Claims
- 1. A method of coating a cutting tool body with an .alpha.-alumina coating consisting essentially of heating the cutting tool body while bringing the cutting tool body in contact with a hydrogen carrier gas to which has been added CO.sub.2, followed by CO, and than AlCl.sub.3 so as to deposit an alpha-alumina layer on the cutting tool body, wherein the oxidation potential of the hydrogen carrier gas is controlled by maintaining a content of H.sub.2 O in the carrier gas below 20 ppm of H.sub.2 O prior to nucleation of said alpha-Al.sub.2 O.sub.3.
- 2. The method of claim 1, wherein the H.sub.2 O content of the hydrogen carrier gas is below 5 ppm of H.sub.2 O prior to the nucleation of the alpha-Al.sub.2 O.sub.3 and the nucleation is carried out at a temperature of about 1000.degree. C.
- 3. The method of claim 1, wherein the alpha-alumina layer has a thickness (d) of 0.5-25 .mu.m and a single phase .alpha.-structure with a grain size (s):
- 0.5 .mu.m<s<1 .mu.m for 0.5.mu.<d<2.5 .mu.m and
- 0.5 .mu.m<s<3 .mu.m for 2.5.mu.<d<25 .mu.m.
- 4. The method of claim 1, wherein the surface roughness (R.sub.a) of the alpha-alumina layer is less than 0.3 .mu.m over a measured length of 0.25 mm.
- 5. The method of claim 1, wherein the alpha-alumina layer exhibits a texture coefficient TC greater than 1.3 for the (012) growth direction of the equivalent crystallographic planes defined as: ##EQU2## where I(hkl)=measured intensity of the (hkl) reflection
- .sub.o (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).
- 6. The method of claim 5, wherein the texture coefficient TC (012) is greater than 1.5.
- 7. The method of claim 1, wherein the cutting tool body includes an intermediate layer of a metal carbide, metal nitride or metal carbonitride, the alpha-alumina layer being deposited on the intermediate layer.
- 8. The method of claim 1, wherein the cutting tool body includes an intermediate layer of TiCN, the alpha-alumina layer being deposited on the intermediate layer.
Priority Claims (1)
Number |
Date |
Country |
Kind |
9203852 |
Dec 1992 |
SEX |
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Parent Case Info
This application is a divisional of U.S. application Ser. No. 08/159,217 filed Nov. 30, 1993, now U.S. Pat. No. 5,487,625.
US Referenced Citations (17)
Foreign Referenced Citations (5)
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Country |
32887 |
Jul 1981 |
EPX |
4110006 |
Oct 1992 |
DEX |
4110005 |
Oct 1992 |
DEX |
4131307 |
Mar 1993 |
DEX |
57-137460 |
Aug 1982 |
JPX |
Divisions (1)
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Number |
Date |
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Parent |
159217 |
Nov 1993 |
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