# US 2014/0193622 A1 · Grain Boundary Engineered Alpha-Alumina Coated Cutting Tool

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- Number: US 2014/0193622 A1
- Document ID: US20140193622A1
- Status: Published application
- Kind: A1
- Application number: 14/131,709
- Filed: 2012-09-17
- Published: 2014-07-10
- Earliest claimed: 2011-09-16
- Assignees: Walter AG
- Applicants: Walter AG
- Inventors: Dirk Stiens; Sakari Ruppi
- Web page: https://patentgrep.com/patent/US20140193622A1

## CPC

- C23C 16/403: {of aluminium, magnesium or beryllium}
- C23C 16/52: Controlling or regulating the coating process {(C23C16/45557, C23C16/279 take precedence)}
- C23C 30/005: {on hard metal substrates}
- Y10T 428/24975: No layer or component greater than 5 mils thick
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

Cutting tool insert has a substrate and a coating with a total thickness of 5 to 40 μm, the coating being one or more refractory layers of which at least one layer is an α-Al2O3 layer having thickness of 1 to 20 μm. The length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is more than 80% of the total length of the sum of grain boundaries of Σ3, Σ7, Σ11, Σ17, Σ19, Σ21, Σ23 and Σ29-type grain boundaries grain boundary character distribution measured by EBSD. The at least one α-Al2O3 layer is deposited by chemical vapour deposition (CVD) using reaction gases comprising H2, CO2, AlCl3 and X and optional additions of N2 and Ar, with X being gaseous H2S, SO2, HF, SF6 or combinations thereof. The volume ratio of CO2 and X in the CVD reaction chamber lies within the range 2<CO2/X<10.

## Claims

### Claim 1

A cutting tool insert consisting of:
a substrate of cemented carbide, cermet, ceramics, steel or a superhard material; and
a coating with a total thickness of 5 to 40 μm, the coating consisting of one or more refractory layers of which at least one layer is an α-Al2O3 layer having a thickness of 1 to 20 μm,
wherein the length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is more than 80% of the total length of the sum of grain boundaries of Σ3, Σ7, Σ11, Σ17, Σ19, Σ21, Σ23 and Σ29-type grain boundaries (=Σ3-29-type grain boundaries), the grain boundary character distribution being measured by EBSD.

### Claim 2 (depends on 1)

The cutting tool insert of claim 1 wherein the length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is from 82% to 99%, of the total length of the sum of grain boundaries of Σ3-29-type grain boundaries, the grain boundary character distribution being measured by EBSD.

### Claim 3 (depends on 1)

The cutting tool insert of claim 1 wherein the coating comprises a first layer adjacent to the substrate surface, the first layer consisting of carbide, nitride, carbonitride or oxycarbonitride of one or more of Ti, Zr, V and Hf, or combinations thereof deposited using CVD or MT-CVD, having a thickness of from 1 to 20 μm.

### Claim 4 (depends on 3)

The cutting tool insert of claim 3 wherein the coating comprises an intermediate layer between the substrate surface and the first layer, the intermediate layer consisting of titanium nitride, TiN, deposited using CVD or MT-CVD, and having a thickness of less than 5 μm.

### Claim 5 (depends on 3)

The cutting tool insert of claim 3 wherein the α-Al2O3 layer is deposited on top of said first layer.

### Claim 6 (depends on 1)

The cutting tool insert of claim 1 wherein
a) the uppermost layer of the coating is the α-Al2O3 layer or
b) the uppermost layer of the coating is a layer of carbide, nitride, carbonitride or oxycarbnitride of one or more of Ti, Zr, V and Hf, or combinations thereof, having a thickness of from 0.5 to 3 μm, and being deposited atop of the α-Al2O3 layer or
c) surface areas of the cutting tool insert comprise the α-Al2O3 layer as the uppermost layer whereas the remaining surface areas of the cutting tool insert comprise as the uppermost layer a layer of carbide, nitride, carbonitride or oxycarbnitride of one or more of Ti, Zr, V and Hf, or combinations thereof, having a thickness of from 0.5 to 3 μm and being deposited atop of the α-Al2O3 layer.

### Claim 7 (depends on 1)

The cutting tool insert of claim 1 wherein the substrate consists of cemented carbide optionally 0.5-10 wt-% cubic carbides of the metals from groups IVb, Vb and VIb of the periodic table and balance WC.

### Claim 8 (depends on 1)

The cutting tool insert of claim 1 wherein the substrate consists of cemented carbide comprising a binder phase enriched surface zone having a thickness of 5 to 30 μm from the substrate surface, the binder phase enriched surface zone having a Co content that is at least 1.5 times higher than in the core of the substrate and having a content of cubic carbides that is less than 0.5 times the content of cubic carbides in the core of the substrate.

### Claim 9 (depends on 1)

A method of manufacturing a cutting tool insert of any of the claim 1, comprising:
depositing said at least one α-Al2O3 layer is deposited by chemical vapour deposition (CVD),
wherein the reaction gas of the CVD process comprises H2, CO2, AlCl3 and X and optional additions of N2 and Ar, with X being gaseous H2S, SO2, SF6 or combinations thereof, and
wherein the volume ratio of CO2 and X in the CVD reaction chamber lies within the range of 2<CO2/X<10.

### Claim 10 (depends on 9)

The method of claim 9, wherein the volume ratio of CO2 and X in the CVD reaction chamber lies within the range of 3<CO2/X<.

### Claim 11 (depends on 9)

The method of claim 9, wherein the volume proportion of the component X or the combination of components X in the CVD reaction chamber lies within the range of 0.2 vol % to 5.0 vol % of the total volume of gases in the CVD reaction chamber.

### Claim 12 (depends on 9)

The method of claim 9, wherein the volume ratio of CO2/AlCl3 in the CVD reaction chamber is equal or smaller than 1.5 and/or the volume ratio of AlCl3/HCl in the CVD reaction chamber is equal or smaller than 1.

### Claim 13 (depends on 9)

The method of claim 9, wherein the component X in the CVD process is H2S or SO2 or a combination of H2S and SO2, whereby, if the component X in the CVD process is a combination of H2S and SO2, the volume proportion of SO2 does not exceed 20% of the volume amount of H2S.

### Claim 14 (depends on 9)

The method of claim 9, wherein the reaction gas of the CVD process comprises additions of N2 and/or Ar in a volume amount in the range of 4 to 20 vol %, of the total volume of gases in the CVD reaction chamber.

### Claim 15 (depends on 9)

The method of claim 9, wherein the CVD process is conducted at a temperature in the range of 850 to 1050° C. and/or the CVD process is conducted at a reaction gas pressure in the range 50 to 120 mbar.

### Claim 16 (depends on 21)

The cutting tool insert of claim 21 wherein the length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is from 84% to 97% of the total length of the sum of grain boundaries of Σ3-29-type grain boundaries, the grain boundary character distribution being measured by EBSD.

### Claim 17 (depends on 16)

The cutting tool insert of claim 16 wherein the length of Σ3-type grain boundaries in the at least one α-Al2O3 layer is from 86% to 92% of the total length of the sum of grain boundaries of Σ3-29-type grain boundaries, the grain boundary character distribution being measured by EBSD.

### Claim 18 (depends on 3)

The cutting tool insert of claim 3 wherein the thickness of the first layer is from 5 to 10 μm.

### Claim 19 (depends on 3)

The cutting tool insert of claim 3 wherein the the first layer consists of titanium carbonitride, Ti(CN).

### Claim 20 (depends on 4)

The cutting tool insert of claim 4 wherein the thickness of the intermediate layer is from 0.3 to 3 μm.

### Claim 21 (depends on 10)

The method of claim 10, wherein the volume ratio of CO2 and X in the CVD reaction chamber lies within the range of 4<CO2/X<6.

### Claim 22 (depends on 11)

The method of claim 11 wherein the volume proportion of the component X or the combination of components X in the CVD reaction chamber lies within the range of 0.5 vol % to 3.0 vol % of the total volume of gases in the CVD reaction chamber.

### Claim 23 (depends on 22)

The method of claim 22 wherein the volume proportion of the component X or the combination of components X in the CVD reaction chamber lies within the range of 0.6 vol % to 2.0 vol % of the total volume of gases in the CVD reaction chamber.

### Claim 24 (depends on 14)

The method of claim 14, wherein the volume amount of N2 and/or Ar is in the range of 10 to 15 vol % of the total volume of gases in the CVD reaction chamber