Molding tool coated with kappa alumina

Abstract

The invention relates to a forming tool and to a method for producing said forming tool, said forming tool comprising a substrate surface to be used as a functional surface, said functional surface being coated with a coating, said coating comprising a layer of kappa alumina as a functional layer.

Description

[0001] The present invention relates to a forming die and a method for producing the forming die of the present invention, wherein the forming die of the present invention comprises a substrate surface to be used as a functional surface, the functional surface being coated with a coating, wherein the coating comprises a kappa aluminum oxide layer as a functional layer. The kappa aluminum oxide layer is deposited by using a low pressure chemical vapor deposition (LPCVD) process, and the forming die is particularly preferably used for aluminum forming processes and aluminum forming processes, such as, in particular (but not limited to), applications in cold forming and cold forming processes, i.e., in particular (but not limited to), aluminum cold forming and aluminum forming processes, wherein, in the context of the present invention, aluminum forming processes and aluminum forming processes also include aluminum alloy forming processes and aluminum alloy forming processes. Background Art

[0002] Titanium carbide (TiC) and titanium nitride (TiN) are known materials deposited using chemical vapor deposition (CVD) technology (hereinafter also referred to as CVD-TiC and CVD-TiN) and are often used as coatings to enhance the performance of forming dies for cold forming of aluminum. Nevertheless, the adhesion of aluminum to the surface of the forming die is always a disadvantage and shortens the service life of the forming die, so the die must be cleaned frequently.

[0003] The use of doped kappa alumina layers is known, for example, from patent application DE 2825009 A1 and patent specification DE 2825009 C2. In these documents it is described that in order to produce a single-phase or nearly single-phase kappa alumina layer having better chip formation processing properties than other types of alumina-containing layers, titanium, zirconium or hafnium is used as a doping element and that the doped kappa alumina layer is formed by using titanium tetrachloride, zirconium tetrachloride or hafnium tetrachloride, respectively.

[0004] Purpose of the Invention

[0005] The main object of the present invention is to provide a new coating solution which overcomes the disadvantages of current coating solutions for forming dies for aluminium cold forming. Summary of the invention

[0006] The object of the present invention is achieved by providing a coating molding die, which includes a substrate 1, wherein the substrate has a substrate surface to be used as a functional surface, the functional surface is coated with a coating (thereby forming a coated functional surface), wherein the coating includes a kappa aluminum oxide layer 20 as a functional layer.

[0007] Preferably, the coating is applied on a forming mold and further comprises one or more additional layers between the surface of the substrate 1 and the kappa alumina layer 20, for providing:

[0008] Enhanced adhesion between the coating and the substrate, in particular to enhance the adhesion of the kappa alumina layer 20 to the substrate surface, and / or

[0009] Diffusion barrier effect, used to avoid or reduce the diffusion of chemical elements from the substrate 1 (especially the substrate surface) to the coating, thereby avoiding diffusion from the substrate surface to the kappa alumina layer 20, and / or

[0010] Stress compensation between the substrate 1 and the kappa alumina layer 20 is used to enhance the toughness of the coated functional surface, especially to improve the load-bearing capacity of the coating molding die during application.

[0011] According to a preferred embodiment of the present invention, the coating of the molding die of the present invention is manufactured in the following manner, that is, it includes a multilayer film 30, which provides a diffusion barrier effect, can avoid or at least reduce the diffusion of chemical elements from the substrate surface to the coating, and also provides stress compensation between the substrate 1 surface and the κ alumina layer 20, so as to enhance the toughness of the coating functional surface. The multilayer film 30 is preferably deposited in the following manner, that is, TiN layers 32 and TiCN layers 31 are alternately deposited to form a TiN / TiCN / TiN / TiCN... structure.

[0012] According to another preferred embodiment of the present invention, the coating comprises an additional TiN layer, which is deposited as an adhesion layer 10 to enhance the adhesion of the coating to the substrate surface (on which the coating is deposited) and to provide a diffusion barrier effect. The adhesion layer is preferably deposited directly on the substrate surface and its layer thickness is preferably in the range of 0.3 μm to 1 μm.

[0013] According to a further preferred embodiment of the invention, a further intermediate layer, preferably a TiCN layer, is deposited between the multilayer film 30 and the functional layer 20 (ie the κ alumina layer) to obtain a clamping effect between the κ alumina layer 20 and the multilayer film 30 .

[0014] In the context of the present invention, some preferred types of forming dies include:

[0015] Cold forming inserts,

[0016] Forming punch,

[0017] Roll forming dies,

[0018] ·Drawing forming inserts,

[0019] Powder compaction mold,

[0020] Pull ring,

[0021] Cold forging die,

[0022] Perforating punch,

[0023] Cooling core,

[0024] Die casting dies and core pins,

[0025] Metal profiling extrusion die,

[0026] Metal profiling extrusion dies.

[0027] The above-listed preferred forming dies should only be taken as an exemplary list of forming dies in the present invention, and should not be considered as a limitation on the forming dies that can be considered within the scope of the present invention.

[0028] Preferably, the kappa alumina layer is deposited as the outermost layer of the coating.

[0029] Preferably, the kappa alumina layer is post-treated until a surface quality is achieved characterized by an average roughness of Ra=0.02 μm, more preferably Ra≤0.02 μm, or even Ra<0.02 μm.

[0030] The layer thickness of the kappa aluminum oxide layer is preferably in the range of 2 μm to 8 μm, more preferably in the range of 3 μm to 5 μm.

[0031] The total coating thickness is preferably in the range of 5 μm to 20 μm, more preferably 6 μm to 15 μm.

[0032] According to the present invention, the molding die of the present invention is manufactured by using a method comprising at least the following steps:

[0033] providing a forming mold including a substrate surface to be used as a functional surface,

[0034] • Depositing a coating on the functional surface, wherein during the deposition of the coating at least one kappa alumina layer is deposited by using a low pressure chemical vapor deposition (LPCVD) technique.

[0035] Kappa alumina produced using LPCVD has been shown to enable better wettability of aluminum relative to the coated surface of the forming die during the forming process compared to TiN coatings or TiC coatings because, unlike TiC or TiN, aluminum does not readily adhere to kappa alumina.

[0036] Thus, the present invention improves die performance and service life of forming dies used in aluminum processing operations compared to the prior art because the dies do not require frequent cleaning and the kappa alumina coating is less susceptible to damage.

[0037] Kappa alumina is used as a coating material instead of TiC, which significantly extends the service life by about 800%.

[0038] The coating comprising kappa alumina in the present invention exhibits better wettability when interacting with aluminum. The layer has a low Young's contact angle (approximately θ<90°) when interacting with molten aluminum or aluminum alloys compared to TiN and TiC layers.

[0039] When comparing TiC as a functional coating (according to the prior art) with kappa alumina as a functional coating (according to the invention), it was observed that the tendency of aluminum to adhere to the die surface was significantly reduced, so that the die service life before the die had to be replaced was increased by about 800%. This is a significant breakthrough / advancement in aluminum cold forming (e.g. aluminum forging applications).

[0040] According to the invention, the forming die of the invention is particularly suitable for forming and shaping applications.

[0041] According to a preferred embodiment of the present invention, the coating layer provided on the molding die is formed in the following manner, that is, comprising the following layers:

[0042] - TiN layer as adhesion layer and diffusion barrier,

[0043] - a multilayer film as a stress compensation layer and a diffusion barrier layer, the multilayer film comprising TiN layers and TiCN layers deposited alternately with each other, and

[0044] - A kappa aluminum oxide layer (hereinafter also referred to as kappa-Al2O3 layer) as a functional layer, or even as a main functional layer.

[0045] Embodiment of manufacturing a molding die according to the present invention:

[0046] Cold forming dies made of WC-Co with a cobalt content in the range of 10 wt. % to 27 wt. %, and cold forming dies made of steels of types 1.2343 and 1.279, are coated in accordance with a preferred embodiment of the present invention in the following manner, i.e., a coating is deposited which is formed by a first TiN coating layer, a multilayer film consisting of TiN and TiCN coating layers, and a κ-Al2O3 coating layer as the outermost layer. The coating deposition is carried out in the following manner:

[0047] 1.Deposition of TiN layer:

[0048] The TiN layer is deposited as an adhesion layer 10 and at the same time acts as a diffusion barrier, preventing possible diffusion of elements from the substrate into the coating, which could lead to deterioration of the coating properties.

[0049] The use of the above-mentioned TiN layer is advisable in particular when the substrate is a cemented carbide material, for example a WC—Co substrate, whose cobalt content is greater than 8 wt. % (Co>8 wt. %).

[0050] This prevents cobalt from diffusing under high temperature and low pressure conditions and forming an η phase at the interface between the substrate surface and the coating. In addition to acting as a diffusion barrier, the TiN layer also acts as an adhesion promoter, thereby enabling good adhesion between the substrate and the additional coating layer deposited on the TiN layer.

[0051] The TiN layer is deposited according to the following reaction:

[0052] TiCl4(g)+0.5N2(g)+3H2(g)→TiN(s)+4HCl(g)+H2(g)

[0053] 2. Deposition of a multilayer film, the multilayer film being formed by a TiN / TiCN bilayer repeated x times, wherein x is preferably in the range of 10 to 20, ie the bilayer is preferably repeated 10 to 20 times.

[0054] The TiN / TiCN multilayer film is disposed as an intermediate layer between the first TiN layer deposited as an adhesion layer and a diffusion barrier layer and the κ-Al2O3 functional layer. The TiN / TiCN multilayer film is preferably deposited in such a way that it consists of repeated TiN layers and TiCN layers, which are deposited alternately with each other to form a TiN / TiCN / TiN / TiCN ... structure, and serves as a stress compensation intermediate layer between the first TiN layer and the κ-Al2O3 layer. With the multilayer film, stress accumulation can be reduced or stopped. In addition, the multilayer film 30 also acts as a diffusion barrier.

[0055] The TiN and TiCN independent layers forming the multilayer film 30 are deposited according to the following reactions:

[0056] TiCl4(g)+0.5N2(g)+3H2(g)→TiN(s)+4HCl(g)+H2(g)

[0057] 3TiCl4(g)+CH4(g)+(1-x) / 2N2(g)+2(1-x)H2(g)→Ti x CN 1-x (s)+4HCl(g)

[0058] 3. Deposition of κ-Al2O3 layer

[0059] κ-Al2O3 is the main functional layer 20. The layer is a hard layer (its hardness is preferably between 30 GPa and 35 GPa, more preferably between 33 GPa and 35 GPa), and is chemically and thermally stable at least up to 1000° C. Therefore, it provides excellent wear resistance at least up to 1000° C.

[0060] The κ-Al2O3 layer is formed according to the following reaction:

[0061] 2Al(s)+6HCl(g)+H2(g)→2AlCl3(g)+4H2(g)——Carried out in an external aluminum generator at 220-335°C and 60-100 mbar.

[0062] H2(g)+CO2(g)→H2O(g)+CO(g)—carried out in situ in the coating reactor at a temperature of about 1000°C, preferably at a temperature in the range of 1000°C to 1050°C, and preferably at a pressure in the range of 65mbar to 80mbar.

[0063] 2AlCl3(g)+3H2O(g)+H2(g)→Al2O3(s)+6HCl(g)+H2(g)——carried out in a coating reactor at a temperature of about 1000°C, preferably at a temperature in the range of 1000°C to 1050°C, and preferably at a pressure in the range of 65mbar to 80mbar.

[0064] The above temperature and pressure ranges may vary depending on the design of the reactor used to perform the LPCVD process.

[0065] The above-mentioned LPCVD process, by including the reactions required to form each of the above-mentioned layers, allows the manufacture of coated forming dies or coated forming dies, which respectively exhibit excellent performance in applications, including aluminum (including aluminum alloy) forming processes (exhibiting excellent cold forming process performance) and forming processes (exhibiting excellent high-pressure die casting performance).

[0066] The inventors have observed that the use of the described reaction and the above-described coating parameters brings the following additional benefits:

[0067] The kappa alumina layer (kappa-Al2O3 layer) obtained in this way is produced without any dopants and shows an optimal combination of properties, resulting in excellent performance when interacting with aluminum and aluminum alloys during forming and shaping processes.

[0068] The coated cold forming dies were used in aluminum cold forming and significant service life extension as well as better oxidation and wear resistance were observed.

[0069] In particular, during the cold forging of aluminum, forming dies coated with a CVD-deposited TiC layer as the main functional layer (according to the prior art) and forming dies coated with the above-described coating according to the invention (as described in the examples of the invention) were tested. The CVD-TiC-coated forming dies required cleaning of the aluminum adhering to the die surface after forming 10 to 50 pieces, while the forming dies according to the current examples of the invention required cleaning of the aluminum adhering to the die surface only after forming 400 pieces. This means that the service life before cleaning is extended by about 800%.

[0070] Figure 1 A schematic diagram showing a preferred embodiment of a coating forming die or a coating portion of a coating forming die according to the present invention.

[0071] Figure 2 A schematic diagram of another preferred embodiment of a coating forming mold or a coating part of a coating forming mold according to the present invention is shown, wherein an additional TiCN layer is deposited between the multilayer coating 30 and the main functional layer 20 to achieve a clamping effect, thereby improving the bonding strength (or cohesive strength) between the κ alumina functional layer 20 and the multilayer coating 30.

[0072] Specifically, the present invention relates to:

[0073] A forming die (i.e. a forming die or a shaping die in the context of the present invention) comprises a substrate surface serving as a functional surface, the functional surface being coated with a coating, wherein the coating comprises a kappa aluminum oxide layer as a functional layer which does not contain doping elements.

[0074] In the forming mould, the coating preferably comprises one or more further layers between the substrate surface and the kappa alumina layer, said layers providing:

[0075] · enhanced adhesion between the coating and the substrate surface, and / or

[0076] Diffusion barrier effect, used to prevent or reduce the diffusion of chemical elements from the substrate surface to the coating, and / or

[0077] Stress compensation between the substrate surface and the kappa alumina layer to enhance the toughness of the coated functional surface, in particular to improve the load-bearing capacity.

[0078] In the molding mold, its coating preferably comprises a multilayer film, which includes TiN layers 32 and TiCN layers 31 deposited alternately with each other to form a TiN / TiCN / TiN / TiCN... structure, which provides a diffusion barrier to avoid or reduce the diffusion of chemical elements from the surface of the substrate to the coating, and also provides stress compensation between the surface of the substrate and the κ alumina layer to enhance the toughness of the coated functional surface.

[0079] In the case of a forming mold, its coating preferably comprises a TiN layer, which provides enhanced adhesion and a diffusion barrier effect between the coating and the substrate surface.

[0080] The forming mold is preferably a forming mold or a shaping mold, which is at least one of the following mold types:

[0081] Cold forming inserts,

[0082] Forming punch,

[0083] Roll forming dies,

[0084] ·Drawing forming inserts,

[0085] Powder compaction mold,

[0086] Pull ring,

[0087] Cold forging die,

[0088] Perforating punch,

[0089] Cooling core,

[0090] Die casting dies and core pins,

[0091] Metal profiling extrusion die,

[0092] Metal profiling extrusion dies.

[0093] In the forming mold, its kappa alumina layer is preferably deposited as the outermost layer of the coating.

[0094] In the forming mold, the κ aluminum oxide layer thereof preferably has a surface quality characterized by an average roughness of Ra=0.02 μm, more preferably Ra≤0.02 μm, or even Ra<0.02 μm.

[0095] In the forming tool, its kappa aluminum oxide layer preferably has a layer thickness in the range from 2 μm to 8 μm, preferably in the range from 3 μm to 5 μm.

[0096] The forming tool preferably has a total coating thickness in the range from 5 μm to 20 μm, preferably from 6 μm to 15 μm.

[0097] In the molding die, an additional layer 40 having a clamping function is preferably deposited between the multilayer film 30 and the κ alumina layer 20 to improve the bonding strength between the multilayer film 30 and the κ alumina layer 20. The layer 40 is preferably a TiCN layer deposited by using the same reaction as described above for depositing the TiCN layer 31, but with a greater thickness and selected to achieve the clamping function.

[0098] A method for manufacturing a molding die according to any one of the above embodiments or a combination thereof, the method comprising the following steps:

[0099] providing a forming mold including a substrate surface to be used as a functional surface,

[0100] Depositing a coating on the functional surface, wherein during the coating deposition at least one kappa aluminum oxide layer without any doping elements is deposited by using a low pressure chemical vapor deposition technique.

[0101] In the method, the kappa alumina layer is preferably formed by using the following reaction, the temperature and pressure being selected depending on the reactor used for deposition:

[0102] ·2Al(s)+6HCl(g)+H2(g)→2AlCl3(g)+4H2(g)

[0103] ·H2(g)+CO2(g)→H2O(g)+CO(g)

[0104] ·2AlCl3(g)+3H2O(g)+H2(g)→Al2O3(s)+6HCl(g)+H2(g).

Claims

1. A molding die, comprising a substrate (1), wherein the substrate (1) has a substrate surface (11) to be used as a functional surface, wherein the functional surface is coated with a coating, wherein: The coating comprises a kappa aluminum oxide layer (20) as a functional layer, wherein the kappa aluminum oxide layer does not contain any doping elements.

2. The molding die according to claim 1, characterized in that: The coating comprises one or more further layers containing TiN and / or TiCN between the substrate surface and the kappa alumina layer, said layers providing: Enhanced adhesion between the coating and the substrate surface, and / or Diffusion barrier effect, used to prevent or reduce the diffusion of chemical elements from the substrate surface to the coating, and / or Stress compensation between the substrate surface and the kappa alumina layer to increase the toughness of the coated functional surface, in particular to improve the load-bearing capacity.

3. The molding die according to claim 2, characterized in that: The coating comprises a multilayer film (30), wherein the multilayer film (30) includes TiN layers (32) and TiCN layers (31) deposited alternately with each other to form a TiN / TiCN / TiN / TiCN...structure, which provides a diffusion barrier effect to avoid or reduce the diffusion of chemical elements from the substrate surface to the coating, and also provides stress compensation between the substrate surface and the kappa alumina layer to enhance the toughness of the coated functional surface.

4. The forming mold according to claim 2 or 3, characterized in that: The coating comprises an adhesion layer (10), which is a TiN layer that provides enhanced adhesion between the coating and the substrate surface and provides a diffusion barrier effect.

5. The molding die according to any one of claims 1 to 4, characterized in that: The molding die is at least one of the following die types: Cold forming inserts, Forming punch, Roll forming dies, ·Drawing forming inserts, Powder compaction mold, Pull ring, Cold forging die, Perforating punch, Cooling core, Die casting dies and core pins, Metal profiling extrusion die, Metal profiling extrusion dies.

6. The molding die according to any one of claims 1 to 5, characterized in that: The kappa alumina layer is deposited as the outermost layer of the coating.

7. The molding die according to claim 6, characterized in that: The kappa alumina layer has a surface quality characterized by an average roughness Ra ≤ 0.02 μm.

8. The molding die according to any one of claims 1 to 7, characterized in that: The layer thickness of the kappa aluminum oxide layer is in the range from 2 μm to 8 μm, preferably from 3 μm to 5 μm.

9. The molding die according to any one of claims 1 to 7, characterized in that: The total thickness of the coating is in the range of 5 μm to 20 μm, preferably 6 μm to 15 μm.

10. The molding die according to any one of claims 1 to 9, characterized in that: An additional layer (40) having a clamping function, preferably a TiCN layer, is deposited between the multilayer film (30) and the kappa alumina layer (20) to improve the bonding strength between the multilayer film (30) and the kappa alumina layer (20).

11. A method for manufacturing a forming mold according to any one of the preceding claims 1 to 10, characterized in that: The method comprises the following steps: providing a forming mold, the forming mold comprising a substrate surface to be used as a functional surface, Depositing a coating on the functional surface, wherein during the coating deposition at least one kappa aluminum oxide layer without any doping elements is deposited by using a low pressure chemical vapor deposition technique.

12. The method according to claim 11, characterized in that: The kappa alumina layer is formed using the following reaction, with the choice of temperature and pressure depending on the reactor used for deposition: ·2Al(s)+6HCl(g)+H2(g)→2AlCl3(g)+4H2(g) ·H2(g)+CO2(g)→H2O(g)+CO(g) ·2AlCl3(g)+3H2O(g)+H2(g)→Al2O3(s)+6HCl(g)+H2(g).

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