Chromium-nickel co-penetration coating and its preparation method and application

Abstract

The present disclosure provides a chromium-nickel co-penetration coating and its preparation method and application. The preparation method includes: performing surface pretreatment on a metal workpiece; performing shot peening on the pretreated metal workpiece; applying a chromium-nickel co-penetration slurry once on the surface of the shot peened metal workpiece, drying, solidifying, and sintering to obtain a chromium-nickel co-penetration coating on the surface of the metal workpiece; the chromium-nickel co-penetration slurry includes a solid phase component and a liquid phase component; the solid phase component includes chromium powder, nickel powder, aluminum oxide, and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide, and magnesium oxide. The coating is suitable for various metal workpieces whose surfaces need to be strengthened, including carbon steel, austenitic stainless steel, and high-temperature alloys. It has a wide range of applications and is highly practical. The coating has strong adhesion and can improve the metal workpiece's resistance to high and low temperature corrosion and steam oxidation.

Description

Technical Field

[0001] The present disclosure belongs to the technical field of material surface coatings, and particularly relates to a chromium-nickel co-penetration coating and a preparation method and application thereof. Background Art

[0002] The most common corrosion protection method for metal workpieces is to coat the metal surface with a metal, non-metallic, or metal-non-metallic composite film through physical, chemical, or electrochemical metal surface treatment processes as a protective layer to prevent or slow chemical reactions between the metal and the medium it contacts. Related metal surface treatment technologies include thermal spraying, electroplating, thermal diffusion, surface phosphating, and metal or non-metallic coatings. By applying a coating to the workpiece surface, the composition, organization, and structure of the material surface are altered, improving surface properties, enhancing the workpiece's corrosion and wear resistance, and extending the workpiece's service life.

[0003] Thermal diffusion technology involves the use of heat diffusion to infiltrate the desired metal or non-metallic element into the surface of a metal workpiece, thereby forming a surface alloy layer. Co-diffusion is the most widely used thermal diffusion process, incorporating multiple elements into the workpiece surface simultaneously through a single heating diffusion process. Co-diffusion combines the advantages of various single-diffusion methods, while offsetting their shortcomings through the coordination of elements, resulting in better overall performance on the workpiece surface.

[0004] At present, there are co-penetration based on metal elements, co-penetration based on non-metallic elements, and co-penetration based on rare earth elements. For example, aluminum-chromium co-penetration is performed on the surface of high-temperature alloy workpieces to form an element coating of a dense oxide film. The stable physical and chemical properties of its oxide under high temperature conditions are used to improve the service life of the workpiece. However, most of the current co-penetration of metal workpieces adopts a solid method, which requires a combination of multiple metal elements and components such as catalysts. The co-penetration time is long and the experimental requirements are high. In addition, the formed coating has poor adhesion and small thickness. Multiple coatings are required to achieve the required thickness, and the scope of application is narrow. Especially for metal workpieces such as high-carbon steel and high-alloy steel, in the process of element diffusion, due to the different diffusion rates of Cr or Al and Fe, there is a Kirkendall effect of atomic diffusion. The diffusion of Cr or Al is accompanied by the appearance of voids, resulting in a large number of pores in the coating, the coating is not dense, the brittleness increases, and it may even cause the coating to fall off, seriously affecting the performance. Secondly, there is also a gas method, which uses alumina, chromium powder, aluminum powder and ammonium chloride to form an aluminum-chromium co-penetration agent, and the chromium-aluminum co-penetration agent and parts are placed in a crucible, and heated under an argon atmosphere to obtain parts containing an aluminum-chromium coating. This method needs to be carried out in a vacuum environment and the preparation process needs to be strictly controlled. In addition, there is also a neutral salt bath chromium-aluminum co-penetration method, which uses sodium chloride, barium chloride, sodium fluoride, aluminum powder, and chromium powder to form a co-penetration agent. The co-penetration agent is placed in a crucible, and the crucible containing the salt bath chromium-aluminum co-penetration agent is placed in a resistance furnace for heating. The sample is then placed in a prepared chromium-aluminum co-penetration salt bath so that the main working surface of the sample is kept as perpendicular to the flow direction of the salt bath as possible. After keeping warm for 4 hours, it is taken out and oil quenched, that is, a chromium-aluminum co-penetration layer is obtained on the surface of the nickel-based high-temperature alloy. This method has a long holding time and has high requirements on the placement of the sample. The thickness of the coating formed is relatively thin, only about 20μm, and the corrosion and wear resistance is poor. Summary of the Invention

[0005] The present disclosure aims to solve at least one of the technical problems existing in the prior art and provide a chromium-nickel co-penetration coating and a preparation method and application thereof.

[0006] In one aspect of the present disclosure, a method for preparing a chromium-nickel co-penetration coating is provided.

[0007] The preparation method comprises:

[0008] Surface pretreatment of metal workpieces;

[0009] Shot peening is performed on the pretreated metal workpiece;

[0010] The chromium-nickel co-penetration slurry is applied once on the surface of the metal workpiece after shot blasting, and then dried, solidified and sintered to obtain a chromium-nickel co-penetration coating on the surface of the metal workpiece; wherein,

[0011] 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, aluminum oxide and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide and magnesium oxide.

[0012] Optionally, the solid-liquid ratio of the solid phase component to the liquid phase component is 10:(1-5).

[0013] Optionally, the solid phase components include, by mass percentage:

[0014] 50-80% chromium powder;

[0015] 1-10% nickel powder;

[0016] 10-20% alumina;

[0017] 0-20% chromium oxide;

[0018] The sum of the mass percentages of the above solid phase components is 100%.

[0019] Optionally, the chromium powder, nickel powder, aluminum oxide and chromium oxide are ball-milled at a rotation speed of 350 to 400 r / min for 6 to 24 hours to obtain a solid phase component.

[0020] Optionally, the liquid phase components include, by mass percentage:

[0021] 10-30% Al(H2PO4)3;

[0022] 15-25% water glass;

[0023] 5-10% ammonium iodide;

[0024] 10-40% chromium oxide;

[0025] 15-35% magnesium oxide;

[0026] The sum of the mass percentages of the above liquid phase components is 100%.

[0027] Optionally, the coating thickness of the chromium-nickel co-diffusion slurry coated on the surface of the metal workpiece is 0.1 to 1.0 mm.

[0028] Optionally, in the shot peening treatment, the shot peening particle diameter is 0.1 to 1.0 mm, the shot peening pressure is 0.5 to 2.0 MPa, and the shot peening time is 10 to 30 minutes.

[0029] Optionally, the metal workpiece coated with the chromium-nickel co-diffusion slurry is subjected to drying, solidification, and sintering treatment, including:

[0030] The metal workpiece coated with the chromium-nickel co-diffusion slurry is pre-dried at 60-85°C for 5-30 minutes, then dried at 100-160°C for 30-60 minutes, and finally cured at a medium temperature of 250-300°C for 20-60 minutes;

[0031] The dried and solidified metal workpiece is sintered at 500-650°C for 5-30 minutes.

[0032] In another aspect of the present disclosure, a chromium-nickel co-penetration coating is provided, which is prepared according to the preparation method described above.

[0033] Another aspect of the present disclosure provides an application of a chromium-nickel co-penetration coating, wherein the chromium-nickel co-penetration coating described above is applied to the surface of a metal workpiece made of carbon steel, austenitic steel, and a high-temperature alloy.

[0034] The present disclosure provides a chromium-nickel co-penetration coating and its preparation method and application. The preparation method includes: performing surface pretreatment on a metal workpiece; performing shot peening on the pretreated metal workpiece; applying a chromium-nickel co-penetration slurry once on the surface of the shot peened metal workpiece, drying, solidifying, and sintering to obtain a chromium-nickel co-penetration coating on the surface of the metal workpiece; the chromium-nickel co-penetration slurry includes a solid phase component and a liquid phase component; the solid phase component includes chromium powder, nickel powder, aluminum oxide, and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide, and magnesium oxide. The coating is suitable for various metal workpieces whose surfaces need to be strengthened, including carbon steel, austenitic stainless steel, and high-temperature alloys. It has a wide range of applications and is highly practical. The coating has strong adhesion and can further improve the metal workpiece's resistance to high and low temperature corrosion and steam oxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flowchart of a method for preparing a chromium-nickel co-penetration coating according to an embodiment of the present disclosure;

[0036] Figure 2 This is an electron microscope image of the chromium-nickel co-penetration coating prepared in Example 3 of the present disclosure. DETAILED DESCRIPTION

[0037] To help those skilled in the art better understand the technical solutions of the present disclosure, the present disclosure is further described below in conjunction with the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a portion of the embodiments of the present disclosure, not all of them. Based on the described embodiments of the present disclosure, all other embodiments obtained by those of ordinary skill in the art without the need for creative work are within the scope of protection of the present disclosure.

[0038] like Figure 1As shown, one aspect of the present disclosure provides a method S100 for preparing a chromium-nickel co-penetration coating, which specifically includes the following steps S110 to S130:

[0039] S110. Perform surface pretreatment on the metal workpiece.

[0040] Specifically, organic reagents such as alcohol or acetone are used to clean oil stains and dust on the surface of the metal workpiece. At the same time, the oxide scale on the surface of the metal workpiece can be removed by using a steel brush, sandpaper or polishing.

[0041] It should be noted that the present embodiment does not impose any specific restrictions on the material or type of the metal workpiece. For example, the workpiece may be a high-temperature alloy metal workpiece, various types of carbon steel metal workpieces, or austenitic steel metal workpieces. Of course, such metal workpieces may also include pipelines, turbine blades in the aviation field, or other types of workpieces.

[0042] S120, performing shot peening on the pretreated metal workpiece.

[0043] Specifically, during the shot peening process, shot peening particles are sprayed onto the surface of the metal workpiece at high speed, causing its surface to undergo plastic deformation to form a strengthening layer of a certain thickness. The shot peening particles have a diameter of 0.1 to 1.0 mm, the shot peening pressure is 0.5 to 2.0 MPa, and the shot peening time is 10 to 30 minutes.

[0044] In this embodiment, by activating the surface of the metal workpiece, the physical properties and bonding strength of the metal workpiece such as adhesion, roughness and specific surface area are improved, which is beneficial to increase the adhesion of the subsequent penetration coating, further improve the penetration effect of the subsequent co-penetration coating, and make the coating thickness thicker.

[0045] S130, applying the chromium-nickel co-penetration slurry once on the surface of the metal workpiece after the shot blasting treatment, and performing drying, curing and sintering treatment to obtain a chromium-nickel co-penetration coating on the surface of the metal workpiece.

[0046] It should be noted that this embodiment does not specifically limit the method of coating the chromium-nickel co-diffusion slurry on the surface of the metal workpiece. For example, the chromium-nickel co-diffusion slurry can be coated on the surface of the metal workpiece by spraying or brushing.

[0047] It should be further noted that the chromium-aluminum co-diffusion coating currently prepared is relatively thin, requiring multiple coats to increase the coating thickness and resulting in poor stability. However, this embodiment eliminates the need for multiple coats and can achieve the desired thickness with a single coat. Furthermore, the coating thickness can be adjusted based on actual needs.

[0048] Specifically, in this embodiment, the chrome-nickel slurry is applied to an appropriate thickness in a single application, eliminating the need for multiple layered applications. The chrome-nickel slurry is applied to a thickness of 0.1 to 1.0 mm. In other words, this embodiment applies the chrome-nickel slurry to the surface of the metal workpiece in a single application, forming a chrome-nickel coating layer. The chrome-nickel coating layer has a thickness of 0.1 to 1.0 mm. Within this thickness range, the metal workpiece's applicability is ensured while also improving its high-temperature corrosion resistance.

[0049] In some preferred embodiments, the slurry coating thickness of the chromium-nickel co-penetration 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.

[0050] It should be understood that the service life of the coating is not only related to the thickness of the coating, but also has a certain correlation with the material of the coating itself and its bonding with the substrate. Most of the current coatings are chromium-aluminum coatings, which mix chromium powder, aluminum powder and some chloride powders together. They need to go through a complex pretreatment process such as grinding, calcining, and cooling to obtain a co-penetrating agent, which is then applied to the surface of the workpiece. Since the co-penetrating agent is composed of powder, this method has a complicated processing process for the co-penetrating agent, and the bonding force between the coating and the workpiece is weak, and the coating is easy to fall off. In response to this, the chromium-nickel co-penetrating slurry of this embodiment includes not only a solid phase component but also a liquid phase component to reduce the pretreatment process of the co-penetrating agent.

[0051] 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, aluminum oxide and chromium oxide, and the liquid phase component includes Al(H2PO4)3, water glass, ammonium iodide, chromium oxide and magnesium oxide.

[0052] 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, the coating is prevented from falling off, and there is no need to perform a complicated pretreatment process on the solid phase component, thereby simplifying the slurry preparation process.

[0053] In other preferred embodiments, the solid-liquid ratio (g:mL) of the solid phase component to the liquid phase component is 10:(1-5).

[0054] In other preferred embodiments, the liquid phase components include, 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.

[0055] Among them, in the liquid phase components, Al(H2PO4)3 and water glass serve as binders, and have high bonding strength with the metal substrate, and the coating thickness required for preparing the coating can be achieved in one coating treatment; secondly, in the process of drying the slurry, Al(H2PO4)3 and water glass can be directly decomposed without producing harmful gases, which can avoid the formation of bubbles inside the coating, thereby making the structure inside the coating layer dense and free of pores; and the above-mentioned binder components have good high-temperature toughness and are not easy to crack during the drying process.

[0056] Furthermore, in the liquid phase component, ammonium iodide acts as a penetration aid, which can form active transition halide gas and accelerate the penetration speed of active chromium atoms and nickel atoms into the matrix.

[0057] Furthermore, in the liquid phase, magnesium oxide acts as a curing agent, dehydrating and condensing the acid phosphate in the binder, effectively lowering the slurry's curing and film-forming temperature. Simultaneously, adding an appropriate amount of chromium oxide can slow the curing reaction 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 fast curing.

[0058] As a further preferred embodiment, the content of Al(H2PO4)3 is preferably 10%, 15%, 20%, 25%, 30%, the content of water glass is preferably 15%, 20%, 25%, the content of ammonium iodide is preferably 5%, 7%, 10%, the content of chromium oxide is preferably 10%, 15%, 20%, 28%, 35%, 40%, and the content of magnesium oxide is preferably 15%, 25%, 30%, 35%.

[0059] In other preferred embodiments, the solid phase components include, by mass percentage: 50-80% chromium powder; 1-10% nickel powder; 10-20% aluminum oxide; and 0-20% chromium oxide.

[0060] Among them, in the solid phase components, aluminum oxide 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 the substrate during the slurry preparation process, resulting in uneven diffusion layer; secondly, adding a small amount of nickel can increase the chromization speed and reduce the chromization temperature, thereby reducing the adverse effects of heat treatment on the comprehensive mechanical properties of the substrate while achieving the required diffusion layer thickness.

[0061] It is worth noting that the chromium and nickel elements in this embodiment are respectively infiltrated into the base metal, and the chromium and nickel infiltrated into the base can also form intermetallic compounds with the base. Compared with a single chromium-infiltrated coating, the chromium-nickel co-infiltrated layer has better wear resistance and corrosion resistance.

[0062] As a further preferred embodiment, the content of chromium powder is preferably 50%, 60%, 70%, 80%, the content of nickel powder is preferably 1%, 5%, 10%, the content of aluminum oxide is preferably 10%, 15%, 20%, and the content of chromium oxide is preferably 1%, 5%, 12%, 15%, 20%.

[0063] In other preferred embodiments, chromium powder, nickel powder, aluminum oxide, and chromium oxide are ball-milled in a planetary ball mill to obtain a solid phase component. The ball milling speed is 350-400 rpm and the milling time is 6-24 hours. Ball-milling the mixed metal powders before mixing with the liquid phase component facilitates uniform mixing of the components.

[0064] Furthermore, the metal workpiece coated with the chromium-nickel co-diffusion slurry is dried, solidified, and sintered, including the following specific steps:

[0065] The metal workpiece coated with the chromium-nickel co-diffusion slurry is pre-dried at a low temperature of 60-85°C for 5-30 minutes, then dried at a low temperature of 100-160°C for 30-60 minutes, and finally cured at a medium temperature of 250-300°C for 20-60 minutes;

[0066] The dried and solidified metal workpiece is sintered at 500-650°C for 5-30 minutes.

[0067] In some preferred 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.

[0068] In other preferred embodiments, the temperature of low-temperature drying is preferably 100°C, 120°C, 140°C, 150°C, 160°C, and the time is preferably 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min.

[0069] In other preferred embodiments, the medium-temperature curing temperature is preferably 250°C, 260°C, 270°C, 280°C, 290°C, 300°C, and the curing time is preferably 20 min, 30 min, 40 min, 50 min, 60 min.

[0070] In other preferred 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.

[0071] In this embodiment, by adopting a segmented gradient curing process, it is ensured that the co-infiltration slurry will not have surface quality problems due to local stress during the curing process. At the same time, it is beneficial to increase the adhesion of the co-infiltration slurry, improve the coating effect, shorten the curing time, and reduce energy consumption.

[0072] The preparation method of the chromium-nickel co-penetration coating of this embodiment is simple, does not need to be carried out under vacuum conditions, has high production efficiency, and has little pollution during the production process. The chromium-nickel co-penetration coating formed based on the above components has good bonding with the substrate, effectively preventing the coating from falling off during use, thereby achieving the purpose of extending the life of the coating. In addition, the chromium-nickel co-penetration coating has a wide range of applications and strong practicality. It is not only suitable for high-temperature alloys, but also can be applied to various types of carbon steels and other metal workpieces such as austenitic steel.

[0073] In another aspect of the present disclosure, a chromium-nickel co-penetration coating is provided, which is prepared according to the preparation method described above.

[0074] In this embodiment, the chromium-nickel co-diffusion coating formed on various metal workpieces has a thickness of 5-50 μm. The coating corresponding to 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.

[0075] Another aspect of the present disclosure provides an application of a chromium-nickel co-penetration coating, wherein the chromium-nickel co-penetration coating described above is applied to the surface of a metal workpiece made of carbon steel, austenitic steel, and a high-temperature alloy.

[0076] The preparation method of the chromium-nickel co-penetration coating will be further described below with reference to several specific examples:

[0077] Example 1

[0078] This example uses a large carbon steel boiler pipe as the metal workpiece to be treated. The pipe specifications are all 55mm in outer diameter, 8mm in wall thickness, and 4000mm in length. The surface chromium-nickel treatment is performed on the metal workpiece, including the following steps:

[0079] S1. Pipeline surface cleaning:

[0080] Use alcohol / acetone to clean the surface oil stains, dust, etc. of the pipeline workpiece, and use a steel brush to remove the surface oxide scale.

[0081] S2. Surface shot peening treatment:

[0082] The cleaned pipe workpiece is shot peened with a shot peening particle diameter of 0.3 mm, a shot peening pressure of 0.5 MPa, and a shot peening time of 10 min.

[0083] S3. Surface slurry coating

[0084] Use spraying (or brushing or other methods) to apply the chromium-nickel co-diffusion slurry to a thickness of 0.5mm at one time, and do not apply it in layers multiple times.

[0085] The preparation method of the chromium-nickel co-diffusion slurry is as follows: according to the mass percentage of the solid phase components, 70% chromium powder, 5% nickel powder, 15% aluminum oxide and 10% chromium oxide are weighed respectively, and the mixed metal powder is ball-milled at a ball milling speed of 350r / min and a ball milling time of 8h to obtain the final solid phase component. According to the mass percentage of the liquid phase component, 25% Al(H2PO4)3, 18% water glass, 7% ammonium iodide, 15% chromium oxide and 35% magnesium oxide are measured and mixed to obtain the liquid phase component. The solid phase component and the liquid phase component are mixed at a solid-liquid (g:ml) ratio of 10:2 to obtain the final metal powder coating raw material.

[0086] S4, drying and curing

[0087] Using a segmented gradient curing process, the metal pipe workpiece coated with chromium-nickel material was pre-dried at 75°C for 5 minutes, then dried at 140°C for 55 minutes, and finally cured at a medium temperature of 250°C for 30 minutes.

[0088] S5, rapid sintering

[0089] The metal pipe workpiece is rapidly sintered and diffused chromized by a rapid heating method, and then air-cooled to room temperature; the heating rate is set to 1000℃ / min, the holding temperature is 500℃, and the holding time is 30min, to obtain a chromium-nickel co-diffusion coating coated on the metal pipe workpiece.

[0090] In Example 1, the obtained chromium-nickel co-penetration coating was subjected to an oxidation resistance test, specifically as follows: after cyclic oxidation at 500°C for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-penetration coating sample was 0.15 mg / mm 2 The oxidation weight gain of carbon steel matrix is ​​1.47mg / mm 2 , the oxidation rate decreased by 89.8%.

[0091] In Example 1, the resulting chromium-nickel co-infiltration coating was subjected to wear resistance testing. Specifically, under the test conditions of a 10g load and a 10s dwell time, the microhardness of the prepared chromium-nickel co-infiltration coating was approximately 412 HV, while the microhardness of the carbon steel substrate was approximately 320 HV, representing an increase in hardness by approximately 1.3 times. Furthermore, in accordance with the national standard GB / T 12444-2006, "Metallic Materials, Test Methods for Wear," the wear resistance of the carbon steel and the coating was tested. Under the same test conditions, the friction wear of the coated sample was reduced by approximately 21.7%, and the friction coefficient was reduced by approximately 6.8%.

[0092] Example 2

[0093] This example uses a large boiler pipe made of austenitic steel as the metal workpiece to be treated. The pipe specifications are all 55mm in outer diameter, 8mm in wall thickness, and 4000mm in length. Surface chromium-nickel treatment is performed on the metal pipe workpiece, including the following steps:

[0094] S1. Pipeline surface cleaning:

[0095] Use alcohol / acetone to clean the surface oil stains, dust, etc. of the pipeline workpiece, and use a steel brush to remove the surface oxide scale.

[0096] S2. Surface shot peening treatment:

[0097] The cleaned pipe workpiece is shot peened with a shot peening particle diameter of 0.5 mm, a shot peening pressure of 1.0 MPa, and a shot peening time of 10 min.

[0098] S3. Surface slurry coating

[0099] Use spraying (or brushing or other methods) to apply the chromium-nickel co-diffusion slurry to a thickness of 0.5mm at one time, and do not apply it in layers multiple times.

[0100] The preparation method of the chromium-nickel co-diffusion slurry is as follows: according to the mass percentage of the solid phase components, 75% of chromium powder, 3% of nickel powder, 10% of aluminum oxide and 12% of chromium oxide are weighed respectively, and the mixed metal powder is ball-milled at a ball milling speed of 350r / min and a ball milling time of 10h to obtain the final solid phase component. According to the mass percentage of the liquid phase component, 30% of Al(H2PO4)3, 25% of water glass, 10% of ammonium iodide, 20% of chromium oxide and 15% of magnesium oxide are measured and mixed to obtain the liquid phase component. The solid phase component and the liquid phase component are mixed at a solid-liquid (g:ml) ratio of 10:3 to obtain the final metal powder coating raw material.

[0101] S4, drying and curing

[0102] Using a segmented gradient curing process, the metal pipe workpiece coated with chromium-nickel material was pre-dried at 85°C for 5 minutes, then dried at 160°C for 55 minutes, and finally cured at 300°C for 30 minutes.

[0103] S5, rapid sintering

[0104] The metal pipe workpiece is rapidly sintered and diffused chromized by a rapid heating method, and then air-cooled to room temperature; the heating rate is set to 1000℃ / min, the holding temperature is 550℃, and the holding time is 30min, to obtain a chromium-nickel co-diffusion coating coated on the metal pipe workpiece.

[0105] In Example 2, the obtained chromium-nickel co-penetration coating was subjected to an oxidation resistance test, as follows: After cyclic oxidation at 650°C for 100 hours, the oxidation weight gain of the prepared chromium-nickel co-penetration coating sample was 0.000078 mg / mm 2 The oxidation weight gain of the stainless steel substrate is 0.0047 mg / mm 2 , the oxidation rate decreased by 98.3%.

[0106] In Example 2, the resulting chromium-nickel co-infiltrated coating was subjected to wear resistance testing. Specifically, under the test conditions of a 10g load and a 10s dwell time, the microhardness of the prepared chromium-nickel co-infiltrated coating was approximately 400 HV, while the microhardness of the austenitic steel substrate was approximately 190 HV, representing a hardness increase of approximately 2.1 times. Furthermore, in accordance with the national standard GB / T 12444-2006, "Metallic Materials, Test Methods for Wear," this Example 2 tested the wear resistance of the austenitic steel and the coating. Under the same test conditions, the friction wear of the coated sample was reduced by approximately 39%, and the friction coefficient was reduced by approximately 13%.

[0107] Example 3

[0108] This example uses a large boiler pipe made of high-temperature alloy as the metal workpiece to be treated. The pipe specifications are all 55mm in outer diameter, 8mm in wall thickness, and 4000mm in length. Surface chromium-nickel treatment is performed on the metal pipe workpiece, including the following steps:

[0109] S1. Pipeline surface cleaning:

[0110] Use alcohol / acetone to clean the surface oil stains, dust, etc. of the pipeline workpiece, and use a steel brush to remove the surface oxide scale.

[0111] S2. Surface shot peening treatment:

[0112] The cleaned pipe workpiece is shot peened with a shot peening particle diameter of 0.5 mm, a shot peening pressure of 1.5 MPa, and a shot peening time of 15 min.

[0113] S3. Surface slurry coating

[0114] Use spraying (or brushing or other methods) to apply the chromium-nickel co-diffusion slurry to a thickness of 1.0 mm at one time, and do not apply it in layers multiple times.

[0115] The preparation method of the chromium-nickel co-diffusion slurry is as follows: according to the mass percentage of the solid phase components, 60% chromium powder, 5% nickel powder, 20% aluminum oxide and 15% chromium oxide are weighed respectively, and the mixed metal powder is ball-milled at a ball milling speed of 350r / min and a ball milling time of 12h to obtain the final solid phase component. According to the mass percentage of the liquid phase component, 25% Al(H2PO4)3, 20% water glass, 5% ammonium iodide, 35% chromium oxide and 15% magnesium oxide are measured and mixed to obtain the liquid phase component. The solid phase component and the liquid phase component are mixed at a solid-liquid (g:ml) ratio of 10:5 to obtain the final metal powder coating raw material.

[0116] S4, drying and curing

[0117] Using a segmented gradient curing process, the metal pipe workpiece coated with chromium-nickel material was pre-dried at 80°C for 10 minutes, then dried at 150°C for 30 minutes, and finally cured at 300°C for 20 minutes.

[0118] S5, rapid sintering

[0119] The metal pipe workpiece is rapidly sintered and diffused chromized by a rapid heating method, and then air-cooled to room temperature; the heating rate is set to 1000℃ / min, the holding temperature is 650℃, and the holding time is 20min, to obtain a chromium-nickel co-diffusion coating on the metal pipe workpiece.

[0120] In Example 3, the obtained chromium-nickel co-penetration coating was subjected to an oxidation resistance test, as follows: After cyclic oxidation at 1000°C for 100h, the oxidation weight gain of the prepared chromium-nickel co-penetration coating sample was 0.012mg / mm 2 The oxidation weight gain of the high-temperature alloy matrix is ​​0.108 mg / mm 2 , the oxidation rate decreased by 88.9%.

[0121] In Example 3, the resulting chromium-nickel co-infiltrated coating was subjected to wear resistance testing. Specifically, the microhardness of the prepared chromium-nickel co-infiltrated coating was approximately 437 HV, while the microhardness of the high-temperature alloy substrate was approximately 300 HV, representing a hardness increase of approximately 1.5 times. Furthermore, in accordance with the national standard GB / T 12444-2006, "Metallic Materials, Test Methods for Wear," the wear resistance of the high-temperature alloy and coating was tested. Under the same test conditions, the friction wear of the coated sample was reduced by approximately 20.3%, and the friction coefficient was reduced by approximately 6.8%.

[0122] like Figure 2As shown, the thickness of the chromium-nickel co-penetration coating obtained in Example 3 is about 31 μm, and the average chromium content and nickel content are 35 wt.% and 6 wt.%, respectively. The co-penetration coating has a uniform and dense structure, no obvious defects inside, and good metallurgical bonding with the substrate.

[0123] Example 4

[0124] This example uses a large boiler pipe made of high-temperature alloy as the metal workpiece to be treated. The pipe specifications are all 55mm in outer diameter, 8mm in wall thickness, and 4000mm in length. Surface chromium-nickel treatment is performed on the metal pipe workpiece, including the following steps:

[0125] S1. Pipeline surface cleaning:

[0126] Use alcohol / acetone to clean the surface oil stains, dust, etc. of the pipeline workpiece, and use a steel brush to remove the surface oxide scale.

[0127] S2. Surface shot peening treatment:

[0128] The cleaned pipe workpiece is shot peened with a shot peening particle diameter of 0.1 mm, a shot peening pressure of 1.0 MPa, and a shot peening time of 20 min.

[0129] S3. Surface slurry coating

[0130] Use spraying (or brushing or other methods) to apply the chromium-nickel co-diffusion slurry to a thickness of 0.8 mm at one time, and do not apply it in layers multiple times.

[0131] The preparation method of the chromium-nickel co-diffusion slurry is as follows: according to the mass percentage of the solid phase components, 70% chromium powder, 5% nickel powder, 10% aluminum oxide and 15% chromium oxide are weighed respectively, and the mixed metal powder is ball-milled at a ball milling speed of 400r / min for 24 hours to obtain the final solid phase component. According to the mass percentage of the liquid phase component, 20% Al(H2PO4)3, 15% water glass, 7% ammonium iodide, 28% chromium oxide and 30% magnesium oxide are measured and mixed to obtain the liquid phase component. The solid phase component and the liquid phase component are mixed at a solid-liquid (g:ml) ratio of 10:5 to obtain the final metal powder coating raw material.

[0132] S4, drying and curing

[0133] Using a segmented gradient curing process, the metal pipe workpiece coated with chromium-nickel material was pre-dried at 60°C for 5 minutes, then dried at 100°C for 55 minutes, and finally cured at 250°C for 30 minutes.

[0134] S5, rapid sintering

[0135] The metal pipe workpiece is rapidly sintered and diffused chromized by a rapid heating method, and then air-cooled to room temperature; the heating rate is set to 1000℃ / min, the holding temperature is 500℃, and the holding time is 30min, to obtain a chromium-nickel co-diffusion coating coated on the metal pipe workpiece.

[0136] In Example 4, the obtained chromium-nickel co-penetration coating was subjected to an oxidation resistance test, as follows: After cyclic oxidation at 1000°C for 100 h, the oxidation weight gain of the prepared chromium-nickel co-penetration coating sample was 0.033 mg / mm 2 The oxidation weight gain of the high-temperature alloy matrix is ​​0.108 mg / mm 2 , the oxidation rate decreased by 69.4%.

[0137] In Example 4, the resulting chromium-nickel co-infiltrated coating was subjected to wear resistance testing. Specifically, the microhardness of the prepared chromium-nickel co-infiltrated coating was approximately 419.6 HV, while the microhardness of the high-temperature alloy substrate was approximately 300 HV, representing a hardness increase of approximately 1.4 times. Furthermore, in accordance with the national standard GB / T 12444-2006, "Metallic Materials, Test Methods for Wear," the wear resistance of the high-temperature alloy and coating was tested. Under the same test conditions, the friction wear of the coated sample was reduced by approximately 18.3%, and the friction coefficient was reduced by approximately 6.2%.

[0138] The present disclosure provides a chromium-nickel co-penetration coating and its preparation method and application, which have the following beneficial effects compared with the prior art:

[0139] First, the chromium-nickel high-temperature corrosion-resistant coating and its preparation method disclosed herein do not require vacuum conditions, and the preparation process is simple. At the same time, the chromium-nickel co-penetration coating has high preparation efficiency, low pollution, adjustable thickness, good wear resistance, and especially excellent resistance to high and low temperature corrosion and steam oxidation.

[0140] Second, the present disclosure mixes the solid phase component with the liquid phase component to form a chromium-nickel co-diffusion slurry, which is easy to coat the surface of the metal workpiece and has a strong bonding force with the workpiece surface.

[0141] Third, the metal powder raw material disclosed in the present disclosure is suitable for various metal workpieces whose surfaces need to be strengthened, including carbon steel, austenitic stainless steel, and high-temperature alloys, and has a wide range of applications and strong practicality.

[0142] Fourth, the present invention also undergoes a shot peening process before co-penetration coating to increase the specific surface area of ​​the metal workpiece, improve the penetration of metal elements and the adhesion of the coating, thereby further enhancing the strength and corrosion resistance of the surface coating.

[0143] It is understood that the above embodiments are merely exemplary embodiments for illustrating the principles of the present disclosure, and the present disclosure is not limited thereto. Those skilled in the art may make various modifications and improvements without departing from the spirit and substance of the present disclosure, and such modifications and improvements are also considered to be within the scope of protection of the present disclosure.

Claims

1. A method for preparing a chromium-nickel co-penetration coating, characterized in that: The preparation method comprises: Surface pretreatment of metal workpieces; Shot peening is performed on the pretreated metal workpiece; Apply the chromium-nickel co-diffusion slurry once on the surface of the metal workpiece after shot blasting, pre-dry at 60-85°C for 5-30 minutes, then dry at 100-160°C for 30-60 minutes, and finally cure at a medium temperature of 250-300°C for 20-60 minutes; The dried and solidified metal workpiece is sintered at 500-650°C for 5-30 minutes to obtain a chromium-nickel co-penetration coating on the surface of the metal workpiece; wherein, The chromium-nickel co-diffusion slurry includes a solid phase component and a liquid phase component; the solid-liquid ratio of the solid phase component to the liquid phase component is 10:(1-5); the solid phase component includes: 50-80% chromium powder; 1-10% nickel powder; 10-20% alumina; 0-20% chromium oxide, the sum of the mass percentages of the above solid phase components is 100%; The liquid phase components include: 10-30% Al(H2PO4)3; 15-25% water glass; 5-10% ammonium iodide; 10-40% chromium oxide; 15-35% of magnesium oxide, the sum of the mass percentages of the above liquid phase components is 100%.

2. The preparation method according to claim 1, characterized in that The chromium powder, the nickel powder, the aluminum oxide and the chromium oxide are ball-milled for 6 to 24 hours at a rotation speed of 350 to 400 r / min to obtain a solid phase component.

3. The preparation method according to claim 1 or 2, characterized in that The coating thickness of the chromium-nickel co-diffusion slurry coated on the surface of the metal workpiece is 0.1 to 1.0 mm.

4. The preparation method according to claim 1 or 2, characterized in that In the shot peening treatment, the diameter of the shot peening particles is 0.1 to 1.0 mm, the shot peening pressure is 0.5 to 2.0 MPa, and the shot peening time is 10 to 30 minutes.

5. A chromium-nickel co-penetration coating, characterized in that: The chromium-nickel co-penetration coating is prepared by the preparation method according to any one of claims 1 to 4.

6. An application of a chromium-nickel co-penetration coating, characterized in that: The chromium-nickel co-diffusion coating according to claim 5 is applied to the surface of a metal workpiece made of carbon steel, austenitic steel or high-temperature alloy.

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