A nickel-lanthanum oxide-nano-titanium dioxide composite coating and its preparation method and application

Abstract

The invention discloses a nickel-lanthanum oxide-nano-titania composite coating and a preparation method and application thereof. The preparation method comprises: using sodium polyphosphate as a dispersant and sodium carboxymethyl cellulose solution as a binder, mixing the dispersant with nano-titanium dioxide and deionized water, mechanically stirring, spraying and granulating the obtained slurry, heat-treating to obtain nano-titanium dioxide agglomerated powder, mixing the powder with metallic nickel powder and lanthanum oxide powder to obtain a mixed feed powder, and sequentially plasma-spraying a base layer and a composite coating on the surface of a substrate after sandblasting and dust removal to obtain the nickel-lanthanum oxide-nano-titania composite coating. The composite coating greatly enhances the density, toughness and corrosion resistance, solves the problem that nano-scale powders cannot be plasma-sprayed, and has great application potential in the marine field.

Description

Technical Field

[0001] The invention belongs to the field of material surface coating preparation, and particularly relates to a nickel-lanthanum oxide-nano titanium dioxide composite coating and a preparation method and application thereof. Background Art

[0002] As ocean exploration deepens, demands on marine equipment are also increasing. The marine environment is complex and features diverse corrosion types, including seawater corrosion and severe microbial corrosion. Research on protective measures against these challenges facing various marine engineering equipment is crucial. Coating protection technologies have been widely adopted in marine engineering, with thermal spray coatings and water-based organic coatings being the most commonly used. While water-based organic coatings offer advantages such as ease of use, they still suffer from challenges such as poor wear resistance, limited protective properties, a short protection lifespan, insufficient bonding capacity leading to flaking under high-pressure conditions, and controversial environmental performance. Some organic coatings contain hazardous substances, such as volatile organic compounds (VOCs), which can harm the marine environment. Thermal spray coatings, already widely used in the aerospace industry due to their excellent corrosion and wear resistance, high strength and hardness, can complement the shortcomings of water-based coatings in the marine sector. Thermal spray coatings offer sufficient surface hardness, a long protection lifespan, and are environmentally friendly. Furthermore, thermal spray technology boasts simple equipment, convenient operation, and strong adaptability, making it widely used in various applications. However, thermal spray coatings have disadvantages such as high porosity and poor toughness, which can easily lead to protection failure in complex marine environments.

[0003] Ceramics have the characteristics of wear resistance, corrosion resistance, high hardness, high temperature resistance, and good biocompatibility. They are good thermal spray coating materials for marine environments. Micron-level titanium dioxide thermal spray coatings have high bonding strength, moderate hardness, stable chemical properties, and strong corrosion resistance. They are a commonly used corrosion-resistant coating. Unlike other ceramic coatings, titanium dioxide also has good antibacterial properties and is often used as an additive to other coating systems to increase their antibacterial properties. However, micron titanium dioxide coatings also have disadvantages such as high porosity and poor toughness. Based on this, the present invention is proposed to prepare a dense, low-porosity, high-toughness and corrosion-resistant titanium dioxide-based composite coating. Summary of the Invention

[0004] However, to date, there have been no relevant patents or literature reports on the preparation of nickel-lanthanum oxide-titanium dioxide nanocomposite thermal spray powders and coatings for use in the marine field. In response to the shortcomings of the existing micron titanium dioxide coatings in the marine field, the main purpose of the present invention is to provide a method for preparing a nickel-lanthanum oxide-nano titanium dioxide composite coating. Nano-titanium dioxide is agglomerated using spray granulation technology to achieve a suitable size for plasma spraying, and then co-deposited on the substrate surface with metallic nickel and lanthanum oxide to prepare a nickel-lanthanum oxide-nano titanium dioxide composite coating. This process can effectively improve the density, toughness and corrosion resistance of the coating.

[0005] The present invention adopts three toughening methods combined: first, metal particles are introduced into the ceramic. The metal phase can effectively prevent the movement of cracks, and by preventing them from breaking, the toughness and wear resistance of the coating are increased, thereby extending the service life. Nickel has strong corrosion resistance and can prevent rust when plated on other metals. It is also a common corrosion-resistant metal. Second, rare earth oxide toughening has a good effect. After adding an appropriate amount of rare earth oxide, the porosity and pore size in the ceramic coating can be reduced, and the stress concentration of the internal stress of the coating at the edge of the pores is reduced, thereby improving the bonding strength and toughness of the coating. Third, nanotechnology toughening is an effective toughening method. Due to the refinement of the grains of nanoceramics, the number of grain boundaries is greatly increased. At the same time, the porosity of the nanoceramic coating is lower, making the coating more dense, thereby achieving an increase in strength and toughness.

[0006] Another object of the present invention is to provide a nickel-lanthanum oxide-nano-titanium dioxide composite coating, which is prepared by the above preparation method.

[0007] Another object of the present invention is to provide the application of the nickel-lanthanum oxide-nano-titanium dioxide composite coating in the protection of marine engineering equipment.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] The present invention provides a method for preparing a nickel-lanthanum oxide-nano-titanium dioxide composite coating, comprising the following steps:

[0010] Step 1: preparing nano titanium dioxide agglomerated powder, comprising:

[0011] (1) Preparation of dispersant and binder: Sodium polyphosphate is used as dispersant, sodium carboxymethyl cellulose solution is used as binder, the mass of the dispersant powder accounts for 1% to 2% of the mass of the nanopowder; the mass of the binder accounts for 50% of the mass of the nanopowder, wherein the mass ratio of sodium carboxymethyl cellulose powder to deionized water is 1.5:100. After weighing sodium carboxymethyl cellulose and deionized water according to the ratio, heat in a water bath at 90°C and stir for 2 hours;

[0012] (2) preparing a slurry: mixing the dispersant with nano-titanium dioxide and deionized water, mechanically stirring for 1 hour, adding the binder and ultrasonically shaking for 0.5 hours, and then mechanically stirring for 2 hours to obtain a slurry;

[0013] (3) spray granulation: the slurry is added to a spray granulation device for spray granulation to obtain a powder with a particle size of 10 to 100 μm, and heat treated at 800° C. to obtain nano-titanium dioxide agglomerated powder;

[0014] Step 2: Prepare nickel-lanthanum oxide-nano-titania composite powder: Place the nano-titania agglomerated powder, metallic nickel powder, and lanthanum oxide powder into a V-type powder mixer and mix them thoroughly for 24 hours to obtain nickel-lanthanum oxide-nano-titania mixed feeding powder, wherein the mass of nickel powder accounts for 10% to 30% of the total powder mass, and the mass of lanthanum oxide powder accounts for 3% to 9% of the total powder mass.

[0015] Step 3, preparing a nickel-lanthanum oxide-nano-titanium dioxide composite coating, comprising:

[0016] (a) Sandblasting: G25 crushed steel grit is used to pre-treat the substrate surface to obtain a certain degree of roughness;

[0017] (b) Dust removal: Use compressed air to remove dust from the surface of the substrate after sandblasting, and then use anhydrous ethanol to clean it under ultrasonic conditions to remove rust and stains on the surface of the material;

[0018] (c) Plasma spraying primer: spraying a primer layer on the surface of the dust-removed substrate, wherein the primer layer is made of nickel-chromium-aluminum-yttrium alloy;

[0019] (d) Plasma spraying composite coating: spraying composite coating on the substrate sprayed with the primer layer in step (c): spraying nickel-lanthanum oxide-nano-titanium dioxide composite coating on the substrate sprayed with the primer layer by plasma spraying.

[0020] Preferably, in step 2, the solid content of the slurry is 35% to 40%.

[0021] Preferably, in step 2, the spray granulation equipment adopts a centrifugal spray dryer model G1 PP-5000Y produced by Shanghai Shunzhi Instrument Manufacturing Co., Ltd., and sets the "induced draft" operating frequency to 35HZ according to the material specific gravity, the atomization operating frequency to 300HZ, the inlet air temperature to 220 degrees, the air hammer action time to 2 seconds, and the air hammer interval time to 15 seconds; before use, turn on the induced draft fan, turn on the electric heating, turn on the lighting, and pour the slurry to be dried into the barrel; when the inlet air temperature reaches the required set temperature, start the peristaltic pump on the touch screen, adjust the speed to 10 rpm, start the atomization on the touch screen, and rotate the atomizer nozzle. When the speed is normal, let the atomizer spray water for a period of time so that the outlet air temperature reaches the predetermined exhaust air temperature of 100°C, and then quickly convert it into the liquid in the mixing barrel. The liquid is steplessly adjusted by the Mono pump, gradually increasing from small to large.

[0022] Preferably, in step c, the material of the base layer is nickel-chromium-aluminum-yttrium alloy, the powder particle size is 45 to 120 μm, and the thickness of the base layer is 80 to 120 μm.

[0023] Preferably, in step d, the thickness of the nickel-lanthanum oxide-nano-titanium dioxide composite coating is 300 to 500 μm.

[0024] Preferably, in steps c and d, a GP-80 plasma spraying device is used, the flow rate of argon is 80 L / h, and the flow rate of hydrogen is 100 L / h; at the same time, a BF-02 ultrafine powder feeder is used, the powder feeding amount is 20 g / min, a handheld gun and external powder feeding method are used, the spraying power is 35 kW (500 A × 64 V), and the gun distance is 100 mm.

[0025] The present invention also provides a nickel-lanthanum oxide-nano titanium dioxide composite coating, which is prepared by the above preparation method and comprises 10%-30% Ni, 3%-9% La2O3 and 61%-87% TiO2, and has a thickness of 300-500 μm.

[0026] The present invention also provides application of the nickel-lanthanum oxide-nano-titanium dioxide composite coating in protection of marine engineering equipment.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention utilizes spray granulation technology to agglomerate nano-titanium dioxide, thus solving the problem that nano-scale powder cannot be plasma sprayed.

[0029] 2. The nickel-lanthanum oxide-nano-titanium dioxide composite coating prepared by the present invention is greatly improved compared with the traditional micron titanium dioxide coating: it has lower porosity, reduced from 7.60% to 2.08%; higher fracture toughness, from 2.7Mpa·m1 / 2 Increased to 3.9Mpa·m 1 / 2 The corrosion resistance is better. According to the Tafel fitting analysis of the polarization curve, the corrosion potential (Ecorr) in artificial seawater is increased from -678mV to -459mV, and the corrosion current density (Icorr) is increased from 69.2×10 - 6 A / cm 2 Reduced to 17.7×10 -6 A / cm 2 The corrosion rate is 803.1×10 -3 mmpy decreased to 205.1×10 -3 mmpy; in sulfate-reducing bacteria (SRB) solution, the self-corrosion potential (Ecorr) increased from -486 mV to -40.1 mV, and the self-corrosion current density (Icorr) increased from 59.60×10 -6 A / cm 2 Reduced to 6.68×10 -6 A / cm 2 The corrosion rate is 691.91×10 -3 mmpy decreased to 77.60×10 -3 mmpy, greatly enhancing density, toughness and corrosion resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a picture of the nano-titanium dioxide agglomerated powder prepared in Example 1.

[0031] Figure 2 This is a surface morphology of the nickel-lanthanum oxide-nano-titanium dioxide composite coating prepared in Example 2; (a) low magnification; (b) high magnification.

[0032] Figure 3 This is a cross-sectional porosity diagram of the nickel-lanthanum oxide-nano-titanium dioxide composite coating prepared in Example 3; (a) coating cross section; (b) porosity schematic diagram.

[0033] Figure 4 This is a polarization curve diagram of the nickel-lanthanum oxide-nano-titanium dioxide composite coating prepared in Example 5; (a) seawater; (b) SRB solution. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the embodiments and accompanying drawings:

[0035] Example 1

[0036] This embodiment uses spray granulation technology to prepare nano titanium dioxide agglomerated powder, using the following steps:

[0037] (1) Sodium carboxymethyl cellulose powder and deionized water were mixed at a mass ratio of 1.5:100, and then heated in a 90° C. water bath for 2 h while stirring to obtain a diluted sodium carboxymethyl cellulose solution as a binder.

[0038] (2) Weigh 2% of the mass of titanium dioxide powder as a dispersant.

[0039] (3) Mix the weighed nano-titanium dioxide powder, deionized water, and dispersant to ensure that the solid content of the binder is 35% after subsequent addition to obtain a mixed slurry, and mechanically stir for 1 hour.

[0040] (4) Weigh 50% of the mass of the titanium dioxide powder as a binder and add it to the mixed slurry of step (3), perform ultrasonic vibration for 0.5 hours, and then mechanically stir for 2 hours.

[0041] (5) Add the slurry from step (4) to the spray granulation equipment, set the "inducing air" operating frequency to 35 Hz, set the "atomization" operating frequency to 300 Hz, set the "inlet air temperature" to 220 degrees, set the "air hammer action time" to 2 seconds, and set the "air hammer interval time" to 15 seconds to obtain a powder with a particle size of 10 to 100 μm.

[0042] (6) The powder obtained in step (5) was heat treated at 800°C for 2h.

[0043] The prepared agglomerated nano-titanium dioxide powder was observed under a scanning electron microscope, and its morphology was as follows: Figure 1 As shown, it can be observed that the powders are well agglomerated, basically spherical, and have uniform size distribution.

[0044] Example 2

[0045] In this example, a nickel-lanthanum oxide-nano-titanium dioxide composite coating was prepared using plasma spraying technology on a 45# steel substrate. The nano-titanium dioxide agglomerated powder was prepared using the same process as in Example 1. This agglomerated powder was mixed with spherical nickel powder and mechanically mixed for 24 hours to obtain a composite feed powder.

[0046] (1) The substrate 45# steel was sandblasted and the surface of the sample was pretreated with G25 type crushed steel sand so that the substrate surface obtained a certain roughness, which was conducive to the adhesion of the coating.

[0047] (2) After sandblasting in step (1), the substrate is subjected to dust removal treatment. A compressed air machine is used to remove dust from the surface of the sample. Then, anhydrous ethanol is used to clean the sample under ultrasonic conditions to remove rust and stains on the surface of the material and improve the spraying quality.

[0048] (3) Plasma spraying technology is used to spray a base layer on the substrate after dust removal in step (2) with a thickness of 80 to 120 μm. The base layer material is a nickel-chromium-aluminum-yttrium alloy with a powder particle size of 45 to 120 μm.

[0049] (4) Plasma spraying technology is used to spray a composite coating on the substrate sprayed with the primer layer in step (3) to a thickness of 300 to 500 μm. GP-80 plasma spraying equipment is used, with argon gas at 80 L / h, hydrogen at 100 L / h, a BF-02 ultrafine powder feeder, a powder feed rate of 20 g / min, a handheld gun, external powder feeding, a spraying power of 35 kW (500 A × 64 V), and a gun distance of 100 mm.

[0050] The sprayed coating was observed by scanning electron microscope. Figure 2 This is its surface morphology.

[0051] Example 3

[0052] In this example, 45# steel was used as the substrate, and a nickel-lanthanum oxide-nano-titanium dioxide composite coating was prepared by plasma spraying technology, and the porosity difference between the composite coating and the ordinary micron-titanium dioxide coating was analyzed.

[0053] The coating preparation method of Example 3 is the same as that of Example 2. The cross section of the coating is polished and then observed by scanning electron microscopy. The porosity of the coating is calculated by Image J. Figure 3 The following diagram shows how the porosity is calculated. Compared to ordinary micronized titanium dioxide coatings, the porosity of the nickel-lanthanum oxide-nano-titanium dioxide composite coating is reduced from 7.60% to 2.08%.

[0054] Example 4

[0055] In this example, 45# steel was used as the substrate, and a plasma spraying technique was used to prepare a nickel-nano titanium dioxide composite coating, and the difference in fracture toughness between the composite coating and a common micron titanium dioxide coating was analyzed.

[0056] The coating preparation method of Example 4 is the same as that of Example 2. The fracture toughness is calculated by indentation method. The fracture toughness is 2.7Mpa·m 1 / 2 Increased to 3.9Mpa·m 1 / 2 .

[0057] Example 5

[0058] In this example, 45# steel was used as the substrate, and a plasma spraying technique was used to prepare a nickel-nano titanium dioxide composite coating, and the difference in corrosion resistance between the nickel-nano titanium dioxide composite coating and the ordinary micron titanium dioxide coating was analyzed.

[0059] Example 5 is the same as the coating preparation method of Example 2. On this basis, a copper wire is welded on the back of the sample by electric welding and the surrounding area is sealed with resin to obtain an electrochemical sample. The sample is placed in artificial seawater and SRB solution to test its polarization curve. Figure 4 This is a comparison of the polarization curves of nickel-lanthanum oxide-nano-titanium dioxide composite coating and ordinary micron-titanium dioxide coating. According to the Tafel fitting analysis of the polarization curves, the self-corrosion potential in artificial seawater increased from -678mV to -459mV, and the self-corrosion current density increased from 69.2×10 -6 A / cm 2 Reduced to 17.7×10 -6 A / cm 2 , the corrosion rate increased from 803.1×10 -3 mmpy decreased to 205.1×10 -3 mmpy; the self-corrosion potential in SRB solution increased from -486mV to -40.1mV, and the self-corrosion current density increased from 59.60×10 -6 A / cm 2 Reduced to 6.68×10 -6 A / cm 2 The corrosion rate is 691.91×10 -3 mmpy decreased to 77.60×10 -3 mmpy.

[0060] In summary, the present invention uses spray granulation technology to agglomerate nano-titanium dioxide to a size suitable for plasma spraying, and then deposits it on the surface of the substrate together with metallic nickel and lanthanum oxide to prepare a nickel-lanthanum oxide-nano-titanium dioxide composite coating. This process can effectively improve the density, toughness and corrosion resistance of the coating, and has important market value when applied to the protection of marine engineering equipment.

[0061] The above is a preferred embodiment of the present invention, but the present invention should not be limited to the contents disclosed in this embodiment. Therefore, any equivalent or modified implementations that do not depart from the spirit disclosed in the present invention fall within the scope of protection of the present invention.

Claims

1. A method for preparing a nickel-lanthanum oxide-nano-titanium dioxide composite coating, characterized in that: The following steps are involved: Step 1: preparing nano titanium dioxide agglomerated powder, comprising: (1) Preparation of dispersant and binder: Sodium polyphosphate is used as dispersant, sodium carboxymethyl cellulose solution is used as binder, the mass of the dispersant powder accounts for 1% to 2% of the mass of the nanopowder; the mass of the binder accounts for 50% of the mass of the nanopowder, wherein the mass ratio of sodium carboxymethyl cellulose powder to deionized water is 1.5:

100. After weighing sodium carboxymethyl cellulose and deionized water according to the ratio, heat in a water bath at 90°C and stir for 2 hours; (2) preparing a slurry: mixing the dispersant with nano-titanium dioxide and deionized water, mechanically stirring for 1 hour, adding the binder and ultrasonically shaking for 0.5 hours, and then mechanically stirring for 2 hours to obtain a slurry; (3) spray granulation: the slurry is added to a spray granulation device for spray granulation to obtain a powder with a particle size of 10 to 100 μm, and heat treated at 800° C. to obtain nano-titanium dioxide agglomerated powder; Step 2, preparing nickel-lanthanum oxide-nano-titania composite powder: the nano-titania agglomerated powder, metallic nickel powder, and lanthanum oxide powder are placed in a V-type powder mixer and fully mixed for 24 hours to obtain a nickel-lanthanum oxide-nano-titania mixed feed powder, wherein the mass of the nickel powder accounts for 10% to 30% of the total powder mass, and the mass of the lanthanum oxide powder accounts for 3% to 9% of the total powder mass; Step 3, preparing a nickel-lanthanum oxide-nano-titanium dioxide composite coating, comprising: (a) Sandblasting: G25 crushed steel grit is used to pre-treat the substrate surface to obtain a certain degree of roughness; (b) Dust removal: Use compressed air to remove dust from the surface of the substrate after sandblasting, and then use anhydrous ethanol to clean it under ultrasonic conditions to remove rust and stains on the surface of the material; (c) Plasma spraying primer: spraying a primer layer on the surface of the dust-removed substrate, wherein the primer layer is made of nickel-chromium-aluminum-yttrium alloy; (d) Plasma spraying composite coating: spraying composite coating on the substrate sprayed with the primer layer in step (c): spraying nickel-lanthanum oxide-nano-titanium dioxide composite coating on the substrate sprayed with the primer layer by plasma spraying.

2. The method for preparing the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 1, characterized in that: In step (2), the solid content of the slurry is 35% to 40%.

3. The method for preparing the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 1, characterized in that: In step (3), the spray granulation equipment adopts a centrifugal spray dryer with model G1 PP-5000Y, and the induced draft operating frequency is set to 35Hz according to the material specific gravity, the atomization operating frequency is 300Hz, the inlet air temperature is 220 degrees, the air hammer action time is 2 seconds, and the air hammer interval time is 15 seconds; before use, the induced draft fan is turned on, the electric heating is turned on, the lighting is turned on, and the slurry to be dried is poured into the barrel; when the inlet air temperature reaches the required set temperature, the peristaltic pump on the touch screen is started, the speed is adjusted to 10 rpm, the atomization on the touch screen is started, and the atomizer nozzle is rotated. When the speed is normal, the atomizer is allowed to spray water for a period of time so that the outlet air temperature reaches the predetermined exhaust air temperature of 100°C, and then quickly converted into the liquid in the mixing barrel. The liquid is steplessly adjusted by a Mono pump, gradually increasing from small to large.

4. The method for preparing the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 1, characterized in that: In step (c), the material of the primer layer is nickel-chromium-aluminum-yttrium alloy, the powder particle size is 45 to 120 μm, and the thickness of the primer layer is 80 to 120 μm.

5. The method for preparing the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 1, characterized in that: In step (d), the thickness of the nickel-lanthanum oxide-nano-titanium dioxide composite coating is 300 to 500 μm.

6. The method for preparing the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 1, characterized in that: In step (c) and step (d), a GP-80 plasma spraying equipment was used, the flow rate of argon was 80 L / h, and the flow rate of hydrogen was 100 L / h; at the same time, a BF-02 ultrafine powder feeder was used, the powder feeding rate was 20 g / min, a handheld gun and external powder feeding method were used, the spraying power was 35 kW, and the gun distance was 100 mm.

7. A nickel-lanthanum oxide-nano-titanium dioxide composite coating, characterized in that: The composition is 10%-30% Ni, 3%-9% La2O3 and 61%-87% TiO2, with a thickness of 300-500 μm, and is prepared by the preparation method of the nickel-lanthanum oxide-nano titanium dioxide composite coating according to any one of claims 1 to 6.

8. Use of the nickel-lanthanum oxide-nano-titanium dioxide composite coating according to claim 7 in the protection of marine engineering equipment.

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