Coated cutting tool and method for the production thereof

Abstract

The invention relates to a method for producing a coated cutting tool in which a coating with at least one oxide layer is applied to a base layer by means of a PVD method. The method includes voltage-pulsed sputtering of at least one cathode metal selected from the group of aluminum, scandium, yttrium, silicon, zinc, titanium, zirconium, hafnium, chromium, niobium, and tantalum, as well as mixtures and alloys thereof in the presence of a reactive gas; and the depositing of at least one oxide layer formed by converting the reactive gas with the sputtered cathode metal onto the base body. The cathode metal includes at least aluminum. Dinitrogen oxide is used as the reactive gas. The at least one oxide layer is in the form of an oxide, mixed oxide, or oxide mixture of the at least one cathode metal.

Claims

1. A cutting tool with a base body and a coating, characterized in that the coating has one or more oxide layers wherein at least one oxide layer is produced according to the method comprising the steps of: voltage-pulsed sputtering of aluminum and at least one cathode metal selected from the group consisting of magnesium, aluminum, scandium, yttrium, silicon, zinc, titanium, zirconium, hafnium, chromium, niobium, tantalum, as well as mixtures and alloys thereof in the presence of a reactive gas; and depositing of at least one oxide layer formed by converting the reactive gas with the sputtered aluminum and cathode metal onto the base body, wherein dinitrogen oxide is used as the reactive gas, and wherein the at least one oxide layer is formed in the form of a mixed oxide of aluminum and the at least one cathode metal in a mixture with an oxynitride of the cathode metal, aluminum or a combination thereof.

2. The cutting tool according to claim 1, characterized in that a base coating comprising titanium aluminum nitride is applied directly to the base body.

3. The cutting tool according to claim 2, wherein the base coating contains 50 to 60 atomic % aluminum.

4. The cutting tool according to claim 1, characterized in that the at least one oxide layer comprises aluminum oxidynitride enriched with portions of the at least one cathode metal.

5. The cutting tool according to claim 1, characterized in that the coating further comprises multiple oxide layers.

6. The cutting tool of claim 5, wherein the multiple oxide layers alternate with one or more nitrides or carbon nitrides of the metals Ti, Zr, Hf, Cr, Nb, and Ta, or with titanium aluminum nitride.

7. The cutting tool according to claim 5, characterized in that the multiple oxide layers have a gradient with an aluminum content decreasing from the base body in the direction of the outermost oxide layer.

8. The cutting tool according to claim 1, characterized in that the coating has a cover layer formed from the oxide layer.

9. The cutting tool according to claim 8, characterized in that the cover layer has a coating thickness ranging from about 0.1 to about 0.5 μm.

10. The cutting tool according to claim 9, characterized in that the coating consists of a titanium aluminum nitride layer applied directly to the base body and the cover layer formed from the oxide layer.

11. The cutting tool according claim 1, wherein the at least one cathode metal is silicon.

12. The cutting tool according claim 1, wherein the at least one cathode metal is titanium.

13. The cutting tool according claim 1, wherein the at least one cathode metal is zirconium.

14. The cutting tool according claim 1, wherein the at least one cathode metal is chromium.

15. The cutting tool according to claim 1, wherein the aluminum and at least one cathode metal are present in the oxide layer at a ratio (Al:M) ranging 98:2 to 70:30.

16. The cutting tool of claim 4, wherein the aluminum oxynitride is enriched with portions of at least one other cathode metal selected from the group of consisting of Mg, Sc, Y, Si, Zn, Ti, Zr, Hf, Cr, Nb, and Ta, as well as combinations thereof.

17. A cutting tool with a base body and a coating, characterized in that the coating has one or more oxide layers wherein at least one oxide layer is produced according to the method comprising the steps of: voltage-pulsed sputtering of at least one cathode metal selected from the group consisting of magnesium, aluminum, scandium, yttrium, silicon, zinc, titanium, zirconium, hafnium, chromium, niobium, tantalum, as well as mixtures and alloys thereof in the presence of a reactive gas; and depositing of at least one oxide layer formed by converting the reactive gas with the sputtered cathode metal onto the base body, wherein the cathode metal comprises at least aluminum, wherein dinitrogen oxide is used as the reactive gas, and wherein the at least one oxide layer is formed in the form of an oxide or oxide mixture of the at least one cathode metal in a mixture with one or more oxynitrides of the cathode metal.

18. The method of claim 17, wherein the cathode metal further comprises silicon.

19. The method of claim 17, wherein the cathode metal further comprises titanium.

20. The method of claim 17, wherein the cathode metal further comprises chromium.

21. The method of claim 17, wherein the cathode metal further comprises zirconium.

Description

EXAMPLE 1

(1) In a CC800/9 sinox PVD coating system from Cemecon, a cutting tool comprising 12.2% by weight Co, 1.4% by weight TaC, 0.9% by weight NbC, and 85.5% by weight WC (P-types for milling steel) was provided with the following coating as indicated.

(2) 1. TiAlN (Ti:Al ratio of 40:60 at %) as a base coating with a coating thickness of 1.7 μm (deposited in DC voltage sputtering);

(3) 2. Aluminum oxide as an oxide layer with a coating thickness of 0.9 μm;

(4) 3. TiAlN as a cover layer with a coating thickness of about 0.1 μm;

(5) Before the coating process, the hard metal base body was cleaned in the vacuum chamber with Ar ion bombardment.

(6) The depositing of the TiAlN base coating was carried out in a known manner in DC voltage operation.

(7) The depositing of the oxide layer and the TiAlN cover layer was implemented through pulsed medium-frequency sputtering. The deposit conditions are listed in Table 1 as follows:

(8) TABLE-US-00001 TABLE 1 PVD deposit conditions TiAIN base TiAIN cover coating Al.sub.2O.sub.3 layer Duration [s] 5300 6000 500 Substrate temperature [° C.] 600 600 600 Processing pressure [mPa] 580 530 560 Cathode pulse frequency [kHz] 0 50 50 Cathode voltage [V] 370 390 330 Bias voltage [−V] 100 60 60 Ar flow rate [sccm] 500 500 500 N.sub.2O flow rate [sccm] 0 30 0 N.sub.2 flow rate [sccm] 105 0 80

(9) The coating was implemented using four cathodes, which were pulsed in bipolar operation. Two Al targets and two Ti.sub.40Al.sub.60 targets were used. The pulse frequency for both targets was about 50 kHz; the TiAl target, however, was operated only at low power in order to obtain pure aluminum oxide to the extent possible on the inserts on one hand and to prevent oxide population on the TiAl target surface on the other hand.

(10) For depositing of aluminum oxide, dinitrogen oxide was used as the reactive gas in argon with a concentration of 6% by volume. The operating point was controlled by maintaining a constant cathode voltage of about 400 V.

EXAMPLE 2

(11) To produce a cutting insert according to the prior art, a conventional PVD coating was applied to a hard metal base body according to Example 1. The coating consisted of TiAlN (Ti:Al ratio of 40:60 at %) with a coating thickness of 1.5 μm (deposited in DC voltage sputtering).

EXAMPLE 3

(12) In a CC800/9 sinox PVD coating system from Cemecon, a cutting tool comprising 6.1% by weight Co and 83.9% by weight WC (K-types for cast milling cutters) was provided with the following coating as indicated.

(13) 1. TiAlN (Ti:Al ratio of 40:60 at %) as a base coating with a coating thickness of 3.1 μm (deposited in DC voltage sputtering);

(14) 2. Aluminum oxide as an oxide cover layer with a coating thickness of 0.1 μm;

(15) The depositing of the oxide cover layer was achieved through pulsed medium-frequency sputtering similar to the conditions indicated in Table 1 but the coating duration was adapted.

EXAMPLE 4

(16) To produce a cutting insert according to the prior art, a conventional PVD coating was applied to a hard metal base body according to Example 3. The coating consisted of TiAlN (Ti:Al ratio of 45:55 at %) with a coating thickness of 4.8 μm (deposited with DC voltage sputtering).

(17) Cutting Test 1

(18) In milling tests using an M680 corner milling tool on a workpiece made of alloyed 42CrMo4 steel, cutting tools having insert shape XPHT160412 according to Example 1 were used and compared to corresponding cutting tools according to Example 2.

(19) Milling was done at a cutting speed vc of 250 m/min and a tooth feed rate fz of 0.25. The cutting depth ap was 1 mm and the cutting width ae was 20 mm. Milling was dry.

(20) A higher milling length was achieved with the cutting tools from Example 1 produced according to the invention up to the end of useful life than was achieved with the comparison tools. The end of useful life is defined by reaching a wear mark width of 0.1 mm or breaking of the cutting edge.

(21) With the tested cutting tools, the following milling lengths (average value of two milling tests in the so-called “single-tooth test”) were achieved: Example 1: 14400 mm (and 5330 mm per micrometer of coating thickness) Example 2 (TiAlN coating according to prior art): 6400 mm (and 4270 mm per micrometer of coating thickness)
Cutting Test 2

(22) In milling tests using an M680 corner milling tool on a workpiece made of GJS-700 ductile cast iron, cutting tools having insert shape XPHT160412 according to Example 3 were used and compared to corresponding cutting tools according to Example 4.

(23) Milling was done at a cutting speed vc of 250 m/min and a tooth feed rate fz of 0.25. The cutting depth ap was 2 mm and the cutting width ae was 20 mm. Milling was dry.

(24) A higher milling length was achieved with the cutting tools from Example 3 produced according to the invention up to the end of useful life than was achieved with the comparison tools. The end of useful life is defined by reaching a wear mark width of 0.2 mm or breaking of the cutting edge.

(25) With the tested cutting tools, the following milling lengths (average value of two milling tests in the so-called “single-tooth test”) were achieved: Example 3: 8500 mm (and 2800 mm per micrometer of coating thickness) Example 4 (TiAlN Coating According to Prior Art): 8250 mm (and 1700 mm per micrometer of coating thickness)

(26) The patents and other documents identified herein are hereby incorporated by reference herein. Other embodiments of the invention will be apparent to those skilled in the art from a consideration of the specification or a practice of the invention disclosed herein. It is intended that the specification and examples are illustrative only and are not intended to be limiting on the scope of the invention. The true scope and spirit of the invention is indicated by the following claims.