coated and uncoated inserts
both failed after 8 minutes whereas the insert coated by the
process of the invention was still cutting after }2 minutes.
The flank wear after four minutes was about 0.65 mm on the
electro-coated insert and about 0.22 mm on the insert coated
by the process of the invention.
EXAMPLE 6
Mixed carbide tool inserts, of composition WC/TiC/
TaNbC/Co, grade P10, were coated as described in Example 5
to an average thickness of 3 ~m by the process of the inven-
tion and on another insert to an average thickness of 4 ~m
by electroplating. Machining tests were conducted on Type 080
.
- 18 -
~8'71D4~
A ~0 steel work bars under the conditions described in
Example 5 but with a cutting speed of 245 mpm.
After 3.3 minutes the insert coated by the present
process showed 0.14 mm of flank wear, whereas after only 1.8
minutes the electro-coated insert showed 0.23 mm of flank
wearO
These machining tests show clearly the improvement
in flank wear, and to some extent the improvement in tool life,
produced by coating cutting tools by the process of the pre-
sent invention.
The foregoing examples show not only the utility of
the coating process of the present invention, but, also, the
fact that the rate of deposition of ruthenium can be at least
4 ~m or 5 ~m per hour which note is highly advantageous.
Although the present invention has been described
in conjunction with preferred embodiments, it is to be under-
stood 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 appended claims.
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