Wear-resistant coating and preparation method thereof

Abstract

The invention relates to the field of wear-resistant coatings, in particular to a wear-resistant coating and a preparation method thereof. And cleaning and removing an oxide layer on the surface of the substrate to obtain a base surface. And a transition layer is formed on the surface of the basal plane by using a stellite 6 welding material through multiple plasma arc surfacing. And grinding and cleaning the surface of the transition layer to form a bonding surface. A wear-resistant layer is formed on the surface of the bonding surface through chemical vapor deposition, and the component of the wear-resistant layer is titanium nitride. The wear-resistant layer and the base body are connected through the transition layer, so that interface shear stress generated in the high-temperature friction process is gradually released in the transition layer in the thickness direction, and the risk that the wear-resistant layer is broken and falls off is reduced. The transition layer is formed through multiple plasma arc surfacing, so that the transition layer has high toughness and impact resistance, the binding force between the transition layer and the wear-resistant layer is improved, and the service life of the whole wear-resistant coating is prolonged.

Description

Technical Field

[0001] This invention relates to the field of wear-resistant coatings, and particularly to a wear-resistant coating and its preparation method. Background Technology

[0002] In some components of fluid machinery, such as fluid valves, the surfaces that come into contact with the fluid, such as the sealing and guiding surfaces of fluid valves, are often subjected to the combined effects of high temperature, high pressure, erosion by solid particles, and corrosive media. This can easily lead to surface wear, pitting, peeling, and interface failure, which is detrimental to the long-term stable operation of the relevant components.

[0003] To improve the service life of components, wear-resistant coatings are often formed on their surfaces. Currently, titanium nitride (TiN) is the preferred material for wear-resistant coatings due to its extremely high hardness and wear resistance, high temperature resistance, low coefficient of friction and lubricity, strong adhesion and substrate compatibility, and excellent corrosion resistance. However, TiN has a lower coefficient of thermal expansion than the steel substrate, making it prone to coating cracking due to this mismatch in thermal expansion coefficients when heated. During high-temperature wear, localized frictional heat can cause the coating surface temperature to be much higher than the substrate, creating a temperature gradient and further exacerbating thermal stress. Especially when the coating surface temperature exceeds 500℃, TiN is oxidized into brittle titanium dioxide (TiO2). TiO2 has a larger volume than TiN of the same molar amount, and its crystal structure differs significantly from TiN. This results in weaker bonding between the oxide layer and both TiN and the substrate, making it prone to cracking and detachment, which is detrimental to the long-term stable operation of components. Summary of the Invention

[0004] The purpose of this invention is to provide a wear-resistant coating that is not easily detached and a method for preparing the same.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a wear-resistant coating, comprising: Clean and remove the oxide layer from the substrate surface to obtain the base surface; A transition layer is formed on the surface of the base surface by multiple plasma arc welding with Stellite 6 welding material; The surface of the transition layer is ground and cleaned to form a bonding surface; A wear-resistant layer is formed on the surface of the bonding surface by chemical vapor deposition, and the wear-resistant layer is composed of titanium nitride.

[0006] Optionally, each weld overlay forms an alloy film with a thickness of any value between 1.5 mm and 3 mm, and the total thickness of the transition layer is any value between 1.6 cm and 2.4 cm.

[0007] Optionally, the welding current is any value between 120A and 180A, the arc voltage is any value between 22V and 28V, the welding speed is any value between 80mm / min and 150mm / min, and the welding is carried out under the protection of an inert gas.

[0008] Optionally, the roughness of the mating surface is any value between 0.2 μm and 0.4 μm.

[0009] Optionally, the chemical vapor deposition is performed by arc ion plating or magnetron sputtering.

[0010] Optionally, the bonding surface is ultrasonically cleaned and bombarded with argon ions before the chemical vapor deposition. The nitrogen partial pressure in the chemical vapor deposition is any value between 0.1 Pa and 0.4 Pa, the substrate bias voltage is any value between -40 V and -120 V, and the deposition temperature is any value between 300 °C and 450 °C.

[0011] Optionally, when depositing the wear-resistant layer by the arc ion plating, the deposition chamber pressure is any value between 0.15 Pa and 0.5 Pa, and the titanium target current is any value between 50 A and 65 A.

[0012] Optionally, the thickness of the wear-resistant layer is any value between 2μm and 10μm.

[0013] The present invention also provides a wear-resistant coating, which is prepared by the above-described method for preparing a wear-resistant coating.

[0014] Optionally, the substrate is austenitic stainless steel F347, and the internal structure of the transition layer consists of equiaxed crystals, columnar crystals, and fine equiaxed crystals.

[0015] The beneficial effects of this invention are as follows: The transition layer, in terms of mechanical properties, is located in the intermediate range between the matrix and TiN. By constructing a continuous hardness and elastic modulus gradient, the interfacial shear stress generated during high-temperature friction is no longer concentrated on the extremely thin TiN / matrix interface, but is gradually released along the thickness direction within the transition layer. This reduces the stress peak at the interface, forming a buffer between the matrix and the wear-resistant layer. This prevents stress concentration at the interfacial interface caused by TiN oxidation at high temperatures, which reduces the interfacial bonding ability. Consequently, it inhibits the fragmentation and detachment of brittle substances formed by oxidation under frictional shear, thereby suppressing the initiation and propagation of interfacial cracks. This prevents large-scale peeling of the wear-resistant layer due to interfacial cracks, drastic fluctuations in the friction coefficient, and rapid failure of wear resistance. On the other hand, the transition layer is formed by multiple plasma arc welding processes, which facilitates increasing the thickness of the transition layer. Furthermore, plasma arc welding has a relatively large molten pool volume and more stable heat input, allowing the molten metal inside the pool to have more sufficient flow and degassing time under a protective atmosphere, which is beneficial for the floating and removal of inclusions. Simultaneously, continuous high-purity argon protection creates a stable low-oxygen environment throughout the molten pool and its surroundings, significantly inhibiting oxygen dissolution and oxide formation. When preparing a Stellite 6 alloy transition layer on the substrate surface using multiple plasma arc welding techniques, a composite crystal structure composed of equiaxed crystals, columnar crystals, and fine equiaxed crystals is formed internally. The transition layer microstructure consists of equiaxed crystals at the bottom, columnar crystals in the middle, and fine equiaxed crystals at the top. Equiaxed crystals are predominantly distributed near the interface between the transition layer and the substrate. This is due to the diffusion of elements from the substrate into the transition layer, creating a localized mixing region that facilitates the formation of equiaxed crystals. This region exhibits uniform and stable properties, lacking directionality, thus providing buffering capacity in both the transverse and longitudinal directions. This helps alleviate stress concentration at the interface and results in high bonding strength with the substrate. Columnar crystals are predominantly distributed in the middle layer of the transition layer. These columnar crystals are relatively large, with small grain boundary areas, consistent orientation, and exhibit significant directionality—good in the longitudinal direction and poor in the transverse direction—which helps improve the buffering capacity of the transition layer in the thickness direction. The transition layer, near its interface with the wear-resistant layer, is primarily composed of fine equiaxed crystals. This is because the surface area has numerous heat dissipation channels, resulting in rapid cooling and increased supercooling. The thinness of the fine equiaxed crystal region has little impact on the performance of the transition layer, but it helps improve the bonding strength between the transition layer and the wear-resistant layer. The transition layer contains a higher proportion of columnar crystals and a moderate proportion of equiaxed crystals. The fine equiaxed crystals are locally aggregated, exhibiting complex crystal forms and uneven distribution. This gives the transition layer both high toughness and impact resistance, making it suitable for sliding friction or dynamic load scenarios, and enabling a high level of film-substrate bonding strength between the wear-resistant layer and the transition layer.This high bonding strength ensures that even under high-temperature friction and oxidation conditions, the interface can withstand repeated shear loads without overall detachment, even if local surface oxidation or slight breakage occurs. This fundamentally avoids the main failure mode of large-scale peeling, and changes the wear behavior from being dominated by interface peeling to being dominated by abrasive wear and slight oxidation wear. During the friction process, the structural integrity is maintained, and the coefficient of friction remains within a relatively stable range, thus giving the wear-resistant coating a longer service life.

[0016] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0017] Figure 1 This is a flowchart of the method for preparing the wear-resistant coating as shown in Embodiment 1 of the present invention; Figure 2 This is a scanning electron microscope image of the wear-resistant coating shown in Embodiment 1 of the present invention; Figure 3 This is an analysis diagram of the microhardness test results of multiple samples as shown in Embodiment 1 of the present invention; Figure 4 This is a diagram showing the bonding strength analysis between the transition layer and the wear-resistant layer of the wear-resistant coating as shown in Embodiment 1 of the present invention. Figure 5 These are high-temperature friction and wear performance analysis diagrams of multiple samples as shown in Embodiment 1 of the present invention; Figure 6 The above are the potentiodynamic polarization curves of multiple samples shown in Embodiment 1 of the present invention; Figure 7 This is a diagram showing the bonding strength analysis of the transition layer and the wear-resistant layer of the wear-resistant coating shown in Comparative Example 1 of the present invention. Detailed Implementation

[0018] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0022] This invention application protects a method for preparing a wear-resistant coating, comprising: S1. Clean and remove the oxide layer on the substrate surface to obtain the substrate surface.

[0023] S2. A transition layer is formed on the base surface by multiple plasma arc welding with Stellite 6 welding material.

[0024] S3. Grind and clean the surface of the transition layer to form a bonding surface.

[0025] S4. A wear-resistant layer is formed on the bonding surface by chemical vapor deposition. The wear-resistant layer is composed of titanium nitride.

[0026] The transition layer, mechanically positioned between the matrix and TiN, creates a continuous gradient of hardness and elastic modulus. This prevents the interfacial shear stress generated during high-temperature friction from concentrating on the extremely thin TiN / matrix interface. Instead, it gradually releases stress along the thickness of the transition layer, reducing the stress peak at the interface and creating a buffer between the matrix and the wear-resistant layer. This prevents stress concentration at the interfacial interface caused by TiN oxidation at high temperatures, which reduces interfacial bonding and inhibits the fragmentation and detachment of brittle materials formed by oxidation under frictional shear. This, in turn, suppresses the initiation and propagation of interfacial cracks, preventing large-scale peeling of the wear-resistant layer, drastic fluctuations in the friction coefficient, and rapid failure of wear resistance due to interfacial cracks. Furthermore, the transition layer is formed through multiple plasma arc welding processes, facilitating increased thickness. Plasma arc welding also provides a relatively large molten pool volume and more stable heat input, allowing for more sufficient flow and degassing time of the molten metal within the protective atmosphere, thus promoting the flotation and removal of inclusions. Simultaneously, continuous high-purity argon protection creates a stable low-oxygen environment throughout the molten pool and its surroundings, significantly inhibiting oxygen dissolution and oxide formation. When preparing a Stellite 6 alloy transition layer on the substrate surface using multiple plasma arc welding techniques, a composite crystal structure composed of equiaxed crystals, columnar crystals, and fine equiaxed crystals is formed internally. The transition layer microstructure consists of equiaxed crystals at the bottom, columnar crystals in the middle, and fine equiaxed crystals at the top. Equiaxed crystals are predominantly distributed near the interface between the transition layer and the substrate. This is due to the diffusion of elements from the substrate into the transition layer, creating a localized mixing region that facilitates the formation of equiaxed crystals. This region exhibits uniform and stable properties, lacking directionality, thus providing buffering capacity in both the transverse and longitudinal directions. This helps alleviate stress concentration at the interface and results in high bonding strength with the substrate. Columnar crystals are predominantly distributed in the middle layer of the transition layer. These columnar crystals are relatively large, with small grain boundary areas, consistent orientation, and exhibit significant directionality—good in the longitudinal direction and poor in the transverse direction—which helps improve the buffering capacity of the transition layer in the thickness direction. The transition layer, near its interface with the wear-resistant layer, is primarily composed of fine equiaxed crystals. This is because the surface area has numerous heat dissipation channels, resulting in rapid cooling and increased supercooling. The thinness of the fine equiaxed crystal region has little impact on the performance of the transition layer, but it helps improve the bonding strength between the transition layer and the wear-resistant layer. The transition layer contains a higher proportion of columnar crystals and a moderate proportion of equiaxed crystals. The fine equiaxed crystals are locally aggregated, exhibiting complex crystal forms and uneven distribution. This gives the transition layer both high toughness and impact resistance, making it suitable for sliding friction or dynamic load scenarios, and enabling a high level of film-substrate bonding strength between the wear-resistant layer and the transition layer.This high bonding strength ensures that even under high-temperature friction and oxidation conditions, the interface can withstand repeated shear loads without overall detachment, even if local surface oxidation or slight breakage occurs. This fundamentally avoids the main failure mode of large-scale peeling, and changes the wear behavior from being dominated by interface peeling to being dominated by abrasive wear and slight oxidation wear. During the friction process, the structural integrity is maintained, and the coefficient of friction remains within a relatively stable range, thus giving the wear-resistant coating a longer service life.

[0027] In some embodiments, each weld build-up forms an alloy film with a thickness of any value between 1.5 mm and 3 mm. The thickness of the alloy film can be, for example, any value among 1.5 mm, 2 mm, 2.5 mm, and 3 mm, and the total thickness of the transition layer is any value between 1.6 cm and 2.4 cm, for example, any value among 1.6 cm, 1.8 cm, 2 cm, 2.2 cm, and 2.4 cm. Constraining the thickness of the alloy film formed in each weld build-up helps to regulate the internal crystal structure of the transition layer through multi-layer thermal cycling. Multiple weld build-ups forming a thicker transition layer help improve the ability of the transition layer to release interfacial shear stress in the thickness direction and also help to improve the bonding strength between the wear-resistant layer and the substrate, thereby suppressing the peeling of the wear-resistant layer.

[0028] In some embodiments, the welding current is any value from 120A to 180A, for example, any value from 120A, 150A, and 180A; the arc voltage is any value from 22V to 28V, for example, any value from 22V, 24V, 26V, and 28V; the welding speed is any value from 80mm / min to 150mm / min, for example, any value from 80mm / min, 90mm / min, 120mm / min, and 150mm / min; and the welding is performed under the protection of an inert gas. By constraining the reaction conditions of the welding, it is helpful to control the quality of the transition layer, thereby improving the buffering capacity of the transition layer.

[0029] In some embodiments, the roughness of the bonding surface is any value from 0.2 μm to 0.4 μm, for example, any value from 0.2 μm, 0.3 μm and 0.4 μm, which helps to improve the bonding force between the transition layer and the wear-resistant layer.

[0030] In some embodiments, chemical vapor deposition is performed as arc ion plating or magnetron sputtering. Arc ion plating evaporates and highly ionizes the target material through cathode arc discharge, forming a high-density plasma. This high-energy ion bombardment of the substrate eliminates columnar crystal growth, contributing to a dense and strongly bonded coating. Magnetron sputtering confines electron movement with a magnetic field, improving sputtering efficiency and reducing large particle formation, thus contributing to the preparation of thin films with smooth surfaces. Preparing wear-resistant layers using arc ion plating or magnetron sputtering facilitates rapid film formation and improves the adhesion between the wear-resistant layer and the transition layer.

[0031] In some embodiments, the bonding surface is ultrasonically cleaned and bombarded with argon ions before chemical vapor deposition. During chemical vapor deposition, the nitrogen partial pressure is any value between 0.1 Pa and 0.4 Pa, for example, any value among 0.1 Pa, 0.2 Pa, 0.3 Pa, and 0.4 Pa; the substrate bias voltage is any value between -40 V and -120 V, for example, any value among -40 V, -80 V, and -120 V; and the deposition temperature is any value between 300 °C and 450 °C, for example, any value among 300 °C, 350 °C, 400 °C, and 450 °C. Constraining the parameters during the preparation of the wear-resistant layer helps improve the quality of the wear-resistant layer and its bonding ability with the transition layer, thereby enabling the wear-resistant coating to achieve a longer service life. Argon ion bombardment helps improve interfacial adhesion.

[0032] In some embodiments, when the wear-resistant layer is deposited by arc ion plating, the deposition chamber pressure is any value from 0.15 Pa to 0.5 Pa, for example, any value from 0.15 Pa, 0.3 Pa, 0.4 Pa, and 0.5 Pa, and the titanium target current is any value from 50 A to 65 A, for example, any value from 50 A, 55 A, 60 A, and 65 A.

[0033] In some embodiments, the thickness of the wear-resistant layer is any value from 2μm to 10μm, for example, any value among 2μm, 4μm, 6μm, 8μm, and 10μm. The thickness of the wear-resistant layer is constrained to maintain high wear resistance and a low coefficient of friction while avoiding the risk of residual stress accumulation and peeling due to excessive thickness.

[0034] The present invention also provides a wear-resistant coating, which is prepared by the above-described method for preparing a wear-resistant coating.

[0035] The wear-resistant coating prepared by the above method is not easy to peel off and has good wear and corrosion resistance, which can effectively improve the service life of the substrate and has high practicality.

[0036] In some embodiments, the substrate is austenitic stainless steel F347, and the internal structure of the transition layer consists of equiaxed crystals, columnar crystals, and fine equiaxed crystals. Austenitic stainless steel F347 has outstanding high-temperature resistance and corrosion resistance, and can maintain its oxidation resistance and mechanical properties for a long time in air below 800°C. It is easy to process and weld, and has high practicality in the field of workpiece preparation.

[0037] Please refer to the following examples for details.

[0038] Example 1: Please see Figure 1 The method for preparing the wear-resistant coating shown in a preferred embodiment of this application includes: S1. Clean and remove the oxide layer on the substrate surface to obtain the substrate surface.

[0039] S2. A transition layer is formed on the base surface by multiple plasma arc welding with Stellite 6 welding material.

[0040] S3. Grind and clean the surface of the transition layer to form a bonding surface.

[0041] S4. A wear-resistant layer is formed on the bonding surface by chemical vapor deposition. The wear-resistant layer is composed of titanium nitride.

[0042] In step S1, ASTM A182 F347 austenitic stainless steel is selected as the base material. The oxide scale is removed by grinding with a grinding wheel, and the surface is ground step by step with 240-800 grit sandpaper to obtain a base surface with a surface roughness of less than 10μm and no defects such as pits or cracks.

[0043] In step S2, the substrate is placed in a plasma arc welding equipment (DL-PTA-300 CNC plasma welding system, Kennametal Stellite Metals Ltd.), and the substrate surface is welded using Stellite 6 alloy powder. During welding, the current is set to 150A, the arc voltage is maintained at 24V, the welding speed is controlled at 120mm / min, and high-purity argon gas at a flow rate of 12L / min is used as the shielding gas to ensure a stable welding process and reduce oxide formation. Each weld layer forms an alloy film with a thickness of approximately 2.0mm, and after multiple weld layers, a transition layer with a total thickness of approximately 2cm is formed.

[0044] In step S3, the naturally cooled transition layer is finely ground using a grinding wheel, and polishing residue is removed by ultrasonic cleaning to form a bonding surface with a roughness of approximately 0.3 μm, suitable for subsequent deposition of the wear-resistant layer. Please refer to [link to relevant documentation]. Figure 2 Scanning electron microscopy (SEM) revealed that the transition layer consists of equiaxed crystals, columnar crystals, and fine equiaxed crystals. The equiaxed crystals are mainly distributed in the region adjacent to the substrate, i.e., the interlayer interface between the substrate and the transition layer. The columnar crystals are oriented perpendicular to the substrate in the central region of the transition layer, while the fine equiaxed crystals are concentrated in the region adjacent to the bonding surface, i.e., the interlayer interface between the transition layer and the wear-resistant layer. The overall forming quality of the transition layer is good, with no macroscopic cracks or pores, and a continuous metallurgical bonding interface is formed between it and the substrate.

[0045] The obtained transition layer was subjected to three-dimensional tomographic scanning using a high-resolution micron-level industrial computed tomography (CT) system (model EasyTom 150) purchased from RX Solutions, France. The scanning voltage was 150 kV, the current was 66 μA, and the voxel size was controlled at 10 μm. During the scanning process, no distinguishable pores, cracks, or inclusions were found throughout the entire volume of the wear-resistant coating. The layer showed uniform density and continuous interface structure, indicating that the transition layer can achieve a high-density internal structure under the process conditions of this invention, providing a reliable substrate support for the subsequent deposition of TiN thin films. The oxygen content of the transition layer was determined using an oxygen, nitrogen, and hydrogen analyzer (model EMGA-930) purchased from Horiba Group, Japan. The average value of the two measurements was 0.00325 wt.%, indicating that the oxygen content of the transition layer was extremely low and no brittle defects caused by oxide inclusions were observed. The dense characteristics of industrial CT and the low oxygen level obtained from oxygen content testing corroborate each other, proving that the plasma arc welding method used in this invention can effectively suppress oxidation reaction and porosity formation, thereby ensuring the metallurgical quality and mechanical reliability of the transition layer, enabling it to serve as a stable intermediate layer for TiN coating deposition and provide sufficient structural support in subsequent friction, wear and corrosion environments.

[0046] In step S4, the composite material of the ground and cleaned substrate and Stellite 6 is placed in a chemical vapor deposition (CemeCon CC800 sputtering coating system, Ulvac Co., Ltd., Japan) for TiN deposition via arc ion plating to obtain a wear-resistant layer. The bonding surface is first cleaned and activated by argon ion bombardment to improve the adhesion between the wear-resistant layer and the transition layer. The deposition temperature is set to 400°C, the nitrogen to hydrogen ratio in the reaction gas is maintained at 4:1, the pressure in the deposition chamber is stabilized at approximately 0.25 Pa, the titanium target current is adjusted to 60 A, and the substrate bias voltage is controlled at -80 V. After deposition lasts for approximately 90 minutes, a wear-resistant layer with a thickness of approximately 5 μm is formed. Its surface is uniformly golden yellow, and no microcracks or large-area particle defects are observed.

[0047] After the composite coating is prepared, the wear-resistant layer can be further treated with post-processing techniques such as polishing or micro-arc oxidation to improve surface integrity and tribological behavior, thereby enabling the wear-resistant coating to achieve lower frictional resistance. In this embodiment, no post-processing is performed to facilitate the evaluation of the wear-resistant coating's performance.

[0048] The matrix is ​​named F347, the composite material of the matrix and the transition layer is named Stl6, and the composite material of the matrix and the wear-resistant coating is named Stl6 / TiN.

[0049] Microhardness tests were conducted on F347, Stl6, and Stl6 / TiN using an MH-5 Vickers microhardness tester purchased from Maige Instruments (Suzhou) Co., Ltd. A load of 0.05 N was applied for all tests, and the load was maintained for 15 seconds. The test results are available in the [link to test results]. Figure 3 It can be seen that the hardness of the matrix is ​​250.87 HV, while the hardness increases to about 516.57 HV after the transition layer is formed on its surface. After the wear-resistant layer is formed, the hardness reaches about 2163.53 HV, which is nearly nine times higher than that of the matrix and about four times higher than that of the composite material of matrix and transition layer. This indicates that the wear-resistant layer has significantly enhanced resistance to indentation.

[0050] The coating adhesion strength was tested using a nano-scratch analyzer (model SMT-5000) purchased from Rtec Instruments, USA. The coating failure point was determined by gradually increasing the load and simultaneously recording changes in acoustic emission signals and frictional force. Please refer to [link to relevant documentation]. Figure 4 It can be seen that the critical load (LC1) of TiN on the Stellite 6 surface reached about 73.78 N, which is much greater than the conventional 20 N to 30 N. No obvious peeling was observed at the interface before the coating failed, indicating that the interfacial bonding strength prepared by the method of the present invention is at a high level.

[0051] The tribological properties of F347, Stl6, and Stl6 / TiN were evaluated using a high-temperature tribological testing machine (model MFT-5000) purchased from Rtec Instruments, USA. The coefficient of friction of the wear-resistant coating surface was tested over time at room temperature, 250°C, and 500°C under dry sliding conditions. The test results are available in [link to test results]. Figure 5 It can be seen that the friction coefficient of the F347 surface fluctuates in the range of 0.5 to 1.2 at room temperature, showing obvious adhesive wear. In contrast, the wear-resistant coating maintains a stable surface friction coefficient of about 0.4 to 0.5 at both 250°C and 500°C, without a sharp increase in the friction coefficient. Moreover, the temperature rise has little effect on the friction coefficient. No peeling or penetrating damage is found in the wear tracks of the wear-resistant coating, indicating that the wear-resistant coating formed by this invention is more suitable for high-temperature friction conditions.

[0052] Electrodynamic polarization and AC impedance tests were performed using a CS350 electrochemical workstation purchased from Wuhan KOST Instrument Co., Ltd., to evaluate the corrosion resistance of F347, Stl6, and Stl6 / TiN. The electrodynamic polarization curves were fitted, and the test results from the curves are summarized in Table 1 below.

[0053]

[0054] Please see Figure 6According to Table 1, the corrosion current density of F347 in a 3.5 wt% NaCl solution is 1.526 μA / cm². 2 The corrosion current density of Stl6 is 0.746 μA / cm. 2 The corrosion current density of Stl6 is 0.37 μA / cm. 2 This indicates that the wear-resistant coating can significantly reduce the corrosion rate of the sample. In addition, the critical electrochemical dissolution potential of Stl6 / TiN reaches 939mV, which is significantly higher than that of Stl6 (584mV) and F347 (151.6mV), and the AC impedance modulus is the largest across the entire frequency range, indicating that the wear-resistant coating has good passivation ability and the strongest surface stability.

[0055] Comparative Example 1: The only difference between this comparative example and Example 1 is that a transition layer of Stellite 6 alloy was prepared on the substrate surface using laser cladding in this comparative example. The thickness of the transition layer was approximately 3 mm. During laser cladding, the defocusing amount was +5 mm; the nozzle working distance was 11 mm; the laser power was 2.6 kW; the cladding speed was 16 m / min; the single-pass lateral movement was 0.5 mm; the powder feed rate was 25 g / min; the protective gas flow rate was 13 L / min; and the powder carrier gas flow rate was 5.5 L / min.

[0056] The cross-section of the wear-resistant coating observed under a scanning electron microscope shows that the transition layer of this comparative example is mainly composed of columnar crystals, which results in high hardness and wear resistance, but also high brittleness, low toughness, and weak buffering and interfacial bonding ability.

[0057] Please see Figure 7 The LC1 value of TiN and Stellite 6, obtained through nano-scratch testing, was approximately 31.2 N, significantly lower than the result in Example 1. This is due to differences in internal crystal structure caused by different preparation processes. Furthermore, laser cladding uses a high-energy-density laser as a heat source, resulting in extremely rapid cooling of the molten pool and a highly non-equilibrium solidification process. This easily leads to the formation of fine compositional segregation zones and residual stress concentration areas within the cladding layer. Simultaneously, the small molten pool size and large temperature gradient during laser cladding make it extremely sensitive to the molten pool atmosphere and oxygen content, readily forming trace oxide inclusions near alloy grain boundaries or interfaces, which is detrimental to strong interlayer bonding.

[0058] The beneficial effects of this invention lie in providing a composite wear-resistant coating and its preparation method. This not only achieves a gradient transition from tough metal to high-hardness ceramic in its structure, reducing the failure risk caused by abrupt changes in interfacial thermal stress and elastic modulus, and effectively suppressing cracking and peeling of the coating under thermal cycling and mechanical loads, but also comprehensively strengthens the key surfaces of the substrate by increasing hardness, improving tribological behavior, and enhancing surface passivation capabilities, significantly improving the scratch and wear resistance of the substrate surface. This invention forms a transition layer through multiple plasma arc welding processes, controlling the current, voltage, welding speed, and shielding gas during welding to achieve a dense internal structure with high toughness and continuous metallurgical bonding at the interface. Simultaneously, it stabilizes the oxygen content at an extremely low level of approximately 0.00325%, thereby significantly improving the porosity and oxidation problems commonly found in traditional weld overlay layers.

[0059] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0060] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a wear-resistant coating, characterized in that, include: Clean and remove the oxide layer from the substrate surface to obtain the base surface; A transition layer is formed on the surface of the base surface by multiple plasma arc welding with Stellite 6 welding material; The surface of the transition layer is ground and cleaned to form a bonding surface; A wear-resistant layer is formed on the surface of the bonding surface by chemical vapor deposition, and the wear-resistant layer is composed of titanium nitride.

2. The method for preparing the wear-resistant coating as described in claim 1, characterized in that, Each weld overlay forms an alloy film with a thickness of 1.5 mm to 3 mm, and the total thickness of the transition layer is 1.6 cm to 2.4 cm.

3. The method for preparing the wear-resistant coating as described in claim 2, characterized in that, The welding current is any value between 120A and 180A, the arc voltage is any value between 22V and 28V, the welding speed is any value between 80mm / min and 150mm / min, and the welding is carried out under the protection of inert gas.

4. The method for preparing the wear-resistant coating as described in claim 1, characterized in that, The roughness of the mating surface is any value between 0.2 μm and 0.4 μm.

5. The method for preparing the wear-resistant coating as described in claim 1, characterized in that, The chemical vapor deposition is performed by arc ion plating or magnetron sputtering.

6. The method for preparing the wear-resistant coating as described in claim 5, characterized in that, Before performing the chemical vapor deposition, the bonding surface is ultrasonically cleaned and bombarded with argon ions. During the chemical vapor deposition, the nitrogen partial pressure is any value between 0.1 Pa and 0.4 Pa, the substrate bias voltage is any value between -40 V and -120 V, and the deposition temperature is any value between 300 °C and 450 °C.

7. The method for preparing the wear-resistant coating as described in claim 5, characterized in that, When the wear-resistant layer is deposited by the arc ion plating, the deposition chamber pressure is any value between 0.15 Pa and 0.5 Pa, and the titanium target current is any value between 50 A and 65 A.

8. The method for preparing the wear-resistant coating as described in claim 1, characterized in that, The thickness of the wear-resistant layer is any value between 2μm and 10μm.

9. A wear-resistant coating, characterized in that, It is prepared by the method for preparing the wear-resistant coating as described in any one of claims 1 to 8.

10. The wear-resistant coating as described in claim 9, characterized in that, The substrate is austenitic stainless steel F347, and the internal structure of the transition layer consists of equiaxed crystals, columnar crystals, and fine equiaxed crystals.

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