Cutting tool made of A12O3-coated cBN-based sintered material

Details Cutting tool made of A12O3-coated cBN-based sintered material Cutting tool made of A12O3-coated cBN-based sintered material

2000-01-27

2002-01-08

Jones, Deborah (Department: 1775)

Stock material or miscellaneous articles

Composite

Of inorganic material

C428S216000, C428S336000, C428S702000, C428S704000, C051S307000, C051S309000, C501S096100, C501S096400

Reexamination Certificate

active

06337152

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cutting tool made of a cubic boron nitride (cBN) sintered material substrate coated with Al
2
O
3
. More particularly, the present invention relates to a cutting tool made of Al
2
O
3
-coated cBN-based sintered material having improved wear resistance and breakage resistance.
2. Description of the Related Art
Al
2
O
3
is a material optimum for cutting iron-based materials because of its excellent chemical stability and hardness. However, Al
2
O
3
exhibits a poor toughness. Therefore, a cutting tool mainly composed of Al
2
O
3
has a deteriorated stability against tool failure to disadvantage. In order to overcome this difficulty, a cutting tool consisting of a cemented carbide substrate having a relatively excellent toughness coated with Al
2
O
3
has been commercialized.
In recent years, there is a growing need for high speed and efficiency and dry cutting in response to the trends of environment-friendly production. In the conventional tools, however, the cemented carbide substrate deforms excessively plastically at high cutting temperature, resulting in that the coating layer easily peels off or is destroyed.
As a means for solution to the problems, a method for coating a cBN-based sintered material excellent in high temperature hardness with Al
2
O
3
has been proposed in JP-A-59-8679 (The term “JP-A” as used herein means an “unexamined published Japanese patent application”). However, since the adhesion between cBN-based sintered material and Al
2
O
3
coating layer is insufficient and the optimization of the crystallinity of Al
2
O
3
is insufficient, a remarkable enhancement of wear resistance and breakage resistance is not exhibited in cutting of hard materials such as hardened steel or high speed and efficiency cutting of steel.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a cutting tool which exhibits an excellent flank wear resistance and crater wear resistance particularly in cutting of high hardness difficult-to-cut ferrous materials or high speed and efficiency cutting of steel.
A cutting tool according to the present invention is coated with one or more Al
2
O
3
layers on at least a part of the surface of a cBN-based sintered material substrate taking part in cutting. The sintered material substrate comprises cBN in an amount of 20% to 99% by volume and Al
2
O
3
having an average crystalline particle diameter of not more than 1 &mgr;m in an amount of not less than 1.0% to less than 10% by volume. The Al
2
O
3
layer has a thickness (d) of 0.5 &mgr;m to 50 &mgr;m . The average crystalline particle diameter (s) of Al
2
O
3
is from 0.01 &mgr;m to 4 &mgr;m if the thickness (d) of the Al
2
O
3
layer is from 0.5 &mgr;m to 25 &mgr;m (0.5 &mgr;m≦d≦25 &mgr;m ), and that of Al
2
O
3
is from 0.01 &mgr;m to 10 &mgr;m if the thickness (d) of the Al
2
O
3
layer is from more than 25 &mgr;m to 50 &mgr;m (25 &mgr;m<d≦50 &mgr;m ).
The incorporation of a proper amount of Al
2
O, in a cBN-based sintered material substrate makes it possible to increase the adhesion of the Al
2
O
3
layer or interlayer made of TiC
x
N
y
O
Z
having an excellent bonding power with Al
2
O
3
, thereby enhancing the cutting properties. A particularly preferred content of Al
2
O
3
is form 3.0% to less than 5.0%. The reason why the adhesion of the Al
2
O
3
layer or interlayer can be thus increased is presumably as follows:
(1) Al
2
O
3
constituting the coating layer and TiC
x
N
y
O
Z
—
undergo nucleation with Al
2
O
3
contained in cBN-based sintered material substrate as a starting point; and.
(2) the incorporation of Al
2
O
3
in cBN-based sintered material substrate causes the residual stress characteristic to cBN-based sintered material substrate to change, thereby relaxing misfit of coating layer to residual stress (thermal stress, internal stress).
The homogeneous incorporation of fine Al
2
O
3
particles having a particle diameter of not more than 1 &mgr;m in cBN-based sintered material substrate makes it possible to accelerate the formation of fine homogenous nuclei during the formation of Al
2
O
3
or TiC
x
N
y
O
Z
—
layer and hence form an Al
2
O
3
layer having an excellent crystallinity and adhesion. If the content of Al
2
O
3
falls below 1.0% by volume, it causes uneven nucleation during the formation of coating layer, thereby exerting an insufficient effect. On the contrary, if the content of Al
2
O
3
exceeds 10% by volume, the mechanical properties inherent to Al
2
O
3
is presumably reflected in the mechanical properties of cBN-based sintered material, thereby drastically deteriorating the breakage resistance of cBN-based sintered material substrate.
The Al
2
O
3
layer is preferably mainly composed of &agr;-Al
2
O
3
. The coating of cBN-based sintered material substrate with &agr;-Al
2
O
3
with a good adhesion makes it possible to inhibit wear on relieve face and crater wear and hence drastically prolong the life of tool. The coating of cBN-based sintered material substrate with &kgr;-Al
2
O
3
with a good adhesion, too, makes it possible to inhibit crater wear and prolong the life of tool. However, wear on relieve face can be little inhibited.
Further, the Al
2
O
3
layer can be oriented on (012), (104), (110), (113), (024) or (116) plane with an orientation index of not less than 1.0 to form a coating layer excellent in wear resistance and strength. This orientation index can be defined by the following equation. The method for determining orientation index is described also in WO96/15286 (PCT/SE95/01347), etc.
TC(hkl)=I(hkl)/Io(hkl)×[(l
)&Sgr;{(hkl)/Io(hkl)}]
−1
where I(hkl): Intensity of (hkl) diffraction ray in XRD;
Io(hkl): Diffraction intensity in ASTM card of XRD; and
n: Number of diffraction rays used in calculation ((hkl) diffraction rays used are (012),(104),(110),(113),(024) and (116))
In the foregoing cutting tool, the Al
2
O
3
layer may be complexed with the TiC
x
N
y
O
Z
—
layer to form a laminate. Specific examples of the composite structure include (1) structure comprising an interlayer made of TiC
x
N
y
O
Z
—
formed on the interface of Al
2
O
3
layer with cBN-based sintered material substrate, (2) structure comprising a TiC
x
N
y
O
Z
layer provided interposed between a plurality of Al
2
O
3
layers, and (3) structure comprising a TiC
x
N
y
O
Z
—
layer provided as an outermost layer.
Referring to the reason why the thickness of the Al
2
O
3
layer is defined to a range of from 0.5 &mgr;m to 50 &mgr;m , if the thickness of the Al
2
O
3
layer falls below the lower limit, the resulting coating effect is insufficient. On the contrary, if the thickness of the Al
2
O
3
layer exceeds the upper limit, the coating layer is more liable to peeling, chipping or breakage. The thickness of the Al
2
O
3
layer is preferably from about 3 to 40 &mgr;m. In particular, if the thickness of the Al
2
O
3
layer is not more than 25 &mgr;m and the average crystal particle diameter (s) of Al
2
O
3
is from 0.01 &mgr;m to 4 &mgr;m, the resulting product is excellent in flank wear resistance. If the thickness of the Al
2
O
3
layer is more than 25 &mgr;m and the average crystal particle diameter (s) of Al
2
O
3
is from 0.01 &mgr;m to 10 &mgr;m. the resulting product is excellent in crater wear resistance. If there are a plurality of Al
2
O
3
layers, the total thickness of these Al
2
O
3
layers is used to see whether the thickness of the Al
2
O
3
layer is not more than 25 &mgr;m.
The formation of the foregoing Al
2
O
3
layer or TiC
x
N
y
O
Z
—
layer can be accomplished by CVD method such as thermal CVD method, plasma CVD method and moderate temperature CVD method or PVD method such as sputtering method and ion plating method.
On the other hand, the sintered material substrate is composed of cBN and a binder phase. If the content of cBN is not less than 20% by volume, the production of a thick binder phase which forms a mechanically weak point can be inhibited. The binder phase is preferably made of at leas

Affiliated with

Also associated with

Rating

Cutting tool made of A12O3-coated cBN-based sintered material does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Cutting tool made of A12O3-coated cBN-based sintered material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cutting tool made of A12O3-coated cBN-based sintered material will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2859756