Corrosion coating material, coating, preparation method and application

Abstract

The invention belongs to the technical field of heat-engine plant unit circulation component surface corrosion prevention, and discloses a high-temperature-corrosion-resistant coating material, a coating and a preparation method and application thereof.The preparation method comprises the steps that by mass, 10%-20% of Cr, 1%-5% of Ni, 2%-10% of Fe, 10%-30% of molybdenum, 20%-40% of copper and 10%-20% of silicon are mixed to be uniform, a pipeline is embedded, heat treatment is conducted, and an initial chromium-rich infiltrated layer is formed; and then nitriding treatment is conducted on the initial chromium-rich nitriding layer, and the high-temperature-corrosion-resistant chromium-nitrogen composite coating is formed. The added silicon can form silicides in the coating, and the silicides can prevent the corrosion medium from permeating, so that the corrosion process is slowed down or prevented; the added molybdenum can effectively improve the stability of the composite coating in a corrosion medium rich in sulfate ions; and the added copper can form a protective layer consisting of copper sulfide or copper oxide on the surface of the steel, so that the corrosion of a corrosive medium is effectively prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of surface corrosion protection of circulating components of thermal power plant units, and in particular relates to a corrosion coating material, a coating, a preparation method and an application thereof. Background Art

[0002] The petrochemical industry is facing the requirements of large-scale equipment, inferior crude oil, safety, green and environmental protection. The annual demand for steel exceeds 10 million tons, of which flow components account for about 25-30%, with an annual demand of up to 2.5-3 million tons. The number of leaks caused by corrosion problems reaches 1,000 times each year, and the economic loss exceeds 70 billion yuan. Therefore, through further technical research and development and improvement, a series of corrosion-resistant coating technologies will be expanded to the petrochemical field with a larger market scale and demand, and at the same time strive to open up the market in the fields of aerospace, vehicles and ships, and nuclear industry to meet the urgent needs of surface strengthening and protection of key components in multiple scenarios and complex extreme working conditions. It has significant engineering application value and broad prospects for promotion and application.

[0003] The material selection for power plant boiler pipes has an important impact on their corrosion resistance. Different materials have different corrosion resistance. If the selected material has poor corrosion resistance, it is easy to corrode in harsh environments.

[0004] In the prior art, nickel-tantalum alloy materials are used as boiler pipe coatings, which can significantly improve the pipe interface bonding strength and form a dense Cr 2 O 3 The coating is used to improve the corrosion resistance, thereby extending the service life of the pipeline and reducing the risk of pipe burst accidents. However, due to the high hardness and strength of nickel-tantalum alloy, it is difficult to process. When preparing the coating, advanced processing technology and equipment are required to ensure the uniformity and density of the coating. This may increase the processing cost and processing time, and also have high requirements on the skill level of the processing personnel.

[0005] Boiler pipes are mostly made of austenitic steel. To improve the corrosion resistance of austenitic steel, grain refinement and inner wall shot peening technology are generally used. These two technologies change the inner wall structure of the pipe, allowing the alloy to quickly grow the Cr required for oxidation resistance. 2 O 3 But Cr 2 O 3The stability in steam above 600℃ is poor, and the loose oxide film caused by volatile products will cause the oxide film to peel off, and further lead to pipe blockage and pipe explosion accidents; in addition, the Cr content in the alloy matrix is ​​relatively low. As the service time increases, when the Cr content required for the growth of the oxide film cannot be replenished, the oxidation resistance of the alloy will also drop sharply. Therefore, the two technologies can only improve the corrosion resistance of the alloy in a short period of time at the beginning of service, and cannot fundamentally solve the problems of alloy oxidation and oxide film peeling. Summary of the invention

[0006] In order to overcome the problem of poor corrosion resistance in the prior art, the purpose of the present invention is to provide a corrosion coating material, coating, preparation method and application. The coating prepared by this method can make the metal material show excellent performance in high temperature resistance, corrosion resistance, wear resistance, fatigue resistance, etc., thereby improving reliability and extending service life.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A corrosion coating material comprises, by mass percentage, 10-20% Cr, 1-5% Ni, 2-10% Fe, 10-30% Mo, 20-40% Cu and 10-20% Si.

[0009] A further improvement of the present invention is that, by mass percentage, it includes 15-20% Cr, 1-5% Ni, 2-5% Fe, 10-20% Mo, 30-40% Cu and 15-20% Si.

[0010] A method for preparing a high temperature corrosion resistant coating comprises the following steps:

[0011] By mass percentage, 10-20% of Cr, 1-5% of Ni, 2-10% of Fe, 10-30% of Mo, 20-40% of Cu and 10-20% of Si are uniformly mixed to obtain a mixed powder;

[0012] The mixed powder is embedded in the pipe, and heat treated in an inert atmosphere to form an initial coating on the surface of the pipe;

[0013] The initial coating formed on the substrate is nitrided to form a high temperature corrosion resistant coating on the substrate.

[0014] A further improvement of the present invention is that 10-20% Cr, 1-5% Ni, 2-10% Fe, 10-30% Mo, 20-40% Cu and 10-20% Si are uniformly mixed and the mixture is subjected to wet ball milling.

[0015] A further improvement of the present invention is that the surface of the pipeline is pretreated before the mixed powder is embedded in the pipeline.

[0016] A further improvement of the present invention is that the heat treatment temperature is 900-1300° C. and the time is 24-60 hours.

[0017] A further improvement of the present invention is that the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.

[0018] A further improvement of the present invention is that the nitriding treatment is performed by a gas nitriding method.

[0019] A high temperature corrosion resistant coating.

[0020] The invention discloses an application of a high temperature corrosion resistant coating in circulation components of a thermal power unit.

[0021] Compared with the prior art, the present invention has at least the following beneficial effects:

[0022] In the present invention, an initial chromium-rich diffusion layer is formed on the surface of the pipeline by pre-chromization treatment. Chromium can form a dense chromium oxide film (Cr 2 O 3 This film is very stable and can effectively prevent further corrosion on the pipe surface. Even when there are wounds or cracks on the pipe surface, the chromium atoms in the matrix can be replenished in time and combined with oxygen atoms in the air to form a protective chromium oxide film (Cr 2 O 3 ), thereby preventing further oxidation. During the chromizing process, active chromium atoms diffuse into the matrix and form substitutional solid solutions with iron atoms. The chromium atoms and the surrounding iron atoms deviate from the equilibrium position of their crystal lattices and are in a high-energy activation state, thereby promoting the replacement of high-energy iron atoms by nitrogen atoms in the subsequent nitriding process, increasing the nitriding speed and the thickness of the nitrided layer. Nitrogen can also form CrN or Cr with chromium. 2 N, compared with a single chromium-rich or nitrogen-rich layer, has better wear resistance and high-temperature corrosion resistance. In addition, in the present invention, by adding nickel to the infiltrant, a dense NiO oxide film is formed on the alloy surface. This film can effectively isolate the corrosive medium and protect the pipeline from corrosion. This protective film can also maintain good stability in extreme environments, thereby extending the service life of the pipeline; by adding molybdenum, the stability of the coating in corrosive media rich in sulfate ions is improved; by adding copper, an additional protective layer is formed on the pipeline surface, such as copper sulfide (Cu 2S) or copper oxide layer, these protective layers are more corrosion-resistant than the pipeline itself, thus effectively preventing further erosion by the corrosive medium; by adding silicon, silicides are formed in the coating, which can hinder the penetration of corrosive media (such as oxygen, water, etc.), thereby slowing down or preventing the occurrence of the corrosion process, and silicon can enhance the oxidation resistance of the pipeline, making it less likely to undergo oxidation reactions in high temperature or oxidizing environments, thereby maintaining its stability and durability; the solid solution strengthening effect of silicon can refine the grains of the pipeline and improve the strength and hardness of the pipeline. At the same time, fine grains also help to improve the fatigue resistance and corrosion resistance of the pipeline. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a cross-sectional morphology photograph of a tough high-temperature steam oxidation resistant coating prepared under the parameters of Example 1 of the present invention;

[0024] Figure 2 This is a cross-sectional morphology photograph of a tough high-temperature steam oxidation resistant coating prepared under the parameters of Example 2 of the present invention;

[0025] Figure 3 This is a cross-sectional morphology photograph of a tough high-temperature steam oxidation resistant coating prepared under the parameters of Example 3 of the present invention;

[0026] Figure 4 The distribution of Fe, Cr and N elements in the tough high-temperature steam oxidation resistant coating prepared under the parameters of Example 4 of the present invention. DETAILED DESCRIPTION

[0027] In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

[0028] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0029] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0030] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, an electrical connection, or a communication; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0031] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0032] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0033] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0034] It should be further understood that the term "and / or" used in the present description and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0035] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0036] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] The pipeline in the present invention is an austenitic steel pipeline, and the material is: TP304H, TP347H, Super304H, TP347HFG, HR3C or nickel-iron based alloy.

[0038] The method for preparing the high temperature corrosion resistant coating of the present invention comprises the following steps:

[0039] By mass percentage, 10-20% of Cr, 1-5% of Ni, 2-10% of Fe, 10-30% of Mo, 20-40% of Cu and 10-20% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0040] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0041] The mixed powder is embedded in the pipeline and heat treated at 900-1300°C for 24-60h under an inert atmosphere (nitrogen or argon) to form an initial coating on the pipeline surface;

[0042] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0043] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0044] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 500-600Pa, introduce flowing ammonia to make the pressure in the furnace 200-600Pa.

[0045] Heating and insulation: Heat the furnace to raise the pipe surface temperature to the nitriding temperature range (500-600℃). Keep it at this temperature for 48-100 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0046] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0047] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0048] The high temperature corrosion resistant coating prepared by the method of the present invention can be applied in the circulation components of thermal power units.

[0049] High temperature corrosion resistance: In a 600℃ pure water vapor environment, the weight gain of the coating is 0.0134mg / cm2 after 1000h of oxidation corrosion. 2 , and its corrosion rate is 1.4×10 -5 mg / (cm 2 h), the weight gain of the base material is 0.7935 mg / cm 2 , and its corrosion rate is 8.3×10 -4 mg / (cm 2 ·h). The high temperature corrosion resistance of the coating is 49 times higher than that of the base material. In a 650℃ pure water vapor environment for 1000h, the weight gain of the coating is 0.0507mg / cm 2 , and its corrosion rate is 5.8×10 -5 mg / (cm 2 h), the weight gain of the base material is 3.3951 mg / cm 2 , the corrosion rate is 3.5×10 -3 mg / (cm 2 h). The high temperature corrosion resistance of the coating is 166 times higher than that of the base material.

[0050] Example 1

[0051] The material of austenitic steel pipe is TP347H.

[0052] In terms of mass percentage, 10% of Cr, 5% of Ni, 10% of Fe, 30% of Mo, 30% of Cu and 15% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0053] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0054] The mixed powder is embedded in the pipe and heat treated at 900°C for 60 h in an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0055] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0056] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0057] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 500Pa, introduce flowing ammonia to make the pressure in the furnace 200Pa.

[0058] Heating and insulation: Heat the furnace to raise the pipe surface temperature to the nitriding temperature of 600°C. Keep it at this temperature for 48 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0059] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0060] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0061] See also Figure 1 It can be seen that the total thickness of the prepared high-temperature corrosion-resistant coating is about 30 μm, the infiltration layer has a dense structure, uniform thickness, and good metallurgical bonding with the substrate.

[0062] Example 2

[0063] The material of austenitic steel pipe is TP347H.

[0064] According to mass percentage, 20% of Cr, 1% of Ni, 2% of Fe, 17% of Mo, 40% of Cu and 20% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0065] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0066] The mixed powder is embedded in the pipe and heat treated at 1300°C for 24 h under an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0067] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0068] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0069] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 520Pa, introduce flowing ammonia to make the pressure in the furnace 500Pa.

[0070] Heating and insulation: Heat the furnace body to raise the pipe surface temperature to the nitriding temperature of 500°C. Keep it at this temperature for 100 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0071] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0072] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0073] See also Figure 2 It can be seen that the total thickness of the prepared high-temperature corrosion-resistant coating is about 50 μm, the infiltration layer has a dense structure, uniform thickness, and good metallurgical bonding with the substrate.

[0074] Example 3

[0075] The material of austenitic steel pipe is Super304H.

[0076] In terms of mass percentage, 15% of Cr, 3% of Ni, 2% of Fe, 30% of Mo, 30% of Cu and 20% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0077] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0078] The mixed powder is embedded in the pipe and heat treated at 1000°C for 30 h in an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0079] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0080] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0081] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 550Pa, introduce flowing ammonia to make the pressure in the furnace 400Pa.

[0082] Heating and insulation: Heat the furnace body to raise the pipe surface temperature to the nitriding temperature of 570°C. Keep it at this temperature for 60 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0083] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0084] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0085] See also Figure 3It can be seen that the total thickness of the prepared high-temperature corrosion-resistant coating is about 34 μm, the infiltration layer has a dense structure, uniform thickness, and good metallurgical bonding with the substrate.

[0086] Example 4

[0087] The material of austenitic steel pipe is TP347HFG.

[0088] According to mass percentage, 20% of Cr, 5% of Ni, 5% of Fe, 10% of Mo, 40% of Cu and 20% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0089] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0090] The mixed powder is embedded in the pipe and heat treated at 1100°C for 40 h in an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0091] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0092] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0093] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 600Pa, introduce flowing ammonia to make the pressure in the furnace 600Pa.

[0094] Heating and insulation: Heat the furnace to raise the pipe surface temperature to the nitriding temperature of 550°C. Keep it at this temperature for 65 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0095] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0096] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0097] See also Figure 4It can be seen that due to the surface activation of pre-chromizing, strong diffusion occurs between N and the Cr-rich layer during the nitriding process, replacing the high-energy Fe atoms in the Fe-Cr diffusion layer formed during the chromizing process to form a Cr-N composite coating. The Cr / N ratio in the Cr-N composite coating is 60% and 25%, respectively, and does not change with the change of coating thickness. As the distance from the coating surface increases, the content of Cr and N atoms decreases in a gradient until it reaches the inside of the alloy matrix. At the same time, a certain concentration of Fe and other atoms in the matrix alloy are found in the coating, and the concentration of Fe atoms gradually increases from the outside to the inside.

[0098] Example 5

[0099] The material of austenitic steel pipe is HR3C.

[0100] According to mass percentage, 20% of Cr, 5% of Ni, 5% of Fe, 00% of Mo, 30% of Cu and 20% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0101] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0102] The mixed powder is embedded in the pipe and heat treated at 1200°C for 50 h in an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0103] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0104] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0105] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 570Pa, introduce flowing ammonia to make the pressure in the furnace 300Pa.

[0106] Heating and insulation: Heat the furnace body to raise the pipe surface temperature to the nitriding temperature of 620°C. Keep it at this temperature for 90 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0107] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0108] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0109] Example 6

[0110] Austenitic steel pipes are made of a nickel-iron based alloy.

[0111] According to mass percentage, 20% of Cr, 1% of Ni, 2% of Fe, 20% of Mo, 40% of Cu and 17% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0112] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0113] The mixed powder is embedded in the pipe and heat treated at 1250°C for 55 h under an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0114] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0115] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0116] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 580Pa, introduce flowing ammonia to make the pressure in the furnace 450Pa.

[0117] Heating and insulation: Heat the furnace to raise the pipe surface temperature to the nitriding temperature of 580°C. Keep it at this temperature for 50 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0118] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0119] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0120] Example 7

[0121] The material of austenitic steel pipe is Super304H.

[0122] In terms of mass percentage, 15% of Cr, 5% of Ni, 5% of Fe, 20% of Mo, 40% of Cu and 15% of Si are mixed uniformly by wet ball milling to obtain a mixed powder;

[0123] Pre-treat the pipeline surface to remove impurities and oil stains on the surface;

[0124] The mixed powder is embedded in the pipe and heat treated at 1050°C for 45h under an inert atmosphere (nitrogen or argon) to form an initial coating on the pipe surface;

[0125] The initial coating formed on the pipeline is nitrided by gas nitriding to form a high temperature corrosion resistant coating on the substrate. The specific process is as follows:

[0126] Furnace loading: Place the pretreated pipe into the nitriding furnace, close the furnace door and seal it.

[0127] Vacuuming and introducing ammonia: Start the vacuum system, extract the air in the furnace, and after reaching a vacuum degree of 600Pa, introduce flowing ammonia to make the pressure in the furnace 550Pa.

[0128] Heating and insulation: Heat the furnace body to raise the pipe surface temperature to the nitriding temperature of 670°C. Keep it at this temperature for 60 hours to thermally decompose the ammonia to produce active nitrogen atoms.

[0129] Nitriding reaction: Active nitrogen atoms are continuously adsorbed onto the surface of the pipe and diffuse into the coating on the surface of the pipe.

[0130] Cooling: After nitriding is completed, turn off the heating system and let the pipe cool naturally in the furnace to avoid excessive thermal stress and deformation.

[0131] The silicon added in the present invention can form silicides in the coating, which can hinder the penetration of corrosive media, thereby slowing down or preventing the occurrence of the corrosion process; the added molybdenum can effectively improve the stability of the composite coating in corrosive media rich in sulfate ions; the added copper can form a layer of copper sulfide (Cu 2 S) or copper oxide, thereby effectively preventing further erosion by corrosive media.

[0132] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the attached claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention. Any figure mark in the claims should not be regarded as limiting the claims involved.

[0133] In addition, it should be understood that although this specification is described in accordance with the implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. The above content is only to illustrate the technical idea of ​​the present invention, and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A corrosion coating material, characterized in that: By mass percentage, it includes 10-20% Cr, 1-5% Ni, 2-10% Fe, 10-30% Mo, 20-40% Copper and 10-20% Silicon.

2. The corrosion coating material according to claim 1, characterized in that: By mass percentage, it includes 15-20% Cr, 1-5% Ni, 2-5% Fe, 10-20% Mo, 30-40% Copper and 15-20% Silicon.

3. A method for preparing a high temperature corrosion resistant coating, characterized in that: The following steps are involved: By mass percentage, 10-20% of Cr, 1-5% of Ni, 2-10% of Fe, 10-30% of Mo, 20-40% of Cu and 10-20% of Si are uniformly mixed to obtain a mixed powder; The mixed powder is embedded in the pipe, and heat treated in an inert atmosphere to form an initial coating on the surface of the pipe; The initial coating formed on the substrate is nitrided to form a high temperature corrosion resistant coating on the substrate.

4. The method for preparing the high temperature corrosion resistant coating according to claim 3, characterized in that: 10-20% Cr, 1-5% Ni, 2-10% Fe, 10-30% Mo, 20-40% Cu and 10-20% Si are uniformly mixed and the mixture is milled by wet ball milling.

5. The method for preparing the high temperature corrosion resistant coating according to claim 3, characterized in that: Before embedding the mixed powder into the pipe, the pipe surface is pretreated.

6. The method for preparing the high temperature corrosion resistant coating according to claim 3, characterized in that: The heat treatment temperature is 900-1300°C and the time is 24-60h.

7. The method for preparing the high temperature corrosion resistant coating according to claim 3, characterized in that: The inert atmosphere is an argon atmosphere or a nitrogen atmosphere.

8. The method for preparing the high temperature corrosion resistant coating according to claim 3, characterized in that: The nitriding treatment is carried out by a gas nitriding method.

9. A high temperature corrosion resistant coating prepared according to the method according to any one of claims 3 to 8.

10. Use of a high temperature corrosion resistant coating prepared according to the method according to any one of claims 3 to 8 in circulation components of a thermal power unit.

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