Composite coating and method for producing the same

Abstract

The present disclosure provides a composite coating and a preparation method thereof, the preparation method comprising: gradient preheating a substrate and a stainless steel powder; forming a stainless steel coating on the surface of the substrate by a laser cladding process using the stainless steel powder; and forming a zirconium-based amorphous alloy layer on the surface of the stainless steel coating by a plasma spraying process using a zirconium-based amorphous alloy powder; wherein the chemical general formula of the zirconium-based amorphous alloy powder is Zr 63 Cu 20‑x Al 10+x Fe5Ti2, wherein 0≤x≤8; and the surface of the zirconium-based amorphous alloy powder is coated with a transition metal oxide layer. The composite coating prepared by the present disclosure forms a Fe-Zr intermetallic compound diffusion bonding layer at the interface, realizes metallurgical bonding, has high interface bonding strength, and has high hardness, low porosity and excellent corrosion resistance as a whole.

Description

Technical Field

[0001] This disclosure relates to the field of anti-corrosion coatings, and in particular to composite material coatings and their preparation methods. Background Technology

[0002] The production workshop for anode foil used in aluminum electrolytic capacitors is constantly exposed to acid mists such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid. Although a large number of steel and stainless steel equipment in the workshop are coated with anti-corrosion paint for protection, the anti-corrosion paint generally suffers from problems such as poor adhesion, insufficient acid resistance, and easy blistering and peeling in actual use. The effective protection period is only 3-6 months, and frequent shutdowns for maintenance seriously affect the continuity of production.

[0003] Zirconium-based amorphous alloys, due to their unique amorphous structure, possess high strength, high hardness, high elastic limit, and excellent corrosion resistance, demonstrating application potential in the field of surface protective coatings. However, using zirconium-based amorphous alloys as coating materials presents the following technical challenges: First, the significant difference in thermal expansion coefficients and thermal conductivity between zirconium-based amorphous alloys and commonly used metal substrates such as steel leads to excessive interfacial thermal stress during direct spraying, easily causing cracks or even coating peeling. Second, they are extremely sensitive to oxygen content, easily undergoing oxidation and crystallization during high-temperature spraying, and the superior performance of amorphous alloys depends entirely on their amorphous structure. Third, although existing technologies include coating schemes combining amorphous alloys with aluminum alloys, the aluminum alloy transition layer has low strength, poor thermal compatibility with the steel substrate, and is prone to softening during high-temperature spraying, making it difficult to provide stable support for large-area coatings.

[0004] Stainless steel, with its similar thermophysical properties to steel substrates, high strength, and corrosion resistance, is theoretically suitable as a transition layer between zirconium-based amorphous alloys and steel substrates. However, stainless steel has low thermal conductivity, leading to heat accumulation during laser cladding and plasma spraying, which can easily cause thermal stress and cracking. Furthermore, the dense oxide film on the stainless steel surface can reduce the interfacial bonding strength with amorphous alloys. Therefore, further improvements in these areas are desired. Summary of the Invention

[0005] This disclosure provides a method for preparing a composite material coating, comprising: gradient preheating of a substrate and stainless steel powder; forming a stainless steel coating on the surface of the substrate using stainless steel powder via laser cladding; and forming a zirconium-based amorphous alloy layer on the surface of the stainless steel coating using zirconium-based amorphous alloy powder via plasma spraying; wherein the general chemical formula of the zirconium-based amorphous alloy powder is Zr. 63 Cu 20-x Al 10+x Fe5Ti2, where 0≤x≤8; the surface of the zirconium-based amorphous alloy powder is coated with a transition metal oxide layer.

[0006] In some embodiments, gradient preheating includes a first preheating stage and a second preheating stage. The temperature of the first preheating stage is 200°C to 300°C, and the holding time is 10 min to 20 min. The temperature of the second preheating stage is 400°C to 500°C, and the holding time is 10 min to 20 min.

[0007] In some embodiments, during the laser cladding process, auxiliary cooling is applied to the molten pool at a cooling rate of 10² K / s to 10 4 K / s.

[0008] In some embodiments, inert gas or circulating cooling medium is used for auxiliary cooling.

[0009] In some embodiments, the thickness of the transition metal oxide layer is 50 nm to 150 nm. In some embodiments, the transition metal oxide layer includes at least one of yttrium oxide, cerium oxide, or zirconium oxide.

[0010] In some embodiments, the plasma spraying process employs gradient spraying parameters: the plasma output power of the first spraying pass is 12kW to 15kW, and the spraying distance is 100mm to 120mm; the plasma output power of the second and subsequent spraying passes is 8kW to 11kW, and the spraying distance is 80mm to 95mm.

[0011] In some embodiments, the total number of plasma spraying passes is 3 to 6, with an interval of 3 to 8 minutes between adjacent spraying passes, during which the substrate is cooled to 300°C to 400°C.

[0012] In some embodiments, the matrix comprises carbon steel, alloy steel, or cast iron. In some embodiments, the stainless steel powder comprises austenitic stainless steel. In some embodiments, the particle size of the stainless steel powder is 50 μm to 80 μm. In some embodiments, the thickness of the stainless steel coating is 50 μm to 150 μm. In some embodiments, the particle size of the zirconium-based amorphous alloy powder is 50 μm to 100 μm. In some embodiments, the zirconium-based amorphous alloy powder is Zr. 63 Cu 16 Al 14 Fe5Ti2.

[0013] In some embodiments, the laser power used in the laser cladding process is 1kW to 2kW, the spot diameter is 2mm to 3mm, the scanning speed is 100m / min to 140m / min, the overlap rate is 30% to 50%, and the powder feeding rate is 20g / min to 30g / min.

[0014] Another embodiment of this disclosure provides a composite material coating, which is a composite material coating obtained according to any of the above preparation methods.

[0015] In some embodiments, the composite material coating comprises a stainless steel coating, a diffusion bonding layer, and a zirconium-based amorphous alloy layer stacked sequentially. The thickness of the diffusion bonding layer is 1 μm to 5 μm, and the diffusion bonding layer contains an Fe-Zr intermetallic compound. In some embodiments, the amorphous phase content of the zirconium-based amorphous alloy layer is ≥90%, the Vickers hardness is 900 HV to 1200 HV, and the porosity is ≤0.5%.

[0016] This disclosure utilizes stainless steel as the transition layer material, which offers higher strength and better thermal compatibility compared to aluminum alloy transition layers in existing technologies. Furthermore, to address the low thermal conductivity of stainless steel, a gradient preheating process is designed in the laser cladding process to reduce thermal stress and prevent cracking. The composite coating prepared by this disclosure forms an Fe-Zr intermetallic compound diffusion bonding layer at the interface, achieving metallurgical bonding with high interfacial bonding strength. The overall composite coating exhibits high hardness, low porosity, and excellent corrosion resistance. Attached Figure Description

[0017] Figure 1 A schematic flowchart illustrating a method for preparing a composite material coating according to an embodiment of the present disclosure is shown; Figure 2 X-ray diffraction patterns of composite material coatings according to some embodiments of the present disclosure are shown; Figures 3 to 5 Electron backscatter diffraction (EBSD) patterns of stainless steel layers in some embodiments of this disclosure are shown. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the technical solutions of this disclosure will be described in detail below with reference to the accompanying drawings.

[0019] Exemplary embodiments will be described more fully below with reference to the accompanying drawings; however, these exemplary embodiments may be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will enable those skilled in the art to fully understand the scope of this disclosure.

[0020] Where there is no conflict, the various embodiments of this disclosure and the features thereof in the embodiments may be combined with each other.

[0021] As used herein, the term “and / or” includes any and all combinations of one or more related enumerated entries.

[0022] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. As used herein, the singular forms “a” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It will also be understood that when the terms “comprising” and / or “made of” are used in this specification, the presence of the stated feature, integral, step, operation, element, and / or component is specified, but the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or groups thereof is not excluded.

[0023] Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art. It will also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this disclosure, and will not be interpreted as having an idealized or overly formal meaning unless expressly so defined herein. Unless otherwise stated, percentage concentrations herein are mass percentage concentrations.

[0024] This disclosure addresses the technical challenge of the large difference in thermophysical properties between stainless steel and zirconium-based amorphous alloys. By designing specific amorphous alloy components and using a gradient preheating laser cladding process, a composite coating with high interfacial bonding strength, high amorphous phase content, and excellent corrosion resistance is prepared.

[0025] like Figure 1 As shown, embodiments of this disclosure provide a method for preparing a composite material coating, including step S101, which involves gradient preheating of the substrate and stainless steel powder. In some embodiments, the substrate comprises carbon steel, alloy steel, or cast iron. In some embodiments, the stainless steel powder comprises austenitic stainless steel, more preferably 316L stainless steel. By bringing the substrate and stainless steel powder to temperatures close to the initial temperature of the laser cladding process, the thermal stress during the cladding process is effectively reduced, while oxidation of the stainless steel powder due to sudden temperature rise is avoided. For stainless steel, due to its low thermal conductivity, if sufficient preheating is not performed, a large temperature gradient will form around the molten pool during laser cladding, leading to thermal stress concentration and crack formation.

[0026] The preparation method disclosed herein also includes step S102, in which stainless steel powder is used to form a stainless steel coating on the surface of a substrate through a laser cladding process. By using stainless steel as a transition layer material, compared with an aluminum alloy transition layer, stainless steel has higher strength and better thermal compatibility.

[0027] The preparation method disclosed herein further includes step S103, which involves forming a zirconium-based amorphous alloy layer on the surface of a stainless steel coating using zirconium-based amorphous alloy powder via plasma spraying. In some embodiments, the general chemical formula of the zirconium-based amorphous alloy powder is Zr. 63 Cu 20-x Al10+x The alloy composition is Fe5Ti2, where 0 ≤ x ≤ 8. The Zr content is fixed at 63 at%, which falls within the optimal amorphous formation range for zirconium-based amorphous alloys. The introduction of Fe (5 at%) significantly improves the strength and thermal stability of the amorphous alloy. Ti (2 at%) effectively improves corrosion resistance. The ratio of Cu to Al changes in tandem, and the glass transition temperature and the width of the supercooled liquid phase region of the amorphous alloy can be precisely controlled by adjusting the x value. In some embodiments, x=4 is the optimal ratio, at which point the amorphous alloy has the widest supercooled liquid phase region (ΔTx≥50K), which is beneficial for plastic deformation and spreading during plasma spraying.

[0028] In some embodiments, the surface of the zirconium-based amorphous alloy powder is coated with a transition metal oxide layer. In the high-temperature flame of plasma spraying, the coating layer preferentially melts and forms a dense protective film to prevent oxidation of the zirconium-based amorphous alloy powder; at the same time, the coating layer can act as a "lubricant" when impacting the stainless steel layer surface, promoting the spread of molten droplets and improving the interfacial bonding quality.

[0029] In some embodiments, gradient preheating includes a first preheating stage and a second preheating stage. The temperature of the first preheating stage is 200°C to 300°C, and the holding time is 10 min to 20 min. The temperature of the second preheating stage is 400°C to 500°C, and the holding time is 10 min to 20 min. In some embodiments, the first preheating stage mainly removes moisture and low-boiling-point impurities adsorbed on the substrate surface. The second preheating stage brings the substrate and stainless steel powder to temperatures close to the initial temperature of the laser cladding process, effectively reducing thermal stress during cladding and preventing oxidation of the stainless steel powder due to sudden temperature increases.

[0030] In some embodiments, during the laser cladding process, auxiliary cooling is applied to the molten pool at a cooling rate of 10² K / s to 10 4 K / s, for example, is 10 3 The cooling rate is K / s to induce a fine-grained or nanocrystalline structure in the stainless steel layer. In some embodiments, an inert gas or circulating cooling medium is used for auxiliary cooling. Under conventional cooling conditions, stainless steel is prone to forming coarse austenitic dendrites, which reduces the mechanical properties of the coating. By using assisted rapid cooling, the stainless steel layer can achieve a fine-grained or even nanocrystalline structure, improving its hardness and strength. At the same time, the refined grains also facilitate subsequent interfacial atomic diffusion with the amorphous alloy layer.

[0031] In some embodiments, the thickness of the transition metal oxide layer is 50 nm to 150 nm. In some embodiments, the transition metal oxide layer includes at least one of yttrium oxide, cerium oxide, or zirconium oxide. In the high-temperature flame of plasma spraying, these coating layers preferentially melt and form a dense protective film to prevent oxidation of the zirconium-based amorphous alloy powder; simultaneously, these coating layers can act as a "lubricant" when impacting the stainless steel layer surface, promoting the spread of molten droplets and improving the interfacial bonding quality. If the thickness of the transition metal oxide layer is too small, the protective effect is relatively limited; if the thickness of the transition metal oxide layer is too large, thermal stress is easily generated.

[0032] In some embodiments, the plasma spraying process employs gradient spraying parameters: the plasma output power of the first spraying pass is 12kW to 15kW, and the spraying distance is 100mm to 120mm; the plasma output power of the second and subsequent spraying passes is 8kW to 11kW, and the spraying distance is 80mm to 95mm. Since the stainless steel layer has low thermal conductivity, using higher power and a larger spraying distance in the first pass ensures sufficient melting of the amorphous alloy powder while allowing enough time for heat to conduct to the substrate, preventing localized overheating of the stainless steel layer surface. Subsequent passes reduce power and shorten the spraying distance to minimize the thermal impact on the already deposited layer when further deposition is carried out on top of the amorphous alloy layer of a certain thickness, preventing crystallization of the amorphous alloy.

[0033] In some embodiments, the plasma spraying process involves a total of 3 to 6 spraying passes, with an interval of 3 to 8 minutes between adjacent spraying passes. During the interval, the substrate is cooled to 300°C to 400°C. In this disclosure, the spraying substrate refers to the material on which the spraying is performed. For example, when spraying on a stainless steel coating, the spraying substrate is the base material and the stainless steel coating; when performing subsequent spraying passes on some amorphous bonding layers, the spraying substrate is the base material, the stainless steel coating, and the previously sprayed amorphous bonding layer.

[0034] In some embodiments, the particle size of the stainless steel powder is 50 μm to 80 μm. This particle size range is well-suited for laser cladding processes. If the powder is too fine, it is prone to over-oxidation during laser cladding and may even be blown away by the gas flow; while powder with a particle size of 50 μm to 80 μm has better flowability and resistance to high-temperature oxidation, and can be smoothly fed into the molten pool. If the powder particle size is too large, the molten pool will not be able to completely melt the particles, thus leaving unfused pores in the coating.

[0035] In some embodiments, the thickness of the stainless steel coating is 50 μm to 150 μm, such as 80 μm, 100 μm or 120 μm. If the coating is too thin, it is not easy to completely cover the micro-defects on the substrate surface, which can easily form through-pores and reduce corrosion resistance; if the coating is too thick, residual tensile stress will accumulate during rapid cooling, which can easily lead to some micro-cracks in the coating.

[0036] In some embodiments, the particle size of the zirconium-based amorphous alloy powder is 50 μm to 100 μm. If the particle size of the zirconium-based amorphous alloy powder is too large, the powder will be difficult to melt fully in the plasma flame, resulting in a decrease in deposition rate or a rough coating surface; if the particle size of the zirconium-based amorphous alloy powder is too small, it will be easily oxidized in the high-temperature flame or blown away directly by the gas flow, resulting in material waste and a reduction in the amorphous phase content.

[0037] In some embodiments, the laser power used in the laser cladding process is 1kW to 2kW, the spot diameter is 2mm to 3mm, the scanning speed is 100m / min to 140m / min, the overlap rate is 30% to 50%, and the powder feeding rate is 20g / min to 30g / min.

[0038] Another embodiment of this disclosure provides a composite material coating, which is a composite material coating obtained according to any of the above preparation methods. In some embodiments, the composite material coating includes a stainless steel coating, a diffusion bonding layer, and a zirconium-based amorphous alloy layer stacked sequentially, wherein the thickness of the diffusion bonding layer is 1 μm to 5 μm, and the diffusion bonding layer contains an Fe-Zr intermetallic compound. In some embodiments, the amorphous phase content of the zirconium-based amorphous alloy layer is ≥90%, the Vickers hardness is 900 HV to 1200 HV, and the porosity is ≤0.5%.

[0039] This disclosure employs a gradient preheating and auxiliary cooling strategy in the laser cladding process to achieve a fine-grained structure in the stainless steel coating and reduce thermal stress. In the plasma spraying process, gradient spraying parameters are used to effectively control heat input and prevent crystallization of the zirconium-based amorphous alloy. The resulting composite coating comprises a sequentially stacked stainless steel layer, a diffusion bonding layer containing Fe-Zr intermetallic compounds, and a zirconium-based amorphous alloy layer, exhibiting high interfacial bonding strength. Through specific amorphous alloy component design and process synergistic optimization, this disclosure enables the composite coating to possess both the good toughness of stainless steel and the high hardness, high wear resistance, and excellent corrosion resistance of zirconium-based amorphous alloys. Using stainless steel as the transition layer material, compared to the aluminum alloy transition layer in existing technologies, stainless steel has higher strength, better thermal matching (similar to the thermal expansion coefficient of the steel substrate), and its excellent corrosion resistance ensures it will not become a "weak link" in the overall coating system. This disclosure addresses the low thermal conductivity of stainless steel by designing a combined strategy of gradient preheating and auxiliary cooling in the laser cladding process: gradient preheating reduces thermal stress and prevents cracking; auxiliary cooling promotes the formation of fine-grained / nanocrystalline structures, improving the mechanical properties of the stainless steel layer and its support capacity for the amorphous alloy layer. This disclosure specifies Zr... 63 Cu 20-x Al 10+x The Fe5Ti2 amorphous alloy composition system, in which the Cu / Al ratio is linked and controlled, optimizes the amorphous formation capability and hot working performance, providing a wider operating window for plasma spraying. This disclosure employs gradient spraying parameters in the plasma spraying process, precisely controlling the heat input through varying power and spraying distance, effectively avoiding amorphous alloy crystallization caused by heat accumulation, and ensuring that the amorphous phase content in the coating is ≥90%. The composite coating prepared in this disclosure forms an Fe-Zr intermetallic compound diffusion bonding layer at the interface, achieving metallurgical bonding with high interfacial bonding strength. The overall composite coating exhibits high hardness, low porosity, and excellent corrosion resistance.

[0040] The following description, in conjunction with specific embodiments, will provide a better understanding of this disclosure.

[0041] Example 1 This embodiment provides a method for preparing a corrosion-resistant zirconium-based amorphous alloy-stainless steel composite coating, the specific steps of which are as follows: (1) Matrix preparation The substrate material is Q235 carbon steel, with dimensions of 50mm×50mm×8mm. The substrate surface is successively polished with 240#, 400#, 800#, and 1200# sandpaper, then ultrasonically cleaned with acetone and anhydrous ethanol for 15 minutes each, and dried with cold air for later use.

[0042] (2) Laser cladding preparation of stainless steel layer The stainless steel powder used is 316L austenitic stainless steel powder with a particle size of 50-80μm and a chemical composition that conforms to GB / T20878-2007 standard.

[0043] Gradient preheating before laser cladding: Place the substrate in a vacuum chamber and evacuate to 1×10⁻⁶. -2 Pa was heated to 250°C at a heating rate of 10°C / min and held for 15 min; then heated to 450°C at a heating rate of 5°C / min and held for 15 min.

[0044] The laser cladding equipment uses a fiber laser (wavelength 1070nm, maximum output power 3kW) and is equipped with a coaxial powder feeding system. The process parameters are: laser power 1.5kW, spot diameter 2.5mm, scanning speed 120m / min, overlap rate 40%, and powder feeding rate 25g / min. Simultaneously with laser cladding, a high-pressure argon gas nozzle is used to assist in cooling the molten pool; the argon gas pressure is 0.5MPa, and the cooling rate is approximately 5×10³K / s.

[0045] The stainless steel layer formed after laser cladding is about 100 μm thick. Electron backscatter diffraction (EBSD) analysis shows that the average grain size of the stainless steel layer is 1.2 μm, exhibiting a fine-grained / nanocrystalline structure.

[0046] (3) Preparation of zirconium-based amorphous alloy powder The master alloy ingot (composition Zr) was prepared by vacuum arc melting combined with copper mold spraying. 63 Cu 16 Al 14 Fe5Ti2). High-purity metal raw materials (purity ≥ 99.9%) are weighed according to the formula and placed into a vacuum arc melting furnace, then evacuated to 5 × 10⁻⁶. -3 After Pa, the mixture was purged with high-purity argon gas for protection and repeatedly smelted four times to ensure uniform composition. The master alloy ingot was then crushed and pulverized using an air jet mill, and sieved to obtain amorphous alloy powder with a particle size of 50-100 μm. X-ray diffraction (XRD) confirmed that the powder was amorphous.

[0047] To further improve the oxidation resistance and spreading performance of the powder during spraying, the amorphous alloy powder was surface coated: the amorphous alloy powder was dispersed in a deionized aqueous solution containing 0.2 wt% sodium dodecylbenzenesulfonate and thoroughly ultrasonically dispersed. A quantitative yttrium nitrate solution was added, and the pH value of the system was slowly adjusted to 8-9 using dilute ammonia. The mixture was then placed in a 60℃ constant temperature water bath and stirred for 2 h to allow the yttrium hydroxide precursor to be uniformly deposited and coated on the surface of the amorphous powder. After the reaction, the mixture was filtered and thoroughly washed with deionized water and anhydrous ethanol in sequence, and then dried in a 70℃ oven. Subsequently, the powder was placed in a tube furnace and calcined at 350℃ for 2 h under an inert atmosphere, where the precursor was completely decomposed and converted into yttrium oxide. Finally, a composite powder with a uniform yttrium oxide coating was obtained, with the thickness of the yttrium oxide coating layer controlled at approximately 90 nm.

[0048] (4) Plasma spraying preparation of zirconium-based amorphous alloy layers The substrate with the 316L stainless steel layer prepared in step (2) was fixed on the spraying fixture by using an atmospheric plasma spraying system (APS).

[0049] The spraying process uses gradient parameters: for the first pass, the plasma output power is 13kW, the spraying distance is 110mm, the plasma gas source is Ar (65L / min) + H2 (8L / min), the powder feeding rate is 45g / min, and the spray gun moving speed is 850mm / s; for the second to fourth passes, the output power is reduced to 10kW, the spraying distance is shortened to 90mm, and other parameters remain unchanged.

[0050] After each coat was applied, a 5-minute interval was maintained during which the substrate was forcibly cooled with compressed air to approximately 350°C before the next coat was applied. A total of four coats were applied, with the total coating thickness controlled at approximately 225 μm. After coating, the substrate was cooled to room temperature in the furnace, yielding a zirconium-based amorphous alloy-stainless steel composite coating.

[0051] Example 2 The difference between this embodiment and Embodiment 1 is that x=0, that is, the general chemical formula of the zirconium-based amorphous alloy powder is Zr. 63 Cu 20 Al 10 For Fe5Ti2, other process parameters and operating steps are exactly the same as in Example 1.

[0052] Example 3 The difference between this embodiment and Embodiment 1 is that x=8, that is, the general chemical formula of zirconium-based amorphous alloy powder is Zr. 63 Cu 12 Al 18 For Fe5Ti2, other process parameters and operating steps are exactly the same as in Example 1.

[0053] Example 4 The difference between this embodiment and Embodiment 1 is that auxiliary cooling is not performed in the laser cladding process (i.e., high-pressure argon nozzles are not used to force cooling of the molten pool), while other process parameters and operating steps are exactly the same as in Embodiment 1.

[0054] Example 5 The difference between this embodiment and Embodiment 1 is that the plasma spraying process does not use gradient parameters, and all passes use the same output power (11kW) and spraying distance (100mm). Other process parameters and operating steps are exactly the same as in Embodiment 1.

[0055] Comparative Example 1 The difference between this comparative example and Example 1 is that gradient preheating is not performed during the preparation of the stainless steel layer (i.e., the substrate is directly laser clad without the preheating steps of 250°C and 450°C), while other process parameters and operating steps are exactly the same as in Example 1.

[0056] Comparative Example 2 The difference between this comparative example and Example 1 is that the zirconium-based amorphous alloy powder was not surface-coated; that is, Zr without a yttrium oxide coating was used directly. 63 Cu 16 Al 14 Fe5Ti2 powder was plasma sprayed, and other process parameters and operating steps were exactly the same as in Example 1.

[0057] Comparative Example 3 The difference between this comparative example and Example 1 is that the zirconium-based amorphous alloy powder uses components commonly found in existing technologies, specifically Zr. 55 Cu 30 Al 10 Ni5 (excluding Fe and Ti elements), without variable adjustment of the x value, and other process parameters and operating steps are exactly the same as in Example 1.

[0058] Comparative Example 4 The difference between this comparative example and Example 1 is that an aluminum alloy layer (AlNiY alloy, Al accounts for 60wt%, Ni accounts for 20wt%, and Y accounts for 20wt%) is used instead of a stainless steel layer as a transition layer. Other process parameters and operating steps are the same as in Example 1. (It should be noted that, due to the low melting point of aluminum alloy, the laser cladding parameters have been adapted: the laser power is reduced to 0.8kW, the scanning speed is reduced to 60m / min, and the preheating temperature is reduced to 150℃ and 250℃.)

[0059] Comparative Example 5 The difference between this comparative example and Example 1 is that the gradient preheating, auxiliary cooling, powder coating treatment and gradient spraying parameters are omitted (i.e., the most basic process scheme is adopted: no preheating, no auxiliary cooling, no powder coating, single-parameter spraying (all passes use the same output power (11kW) and spraying distance (100mm)), while other process parameters and operating steps are exactly the same as in Example 1.

[0060] All the above embodiments and comparative examples used the same testing standards: Hardness test: Vickers hardness tester was used, according to GB / T 4340.1-2009 standard, with a load of 200gf and a holding time of 15s. Ten points were tested for each sample and the average value was taken.

[0061] Bond strength test: According to ASTM C633-13 standard, the tensile test of the dual specimen was used with a universal testing machine at a loading rate of 1 mm / min. The maximum load on which the coating peeled off from the substrate was recorded, and the bond strength was calculated.

[0062] Amorphous phase content determination: The content of amorphous phase was calculated by X-ray diffraction (XRD) combined with the Rietveld full-spectrum fitting method.

[0063] Porosity determination: Image analysis was used to binarize the SEM images of the coating cross-section (EBSD function images of SEM) (magnification of 500×, 10 fields of view were randomly selected) and calculate the average value of the pore area ratio.

[0064] Corrosion resistance testing: An electrochemical workstation was used. The test sample was a coated specimen with an exposed area of ​​1 cm². The electrolyte was a 3.5 wt% NaCl aqueous solution (simulating a seawater environment). The reference electrode was a saturated calomel electrode (SCE), and the counter electrode was a platinum electrode. The open circuit potential (OCP) was first tested for 30 minutes until it stabilized. Then, potentiodynamic polarization curves were tested within the range of -0.5 V to +1.0 V (vs SCE) at a scan rate of 1 mV / s. The self-corrosion potential (Ecorr) and self-corrosion current density (Icorr) were calculated using the Tafel extrapolation method.

[0065] Grain size determination: The grain size of the stainless steel layer was statistically analyzed using the electron backscatter diffraction (EBSD) function of a scanning electron microscope (SEM). Additionally, the presence or absence of the Fe-Zr phase at the interface was determined using the electron backscatter diffraction (EBSD) function of a scanning electron microscope (SEM).

[0066] Tables 1 and 2 show the test results of various properties of the composite material coatings prepared in Examples 1 to 5 and Comparative Examples 1 to 5.

[0067] Table 1 Table 2 By comparing Examples 1 to 3 with Comparative Example 3, it can be seen that the Zr specified in this disclosure is used... 63 Cu 20-x Al 10+ x The composite coating prepared using the Fe5Ti2 system exhibited a significantly higher amorphous phase content (90.8-94.2%) than Comparative Example 3 (85.2%), along with a higher self-corrosion potential (-0.35~-0.41V vs -0.55V) and lower corrosion current density (0.85-1.24 μA / cm² vs 3.86 μA / cm²). This indicates that the introduction of Fe and Ti elements significantly improved the corrosion resistance of the amorphous alloy. Meanwhile, no Fe-Zr intermetallic compounds were detected at the interface of Comparative Example 3, suggesting that the interfacial reactivity between the Fe-free zirconium-based amorphous alloy and the stainless steel layer is low, which is unfavorable for forming a high-strength metallurgical bond. Regarding the optimal x value, Example 1 (x=4) showed the best overall performance, with the highest amorphous phase content (94.2%), the highest hardness (1085HV), and the lowest corrosion current density (0.85μA / cm²).

[0068] Comparing Example 1 and Comparative Example 1, it is evident that Comparative Example 1, without gradient preheating, exhibits significantly coarsened stainless steel layer grain size (8.5 μm vs 1.2 μm) and a substantial decrease in bonding strength (48.5 MPa vs 68.5 MPa). The high thermal stress generated by laser cladding without preheating leads to microcracks within the stainless steel layer. Furthermore, the grain coarsening reduces the inherent strength of the stainless steel layer, thus affecting the overall coating bonding performance. In addition, the discontinuous distribution of Fe-Zr intermetallic compounds at the interface of Comparative Example 1 further demonstrates that favorable preheating conditions promote interfacial atomic diffusion and metallurgical bonding.

[0069] Comparing Example 1 and Comparative Example 2, it can be seen that Comparative Example 2, which did not coat the amorphous alloy powder with yttrium oxide, showed a decrease in amorphous phase content (88.3%), an increase in porosity (0.68%), and an increase in corrosion current density of nearly 1.5 times. This is because the uncoated powder crystallized in the high-temperature plasma flame, and the precipitated crystalline phase reduced the density and corrosion resistance of the coating.

[0070] A comparison of Examples 1 and 5 shows that in Example 5, using uniform spraying parameters (without gradient adjustment), the amorphous phase content decreased to 87.6%, and the bonding strength decreased to 55.6 MPa. This is because subsequent spraying passes generated excessive thermal shock to the deposited amorphous layer, causing crystallization in some areas, while the accumulation of thermal stress affected the interfacial bonding. This comparison verifies the necessity of gradient spraying parameters for maintaining the amorphous structure and controlling thermal stress.

[0071] Comparing Examples 1 and 4, it can be seen that in Example 4, without auxiliary cooling, the grain size of the stainless steel layer coarsens from 1.2 μm to 3.8 μm, and other performance indicators also decreased to some extent, but overall it was still better than most comparative examples. This indicates that auxiliary cooling helps to obtain a finer stainless steel microstructure, but it is not the key factor determining the success or failure of the coating.

[0072] A comparison of Example 1 and Comparative Example 4 reveals that Comparative Example 4, which uses an aluminum alloy as the transition layer, employs the same preferred processes as this disclosure, including gradient preheating, auxiliary cooling, powder coating, and gradient spraying. However, the hardness of the composite coating (890 HV) is significantly lower than that of Example 1 (1085 HV). This is because the aluminum alloy transition layer itself has low hardness and cannot provide sufficient rigid support for the outer zirconium-based amorphous alloy during hardness testing, resulting in poor overall hardness performance of the composite coating. Furthermore, the aluminum alloy transition layer is prone to softening and oxidation under the high-temperature environment of plasma spraying, which also affects the deposition quality of the amorphous alloy layer.

[0073] By comparing Example 1 with Comparative Example 5, it can be seen that Comparative Example 5 lacks all key process steps such as gradient preheating, auxiliary cooling, powder coating and gradient spraying. As a result, all performance indicators deteriorate: the amorphous phase content is only 76.5%, the porosity is as high as 1.25%, the bonding strength is only 35.2 MPa, and the corrosion current density is as high as 8.52 μA / cm².

[0074] Figure 2 The images show the X-ray diffraction patterns of the composite material coatings from Examples 1, 4, 5, and Comparative Example 5. It should be understood that... Figure 2 These are merely representative examples; X-ray diffraction patterns corresponding to other embodiments and comparative examples can be obtained by referring to the above method. The XRD pattern of Example 1 shows only a characteristic amorphous peak between 2θ=30°-40°, without any other sharp crystalline diffraction peaks, indicating that in the composite coating prepared in this disclosure, the zirconium-based amorphous alloy layer maintains a complete amorphous structure, with an amorphous phase content of 94.2% (see Table 1).

[0075] The XRD pattern of Example 4 still shows predominantly amorphous peaks, with the appearance of Zr6FeAl2 crystalline peaks (amorphous phase content 93.5%, see Table 1). This change indicates that, without auxiliary cooling, the stainless steel layer remained at higher temperatures for a longer period during laser cladding, resulting in a certain degree of grain coarsening (from 1.2 μm to 3.8 μm, see Table 1). This grain coarsening weakens the quenching effect of the stainless steel layer on the subsequent plasma-sprayed molten droplets, leading to a slight decrease in the cooling rate of the amorphous alloy layer. Consequently, the short-range order of the amorphous structure is altered to some extent in the microstructure.

[0076] In Example 5, the XRD pattern showed an increase in the types of crystallization peaks and a greater relative peak value, while the amorphous phase content decreased to 87.6% (see Table 1). This change indicates that when uniform spraying parameters were used, the heat input in subsequent passes was not adaptively reduced, leading to repeated heating of the deposited layer. Local temperatures exceeded the glass transition temperature or even the crystallization transition temperature of the amorphous alloy, thus inducing the crystallization transformation of the amorphous phase. Furthermore, the continuous accumulation of heat on the stainless steel layer surface reduced the cooling rate at the interface, further promoting the formation of crystallized products. This result confirms that the gradient spraying parameter design of this invention is not a simple parameter selection, but a targeted solution based on a deep understanding of the low thermal conductivity and easy heat accumulation of stainless steel: using high power and a large spraying distance in the first pass facilitates sufficient powder melting and initial spreading, while reducing power and shortening the spraying distance in subsequent passes effectively avoids overheating and crystallization of the deposited layer.

[0077] In the XRD pattern of Comparative Example 5, the relative peak values ​​of the Zr6FeAl2 and TiZr crystallization peaks further increased, while the amorphous peaks gradually disappeared, and the amorphous phase content decreased to 76.5% (see Table 1). This change indicates that when all process measures such as gradient preheating, auxiliary cooling, powder coating, and gradient spraying are missing, the zirconium-based amorphous alloy undergoes severe crystallization during plasma spraying. The fundamental reason is the lack of auxiliary cooling and gradient spraying parameter control, resulting in excessive heat input and inability to dissipate heat in time. This causes the cooling rate of the molten droplets to be lower than the critical cooling rate of the zirconium-based amorphous alloy, thus leading to a crystallization transformation during deposition. This result strongly demonstrates the synergistic necessity of the various process measures of this invention for maintaining the amorphous structure.

[0078] Figures 3 to 5 The images show the electron backscattering diffraction (EBSD) patterns of the stainless steel layers in Examples 1, 4, and 1, respectively. It should be understood that... Figures 3 to 5 This is merely representative; the above method can be used to obtain EBSD diagrams corresponding to other embodiments and comparative examples. Figure 3As can be seen, the stainless steel layer prepared using the combined process of gradient preheating and auxiliary cooling has relatively fine grains, with an average grain size of 1.2 μm (see Table 1). This fine-grained structure is beneficial for improving the strength and toughness of the stainless steel layer itself, while also providing a smooth and dense substrate surface for the subsequent deposition of the amorphous alloy layer. Figure 4 As can be seen, without auxiliary cooling, the grain size of the stainless steel layer significantly coarsens, with the average grain size increasing to 3.8 μm (see Table 1). Figure 5 As can be seen, without gradient preheating, the grain size of the stainless steel layer coarsens drastically to 8.5 μm (see Table 1), and the grain size distribution is extremely uneven, with abnormally large grains appearing in some areas. Analysis suggests that without preheating, a large temperature gradient exists between the substrate and the cladding layer. After the molten pool solidifies in a very short time, the subsequent heat accumulation leads to tempering and grain growth in the solidified areas. The coarse and uneven grain structure severely degrades the mechanical properties of the stainless steel layer, which is highly consistent with the result of a bond strength of only 48.5 MPa in Comparative Example 1 in Table 1.

[0079] Therefore, the Zr disclosed herein 63 Cu 20-x Al 10+x Fe5Ti2-based amorphous alloy components (especially when x=4) possess excellent amorphous forming ability and corrosion resistance, making them ideal materials for preparing high-performance composite coatings. The synergistic effect of gradient preheating and auxiliary cooling during laser cladding yields a fine-grained / nanocrystalline stainless steel layer, providing a good substrate for subsequent deposition of the amorphous alloy layer. Oxide coating of the amorphous alloy powder effectively inhibits oxidation during spraying, reduces porosity, and improves the coating's density and corrosion resistance. Plasma spraying, employing gradient parameters (variable power, variable spraying distance), precisely controls the heat input, effectively preventing crystallization of the amorphous alloy and ensuring a high amorphous phase content. When these process measures are applied in combination, a continuous and dense Fe-Zr intermetallic compound diffusion bonding layer can be formed between the stainless steel layer and the amorphous alloy layer, achieving interfacial metallurgical bonding and significantly improving the mechanical properties and service reliability of the composite coating.

[0080] Example embodiments have been disclosed herein, and while specific terminology has been used, it is for illustrative purposes only and should be construed as such, and is not intended to be limiting. In some instances, it will be apparent to those skilled in the art that features, characteristics, and / or elements described in connection with particular embodiments may be used alone, or in combination with features, characteristics, and / or elements described in connection with other embodiments, unless otherwise expressly indicated. Therefore, those skilled in the art will understand that various changes in form and detail may be made without departing from the scope of this disclosure as set forth by the appended claims.

Claims

1. A method for preparing a composite material coating, characterized in that, include: Gradient preheating of the matrix and stainless steel powder; Using the aforementioned stainless steel powder, a stainless steel coating is formed on the surface of the substrate through a laser cladding process; Zirconium-based amorphous alloy powder is used to form a zirconium-based amorphous alloy layer on the surface of the stainless steel coating through a plasma spraying process. The general chemical formula of the zirconium-based amorphous alloy powder is Zr. 63 Cu 20-x Al 10+x Fe5Ti2, wherein 0≤x≤8; the surface of the zirconium-based amorphous alloy powder is coated with a transition metal oxide layer.

2. The preparation method according to claim 1, characterized in that, The gradient preheating includes a first preheating stage and a second preheating stage. The temperature of the first preheating stage is 200°C to 300°C, and the holding time is 10 min to 20 min. The temperature of the second preheating stage is 400°C to 500°C, and the holding time is 10 min to 20 min.

3. The preparation method according to claim 1, characterized in that, During the laser cladding process, auxiliary cooling is applied to the molten pool at a cooling rate of 10² K / s to 10 4 K / s.

4. The preparation method according to claim 3, characterized in that, The auxiliary cooling is performed using inert gas or a circulating cooling medium.

5. The preparation method according to claim 1, characterized in that, The thickness of the transition metal oxide layer is 50 nm to 150 nm; and / or The transition metal oxide layer includes at least one of yttrium oxide, cerium oxide, or zirconium oxide.

6. The preparation method according to claim 1, characterized in that, The plasma spraying process employs gradient spraying parameters: the plasma output power of the first spraying pass is 12kW to 15kW, and the spraying distance is 100mm to 120mm; the plasma output power of the second and subsequent spraying passes is 8kW to 11kW, and the spraying distance is 80mm to 95mm.

7. The preparation method according to claim 6, characterized in that, The plasma spraying process consists of 3 to 6 spraying passes, with an interval of 3 to 8 minutes between adjacent spraying passes. During the interval, the substrate is cooled to 300°C to 400°C.

8. The preparation method according to any one of claims 1 to 7, characterized in that, Meet at least one of the following: The matrix includes carbon steel, alloy steel, or cast iron; The stainless steel powder includes austenitic stainless steel; The particle size of the stainless steel powder is 50 μm to 80 μm; The thickness of the stainless steel coating is 50 μm to 150 μm; The zirconium-based amorphous alloy powder has a particle size of 50 μm to 100 μm; The zirconium-based amorphous alloy powder is Zr. 63 Cu 16 Al 14 Fe5Ti2; The laser cladding process uses a laser power of 1kW to 2kW, a spot diameter of 2mm to 3mm, a scanning speed of 100m / min to 140m / min, an overlap rate of 30% to 50%, and a powder feeding rate of 20g / min to 30g / min.

9. A composite material coating, characterized in that, The composite material coating is a composite material coating obtained by the preparation method according to any one of claims 1 to 8.

10. The composite material coating according to claim 9, characterized in that, The composite material coating comprises a stainless steel coating, a diffusion bonding layer, and a zirconium-based amorphous alloy layer stacked sequentially. The thickness of the diffusion bonding layer is 1 μm to 5 μm, and the diffusion bonding layer contains an Fe-Zr intermetallic compound; and / or The zirconium-based amorphous alloy layer has an amorphous phase content of ≥90%, a Vickers hardness of 900 HV to 1200 HV, and a porosity of ≤0.5%.

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