U.S. patent number RE34,180 [Application Number 07/243,089] was granted by the patent office on 1993-02-16 for preferentially binder enriched cemented carbide bodies and method of manufacture.
This patent grant is currently assigned to Kennametal Inc.. Invention is credited to George P. Grab, Bela J. Nemeth, deceased.
United States Patent |
RE34,180 |
Nemeth, deceased , et
al. |
February 16, 1993 |
**Please see images for:
( Certificate of Correction ) ** |
Preferentially binder enriched cemented carbide bodies and method
of manufacture
Abstract
Cemented carbide substrates having substantially A or B type
porosity and a binder enriched layer near its surface are
described. A refractory oxide, nitride, boride, and/or carbide
coating is deposited on the binder enriched surface of the
substrate. Binder enrichment is achieved by incorporating Group IVB
or VB transition elements. These elements can be added as the
metal, the metal hydride, nitride or carbonitride.
Inventors: |
Nemeth, deceased; Bela J. (late
of Greensburg, PA), Grab; George P. (Greensburg, PA) |
Assignee: |
Kennametal Inc. (Latrobe,
PA)
|
Family
ID: |
26935585 |
Appl.
No.: |
07/243,089 |
Filed: |
September 9, 1988 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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248465 |
Mar 27, 1981 |
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Reissue of: |
587584 |
Mar 8, 1984 |
04610931 |
Sep 9, 1986 |
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Current U.S.
Class: |
428/547; 419/14;
419/16; 419/45; 419/55; 419/60; 428/552; 428/565; 75/238; 75/241;
75/242 |
Current CPC
Class: |
C22C
29/08 (20130101); C23C 30/005 (20130101); B22F
2998/00 (20130101); B22F 2998/00 (20130101); B22F
2207/03 (20130101); Y10T 428/12146 (20150115); Y10T
428/12056 (20150115); Y10T 428/12021 (20150115) |
Current International
Class: |
C22C
29/08 (20060101); C22C 29/06 (20060101); C23C
30/00 (20060101); B22F 003/16 (); B22F
007/02 () |
Field of
Search: |
;428/547,551,565,610,552
;75/201,203,204,28R,241,242,240,238,239 ;148/126
;419/18,15,16,45,47,14,13,55,60 |
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1544436 |
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Apr 1979 |
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GB |
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1593326 |
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Jul 1981 |
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GB |
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.
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.
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|
Primary Examiner: Zimmerman; John
Attorney, Agent or Firm: Prizzi; John J. Belsheim; Stephen
T.
Parent Case Text
This is a continuation of application Ser. No. 248,465, filed Mar.
27, 1981, now abandoned.
Claims
What is claimed is:
1. A cemented carbide body formed by sintering a substantially
homogeneous mixture of constituents comprising: a least 70 weight
percent tungsten carbide; a metallic binder; a .[.metal.].
.Iadd.second .Iaddend.carbide selected from the group consisting of
the Group IVB and VB transition metal carbides; said metal carbide
being present in an amount less than the amount of tungsten
carbide; said body having substantially A to B type porosity
throughout said body; said metal carbide combined with said
tungsten carbide forming a solid solution carbide; a .Iadd.first
.Iaddend.layer of .Iadd.binder enriched and .Iaddend.at least
partially solid solution carbide depleted material .[.near.].
.Iadd.beginning at and extending inwardly from .Iaddend.a
peripheral surface of said body.Iadd., the content of said binder
present in the first layer reaching between about 150 percent and
about 300 percent of the average binder content of the cemented
carbide body; and a hard dense refractory coating bonded to the
peripheral surface of the cemented carbide body.Iaddend..
2. A cemented carbide body according to claim 1 wherein said binder
is selected from the group consisting of cobalt, nickel, iron and
their alloys. .[.3. A cemented carbide body formed by sintering a
substantially homogeneous mixture of constituents comprising: at
least 70 weight percent tungsten carbide; a cobalt binder alloy; a
metal carbide selected from the group consisting of the Group IVB
and VB transition metal carbides; said metal carbide combined with
said tungsten carbide forming a solid solution carbide; a layer of
at least partially solid solution depleted material near a
peripheral surface of said body; and wherein said cobalt binder
alloy has an overall magnetic saturation value of less than 158
gauss-cm.sup.3 /gm cobalt..]. .[.4. A cemented carbide body
according to claim 3 wherein said cobalt binder alloy has an
overall magnetic saturation value of approximately 145 to 157
gauss-cm.sup.3 /gm cobalt..]. .[.5. A cemented carbide body
according to claim 3 wherein said cobalt binder alloy has an
overall magnetic saturation value of less than 126
gauss-cm.sup.3 /gm cobalt..]. 6. A cemented carbide body
comprising: at least 70 weight percent .[.tugnsten.].
.Iadd.tungsten .Iaddend.carbide; cobalt; a metal carbide selected
from the group consisting of the Group IVB and VB transition metal
carbides; a layer of cobalt enrichment near a peripheral surface of
said body; said body having substantially A to B type porosity
throughout .Iadd.and wherein the cobalt enriched layer has a cobalt
content at said peripheral surface equal to 1.5 to 3 times the
average cobalt content of the body.Iaddend.. 7. The cemented
carbide, body according to claim 6 wherein the level of said
transition metal carbide in
said layer of cobalt enrichment is at least partially depleted. 8.
A cemented carbide body according to claims 6 or 7 wherein said
metal carbide is selected from the group consisting of titanium
.Iadd.carbide.Iaddend., hafnium .Iadd.carbide.Iaddend.,
tantalum
.Iadd.carbide ep and niobium .Iadd.carbide.Iaddend.. 9. A cemented
carbide body according to claims 6 or 7 wherein said metal carbide
is present at
the level of at least 0.5 weight percent. 10. A cemented carbide
body according to claim 8 wherein said metal carbide is present at
the level of
at least 0.5 weight percent. .[.11. A cemented carbide body
according to claims 6 or 7 wherein the cobalt enriched layer has a
cobalt content at said peripheral surface equal to 1.5 to 3 times
the average cobalt content of the body..]. .[.12. A cemented
carbide body according to claim 6 wherein the cobalt enriched layer
extends inwardly from said peripheral surface of said body to a
minimum depth of substantially 6 microns..].
A cemented carbide body according to claim .[.11.]. .Iadd.6
.Iaddend.wherein the cobalt enriched layer extends inwardly from
said peripheral surface of said body to a minimum depth of
substantially 6 microns. .[.14. A cemented carbide body according
to claim 12 wherein the cobalt enriched layer extends inwardly from
said peripheral surface of
said body to a depth of 12 to 50 microns..]. 15. A cemented carbide
body according to claim 13 wherein the cobalt enriched layer
extends inwardly from said peripheral surface of said body to a
depth of 12 to 50 microns.
6. A cemented carbide body accoring to .[.claims 6 or 14.].
.Iadd.claim 6.Iaddend., wherein said peripheral surface of said
body comprises a rake face; said rake face joined to a flank face;
a cutting edge located at the junction of said rake and flank
faces; and wherein said enriched layer
extends inwardly from said rake face. 17. A cemented carbide body
according to claim 16 further comprising a hard dense refractory
coating bonded to said peripheral surface of said body, and said
coating having
one or more layers. 18. The cemented carbide body according to
claim .[.17.]. .Iadd.100 .Iaddend.wherein the material comprising
said layer is selected from the group consisting of the carbides,
nitrides, borides and carbonitrides of titanium, zirconium,
hafnium, niobium, tantalum,
vanadium, and the oxide and oxynitride of aluminum. 19. The
cemented carbide body according to claim .[.17.]. wherein said
coating comprises a
layer of titanium carbide. 20. The cemented carbide body according
to claim .[.17.]. .Iadd.100 .Iaddend.wherein said coating comprises
a layer
of titanium carbonitride. 21. The cemented carbide body according
to claim .[.17.]. .Iadd.100 .Iaddend.wherein said coating comprises
a layer of
titanium carbide and a layer of titanium nitride. 22. The cemented
carbide body according to claim 21 wherein said coating further
comprises a layer
of titanium carbonitride. 23. The cemented carbide body according
to claim .[.17.]. .Iadd.100 .Iaddend.wherein said coating comprises
a layer of
aluminum oxide. 24. The cemented carbide body according to claim
23
wherein said coating further comprises a layer of titanium carbide.
25. The product prepared by the process of forming a binder
enriched layer near a peripheral surface of a substantially A to B
type porosity cemented carbide body, in which said process
comprises: milling and blending a first carbide powder, a binder
alloy powder and a chemical agent powder selected from the group
consisting of metals, alloys, nitrides and carbonitrides of Group
IVB and VB transition metals; pressing a compact utilizing said
powders; sintering said compact at a temperature above the binder
alloy melting temperature so as to transform, at least partially,
the chemical agent to a carbide in the layer to be binder enriched;
removing said binder enriched layer in selected areas of said
product; resintering said compact at a temperature above the binder
alloy melting temperatures so as to transform, at least partially,
the chemical agent to a carbide in the layer near the peripheral
surface of the selected area of
the product. 26. The product of claim 25 further comprising the
step of: depositing on said peripheral surface of the product an
adherent hard wear
resistant refractory coating having one or more layers. 27. The
product of claim 26 wherein the material comprising each of said
layers is selected from the group consisting of the carbides,
nitrides and carbonitrides of titanium, zirconium, hafnium,
niobium, tantalum and vanadium, and the
oxide and oxynitride of aluminum. 28. The product of claim 25
wherein said first carbide powder comprises tungsten carbide and
said tungsten carbide
comprises at least 70 weight percent of the product. 29. The
product according to claim 28 wherein said binder is selected from
the group
consisting of cobalt, nickel, iron and their alloys. 30. A process
for forming a cobalt binder enriched layer near a peripheral
surface of a substantially A type porosity cemented carbide body,
said process comprising the steps of: milling and blending powders
comprising tungsten carbide, cobalt and a metal compound selected
from the group consisting of nitrides, and carbonitrides of Group
IVB and VB transition metals.Iadd., and the adding of free carbon
as during milling and blending in an amount sufficient to produce a
tungsten lean cobalt binder in the sintered compact.Iaddend.;
pressing a compact utilizing said powders; sintering said compact
at a temperature above the melting temperature of said binder so as
to transform, at least partially, the metal compound to a metal
carbide in the layer to be binder enriched.Iadd.; and removing said
binder enriched layer in selected areas of said peripheral
surface.Iaddend.. .[.31. The process according to claims 30 further
comprising the step of: removing said binder enriched layer in
selected areas of said peripheral
surface..]. 32. The process according to claim 30 further
comprising the step of: depositing on said peripheral surface an
adherent hard wear resistant coating having one or more layers
wherein the material comprising each of said layers is selected
from the group consisting of the carbides, nitrides, borides and
carbonitrides of titanium, zirconium, hafnium, niobium, tantalum
and vanadium, and the oxide and the oxynitride
of aluminum. 33. The process according to claim 30 wherein said
powders further comprise a second carbide powder selected from the
group consisting of the Group IVB and VB metal carbides and their
solid
solutions. 34. The process according to claim 30 further comprising
the step of at least partially volatilizing an element selected
from the group
consisting of hydrogen and nitrogen during the sintering step.
.[.35. The process according to claim 31 further comprising the
addition of free carbon as during milling and blending in an amount
sufficient to produce a
tungsten lean cobalt binder in the sintered compact..]. .Iadd.36.
The cemented carbide body according to claim 1 wherein said binder
is present
in an amount up to about 10 weight percent. .Iaddend. .Iadd.37. A
cemented carbide body according to claim 1 further including
nitrogen present as a carbonitride in a solid solution of said
tungsten and second carbide. .Iaddend. .Iadd.38. A cemented carbide
body according to claim 37 wherein said carbonitride is a tungsten
titanium carbonitride. .Iaddend.
.Iadd.39. A cemented carbide body according to claim 1 wherein said
second carbide is present at the level of at least 0.5 weight
percent.
.Iaddend. .Iadd.40. A cemented carbide body according to claim 1
wherein said second carbide is present in an amount between 0.5 and
2 weight
percent. .Iaddend. .Iadd.41. The cemented carbide body according to
claim 1 further including a second layer of partial metallic binder
depletion beneath and separate from said first layer. .Iaddend.
.Iadd.42. The cemented carbide body according to claim 41 wherein
the bulk substrate is beneath said second layer. .Iaddend.
.Iadd.43. The cemented carbide body according to claim 1 wherein
said first layer extends inwardly from the peripheral surface a
distance between about 12 microns to about 50 microns. .Iaddend.
.Iadd.44. The cemented carbide body according to claim 1 wherein
the first layer extends inwardly from the peripheral surface a
distance between about 6 and about 125 microns. .Iaddend. .Iadd.45.
The cemented carbide body according to claim 1 wherein said second
carbide is a cubic carbide selected from the group consisting of
tantalum carbide, niobium carbide, titanium carbide, vanadium
carbide, hafnium carbide and zirconium carbide. .Iaddend. .Iadd.46.
The cemented carbide body according to claim 45 wherein the
metallic binder is cobalt, and the cobalt is present in an amount
between about 5 and 10 weight percent. .Iaddend. .Iadd.47. The
cemented carbide body according to claim 46 wherein the cubic
carbide content is not greater than about 20 weight percent.
.Iaddend. .Iadd.48. The cemented carbide body according to claim 1
wherein the binder is cobalt, and the first layer has a cobalt
content between about 1.75 and about 3.0 times the average cobalt
content of the
cemented carbide body. .Iaddend. .Iadd.49. The cemented carbide
body according to claim 1 wherein said metallic binder is cobalt
and said cobalt is present as a cobalt binder alloy, and said
cobalt binder alloy has an overall magnetic saturation value of
between approximately 145 to
approximately 157 gauss-cm.sup.-3 /gm cobalt. .Iaddend. .Iadd.50.
The cemented carbide body according to claim 1 wherein the first
layer has a binder content between about 2.0 and about 3.0 times
the average binder
content of the cemented carbide body. .Iaddend. .Iadd.51. The
cemented carbide body according to claim 1 wherein said binder is
cobalt and the cobalt is present in said body as a cobalt alloy,
and said cobalt alloy has an overall magnetic saturation value of
less than 158 gauss-cm.sup.-3
/gm cobalt. .Iaddend. .Iadd.52. A cemented carbide body according
to claim 6 wherein the cobalt enriched layer has a cobalt content
reaching between about 1.75 and about 3.0 times the average cobalt
content of the body. .Iaddend. .Iadd.53. A cemented carbide body
according to claim 6 wherein the cobalt enriched layer has a cobalt
content reaching between about 2.0 and about 3.0 times the average
cobalt content of the body.
.Iaddend. .Iadd.54. The cemented carbide body according to claim 6
wherein said cobalt is present as a cobalt binder alloy having an
overall magnetic saturation value of less than 158 gauss-cm.sup.-3
/gm cobalt and
at least gauss-cm.sup.3 /gm cobalt. .Iaddend. .Iadd.55. The product
of claim 25 wherein in said cemented carbide body said binder alloy
is a cobalt alloy, and said cobalt alloy has an overall magnetic
saturation value of between approximately 145 to approximately 157
gauss-cm.sup.-3
/gm cobalt. .Iaddend. .Iadd.56. A coated cemented carbide cutting
insert comprising:
a cemented carbide body configured so as to present a rake face
joined to a flank face, a cutting edge located at the juncture of
the rake and flank faces;
said cemented carbide body formed by sintering a substantially
homogenous mixture of constituents, the body comprising:
at least 70 weight percent of tungsten carbide;
between about 3 weight percent and about 10 weight percent of
cobalt;
a solid solution of tungsten carbide and a carbide of a second
metal, the second metal selected from the group consisting of
titanium, hafnium, tantalum and niobium;
a zone of cobalt enrichment being at and extending inwardly from
the peripheral surface of the rake face wherein the zone of cobalt
enrichment has a cobalt content equal to about 1.5 to about 3 times
the average cobalt content of the cemented carbide body, cobalt
enrichment being absent from the flank face, said cobalt being
present as a cobalt binder alloy wherein said cobalt binder alloy
has an overall magnetic saturation value of less than 158
gauss-cm.sup.3 /gm cobalt; and
a hard dense refractory coating bonded to the peripheral surfaces
of said cemented carbide body including the peripheral surfaces of
the rake and flank faces, and said coating having one or more
layers. .Iaddend.
.Iadd. . The cutting insert according to claim 56 wherein said
coating comprises a layer of titanium carbide. .Iaddend. .Iadd.58.
The cutting insert according to claim 56 wherein said coating
comprises a layer of titanium carbonitride. .Iaddend. .Iadd.59. The
cutting insert according to claim 56 wherein said coating comprises
a layer of titanium nitride. .Iaddend. .Iadd.60. The cutting insert
according to claim 56 wherein said coating comprises a layer of
aluminum oxide. .Iaddend. .Iadd.61. The cutting insert according to
claim 56 wherein the zone of cobalt enrichment further exhibits
solid solution carbide depletion to some degree. .Iaddend.
.Iadd.62. The cutting insert according to claim 61 wherein the
cemented carbide body exhibits an absence of solid solution carbide
depletion from the flank face. .Iaddend. .Iadd.63. The cutting
insert according to claim 56 wherein the cemented carbide body
includes a zone of cobalt depletion to some degree and solid
solution enrichment beneath the
zone of cobalt enrichment. .Iaddend. .Iadd.64. The cutting insert
according to claim 56 wherein the cobalt enriched zone extends
inwardly from the peripheral surface of the rake face to a minimum
depth of approximately 6 microns. .Iaddend. .Iadd.65. The cutting
insert according to claim 56 further including nitrogen present as
a carbonitride in a solid solution of the tungsten carbide and
second metal carbide. .Iaddend.
.Iadd.66. The cutting insert according to claim 56 wherein said
cobalt binder alloy has an overall magnetic saturation value of
between approximately 145 to approximately 157 gauss-cm.sup.3 /gm
cobalt.
.Iaddend. .Iadd.67. The cutting insert according to claim 56
wherein the zone of cobalt enrichment reaches a level of between
about 175 percent and about 300 percent of the average cobalt
content of the cemented carbide body. .Iaddend. .Iadd.68. The
cutting insert according to claim 56 wherein the zone of cobalt
enrichment reaches a level of between about 200 percent and about
300 percent of the average cobalt content of the cemented
carbide body. .Iaddend. .Iadd.69. The coated cemented carbide
cutting insert according to claim 56 wherein said cobalt binder
alloy has an overall magnetic saturation value of less than 158
gauss-cm.sup.3 /gm
cobalt and at least 139 gauss-cm.sup.3 /gm cobalt. .Iaddend.
.Iadd.70. A process for forming a cobalt enriched layer at a
peripheral surface of a cemented carbide body, said process
comprising the steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount between about 3 and about 10 weight
percent of cobalt, and an amount greater than approximately 0.5
weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of transition metals
whose carbides have a free energy of formation more negative than
said first carbide at a temperature above the binder carbon
eutectic;
densifying said compact;
transforming, at least partially, said chemical agent to a solid
solution with said first carbide by a heat treatment; and
increasing the cobalt content at said peripheral surface during
said heat treatment resulting in the cemented carbide body having a
cobalt enriched layer beginning at and extending inwardly from the
peripheral surface wherein the cobalt content in the cobalt
enriched layer is between about 150 percent and about 300 percent
of the average cobalt content of the cemented carbide body, and the
cobalt being present as a cobalt binder alloy wherein the cobalt
binder alloy has a magnetic saturation value of
less than 158 gauss-cm.sup.3 /gm cobalt. .Iaddend. .Iadd.71. The
process according to claim 70 wherein the chemical agent is present
in an amount
between 0.5 and 2 weight percent. .Iaddend. .Iadd.72. The process
according to claim 70 whereim the chemical agent is titanium
nitride. .Iaddend. .Iadd.73. The process according to claim 70,
wherein the
chemical agent is titanium carbonitride. .Iaddend. .Iadd.74. The
process according to claim 70 wherein said cobalt binder alloy has
an overall magnetic saturation value of between approximately 145
to approximately
157 gauss-cm.sup.-3 /gm cobalt. .Iaddend. .Iadd.75. The process
according to claim 70 wherein said cobalt binder alloy has an
overall magnetic saturation value of less than 158 gauss-cm.sup.-3
/gm cobalt and at least
139 gauss-cm.sup.3 /gm cobalt. .Iaddend. .Iadd.76. A process for
forming a binder enriched layer near a peripheral surface of a
cemented carbide body, said process comprising the steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount between about 3 and about 10 weight
percent of a binder metal, and an amount greater than approximately
0.5 weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of transition metals
whose carbides have a free energy of formation more negative than
said first carbide at a temperature above the binder carbon
eutectic:
densifying said compact;
transforming, at least partially, said chemical agent to a solid
solution with said first carbide by a first heat treatment;
increasing the binder content near said peripheral surface during
said first heat treatment;
removing the zone of increased binder content from at least a
portion of the peripheral surface of the body;
subjecting the cemented carbide body to a second heat treatment so
as to increase the binder content near the portion of the
peripheral surface
previously removed. .Iaddend. .Iadd.77. The process according to
claim 76 further including the step of applying a hard dense
refractory coating to
the body. .Iaddend. .Iadd.78. A process for fabricating a cutting
insert said process comprising the steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount not greater than about 10 weight percent
of a binder metal, and an amount greater than approximately 0.5
weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of transition metals
whose carbides have a free energy of formation more negative than
said first carbide at a temperature above the binder carbon
eutectic;
densifying said compact into a configuration presenting a rake face
joined to a flank face wherein a cutting edge is located at the
juncture of the rake and flank faces;
transforming, at least partially, said chemical agent to solid
solution with said first carbide by a first heat treatment while
maintaining some nitrogen in the form of a nitride or carbonitride
as a constituent of the compact;
increasing the binder content near said peripheral surface of the
rake and flank faces during said first heat treatment;
removing the binder enriched layer from at least one portion of the
peripheral surface of the compact;
subjecting the compact to a second heat treatment so as to increase
the binder content near the one portion of the peripheral surface
of the compact; and
depositing on said peripheral surface of the cemented carbide body
an adherent hard wear resistant coating having one or more layers
wherein the material comprising each of said layers is selected
from the group consisting of the carbides, nitrides, borides and
carbonitrides of titanium, zirconium, hafnium, niobium, tantalum
and vanadium, and the
oxide and the oxynitride of aluminum. .Iadd.79. The process
according to claim 78 wherein the chemical agent is present in an
amount between 0.5 and 2 weight percent. .Iaddend. .Iadd.80. The
process according to claim 78 wherein a portion of the nitrogen
present in the compact prior to the first heat treatment is
volatilized during the first heat treatment.
.Iaddend. .Iadd.81. The process according to claim 80 wherein a
portion of the nitrogen present in the compact after the first heat
treatment and prior to the second heat treatment is volatilized
during the second heat treatment. .Iaddend. .Iadd.82. The process
according to claim 78 wherein the first and second heat treatments
occur at a temperature over the melting point of the binder metal.
.Iaddend. .Iadd.83. The process according to claim 78 wherein the
transition metals include titanium, tantalum, hafnium and niobium.
.Iaddend. .Iadd.84. The process according to claim 78 further
comprising the addition of free carbon as during milling and
blending in an amount sufficient to produce a tungsten lean
cobalt binder in the sintered compact. .Iaddend. .Iadd.85. The
process according to claim 84 wherein one-half mole of the free
carbon is added
per mole of starting nitrogen. .Iaddend. .Iadd.86. The process
according to claim 78 wherein the chemical agent is titanium
nitride. .Iaddend. .Iadd.87. The process according to claim 78
wherein the binder enrichment is removed from an area adjacent the
peripheral surface of the flank face after the first heat treatment
and before the second heat treatment.
.Iaddend. .Iadd.88. A process for fabricating a coated cemented
carbide cutting insert, said process comprising the steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount of binder metal not greater than about
10 weight percent; and an amount between approximately 0.5 and 2
weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of the Group IVB and
VB transition metals;
densifying said compact into a configuration presenting a rake face
joined to a flank face wherein a cutting edge is located at the
juncture of the rake and flank faces;
liquid phase sintering the configured compact in an atmosphere
having the nitrogen vapor pressure below its equilibrium pressure
so as to transform, at least partially, said chemical agent to
solid solution with said first carbide while maintaining some
nitrogen in the form of a nitride or carbonitride as a constituent
of the compact;
increasing the binder content of the compact in a zone near the
peripheral surface of the rake and flank faces during the liquid
phase sintering;
removing the binder enriched zone from at least one portion of the
peripheral surface of the compact;
subjecting the compact to a heat treatment in an atmosphere having
the nitrogen vapor pressure below its equilibrium vapor pressure so
as to increase the binder content near the one portion of the
peripheral surface of the compact; and
depositing on said peripheral surface of the cemented carbide
compact an adherent hard wear resistant coating having one or more
layers wherein the material comprising each of said layers is
selected from the group consisting of the carbides, nitrides
borides and carbonitrides of titanium, zirconium, hafnium, niobium,
tantalum and vanadium, and the oxide and the oxynitride of
aluminum. .Iaddend. .Iadd.89. The process according to claim 88
wherein the pressure during the liquid phase sintering and the heat
treatment is between about 0.1 and about 0.15 torr. .Iaddend.
.Iadd.90. A cemented carbide body of substantially A to B porosity
and having a binder enriched zone at the peripheral surface of the
body produced by a process comprising the steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount between about 3 and about 10 weight
percent of a binder metal, and an amount greater than approximately
0.5 weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of transition metals
whose carbides have a free energy of formation more negative than
said first carbide at a temperature above the binder carbon
eutectic;
densifying said compact;
transforming, at least partially, said chemical agent to a solid
solution with said first carbide by a heat treatment; and
increasing the binder content in a zone at said peripheral surface
during said heat treatment wherein the level of cobalt in the zone
is between about 175 percent and about 300 percent of the average
cobalt content of
the cemented carbide body. .Iaddend. .Iadd.91. The cemented carbide
body according to claim 90 wherein the transforming step
includes:
liquid phase sintering the compact in an atmosphere wherein the
nitrogen partial pressure is below its equilibrium vapor pressure.
.Iaddend.
.Iadd. 2. The cemented carbide body according to claim 90 wherein
the level of binder in the zone reaches a level of between about
200 percent and about 300 percent of the average binder content of
the cemented
carbide body. .Iaddend. .Iadd.93. The cemented carbide body
according to claim 90 wherein said binder metal is cobalt and said
cobalt is present as a cobalt binder alloy, and said cobalt binder
alloy has an overall magnetic saturation value of less than 158
gauss-cm.sup.3 /gm cobalt and
at least 139 gauss-cm.sup.3 /gm cobalt. .Iaddend. .Iadd.94. A
cemented carbide body having a binder enriched zone near the
peripheral surface of the body produced by a process comprising the
steps of:
obtaining a compact having a substantially uniform distribution of
a first carbide, an amount between about 3 and about 10 weight
percent of a binder metal, and an amount greater than approximately
0.5 weight percent of a chemical agent selected from the group
consisting of the nitrides and carbonitrides of transition metals
whose carbides have a free energy of formation more negative than
said first carbide at a temperature above the binder carbon
eutectic;
densifying said compact;
transforming, at least partially, said chemical agent to a solid
solution with said first carbide by a first heat treatment
comprising liquid phase sintering the compact in an atmosphere
wherein the nitrogen partial pressure is below its equilibrium
vapor pressure;
increasing the binder content in a zone near said peripheral
surface during said first heat treatment;
removing the binder enriched zone at selected areas of the
peripheral surface; and
subjecting the compact to a second heat treatment in an atmosphere
wherein the nitrogen partial pressure is below its equilibrium
vapor pressure so as to increase the binder content near the
selected areas of the peripheral surface. .Iaddend. .Iadd.95. The
cemented carbide body according to claim 94 further comprising the
step of coating the peripheral surface of the cemented carbide body
with a hard dense refractory coating after the second heat
treatment. .Iaddend. .Iadd.96. The cemented carbide body according
to claim 94 further comprising the step of coating the peripheral
surface of the cemented carbide body with a hard dense refractory
coating. .Iaddend. .Iadd.97. A coated cemented carbide cutting
insert comprising:
a cemented carbide body configured so as to present a rake face
joined to a flank face, a cutting edge located at the juncture of
the rake and flank faces, the body comprising:
at least 70 weight percent tungsten carbide;
between about 3 weight percent and about 10 weight percent of
cobalt, said cobalt being present as a cobalt binder alloy, said
cobalt binder alloy having an overall magnetic saturation value
between about 145 and about 157 gauss-cm.sup.3 /gm cobalt;
a solid solution of tungsten carbide and a carbide of a second
metal wherein said second metal is selected from the group
consisting of titanium, hafnium, tantalum and niobium;
a zone of cobalt enrichment being at and extending inwardly from a
ground peripheral surface of a selected one of the faces, the
cobalt content in the zone of cobalt enrichment reaching between
about 150 percent and about 300 percent of the average cobalt
content of the cemented carbide body; and
a hard dense refractory coating bonded to the peripheral surface of
the
cemented carbide body. .Iaddend. .Iadd.98. The coated cemented
carbide cutting insert according to claim 97 wherein the rake face
has a ground
peripheral surface. .Iaddend. .Iadd.99. The coated cemented carbide
cutting insert of claim 97 wherein the cobalt content in the zone
of cobalt enrichment ranges between about 200 percent and about 300
percent of the average cobalt content of the cemented carbide body.
.Iaddend.
.Iadd.100. A cemented carbide body comprising at least 70 weight
percent tungsten carbide; cobalt; a metal carbide selected from the
group consisting of the Group IVB and VB transition metal carbides;
a layer of cobalt enrichment near a peripheral surface of said body
wherein the cobalt enriched layer extends inwardly from said
peripheral surface of said body to a depth of 12 to 50 microns and
wherein the cobalt content in the cobalt enriched layer reaches
between about 150 percent and about 300 percent of the average
cobalt content of the cemented carbide body; said body having
substantially A to B type porosity throughout; said peripheral
surface of said body comprises a rake face; said rake face joined
to a flank face; a cutting edge located at the juncture of said
rake and flank faces; and wherein said enriched layer extends
inwardly from said rake face; a hard dense refractory coating
bonded to said peripheral surface of said body, and said coating
having one or more layers. .Iaddend.
.Iadd. The cemented carbide body according to claim 100 wherein
said cobalt is present as a cobalt binder alloy which has an
overall magnetic saturation value of between approximately 145 to
approximately 157
gauss-cm.sup.-3 /gm cobalt. .Iaddend. .Iadd.102. The cemented
carbide body according to claim 100 wherein the cobalt content in
the cobalt enriched layer reaches a level between about 175 percent
and about 300 percent of the average cobalt content of the cemented
carbide body.
.Iaddend. .Iadd.103. The cemented carbide body according to claim
100 wherein the cobalt content in the cobalt enriched layer reaches
a level between about 200 percent and about 300 percent of the
average cobalt
content of the cemented carbide body. .Iaddend. .Iadd.104. The
cemented carbide body according to claim 100 wherein said cobalt is
present in a cobalt binder alloy having an overall magnetic
saturation value of less than 158 gauss-cm.sup.3 /gm cobalt and at
least 139 gauss-cm.sup.3 /gm
cobalt. .Iaddend. .Iadd.105. A cemented carbide body comprising: at
least 70 weight percent tungsten carbide; cobalt; a metal carbide
selected from the group consisting of the Group IVB and VB
transition metal carbides; a layer of cobalt enrichment near a
peripheral surface of said body wherein the level of cobalt
enrichment in the cobalt enriched layer reaches 150 to 300 percent
the average cobalt content of the body; said body having
substantially A to B type porosity throughout. .Iaddend. .Iadd.106.
The cemented carbide body according to claim 105 wherein said
cobalt is present as a cobalt binder alloy which has an overall
magnetic saturation value of between approximately 145 to
approximately 157 gauss-cm.sup.-3
/gm cobalt. .Iaddend. .Iadd.107. The cemented carbide body
according to claim 105 wherein said cobalt is present as a cobalt
binder alloy having an overall magnetic saturation value of less
than 158 gauss-cm.sup.3 /gm cobalt and at least 139 gauss-cm.sup.3
/gm cobalt. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention pertains to the fields of cemented carbide
parts, having cobalt, nickel, iron or their alloys as a binder
material, and the manufacture of these parts. More particularly,
the present invention pertains to cemented carbide metal cutting
inserts having a hard refractory oxide, nitride, boride, or carbide
coating on their surface.
In the past, various hard refractory coatings have been applied to
the surfaces of cemented carbide cutting inserts to improve the
wear resistance of the cutting edge and thereby increase the
cutting lifetime of the insert. See, for example, U.S. Pat. Nos.
4,035,541 (assigned to applicant corporation); 3,564,683;
3,616,506; 3,882,581; 3,914,473; 3,736,107; 3,967,035; 3,955,038;
3,836,392; and U.S. Pat. No. 29,420. These refractory coatings,
unfortunately, can reduce the toughness of cemented carbide inserts
to varying degrees. The degree of degradation depends at least in
part on the structure and composition of the coating and the
process used for is deposition. Therefore, while refractory
coatings have improved the wear resistance of metal cutting
inserts, they have not reduced the susceptibility of the cutting
edge to failure by chipping or breakage, especially in interrupted
cutting applications.
Previous efforts to improve toughness or edge strength in coated
cutting inserts revolved around the production of a cobalt enriched
layer extending inwardly from the substrate/coating interface. It
was found that cobalt enrichment of the surface layers in certain C
porosity substrates could be achieved during vacuum sintering
cycles. These cobalt enriched zones were characterized by A
porosity while most of the bulk of the substrate had C porosity.
Solid solution carbide depletion was usually present to varying
depths and degrees in the areas of cobalt enrichment. Cobalt
enrichment is desirable in that it is well known that increasing
cobalt content will increase the toughness or impact resistance of
cemented carbides. Unfortunately, the level of enrichment produced
is difficult to control in C porosity substrates. Typically, a
coating of cobalt and carbon was formed on the surface of the
substrate. This coating of cobalt and carbon was removed prior to
deposition of the refractory material on the substrate, in order to
obtain adherent bonding between the coating and substrate. At
times, the level of cobalt enrichment in the layers beneath the
surface of the substrate was so high that it had an adverse effect
on flank wear. As a result, sometimes the layer of cobalt
enrichment on the flank faces of the substrate were ground away
leaving cobalt enrichment only on the rake faces and the
possibility of C porosity material on the flank face. In comparison
with A or B type porosity substrates, C porosity substrates are not
as chemically homogeneous. This can result in less control over the
formation of cia phase at the coating substrate interface (a hard
and brittle phase affecting toughness), a reduction in coating
adherency and an increase in nonuniform coating growth.
By way of definition, the porosity observed in cemented carbides
may be classified into one of three categories recommended by the
ASTM (American Society for Testing and Materials) as follows:
Type A for pore sizes less than 10 microns in diameter.
Type B for pore sizes between 10 microns and 40 microns in
diameter.
Type C for irregular pores caused by the presence of carbon
inclusions. These inclusions are pulled out of the sample during
metallographic preparation leaving the aforementioned irregular
pores.
In addition to the above classifications, the porosity observed can
be assigned a number ranging for 1 through 6 to indicate the degree
of frequency of porosity observed. The method of making these
classifications can be found in Cemented Carbides by Dr. P.
Schwarzkopf and Dr. R. Kieffer, published by the MacMillan Co., New
York, (1960) at Pages 116 to 120.
Cemented carbides may also be classified according to their binder
carbon and tungsten contents. Tungsten carbide-cobalt alloys having
excess carbon are characterized by C porosity which, as already
mentioned, are actual free carbon inclusions. Tungsten
carbide-cobalt alloys low in carbon and in which the cobalt is
saturated with tungsten are characterized by the presence of eta
phase, a M.sub.12 C or M.sub.6 C carbide, where M represents cobalt
and tungsten. In between the extremes of C porosity and eta phase,
there is a region of intermediate binder alloy compositions which
contain tungsten and carbon in solution to varying levels, but such
that no free carbon or eta phase are present. The tungsten level
present in tungsten carbide cobalt alloys can also be characterized
by the magnetic saturation of the binder alloy, since the magnetic
saturation of the cobalt alloy is a function of its composition.
Carbon saturated cobalt is reported to have a magnetic saturation
of 158 gauss-cm.sup.3 /gm cobalt and is indicative of C type
porosity, while a magnetic saturation of 125 gauss-cm.sup.3 /gm
cobalt and below indicates the presence of eta phase.
It is, therefore, an object of the present invention to provide a
readily controllable and economic process for producing a binder
enriched layer near the surface of a cemented carbide body.
It is a further object of this invention to provide a cemented
carbide body having a binder enriched layer near its surface with
substantially all porosity throughout the body being of the A or B
types.
It is also an object of this invention to provide cemented carbide
bodies having carbon levels ranging from C porosity to eta phase
with a binder enriched layer near their peripheral surface.
It is an additional object of this invention to combine the
aforementioned cemented carbide bodies according to the present
invention with a refractory coating so as to provide coated cutting
inserts having a combination of high wear resistance and high
toughness.
These and other objects of the present invention will become more
fully apparent upon review of the following description of the
invention.
BRIEF SUMMARY OF THE INVENTION
According to the present invention, it has been found that a binder
enriched layer can be formed near a peripheral surface of a
cemented carbide body through the use of the following process:
Milling and blending a first carbide powder, a binder powder, and a
chemical agent powder selected from the group of metals, alloys,
hydrides, nitrides and carbonitrides of transition elements
.[.whoe.]. .Iadd.whose .Iaddend.carbides have a free energy of
formation more negative than that of the first carbide near the
binder melting point; and then, sintering or subsequently heat
treating a compact of the blended material so as to at least
partially transform the chemical agent to its carbide.
In accordance with the present invention, this process may be used
to produce a layer of binder enrichment near a peripheral surface
of a cemented carbide body, preferably, having substantially only A
to B type porosity throughout said body. Enrichment can also be
achieved in cemented carbide bodies having carbon levels ranging
from eta phase to C porosity.
Cemented carbide bodies in accordance with the present invention
have also been found to have a layer beneath said binder enriched
layer which is partially binder depleted.
Preferably, the first carbide is tungsten carbide. Preferably, the
binder alloy may be cobalt, nickel, iron or their alloys, but is,
most preferably, cobalt.
Preferably, the chemical agent is selected from the hydrides,
nitrides, and carbonitrides of the Group IVB and VB elements and
is, preferably, added in a small but effective amount, most
preferably, 0.5 to 2 weight percent of the powder charge. Most
preferably, the chemical agent is titanium nitride or titanium
carbonitride.
Cemented carbide bodies in accordance with the present invention
have also been found to have a layer, at least partially depleted
in solid solution carbide, near a peripheral surface of the body.
Cemented carbide bodies in accordance with the present invention
have also been found to have a layer beneath said depleted solid
solution layer which is enriched in solid solution carbides.
The cemented carbide bodies according to the present invention,
preferably, have a cutting edge at the juncture of a rake face and
a flank face with a hard dense refractory coating adherently bonded
to these faces. The binder enriched layer may be ground off the
flank face prior to coating.
The refractory coating is preferably composed of one or more layers
of a metal oxide, carbide, nitride, boride or carbonitride.
BRIEF DESCRIPTION OF THE DRAWINGS
The exact nature of the present invention will become more clearly
apparent upon reference to the following detailed specification,
reviewed in conjunction with the accompanying drawings, in
which:
FIG. 1 is a schematic, cross section through an embodiment of a
coated metal cutting insert according to the present invention.
FIG. 2 is a graphical representation of the typical levels of
cobalt enrichment produced in a cemented carbide body according to
the present invention as a function of depth below its rake
surfaces.
FIG. 3 is a graphical representation of the variation in binder and
solid solution carbides relative concentrations as a function of
depth below the rake surface in an Example 12 sample.
DETAILED DESCRIPTION OF THE INVENTION
The aformentioned objects of the invention are achieved through the
heat treatment of a cemented carbide compact containing an element
having a carbide with a more negative free energy of formation than
that of tungsten carbide at an elevated temperature close to or
above the binder melting point. For cutting insert applications,
this element or chemical agent can be selected from Group IVB and
VB transition metals, their alloys, nitrides, carbonitrides and
hydrides. It has been found that the layer of material adjacent to
the periphery of cemented tungsten carbide body can be consistently
binder enriched and, usually, at least partially solid solution
carbide depleted during sintering or reheating at a temperature
above the melting point of the binder alloy by incorporating Group
IVB and VB nitride, hydride and/or carbonitride additions to the
powder charge.
During sintering, these Group IVB and VB additions react with
carbon to form a carbide or carbonitride. These carbides or
carbonitrides may be present partially or wholly in a solid
solution with tungsten carbide and any other carbides present. The
level of nitrogen present in the final sintered carbide is
typically reduced from the level of nitrogen added as a nitride or
carbonitride since these additions are unstable at elevated
temperatures above and below the binder alloy melting point and
will lead to at least partial volatization of nitrogen from the
sample if the sintering atmosphere contains a concentration of
nitrogen less than its equilibrium vapor pressure. If the chemical
agent is added as a metal, alloy or hydride, it will also be
transformed to a cubic carbide, typically in solid solution with
the tungsten carbide and any other carbides present. The hydrogen
in any hydride added is volatilized during sintering.
The metals, hydrides, nitrides and carbonitrides of tantalum,
titanium, niobium, hafnium can be used alone or in combination to
promote consistent cobalt enrichment via sintering or subsequent
heat treating of tungsten carbide-cobalt base alloys having a wide
range of carbon. Additions totaling up to approximately 15 weight
percent have been found to be useful. It is believed that the
metals, nitrides, carbonitrides and hydrides of zirconium and
vanadium are also suitable for this purpose. In A and B porosity
alloys and carbon deficient alloys containing eta phase, cobalt
enrichment occurs without peripheral cobalt or carbon capping, thus
eliminating the need to remove excess cobalt and carbon from the
cemented carbide surfaces prior to refractory coating.
Additions of approximately 0.5 to 2 weight percent, especially of
titanium in the form of titanium nitride or titanium carbonitride,
to tungsten carbide-cobalt base alloys are preferred. Since
titanium nitride is not completely stable during vacuum sintering,
causing at least partial volatilization of the nitrogen, it is
preferable to add one-half mole of carbon per mole of starting
nitrogen to maintain the carbon level necessary for a tungsten lean
cobalt binder alloy. It has been found that cobalt enrichment via
heat treating of tungsten carbide-cobalt base alloys occurs more
readily when the alloy contains a tungsten lean cobalt binder. The
tungsten lean cobalt binder preferably should have a 145 to 157
gauss-cm.sup.3 /gm cobalt magnetic saturation. Titanium nitride
additions along with the necessary carbon additions to tungsten
carbide-cobalt base powder mixes promote the formation of a 145 to
157 magnetic saturation cobalt binder alloy which is ordinarily
difficult to achieve. Although a cobalt binder alloy having 145 to
157 gauss-cm.sup.3 /gm cobalt magnetic saturation is preferred,
alloys containing tungsten saturated cobalt binder alloys (less
than 125 gauss-cm.sup.3 /gm cobalt) can also be enriched.
.Iadd.Furthermore, a cobalt binder alloy having a magnetic
saturation value of less than 158 gauss-cm.sup.3 /gm cobalt and at
least 139 gauss-cm.sup.3 /gm cobalt is another preferred range
within the scope of the invention. As previously mentioned, carbon
saturated cobalt, i.e. a C porosity substrate, has a magnetic
saturation value of about 158 gauss-cm.sup.3 /gm cobalt. Example 14
herein reports a tungsten content in the W-Co binder alloy of 10
weight percent. Such a W-Co binder alloy has a magnetic saturation
value of about 139 gauss-cm.sup.3 /gm cobalt based on data
presented in the 1973 article by Tillwick, D. C. and Joffe, I.,
"Magnetic Properties of Co-W Alloys in Relation to Sintered WC-Co
Compacts", Scripta Metallurgia, Vol. 7, pp. 479-484 (1973).
.Iaddend.
It has been found that a layer of cobalt enrichment thicker than
six microns results in a significant improvement in the edge
strength of refractory coated cemented carbide inserts. While
cobalt enrichment as deep as 125 microns has been achieved, a
cobalt enriched layer having a thickness of 12 to 50 microns is
preferred for coated cutting insert applications. It is also
preferable that the cobalt content of the cobalt enriched layer on
a refractory coated insert be between 150 to 300 percent of the
mean cobalt content as measured on the surface by energy dispersive
X-ray analysis. .Iadd.Furthermore, the ranges of binder or cobalt
enrichment in the enriched layer preferably includes a content that
reaches between about 175 percent to about 300 percent of the
average binder or cobalt content of the cemented carbide body. The
ranges of binder or cobalt enrichment in the enriched layer also
includes a binder or cobalt content that preferably reaches between
about 200 percent and about 300 percent of the average cobalt
content of the cemented carbide body. .Iaddend.
.[.it.]. .Iadd.It .Iaddend.is believed that binder enrichment
should occur in all tungsten carbide-binder-cubic carbide (i.e.,
tantalum, niobium, titanium, vanadium, hafnium, zirconium) alloys
which do not sinter to a .[.coninuous.]. .Iadd.continuous
.Iaddend.carbide skeleton. These alloys containing binder from 3
weight percent and above should enrich utilizing the disclosed
process. However, for cutting insert applications, it is preferred
that the binder content be between 5 and 10 weight percent cobalt
and that the total cubic carbide content be 20 weight percent or
less. While cobalt is the preferred binder, nickel, iron and their
alloys with one another, as well as with cobalt, may be substituted
for cobalt. Other binder alloys containing nickel or cobalt or iron
should also be suitable.
The sintering and heat treating temperatures used to obtain binder
enrichment are the typical liquid phase sintering temperatures. For
cobalt base alloys, these temperatures are 1285 to 1540 degrees
Centigrade. Sintering cycles should be at least 15 minutes at
temperature. Results can be further optimized by the use of
controlled cooling rates from the heat treating temperatures down
to a temperature below the binder alloy melting point. These cool
down rates should be between 25 to 85 degrees Centrigrade/hour,
preferably 40 to 70 degrees Centrigrade/hour. Most preferably, the
heat treat cycle for cutting insert substrates having a cobalt
binder is 1370 to 1500 degrees Centrigrade for 30 to 150 minutes,
followed by a 40 to 70 degrees Centigrade/hour cool down to 1200
degrees Centigrade. Pressure levels during heat treating can vary
from 10.sup.-3 torr up to and including those elevated pressures
typically used in hot isostatic pressing. The preferred pressure
level is 0.1 to 0.15 torr. If nitride or carbonitride additions are
being utilized, the vapor pressure of the nitrogen in the sintering
atmosphere is preferably below its equilibrium pressure, so as to
allow volatilization of nitrogen from the substrate.
While initial enrichment will occur upon sintering, subsequent
grinding steps in the metal cutting insert fabrication process may
remove the enriched zones. In these situations, a subsequent heat
treatment in accordance with the above parameters can be utilized
to develop a new enriched layer beneath the peripheral
surfaces.
Binder enriched substrates to be used in coated cutting inserts can
have binder enrichment on both the rake and flank faces. However,
depending on insert style, the binder enrichment on the flank face
may sometimes be removed, but this is not necessary to achieve
optimum performance in all cases.
The binder enriched substrates can be coated using the refractory
coating techniques well known to those skilled in the art. While
the refractory coating applied can have one or more layers
comprising materials selected from the Group IVB and VB carbides,
nitrides, borides, and carbonitrides, and the oxide of the
oxynitride of aluminum, it has been found that a combination of
good cutting edge strength and flank wear can be achieved by
combining a substrate having a binder enriched layer according to
the .[.prsent.]. .Iadd.present .Iaddend.invention with a coating
of: aluminum oxide over an inner layer of titanium carbide; or an
inner layer of titanium carbide bonded to an intermediate layer of
titanium carbontride, which is bonded to an outer layer of titanium
nitride, or titanium nitride bonded to an inner layer of titanium
carbide. A cemented carbide body having a binder enriched layer
according to the present invention in combination with a titanium
carbide/aluminum oxide coating is most preferred. In this case, the
coating should have a total coating thickness of 5 to 8
microns.
Referring now to FIG. 1, an embodiment of a coated metalcutting
insert 2 according to the present invention is schematically shown.
The insert 2 is comprised of a substrate or cemented carbide body
12 having a binder enriched layer 14, and a binder depleted layer
16 over the bulk 18 of the substrate 12 which has a chemistry
substantially equal to the chemistry of the original powder
blend.
A binder enriched layer 14 is present on the rake faces 4 of the
cemented carbide body and has been ground off the flank faces 6 of
the body. Located inwardly of the binder enriched layer 14 may be a
binder depleted zone 16. This binder depleted zone 16 has been
found to develop along with the binder enriched layer when cemented
carbide bodies are fabricated according to the disclosed
process.
The binder depleted zone 16 is partially depleted in binder
material while being enriched in solid solution carbides. The
enriched layer 14 is partially depleted in solid solution carbides.
Inwardly of the binder depleted zone 16 is bulk substrate material
18.
At the junction of the rake faces and flank faces 6, a cutting edge
8 is formed. While the cutting edge 8 shown here is honed, honing
of the cutting edge is not necessary for all applications of the
present invention. It can be seen in FIG. 1 that the binder
enriched layer 14 extends into this cutting edge area and is,
preferably, adjacent to most, if not all, of the honed edge 8. The
binder depleted zone 16 extends to the flank surface 6 just below
the cutting edges 8. A refractory coating 10 has been adherently
bonded to the peripheral surface of the cemented carbide body
12.
These and other features of the invention will become more apparent
upon reviewing the following examples.
A mix containing 7000 grams of powders was milled and blended for
16 hours with a paraffin, a surfactant, a solvent and cobalt bonded
tungsten carbide cycloids, in the amounts and proportions shown
below
______________________________________ 10.3 w/o* Ta(C) 5.85 w/o*
Ti(C) 0.2 w/o* Nb(C) 8.5 w/o Co 7000 gm 1.5 w/o* Ti(N) .[.-.]. =
102.6 grams .[.WC.]. .Iadd. WC + C to produce a 2 w/o W - 98 w/o Co
binder alloy 2 w/o paraffin (Sunoco 3420) (Sun Oil Co.) 2.5 liter
solvent (perchloroethylene) 14 gram surfactant (Ethomeen S-15)
(Armour Industrial Chemcial Co.)
______________________________________ *weight percent of metal
added. .Iaddend. These inserts were vacuum sintered at 1496 degrees
Centigrade for 30 minutes, and then cooled under ambient furnace
conditions. After sintering, the inserts weighed 1125 grams and
were 13.26 mm.times.13.26 mm.times.4.95 mm in size. These inserts
were then processed to SNG433 ground dimensions as follows: (this
identification number is based on the insert identification system
developed by the American Standards Association and which has been
generally adopted by the cutting tool industry. The International
designation is: SNGN 12 04 12)
1. Tops and bottoms (rake faces) of the inserts were ground to a
thickness of 4.75 mm.
2. The inserts were heat treated at 1427 degrees Centigrade for 60
minutes under a 100 micron vacuum, then cooled at a rate of 56
degrees Centigrade/hour to 1204 degrees Centigrade, followed by
cooling under ambient furnace conditions.
3. The periphery (flank faces) were ground to produce a 12.70 mm
square and the cutting edges honed to a 0.064 mm radius.
A titanium carbide/titanium carbonitride/titanium nitride coating
was then applied to the ground inserts using the following chemical
vapor deposition (CVD) techniques in the following order of
application:
TABLE I
__________________________________________________________________________
Coating Type Temperature Pressure Coating Pressure
__________________________________________________________________________
TiC 982-1025.degree. C. .about.1 atm. ##STR1## TiCN
982-1025.degree. C. .about.1 atm. ##STR2## TiN 982-1050.degree. C.
.about.1 atm. ##STR3##
__________________________________________________________________________
Processed along with the above inserts were inserts made from the
same powder blend but without the TiN and its attendent carbon
addition. Microstructural data obtained from the coated inserts are
shown below:
______________________________________ EXAMPLE 1 EXAMPLE 1 without
TiN with TiN ______________________________________ Porosity A1 A1,
B2 (non- enriched, bulk) A1 (enriched) Cobalt Enriched None
.about.22.9 microns Zone Thickness (rake face only) Solid Solution
None .about.22.9 microns) Depleted Zone (rake face only) Thickness
TiC/Substrate 4.6 microns 3.3 microns Interface Eta Phase Thickness
Coating Thickness TiC 5.6 microns 5.0 microns TiCN 2.3 microns 3.9
microns TiN 1.0 microns 1.0 microns
______________________________________
EXAMPLE NO. 2
Green pill pressed inserts were fabricated according to Example 1
utilizing the Example 1 blends with and without the TiN and its
attendent carbon additions. These inserts were sintered at 1496
degrees Centigrade for 30 minutes under a 25 micron vacuum and then
cooled under ambient furnace conditions. They were then honed
(0.064 mm radius), and subsequently TiC/TiCN/TiN CVD coating
according to the techniques shown in Table I. In this example, it
should be noted that the cobalt enriched layer was present on both
flank and rake faces.
The coated inserts were subsequently evaluated and the following
results were obtained:
______________________________________ EXAMPLE 2 EXAMPLE 2 without
TiN with TiN ______________________________________ Porosity A-1
edges A-2 enriched zone A-3 center A-4 bulk Cobalt Enriched None up
to 22.9 Zone Thickness microns Solid Solution None partial and
Depleted Zone intermittent up Thickness to 21 microns TiC/Substrate
up to 5.9 3.3 microns Interface Eta microns Phase Thickness Coating
Thickness TiC 2.0 microns 1.3 microns TiCN 1.7 microns 1.0 microns
TiN 8.8 microns 7.9 microns Average Rockwell 91.2 91.4 "A" Hardness
(Bulk Material) Coercive Force, Hc 138 oersteds 134 oersteds
______________________________________
EXAMPLE NO. 3
A mix comprising the following materials was charged into a
cylindrical mill, with a surfactant, fugitive binder, solvent and
114 kilograms of cycloids:
______________________________________ WC (2-2.5 micron 15,000
grams particle size) 85.15 w/o WC (4-5 micron 27,575 grams particle
size) 5.98 w/o TaC 2,990 grams 2.6 w/o TiN 1,300 grams 6.04 w/o Co
3,020 grams 0.23 w/o C(Ravin 410-a product 115 grams of Industrial
Carbon Corp.) 50,000 grams
______________________________________
The powder charge was balanced to produce 6.25 weight percent total
carbon in the charge. The mix was blended and milled for 90,261
revolutions to obtain an average particle size of 0.90 microns. The
blend was then wet screened, dried and hammer milled. Compacts were
pressed and then sintered at 1454 degrees Centigrade for 30 minutes
followed by cooling under ambient furnace conditions.
This treatment produced a sintered blank having an overall (i.e.,
measurement included bulk and binder enriched material) magnetic
saturation of 117 to 121 gauss-cm.sup.3 /gm cobalt. Microstructural
evaluation of the sintered blank showed: eta phase to be present
throughout the blank; porosity to be A-2 to B-3; the cobalt
enriched zone thickness to be approximately 26.9 microns; and the
solid solution depicted zone thickness to be approximately 31.4
microns.
EXAMPLE NO. 4
The following materials were added to a 190 mm inside diameter by
194 mm long mill jar lined with a tungsten carbide cobalt alloy. In
addition, 17.3 kilograms of 3.2 mm tungsten carbide-cobalt cycloids
were added to the jar. These materials were milled and blended
together by rotating the mill jar about its cylindrical axis at 85
revolutions per minute for 72 hours (i.e., 367,200
revolutions).
______________________________________ CHARGE COMPOSITION
______________________________________ 283 grams (4.1 wt. %) TaC
205 grams (3.0 wt. %) NbC 105 grams (1.5 wt. %) TiN 7.91 grams (0.1
wt. %) C 381 grams (5.5 wt. %) Co 5946 grams (85.8 wt. %) WC
.about.105 grams Sunoco 3420 14 grams Ethomeen S-15 2500
milliliters Perchloroethylene
______________________________________
This mix was balanced to produce a 2 w/o W--98 w/o Co binder alloy.
After milling and blending, the slurry was wet screened to remove
oversized particles and contaminants, dried at 93 degrees
Centigrade under a nitrogen atmosphere and then hammer milled to
break up agglomerates in a Fitzpatrick Co. J-2 Fitzmill.
Using this powder, compacts were pressed and then sintered at 1454
degrees Centigrade for 30 minutes and cooled under ambient
conditions.
The top and bottom (i.e., the rake faces) of the insert were then
ground to final thickness. This was followed by a heat treatment at
1427 degrees Centigrade under an 100 micron vacuum. After 60
minutes at temperature, the inserts were cooled at a rate of 56
degrees Centigrade/hour to 1204 degrees Centigrade and then furnace
cooled under ambient conditions. The periphery (or flank) surfaces
were then ground to a 12.70 mm square and the insert cutting edges
honed to a 0.064 mm radius. These treatments resulted in an insert
substrate in which only the rake faces had a cobalt enriched and
solid solution depleted zone, these zones having been ground off
the flank faces.
The inserts were then loaded into a coating reactor and coated with
a thin layer of titanium carbide using the following chemical vapor
deposition technique. The hot zone containing the inserts was first
heated from room temperature to 900 degrees Centigrade. During this
heating period, hydrogen gas was allowed to flow through the
reactor at a rate of 11.55 liters per minute. The pressure within
the reactor was maintained at slightly less than one atmosphere.
The hot zone was then heated from 900 degrees Centigrade to 982
degrees Centigrade. During this second heat up stage, the reactor
pressure was maintained at 180 torr. and a mixture of titanium
tetrachloride and hydrogen, and pure hydrogen gas entered the
reactor at flow rates of 15 liters per minute and 33 liters per
minute, respectively. The mixtures of titanium tetrachloride and
hydrogen gas was achieved by passing the hydrogen gas through a
vaporizer holding the titanium tetrachloride at a temperature of 47
degrees Centigrade. Upon attaining 982 degrees Centigrade, methane
was then allowed to also enter the reactor at a rate of 2.5 liters
per minute. The pressure within the reactor was reduced to 140
torr. Under these conditions, the titanium tetrachloride reacts
with the methane in the presence of hydrogen to produce titanium
carbide on the hot insert surface. These conditions were maintained
for 75 minutes, after which the flow of titanium tetrachloride,
hydrogen and methane was terminated. The reactor was then allowed
to cool while Argon was being passed through the reactor at a flow
rate of 1.53 liters per minute under slightly less than one
atmosphere pressure.
Examination of the microstructure in the final insert revealed a
cobalt enriched zone extending inwardly up to 22.9 microns and a
cubic carbide solid solution depletion zone extending inwardly up
to 19.7 microns from the substrate rake surfaces. The porosity in
the enriched zone and the remainder of the substrate was estimated
to be between A-1 and A-2.
EXAMPLE NO. 5
The material in this example was blended and milled using a two
stage milling process with the following material charges:
______________________________________ Stage I (489,600
revolutions) 141.6 grams (2.0 wt. %) TaH 136.4 grams (1.9 wt. %)
TiN 220.9 grams (3.1 wt. %) NbC 134.3 grams (1.9 wt. %) TaC 422.6
grams (5.9 wt. %) Co 31.2 grams (0.4 wt. %) C 14 grams Ethomeen
S-15 1500 milliliters Perchloroethylene Stage II (81,600
revolutions) 6098 grams (84.9 wt. %) WC 140 grams Sunoco 3420 1000
milliliters Perchloroethylene
______________________________________
This was balanced to produce a 2 w/o W--98 w/o Co binder alloy.
The test inserts were then fabricated and TiC coated in accordance
and along with the test blanks described in Example No. 4.
Microstructural evaluation of the coated inserts revealed the
porosity in the cobalt enriched as well as the bulk material to be
A-1. The cobalt enriched zone and the solid solution depleted zone
extended inward from the rake surface to depths of approximately
32.1 microns and 36 microns, respectively.
EXAMPLE NO. 6
The following materials were charged into a 190 mm inside diameter
mill jar:
______________________________________ 283 grams (4.1 w/o) TaC 205
grams (3.0 w/o) NbC 105 grams (1.5 w/o) TiN 7.91 grams (0.1 w/o) C
381 grams (5.5 w/o) Co 5946 grams (85.8 w/o) WC 140 grams Sunoco
3420 14 grams Ethomeen S-15 2500 milliliters Perchloroethylene
______________________________________
This mix was balanced to produce a 2 w/o W--98 w/o Co binder
alloy.
In addition, cycloids were added to the mill. The mixture was then
milled for four days. The mix was dried in a sigma blender at 121
degrees Centigrade under a partial vacuum, after which it was
Fitzmilled through a 40 mesh sieve.
SNG433 inserts were then fabricated using the techniques described
in Example 4. The inserts in this Example, however, were CVD coated
with a TiC/TIN coating. The coating procedure used was as
follows:
1. TiC coating--The samples in the coating reactor were held at
approximately 1026 to 1036 degrees Centigrade under a 125 torr
vacuum. Hydrogen carrier gas flowed into a TiCl.sub.4 vaporizer at
a rate of 44.73 liters/minute. The vaporizer was held at 33 to 35
degrees Centigrade under vacuum. TiCl.sub.4 vapor was entrained in
the H.sub.2 carrier gas and carried into the coating reactor. Free
hydrogen and free Methane flowed into the coating reactor at 19.88
and 3.98 liters/minute, respectively. These conditions were
maintained for 100 minutes and produced a dense TiC coating
adherently bonded to the substrate.
2. TiN coating--Methane flow into the reactor was discontinued and
N.sub.2 was allowed into the reactor at a rate of 2.98
liters/minute. These conditions were maintained for 30 minutes and
produced a dense TiN coating adherently bonded to the TiC
coating.
Evaluation of the Coated inserts produced the following
results:
______________________________________ Porosity A-1, throughout
Cobalt Enriched Zone 17.0 to 37.9 microns Thickness Solid Solution
Depleted up to 32.7 microns Zone Thickness TiC/Substrate Interface
up to 3.9 microns Eta Phase Thickness Coating Thickness TiC 3.9
microns TiN 2.6 microns Average Rockwell "A" 91.0 Hardness of Bulk
Coercive Force, Hc 98 oersteds
______________________________________
EXAMPLE NO. 7
A blend of material was made using the following two stage milling
cycle:
In Stage I, the following materials were added to a 181 mm inside
diameter by 194 mm long WC-Co lined mill jar with 17.3 kg of 4.8 mm
WC-Co cycloids. The mill jar was rotated about its cylindrical axis
at 85 revolutions per minute for 48 hours (244,800
revolutions).
______________________________________ 140.8 grams (2.0 wt. %) Ta
72.9 grams (1.0 wt. %) TiH 23.52 grams (0.3 wt. %) C 458.0 grams
(6.5 wt. %) Co 30 grams Ethomeen S-15 120 grams Sunoco 3420 1000
milliliters Soltrol 130 (a solvent)
______________________________________
In Stage II, 6314 grams (90.2 wt. %) WC and 1500 ml Soltrol 130
were added and the entire charge rotated an additional 16 hours
(81,600) revolutions. This mix was balanced to produce a 5 w/o
W--95 w/o Co binder alloy. After milling, the slurry was wet
screened through 400 mesh, dried under nitrogen at 93 degrees
Centigrade for 24 hours and Fitzmilled through a 40 mesh
screen.
Test samples were uniaxially pressed at 16,400 kilograms total
force to 15.11 mm.times.15.11 mm.times.5.28 mm (8.6 gram/cc
specific gravity).
The above green test samples were sintered at 1468 degrees
Centigrade for 150 minutes under a 1 micron vacuum. The inserts was
then cooled under ambient furnace conditions. Flake graphite was
used as the parting agent between the test inserts and the graphite
sintering trays.
The as sintered inserts were honed to a 0.064 mm radius. The
inserts were then coated with a TiC/TiCN/TiN coating according to
the following procedure:
1. Inserts were located into the reactor and air purged out of the
reactor by flowing hydrogen through it.
2. Inserts were heated to approximately 1038 degrees Centigrade
while maintaining hydrogen flow through the reactor. Coating
reactor pressure was held at slightly greater than one
atmosphere.
3. TiC coating--For 25 minutes, a mixture of H.sub.2 +TiCl.sub.4
entered the reactor at a rate of approximately 92 liters/minute and
methane entered the reactor at a rate of 3.1 liters/minute. The
TiCl.sub.4 vaporizer was maintained at approximately 6 psi and 30
degrees Centigrade.
4. TiCN coating--For 13 minutes, the flow of the H.sub.2
+TiCl.sub.4 mixture was substantially maintained; the flow of
methane reduced by one-half; and N.sub.2 was introduced into the
reactor at a rate of 7.13 liters/minute.
5. TiN coating--For 12 minutes, the methane flow was discontinued
and the nitrogen flow rate doubled. Upon completion of TiN coating,
both the flow of the H.sub.2 +TiCl.sub.4 mixture and the N.sub.2
were discontinued, the reactor heating elements shut off and the
reactor purged with free H.sub.2 until it cooled to approximately
250 degrees Centigrade. At 250 degrees Centigrade, the reactor was
purged with nitrogen.
It was determined that the insert substrates had an A-1 to A-2
porosity in their nonenriched interior or bulk material. A cobalt
enriched zone and solid solution depleted zone extended in from the
surfaces approximately 25 microns and 23 microns, respectively. The
nonenriched interior had an average hardness of 91.7 Rockwell "A".
The coercive force, Hc, of the substrate was found to be 186
oersteds.
EXAMPLE NO. 8
A 260 kg blend of powder, having carbon balanced to C3/C4 porosity
in the final substrate, was fabricated using the following two
stage blending and milling procedure:
STAGE I
The following charge composition was milled for 96 hours:
______________________________________ 10,108 grams TaC (6.08 w/o
Carbon) 7,321 grams NbC (11.28 w/o Carbon) 3,987 grams TiN 1,100
grams C (Molocco Black-a product of Industrial Carbon Corp.) 16,358
grams Co 500 grams Ethomeen S-15 364 kilograms 4.8 mm Co--WC
cycloids Naphtha ______________________________________
STAGE II
The following was added to the above blend, and the mixture milled
for an additional 12 hours:
221.75 kilograms: WC (6.06 w/o Carbon)
5.0 kilograms: Sunoco 3420 Naphtha
The final blend was then wet screened, dried, and Fitzmilled.
Insert blanks were then pressed and later sintered at 1454 degrees
Centigrade for 30 minutes. This sintering procedure produce a
cobalt enriched zone overlying bulk material having a C3/C4
porosity. The sintered blanks were then ground and honed to SNG433
insert dimensions, resulting in removal of the cobalt enriched
zone.
The sintered inserts were then packed with flake graphite inside of
an open graphite canister. This assembly was then hot isostatically
pressed (HIPed) at 1371 to 1377 degrees Centigrade for one hour
under a 8.76.times.10.sup.8 dynes/cm.sup.2 atmosphere of 25 v/o
N.sub.2 and 75 v/o He. Microstructural examination of a HIPed
sample revealed that a cobalt enriched zone of approximately 19.7
microns in depth had been produced during HIPing. About 4 microns
of surface cobalt and 2.mu. surface of carbon were also produced
due to the C type porosity substrate utilized.
EXAMPLE NO. 9
A batch containing the following materials was ball milled:
______________________________________ 30. w/o WC (1.97 micron
average particle size) 750 kg 51.4. w/o WC (4.43 micron average
particle size) 1286 kg 6.0 w/o Co 150 kg 5.0 w/o WC--TiC solid
solution carbide 124.5 kg 6.1 w/o WC--TiC solid solution carbide
152 kg 1.5 w/o W 37.5 kg ______________________________________
This mix was charged to 6.00 w/o total carbon. These materials were
milled for 51,080 revolutions with 3409 kilograms of cycloids and
798 liters of naphtha. A final particle size of 0.82 microns was
produced.
Five thousand grams of powder were split from the blended and
milled batch and the following materials added to it:
______________________________________ 1.9 w/o TiN (premilled to
approxi- 96.9 gm mately 1.4 to 1.7 microns) 0.2 w/o C (Ravin 410)
9.4 gm 1500 ml Perchloroethylene
______________________________________
These materials were then milled in a 190 mm inside diameter
tungsten carbide lined mill jar containing 50 volume percent
cycloids (17.3 kg) for 16 hours. Upon completion of milling, the
lot was wet screened through a 400 mesh screen, dried under partial
vacuum in a sigma blender at 121 degrees Centigrade, and then
Fitzmilled through a 40 mesh sieve.
SNG433 blanks were pressed using a force of 3600 kilograms to
produce a blank density of 8.24 gm/cc and a blank height of 5.84 to
6.10 mm.
The blanks were sintered at 1454 degrees Centigrade for 30 minutes
on a NbC powder parting agent under a 10 to 25 micron vacuum and
then allowed to furnace cool. The sintered samples had sintered
dimensions of 4.93 mm.times.13.31 mm square, a density of 13.4
gm/cc and an overall magnetic saturation value of 146 to 150
gauss-cm.sup.3 /gm Co. Microstructural evaluation of the samples
showed A porosity throughout and a cobalt enriched layer
approximately 21 microns thick.
The top and bottom of the inserts were then ground to a total
thickness of 4.75 mm. The inserts were then heat treated at 1427
degrees Centigrade for 60 minutes under a 100 micron vacuum cooled
to 1204 degrees Centigrade at a rate of 56 degrees Centigrade/hour
and then furnace cooled.
The flank faces of each insert were ground to a 12.70 mm square and
the edges honed to a 0.064 mm radius.
The inserts were subsequently CVD coated with titanium
carbide/aluminum oxide using the following techniques.
The inserts were placed in a coating reactor and heated to
approximately 1026 to 1030 degrees Centigrade and held under an 88
to 125 torr vacuum. Hydrogen gas at a rate of 44.73 liters/minute
was passed through a vaporizer containing TiCl.sub.4 at 35 to 38
degrees Centigrade under vacuum. TiCl.sub.4 vapor was entrained in
the hydrogen and directed into the coating reactor. Simultaneously,
hydrogen and methane were flowing into the reactor at rates of
19.88 and 2.98 liters/minute. These conditions of .[.vacuu.].
.Iadd.vacuum.Iaddend., temperature, and flow rate were maintained
for 180 minutes producing an adherent TiC coating on the inserts.
Hydrogen flow to the vaporizer and methane flow into the reactor
were then terminated. Hydrogen and chlorine were now allowed to
flow to a generator containing aluminum particles at 380 to 400
degrees Centigrade and 0.5 psi pressure. The hydrogen and chlorine
flowed into the generator at rates of 19.88 liters/minute and 0.8
to 1.0 liter/minute, respectively. The chlorine reacted with the
aluminum to produce AlCl.sub.3 vapors which were then directed into
the reactor. While the hydrogen and AlCl.sub.3 were flowing into
the reactor, CO.sub.2 at a rate of 0.5 liters/minute was also
flowing into the reactor. These flow rates were maintained for 180
minutes during which time the inserts were held at 1026 to 1028
degrees Centigrade under a vacuum of approximately 88 torr. This
procedure produced a dense coating of Al.sub.2 O.sub.3 adherently
bonded to a TiC inner coating.
Evaluation of the coated inserts produced the following
results:
______________________________________ Porosity A1 in enriched
zone, A1 with scattered B in the bulk material Cobalt Enriched Zone
approximately 39.3 Thickness (rake microns surface) Solid Solution
Depleted up to 43.2 microns Zone Thickness (rake surface) Coating
Thickness TiC 5.9 microns Al.sub.2 O.sub.3 2.0 microns Average Bulk
Substrate 91.9 Rockwell A Hardness Coercive Force, Hc 170 oersteds
______________________________________
EXAMPLE NO. 10
An additional 5000 grams of material were split from the initial
batch of material produced in Example 9. Premilled TiCN in the
amount of 95.4 grams (1.9 w/o) and 1.98 grams (0.02 w/o) Ravin 410
carbon black were added to this material, mixed for 16 hours,
screened, dried, and Fitzmilled, as per Example 9.
Test pieces were pill pressed, vacuum sintered at 1496 degrees
Centigrade for 30 minutes, and then furnace cooled at the ambient
furnace cooling rate. Evaluation of the sintered samples produced
the following results:
______________________________________ Porosity A-1, throughout
Cobalt Enriched Zone approximately 14.8 Thickness microns Solid
Solution Depleted up to 19.7 microns Zone Thickness Average Bulk
Substrate 92.4 Rockwell A Hardness Magnetic Saturation 130
gauss-cm.sup.3 /gm Co Coercive Force, (Hc) 230 oersteds
______________________________________
EXAMPLE NO. 11
An additional 5000 grams of material were split from the initial
batch made in Example 9. Premilled TiCN in the amount of 95.4 grams
(1.9 w/o) was added, mixed for 16 hours, screened, dried and
Fitzmilled as per Example 9. Test pieces were then pressed and
sintered at 1496 degrees Centigrade with the Example 10 test
pieces.
Evaluation of the sintered samples produced the following
results:
______________________________________ Porosity A-1, with heavy eta
phase throughout Cobalt Enriched Zone approximately 12.5 Thickness
microns Solid Solution Depleted up to 16.4 microns Zone Thickness
Average Bulk Rockwell 92.7 A Hardness Magnetic Saturation 120
gauss-cm.sup.3 /gm Co Coercive Force, Hc 260 oersteds
______________________________________
EXAMPLE NO. 12
The following mix was charged using the two stage milling cycle
outlined below:
STAGE I
The following materials were added to a 181 mm inside diameter by
194 mm long WC-Co lined mill jar with 17.3 kg of 4.8 mm WC-Co
cycloids. The mill jar was rotated about its cylindrical axis at 85
revolutions per minute for 48 hours (244,800 revolutions).
______________________________________ 455 grams (6.5 wt. %) Ni 280
grams (4.0 wt. %) TaN 112 grams (1.6 wt. %) TiN 266 grams (3.8 wt.
%) NbN 42.7 grams (0.6 wt. %) Carbon 14.0 grams Ethomeen S-15 1500
milliliters Perchloroethylene
______________________________________
The following were then added to the mill jar and rotated an
additional 16 hours (81,600 revolutions):
______________________________________ 5890 grams (83.6 wt. %) WC
105 grams Sunoco 3420 1000 milliliters Perchloroethylene
______________________________________
This mix was balanced to produce a 10 w/o .Iadd.W.Iaddend.-90 w/o
Ni binder alloy. After discharging the mix slurry from the mill
jar, it was wet screened through a 400 mesh sieve (Tyler), dried at
93 degrees Centigrade under an nitrogen atmosphere, and Fitzmilled
through a 40 mesh sieve.
Test samples were pill pressed, sintered at 1450 Centigrade for 30
minutes under a 6.9.times.10.sup.4 dynes/cm.sup.2 nitrogen
atmosphere, and then furnace cooled at the ambient furnace cooling
rate. Following sintering, the samples were HIPed at 1370 degrees
Centigrade for 60 minutes in a 1.times.10.sup.9 dynes/cm.sup.2
helium atmosphere. Optical metallographic evaluation of the HIPed
samples showed the material to have A-3 porosity throughout and a
solid solution depletion zone thickness of approximately 25.8
microns.
Subsequently, the sample was reprepared and examined by energy
dispersive x-ray line scan analysis (EDX) at various distances from
the rake surface. FIG. 3 shows a graphical representation of the
variation of nickel, tungsten, titanium and tantalum relative
concentrations as a function of distance from the rake surface of
the sample. It can be clearly seen that there is a layer near the
surface in which the titanium and tantalum, forming carbides which
are in solid solution with tungsten carbide, are at least partially
depleted. This solid solution depleted zone extends inwardly
approximately 70 microns. The discrepancy between this value and
the value reported above are believed to be due to the fact that
the sample was reprepared between evaluations so that different
planes through the sample were examined in each evaluation.
Corresponding with the titanium and tantalum depletion is an
enriched layer of nickel (see FIG. 3). The nickel concentration in
the enriched layer decreases as the distance from the rake surface
decreases from 30 to 10 microns. This indicates that the nickel in
this zone was partially volatilized during vacuum sintering.
The spike in titanium and tantalum concentration at 110 microns is
believed to be due to the scanning of a random large grain or
grains having a high concentration of these elements.
The two parallel horizontal lines show the typical scatter obtained
in analysis of the bulk portion of the sample around the nominal
blend chemistry.
EXAMPLE NO. 13
The following mix was charged using the two stage milling cycle
outlined below:
STAGE I
The following materials were milled per Stage I of Example 12:
______________________________________ 455 grams (6.4 w/o) Ni 280
grams (3.9 w/o) TaH 112 grams (1.6 w/o) TiN 266 grams (3.7 w/o) NbN
61.6 grams (0.9 w/o) C Ravin 410, 502 14 grams Ethomeen S-15 2500
milliliters Perchloroethylene
______________________________________
STAGE II
The following were then added to the mill jar and rotated an
additional 16 hours:
______________________________________ 5980 grams (83.6 w/o) WC 140
grams Sunoco 3420 ______________________________________
This mix was balanced to produce 10 w/o W--90 w/o Ni binder
alloy.
After discharging the mix, it was screened, dried and Fitzmilled
per Example 12.
Pressed test samples were vacuum sintered at 1466 degrees
Centigrade for 30 minutes under a 35 micron atmosphere. The
sintered samples had an A-3 porosity throughout and a solid
solution depletion zone up to 13.1 microns thick.
EXAMPLE NO. 14
A mix was charged using the following two stage milling cycle:
STAGE I
The following materials were added to a 190 mm inside diameter by
194 mm long WC-Co lined mill jar with 17.3 kg of 4.8 mm WC-Co
cycloids. The mill jar was rotated about its axis at 85 revolutions
per minute for 48 hours (244,800 revolutions):
______________________________________ 177 grams (2.5 wt. %)
HfH.sub.2 182.3 grams (2.5 wt. %) TiH.sub.2 55.3 grams (0.8 wt. %)
Carbon 459 grams (6.4 wt. %) Co 14 grams Ethomeen S-15 2500
milliliters Perchloroethylene
______________________________________
STAGE II
The following was then added to the mill jar and rotated an
additional 16 hours (81,600 revolutions):
______________________________________ 6328 grams (87.9 wt. %) WC
140 grams Sunoco 3420 ______________________________________
This mix was balanced to produce 10 w/o W--90 w/o Co binder
alloy.
After discharging the slurry from the mill jar, it was wet screened
through 400 mesh, dried at 93 degrees Centigrade under a nitrogen
atmosphere, and Fitzmilled through a 40 mesh screen.
Insert blanks were pressed and then sintered at 1468 Centigrade for
30 minutes under a 35 micron vacuum allowing volatization of a
majority of the hydrogen in the samples. During sintering, the
samples were supported on a NbC powder parting agent.
The sintered sample had A-2 porosity in the enriched zone and A-4
porosity in the nonenriched bulk of sample. The sample had an
average Rockwell "A" hardness of 90; a zone of solid solution
depletion 9.8 microns thick; and a coercive force, Hc, of 150
oersteds.
EXAMPLE NO. 15
A batch of material having a composition equivalent to the Example
9 batch was blended, milled and pressed into insert blanks. The
blanks were then sintered, ground, heat treated and ground (flank
faces only) in substantial accordance with the procedures used in
Example 9. However, a 60 degrees Centigrade/hour cooling rate was
used in the final heat treatment.
An insert was analyzed by EDX line scan analysis at various
distances from the insert rake surfaces. The results of this
analysis is shown in the FIG. 2 graph. It indicates the existence
of a cobalt enriched layer extending inwardly from the rake
surfaces to a depth of approximately 25 microns followed by a layer
of material partially depleted in cobalt extending inwardly to
approximately 90 microns from the rake surfaces. While not shown in
the FIG. 2 graph, partial solid solution depletion has been found
in the cobalt enriched layer and solid solution enrichment has been
found in the partially depleted cobalt layer.
The two horizontal lines indicate the typical scatter in analysis
of the bulk material around the nominal blend chemistry.
The preceding description and detailed examples have been provided
to illustrate some of the possible alloys, products, processes and
uses that are within the scope of this invention as defined by the
following claims.
* * * * *