Iron-based amorphous alloy low-porosity coating and preparation method and application thereof

Abstract

The invention belongs to the technical field of surface functional coatings, and particularly relates to an iron-based amorphous alloy low-porosity coating and a preparation method and application thereof. According to the method, the coating is prepared by adopting supersonic flame spraying, the supersonic flame has the characteristics of high temperature and high-speed combustion flame flow, powder is axially fed into the flame, sprayed particles can be heated to a molten or semi-molten state and can be accelerated to the speed up to 300 m / s or above, and dynamic mechanical embedding and micro-area metallurgical combination are achieved; and through orthogonal matching of the spraying distance, the powder feeding rate and the gas pressure, amorphous phase change is inhibited, interlayer densification is guaranteed, and therefore the high-quality coating high in bonding strength and compact is obtained. The high velocity oxy-fuel is very high in speed, but the temperature is relatively low, for WC-Co series hard alloy, decomposition of WC in the spraying process can be effectively restrained, and the coating is high in bonding strength, compact and excellent in wear resistance.

Description

Technical Field

[0001] This invention belongs to the field of surface functional coating technology, specifically relating to a low-porosity coating for iron-based amorphous alloys, its preparation method, and its application. Background Technology

[0002] Current metal surface protection technologies face multiple bottlenecks: traditional electroplated hard chromium layers have a bonding strength of less than 30 MPa due to hydrogen embrittlement, and the columnar crystal structure results in a porosity of >5%, which causes substrate corrosion after 96 hours of salt spraying. Furthermore, the hexavalent chromium process violates environmental regulations. Although conventional thermal spraying technology can improve the bonding strength to 40~50 MPa (short transverse specification), the high-temperature flame flow causes iron-based amorphous phase transformation and WC-Co carbide decomposition, and the porosity is >2%, making it difficult to resist electrochemical-mechanical coupling damage and thermal shock stress in marine equipment.

[0003] While existing improved processes such as laser cladding achieve metallurgical bonding, the high heat input causes the substrate to soften and reduces corrosion resistance by 60%, failing to meet the synergistic requirements of deep-sea high pressure, salt spray corrosion, and temperature shock. Therefore, there is an urgent need for a green coating material and its preparation technology that combines high-strength bonding, ultra-low porosity, and amorphous phase stability, overcoming the three major technical barriers of interface strengthening, phase transformation suppression, and thermal coupling tolerance. Summary of the Invention

[0004] The purpose of this invention is to provide a low-porosity coating for iron-based amorphous alloys, its preparation method, and its application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for preparing a low-porosity coating of an iron-based amorphous alloy, comprising the following steps: Iron-based amorphous alloys were prepared by a water-air combined atomization method. The oxygen content of the iron-based amorphous alloys did not exceed 1500 ppm, the amorphous content was not less than 95%, and the sphericity was not less than 95%. The iron-based amorphous alloy was sprayed onto the surface of a preheated substrate using supersonic flame spraying technology. After annealing, a low-porosity coating of the iron-based amorphous alloy was obtained.

[0006] Preferably, the chemical composition of the iron-based amorphous alloy is FeCoSiBPCu.

[0007] Preferably, the oxygen content of the iron-based amorphous alloy is 1000~1500ppm; The particle size D50 of the iron-based amorphous alloy is 15~55µm.

[0008] Preferably, the temperature of the preheated substrate is 80~120℃.

[0009] Preferably, the conditions of the supersonic flame spraying technology include: a powder feeding spraying distance of 150-200 mm, a gas pressure of 0.7-0.9 MPa, and a powder feeding rate of 30-50 g / min.

[0010] Preferably, the temperature of the annealing is not more than 180℃, and the holding time is 55-65 min.

[0011] Preferably, before the preheating, the method further comprises pre-treating the substrate, and the pre-treating comprises sequentially performing first water washing, alkali washing, second water washing, and drying.

[0012] Preferably, the thickness of the coating layer is 50-500 µm.

[0013] The application also provides an iron-based amorphous alloy low-porosity coating prepared by the preparation method.

[0014] The application also provides an application of the iron-based amorphous alloy low-porosity coating in marine equipment, petroleum machinery, and aerospace.

[0015] The application provides a preparation method of an iron-based amorphous alloy low-porosity coating, comprising the following steps: preparing an iron-based amorphous alloy by using a water-gas combined atomization method, wherein the oxygen content of the iron-based amorphous alloy is not more than 1500 ppm, the amorphous content is not less than 95%, and the sphericity is not less than 95%; and spraying the iron-based amorphous alloy on the surface of a preheated substrate by using a supersonic flame spraying technology, and obtaining the iron-based amorphous alloy low-porosity coating after annealing.

[0016] Compared with the prior art, the application has the following beneficial effects: (1) The iron-based amorphous alloy powder is prepared by using the water-gas combined atomization method, and has the characteristics of high strength, high hardness, and high wear resistance. Due to the unique atomic structure, the iron-based amorphous alloy powder can be sintered at a relatively low temperature, so that a highly dense high-performance product is obtained. The water-gas combined atomization method controls the amorphous content to be greater than or equal to 95% through inert gas protection and gradient cooling, and optimizes the bimodal distribution of particle size to reduce the porosity. The produced iron-based amorphous alloy has regular microstructure, low oxygen content, good formability, stable process performance, no pollution, low cost, and meets the environmental protection requirements, and the production cost is reduced.

[0017] (2) the present application adopts the supersonic flame spraying to prepare the coating, the supersonic flame is high-temperature, high-speed combustion flame flow generated by using propane, propylene and other hydrocarbon gas or hydrogen and high-pressure oxygen in the combustion chamber, or in the special nozzle, the combustion flame flow speed can reach 5 Mach (1500 m / s) or more. The powder is axially sent into the flame, the sprayed particles can be heated to the molten or semi-molten state, and accelerated to a speed of 300-500 m / s or even higher, realizing dynamic mechanical embedding and micro-zone metallurgy; by orthogonal matching spraying distance, powder feeding rate and gas pressure, amorphous phase change is inhibited and interlayer densification is ensured, so that the coating with high bonding strength and high density is obtained. The supersonic flame speed is very high, but the temperature is relatively low, for WC-Co hard alloy, the decomposition of WC in the spraying process can be effectively inhibited, the coating not only has high bonding strength, but also is dense, and has excellent wear resistance, the wear resistance is much higher than that of the plasma sprayed layer, and also higher than that of the electroplated hard chromium layer and the sprayed layer, and is widely applied. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The SEM image of the cross section of the low-porosity iron-based amorphous alloy coating obtained in Example 1. DETAILED DESCRIPTION

[0019] The present application provides a preparation method of a low-porosity iron-based amorphous alloy coating, comprising the following steps: An iron-based amorphous alloy is prepared by a water-gas combined atomization method; the oxygen content of the iron-based amorphous alloy is not more than 1500 ppm, the amorphous content is not less than 95%, and the sphericity is not less than 95%; The iron-based amorphous alloy is sprayed on the surface of a preheated substrate by using a supersonic flame spraying technology, and the low-porosity iron-based amorphous alloy coating is obtained after annealing.

[0020] The present application adopts a water-gas combined atomization method to prepare an iron-based amorphous alloy.

[0021] In the present application, the conditions of the water-gas combined atomization method preferably include: high-speed high-pressure water and high-speed argon gas are used, the jet pressure of the high-speed high-pressure water is 120-130 MPa, and the flow rate is 20-22 L / min; the pressure of the high-speed argon gas is 1-1.1 MPa, and the speed is 2.5-2.8 cm 3 / min.

[0022] In this invention, the oxygen content of the iron-based amorphous alloy is no more than 1500 ppm, preferably 1000~1500 ppm, specifically 1000 ppm, 1100 ppm, 1200 ppm, 1300 ppm, 1400 ppm, or 1500 ppm; the particle size D50 of the iron-based amorphous alloy is preferably 15~55 µm, specifically 15 µm, 20 µm, 25 µm, 30 µm, 35 µm, 40 µm, 45 µm, 50 µm, or 55 µm.

[0023] In this invention, the preferred chemical composition of the iron-based amorphous alloy is FeCoSiBPCu.

[0024] After obtaining the iron-based amorphous alloy, the present invention uses supersonic flame spraying technology to spray the iron-based amorphous alloy onto the surface of a preheated substrate. After annealing, a low-porosity coating of the iron-based amorphous alloy is obtained.

[0025] In this invention, the substrate is preferably 30CrMnSiA alloy steel.

[0026] In this invention, before preheating, the substrate is further pretreated. The pretreatment includes sequentially performing a first water wash, an alkaline wash, a second water wash, and drying. The first and second water washes are preferably performed independently using deionized water. The first water wash removes surface dust and impurities, while the second water wash removes residual alkaline cleaning agent. The alkaline cleaning agent used in the alkaline wash preferably includes a sodium hydroxide solution, with a concentration preferably of 6-8 wt%. In this invention, alkaline washing introduces an alkaline electrolytic activation process, generating a nanoscale oxide layer on the surface, enhancing chemical bonding activity, and replacing the mechanical damage caused by traditional sandblasting.

[0027] In this invention, the temperature of the preheated substrate is preferably 80~120℃, specifically 80℃, 90℃, 100℃, 110℃, or 120℃. In this invention, the preheating is preferably performed using a supersonic flame torch.

[0028] In this invention, the preferred conditions for the supersonic flame spraying technology include: a powder feeding and spraying distance of 150-200 mm, specifically 150 mm, 160 mm, 170 mm, 180 mm, 190 mm, or 200 mm; a gas pressure of 0.7-0.9 MPa, specifically 0.7 MPa, 0.8 MPa, or 0.9 MPa; and a powder feeding rate of 30-50 g / min, specifically 30 g / min, 40 g / min, or 50 g / min. This invention does not impose any special limitations on the specific process of the supersonic flame spraying technology; any process well-known to those skilled in the art can be used.

[0029] In the present application, the annealing temperature is preferably no more than 180℃, and can be 160℃ in particular; and the holding time is preferably 1h. In the present application, short-time annealing below the amorphous alloy glass transition temperature triggers atomic short-range relaxation to eliminate internal stress, promotes the gradient diffusion of Co and B elements to the matrix, forms a transition interface layer, and improves the bonding strength by 15% and significantly enhances the thermal shock stability, so as to finally realize the synergistic performance of high strength and toughness, low porosity and long-acting weather resistance of the coating.

[0030] In the present application, the thickness of the coating is preferably 50-500µm.

[0031] The present application also provides an iron-based amorphous alloy low-porosity coating prepared by the preparation method described in the above technical solution, wherein the porosity of the iron-based amorphous alloy low-porosity coating is preferably less than 1%.

[0032] The iron-based amorphous alloy low-porosity coating provided by the present application has a neutral salt spray corrosion resistance of >3000h.

[0033] The present application also provides the application of the iron-based amorphous alloy low-porosity coating described in the above technical solution in marine equipment, petroleum machinery and aerospace.

[0034] Unless otherwise specified, the materials and equipment used in the present application are commercially available in the art.

[0035] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0036] Embodiment 1 30CrMnSiA alloy steel was used as the base material, the base material was preliminarily cleaned with deionized water, then deoiled with an alkaline cleaning agent (specifically, a sodium hydroxide solution with a concentration of 6%), and then washed with deionized water and dried to obtain a pretreated base material; An iron-based amorphous alloy was prepared by a water-gas combined atomization method, wherein the conditions of the water-gas combined atomization method include: high-speed high-pressure water and high-speed argon gas, the jetting pressure of the high-speed high-pressure water is 130MPa, and the flow rate is 22L / min; the pressure of the high-speed argon gas is 1MPa, and the speed is 2.5cm 3 / min; the D50 of the obtained iron-based amorphous alloy is 20µm, the oxygen content is 1200ppm, the sphericity is 95%, and the amorphous content is 96%; The base material was preheated by an ultrasonic speed flame spray gun, and the preheating temperature was 80℃. Using supersonic flame spraying technology, the iron-based amorphous alloy obtained above was sprayed onto the surface of a pretreated substrate. The spraying process was as follows: the powder feeding distance was 150 mm, the gas pressure was 0.8 MPa, the powder feeding rate was 50 g / min, and the thickness was 50 µm. After spraying, the coating was annealed at 160 °C for 1 h to obtain a low-porosity iron-based amorphous alloy coating.

[0037] Example 2 Using 30CrMnSiA alloy steel as the substrate, the substrate is initially cleaned with deionized water, then degreased with an alkaline cleaning agent (specifically, a 6% sodium hydroxide solution), followed by deionized water washing and drying to obtain the pretreated substrate. Iron-based amorphous alloys were prepared using a water-gas combined atomization method. The conditions for this method included: the use of high-speed, high-pressure water and high-speed argon gas. The high-speed, high-pressure water was injected at a pressure of 120 MPa with a flow rate of 20 L / min, and the high-speed argon gas was injected at a pressure of 1 MPa with a velocity of 2.5 cm⁻¹. 3 / min; the obtained iron-based amorphous alloy has a D50 of 52µm, an oxygen content of 1200ppm, a sphericity of 98%, and an amorphous content of 99%; The substrate is preheated using a supersonic flame torch at a temperature of 120°C. Using supersonic flame spraying technology, the iron-based amorphous alloy obtained above was sprayed onto the surface of a pretreated substrate. The spraying process was as follows: the powder feeding distance was 200 mm, the gas pressure was 0.8 MPa, the powder feeding rate was 30 g / min, and the thickness was 50 µm. After spraying, the coating was annealed at 160 °C for 1 h to obtain a low-porosity iron-based amorphous alloy coating.

[0038] Comparative Example 1 A low-porosity iron-based amorphous alloy coating was prepared according to Example 1, wherein the high-speed argon gas had a pressure of 0.6 MPa and a velocity of 2 cm⁻¹. 3 The oxygen content of the obtained iron-based amorphous alloy was 2000 ppm at a rate of 1000 ppm / min.

[0039] Comparative Example 2 A low-porosity iron-based amorphous alloy coating was prepared according to Example 1, wherein the high-pressure water jet pressure was 30 MPa and the flow rate was 12 L / min, and the resulting iron-based amorphous alloy had a D50 of 60~65 µm.

[0040] Comparative Example 3 A low-porosity iron-based amorphous alloy coating was prepared according to Example 1, wherein the high-pressure water jet pressure was 150 MPa and the flow rate was 25 L / min, and the resulting iron-based amorphous alloy had a D50 of less than 12 µm.

[0041] Comparative Example 4 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that the substrate was not pretreated.

[0042] Comparative Example 5 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that the substrate was not preheated.

[0043] Comparative Example 6 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that no annealing was performed after spraying.

[0044] Comparative Example 7 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that the powder feeding rate was 60 g / min.

[0045] Comparative Example 8 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that the spraying material was adjusted to spherical cobalt powder with a purity of cobalt ≥ 99%.

[0046] Comparative Example 9 An iron-based amorphous alloy low porosity coating was prepared in the same manner as in Example 1, except that the spraying material was adjusted to spherical nickel powder with a purity of nickel ≥ 99%.

[0047] Performance test Figure 1 A cross-sectional SEM image of the iron-based amorphous alloy low porosity coating obtained in Example 1 was taken, from which Figure 1 It can be seen that the substrate and the coating are well combined.

[0048] The coatings obtained in the examples and comparative examples were tested for performance; the test results are shown in Table 1; The bonding strength was tested by compression shear method; The salt spray test used a neutral salt spray test: in the test chamber, a salt water containing (5 ± 0.5)% sodium chloride, pH 7.2, was sprayed by a spraying device, and the salt mist was allowed to settle on the test sample, and after a certain time, the surface corrosion state was observed. The temperature requirement of the test chamber is 35 ± 2℃, the humidity is greater than 95%, the mist amount is 1~2mL / (h·cm 2 ), and the nozzle pressure is 137.3kPa. Whether the sample has corrosion spots was observed; The porosity of the sample was tested by the principle of weighing method, according to the weight change of the material before and after being soaked in alcohol, to determine the pore volume of the material. ρ=v1 / (v1+v2),v1 is the pore volume of the material, and v2 is the volume of the material; Thermal shock test: the sample is heated to 350℃ for 1h, then put into water to cool down, repeat this action 50 times, to observe the coating peeling area.

[0049] Table 1 coating performance test results of examples and comparative examples

[0050] From the above data, it can be seen that the coating strength and corrosion resistance can be greatly improved by using the present application.

[0051] Specifically: (1) The coating bonding strength and compactness are significantly improved. Through the synergistic effect of supersonic flame spraying and substrate preheating, the bonding strength reaches 67~70MPa, which is more than 2 times higher than that of traditional chrome plating layer; the porosity is <1%, realizing the physical isolation effect on the corrosion medium.

[0052] (2) The extreme environment resistance performance is broken through. The atomic disordered structure of amorphous alloy gives the coating high chemical homogeneity, the neutral salt spray corrosion resistance time is >3000h, which is 33 times that of traditional chrome plating layer; the friction coefficient is <0.05, the wear resistance is 5 times that of 30Cr steel, which meets the needs of deep sea high pressure, high salt spray and other harsh working conditions.

[0053] (3) The process environmental friendliness and substrate compatibility are optimized. The oxygen content is controlled to be not more than 1500ppm in the water-gas combined atomization powdering process, which avoids the performance degradation caused by metal oxidation; the whole process temperature is <180℃, the heat affected zone depth is <50µm, realizing the micro-deformation processing of precision parts.

[0054] (4) The coating thermal shock resistance and service stability are enhanced. After 50 times of "350℃→water quenching thermal cycle" test, the coating has no peeling, while the traditional plasma sprayed layer has a peeling area of >5% under the same conditions, which shows that the coating of the present application has a significant advantage in the temperature change scene.

[0055] Although the above examples have made a detailed description of the present application, it is only a part of the embodiments of the present application, not all the embodiments, and other embodiments can be obtained according to the present embodiments without creativity, which all belong to the protection scope of the present application.

Claims

1. A method for preparing a low-porosity coating of an iron-based amorphous alloy, characterized in that, Includes the following steps: Iron-based amorphous alloys were prepared by a water-air combined atomization method. The oxygen content of the iron-based amorphous alloys did not exceed 1500 ppm, the amorphous content was not less than 95%, and the sphericity was not less than 95%. The iron-based amorphous alloy was sprayed onto the surface of a preheated substrate using supersonic flame spraying technology. After annealing, a low-porosity coating of the iron-based amorphous alloy was obtained.

2. The preparation method according to claim 1, characterized in that, The chemical composition of the iron-based amorphous alloy is FeCoSiBPCu.

3. The preparation method according to claim 1, characterized in that, The oxygen content of the iron-based amorphous alloy is 1000~1500ppm; The particle size D50 of the iron-based amorphous alloy is 15~55µm.

4. The preparation method according to claim 1, characterized in that, The temperature of the preheated substrate is 80~120℃.

5. The preparation method according to claim 1, characterized in that, The conditions for the supersonic flame spraying technology include: a powder feeding and spraying distance of 150~200mm, a gas pressure of 0.7~0.9MPa, and a powder feeding rate of 30~50g / min.

6. The preparation method according to claim 1, characterized in that, The annealing temperature shall not exceed 180°C, and the holding time shall be 55~65 minutes.

7. The preparation method according to claim 1, characterized in that, Before the preheating, the substrate is pretreated, which includes a first water wash, an alkaline wash, a second water wash, and drying.

8. The preparation method according to claim 1, characterized in that, The thickness of the coating is 50~500µm.

9. The iron-based amorphous alloy low-porosity coating prepared by the preparation method according to any one of claims 1 to 8, characterized in that, The porosity of the iron-based amorphous alloy low-porosity coating is less than 1%.

10. The application of the iron-based amorphous alloy low-porosity coating of claim 9 in marine equipment, petroleum machinery and aerospace.

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