A protective coating for nickel alloy steel and a method of making

Abstract

The application discloses a protective coating for nickel alloy steel and a preparation method thereof. The coating comprises composite powder, modified binder and water in a mass ratio of 80:(30-70):(10-20). The composite powder comprises 15-37 parts of glass powder, 4-9 parts of coal gangue fine powder, 8-15 parts of mullite fine powder, 5-9 parts of silicon carbide fine powder, 33-60 parts of alpha-Al2O3 micro powder, 1-5 parts of zirconium oxide powder, 1-4 parts of iron powder, 1-3 parts of nickel oxide powder and 0.4-1 part of carboxymethyl cellulose. The modified binder is obtained by mixing sodium-potassium composite water glass and mixed solution A. The mixed solution A is obtained by mixing fly ash, phosphoric acid and water and then heating. The protective coating has more than 90% oxidation protection effect within 1100-1300 DEG C, reduces surface layer element segregation of the nickel alloy steel, has more than 0.80 infrared absorption rate in the 1-8 micron wave band at high temperature, completely self-stripping and high cost performance.

Description

TECHNICAL FIELD

[0001] The present application relates to a protective coating for metal and a preparation method, in particular to a protective coating for nickel alloy steel and a preparation method. BACKGROUND

[0002] Nickel alloy steel is widely used in the preparation of liquefied natural gas exploration, transportation and storage equipment due to its excellent low-temperature toughness and low thermal expansion coefficient. In order to improve the internal structure of nickel alloy steel, eliminate defects or perform hot rolling, high-temperature heat treatment of 1100-1300°C is generally required for nickel alloy steel, and the heat treatment time increases with the increase of the size of nickel alloy steel. During the heat treatment process, the nickel alloy steel will be severely oxidized, and a nickel-rich layer will be produced which is difficult to remove by high-pressure descaling water gun, resulting in defects such as pits and even cracks in the later steel plate, thereby greatly reducing the yield. At present, low-temperature hot rolling method, inert atmosphere protection method and protective coating method are mainly used for protection. The protective coating method is widely used due to its excellent protection effect, simple operation and high economic efficiency.

[0003] Patent CN101705024 discloses a high-nickel steel high-temperature oxidation-resistant coating, which is prepared by mixing 10-25wt% SiO2, 20-25wt% Al2O3, 35-60wt% chromium powder, 0-15wt% MgO and 0-15wt% ZrO2 powder with a high-temperature binder to form a high-temperature resistant coating, which can effectively reduce the generation of iron oxide scale and reduce the adhesion of iron oxide scale. But the coating is mainly composed of high-melting-point ceramic phases, and the coating is difficult to densify, so it is difficult to have good protective effect at 1300℃, and the oxidation protection rate at 1300℃ is 75-85%, in addition, the chromium powder in the component is easy to react with nickel steel, increasing the difficulty of self-peeling. Yang Xiaohu et al. (Yang Xiaohu, Zhou Xin, Wang Songtao, et al. Mg-Al-Fe spinel protective layer mechanism for nickel-containing alloy steel [J]. Coatings Industry, 2016, 46(1): 1-7.) prepared a Mg-Al-Fe spinel protective layer from 65wt% MgO and 35wt% Al2O3. But the coating is composed of high-melting-point ceramic phases, and the densification is more difficult, so the protection rate is less than 60% at 1100℃, 1200℃ and 1250℃; In addition, because MgO and Al2O3 in the coating are easy to react with iron oxide of nickel-containing alloy steel, the problem of surface element segregation still exists. Patent CN110452565A discloses a high-temperature oxidation-resistant coating for nickel-based alloy hot rolling and a preparation method thereof. 15-30 parts by mass of nano-SiO2, 6-8 parts by mass of nano-Al2O3, 4-7 parts by mass of nano-MgO, 2-5 parts by mass of nano-TiO2, 10-20 parts by mass of silicon carbide and 4-6 parts by mass of boron oxide are used as powder, and the protective coating is prepared by using amino silane modified powder. The protective rate of the coating of the patent can reach 92% at 1250℃, but the introduction of a large amount of nano-sized raw materials not only increases the cost, but also has the problem of difficult dispersion of nano-powder in the coating preparation process. Wang Huya et al. (Wang Huya, Zhang Guojie, Chen Chen, et al. Influence of phosphate coating on temperature field and oxidation resistance of billet [J]. Metal Processing (hot working), 2023(04): 85-90.) simulated the surface and internal temperature of the billet after heating at 1120℃ for 1h with initial temperature of 700℃ by using ANSYS software. The results show that the surface temperature of the billet with coating is about 50℃ lower than that of the billet without coating, and the internal temperature difference is about 10℃, and the surface coating of the billet acts as a "thermal resistance", increasing the energy consumption of the hot working of the billet. SUMMARY

[0004] The purpose of the present application is to provide a high-temperature oxidation-resistant, high-heat-absorbing self-peeling protective coating for nickel alloy steel.

[0005] The second purpose of the present application is to provide a preparation method of the protective coating for nickel alloy steel.

[0006] Technical solution: The protective coating for nickel alloy steel described in the present invention includes a composite powder, a modified binder and water; the mass ratio of the composite powder, the modified binder and water is 80:(30-70):(10-20); the composite powder includes, by mass: 15-37 parts of glass powder, 4-9 parts of coal gangue fine powder, 8-15 parts of mullite fine powder, 5-9 parts of silicon carbide fine powder, 33-60 parts of α-Al2O3 micropowder, 1-5 parts of zirconium oxide powder, 1-4 parts of iron powder, 1-3 parts of nickel oxide powder and 0.4-1 part of carboxymethyl cellulose; the modified binder is obtained by mixing sodium potassium composite water glass with mixed liquid A; the mixed liquid A is obtained by mixing fly ash, phosphoric acid and water and then heating.

[0007] The mass ratio of the sodium potassium composite water glass to the mixed solution A is 1: (0.1-0.4)

[0008] Wherein, the mass ratio of the fly ash, phosphoric acid and water is 1:0.2:(1.5-4).

[0009] The sodium-potassium composite water glass is obtained by uniformly mixing sodium water glass and potassium water glass in a mass ratio of 1: (0.1-10).

[0010] Wherein, the modulus of the potassium water glass and the sodium water glass is 3.0-3.5.

[0011] Wherein, the particle size of the fly ash, coal gangue fine powder and zirconium oxide powder is less than 45 μm.

[0012] The SiO2 content of the glass powder is ≤75wt%, and the total content of Na2O and K2O is ≥10wt%; and the particle size of the glass powder is less than 18μm.

[0013] Among them, the SiC content of the silicon carbide fine powder is ≥98wt%; the particle size of the silicon carbide fine powder is less than 45μm; the Fe content of the iron powder is ≥99wt%; the particle size of the iron powder is less than 45μm; the NiO content of the nickel oxide powder is ≥99wt%; and the particle size of the nickel oxide powder is less than 10μm.

[0014] Wherein, the Al2O3 content of the α-Al2O3 micropowder is ≥99wt%; and the particle size of the α-Al2O3 micropowder is less than 5μm.

[0015] The method for preparing the protective coating for nickel alloy steel comprises the following steps:

[0016] (1) mixing sodium water glass:potassium water glass with a mass ratio of 1:(0.1-10) to obtain a composite water glass, then mixing fly ash, 50-85% by mass of phosphoric acid and water with a mass ratio of 1:0.2:(1.5-4) to obtain a mixed solution A under the condition of heating at 60-80 DEG C in water bath for 0.5-1h, then mixing the composite water glass and the mixed solution A with a mass ratio of 1:(0.1-0.4) to obtain a modified binder;

[0017] (2) mixing 15-37 parts by mass of glass powder, 4-9 parts of coal gangue powder, 8-15 parts of mullite powder, 5-9 parts of silicon carbide powder, 33-60 parts of alpha-Al2O3 powder, 1-5 parts of zirconia powder, 1-4 parts of iron powder, 1-3 parts of nickel oxide powder and 0.4-1 part of carboxymethyl cellulose to obtain a composite powder;

[0018] (3) mixing the composite powder, the modified binder and water with a mass ratio of 80:(30-70):(10-20) to obtain a protective coating for nickel alloy steel.

[0019] The principle of the application is that the protective coating uses alpha-Al2O3 powder and mullite powder as main raw materials, both of which are high-melting-point phases, so that the coating can stably play a protective role under the use environment of a heating furnace at 1100 DEG C-1300 DEG C. When the protective coating forms a coating layer and is used at high temperature, the glass powder first forms a low-viscosity glass liquid phase, which rapidly spreads on the surface of the nickel alloy steel and starts to play a role in reducing the oxidation of the nickel alloy steel in a short time; then the glass powder, the impurity phase of the coal gangue powder, the fly ash, the potassium water glass, the sodium water glass in the modified binder and a small amount of alpha-Al2O3 powder and mullite powder further react to generate a glass liquid phase with higher viscosity, and these high-viscosity glass liquid phases can further react with the alpha-Al2O3 powder and the mullite powder to form a relatively dense protective layer, so that oxygen is difficult to enter the nickel alloy steel substrate, thereby ensuring that the coating layer has excellent oxidation protection effect in a wide temperature range. In addition, the carbon in the coal gangue powder and the iron powder in the coating layer oxidize at high temperature, consume part of the oxygen on the surface of the nickel alloy steel, and thus also reduce the high-temperature oxidation of the nickel alloy steel.

[0020] The nickel oxide powder, the iron powder and the Fe2O3 obtained by oxidation of the iron powder used in the technical scheme of the application make the Ni and Fe elements in the coating layer have a certain abundance, so that the element segregation in the nickel alloy steel substrate is effectively inhibited, and the surface quality of the nickel alloy steel is greatly improved.

[0021] In the heating furnace working environment, the dominant transfer mode of heat is radiation, and the infrared rays of radiation are all in the near-mid infrared band. The silicon carbide in the technical scheme has high infrared absorption rate in the near-mid infrared band, but the silicon carbide is easy to be oxidized at high temperature. However, the impurity phase of the glass powder and the coal gangue powder, the fly ash in the modified binder, the potassium water glass, the sodium water glass and a small amount of alpha-Al2O3 micro powder and mullite powder in the technical scheme can react to generate a high-viscosity glass liquid phase at high temperature, which can wrap the surface of the silicon carbide, and the oxidation of the silicon carbide is effectively inhibited, so that the coating has good heat absorption function. At the same time, the Fe2O3 generated by the oxidation of the iron powder will react with the oxidized nickel to generate the NiFe2O4 spinel with high infrared absorption rate in the near-mid infrared band, and the silicon carbide and the generated NiFe2O4 spinel will make the coating have high infrared absorption rate, so that the coating is no longer a "thermal resistance", and the rapid heating of the billet can be realized. On the other hand, the Kirchhoff's law of thermal radiation shows that at the same temperature, the radiation value and the absorption value of different objects to the same wavelength are equal, so the protective coating of the application not only has excellent heat absorption capacity, but also has good heat radiation capacity, which can make the large-size nickel alloy steel reach the target temperature faster, thereby shortening the heat treatment cycle and effectively reducing the energy consumption.

[0022] The protective coating of the application has corundum and mullite as main phases at high temperature, and the difference between the thermal expansion coefficients of these phases and the nickel alloy steel is large, and the zirconia powder in the coating will also undergo crystal type transformation when the temperature changes. For example, when the temperature drops to 1100 DEG C, the crystal type of the zirconia changes from tetragonal to monoclinic structure with volume expansion, and cracks are generated in the coating during cooling and shrinkage. The coating using the protective coating of the application will form an overall structure composed of corundum phase, mullite phase, zirconia phase and glass liquid phase at high temperature, and under the coupling action of the difference in thermal expansion coefficient and the crystal type transformation, the coating has good spontaneous peeling property under the conditions of rapid cooling of high-pressure water and the like, which is beneficial to the later rolling of the nickel alloy steel.

[0023] Advantages: Compared with the prior art, the nickel alloy steel protective coating of the application has the following remarkable effects: the nickel alloy steel protective coating of the application has more than 90% oxidation protection effect at 1100-1300 DEG C, reduces the surface element segregation of the nickel alloy steel, has an infrared absorption rate of more than 0.80 in the high-temperature 1-8 micron band, completely self-peels and has high cost performance. DETAILED DESCRIPTION

[0024] The application will be further described in detail below.

[0025] Example 1

[0026] A preparation method of a high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel, comprising the following steps:

[0027] (1) uniformly mixing sodium water glass and potassium water glass in a mass ratio of 1:0.1 to obtain a composite water glass, then mixing fly ash, 50% by mass phosphoric acid and water in a mass ratio of 1:0.2:4, and stirring under 70°C water bath heating conditions for 45 min to obtain a mixed solution A; then mixing the composite water glass and the mixed solution A in a mass ratio of 1:0.1 to obtain a modified binder;

[0028] (2) uniformly mixing 15 parts of glass powder, 4 parts of coal gangue powder, 11 parts of mullite powder, 6 parts of silicon carbide powder, 60 parts of α-Al2O3 powder, 2 parts of zirconia powder, 1 part of iron powder, 1 part of nickel oxide powder and 0.4 part of carboxymethyl cellulose to obtain a composite powder;

[0029] (3) proportioning the above composite powder, the modified binder and water in a mass ratio of 80:30:20, and uniformly mixing to obtain the high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel;

[0030] The high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel prepared in the embodiment is detected to have an average emissivity of 90% after 3h oxidation at 1200°C, and an average infrared absorption rate of 0.84 in the 1-8 micron wave band at high temperature.

[0031] Example 2

[0032] A high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel, characterized in that the preparation method comprises the following steps:

[0033] (1) uniformly mixing sodium water glass and potassium water glass in a mass ratio of 1:3 to obtain a composite water glass, then mixing fly ash, 66% by mass phosphoric acid and water in a mass ratio of 1:0.2:3.1, and stirring under 60°C water bath heating conditions for 1h to obtain a mixed solution A; then mixing the composite water glass and the mixed solution A in a mass ratio of 1:0.2 to obtain a modified binder;

[0034] (2) uniformly mixing 17 parts of glass powder, 9 parts of coal gangue powder, 12 parts of mullite powder, 7 parts of silicon carbide powder, 45 parts of α-Al2O3 powder, 5 parts of zirconia powder, 2 parts of iron powder, 3 parts of nickel oxide powder and 0.7 part of carboxymethyl cellulose to obtain a composite powder;

[0035] (3) proportioning the above composite powder, the modified binder and water in a mass ratio of 80:49:18, and uniformly mixing to obtain the high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel;

[0036] The high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel prepared in the embodiment has an average emissivity of 92% after oxidation at 1200 DEG C for 3 hours, and an average infrared absorption rate of 0.84 in the 1-8 micron wave band at high temperature.

[0037] Example 3

[0038] A preparation method of a high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel, comprising the following steps:

[0039] (1) uniformly mixing sodium water glass and potassium water glass at a mass ratio of 1:7 to obtain a composite water glass, then mixing fly ash, 72% phosphoric acid by mass concentration and water at a mass ratio of 1:0.2:2.4, and stirring the mixture under the condition of 80 DEG C water bath heating for 0.5 hours to obtain a mixed solution A; then mixing the composite water glass and the mixed solution A at a mass ratio of 1:0.3 to obtain a modified binder;

[0040] (2) uniformly mixing 32 parts of glass powder, 6 parts of coal gangue powder, 8 parts of mullite powder, 9 parts of silicon carbide powder, 36 parts of alpha-Al2O3 powder, 3 parts of zirconia powder, 4 parts of iron powder, 2 parts of nickel oxide powder and 0.9 parts of carboxymethyl cellulose to obtain a composite powder;

[0041] (3) proportioning the composite powder, the modified binder and water at a mass ratio of 80:62:13, and uniformly mixing to obtain the high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel;

[0042] The high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel prepared in the embodiment has an average emissivity of 95% after oxidation at 1200 DEG C for 3 hours, and an average infrared absorption rate of 0.86 in the 1-8 micron wave band at high temperature.

[0043] Example 4

[0044] A preparation method of a high-temperature oxidation-resistant, high-heat-absorbing and self-stripping protective coating for nickel alloy steel, comprising the following steps:

[0045] (1) uniformly mixing sodium water glass and potassium water glass at a mass ratio of 1:10 to obtain a composite water glass, then mixing fly ash, 85% phosphoric acid by mass concentration and water at a mass ratio of 1:0.2:1.5, and stirring the mixture under the condition of 65 DEG C water bath heating for 40 minutes to obtain a mixed solution A; then mixing the composite water glass and the mixed solution A at a mass ratio of 1:0.4 to obtain a modified binder;

[0046] (2) 37 parts by mass of glass powder, 5 parts of coal gangue fine powder, 15 parts of mullite fine powder, 5 parts of silicon carbide fine powder, 33 parts of α-Al2O3 micro powder, 1 part of zirconia powder, 3 parts of iron powder, 1 part of nickel oxide powder and 1 part of carboxymethyl cellulose are mixed uniformly to obtain a composite powder;

[0047] (3) The above composite powder, modified binder and water are proportioned at a mass ratio of 80:70:10, and a high-temperature oxidation-resistant, high-heat-absorbing self-stripping protective coating for nickel alloy steel is obtained after mixing uniformly;

[0048] The high-temperature oxidation-resistant, high-heat-absorbing self-stripping protective coating for nickel alloy steel prepared in this example is detected to have an average emissivity of 96% after 3h of oxidation at 1200℃, and an average infrared absorption rate of 0.87 in the high-temperature 1-8 micron wave band.

[0049] Comparative Example 1

[0050] On the basis of Example 1, the difference is that the glass powder is completely replaced by α-Al2O3 micro powder, and the high-temperature oxidation-resistant, high-heat-absorbing self-stripping protective coating for nickel alloy steel is prepared. The coating is detected to have an average emissivity of 65% after 3h of oxidation at 1200℃, and an average infrared absorption rate of 0.71 in the high-temperature 1-8 micron wave band.

[0051] The detection results of this comparative example show that when the glass powder in the protective coating is replaced, the coating layer formed after drying of the coating is difficult to form a dense protective layer at high temperature, greatly reducing the oxidation protection rate of the coating. In addition, there is no longer enough glass liquid phase to wrap silicon carbide at high temperature in the coating, and the silicon carbide will be oxidized, causing the overall infrared absorption rate to decay.

Claims

1. A protective coating for nickel alloy steel, characterized in that: The invention comprises a composite powder, a modified binder and water; the mass ratio of the composite powder, the modified binder and water is 80:(30-70):(10-20); the composite powder comprises, by mass, 15-37 parts of glass powder, 4-9 parts of coal gangue fine powder, 8-15 parts of mullite fine powder, 5-9 parts of silicon carbide fine powder, 33-60 parts of α-Al2O3 micropowder, 1-5 parts of zirconium oxide powder, 1-4 parts of iron powder, 1-3 parts of nickel oxide powder and 0.4-1 part of carboxymethyl cellulose; the modified binder is obtained by mixing sodium potassium composite water glass with a mixed solution A; the mixed solution A is obtained by heating a mixture of fly ash, phosphoric acid and water.

2. The protective coating for nickel alloy steel according to claim 1, characterized in that: The mass ratio of the sodium-potassium composite water glass to the mixed solution A is 1:(0.1-0.4).

3. The protective coating for nickel alloy steel according to claim 1, characterized in that: The mass ratio of the fly ash, phosphoric acid and water is 1:0.2:(1.5-4).

4. The protective coating for nickel alloy steel according to claim 1, characterized in that: The sodium-potassium composite water glass is obtained by uniformly mixing sodium water glass and potassium water glass in a mass ratio of 1: (0.1-10).

5. The protective coating for nickel alloy steel according to claim 4, characterized in that: The modulus of the potassium water glass and the sodium water glass is 3.0-3.

5.

6. The protective coating for nickel alloy steel according to claim 1, characterized in that: The particle sizes of the fly ash, coal gangue fine powder and zirconium oxide powder are less than 45 μm.

7. The protective coating for nickel alloy steel according to claim 1, characterized in that: The SiO2 content of the glass powder is ≤75wt%, and the total content of Na2O and K2O is ≥10wt%; and the particle size of the glass powder is less than 18μm.

8. The protective coating for nickel alloy steel according to claim 1, characterized in that: The SiC content of the silicon carbide fine powder is ≥98wt%; the particle size of the silicon carbide fine powder is less than 45μm; the Fe content of the iron powder is ≥99wt%; the particle size of the iron powder is less than 45μm; the NiO content of the nickel oxide powder is ≥99wt%; and the particle size of the nickel oxide powder is less than 10μm.

9. The protective coating for nickel alloy steel according to claim 1, characterized in that: The Al2O3 content of the α-Al2O3 fine powder is ≥99wt%; and the particle size of the α-Al2O3 fine powder is less than 5μm.

10. A method for preparing the protective coating for nickel alloy steel according to claim 1, characterized in that: The following steps are involved: (1) Sodium water glass and potassium water glass are uniformly mixed in a mass ratio of 1:(0.1-10) to obtain composite water glass, fly ash, phosphoric acid with a mass percentage concentration of 50-85% and water are mixed in a mass ratio of 1:0.2:(1.5-4) and stirred in a water bath at 60-80°C for 0.5-1h to obtain a mixed solution A; the composite water glass and the mixed solution A are then mixed and stirred in a mass ratio of 1:(0.1-0.4) to obtain a modified binder; (2) 15 to 37 parts by mass of glass powder, 4 to 9 parts by mass of coal gangue fine powder, 8 to 15 parts by mass of mullite fine powder, 5 to 9 parts by mass of silicon carbide fine powder, 33 to 60 parts by mass of α-Al2O3 fine powder, 1 to 5 parts by mass of zirconium oxide powder, 1 to 4 parts by mass of iron powder, 1 to 3 parts by mass of nickel oxide powder, and 0.4 to 1 part by mass of carboxymethyl cellulose are mixed to obtain a composite powder; (3) The composite powder, the modified binder and water are prepared in a mass ratio of 80:(30-70):(10-20), and the mixture is evenly mixed to obtain a protective coating for nickel alloy steel.