Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Including a second component containing structurally defined...
Reexamination Certificate
1999-11-05
2001-12-25
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Including a second component containing structurally defined...
C428S336000, C428S469000, C428S697000, C428S698000, C428S699000, C428S701000, C428S702000, C051S307000, C051S309000, C407S119000
Reexamination Certificate
active
06333103
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aluminum oxide-coated article suitable for tools, dies and metal melt-contacting members with excellent cutting properties, wear resistance, durability, etc.
DESCRIPTION OF PRIOR ART
Coated tools are generally produced by forming thin, hard layers on surfaces of substrates made of cemented carbides, high-seed steel or specialty steel by a chemical or physical deposition method. The coated tools have both good wear resistance derived from coating layers and good toughness derived from tool substrates, thus being widely used in various applications. Particularly when high-seed steel bodies are cut with tools at high speeds, tip ends or edges of cutting tools are subjected to temperature elevation to about 1000° C., and at such a high temperature the coated tools should be resistant to wear by contact with the high-seed steel bodies or mechanical impact caused by intermittent cutting, etc. Accordingly, coated tools with excellent wear resistance, toughness, impact resistance and durability are highly desired.
Used widely for hard coatings for tools are non-oxide coatings composed of carbides, nitrides or carbonitrides of metals in Groups IVa, Va and VIa of the Periodic Table, and oxidation-resistant oxide coatings, and these coatings may be constituted by a single layer or a plurality of layers. Used for the non-oxide coatings are titanium carbide, titanium nitride, titanium carbonitride, and used for the oxide coatings are particularly &kgr;-aluminum oxide, &agr;-aluminum oxide, etc. Non-oxide coatings made of carbides, nitrides or carbonitrides are poor in oxidation resistance, and to obviate this defect an oxide layer made of aluminum oxide with excellent oxidation resistance is generally formed.
However, a multilayer coating structure consisting of at least one non-oxide layer and at least one oxide layer is disadvantageous in that adhesion is poor between the non-oxide layer and the oxide layer, and that such a multi-layer coating does not exhibit stable mechanical strength at high temperatures.
When &kgr;-aluminum oxide is used for the oxide layer, it exhibits relatively good adhesion to the non-oxide layer and can be coated at relatively low temperatures of 1000-1020° C. to provide layers with relatively small crystal grain sizes. However, because &kgr;-aluminum oxide is a metastable aluminum oxide, it is transformed to &agr;-aluminum oxide at high temperatures, causing volume change. Therefore, when used for cutting tools, etc., the &kgr;-aluminum oxide layer suffers from cracking due to temperature elevation, thus failing to have enough resistance to peeling.
On the other hand, &agr;-aluminum oxide is stable without change in crystal grain sizes at high temperatures, exhibiting excellent high-temperature stability. However, the &agr;-aluminum oxide layer should be formed at higher temperatures than the &kgr;-aluminum oxide layer, resulting in increase in crystal grain sizes, which leads to the unevenness of cutting properties in the &agr;-aluminum oxide-coated tools.
Chul-Soon et al discussed the relations between the crystal orientation of &agr;-aluminum oxide and its crystal structure. See “The Effect of Reaction Condition on the Crystallographic Orientation and Surface Morphology of Chemical Vapor Deposited Al
2
O
3
,” Proc. 4
th
Euro. Conf. CVD (1983), pp. 410-420. To evaluate the relations of the crystal orientation of &agr;-aluminum oxide with coating conditions, Chul-Soon et al. defined a texture coefficient TC (hkl) as shown in the equation (1) below as a parameter showing the crystal orientation of &agr;-aluminum oxide,
TC (hkl)={I (hkl)/I
0
(hkl)}/[&Sgr;{(hkl)/I
0
(hkl)}8] (1),
wherein (hkl)=(012), (104), (110), (113), (024), (116), (124) and (030), I (hkl) is the measured intensity of X-ray diffraction from a (hkl) plane of an &agr;-Al
2
O
3
layer, and I
0
(hkl) is the standard intensity of X-ray diffraction described in ASTM file No. 10-173 (Powder Diffraction File Published by JCPDS International Center for Diffraction Data).
TC (hkl) defined by the equation (1) indicates a relative intensity of the X-ray diffraction measured on a (hkl) plane of the &agr;-Al
2
O
3
layer. The fact that TC (hkl) is large means that an X-ray diffraction peak ratio expressed by I (hkl)/I
0
(hkl) is larger than the average of all peaks expressed by &Sgr;{I (hkl) I
0
(hkl)}/8. Thus, the larger the TC (hkl) is, the higher the X-ray diffraction peak ratio from the (hkl) plane is than the other peak ratios, namely, the more the (hkl) plane is oriented in a tangent direction of the substrate.
Chul-Soon et al. reported that when an &agr;-aluminum oxide layer is formed by using an AlCl
3
gas, a CO
2
gas and an H
2
gas after the formation of a TiN layer on a surface of a cemented carbide substrate, the texture coefficient TC (hkl) from a (012) plane to a (030) plane is substantially as uniform as 0.91-1.13 at a layer-forming temperature of 1000° C., indicating that the crystal is substantially uniformly oriented. They also reported that as the layer-forming temperature is elevated from 1000° C. to 1050° C., to 1100° C. and to 1150° C., the orientation in (104) and (116) planes increases, and that as the ratio of an AlCl
3
gas increases, the orientation of the (104) plane is intensified. However, Chul-Soon et al. failed to describe the X-ray diffraction intensity of the (1 0 10) plane at all, suggesting that the measured intensity of X-ray diffraction of the (1 0 10) plane was too small to be discussed. Also, according to the article of Chul-Soon et al., the texture coefficient TC (hkl) and the layer surface structure are separately described, without any reference to their correlations.
With respect to the correlations between the crystal orientation of &agr;-aluminum oxide layers and the cutting properties of tools coated with such &agr;-aluminum oxide layers, Japanese Patent laid-Open No. 5-295517 proposes an alumina-coated cemented carbide body produced by coating a cemented carbide substrate with a TiCN layer and an &agr;-Al
2
O
3
layer having a texture coefficient TC (104) of more than 1.5 in the same coating process. Also, Japanese Patent Laid-Open No. 6-316758 proposes an alumina-coated body having an alumina layer having a texture coefficient TC (012) of more than 1.3. Further, Japanese Patent Laid-Open No. 7-216549 proposes an aluminacoated body substantially free from cooling cracks, the alumina layer having a texture coefficient TC (110) of more than 1.5. These laid-open Japanese patent applications do not include a (030) plane in the calculation of the texture coefficient TC (hkl) defined by the above equation (1). However, these laid-open Japanese patent applications fail to refer to the X-ray diffraction intensity from a (1 0 10) plane, and it may be presumed from this fact that the X-ray diffraction intensity from a (1 0 10) plane was too weak to discuss, like in the article of Chul-Soon et al.
In view of such circumstances, the inventors previously proposed an aluminum oxide-coated tool having a first coating layer and a second coating layer formed in this order on a tool substrate, the first coating layer having a single- or multi-layer structure and being made of at least one selected from the group consisting of carbides, nitrides, carbonitrides, oxides, oxycarbides, oxynitrides and oxycarbonitrides of metals in Groups IVa, Va and VIa of the Periodic Table, and the second coating layer being constituted by at least one &agr;-aluminum oxide-based oxide layer, the largest peak of equivalent X-ray diffraction being obtained from a (110) plane (Japanese Patent Laid-Open No. 10-156606). This reference does not discuss the X-ray diffraction intensity from the (1 0 10) plane, either, because it is too weak to be analyzed in this &agr;-aluminum oxide-coated tool.
OBJECT AND SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide an article such as a tool coated with aluminum oxide, crystal grains of which are so f
Gonda Masayuki
Ishii Toshio
Okayama Shirou
Shima Nobuhiko
Ueda Hiroshi
Hitachi Metals Ltd.
Sughrue & Mion, PLLC
Turner Archene
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