ALN-BASED HARD MATERIAL LAYER ON BODIES OF METAL, HARD METAL, CERMET OR CERAMICS, AND METHOD FOR THE PRODUCTION THEREOF

Abstract

The invention relates to the field of materials engineering and relates to an AlN-based hard material layer on bodies of metal, hard metal, cermet or ceramics and to a method for the production thereof. The aim of the invention is to provide an AlN hard material layer which has improved hardness and wear resistance and can be produced in an inexpensive and time-efficient manner. According to the invention, an AlN-based hard material layer is provided, which is an individual layer or a multi-layered layer system, wherein at least the one layer or at least one layer of the multi-layered layer system is an AlN-based hard material layer with a hexagonal lattice structure that has a <002> texture and is oxygen-doped, wherein the oxygen doping is in the range of 0.01 at. % to 15 at. %. The hard material layer can be used as a wear-protection layer for cutting tools.

Claims

1. An AlN-based hardcoat layer on bodies made of metal, cemented carbide, cermet or ceramic, which is an individual layer produced by CVD methods without plasma excitation or a multilayer system, wherein at least the one layer or at least one layer of the multilayer system is an AlN layer with hexagonal lattice structure having a <002> texture which is oxygen-doped, where the oxygen doping is within a range from 0.01 at % to 15 at % without direct lattice binding in the hexagonal lattice structure.

2. The hardcoat layer as claimed in claim 1, in which the texture has a texture coefficient TC of >2.5 to 8.

3. The hardcoat layer as claimed in claim 1, in which the Al content is ?45 at %.

4. The hardcoat layer as claimed in claim 1, in which the texture is in columnar form.

5. The hardcoat layer as claimed in claim 1, in which the h-AlN-based hardcoat layer has a layer thickness between 5 and 40 ?m.

6. The hardcoat layer as claimed in claim 1, in which the at least one h-AlN-based hardcoat layer is nanocrystalline.

7. The hardcoat layer as claimed in claim 6, in which the crystallite size is 5 nm to 100 nm.

8. The hardcoat layer as claimed in claim 6, in which the nanocrystalline h-AlN-based hardcoat layer has amorphous components.

9. The hardcoat layer as claimed in claim 8, in which there is oxygen doping of 0.01 at % to 25 at %.

10. The hardcoat layer as claimed in claim 1, in which the h-AlN-based hardcoat layer has doping by Zr, Si, Hf, Ta and/or Ti.

11. The hardcoat layer as claimed in claim 1, in which at least one h-AlN-based hardcoat layer has a hardness of 2500 HV [0.01] to 2800 HV [0.01].

12. The hardcoat layer as claimed in claim 1, in which there is at least one tie layer, interlayer and/or outer layer.

13. The hardcoat layer as claimed in claim 12, in which the tie layer, interlayer and/or outer layer consist(s) of nitrides, carbides, carbonitrides, oxycarbides, oxycarbonitrides of the elements of transition groups 4-6 of the PTE or of oxides of Al or Zr.

14. The hardcoat layer as claimed in claim 12, in which the tie layer, interlayer and/or outer layer is TiN, TiCN, TiAlN and/or combinations thereof.

15. A process for producing an AlN-based hardcoat layer on bodies made of metal, cemented carbide, cermet or ceramic, in which a textured, oxygen-doped h-AlN-based hardcoat layer is deposited by means of a thermal CVD method without plasma excitation in a CVD reactor from a gas phase composed of AlCl.sub.3, H.sub.2, N.sub.2, NH.sub.3, CO and/or CO.sub.2 and at temperatures between 850? C. and 1050? C. and at pressures between 0.1 kPa and 30 kPa, with supply of CO and/or CO.sub.2 separately to the CVD reactor via a separate gas supply.

16. The process as claimed in claim 15, in which NH.sub.3 is supplied separately via a separate gas supply to the CVD reactor for production of the gas phase.

17. The process as claimed in claim 15, in which a gas phase with 0.30% by volume to 2% by volume of NH.sub.3 is used.

18. The process as claimed in claim 15, in which the deposition of the h-AlN-based hardcoat layer is preceded by deposition of at least one tie layer, interlayer and/or outer layer composed of nitrides, carbides, carbonitrides, oxycarbides, oxycarbonitrides of the elements of transition groups 4-6 of the PTE or of oxides of Al or Zr.

19. The process as claimed in claim 18, in which a tie layer, interlayer and/or outer layer comprising TiN, TiCN, TiAlN and/or combinations thereof is deposited.

Description

[0050] The invention is elucidated in detail below by multiple working examples and the corresponding figures. The figures show:

[0051] FIG. 1: x-ray diffractogram of the highly textured, oxygen-doped h-AlN layer produced by CVD according to Example 1,

[0052] FIG. 2: TEM image of the highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 1

[0053] FIG. 3: TEM-EDX analysis of the highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 1

[0054] FIG. 4: x-ray diffractogram of the highly textured, oxygen-doped h-AlN-based hardcoat layer Example 2 produced by CVD

[0055] FIG. 5: TEM image of the highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 2

[0056] FIG. 6: TEM-EDX analysis of the highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 2

[0057] FIG. 7: SEM polished section image of a 40 ?m-thick highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 3

[0058] FIG. 8: EDX analysis of the highly textured, oxygen-doped h-AlN-based hardcoat layer, doped with silicon, produced by CVD according to Example 4

[0059] FIG. 9: EDX analysis of the highly textured, oxygen-doped h-AlN-based hardcoat layer, doped with zirconium, produced by CVD according to Example 5

[0060] FIG. 10: wear test on a highly textured, oxygen-doped h-AlN-based hardcoat layer according to Example 1, 4 and 5

EXAMPLE 1

[0061] A highly textured and oxygen-doped h-AlN-based hardcoat layer is deposited by a thermal CVD method without plasma excitation as outer layer on WC/Co cemented carbide indexable cutting inserts that have been precoated with a 5 ?m-thick TiN/TiCN/TiN layer system as tie layer, interlayer and outer layer. The coating process is conducted in a hot-wall CVD reactor having an internal diameter of 75 mm. The CVD coating is effected with a gas phase composed of 0.46% by volume of AlCl.sub.3, 0.31% by volume of NH.sub.3, 0.72% by volume of CO.sub.2, 4.80% by volume of N.sub.2 and 93.71% by volume of H.sub.2, The deposition temperature is 900? C. and the process pressure is 6 kPa. After a coating time of 90 min, a 5.2 ?m-thick highly textured and oxygen-doped h-AlN-based hardcoat layer is obtained.

[0062] In the x-ray crystallography layer analysis conducted, an h-AlN phase is detected, the crystallites of which have grown in highly textured manner in <002> direction. The texture coefficient TC is 7.2. TEM analyses combined with an elemental analysis according to FIG. 2 and FIG. 3 showed that the h-AlN phase is doped with 13 at % of oxygen. By means of a Vickers indenter, a microhardness of 2690 HV [0.01] was measured.

[0063] The elemental analysis in the TEM gave the following element contents: [0064] 47 at % Al, [0065] 39.5 at % N, [0066] 13 at % O, [0067] and 0.5 at % Cl.

EXAMPLE 2

[0068] A highly textured and oxygen-doped h-AlN-based hardcoat layer, which is nanocrystalline with amorphous components, is deposited by a thermal CVD method as outer layer on WC/Co cemented carbide indexable cutting inserts that have been precoated with a 5 ?m-thick TiN/TiCN/TiN layer system as tie layer, interlayer and outer layer. The coating process is conducted in a hot-wall CVD reactor having an internal diameter of 75 mm. The CVD coating is effected with a gas phase composed of 0.46% by volume of AlCl.sub.3, 0.42% by volume of NH.sub.3, 0.61% by volume of CO.sub.2, 4.68% by volume of N.sub.2 and 93.83% by volume of H.sub.2. The deposition temperature is 850? C. and the process pressure is 6 kPa. After a coating time of 90 min, a 6.0 ?m-thick highly textured and oxygen-doped h-AlN-based hardcoat layer is obtained, which is in nanocrystalline form with amorphous components.

[0069] In the x-ray crystallography layer analysis conducted, by means of the x-ray diffractogram according to FIG. 4, an h-AlN phase is detected, the crystallites of which have grown in highly textured manner in <002> direction. The texture coefficient TC is 4.2. TEM analyses combined with an elemental analysis according to FIG. 5 and FIG. 6 showed that the h-AlN phase has been doped with 24 at % of oxygen. By means of a Vickers indenter, a microhardness of 2580 HV [0.01] was measured.

[0070] The elemental analysis in the TEM gave the following element contents: [0071] 45 at % Al, [0072] 30.5 at % N, [0073] 24 at % O, [0074] and 0.5 at % Cl.

EXAMPLE 3

[0075] A highly textured, oxygen-doped h-AlN-based hardcoat layer is deposited by a thermal CVD method as outer layer on WC/Co cemented carbide indexable cutting inserts that have been precoated with a 1 ?m-thick TiN tie layer. The coating process is conducted in a hot-wall CVD reactor having an internal diameter of 75 mm. The CVD coating is effected with a gas phase composed of 0.46% by volume of AlCl.sub.3, 0.45% by volume of NH.sub.3, 0.58% by volume of CO.sub.2, 4.80% by volume of N.sub.2 and 93.71% by volume of H.sub.2. The deposition temperature is 1000? C. and the process pressure is 6 kPa. After a coating time of 150 min, a 40.0 ?m-thick highly textured and oxygen-doped h-AlN-based hardcoat layer is obtained.

[0076] In the x-ray crystallography layer analysis conducted, an h-AlN phase is detected, the crystallites of which have grown in highly textured manner in <002> direction. The texture coefficient TC is 5.4. The SEM analysis of the polished section according to FIG. 7 shows a 40 ?m-thick highly textured h-AlN-based hardcoat layer, By means of a Vickers indenter, a microhardness of 2760 HV [0.01] was measured.

EXAMPLE 4

[0077] A highly textured and oxygen-doped h-AlN-based hardcoat layer doped with silicon is deposited by a thermal CVD method as outer layer on WC/Co cemented carbide indexable cutting inserts that have been precoated with a 5 ?m-thick TiN/TiCN/TiN layer system as tie layer, interlayer and/or outer layer. The coating process is conducted in a hot-wall CVD reactor having an internal diameter of 75 mm. The CVD coating is effected with a gas phase composed of 0.46% by volume of AICl.sub.3, 0.06% by volume SiCl.sub.4, 0.31% by volume of NH.sub.3, 0.72% by volume of CO.sub.2, 4.80% by volume of N.sub.2 and 93.65% by volume of H.sub.2. The deposition temperature is 900? C. and the process pressure is 6 kPa. After a coating time of 90 min, a 4.8 ?m-thick highly textured and oxygen-doped h-AlN-based hardcoat layer doped with silicon is obtained.

[0078] In the x-ray crystallography layer analysis conducted, an h-AlN phase is detected, the crystallites of which have grown in highly textured manner in <002> direction. The texture coefficient TC is 3.7. According to FIG. 8, the EDX analysis of the polished section shows doping of the highly textured h-AlN layer with oxygen and silicon. By means of a Vickers indenter, a microhardness of 2610 HV [0.01] was measured.

EXAMPLE 5

[0079] A highly textured and oxygen-doped h-AlN-based hardcoat layer doped with zirconium is deposited by a thermal CVD method as outer layer on WC/Co cemented carbide indexable cutting inserts that have been precoated with a 5 ?m-thick TiN/TiCN/TiN layer system as tie layer, interlayer and outer layer. The coating process is conducted in a hot-wall CVD reactor having an internal diameter of 75 mm. The CVD coating is effected with a gas phase composed of 0.46% by volume of AlCl.sub.3, 0.04% by volume ZrCl.sub.4, 0.31% by volume of NH.sub.3, 0.72% by volume of CO.sub.2, 4.80% by volume of N.sub.2 and 93.67% by volume of H.sub.2. The deposition temperature is 1030? C. and the process pressure is 6 kPa. After a coating time of 90 min, a 4.5 ?m-thick highly textured and oxygen-doped h-AlN-based hardcoat layer doped with zirconium is obtained.

[0080] In the x-ray crystallography layer analysis conducted, an h-AlN phase is detected, the crystallites of which have grown in highly textured manner in <002> direction. The texture coefficient TC is 4.1. According to FIG. 9, the EDX analysis of the polished section shows doping of the highly textured h-AlN-based hardcoat layer with oxygen and zirconium. By means of a Vickers indenter, a microhardness of 2650 HV [0.01] was measured.