CN113912298B - Corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystalline in situ and preparation method thereof - Google Patents

Corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystalline in situ and preparation method thereof Download PDF

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CN113912298B
CN113912298B CN202111316964.3A CN202111316964A CN113912298B CN 113912298 B CN113912298 B CN 113912298B CN 202111316964 A CN202111316964 A CN 202111316964A CN 113912298 B CN113912298 B CN 113912298B
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fluoride
enamel
enamel coating
oxide
situ
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CN113912298A (en
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陈明辉
甄宇
王群昌
王金龙
周文
王福会
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Northeastern University China
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    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/16—Halogen containing crystalline phase
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03B—MANUFACTURE, SHAPING, OR SUPPLEMENTARY PROCESSES
    • C03B5/00—Melting in furnaces; Furnaces so far as specially adapted for glass manufacture
    • C03B5/16—Special features of the melting process; Auxiliary means specially adapted for glass-melting furnaces
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C1/00—Ingredients generally applicable to manufacture of glasses, glazes, or vitreous enamels
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C10/00—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition
    • C03C10/0036—Devitrified glass ceramics, i.e. glass ceramics having a crystalline phase dispersed in a glassy phase and constituting at least 50% by weight of the total composition containing SiO2, Al2O3 and a divalent metal oxide as main constituents
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
    • C03C8/02—Frit compositions, i.e. in a powdered or comminuted form
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
    • C23D5/00—Coating with enamels or vitreous layers
    • C23D5/02—Coating with enamels or vitreous layers by wet methods
    • C—CHEMISTRY; METALLURGY
    • C03—GLASS; MINERAL OR SLAG WOOL
    • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
    • C03C2207/00—Compositions specially applicable for the manufacture of vitreous enamels
    • C03C2207/04—Compositions specially applicable for the manufacture of vitreous enamels for steel

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Abstract

The invention aims to provide a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ and a preparation method thereof, wherein a certain proportion of fluoride is added during the melting of the enamel coating, and is combined with calcium oxide or barium oxide components in enamel glaze to precipitate nanoscale calcium fluoride or barium fluoride crystals in situ; the mass fraction ratio of the enamel coating is as follows: 43-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide, and 5-10% of fluoride. According to the invention, the fluoride nanocrystalline is separated out in situ by control, so that the self-lubricating effect of the enamel coating with low friction coefficient and low wear rate at room temperature can be realized, and the limitation of the low-temperature non-lubricating effect of the traditional fluoride lubricant is broken through. In addition, the coating keeps the excellent acid and alkali corrosion resistance of the enamel, and realizes the integration of self-lubricating and corrosion resistance.

Description

Corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystalline in situ and preparation method thereof
Technical Field
The invention belongs to the technical field of material engineering, and relates to a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ and a preparation method thereof.
Background
For Al by scholars at home and abroad 2 O 3 Ceramics, ZrO 2 The self-lubricating of materials such as ceramics and the like, particularly the enamel and ceramic materials applied to the professional fields of tool antifriction, cutting property improvement and the like, have deeper research, and the intrinsic brittleness of the ceramic materials is a main problem which hinders the improvement of the wear resistance of the ceramic materials. The main idea of reducing the material abrasion is to add solid lubricant to different metal and ceramic materials or to form composite coating on a specific substrate by adopting deposition technologyAnd (4) a way. Fluoride is often added as a solid lubricant to lubricating oils, wear resistant composites, gradient materials to enhance the high temperature lubricity of the materials, or used in combination with other lubricating materials to produce better synergistic lubricating effects, such as CaF 2 -Au、CaF 2 -Mo、CaF 2 -Ag、CaF 2 -BaF 2 Eutectic crystal and the like, and remarkable results are obtained. Most studies have shown that CaF 2 Lubrication can be achieved at high temperatures because of CaF 2 The ionic compound is of a non-laminated structure, the failure mode is gradually changed from brittle failure to plastic flow along with the increase of the temperature, the friction coefficient is reduced, and the lubricating property of the ionic compound gradually appears and improves along with the increase of the temperature. CaF 2 A slip plane exists in the unit cell structure of (1); at high temperatures, the interatomic bond strength on the slip surface decreases, and the slip surface shear strength decreases, and sliding tends to occur. CaF, on the other hand 2 The material has strong adsorbability on solid surfaces, and the characteristic is easy to form a transfer film between opposite grinding surfaces; the cable made of CaF 2 The formed adsorption film can bear high load, and the mutual contact of the opposite-grinding surfaces is effectively prevented. CaF 2 The high-temperature slip property, the adsorptive film forming property and the thermochemical stability of the lubricating oil make it a good high-temperature solid lubricant. At present, CaF 2 The excellent self-lubricating performance of the solid lubricant under high temperature conditions is widely recognized for CaF 2 The lubrication research of (1) is mainly focused on the high-temperature condition at present, and the self-lubrication condition at normal temperature is rarely researched.
For enlarging the content of CaF 2 The lubricating temperature range of the lubricant material is researched by adopting CaF 2 The means of compounding the high-temperature lubricating phase with other low-temperature lubricating phases shows that the two lubricating phases can generate adverse effects, and the compounding design of the high-temperature lubricating phase and the low-temperature lubricating phase has certain defects, so that the CaF is subjected to 2 The normal temperature lubrication of (1) is yet to be further studied.
Disclosure of Invention
The invention provides a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystalline in situ and a preparation method thereof, which can realize the self-lubricating effect of the enamel coating with low friction coefficient and low wear rate at room temperature by controlling the in-situ precipitation of the fluoride nanocrystalline, and break through the limitation that the traditional fluoride self-lubricating phase is only applied above the ductile-brittle transition temperature.
The invention provides a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ, wherein a certain proportion of fluoride is added during smelting of the enamel coating, and the fluoride is combined with calcium oxide or barium oxide components in enamel glaze to precipitate nanoscale calcium fluoride or barium fluoride crystals in situ; the mass fraction ratio of the enamel coating is as follows: 43-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide, and 5-10% of fluoride.
In the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystals in situ, the sum of the contents of silicon dioxide and aluminum oxide is 57-68%.
In the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, the fluoride is calcium fluoride, barium fluoride or sodium fluoride.
In the corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ, the performance indexes of the enamel coating are as follows:
the coefficient of reciprocating friction at room temperature is less than or equal to 0.3, and the wear rate is less than or equal to 6 multiplied by 10 -6 mm 3 ·N -1 ·m -1 (ii) a After being corroded in 30vol% sulfuric acid solution at 80 ℃ for 24 hours, the corrosion weight loss is less than or equal to 0.2mg cm -2 ·d -1 (ii) a After being corroded by 3wt% sodium hydroxide solution at 80 ℃ for 24 hours, the corrosion weight loss is less than or equal to 0.5mg cm -2 。
The invention also provides a preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, which comprises the following steps:
step 1: ball-milling and mixing various oxides and fluorides, and smelting an enamel glaze;
step 2: preparing enamel micro powder by using the enamel glaze obtained in the step 1;
and 3, step 3: preparing enamel micro powder into a composite enamel suspension;
and 4, step 4: and spraying the composite enamel suspension on the surface of the part, and firing to obtain the composite enamel coating.
In the preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, the step 1 is specifically as follows:
step 1.1: mixing 43-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide and 5-10% of fluoride by using grinding balls; the rotating speed is 200-400 rpm, the time is 10-24 hours, and heating and smelting are carried out after uniform mixing;
step 1.2: heating from room temperature to 1450-1550 ℃ at the speed of 10-15 ℃/min in the heating and smelting process; and keeping the temperature for 1-2 h, and then performing water quenching to obtain the enamel glaze with specific components.
In the preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, the step 2 is specifically as follows: and (3) carrying out ball milling on the enamel glaze obtained in the step (1) to obtain enamel micro powder with the particle size of less than 10 microns, wherein the ball milling time is 50-150 h.
In the preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, the step 3 is specifically as follows:
taking 10-30 ml of absolute ethanol required by 1g of enamel micro powder as a dispersing agent; and (3) performing magnetic stirring and ultrasonic oscillation for 15-30 min to obtain the uniformly dispersed composite enamel suspension.
In the preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, the step 4 is specifically as follows:
step 4.1: uniformly spraying the composite enamel suspension on the high-temperature alloy part by using an air compressor, wherein the spraying pressure is 0.2-0.4 MPa, the spraying distance is 15-40 cm, and drying the sprayed coating for 10-60 min at 200-300 ℃ to obtain an original blank of the composite enamel coating;
step 4.2: sintering the dried original blank at the high temperature of 850-1050 ℃ for 5-30 min, taking out, and cooling in the atmosphere to obtain a composite enamel coating; the thickness of the finally prepared composite enamel coating exceeds 80 mu m.
The corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ and the preparation method thereof have the following beneficial effects:
1. the enamel coating prepared by the invention has simple preparation process, and the raw materials required in the formula can be directly purchased in the market.
2. The enamel coating prepared by the invention can react with an alloy substrate in the sintering preparation process to form chemical combination of an interface, and the interface spalling resistance of the coating under the thermal cycle condition is superior to that of the traditional ceramic coating.
3. The enamel coating prepared by the invention has excellent oxygen diffusion resistance and high-temperature oxidation resistance superior to that of the traditional metal coating.
4. The enamel coating prepared by the invention has excellent comprehensive performances such as heat corrosion resistance, thermal cycle spalling resistance, acid and alkali corrosion resistance and the like.
Drawings
FIG. 1 shows in-situ precipitation of nanocrystalline CaF in the present invention 2 Surface pattern of enamel coating;
FIG. 2A shows in situ precipitation of CaF 2 TEM microstructure of the enamel coating;
FIG. 2B is a Ca element map;
FIG. 2C is an F element map;
FIG. 2D is a SAED map of region b in FIG. 2A;
FIG. 3 shows in-situ precipitation of nanocrystalline CaF 2 The integral appearance of a grinding mark of the enamel coating after being rubbed for 1800s at room temperature;
FIG. 4 shows a ground and compounded CaF 2 The enamel coating surface of (a);
FIG. 5 shows a ground and compounded CaF 2 The enamel coating has the overall appearance of a grinding mark after being rubbed for 1800 seconds at room temperature;
FIG. 6 shows the overall appearance of the wear scar of a 304 stainless steel substrate after being rubbed for 1800s at room temperature.
Detailed Description
From the viewpoint of the frictional wear mechanism, the temperature factor determining whether the lubricating phase can spread into a film on the counter-grinding surface is not the ambient temperature, but the transient temperature when contacting the counter-grinding pair. During the friction process, there are many factors that affect the transient temperature, such as surface topography, contact compressive stress, friction coefficient, sliding speed, and material properties (such as lubricant phase size, thermal conductivity and heat capacity). Based on the method, the enamel coating capable of precipitating the nanocrystalline fluoride lubricating phase in situ is well adhered to the substrate, the expected self-lubricating effect is achieved, the enamel coating is used as an inert coating, the enamel coating shows an excellent protection effect in heavy corrosion environments such as sodium hydroxide and concentrated sulfuric acid, and the unification of self-lubricating and corrosion resistance is realized. The present invention is described in detail below with reference to the drawings and examples, but the scope of the present invention is not limited by the drawings and examples.
The corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ is prepared by adding a certain proportion of fluoride during smelting, combining the fluoride with calcium oxide or barium oxide components in enamel glaze and precipitating nanoscale calcium fluoride or barium fluoride crystals in situ; the enamel coating comprises the following components in percentage by mass: 43-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide, and 5-10% of fluoride.
In specific implementation, the sum of the contents of the silicon dioxide and the aluminum oxide is 57-68%. The fluoride is calcium fluoride, barium fluoride or sodium fluoride. The performance indexes of the enamel coating are as follows:
the coefficient of reciprocating friction at room temperature is less than or equal to 0.3, and the wear rate is less than or equal to 6 multiplied by 10 -6 mm 3 ·N -1 ·m -1 (ii) a After being corroded in 30vol% sulfuric acid solution at 80 ℃ for 24 hours, the corrosion weight loss is less than or equal to 0.2mg cm -2 ·d -1 (ii) a After being corroded by 3wt% sodium hydroxide solution at 80 ℃ for 24h, the corrosion weight loss is less than or equal to 0.5mg cm -2 。
The invention also provides a preparation method of the corrosion-resistant self-lubricating enamel coating capable of precipitating the fluoride nanocrystalline in situ, which comprises the following steps:
step 1: ball milling and mixing various oxides and fluorides, and smelting an enamel glaze, which specifically comprises the following steps:
step 1.1: mixing 43-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide and 5-10% of fluoride by using grinding balls; rotating at the speed of 200-400 r/min for 10-24 hours, and heating and smelting after uniform mixing;
step 1.2: heating from room temperature to 1450-1550 ℃ at a speed of 10-15 ℃/min in the heating and smelting process; and keeping the temperature for 1-2 h, and then performing water quenching to obtain the enamel glaze with specific components.
Step 2: preparing enamel micro powder by using the enamel glaze obtained in the step 1, which specifically comprises the following steps:
and (3) carrying out ball milling on the enamel glaze obtained in the step (1) to obtain enamel micro powder with the particle size of less than 10 microns, wherein the ball milling time is 50-150 h.
And step 3: preparing the enamel micro powder into a composite enamel suspension, which specifically comprises the following steps:
taking 10-30 ml of absolute ethyl alcohol required by 1g of enamel micro powder as a dispersing agent; and (3) magnetically stirring and ultrasonically oscillating for 15-30 min to obtain the uniformly dispersed composite enamel suspension.
And 4, step 4: spraying the composite enamel suspension on the surface of a part, and firing to obtain a composite enamel coating, which comprises the following steps:
step 4.1: uniformly spraying the composite enamel suspension on the high-temperature alloy part by using an air compressor, wherein the spraying pressure is 0.2-0.4 MPa, the spraying distance is 15-40 cm, and drying the sprayed coating for 10-60 min at 200-300 ℃ to obtain an original blank of the composite enamel coating;
and 4.2: sintering the dried original blank at the high temperature of 850-1050 ℃ for 5-30 min, taking out, and cooling in the atmosphere to obtain a composite enamel coating; the thickness of the finally prepared composite enamel coating exceeds 80 mu m.
The technical solution of the present invention is further illustrated by the following examples.
Example 1
The enamel coating is prepared by taking a 304 stainless steel plate as a substrate, and the preparation process comprises the following steps:
(1) smelting enamel glaze:
the enamel coating comprises the following components in percentage by mass: 46% of silicon dioxide, 16% of aluminum oxide, 15% of calcium oxide, 8% of boron oxide, 5% of sodium oxide, 4% of calcium fluoride and 6% of sodium fluosilicate. During high-temperature smelting, sodium fluosilicate is decomposed into silicon fluoride gas and sodium fluoride. Wherein, the silicon fluoride gas escapes when being smelted at high temperature, and the sodium fluoride participates in the composition of the enamel glaze. Therefore, the fluoride in the enamel component is actually 6.9%.
Ball-milling and mixing the oxides, rotating at 320 r/min for 20 hours, uniformly mixing, and then heating and smelting, wherein the smelting process is as follows: heating from room temperature to 1450 ℃ at a rate of 10 ℃/min. Keeping the temperature of 1450 ℃ for 1.5h, and then performing water quenching to obtain the enamel glaze with specific components.
(2) Preparing enamel micro powder:
and carrying out planetary ball milling on the enamel glaze obtained after water quenching. The rotational speed is 320 r/min, the time is 100 hours, and the enamel micro powder with the grain diameter less than 10 mu m is prepared.
(3) Preparing a composite enamel suspension:
1g of enamel powder: preparing enamel suspension with 16ml of absolute alcohol, and magnetically stirring and ultrasonically oscillating for 20min to obtain the uniformly dispersed enamel suspension.
(4) Enamel spraying:
and spraying the enamel suspension on a 304 stainless steel sample by using an air compressor under the atmospheric pressure of 0.2MPa, wherein the spraying distance is 20cm, and drying for 10min by using a drying oven at the temperature of 250 ℃ to obtain an original blank of the enamel coating.
(5) Sintering of enamel coatings
And sintering the dried original enamel coating blank in a muffle furnace at 890 ℃ for 5min, taking out, and cooling in the atmosphere to obtain the enamel coating.
The surface appearance of the prepared coating is shown in figure 1, the coating is compact, and no air bubbles exist on the surface. The size of the in-situ precipitated calcium fluoride nanocrystal is 50-200 nm, as shown in FIGS. 2A-2D. Wherein FIG. 2A shows in situ precipitation of CaF 2 TEM microstructure of the enamel coating; FIG. 2B is Ca element mapping; FIG. 2C is an F element map; FIG. 2D is a SAED map of region b in FIG. 2A. The reciprocating friction coefficient is 0.20 at room temperature, the integral appearance of the grinding scar of the enamel coating after being rubbed for 1800s is shown in figure 3, the abrasion loss of the enamel coating for in-situ precipitation of the nanocrystalline calcium fluoride is extremely small, and only the wear loss is smallHas 5.92 multiplied by 10 -6 mm 3 ·N -1 ·m -1 The purposes of friction reduction and wear resistance at room temperature are achieved.
The research on the corrosion dynamic behavior of the coating in a 30vol% sulfuric acid solution at 80 ℃ shows that the high corrosion rate stage of the coating is mainly limited to the initial 1 hour, micro pits with extremely small sizes begin to appear, and the corrosion rate tends to be stable. And along with the prolonging of the corrosion time, the corrosion micro-pits are gradually blocked and repaired by the gel layer, and the surface of the sample becomes flat again. The original luster and color of the paint are kept in the whole corrosion process of 24 hours, the paint shows excellent concentrated acid corrosion resistance, and the corrosion weight loss is only 0.11mg cm -2 。
The research on the corrosion dynamics behavior of the coating in a sodium hydroxide solution with the temperature of 80 ℃ and the weight percent of 3 shows that the surface of the coating is relatively flat after corrosion, the measured surface roughness Ra value is 0.062, which indicates that the alkali resistance of the enamel coating is very outstanding, and the corrosion weight loss of the high-temperature alkali liquor in 24 hours is only 0.23mg cm -2 。
Comparative example 1
The difference from the embodiment 1 is that the enamel glaze removes calcium fluoride components, and the component ratio (mass fraction) is as follows: 48% of silicon dioxide, 16% of aluminum oxide, 16% of calcium oxide, 8% of boron oxide, 5% of sodium oxide and 6% of sodium fluosilicate. During high-temperature smelting, sodium fluosilicate is decomposed into silicon fluoride gas and sodium fluoride. Wherein, the silicon fluoride gas escapes when being smelted at high temperature, and the sodium fluoride participates in the composition of the enamel glaze. Therefore, the fluoride in the enamel component is actually 2.8%.
(1) Smelting enamel glaze:
ball-milling and mixing the oxides, rotating at 320 r/min for 24 hours, uniformly mixing, and then heating and smelting, wherein the smelting process is as follows: heating from room temperature to 1450 deg.C at a speed of 10 deg.C/min; keeping the temperature of 1450 ℃ for 1.5h, and then performing water quenching to obtain the enamel glaze with specific components.
(2) Preparing enamel micro powder:
the water quenched enamel glaze is ball milled in a planetary way. The rotational speed is 320 r/min, the time is 100 hours, and the enamel micro powder with the grain diameter less than 10 mu m is prepared.
(3) The enamel micro powder and the micron-sized calcium fluoride powder are mixed by ball milling, the mass ratio of the two powders is 100:4, the ball milling mixing speed is 320 r/min, and the time is 4 hours. The enamel-based composite powder is prepared, and the mass of the fluoride accounts for 6.5 percent of the total.
And dispersing the enamel-based composite powder in absolute alcohol, and coating and sintering the enamel-based composite powder on a 304 stainless steel substrate to prepare an enamel coating. The surface of the coating was distributed with many bubbles as shown in fig. 4. Fluoride added into the outer body, namely 4 percent of calcium fluoride, has larger grain size and can not be fused into an enamel structure; and the fluoride (introduced in the form of sodium fluosilicate) added in the smelting stage has low content, and a small amount of nano fluoride crystals precipitated in the enamel are unevenly distributed. The coefficient of reciprocal friction of the enamel coating is 0.37 at room temperature, and the integral appearance of the grinding mark of the enamel coating after being rubbed for 1800s is shown in figure 5. The abrasion loss is similar to that of the 304 stainless steel matrix shown in figure 6, namely, calcium fluoride added in the ball milling stage has no self-lubricating effect at room temperature because the calcium fluoride cannot be fused into an enamel structure and has large size.
Example 2
The difference from the embodiment 1 is that the enamel coating comprises the following components in percentage by weight: 49.46 wt% of silicon dioxide, 19.3 wt% of aluminum oxide, 15.55 wt% of calcium oxide, 8.29 wt% of boron oxide, 5.18 wt% of sodium oxide, 1.1 wt% of calcium fluoride and 1.12 wt% of sodium fluosilicate, wherein the addition amount of fluoride accounts for 1.5 wt% of the mass of the enamel coating.
The self-lubricating enamel coating prepared on the 304 stainless steel substrate has a compact structure, and the coating has no micro defects such as bubbles, cracks and the like; the precipitated nanocrystalline calcium fluoride can be seen under a transmission electron microscope, but the fluoride content is low and the distribution is not uniform; the coefficient of reciprocal friction of the coating is 0.43 at room temperature, and the wear rate is 5.98 multiplied by 10 -6 mm 3 ·N -1 ·m -1 . It can be seen that the self-lubricating effect is greatly impaired when the fluoride content is too low, despite the low wear rate.
Example 3
The difference from the embodiment 1 lies in that the enamel coating comprises the following components: 41.47 wt% of silicon dioxide, 11.23 wt% of aluminum oxide, 15.55 wt% of calcium oxide, 8.29 wt% of boron oxide, 5.18 wt% of sodium oxide, 4.06 wt% of calcium fluoride and 14.22 wt% of sodium fluosilicate, and the addition amount of fluoride accounts for 10.5 wt% of the mass of the enamel coating.
The surface of the self-lubricating enamel coating prepared on the 304 stainless steel substrate has a small amount of bubbles and has no micro defects such as cracks; a large amount of uniform nanocrystalline barium fluoride can be separated out under a transmission electron microscope; the coefficient of reciprocal friction is 0.22 at room temperature, and the wear rate is 2.76 multiplied by 10 -4 mm 3 ·N -1 ·m -1 (ii) a Compared with the enamel coating in the embodiment 1, the enamel glaze has overhigh fluoride content, can precipitate a large amount of fluoride nanocrystals, and realizes normal-temperature self-lubrication. However, the high content of fluoride reduces the melting point and hardness of the coating, further reduces the wear resistance of the coating, and the wear rate of the enamel coating is high.
Example 4
The difference from the embodiment 1 lies in the component proportion of the enamel coating, and the barium fluoride with the same mass fraction is used for replacing the calcium fluoride, which is as follows: 45.71 wt% of silicon dioxide, 15.55 wt% of aluminum oxide, 15.55 wt% of calcium oxide, 8.29 wt% of boron oxide, 5.18 wt% of sodium oxide, 3.5 wt% of barium fluoride and 6.22 wt% of sodium fluosilicate, wherein the addition amount of fluoride accounts for 6 wt% of the mass of the enamel coating.
The self-lubricating enamel coating prepared on the 304 stainless steel substrate has a compact structure, and the coating has no micro defects such as bubbles, cracks and the like; precipitated nanocrystalline barium fluoride can be seen under a transmission electron microscope; the coefficient of reciprocating friction is 0.23 at room temperature, and the wear rate is 5.98 multiplied by 10 -6 mm 3 ·N -1 ·m -1 。
After the coating is corroded in 30vol% sulfuric acid solution for 24 hours at 80 ℃, the corrosion weight loss is 0.15mg cm -2 The surface keeps the original luster and color of the enamel. After 24 hours in a sodium hydroxide solution of 3wt% at 80 ℃, the surface roughness Ra value is 0.064, and the corrosion weight loss is 0.31mg cm -2 Thus, the enamel coating has excellent acid and alkali corrosion resistance.
Example 5
The difference from the embodiment 1 is that the alloy matrix is K38G high-temperature alloy, the self-lubricating enamel coating prepared by sintering has compact structure, and the coating is well combined with the matrix alloy; at the same timeThe self-lubricating enamel coating prepared on the substrate has a compact structure, and the coating has no micro defects such as bubbles, cracks and the like; the size of the calcium fluoride nano crystal particles precipitated in situ is not more than 200 nm; the coefficient of reciprocating friction at room temperature is 0.22, and the wear rate is 5.90 multiplied by 10 -6 mm 3 ·N -1 ·m -1 。
Example 6
The difference from the embodiment 1 is that the alloy matrix is TC4 titanium alloy, the self-lubricating enamel coating prepared by sintering has compact structure, and the coating is well combined with the matrix alloy; the self-lubricating enamel coating prepared on the substrate has a compact structure, and the coating has no micro defects such as bubbles, cracks and the like; the size of the calcium fluoride nano crystal particles precipitated in situ is not more than 200 nm; the coefficient of reciprocating friction at room temperature was 0.21, and the wear rate was 5.91X 10 -6 mm 3 ·N -1 ·m -1 。
The fluoride nano crystal particles precipitated in situ have small size, the transient temperature is higher in the friction and wear process under the same condition, the service environment temperature of the brittleness-to-plasticity transition of single fluoride particles is reduced, and finally a lubricating film can be spread on a friction surface at room temperature, so that the self-lubricating effect of low friction coefficient and low wear rate is realized, the limitation that the traditional fluoride coating is only applied above the toughness and brittleness transition temperature is broken through, and a new idea of realizing wide-temperature-range lubrication by depending on a single lubricating phase is developed. In addition, the coating is well adhered to the substrate, the expected self-lubricating effect is achieved, the enamel coating is used as an inert coating, the excellent protection effect is shown in the heavy corrosion environment such as sodium hydroxide and concentrated sulfuric acid, and the unification of self-lubricating and corrosion resisting properties is realized.
The above description is only a preferred embodiment of the present invention and should not be taken as limiting the scope of the invention, which is intended to cover any modifications, equivalents, improvements, etc. within the spirit and scope of the present invention.

Claims (7)

1. The corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystalline in situ is characterized in that a certain proportion of fluoride is added during smelting of the enamel coating, and the fluoride is combined with calcium oxide or barium oxide components in enamel glaze to precipitate nanoscale calcium fluoride or barium fluoride crystals in situ; the mass fraction ratio of the enamel coating is as follows: 46-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide, and 5-10% of fluoride is added;
the performance indexes of the enamel coating are as follows:
the coefficient of reciprocal friction at room temperature is less than or equal to 0.3, the wear rate is less than or equal to 6 multiplied by 10 -6 mm 3 •N -1 •m -1 (ii) a After being corroded in 30vol% sulfuric acid solution at 80 ℃ for 24 hours, the corrosion weight loss is less than or equal to 0.2mg -2 •d -1 (ii) a After being corroded by 3wt% sodium hydroxide solution at 80 ℃ for 24h, the corrosion weight loss is less than or equal to 0.5mg -2 。
2. The corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ as claimed in claim 1 wherein the sum of the contents of silica and alumina is 57 to 68%.
3. The corrosion-resistant self-lubricating enamel coating capable of in-situ precipitation of fluoride nanocrystals as recited in claim 1, wherein the fluoride is calcium fluoride, barium fluoride or sodium fluoride.
4. A method for preparing a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ as claimed in any one of claims 1 to 3, comprising the steps of:
step 1: ball milling and mixing various oxides and fluorides, and smelting enamel glaze;
step 2: preparing enamel micro powder by using the enamel glaze obtained in the step 1;
and 3, step 3: preparing the enamel micro powder into a composite enamel suspension;
and 4, step 4: spraying the composite enamel suspension on the surface of a part, and burning to obtain a composite enamel coating;
the step 1 specifically comprises the following steps:
step 1.1: mixing 46-58% of silicon dioxide, 10-20% of aluminum oxide, 12-18% of calcium oxide or barium oxide, 5-10% of boron trioxide, 3-9% of sodium oxide or potassium oxide and 5-10% of fluoride by using grinding balls; the rotating speed is 200-400 rpm, the time is 10-24 hours, and heating and smelting are carried out after uniform mixing;
step 1.2: heating from room temperature to 1450-1550 ℃ at a speed of 10-15 ℃/min in the heating and smelting process; and keeping the temperature for 1-2 h, and then performing water quenching to obtain the enamel glaze with specific components.
5. The method for preparing the corrosion-resistant self-lubricating enamel coating capable of in-situ precipitating the fluoride nanocrystals according to claim 4, wherein the step 2 is specifically as follows: and (2) performing ball milling on the enamel glaze obtained in the step (1) to obtain enamel micro powder with the particle size of less than 10 microns, wherein the ball milling time is 50-150 hours.
6. The method for preparing a corrosion-resistant self-lubricating enamel coating capable of precipitating fluoride nanocrystals in situ as claimed in claim 4, wherein the step 3 is specifically:
taking 10-30 ml of absolute ethyl alcohol required by 1g of enamel micro powder as a dispersing agent; and (3) magnetically stirring and ultrasonically oscillating for 15-30 min to obtain the uniformly dispersed composite enamel suspension.
7. The method for preparing the corrosion-resistant self-lubricating enamel coating capable of in-situ precipitating the fluoride nanocrystals according to claim 4, wherein the step 4 is specifically as follows:
step 4.1: uniformly spraying the composite enamel suspension on the high-temperature alloy part by using an air compressor, wherein the spraying pressure is 0.2-0.4 MPa, the spraying distance is 15-40 cm, and drying the sprayed coating for 10-60 min at 200-300 ℃ to obtain an original blank of the composite enamel coating;
step 4.2: sintering the dried original blank at the high temperature of 850-1050 ℃ for 5-30 min, taking out, and cooling in the atmosphere to obtain a composite enamel coating; the thickness of the finally prepared composite enamel coating exceeds 80 mu m.
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