Note: Descriptions are shown in the official language in which they were submitted.
1 The present invention relates -to a process o~ producing
a sintered com-pact at high temperature under high pressure.
When hotpresslng a powde,red material to produce a
sintered compact by means of hot isostatic prass or known
super-pressure and high temperature apparatus for making
a diamond, it provides little problem if the particle size
of the material is coarser than several hundred microns, bu-t
if' it is liner than several -ten microns~ particu.larly finer
than one micron, it ;s impossible to obtain a densel-,y ~,
concentrated structure if' the gas components are not
completely removed ~rom the powdered material since numerous
pores are contained in the obtained compact.
The above gas components include physically adsorbed
gas, chemically adsorbed gas and those existing in th& fo,rm
of oxides or hydroxides at the recesses or surf'aces of the
particles. Therefore, however high vacuum is applied to ;~
the powdered material at room temperature, such gas components
generate gases to cause pores in the compact by the heat
, during hot-pressing~
For example, a vacuum is applied to ~C-Co powder
mix at room temperature, and thereafter the temperature
i9 raised to abou-t l000 C, there îs generated a great
deal of gases such as H20, C02, C0 and H2.
The following is a consideration on the influence of
2 amount contained in WC-Co powder mix, the amoun-t 'being
generally said to be about 0.3 to 0.6 ,~
The specific gravit~ of WC 10 ~ Co alloy is 14.6.
Therefore, the weight of 1 cc thereof is 14.6 g. Assuming ,~
that the po-wder mix has an amount of -5 ~ ~ 2;
11~.6 x 0.005 x 1/32 x 22.4 x 103 = 51,1(cc)
The powder mix is then hot-pressed by means of hot isostatic
~s~
1 press under a pressu:re of 2000 atm at a temperature of
1400 C, and this amoun-t o:~ 51.1 cc becomes;
51.1 x 1/2000 x 1673/29~(room temperatu:re) = o. 14 tcc
~s a result, WC-10 ~ Co compac-t must contain 1~ ~ o~ pore.
Therefore 9 it is a'bsolutel-y impossible to o'btain a compact
havi.ng a density of 100 '~
In the case of super-pressure and high temperature
apparatus for making a diamond, the material to be sin-tered
is enclosed in a solid pressure medium such as pyrophyllite,
and since a tremendous pressure such as 500 to 600 ~g/mm2
is applied to -the pressure medium, the escape o~ gases is
almost impossib].e, simi]arly ln an air-tight container.
There~ore, when sintering diamond or cubic(i.e. isometric)
boron nitride, which is becoming a recent issue, there
ari.ses the same problem as WC-Co powder mix men-tioned above.
Upon sintering alumina powder, also the same problem
occurs When the powder material is subjected to gas
analysis, there is o~-ten genera-ted a gas as much as 1 ~.
According to the present inventi.on, there is proposed
a process o~ producin.g a sin-tered compact comprisirlg filling
a cup with a powdered material to be sin-tered, putting on
an opening o:~ the cup a coveri.ng member includin~ a lid and
solder so as to permit ventilation between the interior and
e~terior o.~ the cup to ~orm a cup assemblyg applying heat
as well as vacuu~ to the cup assembly to degas the powdered
material~ melting the solder by the co~tinuation o:~ heatlng
to air-tightl-y seal the cup with the lidg and hot-pressing
the cup to obtain a sintered compact.
~ccordingly, it is an object of the present invention
to provide a process o.~' producing a sintered compact making
it possible to obtain a densely concentrated structure by
,.~ . -. . ", , .. : .. .
52~
1 co~lpletely degassing a powdered materia] so a~ to eliminate
pores caused b-,y gases.
It is another ob,jec-t of the present invention to
provide an effective process ~or ob-taining with certaint~
a dense compact by air-tightly sea:Ling a cup containing
a powdered material during degassing without using any
speci~ic device.
Other objects and ~eatures Or the present invention
- will be apparent from the ~ollowing description Or the
invention with re~erence to -the accompanying drawings 7
in which:
Fig. 1 is a longi-tudinally sectioned view showing
a cup assembly contaîning a powder or green compact thereof
-to be sintered;
F'ig, 2 is the same view showlng a modi~ication o~ a
GUp a9sembly;
Fig. 3 is the sarne view of still another modirication
o~ a cup assembly; and
Figo 4 is the same view illustrating a further ~ -
modification of a cup assembly.
Throughout the drawings~ similar parts and elements
are denoted by the similar reference numerals and letters.
Re~erring now to Figs. 1 and 2, the numeral 1Q
designates a cylindrical cup, in which is contained a
powdered material A to be sintered. The material may be
powder or green compact made by cold-pressing the powder.
On an opening Or the cup 10 is put a vent member 11 made
of solder to permit the air to pass. A lid 12 is put on
said solder member 11 thereby allowing ventilation between
the interior and exterior of the cup 10.
Said vent member 11 may be a net or screen made o~
S2~'~
1 soldar wires as illustrated in ~ig. 1, or may be a corrugated ~;
plate as shown in Fig. 2. Though not shown in the drawings,
the member 11 can be a split ring made of solder wire, and
it is p-ut on the opening of the cup 10. Further the member
11 may be a powdered solder, which is coated on the opening
o~ the cup 10. There can be used an-y other solder member
which permits ventilation.
Said material A to be sintered is diamoncl~ cubic
boron nitride or their mixture. A suitable binder such as
nickel and titanium nitride can be further mixed in the
material.
If such material has a particle size o~ several microns
or finer~ or if the material is mixed with a binder such as
nickel powder, other metal powder, titanium nitride powder
and other compound powder, it can be previously cold--pressed
under a pressure ranging from several ten to several thousand
Kg/cm2 to ~orm a green compact.
There can be used any other powdered materials to be
sintered such as alumina, mix Or tungsten carbide with cobalt,
and titanium diboride.
The combination Or the solder member 11 and the cup
10 along with the lid l2 is exemplified in Table I.
TABLE I
Cup and Lid Solder Member
~'e or its alloy Gu or its alloy
Mo or its alloy Cu or its alloy
Ti or its alloy silver solder
WC Co or W-C~Co eutectic alloy
W Cu alloy ~-~
W Ni alloy
The above combination is selected in view o~ a temperature
- 5 - -~
~5;2~
1 for the comple-tion of degassing a powdered material to be
sintered, and in view Or the reactivity to the material.
Among the above, the combination of ~e or its alloy
with Cu or its alloy is the most ine~pensive and easiesk
in technical operation~
In the abova ernbodiment, the vent member 11 is
inser-ted between the cup 10 and lid 12. However, as
shown in Figs. 3 and 4) the lid 12 itself can be formed
by a porous material such as sintered mass Or iron powder ;;
to permit ventilation, and thereon i9 put a solder piece 13.
The lid may be fitted in the opening o~ the cup 10 as appears
from Fig. l~.
Thou~h not shown in the drawings, the whole cup 10
or a part thereof' can be formed by a porous material such
as sin-tered iron powder. In the case, a solder piece is
put adjacent the porous portion.
The following Table II e~empliries the combination
of the cup 10~ lid 12 and solder piece 13.
TABI.E II
Cup Lid Solder Piece
Ni sintered ~e powcler Cu alloy
Fe or its alloy sintered Fe powder Cu alloy or
Sn-Pb solder
cold-pressed WG powder cold~pressed WC powder Co-C-W or Ni
Co sintered Fe powder Cu al]oy
cold-pressed Fe powder cold-pressed Fe powder Cu
Prererably these porous materials have a porosity
Or 20 to 60 ~.
Thus constructed cup assembly is than subiected to
heat as well as vacuum so as to completely degas -the
powdered material A, and the solder member 11 or solder
piece 13 is melted at its mel-ting point by the continuation
~ 6 -
~5~2
of heating to air-tightly seal the cup 10. In the cases of
Fiys. 1 and 2, the lid 12 is brazed to the cup 10 by the solder
member 11. In the cases of Figs. 3 and 4, the melted solder
piece 13 permeates into the porous lid 12, which is in turn
brazed to the cupr thereby air tightly sealing the cup 10.
Preferable hea-ting temperature is at least 500C or
h:i~her. If the material to be sintered is diamond or cubic
boron nitride which is thermodynamically unstable under ordinary
pressure and transEorms to graphite or hexagonal boron nitride,
10 respectively, when exposed to high temperature, a lower tem-
perature than 1300 C is preferable.
The vacuum is at least 10 2 mmHy or higher, and can
be applied to a limited part having ventilation, for example,
a-t the opening of the cup 10 through a pipe connected thereto.
The obtained cup is compressible under high pressure
at high temperature while main-taining the air-tight seal.
The cup is then hot-pressed by hot isostatic press
or super-pressure and hlgh temp~rature apparatus for making
a diamond so as to obtain a sintered compact. If the material
~O to be sintered is diamond or high pressure form o~ boron
nitride, it is preferable to hot-press under a pressure o~ at
least 20 Kb or more at a temperature higher than 1000C for
several minutes to several hours. As for the other materials
such as alumina, titanium diboride and mix of -tungsten
carbide with cobalt~ the pressure is several ten to several
thousand Kg/cm2 and the temperature is 1200 to 2000C
The cup thus compressed by the hot-pressing includes
a sintered compact and a shell enclosing it. The compact
is obtained by removing the shell.
3~ If a diamond compact obtained has its matrix mainly
composed of copper, it is non-magnetic and useful as an-ti-
."..,
' . ~ . . ..
.. ,., ,, .- . .
1 abrasive parts ~nd el0ments in an electronic computer and
household electric machines such as tape recorder. l~oreover
it has a property higher in heat conductivity. However, it
may generall~ be lower in toughness as compar~d to one with
a matrix of iron ~roup element. Especially, when used as
a cutting tip, the strength is not sufficient at high
temperature since the melting point O:e the copper is lower
than that of iron group element.
In contras-t, a diamond compact with its rnatrix mainly
composed of nickel or its alloy has properties substan-tially
opposite to the above. '~
As a result of experimen-ts, the former is obtained
by the use of iron or cobalt cup in combination with a
solder of copper or its alloy, while the latter can be
obtained b~ the use of a cup of nickel or its alloy in
combination with a solder of copper or its allo~
As mentioned before, the hot-pressed cup includes
a sintered compact enclosed by a shell of compressed cup.
In order to obtain a compact, the~shell should be removed.
However~ this is very difficult, particularly in the case
of small compact such as diamorld, since the shell is
generally in ti~ght engagement wit'h the compact. However7
with a cup of iron or its alloy, it has been found that
the shell can be readily taken off~
U-tilizing the a'bove phenomenon, when putting~ for
exarnple, a conical block of iron on the center of the
bottom of iron cup, a diamond compact having a conical
recess at the center thereof can be obtained with ease
since the conical block is readily taken off. Therefore,
there can be provided a diamond compact having a suitable
shape similar to a :einished product such as wire drawing
~ 8 --
"
2~.~
1 die. Of course, an iron rod and the like can he put in the
c~p. Considering the di-fficulty of shaping a dlamond compact,
this is very useEul.
In order to more clearly illustrate the present
invention, re~erence is now to be made to -the following
Examples, which are only for description rather than limitation
to the invention.
EXAMPLE 1
~ cup o~ mild steel was vibrated while it was fillecl
with diamond powder. The cup had an outer diameter of 14 mm,
inner diameter of 7 mm and height of 19 mm and the diamond
powder had an average particle size of 5 micron. The amount of
diamond was 1.6 g~
On an opening o~ the cup was put, as a solder, a split
ring of pure copper wire with a diameter of 1~5 mm, and thereon
was put a lid of mild steel having a diameter of 14 mm and
thickness of 3 mm.
Thus assembled cup was put in a vacuum furnace, heated
to 1150C by a rising rate of 500C per hour in a vacuum of
2~ 10 4 mmHg, held for 10 minutes, and cooled. The cup taken out
of the furnace had its opening air--tigh-tly sealed by the melted
copper.
This was hot~pressed by a super-pressure and high
temperature apparatus for making a diamond. Initially, the
cup was put in the apparatus, given a pressure of 55 Rb, then
heated to 1450C, held at the temperature fox 5 minutes, and
cooled.
Tha steel cup was then ground and removed to take out ~;
a diamond compact, the specific gravity of which was 4Ø The
compact was densely sintered without any pore.
The compact was further ground by a diamond wheel
dresser. As a result of examination by microscope, the
_ 9 _
5~
l structure was such that -the grains of diamond powder were
bonded together, and grain boundaries therebetween were
f`i]led with rnatal. By the analysis of X-ray microanalyzerJ
i-t was revealed that this bonding metal consis-ted of copper
an(l about 15 '~ Or iron.
3efore hot-pressing, the air-tightly sealed cup was
cut -to find that the inner periphery thereof was ~ilmed
with copper for 'brazing the lid to the cup, the thickness
of copper filrn being a'bout 0.15 mm. The coppar and steel
of the cup were considered to permeate into the grain
boundaries of diamond powder to form a metal matrix.
EXAMPLE 2
Cubic boron nitride powder having average particle
size of' 4 micron and titanium nitride powder having average
particle size of 1 micron were mixed in a volume ratio of
3 : 2, and filled in a cup of molybdenum having an outer
diameter of 14 mm, inner diameter of 10 mm and height of
6 mm.
On an opening of the cup was put~ as a solder, a
screen of 32 mesh(hereinafter re~erred -to as U.S. Standard)
made of bronze, the screen having a diameter of 1 Ll. InmJ on
which was put a lid of moly'bdenum with a diameter o~ 14 mm
and thickness of 3 mm.
Thus assembled cup was put in a vacuum furnace in
the same manner as Example 1, heated at 1100 G in a vacuum
of 10-l~ mmHg, and cooled. The lid and cup taken ou-t of the
furnace were air-ti.ghtly brazed together by the melted bronze.
This cup was hot-pressed by the super pressure
apparatus in the same manner as Example 1. The obtained
compact exhibited Vickers hardness of 3600, and was
densely sinteredO
-- 10 --
5~
1 EXAMPLE 3
Instead of mol~bdenum cup of E'xample 2, there was
prepared a Cllp of pure titanium having the same dimensions.
Then, a diamond powder having average particle size
Or 5 micron was mixed with 19 weight ~ of electrolytic
copper powder and 3.5 weight i~ of nickel powder~ respectively
having a particle size Or -325 mesh. Ths m;x was ball-milled
in a stainless steel pot b~ using cemented carbide balls~ and
filled in said titanium cup~
On an opening O:e the cup was pu-t a split ring o~ silver
solder(corresponding to JIS - Japanese Industrial S-tandard~
BAg-2, melting point 700 C), on which was laid a lid of
titanium.
Similarly to Example 1, the cup assembl~ was put in
a vacuum furnace9 heated to 900 C in a vacuum of 10~L~r~lHg,
and cooled. The cup taken out of the furnace was air-
tightly sealed with the melted silver solder.
'rhe cup was pressed under a pressure of 60 ~b by
means of -the same super-pressure apparatus as Example 1,
and then the temperature was raised to 1500 C. The Cllp
was held at the temperature f'or 5 minutes to be hot-pressed.
The CUp was takerl out, and ground to obtain a densely
sin-tered diamond compact. This was cu-t by a diamond cutter
and a piece was 'orazed to a tool shank b~ using a silver
solder to f'orm a cutt;ng tool.
A cemented carbide rod of WC-l2 ~ Co with Vickers
hardness of 1300 was cut b~ said cutting tool) resulting
in a sat;sfactor~ performance.
EXAMPLE 4
h powdered -titani-um diboride(TiB2) having average
particle size of' 3 micron was filled in a titanium cup
- 11 - : '"
. " ~:
9S2~2
1 having an outer diameter of 1L~r~rn, inner diameter Or 1 0 mm
and height of 6 mm.
A powder of nickel solder(melting point: 102L~ C,
particle size: --120 nnesh, +200 mesh) consisting of
Ni-ll.5 Si-2.9 ~ was added with~ as a ~inding agent,
ethyl cellulose solved in toluene, and a~itated. This
was coated on an opening ol' the cup in a thic1rness of
about 3 rnm, on which was put a tantalum lid having a
thickness of 2 mm.
In the same manner as Example 1, the cup asse~'bl-g
was put in a vacuu~ furnace, hea-ted to 1100 C in a vacuum
of 10-1~ mmHg, and eooled.
As a result of examination on the cup taken Ollt of'
the furnace, the tantalum lid was brazed to the cup wi-thout
an~ gap.
The cup was put in a super-pressure apparatus 3
pressed to 50 Kb, and heated at 1800 C for 10 mimltes
to be hot-pressed.
The obtained eompaet had a density as nnueh as 99 ,~
of ideal density. As a result o~ examina-tion on the
structure after polishin~ the compact by diamond paste,
lt was assured tha-t the eon1pact was densel-y sintered
without any pore.
EXAMPLE 5
Diamond powder of average particle size of 5 micron
added wi-th 20 weight ~ of carbonyl niekel powder was
ball-milled and mixed for 24 hours în a sta;nless steel
pot by using cemented earbide balls of WC-10 -~ Co. The
powder mix was added with 2 '~ of camphor as a lubricant,
and cold-pressed undsr a pressure of 1 t/cm2 to f'orm a
pellet having a diarneter of 5 mrn and height of 5 rnrn.
- 12 -
2~
1In a cu-p of` nickel having an inner diame-ter o~ 5 mm,
outer diameter of 7 mm was put the pellet, on wh;.ch was
put a porous lid having a dia-rneter of 5 mm made of sintered
iron powder with a particle slze from 120 mesh to 100 mesh,
on which was laid a copper allo~ con-taining 5 '~ of iron and
5 ~ of manganese, th.e allo.y havin~ a diam~ter of 2.5 mm ~ -
and height of 2 mm.
The cup as~embly was put in a vacuum furnace wi-th ::
a diffusion pump, heated to 1150 C by a rising rate of
500 C per hour, and cooled~ Taking the cup out of the
furnace J the melted copper alloy completel-y permeated i.nto
th.e porous lid~ which was in turn brazed to the nickel cup.
This was hot-pressed by means of a super-pressllre
and high tempe:rature apparatus for making a diamond.
Graphite was used as a heating element, and salt was ~ -.
interposed between the graphi-te and nickel cup. The cup
was hot-pressed under a pressure of 60 Kb at a temperature :~:
of 1600 C for 10 minutes to obtain a diamond compact
having Vickers hardness of 6500. The densi-ty as well as
hardness was much superior to that obtained. by a conventional
process without the degassing treatment as in the preseni;
invention.
EXAMPLE 6
Super-puritly alumina powder having average particle
size of 0.4 micron was added wi-th o.5 ~ of magnesia powder,
and subjected to a wet ball-milling in water for 100 hours
in a po-t having super-purit-y alumina lining by using
super-purity alumina balls. The powder wad dried, added
with 3 % of camphor, and cold-pressed under a pressure of
1 t~cm to form a green compact having a diameter of 60 mm
and height of 50 mm.
- 13 -
1~¢~
1 i On the other hand, there was prepared a cup having
an inner diame-ter o~ 60 mm, depth o~ 70 mm and thickness
of 1 mm by cutting a low carbon steel block. In the cup
was inserted said green compact~ on which wa~-pu-t a porous
lid having a diameter o~ 60 mm and thickness o~ 1 mm made
of sintered iron powder with a particle size ~rom 100 mesh
to 50 mesh, on which was laid a copper alloy containing
5 ~ of iron and 5 ~ of manganese.
The cup assembly was put in a vacuum furnace with
a diffusion pump, and heated to 1150 C by a rising rate
of 200 C per hour.
Taking the cup out of the furnace, the copper alloy
co~pletely permeated in-to the porous iron lid and sealed
the opening o~ the cup. Then a disc of low carbon steel
having a diameter of ~0 mm and thickness of 1 mm wa3
brazed to the opening of the cup 90 that the whole periphery
o~ the cup was surrounded by the low carbon steel.
This was hot-pressed in an atmosphere of argon gas
` under a pressure of 2000 atm at a temperature of 1400 C
~or one hour by means o~ hot isostatic press.
The metal surrounding the cup taken out of the press
was removed by using HN03 to obtain an aIumina compact.
The surface thereof was ground o~ in a thickness o~ several
mm to obtain a compact as dense as 99 ~ o~ ideal density ~-
(P = 3.99 g/cc).
As a result of examination on crystal particles by
electron microscope, they were about o.8 micron much finer
than those obtained by any other conventional processes.
EXAMPLE 7
3o A cup was formed by a cylindrical member and a
bot-tom lid ~itted therein, both being made by cold pressing
- 14 -
., ., "., ~, " .", , ~ . .
\
;2~2
1 WC powder with average particle slze of' 4 micron. The Cllp
had a -thickness of 2 mm, inner diameter of 5 mm and inner
depth of 2 mm. Also a top lid having a thiclmess of 10 mm
was prepared by the same material.
In the cup was inserted a green compact of powder
mix comprising cubic boron nitride and ~0 ~ of -titani~n
ni-tride J on which was put the top lid7 on which was laid
a mass of cold~pressed powder rni~ consisting of Co-C-W
so as to form an eutectic alloy~
The cup assemhly was subjected to the same degassing
treatment as Example 5 in a vacuum furnace, except that ;
the highest temperature was 1350 c. After grinding off
the surface of the Cllp taken out of the furnace so as to
eliminate roughness on the surface~ the cup was subjected
to the hot-pressirlg in the ~ame manner as F~ample 5 to
obtain a sintered body having a diameter of about 10 mm
and thickness of about 6 mm. This was ground to remove
WC-Co a]loy at the side face and upper face to obtain a
cubic boron nitride compact hav:;ng a eemen-ted carbide as
a substrate. This shape was very useful as a tip of a
cutting tool.
E~AMPLE 8
Instead of nickel cup of Example 5, a cup was made
from tungsten powder having particle size of 10 micron,
and ins-tead of copper alloy of Example 5, nickel was used.
The highest temperature in the vacuum ~urnace was
1 500 c.
Similarly, a compact sufficierltl~ sintered was obtained.
EXAMPLE 9
A cup having an inner diameter of 5 mm, outer diameter
of 8 mm and depth of 10 mm was formed by eutting carbon
- 15 ~
~s~
1 steel. A dlamond powder having particle size finer -than
400 mesh was ~illed in the CUp in a height of 8 mrrlJ while
giving vibra-tion, and thereon was pu-t a porous lid made
b~J sintering iron powder o~ -~140 mesh to -100 mesh, on
which was further laid a piece of copper allog incl-uding
5 ~ o~ iron and 5 '~ of manganese.
The cup assembl-y was put in a vacuum furnace with a
diffusion pump, and heated -to 11~0 C by a rising rate of
500 C per hour.
Taking the cup out o~ the furnace, the copper alloy
permeated into the porous iron lid, which was in turn
brazed to the steel cup.
This was hot-pressed b;q means o~ a super-pressure
and high temperature apparatus for making a diamond. As
a hea-ting e:Lement was used a graphlte tube, and salt was
interposed between the tube and cup. Further as a pressure
mediu-m was used a pyrophyllite.
Initially, the pressure was raised -to 60 Kb, and
then the -temperature to 1600 C by gradually supplying
electrical curren-t. Therearter the pressure as well as
temperature was lowered. The obtaizled compact was such
that the diamond par-ticles were completely impregna-l;ed
with copper and presented good appearance. Vickers
hardness thereof was about 6000~
EXAMPLE 10
Instead of -the steel GUp 0.~ Example 9, 18~8 stainless
steel, nickel or cobalt was used, respectively. Each cup
was subjected to the same treatment as Example 9, with the
same result as Example 9.
EX~MPLE 11
Atomized iron powder was cold-pressed to form a cup
- 16 -
" :" ~
z
1 having a porosit-y Oe 37 ~. The dimensions of the cup were
the same as Example ~. After rilling diamond powder of
-l~00 mesh in -the cup, a lid formed with the same material
as the cup was ~itted in the cup, and thereon were accumulated
copper wires Cllt into pieces, the wires having a diameter of
1 mm.
The cup assembly was put in the same vacuum furnace
as Example 9, and heated, while supplying hydrogen gas for
the reduction of oxides on the surfaces o~ iron and diamond ~;
powders till the temperature was raised to 9~0 C, the
pressure o~ hydrogen gas in the ~'urnace being held at
300 mmHg. After raising the temperature to 950 C, the
furnace was held under a pressure o~ lO l~ to 10 5 mmHg
by the use of di~fusion pump.
The cup was then ho-t-pressed by a super-pressure
a-pparatus in the same manner as Example 9 to obtain a
densely sintered compact~
EXAMPLE 12
A cup having an inner diameter Oe 5 mm, outer
diameter Oe 8 mm and dep-th of 10 mm was formed b;y cutting
a nickel rod. In the cup was filled a diamond powder o~
-400 mesh in a height of 8 mm, and thereon was laid a
porous lid having a diameter o~ 5 mm and thlckness o~ 1 mm
made b;y sintering iron powder of ~140 mesh and -100 mesh,
on which was further put a copper piece.
The cup assembly was put in a vacuum eurnace wlth a
diffusion pump, and heated to 1150 C b-y a rising rate O.e
500 C per hour. Thereafter 7 this was hot-pressed by means
of super-pressure and high temperature apparatus for making
a diamond. As a heating element was used a graphite tube,
and as an electrical insulation material wa~ put a salt
_ ~7 _
~0~ 2
1 between the cup and tube. L~urther as a pressure medium
was use~ a pyrophyllite. Initially, the pressure was
raised -to 60 Kb, and then the temperature to 1500 C by
gradually suppl~ing electrical current~ The cup was held
at the temperature for 5 minutes.
The 0'3 tained compac-t was crushed by compression and
examined by a mlcro~cope to find no pore at the broken face.
As a result of analysis b~ an X-rag microanalyzer, solely
nickel was observed.
EXAMPLE 13
A diamond powder of +300 mesh and -200 rnesh was
used in place o-~ the powder Or Example 12. F'urther instead
o~ the solder piece of Example 12, a solder piece o~
Cu-40 ~ Ni alloy was used.
The cup assembly was treated in vacuum in the same
manner as Fxample 12 except that the highest temperature
was 1300 C.
The obtained compact had a matrix mainly composed
of nickel arld was densely sintered.
EXA~PLE 1L~
There were used diamond powder having particle size
ranging from 2 to 3 micron and a solder piece of Cu-20 '~ Mn
alloy, in places of the powder and solder piece of Example 12.
The cup assembly was treated in vacuum in the same
manner as F~ample 12, excep-t that the highe3t temperature
was 950 C.
The obtained compact had a ma-trix mainly composecl
o~ n;ckel, and was densely sîntered.
EXAMPLE 15
3 In Example 12, thc ho-t-pressing was performed at
a temperature Or 1400 C, 1500 C ancl 1600 C, respectively.
The compact obtained at 1400 C had a specific gravity of
1 3.86. However~ as -the -temperature rose, the gravity increased
linearlq, and at 1600 C it was L~00. Also the nickel amoun-t
in the matrix increased as the -temperature rose.
EXAMPLE 16
Instead of the porous lid o.f Example 12, a porous lid
made by sintering Co powder was used, the cup having -the
same dimension~. In the same manner as Example 12, there
was obtained a sintered compact, which exhibited good
result similar to that of Example l2.
As described hereinbefore in detail$ according to
the present invention, a sintered compact having no pore
can be efficiently and sure].y obtained since a powdered
material to be sintered is completely degassed by the
application of heat as well as vacuum to a cup filled with
the material and at the same time a solder put on the
opening of the Cllp iS melted by said heat so as to air~
tightl.~J seal the Cllp, which is compressible under high
pressure at high temperature during hot-pressing while
maintaining the air tight seal.
19 -
.~,,. : :
,, - ~. ~ - ~ ,
