A body such as a cutting tool coated with refractory single- or multilayers, wherein specific layers are characterized by a controlled microstructure and phase composition with crystal planes preferably grown in a preferential direction with respect to the surface of the coated body. The coating includes one or several refractory layers of which at least one layer is a dense, fine-grained layer of α-Al2O3 preferably textured in the (104) direction. The coated tool exhibits excellent surface finish and shows much improved wear and toughness properties compared to prior art objects when used for machining steel, cast iron and, particularly, when machining nodular cast iron.
REEXAMINATION RESULTS
The questions raised in reexamination proceedings Nos. 90/009,410 and 90/009,666, filed May 5, 2009 and Feb. 24, 2010 respectively, have been considered, and the results thereof are reflected in this reissue patent which constitutes the reexamination certificate required by 35 U.S.C. 307 as provided in 37 CFR 1.570(e) for ex parte reexaminations, and/or the reexamination certificate required by 35 U.S.C. 316 as provided in 37 CFR 1.997(e) for inter partes reexaminations.
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0. 18. A body at least partially coated with one or more refractory layers of which at least one layer is alumina, said alumina layer having a thickness 4 to 8 μm with an average grain size of 1 to 3 μm,
said alumina layer consisting of single phase α-structure textured in the (104)-direction with a texture coefficient larger than 3.0, the texture coefficient (TC) being defined by calculation:
where
I(hkl)=measured intensity of the (hkl) reflection
Io(hkl)=standard intensity of the ASTM standard powder pattern diffraction data
n=number of reflections used in the calculation and (hkl) reflections used are: (012), (104), (110), (113), (024), (116),
wherein the alumina layer is an exposed outermost layer in contact with an inner ticxNyOz-layer.
1. A body at least partially coated with one or more refractory layers of which at least one layer is alumina, said alumina layer having a thickness d of 0.5 μm≦d≦25 μm with a grain size (s) of
0.5 μm<s<4 μm;
said alumina layer consisting of single phase α-structure textured in the (104)-direction with a texture coefficient larger than 1.5 2.5, the texture coefficient (TC) being defined by calculation:
where
I(hkl)=measured intensity of the (hkl) reflection
Io(hkl)=standard intensity of the ASTM standard powder pattern diffraction data
n=number of reflections used in the calculation and (hkl) reflections used are: (012), (104), (110), (113), (024), (116),
said alumina layer being an exposed outermost layer in contact with a ticxNyOz-layer.
0. 23. A body at least partially coated with one or more refractory layers of which at least one layer is alumina, said alumina layer having a thickness d of 0.5 μm≦d≦25 μm with a grain size (s) of
0.5 μm<s<4 μm;
said alumina layer consisting of single phase α-structure textured in the (104)-direction with a texture coefficient larger than 3.0, the texture coefficient (TC) being defined by calculation:
where
I(hkl)=measured intensity of the (hkl) reflection
Io(hkl)=standard intensity of the ASTM standard powder pattern diffraction data
n=number of reflections used in the calculation and (hkl) reflections used are: (012), (104), (110), (113), (024), (116),
said alumina layer being an exposed outermost layer in contact with a ticxNyOz-layer,
wherein the alumina layer has been deposited by a chemical vapor deposition process wherein H2S dopant is added to reactant gases during the deposition process.
0. 21. A body at least partially coated with one or more refractory layers of which at least one layer is alumina, said alumina layer having a thickness d of 0.5 μm≦d≦25 μm with a grain size (s) of
0.5 μm<s<4 μm;
said alumina layer consisting of single phase α-structure textured in the (104)-direction with a texture coefficient larger than 3.0, the texture coefficient (TC) being defined by calculation:
where
I(hkl)=measured intensity of the (hkl) reflection
Io(hkl)=standard intensity of the ASTM standard powder pattern diffraction data
n=number of reflections used in the calculation and (hkl) reflections used are: (012), (104), (110), (113), (024), (116),
said alumina layer being an exposed outermost layer in contact with an innermost ticxNyOz-layer, and
wherein the alumina layer has a fine-grained microstructure of alumina grains with 80% or more of the alumina grains having a grain size of ±50% of an average grain size of the alumina layer.
3. A body according to
0. 4. A body according to
6. A body according to
7. A body according to
8. The coated body of
9. The coated body of
10. The coated body of
12. The coated body of
13. The coated body of
0. 14. The coated body of claim 1, wherein the texture coefficient is larger than 3.0 and the alumina layer has a fine-grained microstructure of alumina with 80% or more of the alumina grains having a grain size of ±50% of an average grain size of the alumina layer.
0. 15. The coated body of claim 1, wherein the texture coefficient is larger than 3.0 and the alumina layer has a thickness d of 0.5 μm≦d≦2.5 μm and the grain size is greater than 0.5 μm and less than 1 μm.
0. 16. The coated body of claim 1, wherein the texture coefficient is larger than 3.0 and the alumina layer has a thickness d of 2.5 μm<d<25 μm and the grain size is greater than 0.5 μm and less than 4 μm.
0. 17. The coated body of claim 16, wherein said body is a cutting tool insert of cemented carbide, titanium based carbonitride or other ceramics.
0. 19. The coated body claim 18, wherein the alumina layer has been smoothened by wet blasting.
0. 20. The coated body of claim 18, wherein the alumina layer has a fine-grained microstructure of alumina grains with 80% or more of the alumina grains having a grain size of ±50% of the average grain size of the alumina layer.
0. 22. The coated body of claim 21, wherein the alumina layer has been smoothened by wet blasting.
0. 24. The coated body of claim 23, wherein the ticxNyOz-layer is an innermost layer.
0. 25. The body according to claim 23, wherein said body is a cutting tool insert of cemented carbide, titanium based carbonitride or other ceramics.
0. 26. The coated body of claim 23, wherein the texture coefficient is larger than 3.0 and the alumina layer has a fine-grained microstructure of alumina with 80% or more of the alumina grains having a grain size of ±50% of an average grain size of the alumina layer.
0. 27. The coated body of claim 23, wherein the texture coefficient is larger than 3.0 and the alumina layer has a thickness d of 0.5 μm<d<2.5 μm and the grain size is greater than 0.5 μm and less than 1 μm.
0. 28. The coated body of claim 23, wherein the texture coefficient is larger than 3.0 and the alumina layer has thickness d of 2.5 μm<d<25 μm and the grain size is an 0.5 μm and less than 4 μm.
0. 29. The coated body of claim 23, wherein the alumina layer has been smoothened by wet blasting.
0. 30. The coated body of claim 23, wherein the thickness of the alumina layer is 4 to 8 μm and an average grain size is 1 to 3 μm.
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The textured Al2O3-coating according to the invention is obtained by careful control of the oxidation potential of the CVD-reactor atmosphere prior to the nucleation of Al2O3. The total concentration level of H2O or other oxidizing species should preferably be below 5 ppm. However, the nucleation of Al2O3 is initiated by a controlled sequencing of the reactant gases as follows: CO2 and CO are first entering the reactor in a H2 free atmosphere (e.g., in the presence of N2 or/and Ar); then, a mixture of H2 and AlCl3 is allowed into the reactor. The temperature can be 850°-1100° C., preferably 950°-1000° C., during the nucleation. However, the exact conditions depend to a certain extent on the design of the equipment used. It is within the purview of the skilled artisan to determine whether the requisite texture and coating morphology have been obtained and to modify the nucleation and the deposition conditions in accordance with the present specification, if desired, to effect the amount of texture and coating morphology.
The following examples are provided to illustrate various aspects of the invention, it being understood that the same are intended only as illustrative and in nowise limitative.
Cemented carbide cutting inserts with the composition 6.5% Co, 8.5% cubic carbides and balance WC were coated with a 5.5 μm thick layer of TiCN. In subsequent process steps during the same coating cycle, a 6 μm thick layer of α-Al2O3 was deposited. Prior to the nucleation, the oxidation potential of the hydrogen carrier gas, i.e., the water vapour concentration, was set to a low level, less than 5 ppm. For instance, see U.S. Pat. No. 5,071,696, the disclosure of which is hereby incorporated by reference.
A hydrogen-free reaction gas mixture comprising N2, CO2 and CO was first introduced into the CVD-reactor. The reaction gases were sequentially added in the given order. After a preset time, H2 and AlCl3 were allowed into the reactor. During the deposition of Al2O3, H2S was used as a dopant.
The gas mixtures and other process conditions during the Al2O3 deposition steps are set forth in Table 1.
TABLE 1
Process Condition
Step 1
Step 2
CO2:
4%
4%
AlCl3:
4%
4%
CO:
2%
—
H2S
—
0.2%
HCl
1%
4%
H2:
balance
balance
Pressure:
55 mbar
100 mbar
Temperature:
1000° C.
1000° C.
Duration:
1 hr
7.5 hr.
XRD-analysis of Sample A showed a texture coefficient, TC(104), of 3.2 of the (104) planes in the single in phase of the Al2O3 coating. SEM-studies of Sample A showed a fine-grained, 6 μm thick Al2O3-coating with an average grain size of 2.1 μm.
The cemented carbide substrate of Sample A was coated with TiCN (5.5 μm) and Al2O3 (6 μm) as set forth above except that the Al2O3 process was carried out according to a prior art technique resulting in a mixture of coarse α-and fine κ-Al2O3 grains in the coating.
Coated tool inserts from Samples A and B were all wet blasted with 150 mesh Al2O3 powder in order to smoothen the coating surface. The cutting inserts were then tested with respect to edge line and rake face flaking in a facing operation in nodular cast iron (AISI 60-40-18. DIN GGG40). The shape of the machined workpiece was such that the cutting edge is intermitted or impacted twice during each revolution.
Cutting data:
The inserts were run one cut over the face of the workpiece. The results are expressed in Table 2 as percentage of the edge line in cut that obtained flaking as well as the rake face area subjected to flaking in relation to total contact area between the rake face and the workpiece chip.
TABLE 2
Edge Line
Rake Face
Sample
Flaking (%)
Flaking (%)
A (invention)
5
6
B (comparative)
90
86
The cutting inserts from Samples A and B were also tested with respect to edge line flaking in a facing operation in an alloyed steel (AISI 1518. W-no. 10580). The shape of the machined workpiece was such that the cutting edge is intermitted or impacted three times during each revolution.
Cutting data:
The inserts were run one cut over the face of the workpiece. The results in Table 3 are expressed as percentages of the edge line in cut that obtained flaking.
TABLE 3
Sample
Edge Line Flaking (%)
A (invention)
0
(according to the invention)
B (comparative)
28
The foregoing has described the principles, preferred embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. Thus, the above-described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.
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