U.S. patent application number 10/678204 was filed with the patent office on 2005-04-07 for cemented carbide blank suitable for electric discharge machining and cemented carbide body made by electric discharge machining.
Invention is credited to Banerjee, Debangshu.
Application Number | 20050072269 10/678204 |
Document ID | / |
Family ID | 34393878 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050072269 |
Kind Code |
A1 |
Banerjee, Debangshu |
April 7, 2005 |
Cemented carbide blank suitable for electric discharge machining
and cemented carbide body made by electric discharge machining
Abstract
A cemented carbide blank suitable for fabrication by electric
discharge machining that includes a carbide phase that includes
tungsten carbide (and optionally vanadium carbide) present in an
amount equal to between about 77.7 weight percent and about 93.6
weight percent of the cemented carbide blank. The cemented carbide
blank further includes chromium present in an amount equal to
between about 0.3 weight percent and about 1.5 weight percent of
the cemented carbide blank, cobalt present in an amount equal to
between about 8 weight percent and about 17 weight percent of the
cemented carbide blank, nickel optionally present in an amount
equal to 0 weight percent up to about 5 weight percent of the
cemented carbide blank, and molybdenum present in an amount equal
to between about 0.1 weight percent and about 1.0 weight percent of
the cemented carbide blank. The cemented carbide blank having a
magnetic saturation as measured according to ASTM B886-03 ranging
between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and
about 182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
Inventors: |
Banerjee, Debangshu;
(Fayetteville, AR) |
Correspondence
Address: |
Mr. Kevin P. Weldon
Kennametal Inc.
P.O. Box 231
Latrobe
PA
15650
US
|
Family ID: |
34393878 |
Appl. No.: |
10/678204 |
Filed: |
October 3, 2003 |
Current U.S.
Class: |
75/240 |
Current CPC
Class: |
C22C 29/08 20130101;
C23C 30/005 20130101 |
Class at
Publication: |
075/240 |
International
Class: |
C22C 029/08 |
Claims
What is claimed is:
1. A cemented carbide blank suitable for fabrication by electric
discharge machining, the cemented carbide blank comprising:
tungsten carbide present in an amount equal to between about 80
weight percent and about 90.9 weight percent of the cemented
carbide blank; chromium present in an amount equal to between about
0.3 weight percent and about 1.5 weight percent of the cemented
carbide blank; cobalt present in an amount equal to between about 8
weight percent and about 14 weight percent of the cemented carbide
blank; nickel present in an amount equal to between about 0.7
weight percent and about 1.3 weight percent of the cemented carbide
blank; and molybdenum present in an amount equal to between about
0.1 weight percent and about 0.3 weight percent of the cemented
carbide blank; and the cemented carbide blank having a magnetic
saturation as measured according to ASTM B886-03 ranging between
about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about
171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
2. The cemented carbide blank of claim 1 comprising: tungsten
carbide present in an amount equal to between about 86 weight
percent and about 88 weight percent of the cemented carbide blank;
the chromium present in an amount equal to between about 0.6 weight
percent and about 1.2 weight percent of the cemented carbide blank,
the cobalt present in an amount equal to between about 10 weight
percent and about 12 weight percent of the cemented carbide blank,
and the nickel present in an amount equal to between about 0.9
weight percent and about 1.1 weight percent of the cemented carbide
blank.
3. The cemented carbide blank of claim 1 wherein the chromium
comprises between about 1.9 weight percent and about 14 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 4.3 weight percent
and about 14.4 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 0.6 weight percent and about 3.3 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
4. The cemented carbide blank of claim 1 wherein the chromium
comprises between about 4.3 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 6.4 weight percent
and about 9.2 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 0.6 weight percent and about 3.3 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
5. The cemented carbide blank of claim 1 wherein the hardness as
measured according to ASTM B294-92(2000) ranges between about 88
HRA and about 92 HRA.
6. The cemented carbide blank of claim 1 wherein the porosity as
measured according to ASTM B276-91(2000) is better than A06 B02
C00.
7. The cemented carbide blank of claim 1 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) ranges
between about 3300 MPa and about 3700 MPa.
8. The cemented carbide blank of claim 1 wherein the density as
measured according to ASTM B311-93(2000) ranges between about 14.0
and about 14.4 grams per cubic centimeter.
9. The cemented carbide blank of claim 1 wherein the coercive force
(H.sub.C) measured B887-03 ranges between about 110 oersteds and
about 170 oersteds.
10. The cemented carbide blank of claim 1 wherein the magnetic
saturation as measured according to ASTM B886-03 ranges between
about to 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
161.times.10.sup.-6 T m.sup.3/kilogram cobalt.
11. The cemented carbide blank of claim 1 wherein the cemented
carbide blank has an absence of eta phase therein.
12. A cemented carbide body made by electric discharge machining,
the cemented carbide body comprising: a body presenting a selected
shape, and the body comprising: tungsten carbide present in an
amount equal to between about 80 weight percent and about 90.9
weight percent of the cemented carbide body; chromium present in an
amount equal to between about 0.3 weight percent and about 1.5
weight percent of the cemented carbide body; cobalt present in an
amount equal to between about 8 weight percent and about 14 weight
percent of the cemented carbide body; nickel present in an amount
equal to between about 0.7 weight percent and about 1.3 weight
percent of the cemented carbide body; and molybdenum present in an
amount equal to between about 0.1 weight percent and about 0.3
weight percent of the cemented carbide body; the cemented carbide
body having a magnetic saturation as measured according to ASTM
B886-03 ranging between about 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about 171.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
13. The cemented carbide body of claim 12 wherein the cemented
carbide body presents one or more surfaces wherein each one of the
surfaces is essentially free of defects caused by the electric
discharge machining.
14. The cemented carbide body of claim 12 comprising the tungsten
carbide present in an amount equal to between about 86 weight
percent and about 88 weight percent of the cemented carbide blank,
the chromium present in an amount equal to between about 0.6 weight
percent and about 1.2 weight percent of the cemented carbide blank,
the cobalt present in an amount equal to between about 10 weight
percent and about 12 weight percent of the cemented carbide blank,
and the nickel present in an amount equal to between about 0.9
weight percent and about 1.1 weight percent of the cemented carbide
blank.
15. The cemented carbide body of claim 12 wherein the chromium
comprises between about 1.9 weight percent and about 14 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 4.3 weight percent
and about 14.4 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 0.6 weight percent and about 3.3 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
16. The cemented carbide body of claim 12 wherein the chromium
comprises between about 4.3 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 6.4 weight percent
and about 9.2 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 0.6 weight percent and about 3.3 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
17. The cemented carbide body of claim 12 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 88
HRA and about 92 HRA.
18. The cemented carbide body of claim 12 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) ranges
between about 3300 MPa and about 3700 MPa.
19. A cemented carbide blank suitable for fabrication by electric
discharge machining, the cemented carbide blank comprising: a
carbide phase present in an amount equal to between about 88.5
weight percent and about 93.6 weight percent of the cemented
carbide blank wherein the carbide phase includes tungsten and
vanadium and carbon; chromium present in an amount equal to between
about 0.3 weight percent and about 0.9 weight percent of the
cemented carbide blank; cobalt present in an amount equal to
between about 6 weight percent and about 10 weight percent of the
cemented carbide blank; and molybdenum present in an amount equal
to between about 0.1 weight percent and about 0.6 weight percent of
the cemented carbide blank; and the cemented carbide blank having a
magnetic saturation as measured according to ASTM B886-03 ranging
between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and
about 171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
20. The cemented carbide blank of claim 19 wherein the chromium
comprises between about 3 weight percent and about 15.8 weight
percent of the sum of the cobalt and chromium and molybdenum, and
the molybdenum comprises between about 1 weight percent and about
10.5 weight percent of the sum of the cobalt and chromium and
molybdenum.
21. The cemented carbide blank of claim 19 wherein the chromium
comprises between about 3 weight percent and about 8 weight percent
of the sum of the cobalt and chromium and molybdenum, and the
molybdenum comprises between about 1 weight percent and about 5
weight percent of the sum of the cobalt and chromium and
molybdenum.
22. The cemented carbide blank of claim 19 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 91
HRA and about 94 HRA.
23. The cemented carbide blank of claim 19 wherein the porosity as
measured according to ASTM B276-91(2000) is better than A06 B02
C00.
24. The cemented carbide blank of claim 19 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) ranges
between about 3300 MPa and about 3700 MPa.
25. The cemented carbide blank of claim 19 wherein the density as
measured according to ASTM B311-93(2000) ranges between about 14.3
and about 15.0 grams per cubic centimeter.
26. The cemented carbide blank of claim 19 wherein the coercive
force (H.sub.C) measured B887-03 ranges between about 260 oersteds
and about 310 oersteds.
27. The cemented carbide blank of claim 19 wherein the magnetic
saturation as measured according to ASTM B886-03 ranges between
about to 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
160.8.times.10.sup.-6 T m.sup.3/kilogram cobalt.
28. The cemented carbide blank of claim 19 wherein the cemented
carbide blank has an absence of eta phase therein.
29. A cemented carbide body made by electric discharge machining,
the cemented carbide body comprising: a body presenting a selected
shape, and the body comprising: a carbide phase present in an
amount equal to between about 88.5 weight percent and about 93.6
weight percent of the cemented carbide body wherein the carbide
phase includes tungsten and vanadium and carbon; chromium present
in an amount equal to between about 0.3 weight percent and about
0.9 weight percent of the cemented carbide body; cobalt present in
an amount equal to between about 6 weight percent and about 10
weight percent of the cemented carbide body; molybdenum present in
an amount equal to between about 0.1 weight percent and about 0.3
weight percent of the cemented carbide blank; the cemented carbide
body having a magnetic saturation as measured according to ASTM
B886-03 ranging between about 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about 171.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
30. The cemented carbide body of claim 29 wherein the cemented
carbide body presents one or more surfaces wherein each one of the
surfaces is essentially free of defects caused by the electric
discharge machining.
31 The cemented carbide body of claim 29 wherein the chromium
comprises between about 3 weight percent and about 8 weight percent
of the sum of the cobalt and chromium and molybdenum, and the
molybdenum comprises between about 1 weight percent and about 5
weight percent of the sum of the cobalt and chromium and
molybdenum.
32. The cemented carbide body of claim 29 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 91
HRA and about 94 HRA.
33. The cemented carbide body of claim 29 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) ranges
between about 3300 MPa and about 3700 MPa.
34. A cemented carbide blank suitable for fabrication by electric
discharge machining, the cemented carbide blank comprising:
tungsten carbide present in an amount equal to between about 77.7
weight percent and about 87.9 weight percent of the cemented
carbide blank; chromium present in an amount equal to between about
0.4 weight percent and about 1.3 weight percent of the cemented
carbide blank; cobalt present in an amount equal to between about
9.5 weight percent and about 15 weight percent of the cemented
carbide blank; nickel present in an amount equal to between about 2
weight percent and about 5 weight percent of the cemented carbide
blank; and molybdenum present in an amount equal to between about
0.2 weight percent and about 1.0 weight percent of the cemented
carbide blank; and the cemented carbide blank having a magnetic
saturation as measured according to ASTM B886-03 ranging between
about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about
182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
35. The cemented carbide blank of claim 34 wherein the chromium
comprises between about 2 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 10 weight percent
and about 33 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 1 weight percent and about 7.8 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
36. The cemented carbide blank of claim 34 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 87
HRA and about 91 HRA.
37. The cemented carbide blank of claim 34 wherein the porosity as
measured according to ASTM B276-91(2000) is better than A06 B02
C00.
38. The cemented carbide blank of claim 34 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) is at
least about 3200 MPa.
39. The cemented carbide blank of claim 34 wherein the density as
measured according to ASTM B311-93(2000) ranges between about 13.5
and about 15.0 grams per cubic centimeter.
40. The cemented carbide blank of claim 34 wherein the coercive
force (H.sub.C) measured B887-03 ranges between about 80 oersteds
and about 150 oersteds.
41. The cemented carbide blank of claim 34 wherein the magnetic
saturation as measured according to ASTM B8860-03 ranges between
about to 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
42. The cemented carbide blank of claim 34 wherein the cemented
carbide blank has an absence of eta phase therein.
43. A cemented carbide body made by electric discharge machining,
the cemented carbide body comprising: a body presenting a selected
shape, and the body comprising: tungsten carbide present in an
amount equal to between about 77.7 weight percent and about 87.9
weight percent of the cemented carbide body; and chromium present
in an amount equal to between about 0.4 weight percent and about
1.3 weight percent of the cemented carbide body; cobalt present in
an amount equal to between about 9.5 weight percent and about 15
weight percent of the cemented carbide body; nickel present in an
amount equal to between about 2 weight percent and about 5 weight
percent of the cemented carbide body; and molybdenum present in an
amount equal to between about 0.2 weight percent and about 1.0
weight percent of the cemented carbide body; the cemented carbide
body having a magnetic saturation as measured according to ASTM
B886-03 ranging between about 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
44. The cemented carbide body of claim 43 wherein the cemented
carbide body presents one or more surfaces wherein each one of the
surfaces is essentially free of defects caused by the electric
discharge machining.
45. The cemented carbide body of claim 43 wherein the chromium
comprises between about 2 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, and the nickel comprises between about 10 weight
percent and about 33 weight percent of the sum of the cobalt and
chromium and nickel and molybdenum, and the molybdenum comprises
between about 1 weight percent and about 7.8 weight percent of the
sum of the cobalt and chromium and nickel and molybdenum.
46. The cemented carbide body of claim 43 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 87
HRA and about 91 HRA.
47. The cemented carbide body of claim 43 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) is at
least about 3200 MPa.
48. A cemented carbide blank suitable for fabrication by electric
discharge machining, the cemented carbide blank comprising:
tungsten carbide present in an amount equal to between about 81.1
weight percent and about 86.4 weight percent of the cemented
carbide blank; chromium present in an amount equal to between about
0.4 weight percent and about 1.3 weight percent of the cemented
carbide blank; cobalt present in an amount equal to between about
13 weight percent and about 17 weight percent of the cemented
carbide blank; and molybdenum present in an amount equal to between
about 0.2 weight percent and about 0.6 weight percent of the
cemented carbide blank; and the cemented carbide blank having a
magnetic saturation as measured according to ASTM B886-03 ranging
between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and
about 182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
49. The cemented carbide blank of claim 48 wherein the chromium
comprises between about 2 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and molybdenum, and
the molybdenum comprises between about 1 weight percent and about
4.4 weight percent of the sum of the cobalt and chromium and
molybdenum.
50. The cemented carbide blank of claim 48 wherein the hardness as
measured according to ASTM B294-92(2001) ranges between about 88
HRA and about 90 HRA.
51. The cemented carbide blank of claim 48 wherein the porosity as
measured according to ASTM B276-91(2000) is better than or equal to
A04 B00 C00.
52. The cemented carbide blank of claim 48 wherein the transverse
rupture strength as measured according to ASTM B406-96(2000) ranges
between about 3800 MPa and about 4200 MPa.
53. The cemented carbide blank of claim 48 wherein the density as
measured according to ASTM B311-93(2000) ranges between about 13.7
and about 14.3 grams per cubic centimeter.
54. The cemented carbide blank of claim 48 wherein the coercive
force (H.sub.C) measured B887-03 ranges between about 180 oersteds
and about 230 oersteds.
55. The cemented carbide blank of claim 48 wherein the cemented
carbide blank has an absence of eta phase therein.
56. A cemented carbide body made by electric discharge machining,
the cemented carbide body comprising: a body presenting a selected
shape, and the body comprising: tungsten carbide present in an
amount equal to between about 81.1 weight percent and about 86.4
weight percent of the cemented carbide blank; chromium present in
an amount equal to between about 0.4 weight percent and about 1.3
weight percent of the cemented carbide blank; cobalt present in an
amount equal to between about 13 weight percent and about 17 weight
percent of the cemented carbide blank; and molybdenum present in an
amount equal to between about 0.2 weight percent and about 0.6
weight percent of the cemented carbide blank; and the cemented
carbide blank having a magnetic saturation as measured according to
ASTM B886-03 ranging between about 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
57. The cemented carbide body of claim 56 wherein the cemented
carbide body presents one or more surfaces wherein each one of the
surfaces is essentially free of defects caused by the electric
discharge machining.
58 The cemented carbide body of claim 56 wherein the chromium
comprises between about 2 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and molybdenum, and
the molybdenum comprises between about 1 weight percent and about
4.4 weight percent of the sum of the cobalt and chromium and
molybdenum.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention pertains to a cemented carbide blank
that is suitable for electric discharge machining (EDM), as well as
a cemented carbide body made by an EDM process from the cemented
carbide blank. More specifically, the present invention pertains to
a cemented tungsten carbide blank, as well as a cemented tungsten
carbide body made by an EDM process from the cemented tungsten
carbide blank, that has a cobalt-based binder wherein the cemented
carbide blank contains additives of chromium and molybdenum, and in
some cases nickel. The cemented tungsten carbide blank is suitable
for EDM, and especially prolonged EDM in excess of 30 hours and
even in excess of 100 hours and even still in excess of 500 hours,
wherein the exposed surface is essentially free of defects caused
by electrolytic corrosion or the EDM process.
[0002] Very basically, electric discharge machining (EDM) is a
process for making a body that typically has a complex shape. An
electrode (e.g., a wire) is positioned near the blank (or body) to
be subjected to EDM and the electrode and the blank are placed at
different electrical potentials. A controlled electric spark
travels between the electrode and the blank that causes the blank
to be eroded or explosively evaporated and thereby cut or shaped
into the desired configuration. It is typical that the electrode
and the blank are located within a liquid dielectric solution. EDM
is a very precise method of machining and can be used to make
finished bodies of complex shapes. Exemplary products that can be
made by EDM include stamping dies and stamping punches.
[0003] Cemented carbides (e.g., cobalt cemented tungsten carbide)
have many advantageous properties so that for some applications, it
would be desirable to be able to use EDM to shape a cemented
carbide body. While EDM has been used to shape cemented carbides
such as, for example, a cobalt cemented tungsten carbide, there
have been some drawbacks. In this regard, heretofore, the surface
of an EDM finished cemented carbide body has experienced "pitting"
wherein holes appear in the surface of the body. The EDM finished
cemented carbide body can also experience pitting or corrosion of
material underneath (and near to) the surface. The EDM finished
cemented carbide body may also experience cracking caused by the
EDM process. The EDM finished cemented carbide body may also suffer
a decrease in the strength of the material.
[0004] It appears that there is an electrochemical corrosion
phenomena that takes place so as to remove by corrosion the binder
material (e.g., cobalt in the case of a cobalt cemented tungsten
carbide body) from the body so as to create these surface pits or
the sub-surface pitting as well as result in the cracking. The
presence of the pitting and cracking has also resulted in a
decrease in the strength of the body.
[0005] The fact that the surface of the body is subjected to high
heat and electrical energy, as well as the fact that the body
itself may remain immersed in the dielectric solution for many
hours (e.g., up to thirty hours or even one hundred hours or even
still up to five hundred hours), accelerates and enhances the
electrochemical corrosion of the cobalt binder of the cobalt
cemented tungsten carbide body. Thus, it can be appreciated that
while the properties of cemented carbides (and especially tungsten
carbide-cobalt material) are very advantageous so as to be very
applicable for parts of complex shapes, the nature of EDM has
inherent drawbacks for use with a material like a tungsten
carbide-cobalt alloy.
[0006] U.S. Pat. No. 6,514,456 B1 to Lackner et al. pertains to a
material that may be subjected to EDM. The Lackner et al. patent
appears to disclose a cobalt cemented tungsten carbide alloy that
contains one or more additives selected from the group consisting
rhenium (Re), germanium (Ge), gallium (Ga), iridium (Ir), osmium
(Os), palladium (Pd), silver (Ag), gold (Au), platinum (Pt),
tellurium (Te), rhodium (Rh), and ruthenium (Ru). According to the
Lackner et al. patent, the cemented carbide alloy is resistant to
"pitting". Comparative Example 3 of the Lackner et al. patent
consists of a cobalt cemented tungsten carbide alloy made by a
powder comprising 12 weight percent cobalt, 0.8 weight percent
chromium carbide and the balance tungsten carbide. According to the
Lackner et al. patent, the chromium carbide was dissolved and the
chromium fraction was dissolved in the binder. According to the
Lackner et al. patent, this Comparative Example 3 does not exhibit
corrosion resistance as good as the corrosion resistance of the
composition of the Lackner et al. patent that includes rhenium (Re)
that is an additive from the above group (i.e., Re, Ge, Ga, Ir, Os,
Pd, Ag, Au, Pt, Te, Rh, and Ru). An article by L{haeck over
(a)}mmle et al. entitled "Hardmetal in the Toolmaking Industry is a
question of confidence", Plansee TIZIT AG, Edition 4, January 2000
pertains to a grade of tungsten carbide-cobalt material that the
article says contains chromium and rhenium. According to L{haeck
over (a)}mmle et al., this grade has application for EDM in that it
is a grade that is resistant to corrosion and pitting.
[0007] While the Lackner et al. patent and the L{haeck over
(a)}mmle et al. article each says that it discloses an alloy that
has resistance to "pitting" as a result of EDM, because "pitting"
is an undesirable result, it still remains as a goal to provide a
cemented carbide (e.g., tungsten carbide-based material that
contains cobalt) that is suitable for EDM without suffering
"pitting" or any significant "pitting" as a result of the EDM
process. It also remains as a goal to provide a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not suffer any pitting or loss of binder in the surface region
underneath the surface of the body as a result of an EDM process.
It still further remains as a goal to provide a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not suffer any cracking at the surface as a result of an EDM
process. It yet additionally remains as a goal to provide a
cemented carbide (e.g., tungsten carbide-based material that
contains cobalt) that does not experience a significant reduction
in strength as a result of an EDM process.
[0008] The materials disclosed in the Lackner et al. patent use
additives (i.e., Re, Ge, Ga, Ir, Os, Pd, Ag, Au, Pt, Te, Rh, and
Ru) that are exotic elements in the field of cemented carbides, and
especially in the field of cobalt cemented tungsten carbides. The
use of these exotic elements as additives in cemented carbides,
such as, for example, cobalt cemented tungsten carbide, makes the
material more expensive.
[0009] It thus would be highly desirable to provide a cemented
carbide (e.g., tungsten carbide-based material that contains
cobalt) that does not contain exotic elements (i.e., Re, Ge, Ga,
Ir, Os, Pd, Ag, Au, Pt, Te, Rh, and Ru) as additives and that is
suitable for EDM without suffering, or at least reducing, "pitting"
or any significant "pitting" as a result of the EDM process. It
would also be highly desirable to provide a cemented carbide (e.g.,
tungsten carbide-based material that contains cobalt) that does not
contain exotic elements (i.e., Re, Ge, Ga, Ir, Os, Pd, Ag, Au, Pt,
Te, Rh, and Ru) as additives and that does not suffer any, or at
lest reduces, pitting or loss of binder in the surface region
underneath the surface of the body as a result of an EDM process.
It further would be highly desirable to provide a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not contain exotic elements (i.e., Re, Ge, Ga, Ir, Os, Pd, Ag,
Au, Pt, Te, Rh, and Ru) as additives and that does not suffer any,
or at least reduces, cracking at the surface as a result of an EDM
process. Finally, it would be highly desirable to provide a
cemented carbide (e.g., tungsten carbide-based material that
contains cobalt) that does not contain exotic elements (i.e., Re,
Ge, Ga, Ir, Os, Pd, Ag, Au, Pt, Te, Rh, and Ru) as additives and
that does not experience a significant reduction in strength as a
result of an EDM process.
SUMMARY OF THE INVENTION
[0010] In one form thereof the invention is a cemented carbide
blank suitable for fabrication by electric discharge machining that
includes a carbide phase that includes tungsten carbide (and
optionally vanadium carbide) present in an amount equal to between
about 77.7 weight percent and about 93.6 weight percent of the
cemented carbide blank. The cemented carbide blank further includes
chromium present in an amount equal to between about 0.3 weight
percent and about 1.5 weight percent of the cemented carbide blank,
cobalt present in an amount equal to between about 8 weight percent
and about 17 weight percent of the cemented carbide blank, nickel
optionally present in an amount equal to 0 weight percent up to
about 5 weight percent of the cemented carbide blank, and
molybdenum present in an amount equal to between about 0.1 weight
percent and about 1.0 weight percent of the cemented carbide blank.
The cemented carbide blank having a magnetic saturation as measured
according to ASTM B886-03 ranging between about 151.times.10.sup.-6
T m.sup.3/kilogram cobalt and about 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
[0011] In another form thereof the invention is a cemented carbide
body made by electric discharge machining. The cemented carbide
body comprises tungsten carbide (and optionally vanadium carbide)
present in an amount equal to between about 77.7 weight percent and
about 93.6 weight percent of the cemented carbide blank. The
cemented carbide blank further includes chromium present in an
amount equal to between about 0.3 weight percent and about 1.5
weight percent of the cemented carbide blank, cobalt present in an
amount equal to between about 8 weight percent and about 17 weight
percent of the cemented carbide blank, nickel optionally present in
an amount equal to 0 weight percent up to about 5 weight percent of
the cemented carbide blank, and molybdenum present in an amount
equal to between about 0.1 weight percent and about 1.0 weight
percent of the cemented carbide blank. The cemented carbide blank
having a magnetic saturation as measured according to ASTM B886-03
ranging between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt
and about 182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0012] In one form thereof the invention is a cemented carbide
blank suitable for fabrication by electric discharge machining. The
cemented carbide blank comprises tungsten carbide present in an
amount equal to between about 80 weight percent and about 90.9
weight percent of the cemented carbide blank. The cemented carbide
blank further includes chromium present in an amount equal to
between about 0.3 weight percent and about 1.5 weight percent of
the cemented carbide blank, cobalt present in an amount equal to
between about 8 weight percent and about 14 weight percent of the
cemented carbide blank, nickel present in an amount equal to
between about 0.7 weight percent and about 1.3 weight percent of
the cemented carbide blank, and molybdenum present in an amount
equal to between about 0.1 weight percent and about 0.3 weight
percent of the cemented carbide blank. The cemented carbide blank
has a magnetic saturation as measured according to ASTM B886-03
ranging between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt
and about 171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0013] In another form thereof, the invention is a cemented carbide
body made by electric discharge machining. The cemented carbide
body comprises tungsten carbide present in an amount equal to
between about 80 weight percent and about 90.9 weight percent of
the cemented carbide body. The cemented carbide body further
includes chromium present in an amount equal to between about 0.3
weight percent and about 1.5 weight percent of the cemented carbide
body, cobalt present in an amount equal to between about 8 weight
percent and about 14 weight percent of the cemented carbide body,
nickel present in an amount equal to between about 0.7 weight
percent and about 1.3 weight percent of the cemented carbide body,
and molybdenum present in an amount equal to between about 0.1
weight percent and about 0.3 weight percent of the cemented carbide
body. The cemented carbide body has a magnetic saturation as
measured according to ASTM B886-03 ranging between about
151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about
171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0014] In still another form thereof, the invention is a cemented
carbide blank suitable for fabrication by electric discharge
machining. The cemented carbide blank comprises a carbide phase
present in an amount equal to between about 88.5 weight percent and
about 93.6 weight percent of the cemented carbide blank wherein the
carbide phase includes tungsten and vanadium and carbon. The
cemented carbide blank further includes chromium present in an
amount equal to between about 0.3 weight percent and about 0.9
weight percent of the cemented carbide blank, cobalt present in an
amount equal to between about 6 weight percent and about 10 weight
percent of the cemented carbide blank, and molybdenum present in an
amount equal to between about 0.1 weight percent and about 0.6
weight percent of the cemented carbide blank. The cemented carbide
blank has a magnetic saturation as measured according to ASTM
B886-03 ranging between about 151.times.10' T m.sup.3/kilogram
cobalt and about 171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0015] In yet another form thereof, the invention is a cemented
carbide body made by electric discharge machining. The cemented
carbide body comprises a carbide phase present in an amount equal
to between about 88.5 weight percent and about 93.6 weight percent
of the cemented carbide body wherein the carbide phase includes
tungsten and vanadium and carbon. The cemented carbide body further
includes chromium present in an amount equal to between about 0.3
weight percent and about 0.9 weight percent of the cemented carbide
body, cobalt present in an amount equal to between about 6 weight
percent and about 10 weight percent of the cemented carbide body,
and molybdenum present in an amount equal to between about 0.1
weight percent and about 0.6 weight percent of the cemented carbide
body. The cemented carbide body has a magnetic saturation as
measured according to ASTM B886-03 ranging between about
151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about
171.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0016] In still another form thereof, the invention is a cemented
carbide blank suitable for fabrication by electric discharge
machining. The cemented carbide blank comprises tungsten carbide
present in an amount equal to between about 77.7 weight percent and
about 87.9 weight percent of the cemented carbide blank. The
cemented carbide blank further includes chromium present in an
amount equal to between about 0.4 weight percent and about 1.3
weight percent of the cemented carbide blank, cobalt present in an
amount equal to between about 9.5 weight percent and about 15
weight percent of the cemented carbide blank, nickel present in an
amount equal to between about 2 weight percent and about 5 weight
percent of the cemented carbide blank, and molybdenum present in an
amount equal to between about 0.2 weight percent and about 1.0
weight percent of the cemented carbide blank. The cemented carbide
blank has a magnetic saturation as measured according to ASTM
B886-03 ranging between about 151.times.10' T m.sup.3/kilogram
cobalt and about 182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
[0017] In yet another form thereof, the invention is a cemented
carbide body made by electric discharge machining. The cemented
carbide body comprises a body presenting a selected shape. The body
comprises tungsten carbide present in an amount equal to between
about 77.7 weight percent and about 87.9 weight percent of the
cemented carbide body. The cemented carbide body further includes
chromium present in an amount equal to between about 0.4 weight
percent and about 1.3 weight percent of the cemented carbide body,
cobalt present in an amount equal to between about 9.5 weight
percent and about 15 weight percent of the cemented carbide body,
nickel present in an amount equal to between about 2 weight percent
and about 5 weight percent of the cemented carbide body, and
molybdenum present in an amount equal to between about 0.2 weight
percent and about 1.0 weight percent of the cemented carbide body.
The cemented carbide body having a magnetic saturation as measured
according to ASTM B886-03 ranging between about 151.times.10.sup.-6
T m.sup.3/kilogram cobalt and about 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
[0018] In yet another form thereof the invention is a cemented
carbide blank suitable for fabrication by electric discharge
machining. The cemented carbide blank comprises tungsten carbide
present in an amount equal to between about 81.1 weight percent and
about 86.4 weight percent of the cemented carbide blank; chromium
present in an amount equal to between about 0.4 weight percent and
about 1.3 weight percent of the cemented carbide blank; cobalt
present in an amount equal to between about 13 weight percent and
about 17 weight percent of the cemented carbide blank; and
molybdenum present in an amount equal to between about 0.2 weight
percent and about 0.6 weight percent of the cemented carbide blank.
The cemented carbide blank has a magnetic saturation as measured
according to ASTM B886-03 ranging between about 151.times.10.sup.-6
T m.sup.3/kilogram cobalt and about 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt.
[0019] In still another form thereof, the invention is a cemented
carbide body made by electric discharge machining. The cemented
carbide body comprises a body presenting a selected shape. The body
comprises tungsten carbide present in an amount equal to between
about 81.1 weight percent and about 86.4 weight percent of the
cemented carbide blank; chromium present in an amount equal to
between about 0.4 weight percent and about 1.3 weight percent of
the cemented carbide blank; cobalt present in an amount equal to
between about 13 weight percent and about 17 weight percent of the
cemented carbide blank; and molybdenum present in an amount equal
to between about 0.2 weight percent and about 0.6 weight percent of
the cemented carbide blank. The cemented carbide blank having a
magnetic saturation as measured according to ASTM B886-03 ranging
between about 151.times.10.sup.-6 T m.sup.3/kilogram cobalt and
about 182.times.10.sup.-6 T m.sup.3/kilogram cobalt.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The following is a brief description of the drawings that
form a part of this patent application:
[0021] FIG. 1 is an isometric view of a blank that may be
fabricated (or made) into a finished body (or product) by EDM
techniques;
[0022] FIG. 2 is a photomicrograph that shows the microstructure of
the specific embodiment of Example 1 wherein there is a 10
micrometer (.mu.m) scale;
[0023] FIG. 3 is a photomicrograph of the top surface of the
specific embodiment of Example 1 subjected to a rough cut EDM
process and wherein there is a 20 micrometer (.mu.m) scale;
[0024] FIG. 4 is a photomicrograph of a cross-section of the
surface of the specific embodiment of the invention shown in FIG. 3
(subjected to a rough cut EDM process) wherein there is a 20
micrometer (.mu.m) scale;
[0025] FIG. 5 is a photomicrograph at one location of a
cross-section of the surface of the specific embodiment of the
invention shown in FIG. 3 (subjected to a rough cut EDM process)
wherein there is a 10 micrometer (.mu.m) scale;
[0026] FIG. 6 is a photomicrograph at another location of a
cross-section of the surface of the specific embodiment of the
invention shown in FIG. 3 (subjected to a rough cut EDM process)
wherein there is a 10 micrometer (.mu.m) scale;
[0027] FIG. 7 is a photomicrograph at one location of a
cross-section of the surface of the specific embodiment of Example
1 subjected to a fine cut EDM process wherein there is a 10
micrometer (.mu.m) scale;
[0028] FIG. 8 is a photomicrograph at another location of a
cross-section of the surface of the specific embodiment of FIG. 7
(subjected to a fine cut EDM process) wherein there is a 20
micrometer (.mu.m) scale;
[0029] FIG. 9 is a corrosion plot that compares the corrosion
resistance of the following materials: a standard tungsten
carbide-12 weight percent cobalt grade, and a tungsten
carbide-cobalt-based alloy made by Plansee TIZIT and sold under the
designation CF H40S, and a cemented carbide blank of the specific
embodiment of Example 1; and
[0030] FIG. 10 is a photomicrograph that shows the microstructure
of a cemented carbide blank of the specific embodiment of Example 3
wherein there is a 10 micrometer (.mu.m) scale.
DETAILED DESCRIPTION OF THE INVENTION
[0031] Referring to the drawings, FIG. 1 shows a cemented carbide
blank 20 of material made according to the present invention. This
blank 20 may be subjected to EDM so as to fabricate a part (or a
cemented carbide body). EDM is a technique that is suitable for the
fabrication of parts that have complex shapes so that the present
invention provides a material that is applicable to many products
including stamping dies and stamping punches. It should also be
appreciated that the material of the invention can be used to
fabricate components of fluid handling equipment used in the oil,
gas and chemical industries. One of these components can be a part
of a ball valve assembly, and more particularly, the extreme seat
in a ball valve assembly.
[0032] Some applications for hard materials require parts of a
complex shape so that EDM is a very suitable process to fabricate
the part. However, for a hard material like a tungsten
carbide-cobalt alloy EDM may not be a suitable fabrication
technique due to the negative effects of electrochemical corrosion
of the cobalt from the tungsten carbide-cobalt alloy that occurs
during the EDM. However, by the present invention, one can take the
basic composition of a hard material (e.g., a cobalt cemented
tungsten carbide) that has suitable properties (e.g., hardness or
toughness), and modify such composition so as to make it resistant
to the electrochemical corrosive effects of EDM, as well as the
susceptibility to cracking during the EDM process, so that it can
be fabricated by EDM into a finished cemented carbide body that
still possesses its desirable properties (e.g., hardness or
toughness and the like).
[0033] Example 1 is one specific embodiment of the present
invention. Example 1 comprises a tungsten carbide-based material
that has a carbide phase that includes tungsten carbide and a
cobalt-based binder phase. The tungsten carbide-based material
further includes additions of nickel and chromium and molybdenum
wherein at least some of these additions (i.e., nickel and chromium
and molybdenum) are present in the binder phase. Example 1 is made
by powder metallurgical techniques. The starting powder mixture
comprises:
[0034] about 85.8 weight percent tungsten carbide wherein the
tungsten carbide has a particle size equal to 1 to 4 micrometers
(.mu.m), about 1.0 weight percent chromium carbide (equals about
0.9 weight percent chromium), about 10.8 weight percent cobalt,
about 1.0 weight percent nickel, about 1.2 weight percent tungsten,
and about 0.2 weight percent molybdenum.
[0035] This starting powder mixture was ball milled for between
about 6 hours to about 8 hours. The ball-milled powder mixture was
then pressed into a green compact. The green compact was then
dewaxed at a temperature between about 400 degrees Centigrade and
about 650 degrees Centigrade. The dewaxed compact was then sintered
under the following conditions: a temperature equal to about 1405
degrees Centigrade for about 60 minutes in a vacuum to form a
sintered body. The sintered body was then hot isostatically pressed
under the following conditions: a temperature equal to about 1405
degrees Centigrade at a pressure equal to 450 pounds per square
inch (psi) (3.1 MPa) in argon gas for 30 minutes to form the
consolidated cemented carbide blank.
[0036] The consolidated cemented carbide blank of Example 1 is a
tungsten carbide-based cobalt alloy that contains chromium and
nickel and molybdenum. The cemented carbide blank of Example 1 has
the following composition (wherein the weight percent is of the
entire consolidated cemented carbide blank): about 87.1 weight
percent tungsten carbide, about 0.9 weight percent chromium, abut
10.8 weight percent cobalt, about 1.0 weight percent nickel, and
about 0.2 weight percent molybdenum. The cemented carbide blank of
Example 1 has the following properties: a density of about
14.2.+-.0.1 grams per cubic centimeter, a coercive force (H.sub.C)
measured in oersteds of about 170, a Rockwell A hardness equal to
about 90.0.+-.0.4, a magnetic saturation equal to between about to
151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
171.times.10.sup.-6 T m.sup.3/kilogram cobalt, a porosity of about
A02B00C00, and a transverse rupture strength equal to about
3500.+-.200 MPa.
[0037] The properties for Example 1, as well as those for Examples
2 through 4 set forth hereinafter, were determined per the various
ASTM standards (ASTM International, 100 Barr Harbor Drive, West
Conshohocken, Pa. 19428, USA) set forth below. The density was
measured according to the procedure set forth in ASTM B311-93(2000)
(Test Method for Density Determination for Powder Metallurgy
(Materials Containing Less Than Two Percent Porosity)). The
coercive force was measured according to the procedure set forth in
ASTM Standard B887-03 (Standard Test Method for Determination of
Coercivity (H.sub.CS) of Cemented Carbides). The Rockwell A
hardness was measured according to the procedure set forth in ASTM
Standard B294-92 (2001) (Standard Test Method for Hardness Testing
of Cemented Carbides). The magnetic saturation was measured
according to the procedure set forth in ASTM Standard B886-03
(Standard Test Methods for Determination of Magnetic Saturation
(M.sub.s) in Cemented Carbides). The porosity was determined
according to the procedure set forth in ASTM B276-91(2000)
(Standard Test Method for Apparent Porosity in Cemented Carbides).
The transverse rupture strength was measured according to the
procedures set forth in ASTM Standard B406-96(2000) (Standard Test
Method for Transverse Rupture Strength of Cemented Carbides).
[0038] A visual examination (at 200.times.) of the etched
microstructure showed that there was an absence of eta phase from
the consolidated cemented carbide blank of Example 1.
[0039] As previously discussed, the consolidated cemented carbide
blank may be subjected to EDM so as to form the EDM finished
product.
[0040] In regard to the components of the starting powder mixture
for Example 1, it should be appreciated that the tungsten carbide
component may also comprise in whole or in part macrocrystalline
tungsten carbide. U.S. Pat. No. 3,379,503 to McKenna and U.S. Pat.
No. 4,834,963 to Terry et al. disclose macrocrystalline tungsten
carbide and processes to make the same. It should be appreciated
that although the starting powder mixture of Example 1 uses
chromium carbide to contribute chromium to the mixture, one could
use chromium metal in the appropriate amount (e.g., for Example 1
the chromium component would equal about 0.9 weight percent).
[0041] In further regard to the components of the starting powder
mixture of Example 1, the components of the starting powder may
fall within the following range that comprises: between about 84.2
weight percent and about 90.1 weight percent tungsten carbide,
between about 0.4 weight percent and about 1.2 weight percent
chromium carbide (or chromium equal to between about 0.3 weight
percent and about 1 weight percent), between about 8 weight percent
and about 11 weight percent cobalt, between about 0.7 weight
percent and about 1.3 weight percent nickel, 0 weight percent to
about 2 weight percent tungsten, and between about 0.1 weight
percent and about 0.3 weight percent molybdenum.
[0042] In regard to the process parameters used to make Example 1,
it should be appreciated that the sintering parameters may be
within the following ranges: a temperature range between about 1360
degrees Centigrade and about 1500 degrees Centigrade (and an
alternate temperature range between ranging between about 1400
degrees Centigrade and about 1450 degrees Centigrade) for a
duration ranging between about 60 minutes to about 90 minutes in a
vacuum. It should be appreciated that the hot isostatic pressing
parameters may be within the following ranges: a temperature range
of between about 1360 degrees Centigrade and about 1500 degrees
Centigrade (and an alternate range between ranging between about
1400 degrees Centigrade and about 1450 degrees Centigrade) and a
pressure range between about 80 psi and higher (and an alternate
pressure range between about 300 psi and about 800 psi) for a
duration between about 60 minutes and about 120 minutes.
[0043] Applicant contemplates that a consolidated cemented carbide
blank along the lines of Example 1 may have the following range of
composition (wherein the weight percent is of the entire
consolidated cemented carbide blank): between about 80 weight
percent and about 90.9 weight percent tungsten carbide, between
about 0.3 weight percent and about 1.5 weight percent chromium,
between about 8 weight percent and about 14 weight percent cobalt,
between about 0.7 weight percent and about 1.3 weight percent
nickel, and between about 0.1 weight percent and about 0.3 weight
percent molybdenum. An alternate range of composition (wherein the
weight percent is of the entire consolidated cemented carbide
blank) comprises: between about 85 weight percent and about 90.9
weight percent tungsten carbide, between about 0.3 weight percent
and about 1.1 weight percent chromium, between about 8 weight
percent and about 11 weight percent cobalt, between about 0.7
weight percent and about 1.3 weight percent nickel, and between
about 0.1 weight percent and about 0.3 weight percent molybdenum.
Yet, another alternate range of composition (wherein the weight
percent is of the entire consolidated cemented carbide blank)
comprises between about 85.4 weight percent and about 88.4 weight
percent tungsten carbide, between about 0.6 weight percent and
about 1.2 weight percent chromium, between about 10 weight percent
and about 12 weight percent cobalt, between about 0.9 weight
percent and about 1.1 weight percent nickel, and between about 0.1
weight percent and about 0.3 weight percent molybdenum.
[0044] In regard to the relation between the cobalt, chromium,
nickel, and molybdenum, in one range, the chromium comprises
between about 1.9 weight percent and about 14 weight percent of the
sum of the elements cobalt and chromium and nickel and molybdenum,
the nickel comprises between about 4.3 weight percent and about
14.4 weight percent of the sum of the elements cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 0.6 weight percent and about 3.3 weight percent of the sum of
the elements cobalt and chromium and nickel and molybdenum. In
another range, the chromium comprises between about 4.3 weight
percent and about 10 weight percent of the sum of the elements
cobalt and chromium and nickel and molybdenum, the nickel comprises
between about 6.4 weight percent and about 9.2 weight percent of
the sum of the elements cobalt and chromium and nickel and
molybdenum, and the molybdenum comprises between about 0.6 weight
percent and about 3.3 weight percent of the sum of the elements
cobalt and chromium and nickel and molybdenum.
[0045] In regard to the range of the properties of a consolidated
cemented tungsten carbide blank using a starting powder mixture of
Example 1 within the above ranges, the blank has the following
range of properties: a density between about 13.9 and about 14.6
grams per cubic centimeter, a coercive force (H.sub.C) measured in
oersteds between about 110 and about 170, a Rockwell A hardness
between about 88 and about 90, a magnetic saturation between about
151 10.sup.-6 T m.sup.3/kilogram cobalt and about 182 10.sup.-6 T
m.sup.3/kilogram cobalt, and a porosity better than or equal to A06
B02 C00.
[0046] The microstructure of the consolidated cemented carbide
blank of Example 1 is shown in FIG. 2. As can be seen, the
consolidated cemented carbide blank has a relatively fine-grained
microstructure.
[0047] The consolidated cemented carbide blank of Example 1 was
subjected to a so-called "rough cut" wire EDM under the following
conditions: faster cut at about 20 volts. FIGS. 3 through 6 shows
the surface region of the finished cemented carbide body of Example
1 after being subjected to the rough cut EDM as described above.
The microstructure shown in FIGS. 3 through 6 may be considered to
be essentially free of defects caused by EDM in the case of a rough
cut EDM process.
[0048] FIG. 3, which has a 20 micrometer (.mu.m) scale, showed only
a small pit (i.e., a dimension of about 10 micrometers (.mu.m)).
The rest of the surface of the finished body had a clean
appearance. The examination showed only a total of six pits over
the entire surface area (about 4 inches (about 10.2 centimeters) by
about 0.5 inches (about 1.3 centimeters) of the finished body.
[0049] FIG. 4 shows a cross-sectional photomicrograph of the
surface region of the cemented carbide body of Example 1 that
resulted from the above-described rough cut EDM. At this scale it
can be seen that the surface region was free of pitting and did not
show the effects of any electrochemical corrosion. FIGS. 5 and 6
are photomicrographs that also show in cross section the surface
region of the cemented carbide body of Example 1 that resulted from
the above-described rough cut EDM. It can be seen at this scale
that there was some pitting either at the surface or in the surface
region of the cemented carbide body underneath the surface.
[0050] The consolidated cemented carbide blank of Example 1 was
subjected to a so-called "fine cut" wire EDM under the following
conditions: slower cut at about 10 volts. FIGS. 7 and 8 show in
cross-section the surface region of the cemented carbide body of
Example 1 that resulted from the EDM fine cut as described above.
As can be seen from these photomicrographs, the surface region of
this body of Example 1 did not suffer any effects of
electrochemical corrosion such as, for example, pitting at the
surface or pitting in the surface region beneath the surface. The
microstructure shown in FIGS. 7 and 8 may be considered to be
essentially free of defects caused by EDM in the case of a fine cut
EDM process.
[0051] An examination of the finished cemented carbide body of
Example 1 that was the result from the fine cut EDM process shows
that this material of Example 1 exhibited excellent corrosion
resistance. Example 1 did not present severe pitting at the
surface. The material of Example 1 did not suffer the pitting and
corrosion in the surface region beneath the surface. The material
of Example 1 did not experience the cracking caused by the EDM
process. The material of Example 1 did not experience a significant
loss in strength wherein after EDM it retained at least between
about 50 percent to 60 percent of the original strength. It can
thus be seen that the finished consolidated cemented carbide body
of Example 1 is a material that is able to satisfactorily withstand
electrochemical corrosion that occurs during a fine cut EDM
process.
[0052] Referring to FIG. 9, the cemented carbide blank of Example 1
was tested against a tungsten carbide-cobalt-based material made
and sold by Plansee TIZIT under the designated CF H40S and a
standard tungsten carbide-12 weight percent cobalt grade to
determine the relative resistance to electrochemical corrosion of
these materials. According to analyses by the assignee of the
present patent application (i.e., Kennametal Inc.), the Plansee
CF-H40S grade of material has the following composition and
properties. The basic composition is about 11.7 weight percent
cobalt, about 1.0 weight percent chromium, about 0.04 weight
percent molybdenum, about 0.07-0.085 weight percent iron and about
0.04 weight percent titanium and the balance tungsten carbide.
Kennametal Inc.'s analysis did not analyze the material for
rhenium, but according to the heretofore-mentioned article by
L{haeck over (a)}mmle et al. entitled "Hardmetal in the Toolmaking
Industry is a question of confidence", this Plansee grade contains
chromium and rhenium. Per Kennametal Inc.'s analyses, the
properties comprise a porosity of A02 B00 C00, a tungsten carbide
grain size of 1-5 micrometers, a magnetic saturation equal to
161-175.times.10.sup.-6 T m.sup.3/kilogram cobalt, a coercive force
(H.sub.C) equal to 136-139 oersteds, a Rockwell A hardness equal to
90.3-90.4 HRA, a Vickers Hardness (30 kilogram load) equal to
1448.+-.6, and a density equal to 14.11-14.14 grams per cubic
centimeter.
[0053] The lines in FIG. 9 are labeled "EXAMPLE 1" to refer to the
cemented carbide blank of Example 1, "CF-H40S" to refer to the
Plansee grade, and "WC-12 wt % Co" to refer to the standard grade
that comprises about 12 weight percent cobalt and about 88 weight
percent tungsten carbide. Electrochemical corrosion is the kind of
corrosion that a material is exposed to during EDM. The test
procedure standard to determine the resistance to electrochemical
corrosion is ASTM G5-94(1999)e1 entitled "Standard Reference Test
Method for Making Potentiostatic and Potentiodynamic Anodic
Polarization Measurements".
[0054] This test per ASTM G5-94(1999)e1 is an accelerated test. It
is based on the principle that corrosion is an oxidation process by
which electrons are released from the corroded specimen. In the
electrochemical cell (i.e., that flask (or container) with the
corroding solution therein), a voltage is applied between the anode
(the specimen) and the cathode (graphite rods), and the current
that is generated as a result is then measured. In this test, the
corroding solution was 0.1 N hydrochloric acid. The measured
current is a measure or a reflection of the corrosion rate of a
material.
[0055] A plot such as shown in FIG. 9 is generated as a result of
the testing. The x-axis of the plot is the applied potential across
the anode (specimen) and the cathode (graphite rod). This applied
potential is measured in E (mv). This figure is a measure of the
intensity of the corrosive environment. The y-axis is a logarithm
of the current generated in the external circuit as a result of the
applied potential difference. The specific current is measured in
A/m.sup.2. This figure is a measure of the corrosion rate of the
specimen.
[0056] As can be seen in FIG. 9, the plot has two branches that are
separated by a vertical line. The position of the vertical line is
indicative of the inherent nobility of the material. In a
comparison on the two plots (i.e., a plot of the Plansee material
and a plot of the Example 1 material), the material that has its
plot that has the vertical line on the farther right is more noble
than the other material. FIG. 9 shows that one specific embodiment
of the invention, i.e., the consolidated cemented carbide blank of
Example 1, exhibits a corrosion rate that was about 20 to about 30
times lower as compared to the Plansee material.
[0057] The right-side horizontal branch (i.e., the anodic part) is
indicative of the corrosion rate and the type. The lower the line
represents the lower the current and the lower corrosion rate. A
drop in the corrosion current is indicated by a depression in the
anodic part is indicative of passivation where a protective layer
is formed on the surface of the material.
[0058] Example 2 is another specific embodiment of the invention.
Example 2 was made using the following starting powder mixture:
about 91.2 weight percent tungsten carbide (the particle size of
the tungsten carbide is about 0.4 to about 0.6 micrometers
(.mu.m)), about 8.0 weight percent cobalt, about 0.5 weight percent
chromium carbide (Cr.sub.3C.sub.2), about 0.1 weight percent
vanadium carbide, about 0.5 weight percent tungsten, and about 0.2
weight percent molybdenum. This powder mixture was attritor milled
in heptane using cemented carbide balls for about 6 hours.
[0059] The powder mixture was then pressed into a green compact.
The green compact was de-waxed at a temperature between about 400
degrees Centigrade and about 650 degrees Centigrade. The de-waxed
compact was then sintered at 1405 degrees Centigrade for 60 minutes
in a vacuum followed by hot isostatic pressing at a temperature of
about 1405 degrees Centigrade and a pressure equal to about 450
pounds per square inch (3.1 MPa) in argon gas for a duration equal
to about 30 minutes.
[0060] The consolidated cemented carbide blank of Example 2 has the
following composition: about 91.3 weight percent tungsten carbide
(the particle size of the tungsten carbide is about 0.4 to about
0.6 micrometers (.mu.m)), about 0.1 weight percent vanadium carbide
that applicant believes is in solid solution with the tungsten
carbide, about 8.0 weight percent cobalt, about 0.4 weight percent
chromium, and about 0.2 weight percent molybdenum. The binder is
cobalt-based and applicant believes that the binder contains at
least some of the chromium and molybdenum.
[0061] The consolidated cemented carbide blank of Example 2 has
properties that fall within the following ranges: a density equal
to between about 14.5 and about 14.8 grams per cubic centimeter, a
coercive force (Hc) measured in oersteds between about 260 and
about 310, a Rockwell A hardness equal to about 92.5 and about 93,
a magnetic saturation equal to between about 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about to 171.times.10.sup.-6 T
m.sup.3/kilogram cobalt, a transverse rupture strength (TRS) equal
to between about 3500 MPa and about 3700 MPa, and a porosity of
A02B00C00. A visual examination (200.times.) showed that there was
no eta phase present in the microstructure.
[0062] The consolidated cemented carbide blank of Example 2 is
suitable to be subjected to EDM so as to form an EDM finished
cemented carbide body.
[0063] In regard to the starting components for Example 2,
applicant contemplates that the components of the starting powder
mixture may fall within the following range (weight percent of the
starting powder mixture):
[0064] between about 90 weight percent and about 94 weight percent
tungsten carbide, between about 0.5 weight percent and about 1.0
weight percent chromium carbide (in the case of an addition of
chromium metal, between about 0.4 weight percent and about 0.9
weight percent chromium), between about 6 weight percent and about
10 weight percent cobalt, up to about 0.3 weight percent vanadium
carbide, 0 weight percent to about 1 weight percent tungsten, and
between about 0.1 weight percent and about 0.6 weight percent
molybdenum. A consolidated cemented carbide blank made with a
starting powder mixture within the above range has the following
range of composition (weight percent of the cemented carbide
blank): between about 90.1 weight percent and about 93.6 weight
percent tungsten carbide (the particle size of the tungsten carbide
is about 0.4 to about 0.6 micrometers (.mu.m)), up to about 0.3
weight percent vanadium carbide wherein applicant believes that the
vanadium carbide is in solid solution with the tungsten carbide,
between about 6 weight percent and about 10 weight percent cobalt,
between about 0.3 weight percent and about 0.9 weight percent
chromium, and between about 0.1 weight percent and about 0.6 weight
percent molybdenum. The cemented carbide blank has a binder phase
that includes at least some of the cobalt, chromium and
molybdenum.
[0065] In regard to the relationship of the components of the
elements cobalt, chromium and molybdenum, in one range the chromium
comprises between about 3 weight percent and about 15.8 weight
percent of the sum of the cobalt and chromium and molybdenum, and
the molybdenum comprises between about 1 weight percent and about
10.5 weight percent of the sum of the cobalt and chromium and
molybdenum. In another range, the chromium comprises between about
3 weight percent and about 8 weight percent of the sum of the
cobalt and chromium and molybdenum, and the molybdenum comprises
between about 1 weight percent and about 5 weight percent of the
sum of the cobalt and chromium and molybdenum.
[0066] Applicant contemplates that a consolidated cemented carbide
blank along the lines of Example 2 can have properties within the
following range: a density between about 13.9 and about 14.6 grams
per cubic centimeter, a coercive force (H.sub.C) measured in
oersteds between about 250 and about 350, a Rockwell A hardness
between about 92 and about 93.5, a magnetic saturation between
about 171.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
182.times.10.sup.-6 T m.sup.3/kilogram cobalt, and a porosity that
is better than or equal to A04B00C00.
[0067] In regard to the process parameters to make the consolidated
cemented carbide blank of Example 2, the sintering parameters and
the hot isostatic pressing parameters fall within the ranges set
forth above for Example 1.
[0068] The consolidated cemented carbide blank of Example 3 is
another specific embodiment of the invention wherein Example 3 is
made using the following starting powder mixture: about 84.6 weight
percent tungsten carbide (the particle size of the tungsten carbide
is about 4 to about 7 micrometers (.mu.m)), about 10 weight percent
cobalt, about 3 weight percent nickel, about 1 weight percent
chromium carbide (Cr.sub.3C.sub.2), about 1.2 weight percent
tungsten, and about 0.2 weight percent molybdenum. This powder
mixture was attritor milled in heptane using cemented carbide balls
for about 6 hours.
[0069] The powder mixture is then pressed into a green compact. The
green compact was de-waxed at a temperature between about 400
degrees Centigrade and about 650 degrees Centigrade. The de-waxed
compact was then sintered at 1405 degrees Centigrade for 60 minutes
in a vacuum followed by hot isostatic pressing at a temperature of
about 1405 degrees Centigrade and a pressure equal to about 450
pounds per square inch (3.1 MPa) in argon gas for a duration equal
to about 30 minutes so as to form a consolidated cemented carbide
blank. The consolidated cemented carbide blank of Example 3 may be
subjected to EDM so as to form the EDM finished cemented carbide
body.
[0070] The consolidated cemented carbide blank of Example 3 has the
following composition: about 85.9 weight percent tungsten carbide
(the particle size of the tungsten carbide is about 4 to about 7
micrometers (.mu.m)), about 10 weight percent cobalt, about 3
weight percent nickel, about 0.9 weight percent chromium, and about
0.2 weight percent molybdenum.
[0071] The consolidated cemented carbide blank of Example 3 has the
following properties: a density equal to about 14.2.+-.0.5 grams
per cubic centimeter, a coercive force (Hc) measured in oersteds
equal to about 120.+-.20, a Rockwell A hardness equal to about
88.4.+-.0.5 HRA, a magnetic saturation equal to 151.times.10.sup.-6
T m.sup.3/kilogram cobalt and about to 181.times.10.sup.-6 T
m.sup.3/kilogram cobalt, a transverse rupture strength (TRS) equal
to between about 3200 and about 3400 MPa, and a porosity equal to
A02B00C00. A visual examination at 200.times. showed that eta phase
was not present in the microstructure.
[0072] In regard to the starting components for Example 3,
applicant contemplates that the components of the starting powder
may fall within the following range (weight percent of the starting
powder mixture): between about 80 weight percent and about 90
weight percent tungsten carbide, between about 0.5 weight percent
and about 1.5 weight percent chromium carbide (in the case of an
addition of chromium metal, between about 0.4 weight percent and
about 1.3 weight percent chromium), between about 9.5 weight
percent and about 15 weight percent cobalt, between about 2 weight
percent and about 5 weight percent nickel, 0 weight percent to
about 1.5 weight percent tungsten, and between about 0.2 weight
percent and about 1.0 weight percent molybdenum. Applicant
contemplates that a consolidated cemented carbide blank made with a
powder mixture within the above range would have a composition
(weight percent of the cemented carbide blank) comprising between
about 80.1 weight percent and about 90.2 weight percent tungsten
carbide, between about 0.4 weight percent and about 1.3 weight
percent chromium, between about 9.5 weight percent and about 15
weight percent cobalt, between about 2 weight percent and about 5
weight percent nickel, and between about 0.2 weight percent and
about 1.0 weight percent molybdenum.
[0073] The relationship between the elements cobalt, chromium,
nickel and molybdenum has the following range: the chromium
comprises between about 2 weight percent and about 10 weight
percent of the sum of the cobalt and chromium and nickel and
molybdenum, the nickel comprises between about 10 weight percent
and about 33 weight percent of the sum of the cobalt and chromium
and nickel and molybdenum, and the molybdenum comprises between
about 1 weight percent and about 7.8 weight percent of the sum of
the cobalt and chromium and nickel and molybdenum.
[0074] Applicant contemplates that a consolidated cemented carbide
blank along the lines of Example 3 can have properties within the
following range: a density between about 13.8 and about 14.5 grams
per cubic centimeter, a coercive force (H.sub.C) measured in
oersteds between about 80 and about 150, a Rockwell A hardness
between about 85 and about 89, a magnetic saturation between
151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
182.times.10.sup.-6 T m.sup.3/kilogram cobalt, and a porosity
better than or equal to A06 B02 C00.
[0075] In regard to the ranges for the process parameters to make
Example 3, the sintering parameters and the hot isostatic pressing
parameters fall within the ranges set forth above for Example
1.
[0076] Another specific embodiment of the invention is Example 4.
Example 4 is a cobalt cemented tungsten carbide material made from
the following starting powder mixture (weight percent of the
starting powder mixture): about 82.8 weight percent tungsten
carbide (the particle size of the tungsten carbide is about 0.8 to
about 1.0 micrometers (.mu.m)), about 15 weight percent cobalt,
about 0.8 weight percent chromium carbide (Cr.sub.3C.sub.2), about
1.2 weight percent tungsten, and about 0.2 weight percent
molybdenum. This powder mixture was attritor milled in heptane
using cemented carbide balls for about 6 hours.
[0077] The powder mixture is then pressed into a green compact. The
green compact was de-waxed at a temperature between about 400
degrees Centigrade and about 650 degrees Centigrade. The de-waxed
compact was then sintered at 1405 degrees Centigrade for 60 minutes
in a vacuum followed by hot isostatic pressing at a temperature of
about 1405 degrees Centigrade and a pressure equal to about 450
pounds per square inch (3.1 MPa) in argon gas for a duration equal
to about 30 minutes so as to form a consolidated cemented carbide
blank. The consolidated cemented carbide blank of Example 4 may be
subjected to EDM so as to form the EDM finished cemented carbide
body.
[0078] The consolidated cemented carbide blank of Example 4 has the
following composition (weight percent of the cemented carbide
blank): about 84.1 weight percent tungsten carbide (the particle
size of the tungsten carbide is about 0.8 to about 1.2 micrometers
(.mu.m)), about 15 weight percent cobalt, about 0.7 weight percent
chromium, and about 0.2 weight percent molybdenum.
[0079] The consolidated cemented carbide blank of Example 4 has the
following properties: a density equal to about 13.97.+-.0.5 grams
per cubic centimeter, a coercive force (Hc) measured in oersteds
equal to about 208.+-.20, a Rockwell A hardness equal to about
89.8.+-.0.5 HRA, a magnetic saturation equal to 160.times.10.sup.-6
T m.sup.3/kilogram cobalt, a transverse rupture strength (TRS)
equal to about 4000.+-.200 MPa, and a porosity equal to better than
or equal to A02B00C00. A visual examination at 200.times. showed
that eta phase was not present in the microstructure.
[0080] In regard to the starting components for Example 4,
applicant contemplates that the components of the starting powder
may fall within the following one range (weight percent of the
starting powder mixture): between about 78.9 weight percent and
about 85.5 weight percent tungsten carbide, between about 0.5
weight percent and about 1.5 weight percent chromium carbide (when
added in the form chromium between about 0.4 and about 1.3 weight
percent chromium), between about 13 weight percent and about 17
weight percent cobalt, 0 weight percent to about 2.0 weight percent
tungsten, and between about 0.2 weight percent and about 0.6 weight
percent molybdenum. Applicant contemplates that a consolidated
cemented carbide body made with a powder mixture within the above
range would have a composition comprising between about 81.1 weight
percent and about 86.4 weight percent tungsten carbide, between
about 0.4 weight percent and about 1.3 weight percent chromium,
between about 13 weight percent and about 17 weight percent cobalt,
and between about 0.2 weight percent and about 0.6 weight percent
molybdenum.
[0081] The relationship between the elements cobalt, chromium, and
molybdenum has the following range: the chromium comprises between
about 2 weight percent and about 10 weight percent of the sum of
the cobalt and chromium and molybdenum, and the molybdenum
comprises between about 1 weight percent and about 4.4 weight
percent of the sum of the cobalt and chromium and molybdenum.
[0082] Applicant contemplates that a consolidated cemented carbide
blank along the lines of Example 4 can have properties within the
following range: a density between about 13.7 and about 14.3 grams
per cubic centimeter, a coercive force (H.sub.C) measured in
oersteds between about 180 and about 230, a Rockwell A hardness
between about 88 and about 90, a magnetic saturation between
151.times.10.sup.-6 T m.sup.3/kilogram cobalt and about to
182.times.10.sup.-6 T m.sup.3/kilogram cobalt, and a porosity
better than or equal to A04 B00 C00.
[0083] In regard to the ranges for the process parameters to make
Example 4, the sintering parameters and the hot isostatic pressing
parameters fall within the ranges set forth above for Example
1.
[0084] Referring to the material of the invention in general, in
regard to the relationship between the elements cobalt, chromium,
nickel and molybdenum, applicant contemplates that in one range the
cobalt will comprise between about 80 weight percent and about 95
weight percent of the sum of the cobalt, chromium, nickel and
molybdenum. The sum of the chromium, nickel and molybdenum will
comprise between about 5 weight percent and about 20 weight percent
of the sum of the cobalt, chromium, nickel and molybdenum. In
another ratio of the elements cobalt, chromium, nickel and
molybdenum, applicant contemplates that the cobalt will comprise
about 90 weight percent of the sum of the cobalt, chromium, nickel
and molybdenum and that the chromium, nickel and molybdenum will
comprise about 10 weight percent of the sum of the cobalt,
chromium, nickel and molybdenum.
[0085] In forming the consolidated body, it is important that the
chromium disassociated from the carbon in the chromium carbide
additive remains free in the cobalt binder alloy and does not
recombine with the carbon. This is because during the EDM process,
the free chromium combines with oxygen to form chromium oxide. The
chromium oxide is a protective layer that retards or eliminates the
electrolytic corrosion due to the EDM process. The chromium oxide
layer increases the passivity of the material.
[0086] In order to facilitate the presence of free chromium and
reduce the possibility that the chromium will recombine with the
carbon, tungsten (in addition to the tungsten in the tungsten
carbide) is added to the starting powder mixture. At least some of
this additional tungsten metal is present in the binder and
combines with the disassociated carbon from the chromium carbide to
eliminate free carbon that could combine with the chromium. There
does not appear to be any free carbon in the binder. The presence
of tungsten in the cobalt binder is measured by the magnetic
saturation of the tungsten carbide-cobalt alloy. It has been found
that the magnetic saturation should be between about 75 percent and
about 90 percent wherein 100 percent is equal to
201.times.10.sup.-6 T m.sup.3/kilogram cobalt, i.e., the magnetic
saturation should range between about to 151.times.10.sup.-6 T
m.sup.3/kilogram cobalt and about to 182.times.10.sup.-6 T
m.sup.3/kilogram cobalt. See Santhanam et al., "Cemented Carbides",
Metals Handbook, Volume 16, 9.sup.th Edition, (1989), Machining ASM
International, pages 71-89.
[0087] It is preferred that eta (.eta.) phase (i.e., double
carbides such as CO.sub.3W.sub.3C and CO.sub.6W.sub.6C) not be
present in the material.
[0088] The presence of molybdenum on the consolidated cemented
carbide blank improves the resistance of the consolidated blank to
pitting due to electrochemical corrosion. The presence of
molybdenum on the consolidated cemented carbide blank improves the
toughness of the consolidated blank.
[0089] It can thus be seen that applicant has invented a new and
useful cemented carbide blank, as well as a cemented carbide body
made from the cemented carbide blank by an EDM process. The
cemented carbide blank of the invention provides a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not contain exotic elements additives (i.e., Re, Ge, Ga, Ir,
Os, Pd, Ag, Au, Pt, Te, Rh, and Ru) as additives and is suitable
for EDM without suffering, or at least reduces, "pitting" or any
significant "pitting" as a result of the EDM process. The cemented
carbide blank of the invention also provides a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not contain exotic elements additives (i.e., Re, Ge, Ga, Ir,
Os, Pd, Ag, Au, Pt, Te, Rh, and Ru) as additives and does not
suffer any, or at least reduces, pitting or loss of binder in the
surface region underneath the surface of the body as a result of an
EDM process. The cemented carbide blank of the invention also
provides a cemented carbide (e.g., tungsten carbide-based material
that contains cobalt) that does not contain exotic elements
additives (i.e., Re, Ge, Ga, Ir, Os, Pd, Ag, Au, Pt, Te, Rh, and
Ru) as additives and does not suffer any, or at least reduces,
cracking at the surface as a result of an EDM process. Finally, the
cemented carbide blank of the invention provides a cemented carbide
(e.g., tungsten carbide-based material that contains cobalt) that
does not contain exotic elements additives (i.e., Re, Ge, Ga, Ir,
Os, Pd, Ag, Au, Pt, Te, Rh, and Ru) as additives and does not
experience a significant reduction in strength as a result of an
EDM process.
[0090] The patents and other documents identified herein are hereby
incorporated by reference herein. Other embodiments of the
invention will be apparent to those skilled in the art from a
consideration of the specification or a practice of the invention
disclosed herein. It is intended that the specification and
examples are illustrative only and are not intended to be limiting
on the scope of the invention. The true scope and spirit of the
invention is indicated by the following claims.
* * * * *