METHOD FOR COATING SOLID DIAMOND MATERIALS

Abstract

A method for coating solid diamond materials, to solder or bond coated diamond materials into a metallic surface or a second diamond surface under ambient air. The diamond materials are at least partially coated under a noble gas atmosphere by a vapour depositing process, the coating is performed with at least one carbide-forming chemical element selected from among B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo and W; some diamond carbon is converted into elemental carbides, which form an elemental carbide layer; and wherein there is a stoichiometric excess of the chemical element in relation to the elemental carbides formed, so an element layer is deposited onto the surface of the elemental carbide layer or a mixed elemental carbide/element layer forms and is deposited on the element layer or mixed elemental carbide/element layer. Also, a machine component, in particular a tool, with a soldered-in solid PCD.

Claims

1. A method for coating solid diamond materials in order to solder or bond the coated diamond materials into a metallic surface or a second diamond surface under ambient air; wherein the diamond materials are at least partially coated in a noble gas atmosphere by means of a vapour deposition process, wherein the coating is accomplished using at least one carbide-forming chemical element which is selected from the group consisting of: B, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; wherein a partial quantity of the diamond carbon of the diamonds contained in the surface of the diamond materials is converted into elemental carbides which form an elemental carbide layer; wherein the chemical element is present in stoichiometric excess in the molar ratio to the elemental carbides formed so that an element layer is deposited on the surface of the elemental carbide layer or a mixed elemental carbide/element layer is formed, wherein: a transition layer is deposited on the resulting element layer or mixed elemental carbide/element layer; and the transition layer comprises at least one layer which is selected from the group consisting of: boride layers, nitride layers, oxide layers as well as mixed layers thereof, carbonitride layers, oxynitride layers and/or carboxynitride layers.

2. The method according to claim 1, wherein the solid diamond materials comprise solid diamond materials of monocrystalline diamonds or polycrystalline diamonds.

3. The method according to claim 1, wherein the solid diamond materials comprise sintered-together diamond particles of polycrystalline diamonds (solid PCDs).

4. The method according to claim 3, wherein the solid PCDs contain sintering adjuvants which are selected from the group consisting of: Al, Mg, Fe, Co, Ni as well as mixtures thereof.

5. The method according to claim 3, wherein the solid diamond materials comprise solid PCDs which have a substructure of hard metal.

6. The method according to claim 5, wherein sintering adjuvants and/or the hard metal substructure are at least largely removed from the solid PCDs.

7. The method according to claim 3, wherein the sintered-together diamond particles have a mean grain size of 0.5 m to 100 m.

8. The method according to claim 1, wherein a layer which satisfies the following general formula is used as transition layer:
(E1, E2, E3 . . . Exy)x(BCNO).sub.y wherein E is an element which is selected from the group consisting of: Mg, B, Al, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W; wherein x lies in the range of 0-2 and y lies in the range of 0.5-2, and B is boron, C is carbon, N is nitrogen and O is oxygen.

9. The method according to claim 8, wherein x and y lie in the range from 0.5 to 1.1.

10. The method according to claim 1, wherein the vapour deposition process is a physical vapour deposition (PVD) process.

11. The method according to claim 1, wherein the vapour deposition process is carried out in a temperature range from 400 C. to 600 C. at a bias voltage of 0 to minus 1000 V and a pressure of 100 mPa to 10 000 mPa for a duration of 1 min to 20 min.

12. The method according to claim 1, wherein the method further comprises carrying out, after coating, a tempering step at 200 C. to 600 C. for a time between 1 min and 60 min.

13. The method according to claim 1, wherein the transition layer is also applied to the elemental carbide layer by means of PVD in a temperature range from 400 C. to 600 C., at a bias voltage of 0 to minus 1000 V and a pressure of 100 mPa to 10 000 mPa for a duration of 0.1 h to 3 h.

14. The method according to claim 1, wherein the transition layer is wetted with a solder, in an air atmosphere.

15. A coated solid PCD obtained by a method according to claim 1.

16. The solid PCD according to claim 15, wherein several solid PCDs are soldered together.

17. A method for producing a machine component with at least one functional region made of a coated solid PCD according to claim 15 as well as a metallic support body, wherein: the solid PCD is fixed on at least one surface of the metallic support body by a solder connection, wherein a hard solder is used as solder; and the solder connection between the coated solid PCD and the support body is produced at a maximum of 700 C. in an air atmosphere under normal pressure.

18. A machine component obtained by a method according to claim 17.

19. The machine component according to claim 18, wherein the machine component is a cutting tool.

20. The method according to claim 10, wherein an argon atmosphere is used as a noble gas atmosphere in the PVD process.

21. The method according to claim 14, wherein the transition layer is wetted with solder and fluxes in an air atmosphere.

22. The machine component according to claim 18, wherein the machine component is a machining tool or an asphalt or a stone milling head or a drilling head.

Description

EXAMPLE

[0048] In the present example, by coating a commercially available solid PCD body it should be possible to solder in the solid PCD bodywithout a protective gas atmosphereand therefore in an air atmosphere with the aid of a bonding layer. To this end, a surface which is readily wettable by the solder used and which also binds firmly to the diamond should be created so that the PCD-bonding layer interface does not become the weak point of the join and the tool thus produced meets all the loads and requirements on the tool and high lifetimes are achieved.

[0049] For the present exemplary embodiment four different commercially available PC D types were used.

[0050] A square plate was selected as the test sample geometry. The types of solid PCD used comprise polycrystalline diamond material which contains cobalt along with other metals.

[0051] The solid PCD test samples were tempered with several carbide-forming metals or elements, in the case of the example, titanium and zirconium and treated at a temperature of about 600 C. and a voltage bias of about 150 V in a PVD coating system. The formation of metal carbides, in the present case, TiC and ZrC was shown by means of X-ray diffractometry.

[0052] The thickness of the carbide layer was about 0.01 m measured by means of X-ray diffractometry and scanning electron microscopy.

[0053] Following the formation of the carbide layer, a boride transition layer was deposited on the elemental carbide layer by vapour deposition of elemental boron in the presence of oxygen and nitrogen by means of PVD. The conditions for the application of the transition layer were a temperature gradient of 400 C. to 600 C. which was passed through at a rate of 10 C./min and then held at 500 C. The PVD process was carried out at a bias voltage of about minus 600 V and a pressure of about 2000 mPa for a duration of 2 h.

[0054] Such coated solid PCDs were then soldered onto a hard metal plate by means of a solder alloy, in the case of the example, of AgCuZnMnNi in an ambient air atmosphere at about 700 C. and a shear test was carried out. Following the shear test a further scanning electron microscope investigation was carried out in order to assess whether cracks or ruptures occurred in the solder or in the interface and/or whether there was any damage to the diamond surface.

[0055] Here it was surprisingly found that in the course of the usual shear stress tests, no ruptures or cracks appeared in the solder layer nor in the interface to the solid PCD.

[0056] The diamond surface itself was also free from damage.