Coated grooving or parting insert

Details Coated grooving or parting insert Coated grooving or parting insert

1999-07-08

2001-07-17

Turner, Archene (Department: 1775)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

C057S307000, C057S309000, C427S255120, C427S255290, C427S255360, C427S355000, C427S368000, C428S195100, C428S323000, C428S325000, C428S469000, C428S472000, C428S698000, C428S701000, C428S702000

Reexamination Certificate

active

06261673

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a coated cemented carbide body. The present invention further relates to a coated cutting tool insert useful for grooving or severing steel components such as steel or stainless steel tubes and bars.
BACKGROUND OF THE INVENTION
When steel or stainless steel tubes or bars are severed using an appropriate coated cutting tool or cutting tool insert, the cutting edge is frictionally heated to a high temperature with the consequence that the material being cut becomes welded onto the cutting edge of the cutting tool insert. As a result, the coating can flake and small cemented carbide chips can be torn out of the cutting tool or cutting tool insert substrate body.
On the other hand, for grooving of the same materials, a high coating wear resistance in combination with a stiff substrate material is required. Finding a cutting tool material that effectively fulfils both these requirements is a challenge.
So far it has been very difficult to improve all tool properties simultaneously. Commercial cemented carbide grades have therefore been optimised with respect to one or few of the wear types and hence to specific application areas.
Swedish patent application 9602413-8 discloses a coated cutting insert particularly suited for wet turning or grooving stainless steel components. The inserts are characterised by a cemented carbide body consisting of WC—Co and cubic carbides coated by one layer of TiC
x
N
y
O
z
with columnar grains, one layer of smooth, fine grained &kgr;—Al
2
O
3
, and preferably an outer layer of TiN.
Swedish patent application 9504304-8 discloses a coated cutting insert particularly useful for wet and dry milling of low and medium alloyed steels. The insert is characterised by a cemented carbide substrate consisting of Co—WC and cubic carbides, a coating including a layer of TiC
x
N
y
O
z
with columnar grains, a layer of smooth, fine grained &kgr;-Al
2
O
3
and preferably an outer layer of TiN.
SUMMARY OF THE INVENTION
According to the present invention, a combination of the cemented carbide substrates, coatings and insert styles has been developed which gives rise to excellent cutting performance in grooving as well as severing of steel or stainless steel.
According to the principles of the present invention, a cutting tool insert is provided which comprises:
a cemented carbide body comprising
6-15 weight % Co, 0.2-1.8 weight % cubic carbides of Ti, Ta and/or Nb, a highly W-alloyed binder phase with a CW-ratio of 0.78-0.93, and the balance WC; and
a coating comprising
a first innermost layer of TiC
x
N
y
O
z
wherein x+y+z=1, the first layer having a thickness of 0.1-1.5 &mgr;m and equiaxed grains with size<0.5 &mgr;m,
a second layer of TiC
x
N
y
O
z
wherein x+y+z=1, the second layer having a thickness of 0.4-3.9 &mgr;m, preferably 1.5-3.0 &mgr;m, with coluanar grains with an average diameter of 0.1-5.0 &mgr;m,
a third layer of a smooth fine-grained &kgr;—Al
2
O
3
layer with a thickness of 0.5-5.5 &mgr;m, and
the total thickness of the first innermost TiC
x
N
y
O
z
and the second TiC
x
N
y
O
z
layer is 0.5-4.0 &mgr;m, and the total thickness of all layers is 2.0-6.0 &mgr;m, preferably 3.0-5.0 &mgr;m.
Further according to the present invention, a method of making a cutting tool insert comprising a WC—Co-based cemented carbide body with a highly W-alloyed binder phase and a CW-ratio of 0.78-0.93, the method comprising coating the body by:
forming a first innermost layer of TiC
x
N
y
O
z
with a CVD-based technique, wherein x+y+z=1, the first layer having a thickness of 0.1-1.5 &mgr;m and equiaxed grains with a size <0.5 &mgr;m,
forming a second layer of TiC
x
N
y
O
z
by a MTCVD-technique, wherein x+y+z=1, the second layer having a thickness of 0.4-3.9 &mgr;m and columnar grains with an average diameter of 0.1-5.0 &mgr;m,
forming a third layer of a smooth &kgr;—Al
2
O
3
having a thickness of 0.5-5.5 &mgr;m, and
forming the layers such that the total thickness of the first and second layers is 0.5-4.0 &mgr;m, and the total thickness of all layers is 2.0-6.0 &mgr;m.


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patent: WO97/20083 (1997-06-01), None
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