Compact oxide coating as well as physical vapor deposition method and application thereof

Abstract

The invention discloses a compact oxide coating and a physical vapor deposition method and application thereof, the compact oxide coating comprises a metal layer and an oxide layer, and the oxide layer is deposited on the surface of the metal layer. The physical vapor phase method comprises the following technological processes: loading a substrate; carrying out ion cleaning on the matrix; inert gas is introduced, the Cr target is started, and a metal layer is deposited on the surface of the base body; mixed gas of oxygen and inert gas is introduced, the flow velocity ratio of the oxygen to the inert gas is 3: 1-2: 1, a Cr target is started, an oxide layer is deposited on the surface of the metal layer, and deposition is conducted for 1-5 min; the flow rate ratio of the oxygen to the inert gas is changed to be 1.5: 1-1: 1, and the deposition time is 60-180 minutes. The oxygen partial pressure is reduced after the target material is poisoned by regulating and controlling the flow velocity ratio of oxygen to argon in stages, so that the stoichiometry and the compactness and mechanical property of the coating are balanced, the performance of the coating is improved and optimized, and the process window for preparing the coating is expanded. The method can be widely applied to the technical field of coating preparation.

Description

Technical Field

[0001] The present application relates to the technical field of coating preparation, and particularly relates to a dense oxide coating, a physical vapor deposition method thereof, and an application thereof. Background Art

[0002] As a common dense oxide coating, the Cr2O3 coating has high hardness, good wear resistance, good thermal stability, and chemical stability. Various techniques such as magnetron sputtering, thermal spraying, chemical vapor deposition, and cathodic arc evaporation have been used to prepare the Cr2O3 coating. In particular, the Cr2O3 coating prepared by magnetron sputtering has good adhesion, uniformity, and a dense structure. However, the process parameters in the physical vapor deposition process have a significant impact on the performance of the Cr2O3 coating.

[0003] Among them, the oxygen flow rate is one of the key process parameters in the Cr2O3 coating preparation process. If the oxygen flow rate is too low, a near-stoichiometric Cr2O3 coating cannot be obtained, resulting in a significant reduction in its mechanical properties; if the oxygen flow rate is too high, serious target poisoning will occur, resulting in a significant reduction in the number of sputtered Cr atoms. At this time, oxygen cannot be completely consumed, resulting in an excess of oxygen in the reaction chamber, and the incorporation of too much oxygen will reduce the crystallinity and density of the Cr2O3 coating.

[0004] It can be seen that the process window for preparing a Cr2O3 coating with excellent performance is narrow, which severely limits its large-scale production and application. There is an urgent need for a simple and easy process parameter setting method to expand the process window for preparing a dense and mechanically excellent Cr2O3 coating. Summary of the Invention

[0005] To solve at least one of the above technical problems, the present application provides a dense oxide coating, a physical vapor deposition method thereof, and an application thereof, and the technical solutions adopted are as follows.

[0006] The dense oxide coating provided by the present application includes a metal layer and an oxide layer. The metal layer contains Cr element, and the oxide layer is deposited on the surface of the metal layer. The oxide layer contains Cr element and oxygen element.

[0007] In certain embodiments of the present application, the chemical formula of the oxide layer is Cr x O y , where x is 35 to 45 at.%, and y is 55 to 65 at.%.

[0008] In certain embodiments of the present application, the thickness of the metal layer is 0.2 to 0.5 μm.

[0009] In certain embodiments of the present application, the thickness of the oxide layer is 1 to 3 μm.

[0010] In some embodiments of the present application, the hardness of the dense oxide coating is at least 30 GPa.

[0011] The dense oxide coating provided by the present application is applied to the surface strengthening of tools, ceramics or mechanical parts.

[0012] The physical vapor deposition method of the dense oxide coating provided by the present application includes the following technological processes:

[0013] Load the substrate into the deposition chamber;

[0014] Vacuumize and heat the deposition chamber, and perform ion cleaning on the substrate;

[0015] Introduce an inert gas, turn on the Cr target, and deposit a metal layer on the surface of the substrate by bipolar pulsed magnetron sputtering;

[0016] Vacuumize the deposition chamber, introduce a mixed gas of oxygen and an inert gas, the flow rate ratio of oxygen to the inert gas is 3:1 to 2:1, turn on the Cr target, and deposit an oxide layer on the surface of the metal layer by bipolar pulsed magnetron sputtering, and the deposition time is 1 to 5 min;

[0017] Change the flow rate ratio of oxygen to the inert gas to 1.5:1 to 1:1, and continue to deposit the oxide layer by bipolar pulsed magnetron sputtering, and the deposition time is 60 to 180 min.

[0018] In some embodiments of the present application, during the process of depositing the metal layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.3 to 0.5 Pa, and the frequency is 50 to 100 kHz.

[0019] In some embodiments of the present application, during the process of depositing the oxide layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.4 to 0.5 Pa, and the frequency is 50 to 100 kHz.

[0020] In some embodiments of the present application, the substrate is made of metal, ceramic or cemented carbide.

[0021] The present application has at least the following beneficial effects: During the process of preparing a dense oxide coating by bipolar pulse magnetron sputtering in the present application, the flow rate ratio of oxygen to inert gas is reduced from 3:1 to 2:1 to 1.5:1 to 1:1. By regulating the flow rate ratio of oxygen to argon in stages, the oxygen partial pressure is reduced after target poisoning to balance the stoichiometry with the coating density and mechanical properties, thereby maximizing the improvement and optimization of the coating performance and expanding the process window for preparing a dense and excellent mechanical property coating. The present application can be widely applied to the technical field of coating preparation.

[0022] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present application will be further illustrated below in conjunction with the drawings and embodiments. It should be noted that the embodiments shown in the following drawings are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application.

[0024] Figure 1 It is the X-ray diffraction pattern of the dense oxide coating in Example 2.

[0025] Figure 2 It is the surface optical morphology diagrams of the dense oxide coatings of Example 1(a) and Example 2(b).

[0026] Figure 3 It is the scanning electron microscope micrographs of the surface and fracture cross-sections of the dense oxide coatings of Example 1(a and c) and Example 2(b and d).

[0027] Figure 4 It is the hardness and elastic modulus of the dense oxide coatings of the comparative example, Example 1 and Example 2 measured by nanoindentation. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will be combined with Figures 1 to 4 The embodiments of the present application will be described in detail, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present application, and should not be construed as a limitation to the present application.

[0029] In the description of the present application, it should be understood that if terms such as "center", "middle part", "longitudinal direction", "transverse direction", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial direction", "radial direction", "circumferential direction", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present application.

[0030] In the description of the present application, the meaning of "several" is more than one, the meaning of "multiple" is more than two. Understandings such as "greater than", "less than", "exceeding", etc. do not include the corresponding number, and understandings such as "above", "below", "within", etc. include the corresponding number. If there is a description of "first", "second", etc., it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0031] In the description of the present application, unless otherwise clearly specified and limited, the terms "set", "install", "connect", "couple" should be understood in a broad sense. For example: it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0032] In the description of the present application, if there are descriptions of reference terms such as "an embodiment", "some embodiments", "an example", "some examples", "some embodiments", "illustrative embodiments", "examples", "specific examples", "some examples", etc., it means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0033] The present application relates to a dense oxide coating, and the dense oxide coating is applied to the surface strengthening of cutting tools, ceramics or mechanical parts.

[0034] Specifically, the dense oxide coating includes a metal layer and an oxide layer. The metal layer contains Cr element, and the oxide layer contains Cr element and oxygen element. The metal layer is deposited on the surface of the substrate, and the oxide layer is deposited on the surface of the metal layer.

[0035] A metal layer and an oxide layer form a composite coating. The metal layer enhances the bonding force with the substrate, and the oxide layer provides excellent mechanical properties, taking into account both the bonding strength and the surface properties, giving full play to the characteristics of the dense oxide coating, and is suitable for surface strengthening of cutting tools and mechanical components to extend the service life.

[0036] The thickness of the metal layer is 0.2 to 0.5 μm. The metal layer, as a transition layer, can improve the bonding force of the coating on the substrate surface. If the thickness of the metal layer is too small, it is not sufficient to improve the bonding force of the coating. If the thickness of the metal layer is too large, it will affect the mechanical properties of the coating.

[0037] The chemical formula of the oxide layer is Cr x O y , where x is 35 to 45 at.%, and y is 55 to 65 at.%. It can be found from Table 1 in the following text that if the stoichiometric ratio of the chromium oxide coating, that is, the ratio of O to Cr, is significantly lower than 1.5, the coating exhibits metallic characteristics (that is, no corundum-type crystal structure is formed) and has poor mechanical properties. Therefore, the first step in preparing chromium oxide is to approach a stoichiometric ratio of 2:3, and then adjust the structure and density to meet the requirements of wear-resistant applications.

[0038] The thickness of the oxide layer is 1 to 3 μm. It should be noted that the thickness of the oxide layer can be determined according to specific applications.

[0039] The hardness of the dense oxide coating is at least 30 GPa, which can give full play to the characteristics of the coating.

[0040] This application relates to a dense oxide coating with good density and wear resistance.

[0041] This application relates to a physical vapor deposition method for the dense oxide coating as described above. The physical vapor deposition method prepares a dense oxide coating on the substrate surface, with good film formation quality, high deposition rate, and low cost, and the prepared coating has good density.

[0042] The physical vapor deposition method includes the following technological processes.

[0043] S1, Load the substrate into the deposition chamber.

[0044] S2, Evacuate and heat the deposition chamber, and perform ion cleaning on the substrate.

[0045] S3, Introduce an inert gas, turn on the Cr target, and deposit a metal layer on the substrate surface by bipolar pulse magnetron sputtering.

[0046] S4. The deposition chamber is evacuated, and a mixed gas of oxygen and an inert gas is introduced. The flow rate ratio of oxygen to the inert gas is from 3:1 to 2:1. The Cr target is turned on, and an oxide layer is deposited on the surface of the metal layer by bipolar pulsed magnetron sputtering. The deposition time is 1 to 5 minutes.

[0047] S5. The flow rate ratio of oxygen to the inert gas is changed to from 1.5:1 to 1:1, and bipolar pulsed magnetron sputtering is continued to deposit the oxide layer. The deposition time is 60 to 180 minutes.

[0048] It should be noted that the inert gas introduced into the deposition chamber is argon.

[0049] In step S1, the substrate is made of metal, silicon wafer, ceramic, or cemented carbide.

[0050] In step S2, the deposition chamber is heated to 100 to 300 °C.

[0051] In step S3 during the deposition of the metal layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.3 to 0.5 Pa, and the frequency is 50 to 100 kHz. In steps S4 and S5 during the deposition of the oxide layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.4 to 0.55 Pa, and the frequency is 50 to 100 kHz.

[0052] It should be noted that in steps S3 to S5, the power density of the target material can determine the deposition rate. Therefore, by setting a reasonable power density, the deposition rate of the coating can be effectively controlled. The bias voltage improves the density of the coating. Too small a bias voltage will result in the inability to improve the density of the coating, and too large a bias voltage will result in excessive residual stress in the coating, affecting the coating adhesion. The gas pressure affects the stability of the coating deposition. Too low a gas pressure makes it difficult to initiate glow discharge and the glow is not easy to maintain, and too high a gas pressure will lead to a decrease in the deposition rate of the coating. During the coating preparation process, a higher frequency helps to reduce the arcing phenomenon caused by target poisoning. Through reasonable regulation of the power density, bias voltage, and gas pressure, the high-efficiency deposition of the metal layer and the oxide layer is achieved.

[0053] In step S4, by controlling the flow rate ratio of oxygen to the inert gas to be from 3:1 to 2:1, the target material quickly enters the poisoned state to form a stoichiometric oxide layer, ensuring the mechanical properties of the coating. In step S5, the flow rate ratio is reduced to from 1.5:1 to 1:1 to maintain the poisoned state of the target material to obtain a stoichiometric oxide layer, ensuring the mechanical properties of the coating.

[0054] Compared with the flow rate ratio of the mixed gas in step S4, the flow rate ratio is reduced in step S5, thereby reducing the oxygen partial pressure in the mixed gas and preventing the adverse effects of excessive oxygen incorporation on the performance of the oxide layer. Furthermore, a dense coating with excellent mechanical properties is prepared. It can not only ensure the formation of stoichiometric oxides but also minimize the adverse effects of excessive oxygen after target poisoning on the density, cleanliness, and even mechanical properties of the oxides.

[0055] By regulating the flow rate ratio of oxygen and argon in stages, the oxygen partial pressure is reduced after target poisoning to balance the relationship between stoichiometry and the density and mechanical properties of the coating, thereby maximizing the improvement and optimization of the coating performance and expanding the process window for preparing dense oxide coatings with excellent mechanical properties.

[0056] In the physical vapor deposition method, the coating is deposited by bipolar pulsed magnetron sputtering. The two targets work alternately, effectively suppressing the accumulation of target surface charges, thereby significantly reducing the risk of arcing on the target surface and improving the stability of the deposition process.

[0057] The content of the present application will be described in detail below with specific examples and comparative examples. It should be noted that the following description is only for illustrative purposes and not a specific limitation of the present application.

[0058] Comparative Example

[0059] The substrate is made of cemented carbide. After ultrasonic cleaning and drying, the substrate is loaded into the deposition chamber of the coating equipment, evacuated to the specified conditions, and the substrate is subjected to ion cleaning.

[0060] Argon is introduced, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -100 V, the gas pressure is 0.5 Pa, the frequency is 100 kHz, the deposition time is set to 5 min, and a Cr layer is deposited as the metal layer, and the thickness of the metal layer is 0.45 μm.

[0061] The Cr target is turned off, the argon supply is stopped, the chamber is evacuated, a mixed gas of oxygen and argon is introduced, the flow rate ratio of oxygen and argon is 6:5, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -100 V, the gas pressure is 0.5 Pa, the frequency is 100 kHz, the deposition time is set to 180 min, and a Cr2O3 layer is deposited as the oxide layer, and the thickness of the oxide layer is 6 μm.

[0062] A dense oxide coating with a Cr2O3 layer is obtained through the above steps. The structural formula of the oxide layer is Cr x O y , where x is 80.4 at.%, and y is 19.6 at.%.

[0063] Example 1

[0064] The substrate is made of cemented carbide. After ultrasonic cleaning and drying, the substrate is loaded into the deposition chamber of the coating equipment, evacuated to the approved conditions, and the substrate is subjected to ion cleaning.

[0065] Argon is introduced, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -50 V, the gas pressure is 0.33 Pa, the frequency is 100 kHz, the deposition time is set to 5 min, and a Cr layer is deposited as the metal layer, and the thickness of the metal layer is 0.45 μm.

[0066] The Cr target is turned off, the argon supply is stopped, the chamber is evacuated, a mixed gas of oxygen and argon is introduced, the flow rate ratio of oxygen to argon is 2:1, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -50 V, the gas pressure is 0.48 Pa, the frequency is 100 kHz, the deposition time is set to 120 min, and a Cr2O3 layer is deposited as the oxide layer, and the thickness of the oxide layer is 1.7 μm.

[0067] After the above steps, a dense oxide coating with a Cr2O3 layer is obtained. The structural formula of the oxide layer is Cr x O y , where x is 41.2 at.%, and y is 58.8 at.%.

[0068] Example 2

[0069] The substrate is made of cemented carbide. After ultrasonic cleaning and drying, the substrate is loaded into the deposition chamber of the coating equipment, evacuated to the approved conditions, and the substrate is subjected to ion cleaning.

[0070] Argon is introduced, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -50 V, the gas pressure is 0.33 Pa, the frequency is 100 kHz, the deposition time is set to 5 min, and a Cr layer is deposited as the metal layer, and the thickness of the metal layer is 0.45 μm.

[0071] The Cr target is turned off, the argon supply is stopped, the chamber is evacuated, a mixed gas of oxygen and argon is introduced, the flow rate ratio of oxygen to argon is 2:1, the Cr target is turned on, and the power density of the target is set to 10.9 W / cm 2 , the bias voltage is -50 V, the gas pressure is 0.48 Pa, the frequency is 100 kHz, the deposition time is set to 1 min, and a Cr2O3 layer is deposited.

[0072] Afterwards, the flow rate ratio of oxygen to argon was reduced to 1:1, and other deposition conditions remained unchanged. The set pressure was 0.4 Pa, the deposition time was 120 min, and a Cr2O3 layer was deposited. The thickness of the oxide layer was 1.9 μm.

[0073] After the above steps, a dense oxide coating with a Cr2O3 layer was obtained. The structural formula of the oxide layer was Cr x O y , where x was 42.0 at.%, and y was 58.0 at.%.

[0074] As shown in Table 1, energy dispersive spectrometer analysis showed that the Cr content in the coating of the comparative example was 80.4 at.%, and the O content was 19.6 at.%. The Cr content in the coating of Example 1 was 41.2 at.%, and the O content was 58.8 at.%. The Cr content in the coating of Example 2 was 42.0 at.%, and the O content was 58.0 at.%. The above data indicated that the coating in the comparative example was oxygen-deficient, while the Cr / O in the coatings of Examples 1 and 2 was close to the stoichiometric ratio.

[0075] Table 1

[0076]

[0077] As Figure 1 shown, the coating in Example 2 showed a higher crystallinity, and all the diffraction peaks belonged to the hexagonal Cr2O3 structure. The (110), (202), (024), (214), and (220) diffraction peaks could be identified from the X-ray diffraction (XRD) pattern. Due to the presence of compressive stress, the XRD diffraction peaks were all shifted towards lower angles.

[0078] As Figure 2 shown, Figure (a) showed that there were many droplet defects on the surface of the coating in Example 1, and it was relatively rough. Figure (b) showed that the surface of the coating in Example 2 was smooth, and there were almost no droplet defects. This indicated that reducing the oxygen partial pressure helped to reduce the degree of target poisoning, reduce the risk of arcing on the target surface, and thus reduce the droplet defects on the coating surface and the surface roughness of the coating.

[0079] As Figure 3 shown, Figures (a) and (c) showed that the coating in Example 1 had a columnar crystal structure, and Figures (b) and (d) showed that the density of the coating in Example 2 was improved, and it was a dense glassy structure. This was because after reducing the oxygen partial pressure, the excessive incorporation of oxygen after target poisoning was effectively reduced, thereby reducing the adverse effect on the density of the coating and improving the density of the coating.

[0080] As Figure 4As shown, the hardness of the coating in the comparative example is 16.8 ± 0.3 GPa, and the elastic modulus is 280 ± 10 GPa. The hardness of the coating in Example 1 is 25.8 ± 0.7 GPa, and the elastic modulus is 352 ± 9 GPa. It can be seen that by increasing the flow rate ratio of oxygen to argon from 6:5 to 2:1, a stoichiometric coating can be prepared, thereby improving the mechanical properties of the coating.

[0081] In addition, the hardness of the coating in Example 1 is 25.88 ± 0.7 GPa, and the elastic modulus is 352 ± 9 GPa. The hardness of the coating in Example 2 is 30.3 ± 0.9 GPa, and the elastic modulus is 321 ± 9 GPa. It can be seen that, under the condition that other conditions remain unchanged, by reducing the flow rate ratio of oxygen to argon, thereby reducing the oxygen partial pressure while maintaining the poisoned state of the target, the hardness of the coating can be increased to a certain extent (increased by 17.4%), and its mechanical properties can be improved. This is because reducing the oxygen partial pressure can reduce the excessive incorporation of oxygen after target poisoning, thereby reducing the adverse effects on the density and properties of the coating, and thus improving the mechanical properties of the coating.

[0082] The embodiments of the present application have been described in detail above with reference to the accompanying drawings. However, the present application is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A physical vapor deposition method for a dense oxide coating, characterized in that: Including Loading a substrate into a deposition chamber; Evacuating and heating the deposition chamber to perform ion cleaning on the substrate; Introducing an inert gas, turning on the Cr target, and depositing a metal layer on the surface of the substrate by bipolar pulse magnetron sputtering; Evacuating the deposition chamber, introducing a mixed gas of oxygen and an inert gas with a flow rate ratio of oxygen to inert gas of 3:1 to 2:1, turning on the Cr target, and depositing an oxide layer on the surface of the metal layer by bipolar pulse magnetron sputtering, with a deposition time of 1 to 5 minutes; Changing the flow rate ratio of oxygen to inert gas to 1.5:1 to 1:1, and continuously depositing the oxide layer by bipolar pulse magnetron sputtering for a deposition time of 60 to 180 minutes.

2. The physical vapor deposition method of the dense oxide coating according to claim 1, wherein: During the process of depositing the metal layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.3 to 0.5 Pa, and the frequency is 50 to 100 kHz.

3. The physical vapor deposition method of the dense oxide coating according to claim 1, characterized in that: During the process of depositing the oxide layer, the power density of the sputtering target is 10 to 15 W / cm 2 , the bias voltage is -50 to -150 V, the gas pressure is 0.4 to 0.5 Pa, and the frequency is 50 to 100 kHz.

4. The physical vapor deposition method of the dense oxide coating according to any one of claims 1 to 3, characterized in that: The substrate is made of metal, ceramic, or cemented carbide.

5. A dense oxide coating, characterized in that: The dense oxide coating is obtained by the physical vapor deposition method according to any one of claims 1 to 4. The dense oxide coating includes a metal layer and an oxide layer. The metal layer contains Cr element, and the oxide layer is deposited on the surface of the metal layer. The oxide layer contains Cr element and oxygen element.

6. The dense oxide coating according to claim 5, wherein: The chemical formula of the oxide layer is Cr x O y , where x is 35 to 45 at.%, and y is 55 to 65 at.%.

7. The dense oxide coating according to claim 5, wherein: The thickness of the metal layer is 0.2 to 0.5 μm.

8. The dense oxide coating according to claim 5, wherein: The thickness of the oxide layer is 1 to 3 μm.

9. The dense oxide coating according to any one of claims 5 to 8, characterized in that: The hardness of the dense oxide coating is at least 30 GPa.

10. Use of a dense oxide coating as described in any one of claims 5 to 9, characterized in that: The dense oxide coating is applied to the surface strengthening of tools, ceramics, or mechanical components.

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