Chromium-nickel co-diffusion coating, preparation method therefor and use thereof

Abstract

The present disclosure provides a chromium-nickel co-diffusion coating, a preparation method therefor and a use thereof. The preparation method comprises: performing surface pretreatment on a metal workpiece; performing shot peening treatment on the pretreated metal workpiece; and applying chromium-nickel co-diffusion slurry in a single step to the surface of the shot-peened metal workpiece, and performing drying, curing, and sintering treatment to obtain a chromium-nickel co-diffusion coating on the surface of the metal workpiece, wherein the chromium-nickel co-diffusion slurry comprises solid-phase components and liquid-phase components; the solid-phase components include chromium powder, nickel powder, aluminum oxide, and chromium oxide; and the liquid-phase components include Al(H2PO4)3, sodium silicate, ammonium iodide, chromium oxide, and magnesium oxide. The coating is suitable for various metal workpieces requiring surface strengthening, including those made of carbon steel, austenitic stainless steel, high-temperature alloys, etc. The coating features a wide range of applications and extremely high practicability. Moreover, the coating has strong adhesion and can improve the high- and low-temperature corrosion resistance and steam oxidation resistance of metal workpieces.

Description

A chromium-nickel co-diffusion coating, its preparation method, and its application.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410975833.3, filed on July 19, 2024, entitled "Chromium-Nickel Co-diffusion Coating and its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure belongs to the field of material surface coating technology, specifically relating to a chromium-nickel co-diffusion coating and its preparation method and application. Background Technology

[0004] The most common method for corrosion protection of metal workpieces is to apply a protective layer of metal, non-metal, or metal-non-metal composite film to the metal surface through physical, chemical, or electrochemical surface treatment processes. This prevents or slows down the chemical reaction between the metal and the medium it comes into contact with. Related metal surface treatment technologies include thermal spraying, electroplating, thermal diffusion, surface phosphating, and metal or non-metal coatings. By creating a coating on the workpiece surface, the composition, microstructure, and composition of the material surface are altered, improving surface properties, enhancing the workpiece's corrosion and wear resistance, and extending its service life.

[0005] Thermal diffusion technology uses heat to diffuse metallic or non-metallic elements into the surface of a metal workpiece, forming a surface alloy layer. Co-diffusion is the most widely used process in thermal diffusion, where multiple elements are simultaneously diffused into the workpiece surface through a single heating diffusion process. Co-diffusion combines the advantages of various single-element diffusion methods, compensating for the shortcomings of single-element diffusion through element combination, resulting in better overall performance of the workpiece surface.

[0006] Currently, there are co-diffusion methods based on metallic elements, co-diffusion based on non-metallic elements, and rare earth co-diffusion. For example, aluminum-chromium co-diffusion is used on the surface of high-temperature alloy workpieces to form a dense oxide film, utilizing the stable physicochemical properties of the oxides at high temperatures to improve the service life of the workpiece. However, most current co-diffusion methods for metal workpieces use solid-state methods, requiring the compounding of multiple metallic elements and catalysts. The co-diffusion time is long, the experimental requirements are high, and the resulting coating has poor adhesion and thinness, requiring multiple coatings to achieve the required thickness, thus limiting its applicability. Especially for metal workpieces such as high-carbon steel and high-alloy steel, during the element diffusion process, due to the different diffusion rates of Cr or Al and Fe, there is a Kirkendall effect in atomic diffusion. During the diffusion of Cr or Al, voids appear, resulting in a large number of pores in the coating, making the coating less dense, increasing brittleness, and even causing the coating to peel off, seriously affecting its performance. Secondly, a gas method is also used, in which an aluminum-chromium co-diffusion agent composed of alumina, chromium powder, aluminum powder, and ammonium chloride is composed. The chromium-aluminum co-diffusion agent and the part are placed in a crucible and heated under an argon atmosphere to obtain a part with an aluminum-chromium coating. This method requires a vacuum environment and strict control of the preparation process. In addition, a neutral salt bath chromium-aluminum co-diffusion method is used, in which a co-diffusion agent composed of sodium chloride, barium chloride, sodium fluoride, aluminum powder, and chromium powder is composed. The co-diffusion agent is loaded into a crucible, which is then placed in a resistance furnace and heated. The sample is then placed in a prepared chromium-aluminum co-diffusion salt bath, ensuring that the main working surface of the sample is as perpendicular as possible to the salt bath flow direction. After holding at this temperature for 4 hours, the sample is removed and oil-quenched, thus obtaining a chromium-aluminum co-diffusion layer on the surface of the nickel-based superalloy. This method has a longer holding time, requires precise sample placement, and results in a thinner coating, only about 20 μm thick, with poor corrosion and wear resistance.

[0007] Summary of the Invention

[0008] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a chromium-nickel co-diffusion coating, its preparation method, and its application.

[0009] In one aspect, this disclosure provides a method for preparing a chromium-nickel co-diffusion coating, the method comprising:

[0010] Surface pretreatment of metal workpieces;

[0011] Shot peening is performed on the pretreated metal workpiece.

[0012] A chromium-nickel co-diffusion slurry is applied in one step to the surface of a shot-peened metal workpiece, followed by drying, curing, and sintering to obtain a chromium-nickel co-diffusion coating on the metal workpiece surface; wherein...

[0013] The chromium-nickel co-diffusion slurry comprises a solid phase component and a liquid phase component; the solid phase component comprises chromium powder, nickel powder, alumina and chromium oxide, and the liquid phase component comprises Al(H2PO4)3, water glass, ammonium iodide, chromium oxide and magnesium oxide.

[0014] Optionally, the solid-liquid ratio of the solid phase component to the liquid phase component is 10:(1-5).

[0015] Optionally, the solid phase component comprises, by mass percentage:

[0016] 50-80% chromium powder;

[0017] 1-10% nickel powder;

[0018] 10-20% aluminum oxide;

[0019] 0-20% chromium oxide;

[0020] The sum of the mass percentages of the above solid components is 100%.

[0021] Optionally, the chromium powder, nickel powder, alumina, and chromium oxide are ball-milled at a speed of 350-400 r / min for 6-24 h to obtain a solid phase component.

[0022] Optionally, the liquid phase component comprises, by mass percentage:

[0023] 10-30% Al(H2PO4)3;

[0024] 15-25% water glass;

[0025] 5-10% ammonium iodide;

[0026] 10-40% chromium oxide;

[0027] 15-35% magnesium oxide;

[0028] The sum of the mass percentages of the above liquid phase components is 100%.

[0029] Optionally, the coating thickness of the chromium-nickel co-diffusion slurry applied to the surface of the metal workpiece is 0.1 to 1.0 mm.

[0030] Optionally, in shot peening, the diameter of the shot particles is 0.1-1.0 mm, the shot peening pressure is 0.5-2.0 MPa, and the shot peening time is 10-30 min.

[0031] Optionally, the metal workpiece coated with chromium-nickel co-diffusion slurry is subjected to drying, curing, and sintering treatment, including:

[0032] The metal workpiece coated with chromium-nickel co-diffusion slurry is pre-dried at 60-85℃ for 5-30 minutes, then dried at 100-160℃ for 30-60 minutes, and finally cured at 250-300℃ for 20-60 minutes.

[0033] The dried and cured metal workpiece is sintered at 500-650℃ for 5-30 minutes.

[0034] In another aspect of this disclosure, a chromium-nickel co-diffusion coating is provided, prepared according to the preparation method described above.

[0035] Another aspect of this disclosure proposes an application of a chromium-nickel co-diffusion coating, wherein the chromium-nickel co-diffusion coating described above is applied to the surface of metal workpieces made of carbon steel, austenitic steel and high-temperature alloys.

[0036] This disclosure provides a chromium-nickel co-diffusion coating, its preparation method, and its application. The preparation method includes: pre-treating the surface of a metal workpiece; shot-peening the pre-treated metal workpiece; applying a chromium-nickel co-diffusion slurry to the shot-peened surface of the metal workpiece in a single application; and then drying, curing, and sintering to obtain the chromium-nickel co-diffusion coating on the surface of the metal workpiece. The chromium-nickel co-diffusion slurry comprises a solid phase component and a liquid phase component. The solid phase component includes chromium powder, nickel powder, alumina, and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide, and magnesium oxide. This coating is suitable for various metal workpieces requiring surface strengthening, including carbon steel, austenitic stainless steel, and high-temperature alloys. It has a wide range of applications and is highly practical. The coating exhibits strong adhesion and can further improve the resistance of metal workpieces to high and low temperature corrosion and steam oxidation. Attached Figure Description

[0037] Figure 1 is a flowchart of a method for preparing a chromium-nickel co-diffusion coating according to an embodiment of the present disclosure;

[0038] Figure 2 is an electron microscope image of the chromium-nickel co-diffusion coating prepared in Example 3 of this disclosure. Detailed Implementation

[0039] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some, not all, of the embodiments of this disclosure. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0040] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing a chromium-nickel co-diffusion coating, specifically including the following steps S110-S130:

[0041] S110. Perform surface pretreatment on the metal workpiece.

[0042] Specifically, organic reagents such as alcohol or acetone are used to clean oil stains and dust from the surface of metal workpieces. At the same time, steel brushes, sandpaper, or polishing can be used to remove oxide scale from the surface of metal workpieces.

[0043] It should be noted that this embodiment does not specifically limit the material and type of the metal workpiece. For example, it can be a high-temperature alloy metal workpiece, various types of carbon steel metal workpieces, or austenitic steel metal workpieces. Of course, such metal workpieces can be pipe workpieces, turbine blades in the aerospace field, or other types of workpieces.

[0044] S120. Perform shot peening on the pretreated metal workpiece.

[0045] Specifically, in the shot peening process, shot peening particles are sprayed at high speed onto the surface of a metal workpiece, causing plastic deformation of its surface layer and forming a reinforced layer of a certain thickness. The shot peening particles have a diameter of 0.1-1.0 mm, the shot peening pressure is 0.5-2.0 MPa, and the shot peening time is 10-30 min.

[0046] In this embodiment, by activating the surface of the metal workpiece, the physical properties such as adhesion, roughness, and specific surface area, as well as the bonding strength, are improved. This is beneficial to increasing the adhesion of the subsequent penetrating coating, further improving the penetration effect of the subsequent co-penetrating coating, and making the coating thickness thicker.

[0047] S130. A chromium-nickel co-diffusion slurry is applied to the surface of a metal workpiece after shot peening, followed by drying, curing, and sintering to obtain a chromium-nickel co-diffusion coating on the surface of the metal workpiece.

[0048] It should be noted that this embodiment does not specifically limit the method of coating the chromium-nickel co-diffusion slurry onto the surface of the metal workpiece. For example, the chromium-nickel co-diffusion slurry can be coated onto the surface of the metal workpiece by spraying or brushing.

[0049] It should be further noted that the currently prepared chromium-aluminum co-diffusion coating is relatively thin, requiring multiple coatings to increase the coating thickness, and has poor stability. In contrast, this embodiment eliminates the need for multiple coatings; a single coating process is sufficient to achieve the desired thickness, and the coating thickness can be adjusted according to actual needs.

[0050] Specifically, in this embodiment, the chromium-nickel co-diffusion slurry is applied to a suitable thickness in a single coating process, without the need for multiple layers. The coating thickness of the chromium-nickel co-diffusion slurry is 0.1–1.0 mm. In other words, this embodiment applies the chromium-nickel co-diffusion slurry to the surface of the metal workpiece in a single application, forming a chromium-nickel co-diffusion coating with a thickness of 0.1–1.0 mm. Within this thickness range, both the applicability of the metal workpiece and its high-temperature corrosion resistance are ensured.

[0051] In some alternative embodiments, the slurry coating thickness of the chromium-nickel co-diffusion coating is 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1.0 mm, etc.

[0052] It should be understood that the service life of a coating is related not only to its thickness but also to the material of the coating itself and its adhesion to the substrate. Most current coatings are chromium-aluminum coatings, which involve mixing chromium powder, aluminum powder, and some chloride powders, requiring complex pretreatment processes such as grinding, calcination, and cooling to obtain a co-diffusion agent, which is then coated onto the workpiece surface. Since the co-diffusion agent is composed entirely of powder, this method involves complex processing of the agent, and the coating has weak adhesion to the workpiece, making it prone to peeling. To address this, the chromium-nickel co-diffusion slurry of this embodiment includes both solid and liquid phase components to reduce the pretreatment process for the co-diffusion agent.

[0053] Specifically, the chromium-nickel co-diffusion slurry includes a solid phase component and a liquid phase component; the solid phase component includes chromium powder, nickel powder, alumina and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide and magnesium oxide.

[0054] In this embodiment, by mixing the liquid phase component with the solid phase component, the adhesion between the chromium-nickel co-diffusion slurry and the workpiece is improved, coating peeling is avoided, and there is no need for a complicated pretreatment process for the solid phase component, which simplifies the slurry preparation process.

[0055] In some alternative embodiments, the solid-liquid ratio (g:mL) of the solid phase component to the liquid phase component is 10:(1-5).

[0056] In some alternative embodiments, the liquid phase component comprises, by mass percentage: 10-30% Al(H2PO4)3; 15-25% water glass; 5-10% ammonium iodide; 10-40% chromium oxide; and 15-35% magnesium oxide.

[0057] In the liquid phase component, Al(H2PO4)3 and water glass act as binders, exhibiting high bonding strength with the metal substrate. A single coating process can achieve the required coating thickness. Secondly, during the drying process of the slurry, Al(H2PO4)3 and water glass can decompose directly without producing harmful gases, thus preventing the formation of bubbles within the coating and resulting in a dense, pore-free structure within the coating layer. Furthermore, the aforementioned binder components exhibit good high-temperature toughness and are not prone to cracking during the drying process.

[0058] Furthermore, in the liquid phase component, ammonium iodide acts as a penetration aid, which can form active transition halide gas, thereby accelerating the penetration of active chromium and nickel atoms into the matrix.

[0059] Furthermore, in the liquid phase component, magnesium oxide acts as a curing agent, causing the acidic phosphate ions in the binder to dehydrate and condense, effectively reducing the curing temperature of the slurry. Simultaneously, adding an appropriate amount of chromium oxide can slow down the curing reaction rate between magnesium oxide and the binder, preventing problems such as cracks on the cured coating surface and failure to form a film due to excessively rapid curing.

[0060] As an optional configuration, the content of Al(H2PO4)3 is preferably 10%, 15%, 20%, 25%, or 30%, the content of water glass is preferably 15%, 20%, or 25%, the content of ammonium iodide is preferably 5%, 7%, or 10%, the content of chromium oxide is preferably 10%, 15%, 20%, 28%, 35%, or 40%, and the content of magnesium oxide is preferably 15%, 25%, 30%, or 35%.

[0061] In some alternative embodiments, the solid phase component comprises, by mass percentage: 50-80% chromium powder; 1-10% nickel powder; 10-20% alumina; and 0-20% chromium oxide.

[0062] In the solid phase component, alumina and chromium oxide are used as fillers, which can effectively prevent the adhesion between chromium powder and nickel powder and between chromium powder, nickel powder and matrix during the slurry preparation process, resulting in uneven diffusion layer; secondly, adding a small amount of nickel can increase the diffusion rate and reduce the diffusion temperature, thereby reducing the adverse effects of heat treatment on the comprehensive mechanical properties of the matrix while achieving the required diffusion layer thickness.

[0063] It is worth noting that in this embodiment, chromium and nickel elements are diffused into the base metal, and the chromium and nickel diffused into the base metal can also form intermetallic compounds with the base metal. Compared with a single chromium diffusion coating, the chromium-nickel co-diffusion layer has superior wear resistance and corrosion resistance.

[0064] As an optional configuration, the preferred contents of chromium powder are 50%, 60%, 70%, and 80%, the preferred contents of nickel powder are 1%, 5%, and 10%, the preferred contents of alumina are 10%, 15%, and 20%, and the preferred contents of chromium oxide are 1%, 5%, 12%, 15%, and 20%.

[0065] In some alternative embodiments, chromium powder, nickel powder, alumina, and chromium oxide are ball-milled in a star-shaped ball mill jar to obtain a solid phase component. The ball milling speed is 350-400 r / min, and the milling time is 6-24 h. By ball-milling the mixed metal powders before mixing them with the liquid phase component, it is beneficial to achieve uniform mixing of the components.

[0066] Furthermore, the metal workpiece coated with chromium-nickel co-diffusion slurry undergoes drying, curing, and sintering treatment, including the following specific steps:

[0067] The metal workpiece coated with chromium-nickel co-diffusion slurry is pre-dried at a low temperature of 60-85℃ for 5-30 minutes, then dried at a low temperature of 100-160℃ for 30-60 minutes, and finally cured at a medium temperature of 250-300℃ for 20-60 minutes.

[0068] The dried and cured metal workpiece is sintered at 500-650℃ for 5-30 minutes.

[0069] In some alternative embodiments, the low-temperature pre-drying temperature is preferably 60°C, 70°C, or 80°C, and the time is preferably 5 min, 10 min, 15 min, 20 min, 25 min, or 30 min.

[0070] In some alternative embodiments, the low-temperature drying temperature is preferably 100°C, 120°C, 140°C, 150°C, or 160°C, and the time is preferably 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, or 60 min.

[0071] In other alternative embodiments, the medium-temperature curing temperature is preferably 250°C, 260°C, 270°C, 280°C, 290°C, or 300°C, and the time is preferably 20 min, 30 min, 40 min, 50 min, or 60 min.

[0072] In other alternative embodiments, the sintering temperature is preferably 500°C, 550°C, 600°C, or 650°C, and the sintering time is preferably 5 min, 10 min, 15 min, 20 min, 25 min, or 30 min.

[0073] In this embodiment, by adopting a segmented gradient curing process, the surface quality problems of the co-infiltrating slurry will not be caused by local stress during the curing process. At the same time, it is beneficial to increase the adhesion of the co-infiltrating slurry, improve the coating effect, shorten the curing time, and reduce energy consumption.

[0074] The chromium-nickel co-diffusion coating preparation method of this embodiment is simple, does not require vacuum conditions, has high production efficiency, and produces little pollution during the production process. The chromium-nickel co-diffusion coating formed based on the above components has good adhesion to the substrate, effectively preventing the coating from peeling off during use, thereby extending the coating life. Furthermore, this chromium-nickel co-diffusion coating has a wide range of applications and is highly practical. It is not only suitable for high-temperature alloys, but also for various carbon steels and other metal workpieces such as austenitic steels.

[0075] In another aspect of this disclosure, a chromium-nickel co-diffusion coating is provided, prepared according to the preparation method described above.

[0076] In this embodiment, the thickness of the chromium-nickel co-diffusion coating formed on various metal workpieces is 5-50 μm. The coating with this thickness has good adhesion to the surface of the metal workpiece and also has excellent resistance to high and low temperature corrosion and steam oxidation.

[0077] Another aspect of this disclosure proposes an application of a chromium-nickel co-diffusion coating, wherein the chromium-nickel co-diffusion coating described above is applied to the surface of metal workpieces made of carbon steel, austenitic steel and high-temperature alloys.

[0078] The preparation method of chromium-nickel co-diffusion coating will be further illustrated below with reference to several specific embodiments:

[0079] Example 1

[0080] This example uses a large boiler pipe made of carbon steel as the metal workpiece to be processed. The pipe has an outer diameter of 55mm, a wall thickness of 8mm, and a length of 4000mm. The surface treatment of this metal workpiece is chromium-nickel diffusion, which includes the following steps:

[0081] S1. Pipe surface cleaning:

[0082] Alcohol / acetone is used to clean the surface of the pipe workpiece to remove oil stains, dust, etc., while steel brushes are used to remove the surface oxide scale.

[0083] S2. Surface shot peening treatment:

[0084] The cleaned pipe workpiece was shot peened with a shot particle diameter of 0.3 mm, a shot peening pressure of 0.5 MPa, and a shot peening time of 10 min.

[0085] S3, Surface slurry coating

[0086] The chromium-nickel co-diffusion slurry should be applied in one go to a thickness of 0.5 mm using spraying (or brushing, etc.). Multiple layers of application are not permitted.

[0087] The preparation method of the chromium-nickel co-diffusion slurry is as follows: Based on the mass percentage of the solid phase components, weigh 70% chromium powder, 5% nickel powder, 15% alumina, and 10% chromium oxide, respectively. Ball mill the mixed metal powder at 350 r / min for 8 hours to obtain the final solid phase component. Based on the mass percentage of the liquid phase components, weigh 25% Al(H2PO4)3, 18% water glass, 7% ammonium iodide, 15% chromium oxide, and 35% magnesium oxide, and mix them to obtain the liquid phase component. Mix the solid and liquid phase components at a solid-liquid (g:ml) ratio of 10:2 to obtain the final metal powder coating raw material.

[0088] S4, Drying and Curing

[0089] A segmented gradient curing process is adopted, in which the metal pipe workpiece coated with chromium-nickel infiltration material is pre-dried at 75℃ for 5 minutes, then dried at 140℃ for 55 minutes, and finally cured at 250℃ for 30 minutes.

[0090] S5, Rapid Sintering

[0091] The metal pipe workpiece was subjected to rapid sintering diffusion chromium infiltration by rapid heating, followed by air cooling to room temperature; the heating rate was set to 1000℃ / min, the holding temperature was 500℃, and the holding time was 30min, resulting in a chromium-nickel co-infiltration coating on the metal pipe workpiece.

[0092] In Example 1, the oxidation resistance of the obtained chromium-nickel co-diffusion coating was tested, as follows: After cyclic oxidation at 500℃ for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-diffusion coating sample was 0.15 mg / mm². 2 The oxidation weight gain of the carbon steel matrix is ​​1.47 mg / mm². 2 The oxidation rate decreased by 89.8%.

[0093] In Example 1, the wear resistance of the obtained chromium-nickel co-diffusion coating was tested, as follows: Under test conditions of 10g load and 10s holding time, the microhardness of the prepared chromium-nickel co-diffusion coating was approximately 412 HV, while the microhardness of the carbon steel substrate was approximately 320 HV, representing an increase in hardness of about 1.3 times. Secondly, in Example 1, following the national standard GB / T 12444-2006 "Metallic Materials - Test Methods for Wear and Friction", the wear resistance of the carbon steel and the coating was tested. Under the same test conditions, the friction and wear amount of the coated sample decreased by approximately 21.7%, and the coefficient of friction decreased by approximately 6.8%.

[0094] Example 2

[0095] This example uses a large boiler pipe made of austenitic steel as the metal workpiece to be treated. The pipe has an outer diameter of 55mm, a wall thickness of 8mm, and a length of 4000mm. The surface treatment of this metal pipe workpiece is chromium-nickel diffusion, including the following steps:

[0096] S1. Pipe surface cleaning:

[0097] Alcohol / acetone is used to clean the surface of the pipe workpiece to remove oil stains, dust, etc., while steel brushes are used to remove the surface oxide scale.

[0098] S2. Surface shot peening treatment:

[0099] The cleaned pipe workpiece was shot peened with shot particles of 0.5 mm in diameter, shot peening pressure of 1.0 MPa, and shot peening time of 10 min.

[0100] S3, Surface slurry coating

[0101] The chromium-nickel co-diffusion slurry should be applied in one go to a thickness of 0.5 mm using spraying (or brushing, etc.). Multiple layers of application are not permitted.

[0102] The preparation method of the chromium-nickel co-diffusion slurry is as follows: Based on the mass percentage of the solid phase components, weigh 75% chromium powder, 3% nickel powder, 10% alumina, and 12% chromium oxide, respectively. Ball mill the mixed metal powder at 350 r / min for 10 h to obtain the final solid phase component. Based on the mass percentage of the liquid phase components, weigh 30% Al(H2PO4)3, 25% water glass, 10% ammonium iodide, 20% chromium oxide, and 15% magnesium oxide, and mix them to obtain the liquid phase component. Mix the solid and liquid phase components at a solid-liquid (g:ml) ratio of 10:3 to obtain the final metal powder coating raw material.

[0103] S4, Drying and Curing

[0104] A segmented gradient curing process is adopted, in which the metal pipe workpiece coated with chromium-nickel infiltration material is pre-dried at 85℃ for 5 minutes, then dried at 160℃ for 55 minutes, and finally cured at 300℃ for 30 minutes.

[0105] S5, Rapid Sintering

[0106] The metal pipe workpiece was subjected to rapid sintering diffusion chromium infiltration by rapid heating, followed by air cooling to room temperature; the heating rate was set to 1000℃ / min, the holding temperature was 550℃, and the holding time was 30min, resulting in a chromium-nickel co-infiltration coating on the metal pipe workpiece.

[0107] In Example 2, the oxidation resistance of the obtained chromium-nickel co-diffusion coating was tested, as follows: After cyclic oxidation at 650℃ for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-diffusion coating sample was 0.000078 mg / mm². 2 The oxidation weight gain of the stainless steel matrix is ​​0.0047 mg / mm². 2 The oxidation rate decreased by 98.3%.

[0108] In Example 2, the wear resistance of the obtained chromium-nickel co-diffusion coating was tested, as follows: Under test conditions of 10g load and 10s holding time, the microhardness of the prepared chromium-nickel co-diffusion coating was approximately 400 HV, while the microhardness of the austenitic steel substrate was approximately 190 HV, representing an increase in hardness of about 2.1 times. Furthermore, in Example 2, following the national standard GB / T 12444-2006 "Metallic Materials - Test Methods for Wear and Friction", the wear resistance of the austenitic steel and the coating was tested. Under the same test conditions, the friction and wear of the coated sample decreased by approximately 39%, and the coefficient of friction decreased by approximately 13%.

[0109] Example 3

[0110] This example uses a large boiler pipe made of high-temperature alloy as the metal workpiece to be processed. The pipe has an outer diameter of 55mm, a wall thickness of 8mm, and a length of 4000mm. The surface chromium-nickel diffusion treatment is performed on this metal pipe workpiece, including the following steps:

[0111] S1. Pipe surface cleaning:

[0112] Alcohol / acetone is used to clean the surface of the pipe workpiece to remove oil stains, dust, etc., while steel brushes are used to remove the surface oxide scale.

[0113] S2. Surface shot peening treatment:

[0114] The cleaned pipe workpiece was shot peened with shot peening particles of 0.5 mm in diameter, shot peening pressure of 1.5 MPa, and shot peening time of 15 min.

[0115] S3, Surface slurry coating

[0116] The chromium-nickel co-diffusion slurry should be applied in one go to a thickness of 1.0 mm using spraying (or brushing, etc.). Multiple layers of application are not allowed.

[0117] The preparation method of the chromium-nickel co-diffusion slurry is as follows: Based on the mass percentage of the solid phase components, weigh 60% chromium powder, 5% nickel powder, 20% alumina, and 15% chromium oxide, respectively. Ball mill the mixed metal powder at 350 r / min for 12 h to obtain the final solid phase component. Based on the mass percentage of the liquid phase components, weigh 25% Al(H2PO4)3, 20% water glass, 5% ammonium iodide, 35% chromium oxide, and 15% magnesium oxide, and mix them to obtain the liquid phase component. Mix the solid and liquid phase components at a solid-liquid (g:ml) ratio of 10:5 to obtain the final metal powder coating raw material.

[0118] S4, Drying and Curing

[0119] A segmented gradient curing process is adopted, in which the metal pipe workpiece coated with chromium-nickel infiltration material is pre-dried at 80℃ for 10 min, then dried at 150℃ for 30 min, and finally cured at 300℃ for 20 min.

[0120] S5, Rapid Sintering

[0121] The metal pipe workpiece was subjected to rapid sintering diffusion chromium infiltration by rapid heating, followed by air cooling to room temperature; the heating rate was set to 1000℃ / min, the holding temperature was 650℃, and the holding time was 20min, resulting in a chromium-nickel co-infiltration coating on the metal pipe workpiece.

[0122] In Example 3, the obtained chromium-nickel co-diffusion coating was subjected to an oxidation resistance test, as follows: After cyclic oxidation at 1000℃ for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-diffusion coating sample was 0.012 mg / mm². 2 The oxidation weight gain of the high-temperature alloy matrix is ​​0.108 mg / mm². 2 The oxidation rate decreased by 88.9%.

[0123] In Example 3, the wear resistance of the obtained chromium-nickel co-diffusion coating was tested, and the results are as follows: the microhardness of the prepared chromium-nickel co-diffusion coating is approximately 437 HV, while the microhardness of the high-temperature alloy substrate is approximately 300 HV, representing an increase in hardness of about 1.5 times. Furthermore, Example 3 also followed the national standard GB / T 12444-2006 "Metallic Materials - Test Methods for Wear" to test the wear resistance of the high-temperature alloy and the coating. Under the same test conditions, the frictional wear of the coated sample decreased by approximately 20.3%, and the coefficient of friction decreased by approximately 6.8%.

[0124] As shown in Figure 2, the thickness of the chromium-nickel co-diffusion coating obtained in Example 3 is about 31 μm, with an average chromium content of 35 wt.% and a nickel content of 6 wt.%. The co-diffusion coating has a uniform and dense structure, no obvious internal defects, and good metallurgical bonding with the substrate.

[0125] Example 4

[0126] This example uses a large boiler pipe made of high-temperature alloy as the metal workpiece to be processed. The pipe has an outer diameter of 55mm, a wall thickness of 8mm, and a length of 4000mm. The surface chromium-nickel diffusion treatment is performed on this metal pipe workpiece, including the following steps:

[0127] S1. Pipe surface cleaning:

[0128] Alcohol / acetone is used to clean the surface of the pipe workpiece to remove oil stains, dust, etc., while steel brushes are used to remove the surface oxide scale.

[0129] S2. Surface shot peening treatment:

[0130] The cleaned pipe workpiece was shot peened with a shot particle diameter of 0.1 mm, a shot peening pressure of 1.0 MPa, and a shot peening time of 20 min.

[0131] S3, Surface slurry coating

[0132] The chromium-nickel co-diffusion slurry should be applied in one go to a thickness of 0.8 mm using spraying (or brushing, etc.). Multiple layers of application are not allowed.

[0133] The preparation method of the chromium-nickel co-diffusion slurry is as follows: Based on the mass percentage of the solid phase components, weigh 70% chromium powder, 5% nickel powder, 10% alumina, and 15% chromium oxide, respectively. Ball mill the mixed metal powder at 400 r / min for 24 h to obtain the final solid phase component. Based on the mass percentage of the liquid phase components, weigh 20% Al(H2PO4)3, 15% water glass, 7% ammonium iodide, 28% chromium oxide, and 30% magnesium oxide, and mix them to obtain the liquid phase component. Mix the solid and liquid phase components at a solid-liquid (g:ml) ratio of 10:5 to obtain the final metal powder coating raw material.

[0134] S4, Drying and Curing

[0135] A segmented gradient curing process is adopted, in which the metal pipe workpiece coated with chromium-nickel infiltration material is pre-dried at 60℃ for 5 minutes, then dried at 100℃ for 55 minutes, and finally cured at 250℃ for 30 minutes.

[0136] S5, Rapid Sintering

[0137] The metal pipe workpiece was subjected to rapid sintering diffusion chromium infiltration by rapid heating, followed by air cooling to room temperature; the heating rate was set to 1000℃ / min, the holding temperature was 500℃, and the holding time was 30min, resulting in a chromium-nickel co-infiltration coating on the metal pipe workpiece.

[0138] In Example 4, the obtained chromium-nickel co-diffusion coating was subjected to an oxidation resistance test, as follows: After cyclic oxidation at 1000℃ for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-diffusion coating sample was 0.033 mg / mm². 2 The oxidation weight gain of the high-temperature alloy matrix is ​​0.108 mg / mm². 2 The oxidation rate decreased by 69.4%.

[0139] In Example 4, the wear resistance of the obtained chromium-nickel co-diffusion coating was tested, and the results are as follows: the microhardness of the prepared chromium-nickel co-diffusion coating is approximately 419.6 HV, while the microhardness of the high-temperature alloy substrate is approximately 300 HV, representing an increase in hardness of about 1.4 times. Secondly, in Example 4, following the national standard GB / T 12444-2006 "Metallic Materials - Test Methods for Wear", the wear resistance of the high-temperature alloy and the coating was tested. Under the same test conditions, the frictional wear of the coated sample decreased by approximately 18.3%, and the coefficient of friction decreased by approximately 6.2%.

[0140] This disclosure presents a chromium-nickel co-diffusion coating, its preparation method, and its application, which have the following advantages compared to the prior art:

[0141] First, the chromium-nickel high-temperature corrosion-resistant coating and its preparation method disclosed herein do not require vacuum conditions, the preparation process is simple, and the chromium-nickel co-diffusion coating has high preparation efficiency, low pollution, adjustable thickness, and good wear resistance, especially with excellent resistance to high and low temperature corrosion and steam oxidation.

[0142] Second, this disclosure mixes solid and liquid components to form a chromium-nickel co-diffusion slurry, which is easy to coat the surface of metal workpieces and has a strong bonding force with the workpiece surface.

[0143] Third, the metal powder raw materials described in this disclosure are suitable for various metal workpieces that require surface strengthening, including carbon steel, austenitic stainless steel and high-temperature alloys, and have a wide range of applications and are extremely practical.

[0144] Fourth, this disclosure further enhances the surface coating strength and corrosion resistance by subjecting the workpiece to shot peening before co-infiltration coating, thereby increasing the specific surface area of ​​the metal workpiece, improving the penetration of metal elements and the adhesion of the coating.

[0145] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method of producing a chromizing coating, characterized by, The preparation method comprises: carrying out surface pretreatment on the metal workpiece; carrying out shot blasting treatment on the pretreated metal workpiece; coating a chromium-nickel co-permeation material slurry on the surface of the shot-blasted metal workpiece once, and carrying out drying and solidification treatment and sintering treatment, so that a chromium-nickel co-permeation coating layer is obtained on the surface of the metal workpiece; wherein the chromium-nickel co-permeation material slurry comprises solid-phase components and liquid-phase components; the solid-phase components comprise chromium powder, nickel powder, aluminum oxide and chromium oxide, and the liquid-phase components comprise Al(H2PO4)3, water glass, ammonium iodide, chromium oxide and magnesium oxide.

2. The production method according to claim 1, characterized by, The solid-liquid ratio of the solid-phase components to the liquid-phase components is 10:(1-5).

3. The preparation method according to claim 1, characterized in that, According to the mass percentage, the solid-phase components comprise: 50-80% of chromium powder; 1-10% of nickel powder; 10-20% of aluminum oxide; 0-20% of chromium oxide; the sum of the mass percentages of the above solid-phase components is 100%.

4. The production method according to claim 3, characterized by, The chromium powder, the nickel powder, the aluminum oxide and the chromium oxide are ball milled for 6-24 h under the condition that the rotating speed is 350-400 r / min, so that the solid-phase components are obtained.

5. The preparation method according to claim 1, characterized in that, According to the mass percentage, the liquid-phase components comprise: 10-30% of Al(H2PO4)3; 15-25% of water glass; 5-10% of ammonium iodide; 10-40% of chromium oxide; 15-35% of magnesium oxide; the sum of the mass percentages of the above liquid-phase components is 100%.

6. The production method according to any one of claims 1 to 5, characterized by, The coating thickness of the chromium-nickel co-permeation material slurry coated on the surface of the metal workpiece is 0.1-1.0 mm.

7. The production method according to any one of claims 1 to 5, characterized by, In the shot blasting treatment, the diameter of the shot blasting particles is 0.1-1.0 mm, the shot blasting pressure is 0.5-2.0 MPa, and the shot blasting time is 10-30 min.

8. The production method according to any one of claims 1 to 5, characterized by, The drying and solidification treatment and the sintering treatment of the metal workpiece coated with the chromium-nickel co-permeation material slurry comprise: pre-drying the metal workpiece coated with the chromium-nickel co-permeation material slurry at 60-85 ℃ for 5-30 min, then drying at 100-160 ℃ for 30-60 min, and finally solidifying at 250-300 ℃ for 20-60 min; sintering the dried and solidified metal workpiece at 500-650 ℃ for 5-30 min.

9. A chromizing coating characterized by, The chromium-nickel co-permeation coating layer is prepared by the preparation method in any one of claims 1 to 8.

10. Use of a chromising coating, characterized in that The chromium-nickel co-permeation coating layer in claim 9 is applied on the surface of a carbon steel, an austenitic steel or a high-temperature alloy metal workpiece.

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