Vanadium aluminium nitride (VAlN) micro alloyed with Ti and/or Si

Abstract

The present invention discloses a high-temperature stable ceramic coating structure including a microalloy comprising the elements Al, V and N producible by a gas phase deposition process.

Claims

1. A high-temperature stable ceramic coating structure comprising a microalloy comprising the elements Al, V, N, Ti and Si, producible by a gas phase deposition process, wherein the microalloy comprises wurtzite AIN.

2. The coating structure according to claim 1, wherein the coating structure is formed in the form of a metastable coating structure, which is in multiphase form at least above a temperature of 900° C.

3. The coating structure according to claim 1, wherein at least the coating structure is stable above a temperature of 900° C. for longer exposure times of more than 50 hours or wherein the coating structure has a layer thickness of less than 10 μm.

4. The coating structure according to claim 1, wherein at least the coating structure is in the form of a thin film or in bulk form or wherein the coating structure is formed as a multilayer structure.

5. The coating structure according to claim 1, wherein the coating structure also comprises at least oxides or carbides in addition to nitrides.

6. The coating structure according to claim 1, wherein the microalloy further comprises cubic TiVSiN.

7. A gas phase deposition process for producing a high temperature stable ceramic coating structure according to claim 1, comprising the steps: evaporating a first target material comprising the elements Al and V; p1 evaporating a second target material comprising the elements Ti and Si; and gas phase depositing the first evaporated target material and the second evaporated target material on a suitable substrate to form to form a coating structure comprising a microalloy comprising the elements Al, V, N, Ti, and Si; and annealing the microalloy above 900° C. to thereby generating wurtzite AIN within the microalloy and produce the high temperature ceramic coating structure, wherein the annealing increases the hardness of the microalloy, increases the toughness of the microalloy, or both.

8. The gas phase deposition process according claim 7, wherein a Co-containing substrate is used.

9. The gas phase deposition process according to claim 7, wherein the substrate temperature is between 200° C. and 500° C.

10. The gas phase deposition process according to claim 7 using a reactive coating gas.

11. The gas phase deposition process according to claim 7, wherein a negative bias voltage is applied to the substrate during the coating process, wherein the bias voltage is less than 120 V.

12. The gas phase deposition process according to claim 7, wherein the coating process is formed in the form of a PVD coating process.

13. The gas phase deposition process according to claim 7, wherein a plurality of layers of a high-temperature stable ceramic coating structure including a microalloy comprising the elements Al, V and N producible by a gas phase deposition process are deposited on top of each other to form a multilayer layer structure.

14. The gas phase deposition process according to claim 7, wherein the suitable substrate is a cutting and forming tool.

15. The gas phase deposition process according claim 7, wherein the microalloy further comprises cubic TiVSiN.

Description

(1) The invention will now be described in detail on the basis of examples and with the help of the figures.

DETAILED DESCRIPTION

(2) FIG. 1 shows Hardness evolution as a function of annealing temperatures for TiN, and different TM-Al—N,

(3) FIG. 2 shows the combinatorial deposition chamber used to synthesize the inventive coating (a), the composition of the inventive coating (b), and the metallic sub-lattice composition of the inventive coating (c),

(4) FIG. 3 shows Hardness evolution as a function of annealing temperatures for the inventive c-AlVTiSiN (a), and an X-ray diffractogram of c-AlVTiSiN as a function of annealing temperatures (b).

(5) FIG. 1 shows Hardness evolution as a function of annealing temperatures for TiN, and different TM-Al—N. As shown by FIG. 1 most of the TM-Al—N such as Ti—Al—N, and Cr—Al—N, and Nb—Al—N display a hardness drop above the annealing temperature above 900° C. as shown in FIG. 1. Incontrast, the inventive micro-alloyed AlVN shows a hardness enhancement as a function of annealing temperature above 900° C. as will be shown in FIG. 3) later. This hardness behaviour was re-producible.

(6) The proposed alloy might have also an enhanced fracture toughness, caused by a higher H/E ratio especially at annealing temperatures above 900° C. and the inventive composition could as well be interesting for high temperature struc applications.

(7) FIG. 2 shows the combinatorial deposition chamber used to synthesize the inventive coating (a), the composition of the inventive coating (b), and the metallic sub-lattice composition of the inventive coating (c). According to a first embodiment, the inventive alloy is synthesized in a combinatorial approach with targets of different chemistry consisting of Al.sub.65V.sub.35, and Ti.sub.75Si.sub.25 as shown in the FIG. 2) on WC-Co substrate. Deposition details are presented below.

(8) The coating from Pos.2 in FIG. 2 has shown the claimed anomalous hardness behavior. The composition of the coating is shown in FIG. 2b and FIG. 2c.

(9) The inventive coatings from Pos.2 as well as standard c-Al.sub.66Tl.sub.34N and c-Ti.sub.75Si.sub.25N coatings are subjected to vacuum annealing experiments which are performed in an electrically heated oven with a back ground pressure of 10.sup.−5 Pa at temperatures of 800° C., 900° C., 1000° C., and 1100° C. with a soaking time of 60 minutes.

(10) The hardness of the films was measured using nanoindentation, and the structural evolution was mapped using XRD as a function of different annealing temperatures.

(11) FIG. 3 (a) shows hardness evolution as a function of annealing temperatures for the inventive c-Al.sub.64V.sub.33Ti.sub.2Si.sub.1N alloy as well as for c-Al.sub.66Ti.sub.34N and for c-Ti.sub.75Si.sub.25N.

(12) Note that for the standard c-Al.sub.66Ti.sub.34N, and c-Ti.sub.7Si.sub.25N coatings display a hardness drop at an annealing temperature above 1000° C. In contrast, for the inventive c-Al.sub.64V.sub.33Ti.sub.2Si.sub.1N coatings the hardness increases as a function of annealing temperature, which is an anomalous and not known behavior.

(13) FIG. 3 (b) shows the structural evolution of the inventive c-Al.sub.64V.sub.33Ti.sub.2Si.sub.1N coating according to the present embodiment as a function of vacuum annealing. XRD shows evolution of wurtzite AlN phase above the annealing temperature of 900° C. Indicating that the alloy undergoes the following reaction
c-Al.sub.64V.sub.33Ti.sub.2Si.sub.1N--->c-TiVSiN+w-AlN   (2)

(14) For the known TM-Al—N alloys, precipitation of w-AlN phase causes lower hardness. Surprisingly however, for the inventive coating the hardness is increasing inspite of precipitation of w-AlN.

(15) Coatings were grown in an industrial scale on an Oerlikon Innova machine using cathodic arc in a nitrogen atmosphere with a pressure of 5 Pa, a substrate temperature of 400° C., and a bias voltage of 70 V. During the arc discharge a magnetic field of Mag 14 and an arc current of 200 A resulting a burning voltage of 27 V.

(16) Though in the example the inventive coating was shown to grow by combinatorial arc depositions, the coating with same compositions could be grown by using the targets with the inventive composition in Arc, Sputtering and other related processes as thin film and bulk form.