Femtosecond laser surface micro-texture reinforced NiCoCrAlY high-temperature coating, preparation method and application thereof

Abstract

This invention discloses a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with microtextured surface. The coating surface features a regularly arranged array of micro-pits, with β-NiAl as the main phase and containing γ / γ′ phases, but no α-Cr phase precipitation. The interface between the coating and the substrate is clear, without a continuous interdiffusion layer. The coating preparation method includes: 1. Substrate surface pretreatment; 2. Electron beam physical vapor deposition (EBPD) to deposit the NiCoCrAlY coating; 3. Vacuum annealing to obtain a phase-stable coating; 4. Laser microtexturing to fabricate the micro-pit array structure on the coating surface. The micro-pit array structure on the coating surface of this invention achieves multiple synergistic enhancement mechanisms, improving the high-temperature oxidation resistance of the coating. This invention actively regulates the oxidation behavior of the coating through femtosecond laser surface microtexturing, improving its ultra-high temperature performance. It has high process integration and is suitable for hot-end components of high-end equipment such as aero-engines and gas turbines.

Description

Technical Field

[0001] This invention belongs to the interdisciplinary field of high-temperature protective coatings and laser surface engineering, specifically relating to a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with microtextured surface, its preparation method, and its application. Background Technology

[0002] High-temperature alloy hot-end components rely on thermal barrier coating systems for effective protection under extreme service environments. This system typically consists of an outer ceramic insulating layer (such as YSZ) and an inner metallic binder layer. NiCoCrAlY alloy, as the most widely used binder material, directly determines the service life of the entire coating system due to its high-temperature oxidation resistance. However, traditional NiCoCrAlY coatings have the following inherent limitations during long-term high-temperature exposure: First, the thermally grown oxides formed on the coating surface produce significant wrinkles during growth, leading to localized stress concentration and becoming the starting point for ceramic layer cracking and spalling; second, spinel-like mixed oxides (such as NiCr2O4 and CoCr2O4) are easily formed in the oxide film, which grow rapidly but have poor protective properties, accelerating coating degradation; third, elemental interdiffusion between the coating and the high-temperature alloy substrate, especially in single-crystal high-temperature alloys, can lead to the formation of secondary reaction zones and topologically close-packed phases, severely deteriorating the mechanical properties of the substrate.

[0003] To address the aforementioned issues, recent research has focused on three main directions: first, optimizing the coating phase composition through optimization, such as reducing Cr content to suppress α-Cr phase precipitation and controlling Al content to stabilize the β-NiAl phase; second, improving oxide film adhesion and inhibiting element interdiffusion by adding active elements (Y, Hf, Zr, etc.) or noble metal elements (Pt); and third, mitigating interfacial stress through multilayer or gradient structure design. While these methods have made some progress, they all emphasize the improvement of the bulk material system of the coating, with insufficient attention paid to the active design and control of the coating surface state, thus limiting their effectiveness in further improving coating performance at ultra-high temperatures.

[0004] In coating preparation technology, different process routes each have their advantages and disadvantages. Atmospheric plasma spraying technology has high deposition efficiency, but the coating often has defects such as porosity and weak interlayer bonding, affecting its density and lifespan. Magnetron sputtering or multi-arc ion plating technology can obtain dense and well-bonded coatings, but the deposition rate is usually low (<10μm / h), limiting production efficiency. Electron beam physical vapor deposition technology exhibits unique comprehensive advantages: it can not only achieve a high deposition rate (usually ≥60μm / h), meeting engineering efficiency requirements, but also produces a dense coating with a unique columnar crystal structure. This columnar crystal structure not only helps to alleviate thermal stress, but also provides a rapid channel for the outward diffusion of Al elements in the coating, thereby helping to promote the rapid formation and healing of the protective α-Al2O3 oxide film, laying a good structural foundation for improving the intrinsic oxidation resistance of the coating.

[0005] Femtosecond laser processing technology, as an advanced manufacturing method characterized by non-contact, ultra-precision, and extremely small heat-affected zone, exhibits unique advantages in the field of micro- and nano-structure processing of material surfaces. Its ultrashort pulse characteristics (102) -15 The femtosecond laser (on the order of s) allows for material removal primarily through a non-thermal ablation mechanism, producing almost no heat-affected zone, slag, or microcracks, making it particularly suitable for surface modification of precision components. Introducing femtosecond laser microtexturing technology into high-temperature coating surface engineering, by designing and processing specific surface morphologies, holds promise for actively intervening in the surface energy distribution and stress state of the oxide film, thus regulating its nucleation and growth behavior. Secondly, the microstructure provides additional surface area and oxide transport channels, promoting rapid formation of a protective oxide film. Thirdly, the structured surface can accommodate some of the oxide volume expansion, alleviating growth stress and suppressing oxide film wrinkling. This provides a novel approach to overcoming the performance bottlenecks of traditional coatings at ultra-high temperatures.

[0006] However, applying femtosecond laser microtexturing technology to strengthen the surface of NiCoCrAlY coatings still faces many challenges: it is necessary to determine the microstructure geometry parameters (shape, size, depth, distribution density) suitable for high-temperature oxidation environments, as these parameters directly affect the growth kinetics of the oxide film; it is necessary to optimize laser process parameters to avoid damage to the coating phase structure or the introduction of microcracks; it is necessary to clarify the performance evolution law and failure mechanism of microtextured coatings under long-term thermal cycling conditions; and it is necessary to establish the process compatibility of EB-PVD deposition, vacuum annealing, and laser processing.

[0007] Currently, there are no publicly available reports, either domestically or internationally, on the application of femtosecond laser surface microtexturing technology to enhance the high-temperature performance of NiCoCrAlY coatings. Therefore, it is necessary to propose an integrated process of "EB-PVD deposition + vacuum annealing + femtosecond laser microtexturing" to actively regulate the oxidation behavior of the coating through surface microstructure design, providing an innovative technical approach to solving the high-temperature failure problem of traditional NiCoCrAlY coatings. Summary of the Invention

[0008] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with surface microtexture. This coating surface, by setting a regularly arranged array of micro-pits, promotes uniform nucleation of the oxide film, effectively releases growth stress, alters the diffusion paths of oxygen and alloying elements, and inhibits oxide film wrinkles and spinel phase formation. This synergistically and significantly improves the high-temperature oxidation resistance of the coating, solving the technical problems of insufficient oxidation resistance, oxide film wrinkles, harmful phase formation, and interfacial interdiffusion in traditional NiCoCrAlY coatings during ultra-high temperature service.

[0009] To solve the above technical problems, the technical solution adopted by the present invention is as follows: a femtosecond laser surface microtexturation-enhanced NiCoCrAlY high-temperature coating, characterized in that the coating surface has a regularly arranged micro-pit array structure, and the coating is mainly composed of β-NiAl phase and contains γ / γ′ phase, without α-Cr phase precipitation; the interface between the coating and the substrate is clear, without a continuous interdiffusion layer.

[0010] The coating surface of this invention has a regularly arranged micro-pit array structure. This surface microtexture enhances coating performance through the synergistic effect of multiple physical mechanisms: the curvature effect of the micro-pit edges provides high-density uniform nucleation sites for α-Al2O3, promoting uniform nucleation of the α-Al2O3 oxide film in NiCoCrAlY; at the same time, the micro-pit array structure increases the specific surface area, accelerates Al diffusion, and is beneficial to Al transport and early oxide film coverage; the micro-pit space can effectively accommodate oxide volume expansion, release growth stress, and thus inhibit oxide film wrinkles and spinel phase formation; in addition, the micro-pit array structure of this surface can change the diffusion path of oxygen and alloying elements, inhibit the formation of harmful phases such as spinel, and produce a certain physical barrier effect on the interdiffusion between the coating and the substrate, ensuring a clear interface between the coating and the substrate without a continuous interdiffusion layer.

[0011] The aforementioned femtosecond laser-enhanced NiCoCrAlY high-temperature coating with microtextured surface is characterized in that the micro-pits in the micro-pit array structure are circular, square, or hexagonal, with a depth of 15μm to 45μm, a characteristic size of 25μm to 60μm, and a center-to-center distance between adjacent micro-pits that is 1.5 to 2.5 times the characteristic size. The area coverage of the micro-pit array structure is 80% to 100%. For circular micro-pits, the characteristic size is the diameter; for square or hexagonal micro-pits, the characteristic size is the circumcircle diameter or the distance between opposite sides.

[0012] The aforementioned femtosecond laser-reinforced NiCoCrAlY high-temperature coating with microtextured surface is characterized in that the chemical composition of the coating, by mass percentage, is: Co 18%~25%, Cr 15%~22%, Al 8%~12%, Y 0.3%~0.8%, with the balance being Ni and unavoidable impurities; the thickness of the coating is 60μm~120μm.

[0013] Meanwhile, this invention also discloses a method for preparing a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with microtextured surface, as described above, characterized in that the method includes the following steps: Step 1: Substrate pretreatment: Grinding, polishing and cleaning the surface of the nickel-based superalloy substrate to obtain the pretreated substrate; Step 2, Coating Deposition: A NiCoCrAlY coating is deposited on the substrate surface after the pretreatment in Step 1 using electron beam physical vapor deposition. Step 3, Vacuum annealing: The NiCoCrAlY coating deposited in Step 2 is vacuum annealed to obtain a coating with a stable phase structure. Step 4: Femtosecond laser microtexturing: A regularly arranged array of micro-pits is fabricated on the coating surface that has a stable phase structure in Step 3 using a femtosecond laser system.

[0014] This invention typically uses second- or third-generation nickel-based single-crystal high-temperature alloys as the substrate. After cutting, the substrate is ground, polished, and cleaned to obtain a clean and flat surface. Then, using a NiCoCrAlY alloy ingot as the source, an electron beam physical vapor deposition method is used, with controlled vacuum, substrate temperature, and workpiece rotation speed, to deposit a NiCoCrAlY coating on the pretreated substrate surface. Vacuum annealing heat treatment is then performed to eliminate internal stress and stabilize the coating phase composition, resulting in a coating with a β-NiAl phase as the main component, a dense structure, and good adhesion to the substrate. Finally, a femtosecond laser process is used to scan and process a regular array of micro-pits with preset geometric features on the coating surface.

[0015] The above-mentioned preparation method is characterized in that the nickel-based high-temperature alloy matrix in step one is the second-generation nickel-based single-crystal high-temperature alloy N5, which is first polished step by step with 400# to 2000# sandpaper, and then polished to a mirror effect with diamond polishing paste with a particle size of 1.5μm~2.5μm and nylon cloth.

[0016] The above-described preparation method is characterized in that the process parameters of the electron beam physical vapor deposition method in step two are: the background vacuum degree does not exceed 6.0 × 10⁻⁶. -3 Pa, substrate temperature 790℃~810℃, workpiece rotation speed 10r / min~15r / min, deposition rate 40μm / h~80μm / h.

[0017] The above preparation method is characterized in that the process parameters for vacuum annealing in step three are: vacuum degree not exceeding 5.0 × 10⁻⁶. -3 Pa, heating rate 5℃ / min~10℃ / min, annealing temperature 1000℃~1100℃, holding time 2h~4h, cooling with furnace.

[0018] The above-described preparation method is characterized in that the process parameters of the femtosecond laser system in step four are: laser wavelength 1030nm±10nm, pulse width 200fs~500fs, repetition frequency 50kHz~200kHz, scanning speed 100mm / s~300mm / s, scanning spacing 40mm~80mm, focused spot diameter 15μm~30μm, single pulse energy 0.2mJ~1.0mJ, and energy density 1.5J / cm³. 2 ~6.0J / cm 2 The number of cycles is 20 to 80, and the processing environment is an argon protective atmosphere with an oxygen content of less than 100 ppm.

[0019] The above preparation method is characterized in that, in step four, the coating with a stable phase structure is ultrasonically cleaned before processing, and the cleaning medium is a mixed solution of anhydrous ethanol and acetone in a volume ratio of 3:1, and the cleaning time is 15 min to 30 min.

[0020] Furthermore, this invention also discloses the application of the femtosecond laser-reinforced NiCoCrAlY high-temperature coating in a high-temperature oxidation environment, characterized in that the coating forms a continuous and dense α-Al2O3 oxide film on its surface under thermal cycling conditions of 1100℃.

[0021] Compared with the prior art, the present invention has the following advantages: 1. Significantly improved high-temperature oxidation resistance: This invention promotes uniform nucleation of α-Al2O3 oxide film in NiCoCrAlY by setting a regularly arranged micro-pit array structure on the coating surface. This is beneficial for the transport of Al elements and early coverage of the oxide film, effectively releases growth stress, changes the diffusion path of oxygen and alloying elements, and inhibits oxide film wrinkles and spinel phase formation. Thus, it synergistically and significantly improves the high-temperature oxidation resistance of the coating. After 100 cycles of thermal cycling at 1100℃, the oxidation weight gain of this coating is reduced by 40%~50% compared with traditional coatings. Moreover, the oxide film is dense and continuous, making it suitable for high-temperature long-life protection of hot-end components such as turbine blades of aero-engines.

[0022] 2. Improved interface stability: The micro-dimple array structure on the coating surface of this invention changes the diffusion path of oxygen and alloying elements, thereby creating a certain physical barrier effect on the interdiffusion between the coating and the substrate. This ensures that there is no obvious interdiffusion layer at the interface between the coating and the substrate, reducing the thickness of the secondary reaction zone of the substrate by more than 60%, effectively protecting the mechanical properties of the high-temperature alloy substrate and extending the overall life of the component.

[0023] 3. Strong process compatibility: This invention first uses electron beam physical vapor deposition (EB-PVD) to prepare a NiCoCrAlY coating on a high-temperature alloy substrate, taking into account its high deposition efficiency and excellent coating density and columnar crystal structure. After vacuum annealing, a coating substrate with a stable phase structure is obtained. Subsequently, femtosecond laser processing is used to precisely construct a regularly arranged micro-pit array structure on the coating surface. Since femtosecond laser processing is a low-temperature, non-contact processing method, it hardly changes the original phase structure and interface state of the coating, realizing the active control of the high-temperature oxidation behavior of the coating surface. The process integration is high, breaking through the traditional technical approach of relying on material bulk modification and opening up a new way to improve the performance of high-temperature coatings through surface engineering.

[0024] 4. Flexible and Adjustable Design: The micro-dimple array structure on the coating surface of this invention is based on the theory of oxide film growth kinetics. By controlling the geometric parameters (shape, depth, feature size, and spacing) of the micro-dimple array structure, it can effectively alleviate oxide film growth stress and inhibit wrinkle formation while promoting the formation of a protective α-Al2O3 oxide film. It can also be optimized and adjusted according to specific service temperature, atmosphere, and life requirements. A quantitative correlation between the geometric features of the microstructure and the oxidation performance of the coating (such as nucleation density, Al diffusion, and stress tolerance) has been established, enabling customized design of the coating's anti-oxidation performance and a wide range of applications.

[0025] 5. Broad Engineering Application Prospects: This invention develops a femtosecond laser low-damage processing window suitable for NiCoCrAlY coatings, achieving high-quality, crack-free fabrication of microstructures. Simultaneously, it completes the process matching and integration of EB-PVD deposition, vacuum annealing, and femtosecond laser processing, ensuring the consistency and repeatability of the coating from macro / micro structure to performance. It possesses engineering application potential. This method is stable and effective, providing an innovative and feasible technical solution for solving the protection challenges of hot-end components in high-end equipment such as aero-engines and gas turbines under ultra-high temperature environments.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a cross-sectional morphology diagram of the NiCoCrAlY coating with a stable phase structure obtained after vacuum annealing in Example 1 of the present invention.

[0028] Figure 2 This is a cross-sectional morphology diagram of the NiCoCrAlY coating with a stable phase structure obtained after vacuum annealing in Example 1 of the present invention.

[0029] Figure 3 This is a surface morphology image of the NiCoCrAlY coating after femtosecond laser microtexturing in Embodiment 1 of the present invention.

[0030] Figure 4 This is a cross-sectional morphology diagram of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 1 of the present invention.

[0031] Figure 5 This is a cross-sectional morphology diagram of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 1 of the present invention.

[0032] Figure 6 The images show the XRD patterns of the NiCoCrAlY coating processed by femtosecond laser microtexturing in Example 1 of the present invention and the NiCoCrAlY coating with stable phase structure in Comparative Example 1 after oxidation at 1100℃ for 10h.

[0033] Figure 7 This is a graph showing the oxidation weight gain of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 1 of the present invention after isothermal oxidation at 1100℃ for 10 hours.

[0034] Figure 8 The image shows the microstructure and phase diagram of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 1 of this invention after 100 thermal cycles at 1100℃.

[0035] Figure 9 This is a surface morphology image of the NiCoCrAlY coating after femtosecond laser microtexturing in Embodiment 2 of the present invention.

[0036] Figure 10 This is a cross-sectional morphology diagram of the NiCoCrAlY coating after femtosecond laser microtexturing in Embodiment 2 of the present invention.

[0037] Figure 11 This is a cross-sectional morphology diagram of the NiCoCrAlY coating after femtosecond laser microtexturing in Embodiment 2 of the present invention. Detailed Implementation

[0038] Example 1 The femtosecond laser-enhanced NiCoCrAlY high-temperature coating in this embodiment has a regularly arranged array of micro-pits, and the coating is dominated by the β-NiAl phase and contains γ / γ′ phases, with no α-Cr phase precipitation. The interface between the coating and the second-generation single-crystal high-temperature alloy N5 substrate is clear, with no continuous interdiffusion layer.

[0039] The method for preparing the femtosecond laser-enhanced NiCoCrAlY high-temperature coating with surface microtexturing in this embodiment includes the following steps: Step 1, Matrix Pretreatment: The second-generation single-crystal high-temperature alloy N5 rod is cut into circular samples with a diameter × thickness of Φ15mm × 2mm by electrical discharge wire cutting, and a small hole with an inner diameter of Φ1.0mm is machined on the edge of the sample for suspension to obtain the N5 matrix. The surface of the N5 substrate was polished stepwise with sandpaper ranging from 400# to 2000#, and then polished with 2.5μm diamond polishing paste and nylon cloth. After polishing, the surface basically achieved a mirror effect and the surface roughness Ra < 100nm. Then, it was ultrasonically cleaned for 15min in metal detergent, deionized water, and acetone-ethanol mixture (volume ratio 3:1) for 15min respectively, and dried at 80℃ to obtain the pretreated N5 substrate. Step 2, Coating Deposition: Using a high-power EB-PVD equipment from the Paton Welding Institute in Ukraine, and with NiCoCrAlY alloy ingots prepared by vacuum induction melting as the target material, electron beam physical vapor deposition was employed. The vacuum chamber of the EB-PVD equipment was first evacuated to 5.0 × 10⁻⁶. -3 Pa, preheat the substrate to 800℃ (calibrated by both infrared thermometer and thermocouple), set the workpiece rotation speed to 12r / min, deposition rate to 60μm / h, electron beam power to 18kW, and deposition time to 90min, and deposit a NiCoCrAlY coating with a thickness of about 100μm on the N5 substrate surface after the pretreatment in step one; the chemical composition of the NiCoCrAlY alloy ingot by mass percentage is: Co 23%, Cr 17%, Al 11%, Y 0.5%, with the balance being Ni and unavoidable impurities; Step 3, Vacuum Annealing: Place the N5 substrate with the NiCoCrAlY coating deposited in Step 2 into a quartz tube, connect it to a high vacuum unit, and evacuate to 4.5 × 10⁻⁶. -3 After Pa, the sample is sealed and placed in a box-type vacuum sintering furnace. The temperature is increased to 1050℃ at a rate of 10℃ / min and held for 2 hours. After the furnace cools to below 80℃, the sample is taken out to obtain a NiCoCrAlY coating with a stable phase structure. The coating is uniformly silvery-gray and has no oxidation discoloration on the surface. Step 4: Femtosecond Laser Microtexturing: First, the NiCoCrAlY coating with a stable phase structure from Step 3 is ultrasonically cleaned for 30 minutes using a mixture of anhydrous ethanol and acetone in a 3:1 volume ratio. Then, a regularly arranged array of micro-pits is fabricated on the cleaned coating surface using a Light Conversion Pharos femtosecond laser system. The process parameters for the femtosecond laser system are: laser wavelength 1030 nm, pulse width 300 fs, repetition rate 100 kHz, scanning speed 200 mm / s, scanning spacing 60 mm, focused spot diameter 20 μm, single pulse energy 0.5 mJ, and energy density 3.0 J / cm³. 2 The process involved 50 cycles, a bidirectional filling mode for the scanning path, and argon gas protection during processing at a flow rate of 25 L / min. The oxygen content in the cavity was monitored in real time and found to be below 30 ppm. The micro-pit array structure consisted of a square array of micro-pits within a 15 mm × 15 mm area, with a pit depth of approximately 30 μm. The characteristic dimension, i.e., the diameter of the inscribed circle of the square micro-pit, was 30 μm, and the center-to-center distance between adjacent micro-pits was 2.0 times the characteristic dimension. The area coverage of the micro-pit array structure was 100%, and the surface of the NiCoCrAlY coating after processing exhibited a regular dot matrix structure without slag or oxide color.

[0040] Coating characterization results in this embodiment: Figure 1 and Figure 2 These are cross-sectional and cross-sectional morphology images of the NiCoCrAlY coating with a stable phase structure obtained after vacuum annealing in this embodiment. Figure 1 and Figure 2 It can be seen that the NiCoCrAlY coating with stable phase structure exhibits a typical columnar crystal structure, without penetrating pores, and has a clear interface with the substrate.

[0041] Figure 3 , Figure 4 and Figure 5 These are images showing the surface, cross-section, and sectional morphology of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 1 of this invention. Figure 3 , Figure 4 and Figure 5 As can be seen, in this embodiment, after femtosecond laser microtexturing, a neat and regular array of square micro-pits is formed on the surface of the NiCoCrAlY coating. The edges of the micro-pits are clear and sharp, the depth is uniform (30μm±2μm), there are no micro-cracks at the bottom and sidewalls of the micro-pits, and the heat-affected zone is less than 3μm.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that the femtosecond laser microtexturing process in step four was not performed, and the NiCoCrAlY coating with a stable phase structure obtained in step three was directly used as the final product morphology.

[0043] Performance Testing and Analysis Thermal cycling oxidation experiments were conducted at 1100℃ on the NiCoCrAlY coating processed by femtosecond laser microtexturing in Example 1 of this invention and the NiCoCrAlY coating with a stable phase structure in Comparative Example 1. The thermal cycling procedure was as follows: the sample was placed in an alumina crucible and then placed in an automatic lifting muffle furnace preheated to 1100℃. After holding at this temperature for 60 min, the sample was removed and cooled to room temperature (≤50℃) in a forced air cooling device for 10 min. This constituted one thermal cycle. The sample was removed after every 20 thermal cycles and weighed using an electronic balance with an accuracy of 0.01 mg. The oxidation weight gain per unit area ΔW / A was calculated. After 100 thermal cycles, the experiment was stopped, and the sample cross-section was analyzed by SEM and XRD.

[0044] Figure 6 The images show the XRD patterns of the NiCoCrAlY coating processed by femtosecond laser microtexturing in Example 1 and the NiCoCrAlY coating with a stable phase structure in Comparative Example 1 after oxidation at 1100℃ for 10 hours. Figure 6 It can be seen that the main phase of the coating after vacuum annealing (i.e., the annealed coating) is β-NiAl (PDF#65-3245), accompanied by a small amount of γ-Ni solid solution phase (PDF#65-0380), and there is no α-Cr phase diffraction peak. That is, after a short oxidation of 10 hours, the oxidation products generated on the coating surface are mainly α-Al2O3 film, indicating that femtosecond laser microtexturing can promote the formation of protective α-Al2O3 film.

[0045] (1) Oxidation kinetics results: The oxidation weight gain curves of the two groups of samples after being oxidized at 1100℃ for 10 h were recorded using a thermogravimetric analyzer (TGA), as follows: Figure 7 As shown, both conform to the parabolic law (ΔW / A). 2 = Kp·t; from Figure 7 As can be seen, the oxidative weight gain of Example 1 (standard microtexture) is only 0.08 mg / cm³. 2 Comparative Example 1 (non-textured) showed an oxidative weight gain of 0.13 mg / cm³. 2 Calculations showed that the oxidation rate of the microtextured coating in Example 1 decreased by about 38%, indicating that the femtosecond laser microtexturing of the present invention can effectively improve the high-temperature oxidation resistance of the NiCoCrAlY coating.

[0046] (2) Oxide film morphology analysis: such as Figure 8As shown, Figures (a) and (c) are microscopic morphology diagrams at different magnifications, Figure (d) is an enlarged view of the area within the box in Figure (c), and Figure (b) is a phase diagram. Figure 8 As can be seen, in Example 1 of this invention, after femtosecond laser microtexturing, the NiCoCrAlY coating formed a continuous and dense oxide film with a thickness of approximately 2.5 μm after 100 cycles at 1100℃ (60 min holding time followed by 10 min cooling time per cycle). Referring to the phase diagram in Figure (b), the oxide film mainly consists of a dense inner layer of α-Al₂O₃ and a very small amount of NiCr₂O₄ spinel on the outer layer. This indicates that although the microtexturing did not completely suppress spinel growth, it significantly slowed down the oxidation rate. The oxide film exhibited good adhesion to the coating interface, without wrinkles or cracks. Compared to Comparative Example 1, the NiCoCrAlY coating in Example 1, after femtosecond laser microtexturing, still showed significant advantages in oxidation resistance under high-temperature conditions.

[0047] Comparison of the results of Example 1 and Comparative Example 1 and mechanistic analysis show that the femtosecond laser-enhanced NiCoCrAlY coating improves its antioxidant performance through the following mechanisms: ① The curvature at the edge of the micro-pits provides high-density nucleation sites, promoting early uniform nucleation of α-Al2O3; ② The micro-pit array structure increases the effective surface area by about 60%~80%, accelerating the outward diffusion of Al elements, which is beneficial for the rapid formation of a continuous protective film; ③ The micro-pits can accommodate about 15%~20% of the oxide volume expansion, releasing growth stress; ④ The micro-pit array structure can change the oxygen diffusion path and inhibit the formation of spinel phase; ⑤ The surface micro-texture has a certain hindering effect on coating / substrate interdiffusion.

[0048] (3) Long-term performance prediction: Based on extrapolation of oxidation kinetic data, the NiCoCrAlY coating processed by femtosecond laser microtexturing in Example 1 of this invention reaches 25 mg / cm³ at 1100℃. 2 The critical weight gain time (typically corresponding to coating failure) is approximately 2800 h, while the NiCoCrAlY coating with a stable phase structure in Comparative Example 1 has a lifespan of approximately 1200 h, indicating that the theoretical lifespan of the microtextured coating of the present invention is extended to approximately 2.2 times that of Comparative Example 1.

[0049] Example 2 The femtosecond laser-enhanced NiCoCrAlY high-temperature coating in this embodiment has a regularly arranged array of micro-pits, and the coating is dominated by the β-NiAl phase and contains γ / γ′ phases, with no α-Cr phase precipitation. The interface between the coating and the second-generation single-crystal high-temperature alloy N5 substrate is clear, with no continuous interdiffusion layer.

[0050] The method for preparing the femtosecond laser-enhanced NiCoCrAlY high-temperature coating with surface microtexturing in this embodiment includes the following steps: Step 1, Matrix Pretreatment: Same as in Example 1; Step 2, Coating Deposition: Same as in Example 1; Step 3, Vacuum annealing: Same as in Example 1; Step 4: Femtosecond Laser Microtexturing: First, the NiCoCrAlY coating with a stable phase structure from Step 3 is ultrasonically cleaned for 20 minutes using a mixture of anhydrous ethanol and acetone in a 3:1 volume ratio. Then, a regularly arranged array of micro-pits is fabricated on the cleaned coating surface using a Light Conversion Pharos femtosecond laser system. The process parameters for the femtosecond laser system are: laser wavelength 1030 nm, pulse width 250 fs, repetition rate 80 kHz, scanning speed 150 mm / s, scanning spacing 50 mm, focused spot diameter 20 μm, single pulse energy 0.5 mJ, and energy density 3.0 J / cm³. 2 The process involved 20 cycles, a bidirectional filling mode for the scanning path, and argon gas protection during processing at a flow rate of 25 L / min. The oxygen content in the cavity was monitored in real time and found to be below 30 ppm. The micro-pit array structure consisted of a square array of micro-pits within a 15 mm × 15 mm area, with a pit depth of approximately 15 μm. The characteristic dimension, i.e., the diameter of the inscribed circle of the square micro-pit, was 25 μm, and the center-to-center distance between adjacent micro-pits was 2.0 times the characteristic dimension. The area coverage of the micro-pit array structure was 100%, and the surface of the NiCoCrAlY coating after processing exhibited a regular dot matrix structure without slag or oxide color.

[0051] Example 2: Coating characterization results: Figure 9 , Figure 10 and Figure 11 These are images showing the surface, cross-section, and sectional morphology of the NiCoCrAlY coating after femtosecond laser microtexturing in Example 2 of this invention. Figure 9 , Figure 10 and Figure 11 As can be seen, in this embodiment, after femtosecond laser microtexturing, a neat and regular array of square micro-pits is formed on the surface of the NiCoCrAlY coating. The edges of the micro-pits are clear, the depth is uniform (15μm±2μm), there are no micro-cracks at the bottom and sidewalls of the micro-pits, and the heat-affected zone is less than 2μm.

[0052] Upon testing, the oxide film morphology of Example 2 of the present invention is similar to that of Example 1, both forming a continuous and dense α-Al2O3 oxide film with good interfacial bonding.

[0053] In summary, the femtosecond laser-based surface microtexture-enhanced NiCoCrAlY coating preparation process developed in this invention significantly improves the high-temperature oxidation resistance and interface stability of the coating by actively regulating the oxide film growth behavior through precisely designed surface microstructures. This method is reliable and effective, providing an innovative technical approach for optimizing the performance of high-temperature protective coatings, and has broad application prospects in the protection of hot-end components of high-end equipment such as aero-engines and gas turbines.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A femtosecond laser-enhanced NiCoCrAlY high-temperature coating with microtextured surface, characterized in that, The coating surface has a regularly arranged array of micro-pits, and the coating is mainly composed of β-NiAl phase, containing γ / γ′ phase, with no α-Cr phase precipitation; the interface between the coating and the substrate is clear, without a continuous interdiffusion layer.

2. The femtosecond laser-reinforced NiCoCrAlY high-temperature coating with surface microtexturation as described in claim 1, characterized in that, The micro-pit array structure has circular, square, or hexagonal micro-pits with a depth of 15μm to 45μm and a feature size of 25μm to 60μm. The center-to-center distance between adjacent micro-pits is 1.5 to 2.5 times the feature size, and the area coverage of the micro-pit array structure is 80% to 100%.

3. The femtosecond laser-reinforced NiCoCrAlY high-temperature coating with surface microtexturation as described in claim 1, characterized in that, The chemical composition of the coating by mass percentage is: Co 18%~25%, Cr 15%~22%, Al 8%~12%, Y 0.3%~0.8%, with the balance being Ni and unavoidable impurities; the thickness of the coating is 60μm~120μm.

4. A method for preparing a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with surface microtexturation as described in any one of claims 1 to 3, characterized in that, The method includes the following steps: Step 1: Substrate pretreatment: Grinding, polishing and cleaning the surface of the nickel-based superalloy substrate to obtain the pretreated substrate; Step 2, Coating Deposition: A NiCoCrAlY coating is deposited on the substrate surface after the pretreatment in Step 1 using electron beam physical vapor deposition. Step 3, Vacuum annealing: The NiCoCrAlY coating deposited in Step 2 is vacuum annealed to obtain a coating with a stable phase structure. Step 4: Femtosecond laser microtexturing: A regularly arranged array of micro-pits is fabricated on the coating surface that has a stable phase structure in Step 3 using a femtosecond laser system.

5. The preparation method according to claim 4, characterized in that, The nickel-based superalloy matrix mentioned in step one is the second-generation nickel-based single-crystal superalloy N5. It is first polished step by step with sandpaper ranging from 400# to 2000#, and then polished to a mirror finish with diamond polishing paste with a particle size of 1.5μm~2.5μm and nylon cloth.

6. The preparation method according to claim 4, characterized in that, The process parameters for electron beam physical vapor deposition in step two are: a background vacuum level not exceeding 6.0 × 10⁻⁶. -3 Pa, substrate temperature 790℃~810℃, workpiece rotation speed 10r / min~15r / min, deposition rate 40μm / h~80μm / h.

7. The preparation method according to claim 4, characterized in that, The process parameters for vacuum annealing in step three are: vacuum degree not exceeding 5.0 × 10⁻⁶. -3 Pa, heating rate 5℃ / min~10℃ / min, annealing temperature 1000℃~1100℃, holding time 2h~4h, cooling with furnace.

8. The preparation method according to claim 4, characterized in that, The process parameters for the femtosecond laser system described in step four are as follows: laser wavelength 1030nm±10nm, pulse width 200fs~500fs, repetition frequency 50kHz~200kHz, scanning speed 100mm / s~300mm / s, scanning spacing 40mm~80mm, focused spot diameter 15μm~30μm, single pulse energy 0.2mJ~1.0mJ, and energy density 1.5J / cm³. 2 ~6.0J / cm 2 The number of cycles is 20 to 80, and the processing environment is an argon protective atmosphere with an oxygen content of less than 100 ppm.

9. The preparation method according to claim 4, characterized in that, In step four, the coating with a stable phase structure is ultrasonically cleaned before processing. The cleaning medium is a mixed solution of anhydrous ethanol and acetone in a volume ratio of 3:1, and the cleaning time is 15 min to 30 min.

10. The application of a femtosecond laser-enhanced NiCoCrAlY high-temperature coating with surface microtexturation as described in any one of claims 1 to 3 in a high-temperature oxidizing environment, characterized in that, Under thermal cycling conditions at 1100℃, a continuous and dense α-Al2O3 oxide film forms on the surface of the coating.

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