HVOF-PVD composite coating and preparation method thereof

Abstract

The invention belongs to the technical field of high-temperature wear-resistant corrosion-resistant composite coatings, and particularly relates to an HVOF-PVD composite coating and a preparation method thereof. The HVOF-PVD composite coating provided by the invention comprises an HVOF layer and a PVD layer, the HVOF layer comprises a NiCr transition layer and a first working layer; the first working layer comprises NiCr and Cr3C2; the PVD layer comprises an AlCr transition layer and a second working layer; and the second working layer comprises AlCrN and TiSiN. By means of the design, the coating shows comprehensive performance superior to that of a single coating under the working conditions of high temperature, corrosion and coupling of the high temperature, the corrosion and the coupling of the high temperature, the corrosion and the coupling, and the comprehensive performance comprises remarkably prolonged wear-resisting life, lower friction coefficient, excellent structural stability and corrosion-wear synergistic resistance.

Description

Technical Field

[0001] This invention belongs to the field of high-temperature wear-resistant and corrosion-resistant composite coating technology, and more specifically relates to an HVOF-PVD composite coating and its preparation method. Background Technology

[0002] NiCr-Cr3C2 cermet coatings prepared by high-velocity vapor deposition (HVOF) technology have attracted much attention in the field of high-temperature protection due to their excellent high-temperature wear resistance and oxidation resistance. The performance of this type of coating is highly dependent on the optimized ratio of the NiCr binder phase to the Cr3C2 hard phase. However, the inherent microscopic defects (such as porosity and oxide inclusions) and relatively rough surface morphology of HVOF coatings pose serious challenges to their application in corrosive environments. These defects become rapid channels for the penetration of corrosive media, and the strong destructive effect of chloride ions on the passivation film leads to a significant decrease in the coating's corrosion resistance.

[0003] Physical vapor deposition (PVD) technology can prepare multilayer thin films with dense structures, smooth surfaces, and excellent chemical stability on the surface of components, which can greatly improve the corrosion resistance of materials. However, the film thickness prepared by PVD technology is limited, and the load-bearing capacity is insufficient. Under harsh wear conditions, it is prone to cracking and peeling, which limits its application under heavy load conditions.

[0004] Therefore, how to construct a new generation of long-life, high-reliability, high-temperature wear-resistant and corrosion-resistant composite coatings has become a key technical challenge that urgently needs to be overcome in the field of surface engineering. Summary of the Invention

[0005] The purpose of this invention is to provide an HVOF-PVD composite coating and its preparation method to solve the problems existing in the prior art.

[0006] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of the present invention is to provide an HVOF-PVD composite coating, comprising: an HVOF layer and a PVD layer; The HVOF layer includes a NiCr transition layer and a first working layer; The first working layer comprises NiCr and Cr3C2; The PVD layer includes an AlCr transition layer and a second working layer; The second working layer comprises alternating AlCrN and TiSiN layers.

[0007] Furthermore, the thickness of the NiCr transition layer is 40-60 μm, preferably 50 μm.

[0008] Furthermore, the thickness of the first working layer is 100-200 μm, preferably 150 μm.

[0009] Furthermore, the mass ratio of NiCr to Cr3C2 in the first working layer is (1:3)-(3:1).

[0010] Furthermore, the thickness of the PVD layer is 2-5 μm.

[0011] Furthermore, the thickness of the AlCr transition layer is 40-60 nm, preferably 50 nm.

[0012] Furthermore, the thickness of the AlCrN layer in the second working layer is 20-50 nm; the thickness of the TiSiN layer is 20-50 nm.

[0013] The preferred thickness ratio of the AlCrN layer to the TiSiN layer is 1:1.

[0014] The second technical solution of the present invention provides a method for preparing the above-mentioned HVOF-PVD composite coating, the steps of which include: A NiCr transition layer and a first working layer are sequentially deposited on the substrate surface by high-velocity flame spraying (HVOF). After surface treatment, an AlCr transition layer is deposited by PVD. Then, an AlCrN layer and a TiSiN layer are sequentially and alternately deposited to obtain the HVOF-PVD composite coating. The first working layer comprises NiCr and Cr3C2 in a mass ratio of (1:3) to (3:1).

[0015] Furthermore, the parameters of the supersonic flame spraying (HVOF) are as follows: powder feed rate of 55-60 g / min, oxygen flow rate of 1800-2000 LPM, propylene flow rate of 5-7 LPM, air flow rate of 24-28 LPM, spraying distance of 300-320 mm, and moving speed of 480-520 mm / s.

[0016] Optionally, the parameters of the supersonic flame spraying (HVOF) are: powder feed rate of 55-60 g / min, oxygen flow rate of 1900 LPM, propylene flow rate of 6 LPM, air flow rate of 26 LPM, spraying distance of 310 mm, and moving speed of 500 mm / s.

[0017] Furthermore, the surface treatment includes polishing and ion cleaning.

[0018] Optionally, the ion cleaning step includes: purging with argon gas after vacuuming, and generating Ar gas through a high negative bias glow discharge. + The surface is bombarded with ions to complete the ion cleaning process.

[0019] Furthermore, the step of depositing the AlCr transition layer using PVD includes: turning on the Cr target and the Al target to deposit the AlCr transition layer, with the following parameters: vacuum degree ≤ 5.0 × 10⁻⁶. -3 Pa; Ar gas pressure: 1.5-3.0 Pa; DC pulse bias voltage: -50 V to -150 V; deposition time: 10-20 min; substrate temperature: 300-450℃.

[0020] Furthermore, the deposition steps of the AlCrN layer include: adjusting the Ar / N2 flow ratio to 1:2, entering the reactive sputtering mode, and starting the AlCr target deposition of the AlCrN layer with the following parameters: working gas pressure 0.25-0.5 Pa; DC pulse bias voltage -50 V to -150 V; substrate temperature 400-500 ℃; deposition time 120-180 min.

[0021] Furthermore, the TiSiN layer deposition step includes: depositing the TiSiN layer on a TiSi target under a nitrogen atmosphere, with parameters: pumped down to <3.0 × 10⁻⁶. -3 Pa, introduce Ar gas to 0.3 Pa; adjust the Ar / N2 flow ratio to 1:1; apply a -100 V DC pulse bias voltage, set the intermediate frequency target power to 5 kW, and maintain the gas pressure between 0.30-0.40 Pa.

[0022] The third technical solution of the present invention provides an application of the above-mentioned HVOF-PVD composite coating in wear-resistant and corrosion-resistant surface engineering.

[0023] The present invention discloses the following technical effects: The HVOF-PVD composite coating involved in this invention achieves synergistic functional enhancement between the PVD surface layer and the HVOF underlayer through a multi-layer composite structure design. The PVD layer primarily provides surface hardness, chemical inertness, and friction-reducing properties. The AlCrN coating, with the introduction of Cr, exhibits superior high-temperature oxidation resistance and a lower coefficient of friction compared to traditional AlTiN coatings. This synergistic mechanism of "interface strengthening-surface protection" makes the chromium-containing PVD coating particularly suitable for harsh conditions involving high temperatures, corrosion, or wear-corrosion coupling. The HVOF underlayer primarily contributes to supporting strength, resistance to plastic deformation, and interfacial stability. This design enables the coating to exhibit superior overall performance compared to a single coating under high-temperature, corrosive, and coupled conditions, including significantly improved wear life, a lower coefficient of friction, excellent structural stability, and synergistic resistance to corrosion and wear. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1The images show the SEM images and particle size distribution diagrams of NiCr, 75NiCr-25Cr3C2, 25NiCr-75Cr3C2, and 50NiCr-50Cr3C2. Among them, (a) is the SEM image of NiCr, (b) is the particle size distribution diagram of NiCr, (c) is the SEM image of 75NiCr-25Cr3C2, (d) is the SEM image of 25NiCr-75Cr3C2, (e) is the particle size distribution diagram of 25NiCr-75Cr3C2, and (f) is the SEM image of 50NiCr-50Cr3C2.

[0025] Figure 2 Nanoindentation curves for different composite coating surfaces.

[0026] Figure 3 In the figure, (a) is a bar chart of wear volume for different HVOF-PVD composite coatings, and (b) is a curve of wear track depth.

[0027] Figure 4 In the figure, (a) shows the friction curves of different HVOF-PVD composite coatings, and (b) shows the wear rate histogram.

[0028] Figure 5 The SEM-EDS images of the wear track morphology of 3B and 3C are shown, where (a) and (b) are for 3B, and (c) and (d) are for 3C.

[0029] Figure 6 The images show the SEM-EDS spectra of wear track morphology in 3D and 4C, where (a) and (b) are 3D, and (c) and (d) are 4C.

[0030] Figure 7 The images are 4D SEM-EDS images of the wear track morphology, where (a) is a low-magnification SEM image of the wear track, and (b) and (c) are magnified images of local wear tracks.

[0031] Figure 8 The nanoindentation load-displacement curves for 4B and 4G are shown.

[0032] Figure 9 The graphs show the friction and wear curves of B, 4B, and 4G in the three sets of experiments.

[0033] Figure 10 The graphs show the wear depth curves for B, 4B, and 4G in the three sets of experiments.

[0034] Figure 11 The cross-section of the coating of the 4B sample after wear was characterized by SEM-EDS, where (a) and (b) are 4B-1, (c) and (d) are 4B-2, and (e) and (f) are 4B-3.

[0035] Figure 12SEM-EDS characterization of the coating morphology of samples B-1 and B-2 after wear, where (a) and (b) are B-1, and (c) and (d) are B-2.

[0036] Figure 13 The SEM-EDS characterization of the coating morphology of sample B-3 after the high-temperature wear-corrosion test is shown in (a) and (b) is the EDS characterization.

[0037] Figure 14 The SEM-EDS characterization of the coating morphology of the 4G sample after friction and wear at room temperature is shown in (a) SEM image, (b) EDS characterization, and (c) magnified view of a local area.

[0038] Figure 15 The SEM-EDS characterization of the coating morphology of the 4G sample after friction and wear at 600℃ is shown in (a) SEM image, (b) EDS characterization, and (c) magnified view of a local area.

[0039] Figure 16 The SEM-EDS characterization of the coating morphology of the 4G sample after high-temperature wear-corrosion test is shown in (a) SEM image, (b) EDS characterization, and (c) magnified view of a local area.

[0040] Figure 17 The SEM-EDS characterization of the coating morphology of sample 4B after friction and wear at room temperature is shown in (a) as a magnified view, (b) as an SEM image, and (c) as an EDS characterization.

[0041] Figure 18 The SEM-EDS characterization of the coating morphology of sample 4B after friction and wear at 600℃ is shown in (a) SEM image, (b) EDS characterization, and (c) magnified view of a local area.

[0042] Figure 19 The SEM-EDS characterization of the coating morphology of sample 4B after high-temperature wear-corrosion test is shown in (a) SEM image, (b) EDS characterization, and (c) magnified view.

[0043] Figure 20 XPS images of the wear surface of sample B after a friction test at 600℃.

[0044] Figure 21 XPS images of the wear track surface of sample B after a high-temperature wear-corrosion test.

[0045] Figure 22 XPS images of the wear surface of sample 4B after a friction test at 600℃.

[0046] Figure 23XPS images of the wear track surface of sample 4B after a high-temperature wear-corrosion test. Detailed Implementation

[0047] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0048] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0049] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0050] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0051] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0052] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0053] In the specific embodiments of the present invention, the NiCr powder involved is Ni80Cr20 powder, which is provided by Chongyi Zhangyuan Tungsten Industry Co., Ltd.; the 25NiCr-75Cr3C2 powder involved is provided by Chongyi Zhangyuan Tungsten Industry Co., Ltd.

[0054] The 75NiCr-25Cr3C2 and 50NiCr-50Cr3C2 involved in this invention are prepared by mixing 25NiCr-75Cr3C2 powder with NiCr powder in a certain proportion.

[0055] Figure 1 The images show the SEM images and particle size distribution diagrams of NiCr, 75NiCr-25Cr3C2, 25NiCr-75Cr3C2, and 50NiCr-50Cr3C2. Among them, (a) is the SEM image of NiCr, (b) is the particle size distribution diagram of NiCr, (c) is the SEM image of 75NiCr-25Cr3C2, (d) is the SEM image of 25NiCr-75Cr3C2, (e) is the particle size distribution diagram of 25NiCr-75Cr3C2, and (f) is the SEM image of 50NiCr-50Cr3C2. As shown in the figure, the NiCr powder is elliptical with a smooth surface and a particle size distribution between 10 and 100 μm, with an average particle size of 37.10 ± 15.19 μm; the 25NiCr-75Cr3C2 powder is spherical with an average particle size of 22.19 ± 6.06 μm and a distribution range of 10-45 μm.

[0056] In the specific embodiment of this invention, the substrate material is 20CrMo steel with dimensions of 200 mm × 200 mm × 12 mm. Before HVOF spraying, the substrate surface is sequentially sanded, cleaned with acetone, and roughened by sandblasting. The main components of 20CrMo steel are shown in Table 1.

[0057] Table 1. Chemical composition (wt.%) of 20CrMo steel as the matrix material In a specific embodiment of the present invention, the raw material powders (NiCr, 75NiCr-25Cr3C2, 25NiCr-75Cr3C2 and 50NiCr-50Cr3C2) used for HVOF spraying are dried at 280°C for 6 hours before spraying to improve fluidity and dispersibility.

[0058] Unless otherwise specified, room temperature and ambient temperature in the specific embodiments of this invention refer to 20-30℃.

[0059] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0060] A specific embodiment of the present invention provides a method for preparing an HVOF-PVD composite coating, the steps of which include: S1. The substrate (20CrMo steel) is rapidly preheated with a supersonic flame (150-200℃), followed by the sequential deposition of a 50 μm thick NiCr transition layer and a 150 μm thick first working layer using HVOF spraying; to suppress thermal deformation of the substrate, compressed air is used to cool the substrate steel plate throughout the process. The parameters for HVOF spraying are: powder feed rate of 55-60 g / min, oxygen flow rate of 1800-2000 LPM, propylene flow rate of 5-7 LPM, air flow rate of 24-28 LPM, spraying distance of 300-320 mm, and moving speed of 480-520 mm / s. After S2 and HVOF spraying are completed, polishing is performed. Then, the substrate is fixed on the rotating frame of the PVD vacuum chamber to ensure uniform coating. The vacuum chamber is evacuated to ≤10. -3 After Pa, Ar gas is introduced, with the pressure set to 0.4-0.6 Pa. The substrate bias is then turned on and set to -780 to -820 V. The substrate is then subjected to glow discharge cleaning for 10 minutes (Ar gas is generated through high negative bias glow discharge). + Ion bombardment of the surface is used for ion cleaning to remove oxides, activate the substrate, and enhance the adhesion between the film and the substrate. S3. After glow discharge cleaning, turn off the Ar gas and turn on the Cr target and Al target to deposit a 50 nm AlCr transition layer (to relieve stress by utilizing its toughness and compatibility). The parameters for depositing the AlCr transition layer are: vacuum degree ≤ 5.0 × 10⁻⁶ -3 Pa; Ar gas pressure: 1.5-3.0 Pa; DC pulse bias voltage: -50 V to -150 V; deposition time: 10-20 min; substrate temperature: 300-450℃; S4. After depositing the AlCr transition layer, high-purity N2 is introduced, and the Ar / N2 flow ratio is adjusted (1:2) to enter the reactive sputtering mode. AlCr target deposition is then started to obtain an AlCrN layer with a thickness of 20-50nm. The parameters for depositing the AlCrN layer were: working gas pressure 0.25-0.5 Pa; DC pulse bias voltage -50 V to -150 V; substrate temperature 400-500 ℃; deposition time 120-180 min. S5. Then, while maintaining the N2 atmosphere, TiSi target deposition was performed to obtain a TiSiN layer with a thickness of 20-50 nm. The parameters for depositing the TiSiN layer were: pumped to <3.0×10⁻⁶. -3 Pa, introduce Ar gas to 0.3 Pa; adjust the Ar / N2 flow ratio to 1:1; apply a -100 V DC pulse bias voltage, set the intermediate frequency target power to 5 kW, and maintain the gas pressure between 0.30-0.40 Pa; The above-mentioned S4 and S5 coatings were cyclically deposited, with approximately 50 cycles, and the total thickness was controlled at approximately 2-5 μm, ultimately yielding the HVOF-PVD composite coating.

[0061] The function of the NiCr transition layer in the HVOF spraying of this invention is as follows: (1) Alleviating the mismatch of thermophysical properties and inhibiting coating failure, the NiCr transition layer, as a performance gradient transition layer, effectively alleviates the huge differences between the coating and the substrate in key properties (such as thermal expansion coefficient, elastic modulus and residual tensile stress), thereby significantly improving the bonding strength and thermal shock resistance of the coating. (2) It provides excellent metallurgical / mechanical bonding. When NiCr alloy and steel substrate (mainly Fe) are subjected to high-temperature particle impact, limited interdiffusion and local metallurgical reaction can occur to form micro-metallurgical bonding, which is stronger and more stable than simple mechanical bonding. The NiCr layer particles sprayed in advance can form a solid, dense and moderately rough bottom layer on the substrate surface, providing an ideal "anchoring" surface for the subsequent deposition of the first working layer, which greatly increases the contact area and mechanical interlocking force between the working layer and the substrate; (3) Chemical and environmental barrier effect: NiCr alloys (especially those with high Cr content, such as Ni80Cr20 used in this invention) have excellent high-temperature oxidation resistance and corrosion resistance. In high-temperature or corrosive environments, they can protect the steel matrix from oxidation and corrosion; prevent elements in the matrix (such as Fe) from diffusing outward to the working layer, and avoid the formation of harmful brittle phases or reduction of its high-temperature performance in the working layer; (4) Support and performance optimization of the first working layer: The NiCr layer has good plasticity and toughness, which can provide solid support for the first working layer (hard NiCr-Cr3C2 ceramic-metal composite layer) above. When the coating is subjected to impact or contact stress, the NiCr layer can undergo plastic deformation, absorb energy, and prevent the first working layer from cracking due to stress concentration.

[0062] (5) Process optimization effect: During the process of spraying NiCr layer, the high-speed and high-temperature NiCr particle flow will preheat and clean the substrate surface, which is conducive to the deposition of subsequent working layers and reduces the porosity and oxide inclusions in the coating.

[0063] Example 1 The preparation steps of the HVOF-PVD composite coating include: S1. The substrate (20CrMo steel) is rapidly preheated with a supersonic flame (between 150-200℃). Then, using Ni80Cr20 powder as raw material, a 50 μm thick NiCr transition layer is deposited by HVOF spraying. Next, using 25NiCr-75Cr3C2 as raw material, a 150 μm thick first working layer (25NiCr-75Cr3C2) is deposited by HVOF spraying. To suppress thermal deformation of the substrate, compressed air is used to cool the substrate steel plate throughout the process. The parameters for HVOF spraying are: powder feed rate of 60 g / min, oxygen flow rate of 1900 LPM, propylene flow rate of 6 LPM, air flow rate of 26 LPM, spraying distance of 3120 mm, and moving speed of 500 mm / s. After S2 and HVOF spraying are completed, polishing is performed. Then, the substrate is fixed on the rotating frame of the PVD vacuum chamber to ensure uniform coating. The vacuum chamber is evacuated to ≤10. -3 After Pa, Ar gas is introduced, and the gas pressure is set to 0.5 Pa. The substrate bias is turned on and set to -800 V. The substrate is then subjected to glow discharge cleaning for 10 min. S3. After glow discharge cleaning, turn off the Ar gas and turn on the Cr target and Al target to deposit a 50 nm AlCr (atomic ratio of 1:1) transition layer. The parameters for depositing the AlCr transition layer are: vacuum degree ≤ 5.0 × 10⁻⁶ -3 Pa; Ar gas pressure: 2.0 Pa; DC pulse bias voltage: -100 V; deposition time: approximately 20 min; substrate temperature: 400 ℃; S4. After depositing the AlCr transition layer, high-purity N2 is introduced, and the Ar / N2 flow ratio is adjusted (1:2) to enter the reactive sputtering mode. AlCr target deposition is then started to obtain an AlCrN layer with a thickness of 50nm. The parameters for depositing the AlCrN layer were: working gas pressure 0.3 Pa; DC pulse bias voltage -100 V; substrate temperature 450 ℃; deposition time 180 min.

[0064] S5. Then, while maintaining the N2 atmosphere, TiSi target deposition was performed to obtain a TiSiN layer with a thickness of 50 nm. The parameters for depositing the TiSiN layer were: pumped to <3.0×10⁻⁶. -3 Pa, introduce Ar gas to 0.3 Pa; adjust the Ar / N2 flow ratio to 1:1; apply a -100 V DC pulse bias voltage, set the intermediate frequency target power to 5 kW, and maintain the gas pressure between 0.30-0.40 Pa; S6. The two coatings in steps S4 and S5 above are deposited in a cycle of about 50 cycles, and the total thickness of the PVD layer is controlled at about 5μm. Finally, the HVOF-PVD composite coating is obtained, which is denoted as 4B.

[0065] Example 2 The only difference from Example 1 is that the first working layer is 75NiCr-25Cr3C2, and the resulting coating is denoted as 4C.

[0066] Example 3 The only difference from Example 1 is that the first working layer is 50NiCr-50Cr3C2, and the resulting coating is denoted as 4D.

[0067] Comparative Example 1 Compared with Example 1, the only difference is that step S4 is to turn on the AlTi target to deposit the AlTiN layer, and the resulting coating is denoted as 3B.

[0068] Comparative Example 2 Compared with Example 2, the only difference is that step S4 is to turn on the AlTi target to deposit the AlTiN layer, and the resulting coating is denoted as 3C.

[0069] Comparative Example 3 Compared with Example 3, the only difference is that step S4 is to turn on the AlTi target to deposit the AlTiN layer, and the resulting coating is denoted as 3D.

[0070] Comparative Example 4 Compared with Comparative Example 1, the only difference is that no first working layer is deposited in step S1, and the resulting coating is denoted as 3A.

[0071] Comparative Example 5 The only difference from Example 1 is that no first working layer is deposited in step S1, and the resulting coating is denoted as 4A.

[0072] Comparative Example 6 Compared with Example 1, the only difference is that only a PVD layer is deposited, that is, the substrate is directly subjected to steps S3-S5 of Example 1, and the resulting coating is denoted as 4G.

[0073] Comparative Example 7 Compared to Comparative Example 1, the only difference is that only a PVD layer is deposited; that is, steps S3-S5 of Comparative Example 1 are directly performed on the substrate. The resulting coating is denoted as 3G. Test case The coating samples prepared in the examples and comparative examples were used to prepare specimens with dimensions of 15 mm × 15 mm × 12 mm using a wire cutting machine for subsequent experimental analysis.

[0074] Friction and wear test: Using an MPT-3G friction and wear testing machine, ball-disc wear tests were conducted on five types of HVOF-PVD composite coating samples (3B, 3C, 3D, 4D, and 4C) according to ASTM G-99 standard.

[0075] The sample dimensions were all 15 mm × 15 mm × 12 mm.

[0076] The experiment was conducted at 350℃, using Al2O3 balls with a diameter of 6 mm as the grinding pair. A load of 15 N was applied, and the balls were continuously worn for 60 minutes at a rotation speed of 200 r / min on a wear track with a diameter of 4 mm. Each group of samples underwent three repeated tests to ensure the reliability and accuracy of the results. After the test, a three-dimensional profilometer was used to measure the wear volume and wear track morphology.

[0077] To systematically evaluate the differences in mechanical properties of different composite coatings, especially key parameters such as elastic modulus and hardness, this invention conducted nanoindentation tests on a series of coatings to obtain the basic characteristics of their microscopic mechanical behavior, laying the foundation for subsequent in-depth analysis of the coatings' performance response under friction, thermal load, and corrosive environments. The experimental results are as follows: Figure 2 As shown.

[0078] Figure 2 The figure shows the nanoindentation curves of different composite coating surfaces. As can be seen from the figure, under the same load, the indentation depths of the five coatings (3B, 4D, 3C, 4C, 3D) are relatively similar (the range is less than 10 nm). Although the 3C coating has the highest hardness (47.06 GPa), the overall differences in hardness and elastic modulus among the coatings are small (hardness range <5 GPa, elastic modulus range <50 GPa), showing highly similar macroscopic mechanical responses. Among them, the 3B coating has the best resistance to plastic deformation.

[0079] To study the tribological properties of different HVOF-PVD composite coatings, it is necessary to quantitatively analyze their key response parameters during the wear process, mainly including the coefficient of friction, wear rate, wear volume, and wear track depth. These parameters can objectively reflect the stress distribution, material loss, surface damage mode, and interfacial lubrication behavior of the coating during the stress process, and are important bases for judging the wear resistance and failure mechanism of the coating.

[0080] Figure 3 In the figure, (a) is a bar chart of wear volume for different HVOF-PVD composite coatings, and (b) is a curve of wear track depth.

[0081] from Figure 3 As can be seen, the 4D sample performed best in both wear depth and wear volume, demonstrating its excellent overall wear resistance. The differences in the ranking of other samples in different indicators reveal the complexity of their wear mechanisms (such as abrasive wear, oxidative wear, etc.). This fully reflects the functional differences in the design of HVOF-PVD composite coatings and provides a clear basis for subsequent optimization.

[0082] Figure 4In the figure, (a) shows the friction curves of different HVOF-PVD composite coatings, and (b) shows the wear rate histogram. As can be seen from the figure, the 4D sample, with its reasonable multilayer structure design, excellent interfacial bonding strength, and effective formation of surface lubricating phase, exhibits the best performance in both friction coefficient (approximately 0.48) and wear rate, demonstrating the best comprehensive tribological performance. Although the 3B and 3C coatings have the lowest friction coefficient (approximately 0.35), the high wear rate of 3C reveals that its wear mechanism may be mainly plastic deformation or abrasive effect, proving that a low friction coefficient is not an absolute guarantee of wear resistance.

[0083] The wear track morphology and surface composition of different HVOF-PVD composite coatings can intuitively reflect key information such as the wear degree, wear track width, oxidation state and dominant wear mechanism of the PVD surface, which is of great importance for revealing the wear mechanism of the composite coating system.

[0084] Figure 5 The figures show the SEM-EDS spectra of the wear track morphology of 3B and 3C, where (a) and (b) represent 3B, and (c) and (d) represent 3C. As can be seen from the figures, the significant difference in wear performance between the 3B and 3C coatings mainly stems from the different ceramic phase contents in their underlying HVOF coatings: the 3B sample (25NiCr-75Cr3C2), due to its high ceramic phase content, exhibits wear track characteristics dominated by abrasive wear with relatively light oxidation; while the 3C sample (75NiCr-25Cr3C2), due to its low underlying hardness and weak resistance to plastic deformation, experiences rapid failure of the PVD layer, resulting in a significantly increased wear track width. The wear mechanism shifts to a combination of oxidative wear and abrasive wear, with increased oxidation.

[0085] Figure 6 The figures show the SEM-EDS spectra of wear track morphology for 3D and 4C samples, where (a) and (b) represent 3D samples, and (c) and (d) represent 4C samples. The figures demonstrate that the composition of the underlying HVOF coating is crucial: the 3D sample, with its moderate ceramic phase content in its 50NiCr-50Cr3C2 underlayer, exhibits a coexistence mechanism of oxidation and abrasive wear during wear, with the plastic deformation capacity of the oxide zone mitigating crack propagation; while the 4C sample, with its low ceramic phase content and insufficient hardness in its 75NiCr-25Cr3C2 underlayer, suffers from severe wear and edge "biting" brittle spalling after rapid PVD layer failure, exhibiting poor fatigue resistance.

[0086] Figure 7The images show the SEM-EDS spectra of the 4D wear track morphology, where (a) is a low-magnification SEM image of the wear track, and (b) and (c) are magnified images of local wear tracks. As can be seen from the figures, although the wear track width of the 4D sample reaches 1200 μm, a continuous oxide film is formed on its surface, and the AlCrN / TiSiN layer remains intact, with the underlying layer not exposed. This indicates that the multilayer structure achieves excellent wear resistance through a synergistic mechanism of "hard protection-oxidative corrosion inhibition": the surface AlCrN / TiSiN resists wear with its high hardness and thermal stability, while the ceramic phase-rich underlying layer provides support and promotes the formation of a chromium / aluminum oxide protective film, ultimately leading to oxidation wear as the dominant process, significantly improving service reliability at high temperatures.

[0087] The ball-disc wear test was performed on three types of samples (B, 4B, and 4G) using an MPT-3G friction and wear testing machine according to ASTM G-99 standard. Sample B was a (25NiCr-75Cr3C2) / NiCr spray coating; sample 4B was the PVD-HVOF composite coating of Example 1; and sample 4G was prepared using the method in Comparative Example 6.

[0088] The sample dimensions were all 15 mm × 15 mm × 12 mm.

[0089] The experiment was divided into three groups: The first group of samples, numbered 4B-1, B-1 and 4G-1, underwent friction and wear testing at room temperature. The second group of samples, numbered 4B-2, B-2 and 4G-2, underwent friction and wear testing at 600°C. The third group of samples, numbered 4B-3, B-3, and 4G-3, had a friction and wear temperature of 600℃. Before and during the wear process, three drops of a saturated solution of NaCl / Na2SO4 / Na2PO4 (with a mass ratio of 6:3:1) were applied to the sample surface.

[0090] All wear tests used Al2O3 balls with a diameter of 6 mm as the grinding pair, applied a load of 15 N, and continuously wore the balls at a rotation speed of 200 r / min on a wear track with a diameter of 4 mm for 100 minutes. Each test was repeated three times to ensure the reliability and accuracy of the results. Wear volume and wear rate results are expressed as mean ± standard deviation. After the test, the wear track depth and morphology were observed using a laser confocal microscope.

[0091] Figure 8 The figures show the nanoindentation load-displacement curves for 4B and 4G coatings. As can be seen from the figures, compared to the 4G coating, the 4B coating exhibits superior resistance to deformation due to its higher hardness and elastic modulus.

[0092] Figure 9The figures show the tribological wear curves of coatings B, 4B, and 4G in three sets of experiments. As can be seen from the figures, in the corrosion-wear coupled environment containing saturated NaCl / Na2SO4 / Na2PO4 solution, although the friction curves of all coatings exhibit initial oscillations due to interference from salt-precipitated abrasive particles and corrosive ions, sample 4B-3, with its excellent structural design and surface chemical state, promotes the formation of a continuous and stable lubricating oxide film, ultimately exhibiting the lowest coefficient of friction (approximately 0.2), demonstrating its superior corrosion-wear synergistic resistance.

[0093] Figure 10 The figures show the wear track depth curves for samples B, 4B, and 4G in the three sets of experiments. As can be seen from the figures, compared to samples 4G and B, sample 4B, with its multi-layered composite structure of a PVD surface layer and an HVOF underlayer working synergistically, exhibits the best and most stable wear resistance under complex conditions including room temperature, high temperature, and salt corrosion. Specifically, the PVD layer in sample 4B provides surface wear resistance and lubrication, while the HVOF underlayer provides high-temperature strength and deformation resistance; the combination of these two effectively suppresses wear under complex conditions.

[0094] Figure 11 The cross-sectional SEM-EDS characterization of the 4B sample coating after wear is shown in the figures. (a) and (b) represent 4B-1, (c) and (d) represent 4B-2, and (e) and (f) represent 4B-3. As can be seen from the figures, the microstructure of the coating cross-section did not change significantly under the three conditions. The interface between the PVD layer and the HVOF underlayer showed good bonding, with no delamination, cracks, or interdiffusion zones, indicating excellent thermal stability and bonding strength. EDS analysis showed that the elements (such as Al, Cr, Ti, Si, and N) within the PVD coating were uniformly distributed without significant segregation or depletion, indicating that the coating maintained chemical stability even under high temperature and corrosive environments. Although localized damage was observed in the PVD coating, its morphological characteristics (such as sharp edges and no traces of plastic deformation) suggest that the damage was more likely caused by mechanical polishing during sample preparation than by actual wear. This damage is not directly related to tribological properties and does not affect the evaluation of the coating's actual service behavior. The 4B coating exhibited excellent structural stability under various environments.

[0095] Figure 12 SEM-EDS characterization of the coating morphology of samples B-1 and B-2 after wear, where (a) and (b) are B-1, and (c) and (d) are B-2.

[0096] Figure 13 The SEM-EDS characterization of the coating morphology of sample B-3 after the high-temperature wear-corrosion test is shown in (a) and (b) is the EDS characterization.

[0097] Figures 12-13It can be seen that the wear of coating B at room temperature is mainly abrasive wear, and the surface is relatively uniform. However, after high-temperature wear, decarburization, oxidation and interfacial stress lead to increased wear, forming honeycomb-like pores. Under the coupled action of wear and corrosion, the coating further degrades, the interfacial bonding is almost lost, and the ceramic phase is almost detached.

[0098] Figure 14 The SEM-EDS images show the morphology of the AlCrN / TiSiN coating after friction and wear at room temperature for the 4G sample. (a) is the SEM image, (b) is the EDS image, and (c) is a magnified view of a local area. As can be seen from the images, the AlCrN / TiSiN coating wear tracks at room temperature exhibit typical abrasive wear characteristics. The parallel furrows and localized spalling on the surface are mainly due to the mechanical cutting of hard abrasive grains and brittle fracture caused by contact stress. The intact elemental distribution and slight oxidation indicate that the wear process is dominated by mechanical damage, and the coating exhibits good chemical stability.

[0099] Figure 15 The SEM-EDS images show the morphology of the coating on the 4G sample after tribological wear at 600℃. (a) is the SEM image, (b) is the EDS image, and (c) is a magnified view of a local area. As can be seen from the images, the wear track width significantly increased to approximately 700 μm, and the surface oxide film was extensively damaged. Simultaneously, the oxygen and iron content increased sharply, while the characteristic elements of the coating almost disappeared. This indicates that the AlCrN / TiSiN coating has completely worn away and failed, with the surface layer mainly composed of iron oxides, thus losing its protective function.

[0100] Figure 16 The SEM-EDS images show the morphology of the coating on the 4G sample after a high-temperature wear-corrosion test. (a) is the SEM image, (b) is the EDS image, and (c) is a magnified view of a local area. As can be seen from the images, the wear track width further increased to approximately 750 μm, indicating extensive damage to the surface oxide film. The extremely high oxygen and iron content, coupled with the near disappearance of characteristic elements in the coating, indicates that the AlCrN / TiSiN coating has completely worn away and failed, with the surface primarily consisting of iron oxides, thus completely losing its protective function.

[0101] Figures 14-16 In summary, a single AlCrN / TiSiN coating exhibits wear resistance at room temperature, but lacks high-temperature thermal stability and oxidation resistance, making it difficult to withstand the damage caused by complex working conditions such as high-temperature wear-oxidation and wear-oxidation-corrosion coupling.

[0102] Figure 17The SEM-EDS characterization of the coating morphology of sample 4B after friction and wear at room temperature is shown in Figure 4B. (a) is a magnified view, (b) is the SEM image, and (c) is the EDS characterization. As can be seen from the figures, the friction and wear tracks at room temperature are shallow and the surface is smooth, without cracks, peeling, or other damage. This indicates that the AlCrN / TiSiN coating remains intact during the friction process, exhibiting only slight oxidation and demonstrating excellent structural integrity, wear resistance, and chemical stability.

[0103] Figure 18 The SEM-EDS images show the morphology of the AlCrN / TiSiN coating after friction and wear at 600℃ for sample 4B. (a) is the SEM image, (b) is the EDS image, and (c) is a magnified view of a portion of the coating. As can be seen from the images, the wear track width of the AlCrN / TiSiN coating is approximately 320 μm at high temperature. A continuous and dense black oxide film forms on the surface without damage. Simultaneously, the oxygen content is moderately increased while the distribution of characteristic elements in the coating remains stable, indicating excellent high-temperature stability and wear resistance.

[0104] Figure 19 The SEM-EDS images show the morphology of the coating on sample 4B after a high-temperature wear-corrosion test. (a) is the SEM image, (b) is the EDS image, and (c) is a magnified view of a local area. Under the harsh conditions of high-temperature salt corrosion, a continuous and dense oxide film formed on the surface of the AlCrN / TiSiN coating. Although the wear track width increased to approximately 600 μm due to interfacial stress and media softening, its overall structure remained intact and its elemental distribution remained stable, exhibiting excellent high-temperature stability and corrosion resistance.

[0105] Figure 20 The image shows the XPS spectra of the wear surface of sample B after a friction test at 600℃. As can be seen from the figure, XPS analysis indicates that a stable oxide passivation film mainly composed of Cr2O3 and NiCr2O4 was formed on the worn surface, accompanied by relatively sufficient nickel oxidation (Ni...). 2+ / Ni 3+ And organic matter adsorption or carbonaceous residue, but a small amount of Cr is still present in some areas. 6+ The presence of Cr and other metals reflects a complex chemical state dominated by oxidation reactions, accompanied by incomplete local oxidation or exposure of fresh surfaces.

[0106] Figure 21 The figure shows the XPS spectra of the wear track surface of sample B after a high-temperature wear-corrosion test. As can be seen from the figure, compared with the unsalted environment at 600℃, the salt-corroded medium promotes the formation of the spinel-type NiCr2O4 phase with better thermal stability on the wear surface and significantly accelerates the oxidation process of carbon, revealing the profound influence of the corrosive medium on the tribochemical process.

[0107] Figure 22The figure shows the XPS spectra of the wear track surface of sample 4B after a friction test at 600℃. As can be seen from the figure, XPS analysis indicates that high-temperature friction caused the formation of a stable composite oxide film mainly composed of TiO2, Al2O3, Cr2O3, and NiCr2O4 on the coating surface. Simultaneously, multiple tribochemical reactions occurred, including the decomposition of carbides to release graphite carbon, the decomposition of nitrides, and the formation of silicates. The final chemical state is the result of the combined effects of mechanical wear and thermo-chemical coupling reactions.

[0108] Figure 23 The image shows the XPS spectra of the wear track surface of sample 4B after a high-temperature wear-corrosion test. As can be seen from the figure, compared to the unsalted environment at 600℃, the salt-corroded medium, by altering the local electrochemical environment and introducing a synergistic wear-corrosion effect, promotes the formation of high-valence Ni on the coating surface. 3+ Oxides, while inhibiting Cr 6+ The formation of this chemical state distribution profoundly affects the hardness, toughness, and protective performance of the oxide film.

[0109] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0110] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An HVOF-PVD composite coating, characterized in that, include: HVOF layer and PVD layer; The HVOF layer includes a NiCr transition layer and a first working layer; The first working layer comprises NiCr and Cr3C2; The PVD layer includes an AlCr transition layer and a second working layer; The second working layer comprises alternating AlCrN and TiSiN layers.

2. The HVOF-PVD composite coating as described in claim 1, characterized in that, The thickness of the NiCr transition layer is 40-60 μm; And / or, the thickness of the first working layer is 100-200 μm.

3. The HVOF-PVD composite coating as described in claim 1, characterized in that, The mass ratio of NiCr to Cr3C2 in the first working layer is (1:3)-(3:1).

4. The HVOF-PVD composite coating as described in claim 1, characterized in that, The thickness of the PVD layer is 2-5 μm.

5. The HVOF-PVD composite coating as described in claim 1, characterized in that, The thickness of the AlCr transition layer is 40-60 nm.

6. The HVOF-PVD composite coating as described in claim 1, characterized in that, The thickness of the AlCrN layer in the second working layer is 20-50 nm; the thickness of the TiSiN layer is 20-50 nm.

7. A method for preparing an HVOF-PVD composite coating according to any one of claims 1-6, characterized in that the step... include: A NiCr transition layer and a first working layer are sequentially deposited on the substrate surface by supersonic flame spraying. After surface treatment, an AlCr transition layer is deposited by PVD. Then, an AlCrN layer and a TiSiN layer are sequentially and alternately deposited to obtain the HVOF-PVD composite coating. The first working layer comprises NiCr and Cr3C2 in a mass ratio of (1:3) to (3:1).

8. The preparation method according to claim 7, characterized in that, The parameters for the supersonic flame spraying are: powder feed rate of 55-60 g / min, oxygen flow rate of 1800-2000 LPM, propylene flow rate of 5-7 LPM, air flow rate of 24-28 LPM, spraying distance of 300-320 mm, and moving speed of 480-520 mm / s. And / or, the surface treatment includes polishing and ion cleaning.

9. The preparation method according to claim 7, characterized in that, The step of depositing the AlCr transition layer using PVD includes: turning on the Cr target and the Al target to deposit the AlCr transition layer, with the following parameters: vacuum degree ≤ 5.0 × 10⁻⁶. -3 Pa; Ar gas pressure: 1.5-3.0 Pa; DC pulse bias voltage: -50 V to -150 V; deposition time: 10-20 min; substrate temperature: 300-450℃; And / or, the AlCrN layer deposition step includes: adjusting the Ar / N2 flow ratio to 1:2, entering reactive sputtering mode, and starting AlCr target deposition of the AlCrN layer with the following parameters: working gas pressure 0.25-0.5 Pa; DC pulse bias -50 V to -150 V; substrate temperature 400-500 ℃; deposition time 120-180 min; And / or, the TiSiN layer deposition step includes: depositing a TiSiN layer on a TiSi target under a nitrogen atmosphere, with parameters such as: pumping down to <3.0 × 10⁻⁶. -3 Pa, introduce Ar gas to 0.3 Pa; adjust the Ar / N2 flow ratio to 1:1; apply a -100 V DC pulse bias voltage, set the intermediate frequency target power to 5 kW, and maintain the gas pressure between 0.30-0.40 Pa.

10. The application of the HVOF-PVD composite coating according to any one of claims 1-6 in wear-resistant and corrosion-resistant surface engineering.

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