U.S. patent number RE41,972 [Application Number 11/653,420] was granted by the patent office on 2010-11-30 for aluminum oxide coated tool.
This patent grant is currently assigned to Sandvik Intellectual Property AB. Invention is credited to Anders Lenander, Bjorn Ljungberg.
United States Patent |
RE41,972 |
Lenander , et al. |
November 30, 2010 |
Aluminum oxide coated tool
Abstract
There is provided a tool at least partly coated with at least
two refractory layers of which one of the said layers is a
fine-grained .alpha.-Al.sub.2O.sub.3-layer which is the top layer
along the cutting edge-line and the other a
TiC.sub.xN.sub.yO.sub.z- or a ZrC.sub.xN.sub.y-layer being the top
layer on the clearance face. The coated tool exhibits excellent
flank and crater wear and high resistance to flaking, particularly
when used for machining of low carbon steel and stainless steel.
Used cutting edges can easily be identified by the naked eye.
Inventors: |
Lenander; Anders (Tyreso,
SE), Ljungberg; Bjorn (Enskede, SE) |
Assignee: |
Sandvik Intellectual Property
AB (Sandviken, SE)
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Family
ID: |
20394780 |
Appl.
No.: |
11/653,420 |
Filed: |
January 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
08497934 |
Jul 5, 1995 |
05861210 |
Jan 19, 1999 |
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Foreign Application Priority Data
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Jul 20, 1994 [SE] |
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9402543-4 |
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Current U.S.
Class: |
428/336;
427/255.31; 428/698; 427/419.1; 428/702; 51/307; 428/216; 51/309;
51/295; 428/701; 427/419.7; 428/469; 427/419.2; 407/119 |
Current CPC
Class: |
C23C
16/403 (20130101); C23C 16/56 (20130101); C23C
30/005 (20130101); Y10T 428/24975 (20150115); Y10T
407/27 (20150115); Y10T 428/265 (20150115) |
Current International
Class: |
B23B
27/14 (20060101); C23C 16/30 (20060101) |
Field of
Search: |
;51/295,307,309
;428/216,336,469,698,701,702 ;407/119
;427/255.3,419.1,419.2,419.7 |
References Cited
[Referenced By]
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JP |
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2825693 |
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Sep 1998 |
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JP |
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Other References
Trial Demand for Invalidation of Related Japanese Patent No.
3761932 dated May 22, 2007. cited by other .
Office Action in Invalidation Trial of Related Japanese Patent No.
3761932 dated Feb. 13, 2009. cited by other .
Kim, Jae-Gon et al., Effect of Partial Pressure of the Reactant Gas
on the Chemical Vapour Deposition of Al.sub.2O.sub.3 Thin Solid
Films, vol. 97, 1982, pp. 97-106. cited by other .
Nils Hedar, "Att utveckia svarvverktyg", Verkstaderna, nr. 11, Sep.
10, 1990, sid. 26, sp. 2, rad 39-52, pp. 22-26. cited by other
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Derwent's Abstract, 77-67577Y/38, abstract of JP-A-52 094813
(Mitsubishi Met. Corp. and Elec.), publication week 197738. cited
by other .
Patent Abstracts of Japan, vol. 13, No. 252, M-836, abstract of
JP-A-01 58402 (Daijietsuto Kogyo K.K.), published Mar. 6, 1989.
cited by other .
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Primary Examiner: Speer; Timothy M
Attorney, Agent or Firm: Drinker Biddle & Reath LLP
Parent Case Text
.Iadd.CROSS-REFERENCES TO RELATED APPLICATIONS
This application is a reissue of U.S. Pat. No. 5,861,210, which
claims the benefit of priority to Swedish Application No. 9402543-4
filed Jul. 20, 1994. .Iaddend.
Claims
What is claimed is:
1. A cutting tool insert made of cemented carbide, titanium based
carbonitride or ceramics having an improved resistance to smearing
of the workpiece material on the cutting edge comprising a body of
generally polygonal or round shape having an upper face, an
opposite face and at least one clearance face intersecting said
upper and lower faces to define a cutting edge, said insert being
at least partly coated with at least two refractory layers of which
one is a fine-grained .alpha.-Al.sub.2O.sub.3-layer and the other
is an MeC.sub.xN.sub.yO.sub.z-layer where Me is a metal selected
from the group consisting of the metals in the Groups IVB, VB and
VIB of the Periodic Table and (x+y+z)=1, said Al.sub.2O.sub.3-layer
being the top layer along the cutting edge-line .Iadd.and on the
upper face .Iaddend.and said MeC.sub.xN.sub.yO.sub.z-layer being
the top layer on the clearance face.
2. The cutting tool insert of claim 1 wherein said
.alpha.-Al.sub.2O.sub.3-layer has a texture in the (012)-direction
or (104)-direction.
3. The cutting tool insert of claim 1 wherein Me is Ti or Zr.
4. The cutting tool insert of claim 3 wherein the layer on the
clearance face is TiN, ZrN, TiCN or TiC.
5. The cutting tool insert of claim 1 wherein a fine-grained
.alpha.-Al.sub.2O.sub.3 layer is present between the body and the
MeC.sub.xN.sub.yO.sub.z layer on the clearance face.
6. The cutting tool insert of claim 1 wherein the Al.sub.2O.sub.3
thickness is 2-12 .mu.m.
7. A method of making a cutting tool insert comprising a body of
generally polygonal or round shape having an upper face, an
opposite face and at least one clearance face intersecting said
upper and lower faces to define a cutting edge, said body made of
cemented carbide, titanium based carbonitride or ceramics
comprising coating said insert at least partially with at least two
refractory layers of which the next outermost is a fine-grained
.alpha.-Al.sub.2O.sub.3-layer and a top
MeC.sub.xN.sub.yO.sub.z-layer where Me is a metal selected from the
group consisting of metals in the groups IVB, VB, VIB of the
Periodic Table and (x+y+z)=1 and removing said top
MeC.sub.xN.sub.yO.sub.z-layer .[.at least.]. along the cutting
edge-line .Iadd.and on the upper face, .Iaddend.leaving said layer
essentially untouched on the clearance face.
8. The method of claim 7 wherein said top layer is removed by
brushing with a brush containing SiC or by blasting with
Al.sub.2O.sub.3-grits.
9. The method of claim 7 wherein said .alpha.-Al.sub.2O.sub.3-layer
has a texture in the (012)-direction or (104)-direction.
10. The method of claim 7 wherein Me is Ti or Zr.
11. The method of claim 10 wherein said
MeC.sub.xN.sub.yO.sub.z-layer comprises TiN, ZrN, TiCN or TiC.
12. The method of claim 7 wherein said
.alpha.-Al.sub.2O.sub.3-layer thickness is 2-12 .mu.m.
.Iadd.13. The method of claim 7 wherein said
.alpha.-Al.sub.2O.sub.3-layer has a texture in the (012)-direction
or (104)-direction and wherein Me is Ti or Zr. .Iaddend.
.Iadd.14. The method of claim 13 wherein the
MeC.sub.xN.sub.yO.sub.z layer is TiN, ZrN, TiCN or TiC.
.Iaddend.
.Iadd.15. The method of claim 14 wherein the Al.sub.2O.sub.3
thickness is 2-12 .mu.m. .Iaddend.
.Iadd.16. The method of claim 14 wherein said upper layer is
removed by blasting with Al.sub.2O.sub.3- grits. .Iaddend.
.Iadd.17. The cutting tool insert of claim 1 wherein said
.alpha.-Al.sub.2O.sub.3-layer has a texture in the (012)-direction
or (104)-direction and wherein Me is Ti or Zr. .Iaddend.
.Iadd.18. The cutting tool insert of claim 17 wherein the layer on
the clearance face is TiN, ZrN, TiCN or TiC. .Iaddend.
.Iadd.19. The cutting tool insert of claim 18 wherein a
fine-grained .alpha.-Al.sub.2O.sub.3-layer is present between the
body and the MeC.sub.xN.sub.yO.sub.z layer on the clearance face.
.Iaddend.
.Iadd.20. The cutting tool insert of claim 19 wherein the
Al.sub.2O.sub.3 thickness is 2-12 .mu.m. .Iaddend.
.Iadd.21. The cutting tool insert of claim 1 wherein the
Al.sub.2O.sub.3-layer is the top layer on substantially the whole
upper face. .Iaddend.
.Iadd.22. The method of claim 7 wherein the
MeC.sub.xN.sub.yO.sub.z-layer is removed from substantially the
whole upper face. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The presently claimed invention relates to an
Al.sub.2O.sub.3-coated cutting tool suitable for machining of
metals by turning, milling, drilling or by similar chipforming
machining methods.
Modern high productivity chipforming machining of metals requires
reliable tools with excellent wear properties. This has so far been
achieved by employing a cemented carbide tool body coated with a
wear resistant coating. The cemented carbide tool body is generally
in the shape of an indexable insert clamped in a tool holder.
The most commonly used wear resistant layers are TiC, TiN, and
Al.sub.2O.sub.3. Both single layer and multilayer coatings are
employed. CVD, PVD or similar coating techniques are used for
depositing the different layers onto the cemented carbide body.
During the past five to ten years, coated cemented carbide tools
have been improved considerably with respect to reliability and
tool life.
During, e.g., a turning and cutting operation, the coated tool is
worn continuously on its rake face by the formed metal chip which
causes crater wear. The machined workpiece also slides along the
clearance face of the tool causing flank wear.
During high speed cutting, the tool edge may reach a very high
temperature at the rake face. This leads to a diffusion type crater
wear on the rake face of the tool. On the clearance face of the
tool, the temperature is significantly lower mainly so that
abrasive type wear occurs.
It is generally accepted that an Al.sub.2O.sub.3-layer performs
best on the rake face due to its excellent ability to withstand
diffusion type wear. Layers of the type MeC.sub.xN.sub.yO.sub.z,
where Me is a metal selected from the group consisting of the
Groups IVB, VB, and VIB of the Periodic Table, generally Ti and
where (x+y+z)=1, which type is hereafter denoted by
TiC.sub.xN.sub.yO.sub.z, generally performs better on the clearance
face. Al.sub.2O.sub.3-layers on the other hand, wear relatively
fast on the clearance face and develop flank wear relatively
quickly on that face. The flank wear will be particularly large for
thick, >4 .mu.m, Al.sub.2O.sub.3-layers. Flank wear influences
the machined surface and may therefore limit tool life. For
TiC.sub.xN.sub.yO.sub.z-type layers, the situation is almost the
reverse, that is, they exhibit low flank wear and faster crater
wear than Al.sub.2O.sub.3.
It is desirable to have a tool with high wear resistance on both
the clearance face and on the rake face at the same time.
Other factors influencing cutting performance of a coated tool
include spalling or flaking of the coatings. Flaking accelerates
tool wear, in particular the flank wear. Flaking may be the result
of inferior coating adhesion or it may be due to the smearing or
welding of workpiece material onto the cutting edge and a
successive withdrawal of the coating. This may occur when the
adhesion strength between the chip formed and the coating material
is sufficiently high.
Some steels are more difficult to machine than others due to
smearing and resulting flaking, for example, stainless steel and
low carbon steel.
Nowadays, less machining per each component is needed. The
requirements for high surface finish of the machined component only
allow tools with a clean smooth cutting edge-line with very little
developed wear to be used. It is becoming more and more difficult
for the machine operator by the naked eye to differentiate between
a little used and an unused cutting edge ("edge identification").
This is particularly difficult if the top layer is Al.sub.2O.sub.3
which color is dark grey or black. By mistake, using a used tool
cutting edge, e.g., during an unmanned night shift run may cause
component rejection or even unwanted production stops. Edge
identification can more easily be done if the insert has a top
layer of TiC.sub.xN.sub.yO.sub.z or in particular if the top layer
is a goldish TiN-, ZrN- or HfN-layer.
In U.S. Pat. No. 4,643,620, the coating thickness is reduced along
the edge by a mechanical treatment such as brushing, lapping or
barrel polishing. The object is mainly to reduce the coating
thickness along the cutting edge which is claimed to improve the
toughness behavior of the cutting tool.
U.S. Pat. No. 4,966,501 discloses a method of reducing edge damages
during cutting by reducing the coated surface roughness by
employing a mechanical polishing, lapping or brush honing. This
method is according to the findings of the present inventors not
sufficient to minimize smearing.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to avoid or alleviate the
problems of the prior art.
It is further an object of this invention to provide improvements
in coated bodies with respect to the tendency of smearing/welding
of workpiece material onto the cutting edge, cutting edge flaking
resistance, simultaneous high resistance to crater and flank wear
and to make "used edge identification" possible.
In one aspect of the invention there is provided a cutting tool
insert made of cemented carbide, titanium based carbonitride or
ceramics comprising a body of generally polygonal or round shape
having an upper face, an opposite face and at least one clearance
face intersecting said upper and lower faces to define a cutting
edge, said insert being at least partly coated with at least two
refractory layers of which one is a fine-grained
.alpha.-Al.sub.2O.sub.3-layer and the other is an
MeC.sub.xN.sub.yO.sub.z-layer where Me is a metal selected from the
group consisting of metals in the Groups IVB, VB and VIB of the
Periodic Table and (x+y+z)=1, said Al.sub.2O.sub.3-layer being the
top layer along the cutting edge-line and said
MeC.sub.xN.sub.yO.sub.z-layer being the top layer on the clearance
face.
In another aspect of the invention there is provided a method of
making a cutting tool insert comprising a body of generally
polygonal or round shape having an upper face, an opposite face and
at least one clearance face intersecting said upper and lower faces
to define a cutting edge, said body made of cemented carbide,
titanium based carbonitride or ceramics comprising coating said
insert at least partially with at least two refractory layers of
which the next outermost is a fine-grained
.alpha.-Al.sub.2O.sub.3-layer and a top
MeC.sub.xN.sub.yO.sub.z-layer where Me is a metal selected from the
group consisting of metals in the Groups IVB, VB, VIB of the
Periodic Table and (x+y+z)=1 removing said top
MeC.sub.xN.sub.yO.sub.z-layer at least along the cutting edge-line
leaving said layer essentially untouched on the clearance face.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is illustrated by FIGS. 1A-1G which show the surface
condition after different post treatments.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE
INVENTION
The inventors have made great efforts to find means to reduce the
smearing of workpiece material onto the cutting edge in order to
improve edge flaking and flank wear resistance. It has been found
by comparative cutting tests with different top layers that
Al.sub.2O.sub.3 is less prone to smearing than layers of the type
TiC.sub.xN.sub.y0.sub.z. In particular, fine-grained smooth
.alpha.-Al.sub.2O.sub.3 is very suitable as a coating material
along the cutting edge in order minimize smearings and thereby
reduce the risk of edge-line flaking.
The fine-grained .alpha.-Al.sub.2O.sub.3 layers may, e.g., be any
of the types disclosed in U.S. patent Ser. Nos. 08/159,217 (our
reference: 024000-993) and 08/366,107 (our reference: 024444-093)
or most likely also any other fine-grained
.alpha.-Al.sub.2O.sub.3-layer with other preferred growth
direction.
Although tools with a top layer of a fine-grained
.alpha.-Al.sub.2O.sub.3, such as described in the above patent
applications have excellent cutting properties they do not always
comply with today's requirements since they, e.g., suffer from the
following drawbacks: "used edge identification" is difficult with
the naked eye high initial flank wear is generally obtained for
tools with Al.sub.2O.sub.3 top layers >4 .mu.m.
As mentioned above, edge identification and improved flank wear can
be obtained by applying a top layer of TiC.sub.xN.sub.yO.sub.z.
However, such a top layer will severely increase smearing along the
edge-line when machining the difficult materials mentioned
above.
The inventors have solved this problem by mechanically removing the
TiC.sub.xN.sub.yO.sub.z-layer either from only the cutting
edge-line or from both the rake face and the cutting edge-line.
By employing this method and keeping the
TiC.sub.xN.sub.yO.sub.z-layer intact on the clearance face, several
requirements have been fulfilled simultaneously: excellent wear
resistance simultaneously on the rake face and on the clearance
face; excellent flaking resistance; and easily identifiable used
cutting edges.
According to the presently claimed invention, there now exists a
cutting tool insert comprising a body of generally polygonal or
round shape having an upper face, an opposite face and at least one
clearance face intersecting said upper and lower faces to define
cutting edges made of cemented carbide, titanium based carbonitride
or ceramics. The insert is at least partly coated with at least two
refractory layers. One is a fine-grained, grain size 0.5-4.0 .mu.m,
preferably 0.5-2.0 .mu.m, .alpha.-Al.sub.2O.sub.3-layer being the
top layer along the cutting edge-line and the other is a
TiC.sub.xN.sub.yO.sub.z- or a ZrC.sub.xN.sub.y-cutting-layer,
preferably a TiN-, ZrN-, TiCN- and/or TiC-layer being the top layer
on the clearance face. The .alpha.-Al.sub.2O.sub.3-layer preferably
has a texture in the (012)-direction or (104)-direction. A Texture
Coefficient, TC, can be defined as:
.function..function..function..times..times..function..function.
##EQU00001## where I(hkl)=measured intensity of the (hkl)
reflection. I.sub.0(hkl)=standard intensity of the ASTM standard
powder pattern diffraction data. n=number of reflections used in
the calculation, (hkl) reflections used are: (012), (104), (110),
(113), (024), (116).
According to the invention, TC for the set of (012) crystal planes
is larger than 1.3, preferably larger than 1.5, and for the set of
(104) crystal planes TC is larger than 1.5, preferably larger than
2.5, and most preferably larger than 3.0.
The .alpha.-Al.sub.2O.sub.3-layer has a thickness of 2-12 .mu.m,
preferably 4-8 .mu.m. The other layer has a thickness of 0.1-5
.mu.m, preferably 1-4 .mu.m. The total thickness of the coating
including also other layers is <20 .mu.m.
According to the method of the presently claimed invention, a
cutting tool insert made of cemented carbide, titanium based
carbonitride or ceramics is at least partly coated with at least
two refractory layers of which the next outermost layer is a
fine-grained .alpha.-Al.sub.2O.sub.3-layer and the outermost is a
MeC.sub.xN.sub.y0.sub.z-layer, where Me is a metal selected from
the group consisting of metals in the groups IVB, VB, VIB of the
Periodic Table, preferably Ti or Zr. This top
MeC.sub.xN.sub.yO.sub.z-layer is removed along the cutting
edge-line or on the cutting edge-line as well as the rake face
leaving said layer essentially untouched on the clearance face.
The methods used to remove the layer can be: brushing with a brush
with straws containing, e.g., SiC or other grinding media,
polishing with diamond paste, controlled directed blasting with,
e.g., Al.sub.2O.sub.3-powders with or without masking off the
clearance face. Also combinations of these methods are
possible.
The aim of the mechanical treatment in the presently claimed
invention is as mentioned to remove the top
TiC.sub.xN.sub.yO.sub.z-layer and expose the fine-grained
.alpha.-Al.sub.2O.sub.3 layer along the edge or also the entire
rake face. A reduction of coating thickness along the edge-line is
not desired. The used mechanical method should be so gentle that
only the top TiC.sub.xN.sub.yO.sub.z-layer is removed leaving the
Al.sub.2O.sub.3 at the edge-line as untouched as possible.
The invention is additionally illustrated in connection with the
following Examples which are to be considered as illustrative of
the presently claimed invention. It should be understood, however,
that the invention is not limited to the specific details of the
Examples.
EXAMPLE 1
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 5.5% Co, 8.6% cubic carbides (TiC-TaC-NbC) and balance
WC were coated with CVD-technique according to the following
sequence: 0.7 .mu.m TiC, 0.5 .mu.m Ti(CO), 8.0 .mu.m Ti(CN), 3.0
.mu.m Al.sub.2O.sub.3 and 2.8 .mu.m TiN.
The Al.sub.2O.sub.3-layer was deposited with a method that gives a
fine-grained .alpha.-Al.sub.2O.sub.3 layer according to U.S. Ser.
No. 08/159,217 (our reference: 024000-993). The TiN-layer was
deposited at 400 mbar and the other layers according to prior art
techniques.
The coated inserts were post treated with different methods
according to below:
Variant 1A: No post treatment.
Variant 1B: Wet blasting with 150 mesh Al.sub.2O.sub.3-grits at 1.0
bar.
Variant 1C: Wet blasting with 150 mesh Al.sub.2O.sub.3-grits at 1.5
bar.
Variant 1D: Wet blasting with 150 mesh Al.sub.2O.sub.3-grits at 2.0
bar.
Variant 1E: Wet blasting with 325 mesh Al.sub.2O.sub.3-grits at 2.0
bar.
Variant 1F: Brushing with a cylindrical nylon brush containing
SiC.
Variant 1G: As 1F but with the center of the brush closer to the
insert in order to get more efficient treatment.
The different treatments resulted in different degrees of thinning
and smoothness of the outer TiN-layer:
Variant 1B: A much smoother surface than 1A. The TiN-layer covering
the whole surface of the insert.
Variant 1C: A much smoother surface than 1A. The TiN-layer covering
the whole surface of the insert.
Variant 1D: A much smoother surface than 1A. The TiN-layer is
removed along the whole edge-line exposing the
Al.sub.2O.sub.3-layer.
Variant 1E: As 1B.
Variant 1F: A much smoother surface than 1A. The TiN-layer covering
the whole surface of the insert.
Variant 1G: A much smoother surface than 1A. The TiN layer is
removed along the whole edge-line exposing the
Al.sub.2O.sub.3-layer.
The surface condition of the variants is illustrated by FIGS.
1A-1G.
EXAMPLE 2
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 5.5% Co, 8.6% cubic carbides (TiC-TaC-NbC) and balance
WC were coated with CVD-technique according to the following
sequence: 0.6 .mu.m TiC, 0.4 .mu.m Ti(CO), 8.1 .mu.m Ti(CN), 8.1
.mu.m on Al.sub.2O.sub.3 and 0.9 .mu.m TiN.
The Al.sub.2O.sub.3-layer was deposited with a method that gives a
fine-grained .alpha.-Al.sub.2O.sub.3 layer according to U.S. Ser.
No. 08/159,217 (our reference: 024000-993). The TiN-layer was
deposited at 400 mbar and the other layers according to prior art
techniques.
The coated inserts were post treated with different methods
according to below:
Variant 2A: No post treatment.
Variant 2B: Wet blasting with 150 mesh Al.sub.2O.sub.3-grits
resulting in a smoother surface. Here the top TiN-layer was removed
along the edge-line as well as on the whole rake face exposing the
black Al.sub.2O.sub.3-layer.
Variant 2C: Brushing with a cylindrical SiC-containing nylon brush.
This treatment resulted in a smooth surface with only the top
TiN-layer removed along the edge-line exposing the
Al.sub.2O.sub.3.
EXAMPLE 3
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 5.5% Co, 8.6% cubic carbides (TiC-TaC-NbC) and balance
WC were coated with CVD-technique according to the following
sequence: 1.0 .mu.m TiC, 0.4 .mu.m Ti(CO), 7.9 .mu.m Ti(CN) and 5.5
.mu.m Al.sub.2O.sub.3.
The Al.sub.2O.sub.3-layer was deposited with a method that gives a
fine-grained .alpha.-Al.sub.2O.sub.3 layer according to U.S. Ser.
No. 08/159,217 (our reference: 024000-993).
The inserts were treated by wet blasting with 150 mesh
Al.sub.2O.sub.3-grits (Variant 3).
EXAMPLE 4
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 6.5% Co, 8.7% cubic carbides (TiC-TaC-NbC) and balance
WC and with a 25 .mu.m thick binder phase enriched zone were coated
with CVD-technique according to the following sequence: 7.9 .mu.m
TiC, 4.2 .mu.m Al.sub.2O.sub.3 and 3.5 .mu.m TiC.
The Al.sub.2O.sub.3-layer was deposited with a method that gives a
fine-grained .alpha.-Al.sub.2O.sub.3-layer according to U.S. Ser.
No. 08/159,217 (our reference: 024000-993).
Variant 4A: No post treatment.
Variant 4B: The inserts were brushed with a cylindrical
SiC-containing nylon brush, resulting in a smooth surface exposing
the Al.sub.2O.sub.3-layer along the whole edge-line.
EXAMPLE 5
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 6.5% Co, 8.7% cubic carbides (TiC-TaC-NbC) and balance
WC and with a 25 .mu.m thick binder phase enriched surface zone
were coated with CVD-technique according to the following sequence:
7.0 .mu.m TiC and 5.1 .mu.m Al.sub.2O.sub.3.
The Al.sub.2O.sub.3-layer was deposited with a method that gives a
fine-grained .alpha.-Al.sub.2O.sub.3 layer according to U.S. Ser.
No. 08/159,217 (our reference: 024000-993).
The inserts were treated by wet blasting with 150 mesh
Al.sub.2O.sub.3-grits (Variant 5).
EXAMPLE 6
Cemented carbide cutting inserts CNMG 120408-QM with the
composition 6.5% Co, 8.7% cubic carbides (TiC-TaC-NbC) and balance
WC and with a 25 .mu.m thick binder phase enriched surface zone
were coated with CVD-technique according to the following sequence:
5.4 .mu.m Ti(CN), 5.3 .mu.m Al.sub.2O.sub.3 and 1.3 .mu.m TiN.
The Al.sub.2O.sub.3-layer was deposited according to prior art
technique resulting in a layer of mixed .alpha.- and
.kappa.-polymorphs. The TiN-layer was deposited at 400 mbar and the
other layers according to prior art techniques.
Variant 6A: Not post treated.
Variant 6B: Wet blasting with 150 mesh Al.sub.2O.sub.3-grits
resulting in a smoother surface and the top TiN-layer removed along
the edge-line as well as on the whole rake face exposing the
Al.sub.2O.sub.3.
Variant 6C: Brushing with a cylindrical SiC-containing nylon brush
resulting in a smooth surface and exposing the
Al.sub.2O.sub.3-layer along the whole edge-line.
EXAMPLE 7
Tool inserts from examples 1-6 were tested with respect of
edge-line flaking in a facing operation in an alloyed steel (AISI
1518, W-no. 1,0580). The shape of the workpiece was such that the
cutting edge was intermitted three times during each revolution.
Cutting data: Cutting speed: 130-220 m/min Feed: 0.2 mm/rev Depth
of cut: 2.0 mm
The inserts were run one cut over the workpiece. The results below
are expressed as percentage of the edge-line in cut that obtained
flaking of the coating.
TABLE-US-00001 % Edge Line Flaking Variant Post Treatment
Al.sub.2O.sub.3 Exposed at edge 1A None No 63 1B Blasted No 80 1C
Blasted No 84 1D Blasted Yes 18 1E Blasted No 70 1F Brushed No 66
1G Brushed Yes 0 2A None No 57 2B Blasted Yes 0 2C Brushed Yes 0 3
Blasted Yes 0 4A None No 87 4B Brushed Yes 0 5 Blasted Yes 0 6A
None No 83 6B Blasted Yes 27 6C Brushed Yes 33
As can be seen from above, the best results have been obtained when
the fine-grained .alpha.-Al.sub.2O.sub.3-layer has been exposed at
the edge-line. Post treatment resulting in a smoother coating
surface but not exposure of the .alpha.-Al.sub.2O.sub.3 does not
result in any improvement of the flaking resistance. Variants 6B
and 6C with the .alpha./.kappa.-polymorphs exposed at the edge-line
do not obtain as good flaking resistance as the Variants with
.alpha.-Al.sub.2O.sub.3-layer exposed at the edge-line.
EXAMPLE 8
Cutting inserts from Examples 4 and 5 were run in longitudinal
turning of a ball bearing steel SKF 25B. Cutting data: Cutting
speed: 180 m/min Feed: 0.36 mm/rev Depth of cut: 2,0 mm, coolant
was used
The flank wear was measured after 2.5 min in order to study the
initial wear.
TABLE-US-00002 Variant Flank Wear, mm 4B 0.13 5 0.20
This Example illustrates the improved flank wear resistance due to
the top TiC layer on the flank face.
The principles, preferred embodiments and modes of operation of the
presently claimed invention have been described in the foregoing
specification. The invention which is intended to be protected
herein, however, is not to be construed as limited to the
particular forms disclosed, since these are to be regarded as
illustrative rather than restrictive. Variations and changes may be
made by those skilled in the art without departing from the spirit
of the invention.
* * * * *