Hard coating with thermal stability and high-temperature oxidation resistance as well as preparation method and application of hard coating

Abstract

The invention discloses a hard coating with thermal stability and high-temperature oxidation resistance as well as a preparation method and application of the hard coating, and belongs to the technical field of nitride hard coatings. The hard coating is composed of a bottom columnar crystal TiAlN base coat, a middle columnar crystal AlTiCrN middle layer and an AlCrSiBN surface layer of a surface nanometer composite structure. Low-aluminum TiAl target deposition is adopted for the TiAlN base layer, high-aluminum AlTi target and AlCr target co-deposition is adopted for the middle of the TiAlN base layer, and high-aluminum AlCrSiB target deposition is adopted for the AlCrSiBN surface layer; the thickness of the TiAlN base coat is 0.1 to 0.5 [mu] m; the thickness of the AlTiCrN intermediate layer is 1.0 to 2.0 [mu] m; and the thickness of the AlCrSiBN surface layer is 0.05 to 0.2 [mu] m. The coating has high film-substrate binding force, thermal stability and high-temperature oxidation resistance. The inner layer of the coating has excellent thermal stability, and the outer layer of the coating has excellent high-temperature oxidation resistance, so that the coating has wide application prospects on the surfaces of products such as cutting tools and molds.

Description

Technical Field

[0001] The present invention belongs to the technical field of nitride hard coatings, and more particularly relates to a hard coating having both thermal stability and high-temperature oxidation resistance, and a preparation method and application thereof. Background Art

[0002] With the continuous advancement of high-speed cutting technology, the temperature generated during the cutting process rises rapidly, posing a significant challenge to the thermal stability and high-temperature oxidation resistance of tool coatings. To meet this challenge, a dense oxide film needs to form on the coating surface to prevent further oxygen penetration into the coating. At the same time, the substrate of the coating must possess high hardness and excellent thermal stability. In short, tool coatings must possess excellent thermal stability on the inside and excellent oxidation resistance on the outside. However, the coating technologies currently available on the market struggle to meet both requirements simultaneously. Studies have found that TiAlN coatings, which are widely used commercially, have good thermal stability but poor resistance to high-temperature oxidation; while AlCrN coatings have excellent oxidation resistance, their thermal stability is insufficient. Therefore, it is of great significance to develop a hard coating that combines thermal stability and high-temperature oxidation resistance. Summary of the Invention

[0003] The purpose of the present invention is to provide a hard coating with both thermal stability and high-temperature oxidation resistance, as well as a preparation method and application thereof, so as to overcome the problem in the prior art that tool coatings are difficult to achieve both thermal stability and high-temperature oxidation resistance. A hard coating with both thermal stability and high-temperature oxidation resistance is designed, comprising a TiAlN base layer with high hardness and excellent thermal stability, an AlTiCrN intermediate layer with excellent hardness and thermal stability, and an AlCrSiBN surface layer with excellent high-temperature resistance.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] One of the technical solutions of the present invention is to provide a hard coating with both thermal stability and high-temperature oxidation resistance, comprising a TiAlN base layer, an AlTiCrN middle layer and an AlCrSiBN surface layer arranged in sequence.

[0006] Preferably, the TiAlN base layer and the AlTiCrN middle layer have a columnar crystal structure; and the AlCrSiBN surface layer has a nanocomposite structure.

[0007] The TiAlN coating is deposited using TiAl, which has a high affinity with the substrate and improves coating adhesion. Furthermore, the TiAlN coating exhibits high thermal stability, ensuring the durability of the hard coating under high-temperature service. The AlTiCrN intermediate layer is co-deposited using an AlCr target and TiAl, providing a good match with the TiAlN and AlCrSiBN layers and excellent thermal stability. The AlCrSiBN layer is deposited using AlCrSiB, exhibiting excellent oxidation resistance and thermal stability. This ensures the formation of a dense boron-containing oxide at high temperatures, reducing the coefficient of friction and improving wear resistance.

[0008] Preferably, the thickness of the TiAlN base layer is 0.1-0.5 μm; the thickness of the AlTiCrN intermediate layer is 1.0-2.0 μm; and the thickness of the AlCrSiBN surface layer is 0.05-0.2 μm.

[0009] The present invention utilizes a TiAlN basecoat and an AlCrTiN layer to regulate interfacial stress and hardness distribution, thereby improving the interfacial bonding between the coating and the substrate, as well as between the TiAlN basecoat and the AlCrTiN layer. Furthermore, after numerous studies, the inventors discovered that under high-temperature oxidative service conditions, the (Al, Cr)2O3 composite oxide layer is denser than Al2O3 and Cr2O3 oxides, and Si oxidizes at high temperatures to form an amorphous SiO2 oxide layer at the interface between the coating and the oxide layer. The synergistic effect of the (Al, Cr)2O3 and SiO2 oxide layers can significantly improve the coating's resistance to high-temperature oxidation. Furthermore, B is oxidized to form a B2O3 lubricating layer on the surface of the oxide layer, enhancing the coating's lubricity and ultimately its wear resistance. Based on the aforementioned background, an AlCrSiBN layer is designed as the coating's surface layer.

[0010] The heterogeneous nano-hard coating obtained by combining a TiAlN base layer with high hardness and excellent thermal stability, an AlTiCrN intermediate layer with excellent hardness and thermal stability, and an AlCrSiBN surface layer with excellent high-temperature resistance has high bonding strength, hardness, excellent thermal stability and high-temperature oxidation resistance. The coated tools prepared using this coating have better cutting performance than commercially available AlTiN, AlCrN and other coated tools.

[0011] The second technical solution of the present invention is to provide a method for preparing the hard coating having both thermal stability and high-temperature oxidation resistance, comprising the following steps:

[0012] In nitrogen atmosphere, TiAlN base layer was deposited on the substrate surface using TiAl target;

[0013] In nitrogen atmosphere, AlCr target and TiAl target were used to co-deposit AlTiCrN intermediate layer on the surface of TiAlN base layer.

[0014] In a nitrogen atmosphere, an AlCrSiBN surface layer was deposited on the surface of the AlTiCrN intermediate layer using an AlCrSiB target.

[0015] The present invention utilizes AlCr and TiAl targets instead of AlCrTi targets to deposit AlCrTiN coatings. This is because AlCrTi targets easily form a single-phase solid solution with uniform composition, whereas AlCrTiN coatings deposited using AlCr and TiAl targets exhibit compositional fluctuations, leading to a high density of interfacial dislocations at the interface between the Ti-rich and Cr-rich regions. This results in high dislocation strengthening, resulting in a coating with higher hardness and improved wear resistance. Consequently, AlCrTiN coatings deposited using AlCr and TiAl targets exhibit higher hardness and superior wear resistance.

[0016] Preferably, the substrate comprises cemented carbide or steel (such as mold steel).

[0017] Furthermore, the substrate further includes the steps of sandblasting passivation, cleaning and argon ion etching before use; the purpose of the cleaning is degreasing and deoiling.

[0018] Preferably, when depositing the TiAlN base layer, the atomic percentage of Ti in the TiAl target is 50-67%, and the atomic percentage of Al is 33-50%. The parameters for depositing the TiAlN base layer include: substrate temperature 450-550°C, nitrogen pressure 2.0-5.0 Pa, target current 100-180 A, substrate bias -120--40 V, and deposition time 5-25 min.

[0019] Preferably, when depositing the AlTiCrN intermediate layer, in the AlCr target, the atomic percentage of Al is 50-70%, and the atomic percentage of Cr is 30-50%; in the TiAl target, the atomic percentage of Ti is 50-67%, and the atomic percentage of Al is 33-50%; the parameters for depositing the AlTiCrN intermediate layer include: substrate temperature 450-550°C, nitrogen pressure 2.0-5.0Pa, target current independent of 100-180A, substrate bias -120--40V, and deposition time 30-75min.

[0020] Preferably, when depositing the AlTiCrN intermediate layer, the current of the AlCr target is 100-180A; the current of the TiAl target is 100-180A.

[0021] Preferably, when depositing the AlCrSiBN surface layer, in the AlCrSiB target, the atomic percentage of Al is 42-65%, the atomic percentage of Cr is 20-30%, the atomic percentage of Si is 15-18%, and the remainder is B; the parameters for depositing the AlCrSiBN surface layer include: substrate temperature 450-550°C, nitrogen pressure 2.0-5.0Pa, target current 100-180A, substrate bias -120--40V, and deposition time 40-90min.

[0022] The present invention limits the atomic percentage of target materials for depositing each layer so that the aluminum content of the TiAlN base layer is less than that of the AlTiCrN middle layer. At the same time, the instability of the B-containing solid solution is utilized to decompose during deposition to form a nanocomposite structure consisting of nanocrystals embedded in an amorphous matrix.

[0023] The third technical solution of the present invention is to provide the application of the above-mentioned hard coating having both thermal stability and high-temperature oxidation resistance in the preparation of coating tools.

[0024] Furthermore, the coating tools include but are not limited to cutting tools and molds.

[0025] The present invention discloses the following technical effects:

[0026] The present invention provides a hard coating with both thermal stability and high-temperature oxidation resistance. The hard coating is composed of a bottom columnar TiAlN base layer, a middle columnar AlTiCrN intermediate layer, and a surface AlCrSiBN nanocomposite structure. The TiAlN base layer is deposited using a low-aluminum TiAl target, the middle layer is co-deposited using a high-aluminum AlTi target and AlCr target, and the AlCrSiBN surface layer is deposited using a high-aluminum AlCrSiB target. The TiAlN base layer has a thickness of 0.1 to 0.5 μm; the AlTiCrN intermediate layer has a thickness of 1.0 to 2.5 μm; and the AlCrSiBN surface layer has a thickness of 0.05 to 0.2 μm. The heterogeneous nanocoating of the present invention has high film-substrate bonding and excellent thermal stability and high-temperature oxidation resistance. Coated tools prepared using this coating have excellent cutting performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The bonding strength of the TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoating provided in Example 1;

[0028] Figure 2 This is a cross-sectional TEM micrograph of the TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoating provided in Example 1 after high-temperature annealing at 1000°C for 2h;

[0029] Figure 3This is a cross-sectional SEM image of the TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoating provided in Example 1 after high-temperature oxidation at 1000°C for 2h. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0031] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. The intermediate value within any stated value or stated range, and each smaller range between any other stated value or intermediate value within the stated range, is also encompassed within the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0032] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0033] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be illustrative only.

[0034] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0035] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0036] Unless otherwise specified, the materials used in the following examples and comparative examples of the present invention are all commercially available products, and the sources of the commercially available products do not affect the technical effects of the present invention.

[0037] The target materials used are specifically: Ti67Al33, that is, the atomic percentage of Ti is 67%, and the atomic percentage of Al is 33%; Al70Cr30, that is, the atomic percentage of Al is 70%, and the atomic percentage of Cr is 30%; Al50Cr23Si15B12, that is, the atomic percentage of Al is 50%, the atomic percentage of Cr is 23%, the atomic percentage of Si is 15%, and the atomic percentage of B is 12%.

[0038] The substrate used is cemented carbide.

[0039] Example 1

[0040] This embodiment provides a hard coating with both thermal stability and high-temperature oxidation resistance, which is composed of a TiAlN base layer, an AlTiCrN intermediate layer and an AlCrSiBN surface layer arranged in sequence, wherein the TiAlN base layer is connected to the substrate, and is recorded as a TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoating.

[0041] The specific preparation steps are as follows:

[0042] S1: A carbide cutting tool was passivated by sandblasting, ultrasonically cleaned, and then argon ion etched. The etching voltages were 100 V, -400 V, -800 V, -500 V, and -200 V, and the etching times were 2 min, 5 min, 8 min, 5 min, and 3 min, respectively.

[0043] S2: Using an arc ion plating machine in a nitrogen atmosphere, a Ti67Al33 target was used to deposit a TiAlN base layer on the cutting tool surface. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -50 V, and deposition time 10 minutes. This resulted in a TiAlN base layer with a thickness of 0.2 μm.

[0044] S3: Using an arc ion plating system in a nitrogen atmosphere, an Al70Cr30 target and a Ti67Al33 target were co-deposited onto the TiAlN base layer to form an AlTiCrN intermediate layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A for both targets, substrate bias voltage -60 V, and deposition time 60 min. This resulted in a TiAlN-AlCrTiN layer with a thickness of 2.0 μm.

[0045] S4: Using an arc ion plating system in a nitrogen atmosphere, an Al50Cr23Si15B12 target was used to deposit an AlCrSiBN surface layer on the AlCrTiN layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 15 minutes. This resulted in a TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoating. The AlCrSiBN layer had a thickness of 0.15 μm.

[0046] Examples 2 to 6

[0047] Examples 2 to 6 provide TiAlN-AlCrTiN-AlCrSiBN heterogeneous nanocoatings with different layer thicknesses, which are also composed of a TiAlN base layer, an AlTiCrN intermediate layer and an AlCrSiBN surface layer arranged in sequence, wherein the TiAlN base layer is connected to a substrate. The main difference from Example 1 is that the deposition parameters of each layer are different, thereby resulting in different thicknesses of the formed layers.

[0048] The deposition parameters of each layer are set as shown in Tables 1 to 3 (the parameters not listed in the table are the same as those in Example 1).

[0049] Table 1 Deposition parameters for forming TiAlN bottom layer in Examples 2 to 6

[0050]

[0051] Table 2 Deposition parameters for forming AlTiCrN intermediate layer in Examples 2 to 6

[0052]

[0053]

[0054] During the deposition process of forming the AlCrTiN layer, the substrate temperature and nitrogen pressure in Examples 2 to 6 are the same as those in Example 1.

[0055] Table 3 Deposition parameters of AlCrSiBN surface layer formed in Examples 2 to 6

[0056]

[0057] During the deposition process of forming the AlCrSiBN surface layer, the substrate temperature and nitrogen pressure in Examples 2 to 6 are the same as those in Example 1.

[0058] Comparative Example 1

[0059] The preparation method of commercial AlCrN coating on the market is as follows:

[0060] S1: The cutting tool made of cemented carbide is sandblasted and passivated, then ultrasonically cleaned, and then argon ion etched;

[0061] S2: Using an arc ion plating system, three rows of Al70Cr30 targets were simultaneously deposited on the cutting tool surface in a nitrogen atmosphere to form an AlCrN base layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -50 V, and deposition time 20 minutes. The resulting AlCrN base layer had a thickness of 0.5 μm.

[0062] S3: Using an arc ion plating machine in a nitrogen atmosphere, an Al70Cr30 target was used to deposit an AlCrN surface layer onto the AlCrN base layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 80 min. The resulting AlCrN surface layer had a thickness of 2.0 μm. This resulted in an AlCrN coating with a thickness of 2.5 μm.

[0063] Comparative Example 2

[0064] The preparation method of commercial AlTiN coating on the market is as follows:

[0065] S1: The cutting tool made of cemented carbide is sandblasted and passivated, then ultrasonically cleaned, and then argon ion etched;

[0066] S2: Using an arc ion plating system, three rows of Al67Ti30 targets were simultaneously deposited on the cutting tool surface in a nitrogen atmosphere to form an AlTiN base layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -50 V, and deposition time 20 minutes. The resulting AlTiN base layer had a thickness of 0.5 μm.

[0067] S3: Using an arc ion plating machine in a nitrogen atmosphere, an Al70Cr30 target was used to deposit an AlCrN surface layer onto the AlTiN base layer. Deposition process parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 80 min. The resulting AlTiN surface layer had a thickness of 2.0 μm. This resulted in an AlTiN coating with a thickness of 2.5 μm.

[0068] Comparative Example 3

[0069] Compared with Example 1, step S2 is omitted, and the rest is the same as Example 1.

[0070] Comparative Example 4

[0071] Compared with Example 1, step S3 is omitted, and the rest is the same as Example 1.

[0072] Comparative Example 5

[0073] Compared with Example 1, step S4 is omitted, and the rest is the same as Example 1.

[0074] Comparative Example 6

[0075] Compared with Example 1, S2 and S4 are swapped, and the rest are the same as Example 1.

[0076] Comparative Example 7

[0077] Compared with Example 1, S2 and S3 are swapped, and the rest are the same as Example 1.

[0078] Comparative Example 8

[0079] Compared with Example 1, S3 and S4 are swapped, and the rest are the same as Example 1.

[0080] Comparative Example 9

[0081] Compared with Example 1, the TiAlN base layer in S2 is replaced by an AlCrN base layer, and the rest is the same as Example 1.

[0082] The formation process of AlCrN base layer is as follows:

[0083] Using an arc ion plating machine in a nitrogen atmosphere, an Al70Cr30 target was used to deposit an AlCrN base layer on the cutting tool surface. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -50 V, and deposition time 10 minutes. This resulted in an AlCrN base layer with a thickness of 0.2 μm.

[0084] Comparative Example 10

[0085] Compared with Example 1, the AlCrSiBN surface layer in S4 is replaced by an AlTiSiN surface layer, and the rest is the same as Example 1.

[0086] The formation process of the AlTiSiN surface layer is as follows: an Al50Ti35Si15 target is used and other deposition parameters remain unchanged.

[0087] Using an arc ion plating system in a nitrogen atmosphere, an Al50Ti35Si15 target was used to deposit an AlTiSiN surface layer onto the AlCrTiN layer. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 15 minutes. This resulted in a TiAlN-AlCrTiN-AlTiSiN heterogeneous nanocoating. The AlTiSiN layer had a thickness of 0.15 μm.

[0088] Comparative Example 11

[0089] Compared with Example 1, the AlCrSiBN surface layer in S4 is replaced by an AlCrN surface layer, and the rest is the same as Example 1.

[0090] The formation process of AlCrN surface layer is as follows:

[0091] Using an arc ion plating system in a nitrogen atmosphere, an Al70Cr30 target was used to deposit an AlCrN surface layer onto the AlCrTiN layer. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 15 minutes. This resulted in a TiAlN-AlCrTiN-AlCrN heterogeneous nanocoating. The AlCrN layer had a thickness of 0.15 μm.

[0092] Comparative Example 12

[0093] Compared with Example 1, the sedimentation time in S2 is adjusted to 4 minutes, the sedimentation time in S3 is adjusted to 25 minutes, and the sedimentation time in S4 is adjusted to 4 minutes. Others are the same as in Example 1.

[0094] Comparative Example 13

[0095] Compared with Example 1, the sedimentation time in S2 is adjusted to 30 min, the sedimentation time in S3 is adjusted to 80 min, and the sedimentation time in S4 is adjusted to 30 min. Others are the same as in Example 1.

[0096] Comparative Example 14

[0097] Compared with Example 1, the AlTiCrN intermediate layer in S3 is replaced by an AlTiN intermediate layer, and the rest is the same as Example 1.

[0098] The AlTiN interlayer is formed by co-depositing the AlTiN interlayer onto the TiAlN base layer using an Al67Ti30 target in a nitrogen atmosphere using an arc ion plating machine. Deposition parameters include substrate temperature of 500°C, nitrogen pressure of 3.0 Pa, target current of 160 A, substrate bias of -60 V, and deposition time of 60 minutes. This results in a TiAlN-AlTiN layer with a thickness of 2.0 μm.

[0099] Comparative Example 15

[0100] Compared with Example 1, the AlTiCrN intermediate layer in S3 is replaced by an AlCrN intermediate layer, and the rest is the same as Example 1.

[0101] The AlCrN interlayer is formed by co-depositing the AlCrN interlayer onto the TiAlN base layer using an Al70Cr30 target in a nitrogen atmosphere using an arc ion plating machine. Deposition parameters include substrate temperature of 500°C, nitrogen pressure of 3.0 Pa, target current of 160 A, substrate bias of -60 V, and deposition time of 60 minutes. This results in a TiAlN-AlCrN layer with a thickness of 2.0 μm.

[0102] Comparative Example 16

[0103] Compared with Example 1, steps S2 and S3 are omitted, and the rest are the same as Example 1.

[0104] Comparative Example 17

[0105] Compared with Example 1, steps S2 and S4 are omitted, and the rest are the same as Example 1.

[0106] Comparative Example 18

[0107] Compared with Example 1, steps S3 and S4 are omitted, and the rest are the same as Example 1.

[0108] Comparative Example 19

[0109] Compared with Example 1, the AlCrSiBN surface layer in S4 is replaced by an AlTiSiBN surface layer, and the rest is the same as Example 1.

[0110] The formation process of the AlTiSiBN surface layer is as follows:

[0111] Using an arc ion plating system in a nitrogen atmosphere, an Al50Ti38B12 target and a Ti85Si15 target were used to co-deposit an AlTiSiBN surface layer onto the AlCrTiN layer. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 15 minutes. This resulted in a TiAlN-AlCrTiN-AlTiSiBN heterogeneous nanocoating. The AlTiSiBN layer had a thickness of 0.15 μm.

[0112] Comparative Example 20

[0113] Compared with Example 1, the AlCrSiBN surface layer in S4 is replaced by an AlTiN surface layer, and the rest is the same as Example 1.

[0114] The formation process of AlTiN surface layer is as follows:

[0115] Using an arc ion plating system in a nitrogen atmosphere, an Al67Ti30 target was used to deposit an AlTiN surface layer onto the AlCrTiN layer. Deposition parameters were: substrate temperature 500°C, nitrogen pressure 3.0 Pa, target current 160 A, substrate bias voltage -60 V, and deposition time 15 minutes. This resulted in a TiAlN-AlCrTiN-AlTiN heterogeneous nanocoating. The AlTiN layer had a thickness of 0.15 μm.

[0116] Performance testing:

[0117] The coating hardness, adhesion, thermal stability, and high-temperature oxidation resistance of Examples 1-6 and Comparative Examples 1-20 were tested using a scratch test, as well as the cutting length of the coated tool when machining 304 stainless steel. Cutting parameters were: 180 m / min, 2.0 mm depth of cut, 0.15 mm / r feed, machining 304 stainless steel.

[0118] The test results are shown in Tables 4 and 5.

[0119] Table 4 Performance test results of the coatings obtained in Examples 1 to 6

[0120]

[0121] Table 5 Performance test results of the coatings obtained in Example 1 and Comparative Examples 1 to 20

[0122]

[0123] The thermal stability in Tables 4 and 5 refers to the highest temperature at which the coating structure does not decompose after high-temperature annealing; the oxide layer thickness refers to the thickness of the oxide layer formed by oxidation at 1000°C for 2 hours in an atmospheric environment, which is used to judge the material's antioxidant properties.

[0124] As can be seen from Tables 4 and 5, the coatings obtained in Examples 1 to 6 of the present invention have high hardness and bonding strength, as well as excellent thermal stability, and thus the coated tools thereof have better cutting performance. When the thickness of the heterogeneous nano-coating is less than 2.0 μm and the thickness exceeds 3.0 μm, the cutting performance of the coated tools is reduced. In comparison, under the same cutting conditions, the coated tools developed in Examples 1 to 6 of the present invention have better cutting performance than the main AlCrN and AlTiN coated tools on the market. In addition, tool coatings with excellent cutting performance must have high hardness, high bonding strength, and excellent thermal stability and high-temperature oxidation resistance. When the sequence of the bottom layer, middle layer, and surface layer in the heterogeneous nano-coating is swapped, the thermal stability and high-temperature oxidation resistance of the coating will be significantly degraded, and thus the coated tools thereof have poor cutting performance; when the AlTiCrN middle layer is replaced with a layer of AlTiN, AlCrN, or other coating, the bonding strength is reduced and the cutting life of the tool is also reduced.

[0125] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0126] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A hard coating having both thermal stability and high temperature oxidation resistance, characterized in that: The invention comprises a TiAlN bottom layer, an AlTiCrN middle layer and an AlCrSiBN surface layer which are arranged in sequence.

2. The hard coating having both thermal stability and high temperature oxidation resistance according to claim 1, characterized in that: The TiAlN bottom layer and the AlTiCrN middle layer are columnar crystal structures; the AlCrSiBN surface layer is a nano-composite structure.

3. The hard coating with both thermal stability and high temperature oxidation resistance according to claim 1, characterized in that: The thickness of the TiAlN base layer is 0.1-0.5 μm; the thickness of the AlTiCrN intermediate layer is 1.0-2.0 μm; and the thickness of the AlCrSiBN surface layer is 0.05-0.2 μm.

4. The method for preparing a hard coating having both thermal stability and high temperature oxidation resistance according to any one of claims 1 to 3, characterized in that: The steps include: In nitrogen atmosphere, TiAlN base layer was deposited on the substrate surface using TiAl target; In nitrogen atmosphere, AlCr target and TiAl target were used to co-deposit AlTiCrN intermediate layer on the surface of TiAlN base layer; In a nitrogen atmosphere, an AlCrSiBN surface layer was deposited on the surface of the AlTiCrN intermediate layer using an AlCrSiB target.

5. The preparation method according to claim 4, characterized in that The substrate comprises cemented carbide or steel.

6. The preparation method according to claim 4, characterized in that When depositing the TiAlN base layer, the atomic percentage of Ti in the TiAl target is 50-67%, and the atomic percentage of Al is 33-50%; and / or, the parameters for depositing the TiAlN base layer include: substrate temperature 450-550° C., nitrogen pressure 2.0-5.0 Pa, target current 100-180 A, substrate bias voltage -120--40 V, and deposition time 5-25 min.

7. The preparation method according to claim 4, characterized in that When depositing the AlTiCrN intermediate layer, in the AlCr target, the atomic percentage of Al is 50-70%, and the atomic percentage of Cr is 30-50%; in the TiAl target, the atomic percentage of Ti is 50-67%, and the atomic percentage of Al is 33-50%; and / or, parameters for depositing the AlTiCrN intermediate layer include: substrate temperature of 450-550° C., nitrogen pressure of 2.0-5.0 Pa, target current of 100-180 A independently, substrate bias of -120--40 V, and deposition time of 30-75 min.

8. The preparation method according to claim 7, characterized in that When depositing the AlTiCrN intermediate layer, the current of the AlCr target is 100-180A; the current of the TiAl target is 100-180A.

9. The preparation method according to claim 4, characterized in that When depositing the AlCrSiBN surface layer, the AlCrSiB target contains: 42-65% Al atomic percentage, 20-30% Cr atomic percentage, 15-18% Si atomic percentage, and the remainder B; And / or, the parameters for depositing the AlCrSiBN surface layer include: substrate temperature 450-550° C., nitrogen pressure 2.0-5.0 Pa, target current 100-180 A, substrate bias -120--40 V, and deposition time 40-90 min.

10. Use of the hard coating having both thermal stability and high-temperature oxidation resistance according to any one of claims 1 to 3 in the preparation of coated tools.

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