Protective coating composition, protective coating as well as preparation method and protection method of protective coating

Abstract

The invention provides a protective coating composition, a protective coating as well as a preparation method and a protection method of the protective coating. The protective coating composition is prepared from the following components in parts by weight: 30 to 35 parts of glass powder A, 10 to 15 parts of glass powder B, 1 to 5 parts of bentonite and 19 to 37 parts of high-temperature-resistant filler, wherein the glass powder A is prepared from the following components in parts by weight: 40 to 50 parts of Bi2O3, 25 to 30 parts of B2O3, 5 to 10 parts of ZnO, 5 to 10 parts of K2O, 1 to 3 parts of MgO and 5 to 10 parts of CaO; the glass powder B is prepared from the following components in parts by weight: 20 to 30 parts of SiO2, 2 to 10 parts of Al2O3, 15 to 20 parts of B2O3, 15 to 20 parts of Na2O, 1 to 5 parts of MgO and 5 to 10 parts of CaO; the high-temperature-resistant filler comprises a metal oxide, a disilicon compound and a nitride. The protective coating has good protective property, lubricating property and heat preservation property.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and in particular, to a protective coating composition, a protective coating, a preparation method thereof, and a protection method. Background Art

[0002] In the alloy hot forming process, the use of coatings is a key link to ensure material properties and processing quality. For alloy materials, especially zirconium alloys, they face challenges such as oxidation, hot corrosion at high temperatures, and an increase in deformation resistance. These problems not only affect the material utilization rate but also reduce the surface quality and mechanical properties of the parts after hot forming.

[0003] Zirconium alloys show great potential in nuclear industry and high-temperature environment applications due to their unique corrosion resistance, radiation resistance, and good thermodynamic properties. However, zirconium alloys are extremely prone to reacting with oxygen at high temperatures to form a powdery oxide layer. The initial oxidation temperature of some zirconium alloys is as low as 220°C, and the oxidation phenomenon will significantly intensify above 360°C. Oxidation at high temperatures not only affects the utilization rate of alloy materials but also seriously affects the surface quality of the parts after hot forming.

[0004] Existing protective, lubricating, and heat-insulating coatings generally have problems of insufficient protection and lubrication when dealing with high-temperature environments. Traditional glass protective lubricants can provide protection and lubrication to a certain extent, but their effective temperature range is limited, and it is difficult to maintain stable performance throughout the hot forming temperature range (especially 900 - 1100°C). In addition, the stability of the coating at high temperatures, the adhesion between the coating and the substrate, and the heat-insulating effect during the hot forming process are poor, which all limit their application effects in zirconium alloy hot forming. The instability of the coating at high temperatures will cause it to fail prematurely and lose its protective effect on the alloy, while inefficient lubrication and heat insulation will increase the energy consumption and cost of hot forming and affect production efficiency.

[0005] Therefore, there is an urgent need to develop a coating that still has good protection, lubrication, and heat insulation at high temperatures, so as to be better applied to the alloy material hot forming process, ensure that the surface of the alloy is not easily oxidized, and is easy to remove after the hot forming process. Summary of the Invention

[0006] The main object of the present invention is to provide a protective coating composition, a protective coating, a preparation method thereof, and a protection method to solve the problem of poor protection, lubrication, and heat insulation performance of the coatings used in the alloy hot forming process in the prior art.

[0007] To achieve the above object, according to one aspect of the present invention, a protective coating composition is provided. By weight, the protective coating composition comprises: 30 to 35 parts of glass powder A, 10 to 15 parts of glass powder B, 1 to 5 parts of bentonite, and 19 to 37 parts of high-temperature resistant filler; wherein, by weight, glass powder A comprises 40 to 50 parts of Bi2O3, 25 to 30 parts of B2O3, 5 to 10 parts of ZnO, 5 to 10 parts of K2O, 1 to 3 parts of MgO, and 5 to 10 parts of CaO; by weight, glass powder B comprises 20 to 30 parts of SiO2, 2 to 10 parts of Al2O3, 15 to 20 parts of B2O3, 15 to 20 parts of Na2O, 1 to 5 parts of MgO, and 5 to 10 parts of CaO; the high-temperature resistant filler comprises metal oxides, disilicon compounds, and nitrides.

[0008] Further, by weight, the above protective coating composition comprises: 31 to 33 parts of glass powder A, 10 to 14 parts of glass powder B, 1 to 3 parts of bentonite, and 25 to 35 parts of high-temperature resistant filler.

[0009] Further, the metal oxide is ZrO2 and / or Cr2O3; and / or, by weight, ZrO2 is 2 to 5 parts, and Cr2O3 is 5 to 8 parts; and / or, the disilicon compound is ZrSi2 and / or HfSi2; and / or, by weight, ZrSi2 is 3 to 6 parts, and HfSi2 is 3 to 6 parts; and / or, the nitride is ZrN and / or HfN; by weight, ZrN is 3 to 6 parts, and HfN is 3 to 6 parts.

[0010] Further, the mass ratio of the metal oxide, disilicon compound, and nitride in the high-temperature resistant filler is 8 to 12: 6 to 9: 7 to 11.

[0011] Further, the mass ratio of glass powder A, glass powder B, and high-temperature resistant filler is 3 to 3.2: 1 to 1.2: 2.6 to 3.

[0012] Further, by weight, the protective coating composition further comprises 35 to 40 parts of solvent, 10 to 15 parts of binder, 1 to 2 parts of dispersant, and 1 to 2 parts of thickener; wherein, the solvent is water; and / or, the binder is an aqueous solution of 2 to 5 wt% hydroxyethyl cellulose; and / or, the dispersant is a polyurethane dispersant; and / or, the thickener is a polyurethane thickener and / or a polyvinyl alcohol thickener.

[0013] According to another aspect of the present invention, a protective coating is provided, which is obtained by mixing the protective coating composition, and the protective coating composition is the above-mentioned protective coating composition.

[0014] According to another aspect of the present invention, there is provided a method for preparing the above-mentioned protective coating, which includes: successively ball-milling and standing the raw materials corresponding to the protective coating to obtain the protective coating.

[0015] According to another aspect of the present invention, there is provided a method for protecting the above-mentioned protective coating, which includes: coating the protective coating on the surface of the alloy to obtain the coated alloy, and successively drying and heating the coated alloy to form a protective coating on the surface of the alloy; successively hot-rolling and hot-forging the alloy with the protective coating, and removing the protective coating on the surface of the alloy after the hot-forging ends; wherein, the temperatures of the hot-rolling and the hot-forging are each independently 900-1100 °C.

[0016] Further, the alloy is selected from any one or more of zirconium alloy, zirconium niobium alloy and zirconium titanium alloy; and / or, the times of the hot-rolling and the hot-forging are each independently 120-300 min; and / or, the coating thickness of the protective coating is 0.15-0.35 mm.

[0017] Applying the technical solution of the present invention, the protective coating composition of the present application controls the components and contents within the above ranges, and can have good protection, lubricity and heat preservation at high temperatures of 900-1100 °C, so that it can be better applied to the alloy hot forming process, and the coating is easy to remove without affecting the subsequent treatment of the alloy. Specifically, glass powder A is a bismuth-containing lead-free low-melting glass, which can be rapidly melted into a dense glass film layer at about 400 °C. Especially for the characteristic of the low starting oxidation temperature of zirconium alloy, it can preferentially prevent the oxidation of zirconium alloy, while glass powder B is a high-melting-point aluminosilicate glass, which gradually melts at high temperatures above 900 °C, and can ensure the stability of the film layer at high temperatures. Under the combined action of glass powder A and B, as the temperature of the zirconium alloy continues to rise, the coating can continuously maintain uniformity and density, and has good protection throughout the alloy hot forming process. Bentonite can improve the suspension performance and easy coating property of the protective coating. The above high-temperature resistant fillers can improve the high-temperature resistance and lubricity of the coating. Among them, the metal oxide filler can enhance the high-temperature stability of the coating, and has a certain heat preservation effect, which can slow down the temperature drop during the alloy hot forming process. At the same time, it can also improve the adhesion between the coating and the alloy at high temperatures. The disilicon compound is easy to react with oxygen in the furnace at high temperatures to form a dense SiO2 protective layer, thereby improving the high-temperature protection performance of the coating, and further improving the high-temperature stability of the coating. Nitrides are extremely easy to wet the metal substrate. At the same time, compared with metal oxides, nitrides have a larger expansion coefficient, avoiding the risk of coating peeling off at high temperatures caused by too small expansion coefficient of metal oxide fillers. Description of the Drawings

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 An optical photograph showing the surface state of the zirconium alloy having a protective coating on the surface after hot rolling in Example 1 of the present application is shown;

[0020] Figure 2 An optical photograph showing the surface state of the zirconium alloy coated with a glass protective lubricant after hot rolling in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0022] As analyzed in the background technology of this application, there is a problem in the prior art that the coating used in the alloy hot forming process has poor protection, lubricity and thermal insulation performance at high temperatures. In order to solve the above problems, this application provides a protective coating composition, a protective coating and a preparation method thereof, and a protective method.

[0023] In a typical embodiment of the present application, a protective coating composition is provided, which comprises, by weight: 30 to 35 parts of glass powder A, 10 to 15 parts of glass powder B, 1 to 5 parts of bentonite and 19 to 37 parts of high temperature resistant filler; wherein, by weight, the glass powder A comprises 40 to 50 parts of Bi2O3, 25 to 30 parts of B2O3, 5 to 10 parts of ZnO, 5 to 10 parts of K2O, 1 to 3 parts of MgO and 5 to 10 parts of CaO; by weight, the glass powder B comprises 20 to 30 parts of SiO2, 2 to 10 parts of Al2O3, 15 to 20 parts of B2O3, 15 to 20 parts of Na2O, 1 to 5 parts of MgO and 5 to 10 parts of CaO; and the high temperature resistant filler comprises metal oxides, disiloxane compounds and nitrides.

[0024] The protective coating composition of the present application controls the components and their contents within the above ranges, and can have good protection, lubricity and heat preservation at high temperatures of 900-1100 °C, so that it can be better applied to the alloy hot forming process, and the coating is easy to remove without affecting the subsequent treatment of the alloy. Specifically, glass powder A is a bismuth-containing lead-free low-melting glass, which can quickly melt into a dense glass film layer at about 400 °C. Especially for the characteristic of the low initial oxidation temperature of zirconium alloy, it can preferentially prevent the oxidation of zirconium alloy, while glass powder B is a high-melting-point aluminosilicate glass, which gradually melts at high temperatures above 900 °C, ensuring the stability of the film layer at high temperatures. Under the combined action of glass powder A and B, as the temperature of the zirconium alloy continuously rises, the coating can continuously maintain uniformity and density, and has good protection throughout the alloy hot forming process. Bentonite can improve the suspension performance and easy coating performance of the protective coating. The above high-temperature resistant fillers can improve the high-temperature resistant performance and lubricating performance of the coating. Among them, metal oxide fillers can enhance the high-temperature stability of the coating, and have a certain heat preservation effect, which can slow down the temperature drop during the alloy hot forming process. At the same time, it can also improve the adhesion between the coating and the alloy at high temperatures. Disilicide compounds are easily oxidized by oxygen in the furnace at high temperatures to form a dense SiO2 protective layer, thus improving the high-temperature protection performance of the coating and further enhancing the high-temperature stability of the coating. Nitrides are extremely easy to wet the metal substrate. At the same time, compared with metal oxides, nitrides have a larger expansion coefficient, avoiding the risk of coating peeling off at high temperatures caused by too small expansion coefficient of metal oxide fillers.

[0025] Among them, it is preferred that the particle size of the solid components (glass powder A, glass powder B, bentonite and high-temperature resistant fillers) is 200-400 mesh.

[0026] In order to further improve the protection, lubricity and heat preservation of the protective coating, in an embodiment of the present application, by weight, the above protective coating composition includes: 31-33 parts of glass powder A, 10-14 parts of glass powder B, 1-3 parts of bentonite and 25-35 parts of high-temperature resistant fillers.

[0027] In order to further improve the protection performance and high-temperature resistant performance of the protective coating, in an embodiment of the present application, the metal oxide is ZrO2 and / or Cr2O3; and / or, by weight, ZrO2 is 2-5 parts and Cr2O3 is 5-8 parts; and / or, the disilicide compound is ZrSi2 and / or HfSi2; and / or, by weight, ZrSi2 is 3-6 parts and HfSi2 is 3-6 parts; and / or, the nitride is ZrN and / or HfN; by weight, ZrN is 3-6 parts and HfN is 3-6 parts.

[0028] ZrO2 has an extremely high melting point and good thermal stability. Preferably, its weight fraction is within the above range, which helps to effectively prevent the coating from decomposing in a high-temperature environment and slow down the oxidation of the metal. At the same time, ZrO2 has a low thermal conductivity, which helps to enhance the heat preservation effect of the coating at high temperatures, slow down the temperature drop of the zirconium alloy during the hot forming process, and thus reduce the deformation resistance of the zirconium alloy. Cr2O3 forms a dense oxide protection layer at high temperatures. Preferably, its weight fraction is within the above range, which helps to effectively prevent metal oxidation, thereby improving the protection of the coating. At the same time, it also helps to improve the adhesion between the coating and the metal matrix, so that the coating is not easily peeled off during the hot forming process of the alloy. Under high-temperature conditions, ZrSi2 and HfSi2 have the effect of improving the lubrication of the coating. Preferably, the weight fractions of the two are within the above range, which helps the two to form a silicide layer at high temperatures, thereby effectively preventing the diffusion of oxygen to the metal matrix and improving the oxidation resistance of the coating. ZrN and HfN have excellent high-temperature stability and wear resistance. Preferably, their weight fractions are within the above range, which helps to improve the durability and stability of the coating, and also helps the coating to have good lubrication performance at high temperatures, thereby improving the surface quality of the alloy.

[0029] In an embodiment of the present application, the mass ratio of the metal oxide, disilicide compound, and nitride in the high-temperature resistant filler is 8-12:6-9:7-11.

[0030] Preferably, the mass ratio of the metal oxide, disilicide compound, and nitride in the high-temperature resistant filler is within the above range, which helps to further improve the high-temperature resistance and lubrication performance of the coating, especially to make the coating tightly adhere to the alloy surface at high temperatures and further improve the denseness of the coating.

[0031] Preferably, the mass ratio of HfN and Cr2O3 is 3-3.5:7-7.5, which helps the coating to have appropriate wettability with the alloy at high temperatures, so as to ensure high stability of the coating while also making the coating firmly adhere to the alloy surface.

[0032] In an embodiment of the present application, the mass ratio of glass powder A, glass powder B, and high-temperature resistant filler is 3-3.1:1-1.2:2.8-3.

[0033] Preferably, controlling the mass ratio of glass powder A, glass powder B, and high-temperature resistant filler within the above range helps to enhance the high-temperature stability and heat preservation effect of the coating, and make the coating have appropriate high-temperature viscosity at high temperatures. Appropriate high-temperature viscosity is a key index for the high-temperature lubrication performance of the coating, so that the coating has a comprehensive effect of protection, lubrication, and heat preservation at high temperatures.

[0034] In an embodiment of the present application, by weight parts, the protective coating composition further comprises 35 - 40 parts of a solvent, 10 - 15 parts of a binder, 1 - 2 parts of a dispersant, and 1 - 2 parts of a thickener; wherein, the solvent is water; and / or, the binder is an aqueous solution of hydroxyethyl cellulose with a concentration of 2 - 5 wt%; and / or, the dispersant is a polyurethane dispersant; and / or, the thickener is a polyurethane - type thickener and / or a polyvinyl alcohol - type thickener.

[0035] Preferably, the solvents of the above types and contents help to better disperse the solid components and other components in the solvent, thereby making it have good fluidity. Preferably, the binders of the above types and contents help to enhance the binding force between the components in the protective coating, thereby improving the adhesion between the coating and the metal surface. Preferably, the dispersants of the above types and contents help to improve the dispersibility of the solid components in the solvent, thereby reducing particle agglomeration and obtaining a coating with uniform composition. Preferably, the thickeners of the above types and contents help to make the coating have appropriate viscosity and storage stability, thereby enhancing the comprehensive performance of the coating.

[0036] In another typical embodiment of the present application, a protective coating is provided, which is obtained by mixing the protective coating composition, and the protective coating composition is the above - mentioned protective coating composition.

[0037] The protective coating comprising the above - mentioned protective coating composition can have good protection, lubricity, and heat preservation properties at 200 - 1100 °C, and thus can be better applied to the alloy hot - forming process. The protective coating of the present application can be coated on the surface of a blank at room temperature of 25 °C to 300 °C. In addition, the protective coating of the present application should be stored sealed in a cool and dry place. If there is slight precipitation after long - term storage, it can be used normally after being stirred evenly.

[0038] In yet another typical embodiment of the present application, a preparation method of the above - mentioned protective coating is provided, and the preparation method comprises: successively ball - milling and standing the raw materials corresponding to the protective coating to obtain the protective coating.

[0039] Preferably, the raw materials corresponding to the above - mentioned protective coating are ball - milled in a ball - mill tank until the D50 particle size is 5 - 8 μm and then left standing for 1 day to obtain the protective coating. Among them, the ball - to - material ratio is 5 - 6:1, the rotation speed of the ball - milling is 80 - 100 rpm, and the ball - milling time is 30 - 40 h.

[0040] The protective coating obtained by the above - mentioned preparation method has good protection, lubricity, and heat preservation properties, and thus can be better applied to the alloy hot - forming process, effectively protecting, lubricating, and heat - preserving the alloy at 200 - 1100 °C.

[0041] In yet another typical embodiment of the present application, a protection method for the above-mentioned protective coating is provided. The protection method includes: coating the protective coating on the surface of the alloy to obtain the alloy after coating, drying and heating the alloy after coating in sequence, and forming a protective coating on the surface of the alloy; hot rolling and hot forging the alloy with the protective coating in sequence, and removing the protective coating on the surface of the alloy after the hot forging ends; wherein, the temperature of the hot rolling and the hot forging are each independently 900-1100°C.

[0042] Through the above protection method, a protective coating can be formed on the surface of the alloy, so that the alloy can be effectively protected, lubricated and heat-insulated during the hot forming process and at the temperature of the hot rolling and the hot forging within the above range. Preferably, the heating temperature is 930-1050°C, which helps to better form a protective coating on the surface of the alloy. Using the above coating can prevent the alloy from undergoing thermal corrosion such as oxidation, and increase lubrication and heat insulation through the coating during the hot forming process, thereby reducing the deformation resistance during hot deformation.

[0043] After hot forming, the remaining coating on the surface of the alloy parts can be removed by means such as sandblasting, shot peening and machining.

[0044] In an embodiment of the present application, the alloy is selected from any one or more of zirconium alloy, zirconium niobium alloy and zirconium titanium alloy; and / or, the time of the hot rolling and the hot forging are each independently 120-300 min; and / or, the coating thickness of the protective coating is 0.15-0.35 mm.

[0045] Preferably, the dosage of the protective coating is 0.25-0.55 kg / m 2 , and preferably the coating thickness of the protective coating is within the above range, which helps to form a protective coating on the surface of the above-mentioned type of alloy under the above hot rolling conditions, so as to better protect, lubricate and heat-insulate the alloy.

[0046] The beneficial effects of the present application will be further described below in conjunction with embodiments.

[0047] Example 1

[0048] By weight, the raw materials of the protective coating are: 33 parts of glass powder A, 12 parts of glass powder B, 2 parts of bentonite, 3 parts of ZrO2, 5 parts of ZrSi2, 3 parts of HfSi2, 4 parts of ZrN, 3 parts of HfN, 7 parts of Cr2O3, 40 parts of water, 11 parts of 2wt% hydroxyethyl cellulose aqueous solution, 1 part of polyurethane dispersant, and 1.5 parts of polyurethane thickener. Among them, glass powder A includes 45 parts of Bi2O3, 27 parts of B2O3, 7 parts of ZnO, 7 parts of K2O, 3 parts of MgO, and 8 parts of CaO. Glass powder B includes 25 parts of SiO2, 5 parts of Al2O3, 16 parts of B2O3, 16 parts of Na2O, 4 parts of MgO, and 7 parts of CaO. The particle sizes of glass powder A, glass powder B, bentonite, and high-temperature resistant filler are 200 mesh.

[0049] The raw materials are ball milled in a ball mill tank until the D50 particle size is 6 μm and then left standing for 1 day to obtain the protective coating. Among them, the ball-to-material ratio is 5:1, the rotation speed of the ball mill is 95 rpm, and the ball milling time is 36 h.

[0050] The protective coating is sprayed on the surface of ZrB930-10 zirconium alloy. After drying, it is heated in a furnace at 930 °C together with the zirconium alloy to form a protective coating. After the furnace is removed, the zirconium alloy is hot rolled at 930 °C for 120 min, and after hot rolling, the zirconium alloy is hot forged at 930 °C for 120 min. After hot forging, the protective coating on the surface of the alloy is removed.

[0051] Example 2

[0052] The difference from Example 1 is that the hot rolling temperature is 1050 °C, the hot rolling time is 300 min, the hot forging temperature is 1050 °C, and the hot forging time is 300 min. Finally, the protective coating and the protective coating are obtained.

[0053] Example 3

[0054] By weight, the raw materials of the protective coating are: 30 parts of glass powder A, 15 parts of glass powder B, 1 part of bentonite, 2 parts of ZrO2, 3 parts of ZrSi2, 6 parts of HfSi2, 3 parts of ZrN, 6 parts of HfN, 8 parts of Cr2O3, 35 parts of water, 10 parts of 2wt% hydroxyethyl cellulose aqueous solution, 1 part of polyurethane dispersant, and 2 parts of polyurethane thickener. Among them, glass powder A includes 40 parts of Bi2O3, 30 parts of B2O3, 5 parts of ZnO, 10 parts of K2O, 1 part of MgO, and 10 parts of CaO. Glass powder B includes 20 parts of SiO2, 10 parts of Al2O3, 15 parts of B2O3, 20 parts of Na2O, 1 part of MgO, and 10 parts of CaO. Finally, the protective coating and the protective coating are obtained.

[0055] Example 4

[0056] By weight parts, the raw materials of the protective coating include: 35 parts of glass powder A, 10 parts of glass powder B, 5 parts of bentonite, 5 parts of ZrO2, 6 parts of ZrSi2, 3 parts of HfSi2, 6 parts of ZrN, 3 parts of HfN, 5 parts of Cr2O3, 40 parts of water, 15 parts of 2wt% aqueous hydroxyethyl cellulose solution, 2 parts of polyurethane dispersant and 1 part of polyurethane thickener. Among them, glass powder A includes 50 parts of Bi2O3, 25 parts of B2O3, 10 parts of ZnO, 5 parts of K2O, 3 parts of MgO and 5 parts of CaO. Glass powder B includes 30 parts of SiO2, 2 parts of Al2O3, 20 parts of B2O3, 15 parts of Na2O, 5 parts of MgO and 5 parts of CaO, and finally a protective coating and a protective layer are obtained.

[0057] Example 5

[0058] The difference from Example 1 is that in 25 parts by weight of the high-temperature resistant filler, the mass ratio of metal oxides (ZrO2 and Cr2O3), disilicon compounds (ZrSi2 and HfSi2) and nitrides (ZrN and HfN) is 10:6:9, and finally a protective coating and a protective layer are obtained.

[0059] Example 6

[0060] The difference from Example 1 is that in 25 parts by weight of the high-temperature resistant filler, the mass ratio of metal oxides (ZrO2 and Cr2O3), disilicon compounds (ZrSi2 and HfSi2) and nitrides (ZrN and HfN) is 9:10:6, and finally a protective coating and a protective layer are obtained.

[0061] Example 7

[0062] The difference from Example 1 is that the total weight parts of glass powder A, glass powder B and the high-temperature resistant filler (ZrO2, ZrSi2, HfSi2, ZrN, HfN and Cr2O3) are 70 parts, and the mass ratio of glass powder A, glass powder B and the high-temperature resistant filler is 3:1:3, and finally a protective coating and a protective layer are obtained.

[0063] Example 8

[0064] The difference from Example 1 is that the total weight parts of glass powder A, glass powder B and the high-temperature resistant filler (ZrO2, ZrSi2, HfSi2, ZrN, HfN and Cr2O3) are 70 parts, and the mass ratio of glass powder A, glass powder B and the high-temperature resistant filler is 3:1:2, and finally a protective coating and a protective layer are obtained.

[0065] Example 9

[0066] The difference from Example 1 is that the total weight parts of HfN and Cr2O3 are 10 parts, and the mass ratio of HfN to Cr2O3 is 3.5:7.5, and finally a protective coating and a protective layer are obtained.

[0067] Example 10

[0068] The difference from Example 1 is that the total weight parts of HfN and Cr2O3 are 10 parts, and the mass ratio of HfN to Cr2O3 is 1:1, and finally a protective coating and a protective layer are obtained.

[0069] Comparative Example 1

[0070] The difference from Example 1 is that a glass protective lubricant Ti-1 is coated on the surface of the zirconium alloy. The components of the glass protective lubricant are 90 parts of glass powder (45 parts of SiO2, 20 parts of Al2O3, 5 parts of Na2O, 3 parts of K2O, 1 part of B2O3 and 16 parts of CaO) and 10 parts of kaolin.

[0071] Comparative Example 2

[0072] The difference from Example 1 is that, by weight, the raw materials of the protective coating include: 25 parts of glass powder A, 25 parts of glass powder B, 6 parts of bentonite, 1 part of ZrO2, 2 parts of ZrSi2, 2 parts of HfSi2, 7 parts of ZrN, 7 parts of HfN, 10 parts of Cr2O3, 45 parts of water, 20 parts of a 2wt% aqueous solution of hydroxyethyl cellulose, 3 parts of a polyurethane dispersant and 3 parts of a polyurethane thickener, and finally a protective coating and a protective layer are obtained.

[0073] Comparative Example 3

[0074] The difference from Example 1 is that nitrides ZrN and HfN are not added, and finally a protective coating and a protective layer are obtained.

[0075] Comparative Example 4

[0076] The difference from Example 1 is that disilicides ZrSi2 and HfSi2 are not added, and finally a protective coating and a protective layer are obtained.

[0077] Test method:

[0078] Protective performance test: Coatings with different compositions are respectively coated on the surface of a cylindrical zirconium alloy with a diameter of 20 mm and a height of 20 mm. After natural drying, it is placed in an electric furnace at 1100 °C for heat preservation for 3 h. After taking out and naturally cooling, the oxidized area of the zirconium alloy is measured.

[0079] Lubrication performance test: Coatings with different compositions are respectively applied on the surface of a hollow cylindrical zirconium alloy with an inner diameter of 10 mm, an outer diameter of 20 mm, and a height of 7 mm. After natural drying, it is placed in an electric furnace at 1000 °C for heat preservation for 0.5 h. After taking it out of the furnace and naturally cooling, measure the oxidized area of the zirconium alloy. During the hot deformation process of the zirconium alloy, the ring upsetting method is used to measure its friction coefficient. The specific operation method can refer to the standard: HB 7065-94 Specification for Glass Protective Lubricants for Hot Deformation of Metallic Materials.

[0080] Heat preservation performance test: Coatings with different compositions are respectively applied on the surface of a cylindrical zirconium alloy with a diameter of 20 mm and a height of 20 mm. After natural drying, it is placed in an electric furnace at 1100 °C for heat preservation for 0.5 h. After taking it out of the furnace, quickly measure its temperature drop rate with a thermocouple and a temperature sensor, and record the time required to drop to 800 °C.

[0081] Perform performance tests on the protective coatings of the above examples and comparative examples, and the test results are shown in Table 1.

[0082] Table 1

[0083]

[0084]

[0085] Among them, Figure 1 is an optical photograph of the surface state of the zirconium alloy with a protective coating on its surface in Example 1. As can be seen from Figure 1 , the green protective coating firmly adheres to the surface of the zirconium alloy, and the white part is the oxidized part. It can be seen that most of the zirconium alloy has not been oxidized.

[0086] Figure 2 is an optical photograph of the surface state of the zirconium alloy coated with glass protective lubricant in Comparative Example 1. As can be seen from Figure 2 , the green glass protective lubricant coating hardly exists, and most of the surface of the zirconium alloy is covered with white oxides.

[0087] From the above description, it can be seen that the above embodiments of the present invention achieve the following technical effects:

[0088] The protective coating composition of the present application controls the components and their contents within the above ranges, and can have good protection, lubricity and heat preservation at high temperatures of 900-1100°C. Therefore, it can be better applied to the alloy hot forming process, and the coating is easy to remove without affecting the subsequent treatment of the alloy. Specifically, glass powder A is a bismuth-containing lead-free low-melting glass, which can quickly melt into a dense glass film layer at about 400°C. Especially for the characteristic of the low initial oxidation temperature of zirconium alloy, it can preferentially prevent the oxidation of zirconium alloy, while glass powder B is a high-melting-point aluminosilicate glass, which gradually melts at high temperatures above 900°C, ensuring the stability of the film layer at high temperatures. Under the combined action of glass powder A and B, as the temperature of the zirconium alloy continues to rise, the coating can continuously maintain uniformity and density, and has a good protective effect throughout the alloy hot forming process. Bentonite can improve the suspension performance and easy coating property of the protective coating. The above high-temperature resistant fillers can improve the high-temperature resistance and lubricity of the coating. Among them, metal oxide fillers can enhance the high-temperature stability of the coating, and have a certain heat preservation effect, which can slow down the temperature drop during the alloy hot forming process. At the same time, it can also improve the adhesion between the coating and the alloy at high temperatures. Disilicon compounds are easily reacted with oxygen in the furnace at high temperatures to form a dense SiO2 protective layer, thereby enhancing the high-temperature protection performance of the coating and further enhancing the high-temperature stability of the coating. Nitrides are extremely easy to wet the metal substrate. At the same time, compared with metal oxides, nitrides have a larger expansion coefficient, avoiding the risk of coating peeling off at high temperatures caused by too small expansion coefficient of metal oxide fillers.

[0089] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A protective coating composition, characterized in that: In parts by weight, the protective coating composition comprises: 30-35 parts of glass powder A; 10-15 parts of glass powder B; 1 to 5 parts of bentonite; and 19 to 37 parts of high temperature resistant filler; Wherein, the glass powder A comprises, by weight, 40 to 50 parts of Bi2O3, 25 to 30 parts of B2O3, 5 to 10 parts of ZnO, 5 to 10 parts of K2O, 1 to 3 parts of MgO and 5 to 10 parts of CaO; In parts by weight, the glass powder B comprises 20 to 30 parts of SiO2, 2 to 10 parts of Al2O3, 15 to 20 parts of B2O3, 15 to 20 parts of Na2O, 1 to 5 parts of MgO and 5 to 10 parts of CaO; The high temperature resistant filler includes metal oxides, disiloxane compounds and nitrides.

2. The protective coating composition according to claim 1, characterized in that In parts by weight, the protective coating composition comprises: 31 to 33 parts of the glass powder A; 10 to 14 parts of the glass powder B; 1 to 3 parts of the bentonite; and 25 to 35 parts of the high temperature resistant filler.

3. The protective coating composition according to claim 1 or 2, characterized in that: The metal oxide is ZrO2 and / or Cr2O3; and / or, in parts by weight, the ZrO2 is 2 to 5 parts, and the Cr2O3 is 5 to 8 parts; and / or, the disilicon compound is ZrSi2 and / or HfSi2; and / or, in parts by weight, the ZrSi2 is 3 to 6 parts, and the HfSi2 is 3 to 6 parts; And / or, the nitride is ZrN and / or HfN; in terms of weight, the ZrN is 3 to 6 parts, and the HfN is 3 to 6 parts.

4. The protective coating composition according to any one of claims 1 to 3, characterized in that The mass ratio of the metal oxide, the disiloxane compound and the nitride in the high temperature resistant filler is 8-12:6-9:7-11.

5. The protective coating composition according to any one of claims 1 to 4, characterized in that The mass ratio of the glass powder A, the glass powder B and the high temperature resistant filler is 3-3.2:1-1.2:2.6-3.

6. The protective coating composition according to any one of claims 1 to 5, characterized in that The protective coating composition further comprises, by weight, 35 to 40 parts of a solvent, 10 to 15 parts of a binder, 1 to 2 parts of a dispersant and 1 to 2 parts of a thickener; Wherein, the solvent is water; and / or the binder is a 2-5wt% hydroxyethyl cellulose aqueous solution; and / or the dispersant is a polyurethane dispersant; and / or the thickener is a polyurethane thickener and / or a polyvinyl alcohol thickener.

7. A protective coating obtained by mixing a protective coating composition, characterized in that: The protective coating composition is the protective coating composition according to any one of claims 1 to 6.

8. A method for preparing the protective coating according to claim 7, characterized in that: The preparation method comprises: The raw materials corresponding to the protective coating are ball-milled and allowed to stand in sequence to obtain the protective coating.

9. A protective method for the protective coating according to claim 7, characterized in that: The protection method includes: Applying a protective coating on the surface of the alloy to obtain a coated alloy, and sequentially drying and heating the coated alloy to form a protective coating on the surface of the alloy; hot rolling and hot forging the alloy having the protective coating in sequence, and removing the protective coating on the surface of the alloy after the hot forging is completed; Wherein, the temperature of the hot rolling and the hot forging are independently 900-1100°C.

10. The protection method according to claim 9, characterized in that: The alloy is selected from any one or more of zirconium alloy, zirconium-niobium alloy and zirconium-titanium alloy; and / or the time of hot rolling and the time of hot forging are each independently 120 to 300 minutes; and / or the coating thickness of the protective coating is 0.15 to 0.35 mm.

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