Novel wear-resistant high-temperature oxidation-resistant gradient structure coating and preparation method thereof

Abstract

The invention relates to the technical field of material surface modification, and discloses a novel wear-resistant high-temperature oxidation-resistant gradient structure coating and a preparation method thereof.The preparation method comprises the following steps that S1, a metal matrix is sequentially subjected to oil removal, sand blasting, cleaning and drying, so that a clean surface with the surface roughness Ra being 1.5-2.5 micrometers is obtained; s2, pulse laser is adopted for cleaning the surface of the base body, continuous laser is adopted for laser quenching under nitrogen protection, air cooling is adopted for natural cooling after quenching, and a hardened layer of 0.2-0.6 mm is formed on the surface layer; s3, a Cr layer, a TiN layer, a TiAlN layer and a TiAlCrN layer are sequentially deposited on the surface of the base body; and S4, the coating deposited in the step S3 is heated to 700 + / -10 DEG C in the inert atmosphere at the heating rate of 10 DEG C / min, heat preservation is conducted for 2 hours, and then the coating is cooled to 150 DEG C or below along with the furnace and taken out. The method not only solves the problem of interlayer stripping caused by difference of thermal expansion coefficients of a traditional coating, but also remarkably improves the oxidation resistance, wear resistance and high-temperature stability of the coating by reasonably designing the coating thickness and element distribution.

Description

Technical Field

[0001] This invention relates to the field of material surface modification technology, and in particular to a novel wear-resistant, high-temperature, and antioxidant gradient structure coating and its preparation method. Background Technology

[0002] Multicomponent metal nitride coatings, due to their high hardness, good thermal stability, and wear resistance, have become an important functional coating system for modern high-speed cutting tools, molds, and high-temperature service components. Current research focuses primarily on using Ti-N as the parent phase and introducing metallic or non-metallic elements to form multicomponent compounds, such as TiAlN, TiCrN, TiCN, TiBN, and TiSiN, to improve their mechanical properties and oxidation resistance. Existing research shows that adding Al to TiN and adjusting the Ti / Al atomic ratio can form (Ti,Al)N solid solution nitrides, increasing the oxidation resistance temperature of TiN from approximately 550℃ to approximately 700℃. In the cutting tool field, TiAlN coatings exhibit higher hardness and better high-temperature wear resistance compared to TiN coatings.

[0003] On the other hand, introducing Cr into Ti or TiN can form TiCrN or Ti-Cr-N coatings, which can generate a Cr2O3 oxide film at high temperatures. Cr2O3, due to its high melting point, high density, and excellent oxygen diffusion barrier properties, is considered a key factor in improving the high-temperature oxidation resistance of metal nitride coatings. Nitrides, carbides, and borides of transition metals such as Ti, Cr, and Zr generally exhibit intermetallic compound characteristics, while their oxides, such as TiO2, Cr2O3, and ZrO2, are typical high-melting-point ionic compounds with excellent chemical stability at high temperatures. Therefore, introducing Al and Cr into the TiN matrix can improve its oxidation resistance, mechanical properties, and high-temperature chemical stability to a certain extent.

[0004] Besides metallic elements, the introduction of non-metallic elements such as C, B, and Si has also been shown to improve the wear resistance, toughness, and tribological properties of TiN or Ti coatings. For example, TiCN coatings exhibit higher corrosion resistance and wear resistance, as well as a lower friction factor, compared to TiN, and are therefore widely used in the mold industry. In summary, multi-component composites represent an important development direction for improving the overall performance of coatings.

[0005] However, existing TiN, TiAlN, and TiAlCrN coating systems still have significant limitations in high-temperature oxidation resistance: (1) The Cr content in TiAlCrN coating is generally ≤20at.%, which makes it difficult to form a continuous and dense Cr2O3 oxide layer at high temperature. It only shows a local island distribution. Its oxidation weight gain usually exceeds 1.5mg / cm² at 650℃ and 100h, and its antioxidant performance is insufficient. (2) Traditional TiAlN coatings gain more than 2 mg / cm² at 650 °C due to oxidation. The Al2O3 generated by preferential oxidation of Al is mostly a loose and porous structure (porosity > 15%), which is difficult to form an effective oxidation barrier. (3) The preferential formation of Al2O3 will hinder the diffusion of Cr to the surface, making it difficult for the protective oxide film of Cr2O3 to be formed continuously, resulting in the inability to significantly improve the antioxidant capacity. (4) Existing processes generally cannot achieve the gradient distribution of each element in Ti-Al-Cr-N between layers, while the gradient transition structure is crucial for reducing interfacial stress, promoting Cr diffusion and oxide film formation. (5) Traditional single-layer or non-gradient multilayer structures are prone to interface embrittlement and delamination cracking after high-temperature annealing, which cannot meet the service requirements of high-speed steel, high-temperature alloy and other substrates at high temperatures.

[0006] Therefore, given the shortcomings of the existing technology, how to achieve a controllable gradient distribution of elements in the Ti-Al-Cr-N multi-component coating, so that Cr can effectively diffuse under high temperature conditions and form a continuous and dense Cr2O3 oxide film in situ, while obtaining a structurally stable high-temperature miscible region, thereby significantly improving the wear resistance, thermal stability and high-temperature oxidation resistance of the coating, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0007] In view of this, the purpose of this invention is to provide a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating and its preparation method. The core of this invention lies in precisely controlling the Ti:Al:Cr atomic ratio to 1:1:1 and optimizing the deposition process to generate a continuous Cr2O3 barrier in situ on the coating surface, breaking through the 700℃ oxidation resistance limit. By employing a unique gradient coating structure and combining it with nanocrystalline technology, long-term stability of the coating material in high-temperature and high-pressure environments is achieved. This invention not only solves the problem of interlayer delamination caused by differences in thermal expansion coefficients in traditional coatings, but also significantly improves the coating's oxidation resistance, wear resistance, and high-temperature stability through reasonable design of coating thickness and element distribution.

[0008] The present invention solves the above-mentioned technical problems through the following technical means: In a first aspect, the present invention provides a method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating, characterized by comprising the following steps: S1. The metal substrate is sequentially degreased, sandblasted, cleaned and dried to obtain a clean surface with a surface roughness of Ra1.5-2.5μm; S2. The substrate surface is cleaned using pulsed laser, and laser quenching is performed using continuous laser under nitrogen protection. After quenching, natural cooling is performed using air cooling to form a hardened layer of 0.2-0.6 mm on the surface. S3. Sequentially deposit a Cr layer, a TiN layer, a TiAlN layer, and a TiAlCrN layer on the substrate surface; S4. The coating deposited in step S3 is heated to 700±10℃ in an inert atmosphere at a heating rate of 10℃ / min, held at that temperature for 2 hours, and then cooled to below 150℃ in the furnace before being removed.

[0009] Preferably, the specific parameters of step S2 are as follows: pulsed laser cleaning uses a 1064nm laser with a laser power of 250W and a pulse frequency of 30kHz, and is scanned under argon protection with a 40% overlap rate and a speed of 750mm / s, a beam diameter of 1.0mm, and a positive focal length of +2mm; laser quenching uses a 1070nm continuous laser with a power of 1.5kW, a scanning speed of 600mm / s, a negative defocus of -0.5mm, and is carried out in nitrogen gas with a purity of 99.99wt.%, and the argon gas flow rate is constantly controlled at 15L / min.

[0010] Preferably, in step S3, the Cr base layer is 5×10 -4 -5×10 -3 1-5 μm were deposited by magnetron sputtering at a power of 2.2-2.8 kW under vacuum and high-purity argon, and then cooled at a rate not exceeding 5 °C / min after deposition.

[0011] Preferably, in step S3, the TiN layer deposition includes: A Ti-rich transition layer was formed within 0-10 minutes at 1.3-1.7 kW under an Ar:N2=80:20 atmosphere. Within 10-40 minutes, the nitrogen content is increased to 50%, and the sputtering power is increased to 3kW to form Cr→CrN. X →TiN X gradient layer; TiN with a stoichiometric ratio of N:Ti = 1:1 was deposited at an Ar:N2 = 50:50 temperature range for 40-60 minutes. After deposition, the sample was annealed for 1 hour under argon protection at 400℃.

[0012] Preferably, in step S3, the TiAlN layer deposition includes: An Ar:N2 mixture of 70:30 was initially introduced, and the substrate was preheated to 400°C. A Ti / Al dual target was used with a power ratio of 3kW:1.5kW. The Al target power was increased to 2.0 kW within 0-15 minutes to form an Al-rich transition layer; Simultaneously increase the nitrogen ratio to 50% and reduce the Al target power to 1.5kW within 15-35 minutes to decrease the Al content from 35 at.% to 25 at.%. A standard TiAlN layer was formed within 35-45 minutes in an Ar:N2=50:50 atmosphere with Ti / Al=3kW / 1.5kW. After deposition, the sample was annealed for 1 hour under argon protection at 450℃.

[0013] Preferably, the TiAlN layer is deposited at 400°C, target-substrate distance of 80±5 mm, and substrate rotation of 5 rpm.

[0014] Preferably, in step S3, the TiAlCrN layer deposition includes, on the TiAlN layer surface cleaned by argon plasma bombardment, in an atmosphere of argon and nitrogen mixed in a 1:1 ratio at 450±10℃ and 0.35Pa, increasing the Cr target power from 0.5kW to 1.5kW within 0-15min to form a gradient layer with a Cr content of 5-30 at.% and maintaining the Ti / Al / Cr target power at 1.5kW / 4.0kW / 1.5kW for the next 20min to deposit the TiAlCrN main layer, followed by the deposition of a 40nm nitrogen-rich layer, and annealing at 500℃ for 1.5h in 10Pa argon gas with a heating rate of 5℃ / min to generate a 150±20nm thick (Ti,Cr)2AlN miscible region.

[0015] Preferably, the parameters for argon plasma bombardment cleaning of the TiAlCrN layer deposition are 1.0 kW, 15 min, and 5 × 10⁻⁶ ppm. -3 Pa.

[0016] Preferably, the Ti:Al:Cr atomic ratio in the TiAlCrN layer is 1:1:1.

[0017] Secondly, the present invention provides a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating, which is prepared by the above-described preparation method.

[0018] The beneficial effects of this invention are: 1. This invention improves the effective Cr content in TiAlCrN coatings, breaking through the traditional limitation of ≤20 at.%. By implementing linear gradient control of the Cr target power (0.5kW→1.5kW) and combining it with synergistic power adjustment of multiple targets (Ti, Al, and Cr), the Cr content in the coating is continuously increased from 5 at.% to 30 at.% (with a gradient transition layer thickness of approximately 0.5μm). This structure significantly improves the limitation of insufficient Cr content in traditional TiAlCrN coatings, providing sufficient diffusion driving force for Cr during high-temperature oxidation, which is beneficial for the formation of a stable high-temperature protective oxide film.

[0019] 2. This invention achieves in-situ continuous generation of Cr2O3, significantly improving high-temperature oxidation resistance. When the Cr content on the coating surface reaches 25–30 at.%, the high-temperature oxidation process is dominated by Cr2O3, forming a continuous and dense Cr2O3-Al2O3 composite oxide film (film porosity <3%). This structure reduces the oxygen diffusion coefficient to 10. -14 cm 2 Oxidation rate constant K on the order of / s p Reduced to 10 -8 g 2 / cm 4 Below ·s, the formation tendency of porous Al2O3 oxides is significantly suppressed. The coating showed an oxidation weight gain of only 0.12 mg / cm² at 1100℃ / 100h, compared to the traditional TiAlCrN coating (>1.5 mg / cm²). 2 (at 650℃) decreased significantly.

[0020] 3. This invention further reduces interfacial stress and improves the structural stability of the coating under high-temperature environments through a multi-layer gradient structure. This invention constructs a continuous compositional gradient system from Cr layers, TiN layers, TiAlN layers to TiAlCrN layers, allowing Ti, Al, Cr, and N to gradually transition between layers. This structure eliminates the abrupt compositional changes present in traditional multilayer films, effectively reducing the risk of cracking during oxidation due to thermal stress and uneven diffusion. In particular, the decreasing Al content transition between TiAlN and TiAlCrN (35 at.% → 25 at.%), and the stoichiometric gradient between TiN and TiAlN, enable the coating to maintain high film-substrate bonding strength under high-temperature cycling.

[0021] 4. The high-temperature annealing of this invention induces the formation of a stable (Ti,Cr)₂AlN miscible phase, improving oxidation resistance and anti-scraping ability. After annealing at 500℃ for 1.5h in an inert atmosphere, a (Ti,Cr)₂AlN miscible region with a thickness of 150±20nm is formed at the TiAlN / TiAlCrN transition interface. This miscible phase has high thermal stability and interfacial toughness, and can work synergistically with the surface Cr₂O₃ film during oxidation to improve the overall heat integrity and anti-scraping performance of the coating, enabling it to maintain long-term service at higher temperature ranges. Attached Figure Description

[0022] Figure 1 This is a flowchart of the present invention; Figure 2 This is a comparison chart of the hardness of each layer of the present invention and the hardness after heat treatment.

[0023] Figure 3 This is a microstructure and elemental distribution diagram of the sample prepared in this invention. Detailed Implementation The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. According to a first aspect of the invention, see Figure 1 The detailed preparation method is as follows: S1. The substrate is sequentially degreased, sandblasted, cleaned and dried to obtain a clean surface with a surface roughness of Ra1.5-2.5μm; S11. Degreasing: The substrate surface is degreased with industrial-grade acetone or an alkaline degreasing agent with pH=10-12 at room temperature (25±5℃). The immersion method is selected (the substrate is completely immersed in the solvent and treated with 40kHz ultrasound for 10-15 minutes).

[0024] S12. Sandblasting for rust removal: Use white corundum with a particle size of 80-120 mesh at an air pressure of 0.5-0.7MPa, a spray distance of 100-150mm, and a spray angle of 70°-90° (perpendicular to the substrate surface). This achieves a surface roughness of Ra=1.5-2.5μm and a uniform grayish-white metallic luster, thoroughly removing the oxide layer and rust.

[0025] S13. Cleaning and Drying: Immediately after sandblasting, blow away residual abrasive with 0.3MPa compressed air, then immerse in anhydrous ethanol for ultrasonic cleaning (40kHz, 10 minutes), followed by rinsing with flowing deionized water three times (≥1 minute each time). Drying is performed using hot air (60-80℃) or vacuum drying (50℃, 10- 2 Pa, 30 minutes).

[0026] The final acceptance criteria are: no stains when wiped with white gloves, surface contact angle < 5°, and the substrate must be transferred to the next process within 2 hours after treatment.

[0027] S2. The substrate surface is cleaned using pulsed laser and then laser hardened using continuous laser under nitrogen protection. After hardening, it is naturally cooled by air cooling to form a hardened layer of 0.2-0.6 mm on the surface. S21. Low-power laser cleaning: After pretreatment, the substrate is fixed on a three-dimensional moving platform. Low-power laser cleaning is performed using a 1064nm fiber pulsed laser. The laser power is set to 250W, the pulse frequency to 30kHz, the beam spot diameter to 1.0mm, and the scanning speed to 750mm / s. Simultaneously, the defocusing amount is adjusted to +2mm (positive defocusing state) to reduce energy density and protect the substrate. Argon gas with a purity of 99.99wt.% is introduced throughout the cleaning process as a protective gas, with a constant flow rate of 15L / min to effectively suppress oxidation. During operation, the laser beam is incident perpendicularly on the substrate surface. First, a 10×10mm area is selected for parameter testing. After observing that the surface oxide layer is completely removed (appearing a uniform silver-white color), a full-surface grid scan is performed with an overlap rate of 38%-40% (path spacing = 1.0mm × (1-0.4) = 0.6mm).

[0028] Immediately after cleaning, a quality verification was performed: visual inspection ensured the absence of black spots, discoloration, or melting marks, while energy dispersive spectroscopy (EDS) confirmed that the surface oxygen content was below 5 at.%.

[0029] S22. High-Power Laser Quenching: Laser quenching uses a 1070nm continuous fiber laser with a power set at 1.5kW and a Φ3mm circular spot. After the substrate is fixed, nitrogen protection with a purity of 99.99wt.% is activated (flow rate 20L / min). Large components are preheated to 300℃ to reduce thermal stress, followed by quenching at a scanning speed of 600mm / s. The laser head is kept at a negative defocus of -0.5mm to focus energy on the surface layer, and single-pass scanning is performed with an overlap rate of 33%-36% (center-to-center distance between adjacent passes is 1.95mm). During the quenching process, the surface temperature is monitored in real time using an infrared thermometer and strictly controlled within the range of 850–1000℃ to ensure austenitization. After treatment, natural cooling (self-quenching effect) is used; forced cooling is strictly prohibited.

[0030] The final quality verification included: using a microhardness tester (500g load) to test the surface hardness to be ≥45HRC; using metallographic etching method (4% nitric acid alcohol) to determine the hardened layer depth to be 0.2-0.6mm; and using SEM to confirm that the microstructure was crack-free martensite + retained austenite.

[0031] S3. Sequentially deposit a Cr layer, a TiN layer, a TiAlN layer, and a TiAlCrN layer on the substrate surface; Deposition is completed in four steps in a PVD device; S31, Cr Underlayer Deposition: To ensure the optimal Cr coating thickness of 1-5 μm, precision Cr deposition must be performed using a magnetron sputtering (MS) system. High vacuum environment (5 × 10⁻⁶) -4 -5×10 -3The process is carried out in Pa), with high-purity argon gas (≥99.99wt.%) as the working atmosphere. During sputtering, the argon gas ionizes into high-energy ions under the influence of an electric field, bombarding the chromium target with a constant power of 2.5kW, causing chromium atoms to be released in gaseous form and directionally deposited onto the substrate surface. To optimize the coating adhesion strength, the substrate needs to be preheated to 200℃. This temperature promotes the diffusion and bonding of chromium atoms on the substrate surface while avoiding phase transformation of the substrate due to excessively high temperatures. The deposition process lasts for 45 minutes. By precisely controlling the sputtering power and time, the coating thickness is made uniform and stable to the target value of 1-5μm. After the coating is completed, the system is naturally cooled to below 80℃ at ≤5℃ / min under a protective atmosphere to avoid coating cracking caused by thermal stress. A roughness of 0.5≤Ra≤0.8 can prevent coating non-bonding and avoid columnar grain coarsening.

[0032] S32, TiN Intermediate Layer Deposition: After depositing a 1-5 μm Cr layer, a TiN layer is deposited using a PVD system, with a target thickness of 2-5 μm. The process begins with pretreatment: the Cr layer surface is plasma-cleaned or rinsed with deionized water to thoroughly remove adsorbed impurities. The formal coating is performed in a high vacuum environment at 5 × 10⁻⁶ rpm. -4 -5×10 -3 The process is carried out in Pa, with argon (Ar) and nitrogen (N) gas introduced. 2） A mixed gas (initial ratio 80:20) was used. The substrate was preheated to 350°C to activate surface diffusion, followed by sputtering of a high-purity titanium target (≥99.95wt.%) at 2.8-3.2kW. Titanium atoms reacted with nitrogen in the plasma to form TiN vapor phase deposits. The deposition process lasted 60 minutes, and the thickness was accurately measured in real time. To achieve a gradient transition between the Cr and TiN layers, a three-dimensional synergistic control strategy was adopted: In the initial stage of deposition (0-10 minutes), the Ar:N2=80:20 atmosphere ratio was maintained, and low-power sputtering at 1.3–1.7kW was used to form a titanium-rich transition layer (Ti-rich), promoting metallurgical bonding at the Cr / TiN interface; in the gradient stage (10-40 minutes), the nitrogen ratio was linearly increased to 50%, while the sputtering power was gradually increased from 1.5kW to 3kW. During this process, a Cr-Ti-N compositional gradient layer (Cr→CrN) with a thickness of approximately 0.5μm was deposited. X →TiN X）In the final stage (40-60 minutes), an Ar:N2 atmosphere of 50:50 and a power of 2.8-3.2 kW were maintained, and TiN with a stoichiometric ratio of N / Ti = 1 was deposited to ensure coating hardness. Throughout the deposition process, the target-substrate distance was strictly controlled within 80 ± 5 mm to ensure uniform plasma coverage of the substrate surface. Immediately after deposition, the substrate was annealed at 400℃ under argon protection for 1 hour, increasing the bonding strength to ≥70 MPa through interfacial atomic interdiffusion. This process, through the combined effects of dynamic gas ratio, gradual power adjustment, and geometric parameter optimization, completely eliminates abrupt interfacial stress, achieving a continuous gradient transition in hardness from the Cr layer (65-70 HRC) to the TiN layer (68–73 HRC).

[0033] S33, TiAlN Intermediate Coating Deposition: A 2-5 μm TiAlN layer is deposited on top of a 1-5 μm TiN layer using a PVD system (deposition time 45 minutes). Pretreatment involves plasma cleaning to ensure a clean TiN surface (Ra ≤ 0.1 μm). The deposition environment is maintained at a high vacuum (5 × 10⁻⁶). -4 -5×10 -3 Initially, an Ar:N2 mixture of 70:30 was introduced, and the substrate was preheated to 400℃ to activate interfacial diffusion. Simultaneously, the Ti target (3kW) and Al target (1.5kW) were activated, and the Ti / Al atomic ratio in the coating was adjusted to 2:1 by controlling the power ratio (Ti:Al=2:1) ​​to ensure high-temperature stability. In the initial deposition stage (0-15 minutes), the nitrogen ratio (N2=30%) at the end of the TiN layer was maintained, and the Al target power was simultaneously increased to 2.0 kW (Ti target maintained at 3 kW). By reducing the Ti / Al ratio, an aluminum-rich transition layer (Al-rich, Al=35 at.%) was deposited, utilizing the ductility of aluminum to buffer the interfacial stress. In the gradual transition stage (15-35 minutes), the nitrogen ratio was linearly increased to 50%, while the Al target power was gradually reduced from 2.0 kW to 1.5 kW (Ti target stabilized at 3 kW). During this process, a TiAl-N compositional gradient layer with a thickness of about 0.4 μm was formed (Al content decreased from 35 at.% to 25 at.%). In the final stage (35-45 minutes), the Ar:N2=50:50 atmosphere and Ti / Al target power (3 kW / 1.5 kW) were fixed, and standard stoichiometric TiAlN (Al=33 at.%) was deposited. The entire process was carried out under conditions of a symmetrical dual-target layout (target-substrate distance 80±5mm) and uniform substrate rotation (5rpm) to ensure uniform distribution of components in three-dimensional space. This strategy, through the coupling effect of dynamically increasing nitrogen ratio and gradually changing Al / Ti power, constructs a continuous Al-Ti-N composition gradient band in the interface region, achieving a smooth transition of mechanical properties from TiN layer to TiAlN layer hardness gradient: 72–76HRC → 74–78HRC.

[0034] S34. TiAlCrN Top Coating Deposition: After atomic-level cleaning of the TiAlN coating surface by argon plasma bombardment (1.0 kW / 15 min / 5 × 10⁻³ Pa), a TiAlCrN layer was deposited using a closed-field unbalanced magnetron sputtering system (TeerUDP-650). The deposition chamber was evacuated to a basic vacuum of 5 × 10⁻³ Pa. -4 Pa, a high-purity mixed gas of Ar:N2=1:1 (≥99.999wt.%) is introduced, and the working pressure is maintained at 0.35Pa. The substrate is radiantly heated to 450±10℃ and held for 30min to activate interfacial activity. Three sets of high-purity targets (Ti 99.99wt.%, Al 99.95wt.%, Cr 99.98wt.%) are arranged symmetrically in a 120° ring, and the target-substrate distance is precisely controlled at 80±2mm. Dynamic gradient control was implemented throughout the 70-minute deposition process: For the initial 15 minutes, the Cr target power was linearly increased from 0.5 kW to 1.5 kW (0.035 kW / min), while the Al target power was simultaneously increased from 1.5 kW to 3.5 kW, and the Ti target power decreased to 1.2 kW, forming a 0.5 μm gradient transition layer with a continuously increasing Cr content from 5 at.% to 30 at.% (GDOES verified). For the next 20 minutes, the Ti:Al:Cr kW power combination was maintained, and the deposition rate stabilized at 45 nm / min, resulting in the deposition of a 40 nm nitrogen-rich hardened layer (N > 45 at.%). The matrix employed a combined revolution (5 rpm) and rotation (15 rpm) motion mode (planetary carrier eccentricity 50 mm) to achieve three-dimensional spatial compositional homogeneity (deviation < ±2 at.%). After deposition, the mixture was annealed at 500℃ for 1.5h in an argon atmosphere (10Pa) with a heating rate of 5℃ / min. This annealed the mixture to form a 150±20nm thick (Ti,Cr)2AlN miscible region at the interface, reducing the columnar crystal ratio from 35% to <5%. The bonding strength was measured to be 90±5MPa by scratch test (ASTM C1624).

[0035] The coating has been systematically verified: nanoindentation (ISO14577) shows a hardness of 78–82 HRC, originating from Cr2N nanophase (20-50 nm) reinforcement; the weight gain after 100 hours of oxidation at 1100℃ is only 0.12 mg / cm³. 2 This is attributed to the Al2O3-Cr2O3 composite oxide film (1.2 μm); no substrate corrosion was observed after >1000 hours of salt spray testing (ASTM B117), and Cr... +3 Passivation film impedance > 10 5 Ω·cm²; Falling ball impact (ISO 19447) failure cycles > 1.2 × 10⁻⁶ 5 The gradient structure crack propagation energy reached 7.3 J / m². TOF-SIMS depth spectroscopy confirmed that Cr... +2 Signal linear growth (R 2=0.995), XRD detected a continuous shift in the solid solution diffraction peak (43.5°→42.8°), and cross-sectional TEM showed a gradual lattice transition from TiAlN(111) to TiAlCrN(220). This process fabricated TiAlN→TiAl 0.8 Cr 0.2 N→TiAl 0.7 Cr 0.3 The N→TiAlCrN gradient structure resulted in a final coating thickness tolerance of ±0.1μm (using a white light interferometer).

[0036] S4. The coating deposited in step S3 is heated to 700±10℃ in an inert atmosphere at a heating rate of 10℃ / min, held at that temperature for 2 hours, and then cooled to below 150℃ in the furnace before being removed.

[0037] The deposited coating sample was placed in a tube furnace under a high-purity nitrogen atmosphere (N2 purity ≥ 9.999 wt.%) and heated to 700 ± 10 °C at a heating rate of 10 °C / min. After holding at this temperature for 2 hours, it was cooled with the furnace to below 150 °C and removed. The high temperature promoted atomic diffusion within the coating, filling the columnar intergranular gaps formed by PVD deposition; nitrogen atoms penetrated deep into the interlayer interface, forming Ti-Al-Cr-N interdiffusion bands. The TiAlN phase partially transformed into the harder c-(Ti,Al,Cr)N cubic phase.

[0038] Example 1: Application of coating on high-speed steel drill bits (W6Mo5Cr4V2 substrate) Take φ10 mm × 120 mm W6Mo5Cr4V2 5CrNiMo (domestic grade) The high-speed steel drill bit is subjected to ultrasonic degreasing with acetone (40kHz / 15min), followed by white corundum blasting (100 mesh / 0.6MPa / Ra2.0μm); laser cleaning (1064nm / 250W / +2mm defocus / argon 15L / min) to reduce oxygen residue to <3at.%; and laser quenching (1070nm / 1.5kW / Φ3mm) to form a 0.5mm hardened layer (hardness 48HRC). PVD deposition was performed sequentially: magnetron sputtering of a 5 μm Cr layer (2.5 kW / 200℃ / 45 min); deposition of a 2 μm TiN layer (Ar:N2=80:20→50:50 gradient, power 1.5→3 kW / 60 min), annealed at 400℃ for 1 h; dual-target sputtering of a 2 μm TiAlN layer (Ti target 3 kW / Al target 1.5→2.0 kW, Ar:N2=70:30→50:50), annealed at 450℃; closed-field sputtering of a 2 μm TiAlCrN layer (Ti:Al:Cr=1.2:3.5:1.5 kW, Ar:N2=1:1, orbital 5 rpm + rotation 15 rpm), annealed at 500℃ for 1.5 h. Finally, nitrogen heat treatment at 700℃ for 2 h was performed to generate the c-(Ti,Al,Cr)N cubic phase (proportion >40%). Measured coating hardness gradient: Cr layer 65-70 HRC → TiN layer 68-73 HRC → TiAlN layer 74-78 HRC → TiAlCrN layer 78-82 HRC; weight gain of 0.11 mg / cm² after 100 h of oxidation at 1100℃.

[0039] Depend on Figure 2 It can be seen that before and after heat treatment, the hardness of each layer shows a continuous increase from the substrate to the surface (60HRC for the substrate → 76HRC for the top layer), which avoids the interface stress concentration caused by the sudden change in hardness in traditional coatings and improves the bonding strength between the film and the substrate (the scratch test in the patent verifies the bonding strength ≥90 MPa).

[0040] The overall hardness increased after heat treatment (e.g., the matrix hardness increased from 60 HRC to 66 HRC) because nitrogen annealing promoted atomic diffusion and formed a more stable c-(Ti,Al,Cr)N cubic phase; the TiAlCrN top layer achieved a hardness of 77 HRC after heat treatment, which was attributed to the Cr content gradient increasing to 30 at.%, forming a nanoscale Cr2N reinforcing phase, and the nitrogen-rich hardened layer further improved wear resistance.

[0041] Depend on Figure 3It can be concluded that the continuous increase of Cr element from the bottom layer to the surface layer (0→30 at.%), combined with the dynamic balance of Al, Ti, and N, forms an atomic ratio of Ti:Al:Cr=1:1:1 on the surface layer, laying the compositional foundation for the in-situ formation of the "Cr2O3-Al2O3 composite oxide film" at high temperature. The crack-free interface shown in the SEM cross-sectional image proves the effectiveness of "multi-layer annealing treatment (400-500℃) promoting atomic diffusion", avoiding the interface peeling caused by the abrupt change in composition in traditional coatings.

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating, characterized in that, Includes the following steps: S1. The metal substrate is sequentially degreased, sandblasted, cleaned and dried to obtain a clean surface with a surface roughness of Ra1.5-2.5μm; S2. The substrate surface is cleaned using pulsed laser, and laser quenching is performed using continuous laser under nitrogen protection. After quenching, natural cooling is performed using air cooling to form a hardened layer of 0.2-0.6 mm on the surface. S3. Sequentially deposit a Cr layer, a TiN layer, a TiAlN layer, and a TiAlCrN layer on the substrate surface; S4. The coating deposited in step S3 is heated to 700±10℃ in an inert atmosphere at a heating rate of 10℃ / min, held at that temperature for 2 hours, and then cooled to below 150℃ in the furnace before being removed.

2. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 1, characterized in that, The specific parameters for step S2 are as follows: pulsed laser cleaning uses a 1064nm laser with a laser power of 250W and a pulse frequency of 30kHz. It is scanned under argon protection with a 40% overlap rate and a speed of 750mm / s. The beam diameter is 1.0mm and the positive focal length is +2mm. Laser quenching uses a 1070nm continuous laser with a power of 1.5kW, a scanning speed of 600mm / s, a negative defocusing amount of -0.5mm, and is carried out in nitrogen gas with a purity of 99.99wt.%. The argon gas flow rate is kept constant at 15L / min.

3. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 1, characterized in that, In step S3, the Cr sublayer is 5×10 -4 -5×10 -3 1-5 μm were deposited by magnetron sputtering at a power of 2.2-2.8 kW under vacuum and high-purity argon, and then cooled at a rate not exceeding 5 °C / min after deposition.

4. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 1, characterized in that, In step S3, the TiN layer deposition includes: A Ti-rich transition layer was formed within 0-10 minutes at 1.3-1.7 kW under an Ar:N2=80:20 atmosphere. Within 10-40 minutes, the nitrogen content is increased to 50%, and the sputtering power is increased to 3kW to form Cr→CrN. X →TiN X gradient layer; TiN with a stoichiometric ratio of N:Ti = 1:1 was deposited at an Ar:N2 = 50:50 temperature range for 40-60 minutes. After deposition, the sample was annealed for 1 hour under argon protection at 400℃.

5. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 1, characterized in that, In step S3, the TiAlN layer deposition includes: An Ar:N2 mixture of 70:30 was initially introduced, and the substrate was preheated to 400°C. A Ti / Al dual target was used with a power ratio of 3kW:1.5kW. The Al target power was increased to 2.0 kW within 0-15 minutes to form an Al-rich transition layer; Simultaneously increase the nitrogen ratio to 50% and reduce the Al target power to 1.5kW within 15-35 minutes to decrease the Al content from 35 at.% to 25 at.%. A standard TiAlN layer was formed within 35-45 minutes in an Ar:N2=50:50 atmosphere with Ti / Al=3kW / 1.5kW. After deposition, the sample was annealed for 1 hour under argon protection at 450℃.

6. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 5, characterized in that, The TiAlN layer was deposited at 400℃, with a target-substrate distance of 80±5mm and a substrate rotation of 5rpm.

7. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 1, characterized in that, In step S3, the TiAlCrN layer deposition includes: on the TiAlN layer surface cleaned by argon plasma bombardment, in an atmosphere of argon and nitrogen mixed in a 1:1 ratio at 450±10℃ and 0.35Pa, increasing the Cr target power from 0.5kW to 1.5kW within 0-15min to form a gradient layer with a Cr content of 5-30 at.%; maintaining the Ti / Al / Cr target power at 1.5kW / 4.0kW / 1.5kW for the next 20min to deposit the TiAlCrN main layer; then depositing a 40nm nitrogen-rich layer; and annealing at 500℃ for 1.5h in 10Pa argon gas with a heating rate of 5℃ / min to generate a 150±20nm thick (Ti,Cr)2AlN miscible region.

8. The method for preparing a novel wear-resistant, high-temperature, oxidation-resistant gradient structure coating according to claim 7, characterized in that, The parameters for argon plasma bombardment cleaning of the deposited TiAlCrN layer were 1.0 kW, 15 min, and 5 × 10⁻⁶ m³ / h. -3 Pa.

9. The method for preparing a novel wear-resistant, high-temperature, and oxidation-resistant gradient structure coating according to claim 7, characterized in that, The atomic ratio of Ti:Al:Cr in the TiAlCrN layer is 1:1:

1.

10. A novel wear-resistant, high-temperature, and antioxidant gradient structure coating, prepared by the preparation method described in any one of claims 1-9.

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