CrAlBN protective coating and preparation method thereof as well as composite coating and preparation method thereof

Abstract

The invention provides a CrAlBN protective coating, a preparation method of the CrAlBN protective coating, a composite coating and a preparation method of the composite coating, and belongs to the technical field of hard protective coatings. According to the method, B is doped in the CrAlN coating, and the doping amount of B is controlled to be 0.6-6.0 at.%, so that the CrAlBN protective coating has low roughness and excellent crystallinity, and the internal organization structure has high density. The result of the embodiment shows that when the content of B is 1.3 at.%, the hardness of the CrAlBN protective coating is 35.4 GPa, the elasticity modulus is 418.6 GPa, the fracture toughness is 1.72 MPa.m < 1 / 2 >, the friction coefficient is 0.82, the corrosion current density of the CrAlBN protective coating is 7.88 * 10 <-8 > A.cm <-2 >, and the CrAlBN protective coating has excellent friction performance, high hardness, high toughness and corrosion resistance.

Description

Technical Field

[0001] The present invention relates to the technical field of hard protective coatings, and in particular to a CrAlBN protective coating and a preparation method thereof, and a composite coating and a preparation method thereof. Background Art

[0002] In modern materials science and engineering, coating technology, as a key means of improving material surface properties, plays an indispensable role in numerous industrial fields. CrAlN coatings, due to their excellent hardness, wear resistance, and corrosion resistance, have become a research hotspot in the field of surface protection.

[0003] Although CrAlN coatings have excellent properties such as hardness, wear resistance, and corrosion resistance, their toughness is relatively poor. This is because: First, CrAlN coatings are nitride ceramic coatings, and atoms are mainly bonded by strong covalent bonds and ionic bonds. Covalent bonds are directional and saturated. When the material is subjected to external forces, it is difficult for atoms to absorb energy through plastic deformation such as slip. When stress is concentrated, the bonds will break directly, forming cracks that expand rapidly, leading to brittle fracture. Second, in order for CrAlN coatings to achieve high hardness, the microstructure of CrAlN needs to have a high density, and plastic deformation mechanisms such as dislocation movement are greatly suppressed. This results in the material's poor ability to plastically deform under stress, and energy cannot be dissipated through plastic deformation, but can only be released through the formation and expansion of cracks, which manifests as low toughness. However, with the continuous development of industrial technology, more stringent requirements have been placed on the performance of CrAlN coatings. In addition to traditional properties such as hardness, wear resistance, and corrosion resistance, good toughness is also required.

[0004] Therefore, how to obtain a CrAlBN protective coating with high hardness, high toughness, high wear resistance and corrosion resistance has become a technical problem that needs to be solved urgently in this field. Summary of the Invention

[0005] The object of the present invention is to provide a CrAlBN protective coating with high hardness, high toughness, high wear resistance and corrosion resistance, a preparation method thereof, and a composite coating and a preparation method thereof.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a CrAlBN protective coating, which comprises the following components in atomic percentage: 15.0-18.1 at.% of Cr, 36.0-39.6 at.% of Al, 34.4-34.9 at.% of N, 0.6-6.0 at.% of B and 6.6-8.5 at.% of O;

[0008] The roughness of the CrAlBN protective coating is 77.0±8 nm.

[0009] Preferably, the thickness of the CrAlBN protective coating is 1.9-2.9 μm.

[0010] The present invention also provides a method for preparing the CrAlBN protective coating according to the above technical solution, comprising: performing a first multi-arc ion plating deposition on a substrate to obtain a CrAlBN protective coating;

[0011] The target material of the first multi-arc ion plating deposition is a CrAlB metal target material, and the first multi-arc ion plating deposition parameters include: a bias voltage of -60 to -80 V; an arc current of 80 to 100 A; and a nitrogen flow rate of 200 to 500 sccm.

[0012] The present invention also provides a composite coating, which comprises, from bottom to top, a Cr layer, a CrAl transition layer and a protective layer; the protective layer is the CrAlBN protective coating described in the above technical solution or the CrAlBN protective coating prepared by the preparation method described in the above technical solution.

[0013] Preferably, the thickness of the Cr layer is 0.3-0.5 nm.

[0014] Preferably, the thickness of the CrAl transition layer is 0.5-1 nm.

[0015] Preferably, the thickness of the protective layer is 1.9-2.9 μm.

[0016] The present invention also provides a method for preparing the composite coating described in the above technical solution, comprising the following steps:

[0017] (1) polishing, ultrasonic cleaning, and ion cleaning the substrate in sequence to obtain a pretreated substrate;

[0018] (2) performing a second multi-arc ion plating deposition on the surface of the pretreated substrate obtained in step (1) to obtain a deposited Cr layer substrate;

[0019] (3) performing a third multi-arc ion plating deposition on the surface of the deposited Cr layer substrate obtained in step (2) to obtain a deposited transition layer substrate;

[0020] (4) performing a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate obtained in step (3) to obtain a composite coating.

[0021] Preferably, the parameters of the second multi-arc ion plating deposition in step (2) include: a vacuum degree of 1 to 3×10 -3Pa; temperature is 350-450°C; Ar gas flow rate is 100-300 sccm; bias voltage is -60--120 V; current is 80-100 A; N2 flow rate is 100-500 sccm; turntable speed is 4-8 r / min; deposition time is 10-30 min; target substrate distance is 240 mm.

[0022] Preferably, the parameters of the third multi-arc ion plating deposition in step (3) include: a vacuum degree of 1 to 3×10 -3 Pa; temperature is 350~450℃; Ar gas flow rate is 100~300sccm; bias voltage is -60~-120V; current is 80~120A; N2 flow rate is 100~500sccm; turntable speed is 4~8r / min; deposition time is 10~30min; target substrate distance is 240mm.

[0023] The present invention provides a CrAlBN protective coating. The CrAlBN protective coating comprises the following components, calculated in atomic percentage: 15.0 to 18.1 at.% Cr, 36.0 to 39.6 at.% Al, 34.4 to 34.9 at.% N, 0.6 to 6.0 at.% B, and 6.6 to 8.5 at.% O. The CrAlBN protective coating has a roughness of 77.0 ± 8 nm. The present invention achieves low roughness by doping the CrAlN coating with boron, controlling the boron doping amount to 0.6 to 6.0 at.%. This makes the CrAlBN protective coating mainly composed of CrN, AlN and α-BN phases in terms of crystal structure, showing typical face-centered cubic crystal structure characteristics. In addition, during the crystal growth process, the (111) and (220) directions of CrN are preferentially oriented. When the B atomic percentage content is 1.3 at.% (abbreviated as 1.3 at.%), the CrAlBN protective coating has excellent crystallinity and a high degree of density of the internal structure. When the B content is 1.3 at.%, the hardness of the CrAlBN protective coating is 35.4 GPa, the elastic modulus is 418.6 GPa, and the fracture toughness is 1.72 MPa·m 1 / 2 , with high hardness and high toughness. In terms of stress state, all CrAlBN protective coatings are under compressive stress, and the internal stress of the coating shows a trend of first decreasing and then increasing with the change of B content, and the internal stress is as low as -480MPa. In addition, the friction performance of the CrAlBN protective coating also changes with the change of B content, and the friction coefficient shows a trend of first decreasing and then increasing. When the B content is 3.0at.%, the friction coefficient is 0.82. In terms of corrosion resistance, when the B content reaches 3.0at.%, the CrAlBN protective coating exhibits excellent corrosion resistance. At this time, the corrosion current density of the CrAlBN protective coating reaches 7.88×10-8 A.cm -2 . Compared with film layers with other B contents, the corrosion current density of the coating with a B content of 3.0 at.% is reduced by 1 to 2 orders of magnitude. This result shows that when the B content is 3.0 at.%, the CrAlBN protective coating has excellent resistance to erosion by corrosive media. This is because the coating forms a more stable and dense passivation film at this content, reducing corrosion channels and effectively hindering the progress of the corrosion reaction. It can be seen that the CrAlBN protective coating provided by the present invention has high hardness and high toughness, as well as excellent corrosion resistance and friction properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 XRD patterns of the CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0025] Figure 2 This is a cross-sectional TEM image of the CrAlBN protective coating prepared in Example 3 of the present invention;

[0026] Figure 3 SEM images of cross sections of CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0027] Figure 4 The roughness of the cross section of the CrAlBN protective coating prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0028] Figure 5 The fracture toughness of the CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 varies with the B content;

[0029] Figure 6 The internal stress of the CrAlBN protective coating prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0030] Figure 7 Friction curves of the CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2;

[0031] Figure 8 The friction coefficient change curves of the CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 are shown;

[0032] Figure 9 Polarization curves of the CrAlBN protective coatings prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 2 in 3.5 wt.% NaCl solution. DETAILED DESCRIPTION

[0033] The present invention provides a CrAlBN protective coating, which comprises the following components in atomic percentage: 15.0-18.1 at.% of Cr, 36.0-39.6 at.% of Al, 34.4-34.9 at.% of N, 0.6-6.0 at.% of B and 6.6-8.5 at.% of O;

[0034] The roughness of the CrAlBN protective coating is 77.0±8 nm.

[0035] In terms of atomic percentage, the CrAlBN protective coating provided by the present invention includes 15.0 to 18.1 at.% of Cr. As one embodiment of the present invention, the atomic percentage of Cr may be 15.0 at.%, 16.0 at.%, 16.5 at.%, 17.1 at.%, 17.6 at.%, or 18.1 at.%. By controlling the atomic percentage of Cr within the above range, the present invention can provide the CrAlBN protective coating with basic hardness, corrosion resistance, and good adhesion.

[0036] In terms of atomic percentage, the CrAlBN protective coating provided by the present invention comprises 36.0 to 39.6 at.% Al. As one embodiment of the present invention, the atomic percentage of Al may be 36.0 at.%, 36.2 at.%, 38.2 at.%, 39.4 at.%, or 39.6 at. By controlling the atomic percentage of Al within the above range, the present invention can form Al2O3 and Al nitride, thereby improving the hardness of the CrAlBN protective coating.

[0037] The CrAlBN protective coating provided by the present invention includes 34.4 to 34.9 at.% nitrogen, measured in atomic percentage. As one embodiment of the present invention, the atomic percentage of nitrogen may be 34.4 at.%, 34.5 at.%, 34.6 at.%, 34.7 at.%, or 34.9 at. By controlling the atomic percentage of nitrogen within the aforementioned range, the present invention can form a variety of nitrides in the coating, such as by forming ultrahard c-BN and lubricating h-BN, refining grains, improving the hardness, wear resistance, and toughness of the CrAlBN protective coating, and reducing the coefficient of friction.

[0038] The CrAlBN protective coating provided by the present invention includes 0.6 to 6.0 at.% of B, calculated in atomic percentage. As one embodiment of the present invention, the atomic percentage of B may be 0.6 at.%, 1.3 at.%, 3.0 at.%, 4.8 at.%, or 6.0 at.%. By controlling the atomic percentage of B within the above range, the present invention can refine grains, reduce coating roughness, and improve the hardness and toughness of the CrAlBN protective coating.

[0039] In terms of atomic percentage, the CrAlBN protective coating provided by the present invention includes 6.6 to 8.5 at.% of O. As an embodiment of the present invention, the atomic percentage of O can be 6.6 at.%, 7.1 at.%, 7.3 at.%, 7.8 at.%, or 8.5 at.%.

[0040] In the present invention, the roughness of the CrAlBN protective coating is 77.0±8 nm. The roughness of the CrAlBN protective coating provided by the present invention is within the above range and has excellent quality, so that the CrAlBN protective coating has excellent hardness and toughness.

[0041] In the present invention, the thickness of the CrAlBN protective coating is preferably 1.9 to 2.9 μm. As an embodiment of the present invention, the thickness of the CrAlBN protective coating can be 1.91 μm, 2.13 μm, 2.47 μm, 2.75 μm or 2.84 μm.

[0042] The present invention also provides a method for preparing the CrAlBN protective coating described in the above technical solution, comprising: performing a first multi-arc ion plating deposition on a substrate to obtain the CrAlBN protective coating.

[0043] In the present invention, the substrate preferably includes a 304 stainless steel substrate or single crystal Si. The present invention has no particular limitation on the source of the 304 stainless steel substrate or single crystal Si, and any conventional commercially available product can be used.

[0044] The present invention preferably sequentially polishes, ultrasonically cleans, and ion cleans the substrate to obtain a pretreated substrate. The present invention does not particularly limit the polishing and ultrasonic cleaning methods; conventional polishing and ultrasonic cleaning can be used to fully remove impurities from the substrate surface. In an embodiment of the present invention, the ultrasonic cleaning power can be 15 to 30 kHz, and the ultrasonic cleaning time can be 30 minutes.

[0045] In an embodiment of the present invention, the ion cleaning method may be: placing the substrate into a vacuum chamber of a multi-arc ion plating instrument, evacuating the chamber to a vacuum of 2×10 -3 After Pa, Ar gas was introduced, the bias voltage was set to -400 V, and the target was bombarded with argon ions for 10 min.

[0046] After obtaining the pretreated substrate, the present invention preferably performs a second multi-arc ion plating deposition on the surface of the pretreated substrate to obtain a deposited Cr layer substrate.

[0047] In the present invention, the parameters of the second multi-arc ion plating deposition preferably include: the vacuum degree is preferably 1 to 3×10 - 3 Pa, more preferably 2×10-3 Pa; the temperature is preferably 350-450°C, more preferably 400-420°C; the Ar gas flow rate is preferably 100-300 sccm, more preferably 100 sccm; the bias voltage is preferably -60--120V, more preferably -100V; the current is preferably 80-120A, more preferably 100A; the N2 flow rate is preferably 100-500 sccm, more preferably 300 sccm; the turret speed is preferably 4-8 r / min, more preferably 6 r / min; the deposition time is preferably 10-30 min, more preferably 20 min; the target-substrate distance is preferably 240 mm. The present invention has no special limitation on the apparatus for the second multi-arc ion plating deposition, and any conventional multi-arc ion plating instrument can be used.

[0048] In the present invention, the target material for the second multi-arc ion plating deposition is preferably a Cr metal target material, and the purity of the Cr metal target material is preferably ≥99.95%. In an embodiment of the present invention, the outer diameter of the Cr metal target material can be 150 mm, the inner diameter can be 138 mm, and the thickness can be 20 mm.

[0049] After obtaining the deposited Cr layer substrate, the present invention preferably performs a third multi-arc ion plating deposition on the surface of the deposited Cr layer substrate to obtain a deposited transition layer substrate.

[0050] In the present invention, the parameters of the third multi-arc ion plating deposition preferably include: the vacuum degree is preferably 1 to 3×10 - 3 Pa, more preferably 2×10 -3 Pa; the temperature is preferably 350-450°C, more preferably 400-420°C; the Ar gas flow rate is preferably 100-300 sccm, more preferably 100 sccm; the bias voltage is preferably -60--120V, more preferably -100V; the current is preferably 80-120A, more preferably 100A; the N2 flow rate is preferably 100-500 sccm, more preferably 300 sccm; the turret speed is preferably 4-8 r / min, more preferably 6 r / min; the deposition time is preferably 10-30 min, more preferably 20 min; the target-substrate distance is 240 mm. The present invention does not specifically limit the apparatus for the third multi-arc ion plating deposition, and any conventional multi-arc ion plating instrument can be used.

[0051] In the present invention, the target material of the third multi-arc ion plating deposition is preferably a CrAl metal target material, more preferably a CrAl metal target material. 50 Al 50Alloy target: The purity of the CrAl metal target is preferably ≥99.95%. In an embodiment of the present invention, the outer diameter of the CrAl metal target can be 150 mm, the inner diameter can be 138 mm, and the thickness can be 20 mm.

[0052] After obtaining the deposition transition layer substrate, the present invention preferably performs a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate to obtain a composite coating.

[0053] In the present invention, the target material for the first multi-arc ion plating deposition is preferably a CrAlB metal target material, more preferably an Al 63 Cr 27 B 10 Alloy target; the purity of the CrAlB metal target is preferably ≥99.95%.

[0054] In the present invention, the first multi-arc ion plating deposition parameters preferably include: a bias voltage of -60 to -80 V; an arc current of 80 to 100 A; and a nitrogen flow rate of 200 to 500 sccm. As an embodiment of the present invention, the bias voltage may be -60 V, -65 V, -70 V, -75 V, or -80 V; and the nitrogen flow rate may be 200 sccm, 300 sccm, 400 sccm, or 500 sccm. In the present invention, if the current is too high, it will promote the nucleation of large particles, thereby reducing the density of the coating. When the bias voltage is too large, the energy density of the plasma will increase significantly, which will produce a large number of molten droplets on the surface of the substrate, thereby causing defects on the coating surface, resulting in reduced hardness and fracture toughness of the CrAlBN protective coating. Therefore, the present invention controls the first multi-arc ion plating deposition parameters within the above range, which can enable the CrAlBN protective coating to have excellent hardness, elastic modulus, fracture toughness, and friction properties.

[0055] The present invention also provides a composite coating, which comprises, from bottom to top, a Cr layer, a CrAl transition layer and a protective layer.

[0056] In the present invention, the protective layer is the CrAlBN protective coating described in the above technical solution, which will not be described in detail here.

[0057] In the present invention, the thickness of the Cr layer is preferably 0.3 to 0.5 nm, more preferably 0.3 to 0.4 nm. By depositing the Cr layer, the present invention can enhance the bonding strength between the layers, providing a good bonding foundation for the subsequent deposition and growth of the transition layer and protective layer.

[0058] In the present invention, the thickness of the CrAl transition layer is preferably 0.5 to 1 nm, more preferably 0.5 to 0.8 nm.

[0059] In the present invention, the thickness of the protective layer is preferably 1.9 to 2.9 μm. As one embodiment of the present invention, the thickness of the protective layer can be 1.91 μm, 2.13 μm, 2.47 μm, 2.75 μm, or 2.84 μm. The protective layer provided by the present invention has excellent density, so controlling the thickness within the above range can ensure that the composite coating has excellent hardness and toughness.

[0060] The present invention can improve the bonding strength between the protective layer and the substrate by providing a Cr layer and a CrAl transition layer; moreover, the effective combination of the multi-layer coating structure of the present invention makes the composite coating have excellent comprehensive mechanical properties, improves the hardness and toughness of the composite coating, and effectively overcomes the stress existing between different layers due to differences in physical expansion properties, thereby preventing it from falling off and significantly extending the service life of the composite coating.

[0061] The composite coating provided by the present invention can be used on the surface of a tool to improve the hardness and corrosion resistance of the tool head and increase the life of the tool.

[0062] The present invention also provides a method for preparing the composite coating described in the above technical solution, comprising the following steps:

[0063] (1) polishing, ultrasonic cleaning, and ion cleaning the substrate in sequence to obtain a pretreated substrate;

[0064] (2) performing a second multi-arc ion plating deposition on the surface of the pretreated substrate obtained in step (1) to obtain a deposited Cr layer substrate;

[0065] (3) performing a third multi-arc ion plating deposition on the surface of the deposited Cr layer substrate obtained in step (2) to obtain a deposited transition layer substrate;

[0066] (4) performing a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate obtained in step (3) to obtain a composite coating.

[0067] The present invention performs polishing, ultrasonic cleaning and ion cleaning on the substrate in sequence to obtain a pretreated substrate.

[0068] In the present invention, the substrate preferably includes a 304 stainless steel substrate or single crystal Si, more preferably a stainless steel cutting tool. The present invention has no particular limitation on the source of the 304 stainless steel substrate or single crystal Si, and any conventional commercially available product can be used.

[0069] The present invention has no particular limitation on the polishing and ultrasonic cleaning methods. Conventional polishing and ultrasonic cleaning can be used to fully remove impurities on the substrate surface. In an embodiment of the present invention, the ultrasonic cleaning power can be 15 to 30 kHz, and the ultrasonic cleaning time can be 30 minutes.

[0070] In an embodiment of the present invention, the ion cleaning method may be: placing the substrate into a vacuum chamber, evacuating the chamber to a vacuum of 2×10 -3 After Pa, Ar gas was introduced, the bias voltage was set to -400 V, and the target was bombarded with argon ions for 10 min.

[0071] After obtaining the pretreated substrate, the present invention performs a second multi-arc ion plating deposition on the surface of the pretreated substrate to obtain a deposited Cr layer substrate.

[0072] In the present invention, the parameters of the second multi-arc ion plating deposition preferably include: the vacuum degree is preferably 1 to 3×10 - 3 Pa, more preferably 2×10 -3 Pa; the temperature is preferably 350-450°C, more preferably 400-420°C; the Ar gas flow rate is preferably 100-300 sccm, more preferably 100-200 sccm; the bias voltage is preferably -60--120V, more preferably -100V; the current is preferably 80-120A, more preferably 100A; the N2 flow rate is preferably 100-500 sccm, more preferably 300 sccm; the turret speed is preferably 4-8 r / min, more preferably 6 r / min; the deposition time is preferably 10-30 min, more preferably 20 min; the target-substrate distance is 240 mm. The present invention does not specifically limit the apparatus for the second multi-arc ion plating deposition, and any conventional multi-arc ion plating instrument can be used.

[0073] In the present invention, the target material for the second multi-arc ion plating deposition is preferably a Cr metal target material, and the purity of the Cr metal target material is preferably 99.95%. In an embodiment of the present invention, the outer diameter of the Cr metal target material can be 150 mm, the inner diameter can be 138 mm, and the thickness can be 20 mm.

[0074] After obtaining the deposited Cr layer substrate, the present invention performs a third multi-arc ion plating deposition on the surface of the deposited Cr layer substrate to obtain a deposited transition layer substrate.

[0075] In the present invention, the parameters of the third multi-arc ion plating deposition preferably include: the vacuum degree is preferably 1 to 3×10 - 3 Pa, more preferably 2.0×10 -3Pa; the temperature is preferably 350-450°C, more preferably 400-420°C; the Ar gas flow rate is preferably 100-300sccm, more preferably 100sccm; the bias voltage is preferably -60--120V, more preferably -100V; the current is preferably 80-120A, more preferably 100A; the N2 flow rate is preferably 100-500sccm, more preferably 300sccm; the turntable speed is preferably 4-8r / min, more preferably 6r / min; the deposition time is preferably 10-30min, more preferably 20min; the target substrate distance is 240mm.

[0076] In the present invention, the target material of the third multi-arc ion plating deposition is preferably a CrAl metal target material, more preferably a CrAl metal target material. 50 Al 50 alloy target; the purity of the CrAl metal target is preferably ≥99.95%. In an embodiment of the present invention, the CrAl metal target can have an outer diameter of 150 mm, an inner diameter of 138 mm, and a thickness of 20 mm. The present invention does not particularly limit the apparatus for the third multi-arc ion plating deposition; a conventional multi-arc ion plating instrument can be used.

[0077] After obtaining the deposition transition layer substrate, the present invention performs a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate to obtain a composite coating.

[0078] In the present invention, the target material for the first multi-arc ion plating deposition is preferably a CrAlB metal target material, more preferably an Al 63 Cr 27 B 10 Alloy target; the purity of the CrAlB metal target is preferably ≥99.95%.

[0079] In the present invention, the first multi-arc ion plating deposition parameters preferably include: a bias voltage of preferably -60 to -80 V; an arc current of 80 to 100 A; and a nitrogen flow rate of 200 to 500 sccm. As one embodiment of the present invention, the bias voltage may be -60 V, -65 V, -70 V, -75 V, or -80 V; and the nitrogen flow rate may be 200 sccm, 300 sccm, 400 sccm, or 500 sccm. In the present invention, if the current is too high, it will promote the nucleation of large particles, thereby reducing the density of the coating. When the bias voltage is too high, the energy density of the plasma will increase significantly, which will produce a large number of molten droplets on the substrate surface, thereby causing defects on the coating surface. This will further reduce the hardness and fracture toughness of the CrAlBN protective coating. Therefore, the present invention controls the first multi-arc ion plating deposition parameters within the above range, which can enable the CrAlBN protective coating to have excellent hardness, elastic modulus, fracture toughness, friction coefficient, and internal stress.

[0080] The method provided by the present invention has the advantages of simple operation, fast deposition speed, low cost, high bonding strength, etc., and can obtain a composite coating with high hardness, high toughness, high wear resistance and corrosion resistance, thereby improving the service life of the tool.

[0081] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0082] Example 1

[0083] A method for preparing a CrAlBN protective coating is as follows:

[0084] (1) The polished substrate (single crystal silicon wafer) is placed in an ultrasonic cleaning machine and cleaned for 30 minutes using 15-30 kHz ultrasonic waves in analytical pure anhydrous alcohol; then ion cleaning is performed; the ion cleaning method is as follows: the substrate is placed in a vacuum chamber of a multi-arc ion plating instrument and evacuated to 2×10 -3 After Pa, Ar gas was introduced, the bias voltage was set to -400 V, and the target was bombarded with argon ions for 10 min, and the introduction of Ar gas was stopped to obtain a pretreated substrate;

[0085] (2) introducing N2 gas and activating the Cr target at the same time, performing a second multi-arc ion plating deposition on the surface of the pretreated substrate to obtain a deposited Cr layer substrate;

[0086] The parameters of the second multi-arc ion plating deposition are as follows: the Cr target uses a Cr metal target material (99.95%), the target material has an outer diameter of 150 mm, an inner diameter of 138 mm, and a thickness of 20 mm; the vacuum degree is maintained at 2.0×10 -3 Pa, temperature maintained at 420°C; Ar gas flow rate: 100 sccm, bias voltage -100 V, current 100 A, N2 flow rate 300 sccm; turret speed 6 r / min, transition layer CrN deposition time 20 min; target substrate distance 240 mm;

[0087] (3) while maintaining the continuous flow of N2, the Cr target is turned off, the CrAl target is started, and a third multi-arc ion plating deposition is performed on the surface of the deposited Cr layer substrate obtained in step (2) to obtain a deposited transition layer substrate;

[0088] The parameters of the third multi-arc ion plating deposition are as follows: using a CrAl metal target with an outer diameter of 150 mm, an inner diameter of 138 mm, and a thickness of 20 mm; maintaining a vacuum degree of 2.0×10-3 Pa, temperature maintained at 420°C; Ar gas flow rate of 100 sccm, bias voltage of -100 V, current of 100 A, N2 flow rate of 300 sccm; turret speed of 6 r / min, transition layer CrAlN deposition time of 20 min; target substrate distance of 240 mm;

[0089] (4) keeping N2 flowing and the CrAl target turned on, while starting the CrAlB target, performing a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate obtained in step (3) to obtain a composite coating;

[0090] The parameters of the first multi-arc ion plating deposition are as follows: using a CrAlB metal target (99.95%) with an outer diameter of 150 mm, an inner diameter of 138 mm, and a thickness of 20 mm; maintaining a vacuum degree of 2.0×10 -3 Pa, the temperature was maintained at 420°C; the Ar gas flow rate was 100 sccm; the turret speed was 6 r / min, the deposition time was 40 min; the target substrate distance was 240 mm; the bias voltage was -80 V; the arc current was 80 A; and the nitrogen flow rate was 300 sccm.

[0091] The obtained CrAlBN protective coating (abbreviated as B-4) has the following components in atomic percentage as shown in Table 1. The test results show that the hardness of the CrAlBN protective coating prepared in this embodiment is 34.7 GPa, the elastic modulus is 410.1 GPa, and the fracture toughness is 1.64 MPa·m 1 / 2 .

[0092] Example 2

[0093] A method for preparing a CrAlBN protective coating, which differs from Example 1 in that the arc current in step (4) is 90 A, and the rest is the same as Example 1;

[0094] The obtained CrAlBN protective coating (abbreviated as B-3) has the following components in atomic percentage as shown in Table 1. The test results show that the hardness of the CrAlBN protective coating prepared in this embodiment is 35.4 GPa, the elastic modulus is 418.6 GPa, and the fracture toughness is 1.72 MPa·m 1 / 2 .

[0095] Example 3

[0096] A method for preparing a CrAlBN protective coating, which differs from Example 1 in that the arc current in step (4) is 100 A, and the rest is the same as Example 1;

[0097] The obtained CrAlBN protective coating (abbreviated as B-2) has the following components in atomic percentage as shown in Table 1. The test results show that the hardness of the CrAlBN protective coating prepared in this embodiment is 33.9 GPa, the elastic modulus is 380.2 GPa, and the fracture toughness is 1.61 MPa·m 1 / 2 .

[0098] Comparative Example 1

[0099] A method for preparing a CrAlBN protective coating, which differs from Example 1 in that the arc current in step (4) is 110 A, and the rest is the same as Example 1;

[0100] The obtained CrAlBN protective coating (abbreviated as B-1) has the following components in atomic percentage as shown in Table 1. The test results show that the hardness of the CrAlBN protective coating prepared in this embodiment is 33.5 GPa, the elastic modulus is 375.9 GPa, and the fracture toughness is 1.41 MPa·m 1 / 2 .

[0101] Comparative Example 2

[0102] A method for preparing a CrAlBN protective coating, which differs from Example 1 in that the arc current in step (4) is 70A, and the rest is the same as Example 1;

[0103] The obtained CrAlBN protective coating (abbreviated as B-5) has the following components in atomic percentage as shown in Table 1. The test results show that the hardness of the CrAlBN protective coating prepared in this embodiment is 30.7 GPa, the elastic modulus is 370.1 GPa, and the fracture toughness is 1.33 MPa·m 1 / 2 .

[0104] Test Example 1

[0105] (1) The atomic percentages of the elements in the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 1.

[0106] Table 1 Atomic percentage (at.%) of each element in CrAlBN protective coating

[0107] element B-1 B-2 B-3 B-4 B-5 Cr 18.1 17.6 17.1 16.5 15.0 Al 39.4 39.6 38.2 36.2 36.0 N 34.6 34.9 34.4 34.7 34.5 B 0.6 1.3 3.0 4.8 6.0 O 7.3 6.6 7.1 7.8 8.5

[0108] (2) The XRD patterns of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in FIG. Figure 1 As shown. Figure 1It can be seen that the CrAlBN protective coating has diffraction peaks at approximately 37.5°, 43.5° and 76°, corresponding to the (111), (200) and (311) crystal planes of the face-centered cubic structure of fcc-(Cr,Al)N crystal. This result indicates that the CrAlBN protective coating has the crystallographic orientation characteristics of the fcc-(Cr,Al)N phase. As the B content in the coating gradually increases, it can be found that the diffraction peak of the fcc-(Cr,Al)N phase shows a trend of moving toward higher angles. During this process, it was found through analysis that its Al / (Al+Cr) ratio remained stable at the level of 0.69. This information indicates that the shift of the peak position to higher angles at this time is not the result of the dissolution of Al elements into the fcc-CrN lattice structure. In order to clarify which atom of Al, Cr or N is replaced by B atoms in the fcc-(Cr,Al)N solid solution phase, a detailed calculation was carried out based on the thermodynamic principle, that is, the Gibbs free energy formula ΔG=ΔH-TΔS. The results show that ΔG(Cr)=-126.312 kJ·mol -1 , ΔG(N)=-13.669kJ·mol -1 , ΔG(Al)=54.495kJ·mol -1 From these data, it can be clearly seen that the Gibbs free energy change of B atoms replacing Cr atoms is negative and the absolute value is large, which means that thermodynamically, B atoms are more likely to replace Cr atoms and thus form fcc-CrAlBN solid solution. Figure 1 It can also be seen that, taking the B-2 coating as an example, the diffraction peak intensity of its (111) plane is significantly enhanced compared to that of the B-1 coating, and the peak width is also narrower. The intensity and width of the diffraction peak are closely related to the grain size. The increase in the diffraction peak intensity and the narrowing of the width usually indicate that the grain size in the coating has increased. This phenomenon shows that in the B-2 coating, the increase in the B element has a specific effect on grain growth, resulting in an increase in grain size. However, when the B content in the coating is further increased, the diffraction peak intensity of the (111) plane decreases sharply, and even disappears completely in some cases (such as the B-4 coating). This phenomenon is caused by grain refinement or the formation of amorphous structure in the coating. Grain refinement will make the crystal orientation more dispersed, resulting in a decrease in the diffraction peak intensity of a specific crystal plane; and since the amorphous structure does not have a long-range ordered crystal structure, its XRD spectrum usually shows a broad diffraction peak or no obvious diffraction peak characteristics.

[0109] (3) The cross-sectional TEM image of the CrAlBN protective coating (B-2) prepared in Example 3 is shown in FIG. Figure 2 As shown. Figure 2 In the figure, (a) is a low-magnification image, and (b) is a high-magnification image and selected electron diffraction pattern (SAED pattern). Figure 1 and Figure 2 It can be seen that the diffraction ring radius of the CrAlBN protective coating is between that of fcc-AlN and fcc-CrN, corresponding to the diffraction characteristics of the fcc-(Cr,Al,B)N phase. Based on the comprehensive analysis results of XRD, TEM, and Gibbs free energy (ΔG) thermodynamic calculations, it can be concluded that the boron element is dissolved in the fcc-(Cr,Al)N phase to form an fcc-(Cr,Al,B)N solid solution. The diffraction rings of fcc-CrAlBN in the SAED spectrum are highly consistent with the XRD results. The lattice constant difference between CrAlBN and CrN is extremely small, making it difficult to distinguish by conventional means. The continuous diffraction ring pattern in the SAED spectrum indicates the presence of amorphous structure in the CrAlBN protective coating. Combined with the XRD results, it is further confirmed that the addition of boron significantly promotes grain refinement of the CrAlBN protective coating.

[0110] (4) The SEM images of the cross sections of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are shown in FIG. Figure 3 As shown. Figure 3 In: (a) B-1, (b) B-2, (c) B-3, (d) B-4 and (e) B-5. Figure 3 It can be seen that the thickness of the CrAlBN protective coating with different B contents is 2.84μm, 2.75μm, 2.47μm, 2.13μm and 1.91μm, respectively. The study found that as the CrAl target current decreases, the coating thickness shows a trend of gradual decrease. This is because the target current has an impact on the sputtering process. A lower target current means that the number of atoms sputtered from the target surface during the sputtering process is reduced. During the coating deposition process, the insufficient supply of atoms directly leads to a decrease in the coating growth rate, which in turn reduces the coating thickness. It can be observed from the figure that sufficient diffusion and interaction occur between the atoms of each layer, forming stable chemical bonds or mutual embedding between atoms, thereby promoting close bonding between the layers. In addition, the appropriate amount of B element can play a role in refining the grains and filling the grain boundary gaps during the coating growth process. The small size of the B atoms enables them to enter the lattice gaps or replace some atoms, thereby inhibiting the abnormal growth of the grains, promoting the densification of the columnar crystal structure, and thus improving the flatness of the coating surface.

[0111] When the CrAl target current gradually decreases, that is, the B content increases, the excess B element will change the growth process of the coating. This will increase the base defects of the coating, slightly reduce the density, and cause larger particles and holes to appear. On the one hand, excessive B atoms may aggregate to form larger particles. These particles exist as defects in the coating, affecting the subsequent deposition of the coating during the preparation process. On the other hand, the chemical properties of the B element are relatively active. During the deposition process, it may react with other elements to produce gas or other byproducts, thereby forming holes within the coating. In addition, as the B content increases, the brittleness of the B element gradually becomes apparent. This is because the chemical bonds formed by B atoms with surrounding atoms are different from the original metal nitride chemical bonds. This difference leads to uneven stress distribution within the material, which in turn reduces the strength of the material and has a negative impact on the performance of the coating.

[0112] (5) The cross-sectional roughness of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 is as follows: Figure 4 As shown. Figure 4 It can be seen that when the B content varies in the range of 0 to 6 at.%, the average surface roughness of the coating is 68.7 nm, 81.6 nm, 70.2 nm, 79.3 nm, and 86.3 nm, respectively. Among them, the B-3 sample exhibits the lowest surface roughness, with an Ra value of 70.2 nm. Overall, the coating roughness fluctuation range is relatively small, maintaining in the range of (77.0 ± 8 nm). The doping of B suppresses the coarsening of grains through the pinning effect, thereby reducing surface defects and irregular structures. Although the B content varies from 0 to 6.0 at.%, the roughness fluctuation range of the coating is small (77.0 ± 8.0 nm), which indicates that the effect of B doping on the surface morphology is relatively stable within a certain range.

[0113] (6) The fracture toughness variation curves of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 with the B content are shown in FIG. Figure 5 As shown. Figure 5 It can be seen that as the B content gradually increases, the fracture toughness of the CrAlBN protective coating shows a downward trend. The change of B content has a significant effect on the fracture toughness of the CrAlBN protective coating. The B-2 coating has the best fracture toughness, which is 1.72 MPa·m 1 / 2 This indicates that at this B content, the CrAlBN protective coating has a stronger ability to resist crack propagation, that is, its fracture toughness is significantly improved.

[0114] (7) The internal stress of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 is as follows: Figure 6 As shown. Figure 6As can be seen, when the B content is 1.3 at.%, the residual stress is -480 MPa. All coatings exhibit compressive stress, and their stress values ​​exhibit a significant nonlinear characteristic with B content. At 1.3 at.%, B doping achieves stress balance through the following synergistic mechanisms: first, the competing effects of grain refinement and lattice contraction lead to a dynamic equilibrium between grain boundary stress and lattice stress; second, the amorphous BN phase partially releases phase transition stress through interfacial relaxation; finally, appropriately increasing the target current enhances the ion bombardment effect, promoting atomic-level relaxation and minimizing residual stress. However, when the B content exceeds 1.3 at.%, the residual stress exhibits a monotonically increasing trend, reaching -600 MPa at a B content of 6.0 at.%. This stress enhancement is attributed to two mechanisms: excessive B doping (>1.3 at.%) leads to the accumulation of lattice distortion energy, generating a significant local compressive stress field; and the increased amorphous BN content induces interfacial stress concentration, while the amorphous BN phase forms a continuous network coverage at the grain boundaries, leading to a significant increase in residual stress.

[0115] (8) The friction curves of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 are as follows: Figure 7 As shown in the figure, the friction coefficient variation curve is as follows: Figure 8 As shown. Figure 7 and 8 As can be seen, the COF of coating B-1 is 0.95. The COF decreases significantly with the addition of elemental boron (B). The minimum COF (0.82) is achieved at a B content of 3.0 at.%. Analysis suggests that this change is due to the presence of larger particles on the coating surface at lower B content. During friction, these larger particles interact with each other, increasing the resistance between the surface and the friction ball, leading to a higher coefficient of friction. Furthermore, the addition of B alters the coating's microstructure. Furthermore, B promotes the presence of substances with potential lubricating properties on the coating surface, such as B-containing oxides or nitrides. These lubricating phases possess low shear strength and, during friction, form a lubricating film between the two contacting surfaces, effectively separating them and reducing direct contact friction, thereby significantly lowering the coefficient of friction. When the B content reaches 3.0 at.%, the coating's microstructure reaches a relatively optimized state. At this point, grain refinement is significant, surface smoothness is optimal, and the proportion of lubricating phases is moderate, enabling full lubrication during friction and effectively reducing frictional resistance.

[0116] (9) The polarization curves of the CrAlBN protective coatings prepared in Examples 1 to 3 and Comparative Examples 1 to 2 in 3.5 wt.% NaCl solution are shown in FIG. Figure 9 As shown. Figure 9It can be seen that with the gradual increase of B content, the corrosion potential of the CrAlBN protective coating moves positively to the right, and the corrosion current density gradually decreases. This phenomenon indicates that the corrosion resistance of the coating has been gradually optimized in this process. From B-1 to B~5, as the B content increases, the corrosion potential of the CrAlBN protective coating is -0.389V, -0.325V, -0.224V, -0.253V and -0.311V, respectively. When the B content is set to 3.0at.%, the CrAlBN protective coating exhibits a lower corrosion current density (7.88×10 -8 A.cm -2 ).

[0117] As can be seen from the above technical solution, the CrAlBN protective coating provided by the present invention has excellent friction performance, high hardness, high toughness, and corrosion resistance. This is because the present invention, by doping the CrAlN coating with boron and optimizing the preparation method, controls the boron doping amount to 0.6 to 6.0 at.%, resulting in the CrAlBN protective coating having low roughness, excellent crystallinity, and a high density internal structure, thus achieving excellent friction performance, high hardness, high toughness, and corrosion resistance.

[0118] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A CrAlBN protective coating, characterized in that: The CrAlBN protective coating comprises the following components in atomic percentage: 15.0-18.1 at.% of Cr, 36.0-39.6 at.% of Al, 34.4-34.9 at.% of N, 0.6-6.0 at.% of B, and 6.6-8.5 at.% of O; The roughness of the CrAlBN protective coating is 77.0±8 nm.

2. The CrAlBN protective coating according to claim 1, characterized in that The thickness of the CrAlBN protective coating is 1.9-2.9 μm.

3. The method for preparing the CrAlBN protective coating according to claim 1 or 2, characterized in that: include: Performing a first multi-arc ion plating deposition on the substrate to obtain a CrAlBN protective coating; The target material of the first multi-arc ion plating deposition is a CrAlB metal target material, and the parameters of the first multi-arc ion plating deposition include: a bias voltage of -60 to -80 V; an arc current of 80 to 100 A; and a nitrogen flow rate of 200 to 500 sccm.

4. A composite coating, characterized in that: From bottom to top, it comprises a Cr layer, a CrAl transition layer and a protective layer; the protective layer is the CrAlBN protective coating according to any one of claims 1 to 2 or the CrAlBN protective coating prepared by the preparation method according to claim 3.

5. The composite coating according to claim 4, characterized in that The thickness of the Cr layer is 0.3-0.5 nm.

6. The composite coating according to claim 4, characterized in that The thickness of the CrAl transition layer is 0.5-1 nm.

7. The composite coating according to claim 4, characterized in that The thickness of the protective layer is 1.9 to 2.9 μm.

8. The method for preparing the composite coating according to any one of claims 4 to 7, comprising the following steps: (1) polishing, ultrasonic cleaning, and ion cleaning the substrate in sequence to obtain a pretreated substrate; (2) performing a second multi-arc ion plating deposition on the surface of the pretreated substrate obtained in step (1) to obtain a deposited Cr layer substrate; (3) performing a third multi-arc ion plating deposition on the surface of the deposited Cr layer substrate obtained in step (2) to obtain a deposited transition layer substrate; (4) performing a first multi-arc ion plating deposition on the surface of the deposition transition layer substrate obtained in step (3) to obtain a composite coating.

9. The preparation method according to claim 8, characterized in that The parameters of the second multi-arc ion plating deposition in step (2) include: vacuum degree of 1 to 3×10 -3 Pa; temperature is 350-450°C; Ar gas flow rate is 100-300 sccm; bias voltage is -60--120 V; current is 80-100 A; N2 flow rate is 100-500 sccm; turntable speed is 4-8 r / min; deposition time is 10-30 min; target substrate distance is 240 mm.

10. The preparation method according to claim 8, characterized in that The parameters of the third multi-arc ion plating deposition in step (3) include: vacuum degree of 1 to 3×10 -3 Pa; temperature is 350~450℃; Ar gas flow rate is 100~300sccm; bias voltage is -60~-120V; current is 80~120A; N2 flow rate is 100~500sccm; turntable speed is 4~8r / min; deposition time is 10~30min; target substrate distance is 240mm.

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