A method for improving the oxidation resistance of the inner and outer walls of a workpiece

Abstract

This disclosure proposes a method for improving the oxidation resistance of the inner and outer walls of a workpiece, belonging to the field of material surface alloying and coating preparation technology. The method includes: mixing Cr and Ni infiltration sources, modifiers, and activators; stirring, wet ball milling, and drying to obtain a solid-phase cladding alloy powder; cleaning the surface of the workpiece to be plated; placing the solid-phase cladding alloy powder into a powder storage tank; uniformly conveying the solid-phase cladding alloy powder to a plasma generator via a powder feeder of a plasma cladding machine; adjusting process parameters via a control panel; and placing the cleaned workpiece under an inert atmosphere for plasma cladding treatment. After cooling, a chromium-nickel anti-oxidation coating with a thickness of 1.15–2.85 mm is obtained on the surface of the workpiece. This process features concentrated heat, short treatment time, minimal heat-affected zone in the cladding zone, high bonding strength between the coating and the base material, and a relatively thick coating, effectively improving the oxidation resistance of the inner and outer walls of the workpiece and thus extending its service life.

Description

Technical Field

[0001] This disclosure belongs to the field of material surface alloying and coating preparation technology, specifically relating to a method for improving the oxidation resistance of the inner and outer walls of a workpiece. Background Technology

[0002] Taking the power industry as an example, pipe blockage and rupture accidents caused by oxide scale on the inner wall of flow-through components account for more than 50% of boiler non-shutdown accidents, resulting in an increase of more than 20% in the unit's operating and material costs. Therefore, researching and developing corrosion-resistant and oxidation-resistant technologies for the inner and outer wall surfaces of pipes used in boiler units is of great practical significance.

[0003] Different metal oxide films possess varying properties. Among them, metals exhibiting dense, high-temperature resistant, and wear-resistant oxide films have attracted attention in the coating field. Constructing an oxide film on the workpiece surface helps improve its corrosion resistance and other properties. Cr, as a diffusion metal element, possesses inherent corrosion resistance and further oxidizes in the environment, forming a dense chromium oxide (Cr2O3) layer on the material surface, thus protecting the workpiece. However, during the Cr diffusion process, it has been found that the Cr layer is often very thin, typically on the micrometer scale, thus offering limited protection to the workpiece.

[0004] Therefore, in order to solve the above-mentioned technical problems, a new method is needed to enhance the penetration of Cr and construct a thicker coating, thereby improving the oxidation resistance of the inner and outer walls of the workpiece and extending the service life of the workpiece. Summary of the Invention

[0005] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a method for improving the oxidation resistance of the inner and outer walls of a workpiece.

[0006] This disclosure provides a method for improving the oxidation resistance of the inner and outer walls of a workpiece, the method comprising:

[0007] Cr and Ni infiltration source, modifier and activator are mixed, and then stirred, wet ball milled and dried to obtain solid phase cladding alloy powder;

[0008] The workpiece to be plated undergoes surface cleaning treatment;

[0009] The solid phase cladding alloy powder is placed in a powder storage tank and uniformly transported to the plasma generator by the powder feeder of the plasma cladding machine. The cleaned workpiece is then subjected to plasma cladding treatment in an inert atmosphere. After cooling, a chromium-nickel anti-oxidation coating with a thickness of 1.15 to 2.85 mm is obtained on the surface of the workpiece.

[0010] Optionally, the modifier is any one of Hf, La, Y, Nd, and Zr.

[0011] Optionally, the activator is any one of NH4Cl, NH4I, CrCl3, and CrCl3·6H2O.

[0012] Optionally, the Cr and Ni infiltration sources are Cr powder and Ni powder with a particle size of less than or equal to 1000 mesh.

[0013] Optionally, in the solid-phase cladding alloy powder, by mass percentage,

[0014] The Cr content is 50-80%;

[0015] The Ni content is 15-45%;

[0016] The content of the modifier is 2-5%;

[0017] The content of the activator is 1-5%.

[0018] Optionally, in plasma cladding, the cladding current is 80-120A, the feed rate is 18-22g / min, the scanning rate is 20-40cm / min, the nozzle height is 8-12mm, the rotation speed is 2-5r / min, the ion gas flow rate is 0.2-0.3L / min, and the protective gas flow rate is 18-20L / min.

[0019] Optionally, the inert atmosphere is Ar or N2.

[0020] Optionally, in the wet ball milling process, the medium is anhydrous ethanol, the ball milling speed is 350-400 rpm, and the ball milling time is 12-24 h.

[0021] Optionally, in the drying process, the drying temperature is 80-120℃ and the drying time is 12-24h.

[0022] Optionally, the thickness of the chromium-nickel anti-oxidation coating is 2.18-2.85 mm.

[0023] This disclosure proposes a method for improving the oxidation resistance of the inner and outer walls of a workpiece. The method includes: mixing Cr and Ni infiltration sources, modifiers, and activators, followed by stirring, wet ball milling, and drying to obtain a solid-phase cladding alloy powder; cleaning the surface of the workpiece to be plated; placing the solid-phase cladding alloy powder into a powder storage tank; uniformly conveying the solid-phase cladding alloy powder to a plasma generator via a powder feeder of a plasma cladding machine; and subjecting the cleaned workpiece to plasma cladding under an inert atmosphere. After cooling, a chromium-nickel anti-oxidation coating with a thickness of 1.15–2.85 mm is obtained on the surface of the workpiece. This disclosure uses a plasma cladding process to prepare the coating. This process has concentrated heat, short action time, small heat-affected zone in the cladding area, high bonding strength between the coating and the base material, and a relatively thick coating, effectively improving the oxidation resistance of the inner and outer walls of the workpiece, thereby extending the service life of the workpiece. Attached Figure Description

[0024] Figure 1 This is a flowchart illustrating a method for improving the oxidation resistance of the inner and outer walls of a workpiece according to an embodiment of the present disclosure.

[0025] Figure 2 The image shows the cross-sectional morphology of the chromium-nickel anti-oxidation coating of Embodiment 1 of this disclosure. Detailed Implementation

[0026] 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.

[0027] like Figure 1 As shown, this disclosure provides a method S100 for improving the oxidation resistance of the inner and outer walls of a workpiece, specifically including the following steps S110 to S130:

[0028] S110: Cr, Ni infiltration source, modifier and activator are mixed, and then stirred, wet ball milled and dried to obtain solid phase cladding alloy powder.

[0029] It should be understood that when the Cr and Ni infiltration sources are Cr powder and Ni powder, the smaller the particle size of the Cr powder and Ni powder, the smaller the particle size of the intermetallic compounds formed in the cladding layer and the more uniform the distribution. Conversely, the larger the particle size, the denser the final cladding coating. Therefore, in this embodiment, the Cr powder and Ni powder preferably have a particle size of 1000 mesh. That is, the Cr powder and Ni powder are sieved through a 1000-mesh sieve and used as infiltration sources. The cladding coating prepared from powder with this particle size has good overall performance.

[0030] In some preferred embodiments, the Cr powder content is preferably 50-80%, for example, 50%, 60%, 70%, or 80%. The Ni powder content is preferably 15-45%, for example, 15%, 20%, 25%, 30%, 40%, or 45%.

[0031] In this embodiment, by using chromium powder and nickel powder as infiltration sources, chromium and nickel elements can form a substitution solid solution. Compared with a single chromium infiltration or nickel infiltration layer, chromium-nickel co-infiltration can significantly improve the oxidation resistance of the infiltration layer.

[0032] In other preferred embodiments, the modifier is any one of Hf, La, Y, Nd, and Zr. By adding other elements such as Hf to the cladding powder component, the non-melting property of Hf and other elements during the cladding process allows them to become non-uniform nucleation points of grains during the solidification of the cladding layer. This facilitates the transformation of the cladding layer structure from coarse dendrites (formed due to rapid cooling after cladding) to cellular crystals, reducing the component segregation generated within and between grains of the coating layer structure. In addition, Hf and other elements can also form solid solutions with nickel and chromium. Other oxidation products such as HfO2 formed at high temperatures can pin the oxide film, enhance the anti-peeling performance of the oxide, and thus improve the high-temperature oxidation resistance of the cladding layer.

[0033] As a further preferred embodiment, the content of the modifier is preferably 2-5%, for example, 2%, 3%, 4%, or 5%.

[0034] In some other preferred embodiments, the activator is any one of NH4Cl, NH4I, CrCl3 and CrCl3·6H2O. Other components such as NH4Cl can generate active transition halides through chemical reactions, which promotes the formation of a good metallurgical bond between the coating and the substrate. The activator can play a role in promoting penetration and activation, thereby improving the penetration rate and coating quality.

[0035] As a further preferred embodiment, the content of the activator is preferably 1-5%, for example, 1%, 2%, 3%, 4%, or 5%.

[0036] It should be understood that, in order to ensure uniform mixing of the components, the solid-phase cladding alloy powder can be ball-milled. For example, in a wet ball mill, the medium for wet milling is anhydrous ethanol. The solid-phase cladding alloy powder is ball-milled at a speed of 350-400 rpm for a time of 12-24 hours.

[0037] In some other preferred embodiments, after wet ball milling, the drying temperature for drying the solid-phase clad alloy powder is 80-120°C, and the drying time is 12-24 hours.

[0038] S120. Perform surface cleaning treatment on the workpiece to be plated.

[0039] Specifically, the surface of the workpiece to be plated is cleaned with a high-pressure water gun for 5-10 minutes to remove oil stains, dirt, and oxide scale, and then rinsed with alcohol or acetone to provide a clean surface with a metallic luster for subsequent cladding.

[0040] S130. The solid phase cladding alloy powder is placed in a powder storage tank. The solid phase cladding powder is uniformly conveyed to the plasma generator through the powder feeder of the plasma cladding machine. The process parameters are adjusted through the control panel. The cleaned workpiece to be plated is placed in an inert atmosphere for plasma cladding treatment. After cooling treatment, a chromium-nickel anti-oxidation coating with a thickness of 1.15 to 2.85 mm is obtained on the surface of the workpiece to be plated.

[0041] Specifically, in plasma cladding, the cladding current is 80-120A, the feed rate is 18-22 g / min, the scanning rate is 20-40 cm / min, the nozzle height is 8-12 mm, the rotation speed is 2-5 r / min, the ion gas flow rate is 0.2-0.3 L / min, the protective gas flow rate is 18-20 L / min, and the inert atmosphere is Ar or N2. Under these process parameters, it is beneficial to improve the diffusion rate and film-substrate adhesion, thereby improving the coating thickness and quality, and meeting the application requirements of the workpiece.

[0042] In some preferred embodiments, the thickness of the chromium-nickel anti-oxidation coating is preferably 1.15-2.85 mm, and may also be preferably 2.18-2.85 mm, etc.

[0043] It should be understood that after the cladding is completed, a high-pressure water gun can be used to rinse off any residue on the workpiece surface, and it can be air-dried naturally to obtain a smooth and even chromium-nickel anti-oxidation coating.

[0044] In this embodiment, a coating is prepared by plasma cladding. During the preparation process, a chromium-nickel anti-oxidation coating with a thickness of 1.15-2.85 mm and good metallurgical bonding is prepared by adjusting the composition of the cladding powder and the main process parameters such as plasma cladding parameters. This process has concentrated heat, short action time, small heat-affected zone, high bonding strength between the coating and the base material, and a relatively thick coating thickness, which effectively improves the oxidation resistance of the inner and outer walls of the workpiece, thereby extending the service life of the workpiece coating.

[0045] The chromium-nickel anti-oxidation coating prepared in this embodiment has an oxidation resistance that is 18-62 times higher than that of the base material in a pure water vapor environment at 600°C and 20-84 times higher than that of the base material in a pure water vapor environment at 650°C. This demonstrates that the chromium-nickel anti-oxidation coating prepared by the method disclosed in this invention effectively improves the oxidation resistance of the alloy base material in a water vapor environment.

[0046] It should be noted that the method of this embodiment can be applied to austenitic steel and high-temperature alloy components used in large boilers, oil and gas field pipelines and other workpieces with large length-to-diameter ratios and various complex shapes. It is especially suitable for boiler pipelines, with strong practicality, high diffusion rate, excellent membrane-substrate adhesion, and excellent industrial mass production benefits.

[0047] The following will further illustrate the method for improving the oxidation resistance of the inner and outer walls of a workpiece with reference to several specific embodiments:

[0048] Example 1

[0049] Step 1: Weigh the components of the solid cladding alloy powder according to the mass ratio, including 50% Cr, 45% Ni, 2% NH4Cl and 3% Hf, place it in a planetary ball mill and wet-mill it with ethanol at 400 rpm for 24 h, and then vacuum dry it at 100℃ for 24 h to obtain the solid cladding alloy powder.

[0050] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0051] Step 3: Place the solid phase cladding alloy powder into the powder storage tank, and use the powder feeder of the plasma cladding machine to evenly transport the solid phase cladding alloy powder to the plasma generator. Adjust the process parameters through the control panel, place the workpiece to be plated in an inert atmosphere for plasma cladding treatment, and cool it down. A chromium-nickel anti-oxidation coating with a thickness of 2.35mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0052] The plasma cladding process parameters are as follows: cladding current is 120A, feed rate is 20g / min, scanning rate is 35cm / min, nozzle height is 10mm, rotation speed is 2r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar or N2.

[0053] Combination Figure 2 It can be seen that the chromium-nickel anti-oxidation coating has a uniform microstructure, moderate thickness, sufficient Cr atom diffusion, and good metallurgical bond between the infiltrated layer and the substrate, making it difficult to fall off.

[0054] Example 2

[0055] The steps in this example are the same as in Example 1, and it is a parallel experiment of Example 1, in which a chromium-nickel anti-oxidation coating with a thickness of 2.45 mm is obtained on the surface of the workpiece to be plated.

[0056] Example 3

[0057] The steps in this example are the same as in Example 1, and it is a parallel experiment of Example 1, in which a chromium-nickel anti-oxidation coating with a thickness of 2.18 mm is obtained on the surface of the workpiece to be plated.

[0058] Example 4

[0059] The steps in this example are the same as in Example 1, except that the cladding current in the plasma cladding process parameters in step S3 is changed to 80A, while other conditions remain unchanged, and a chromium-nickel anti-oxidation coating with a thickness of 1.15mm is obtained on the surface of the workpiece to be plated.

[0060] Example 5

[0061] In this example, each step is the same as in Example 1, except that the cladding current in the plasma cladding process parameters in step S3 is changed to 100A, while other conditions remain unchanged, and a chromium-nickel anti-oxidation coating with a thickness of 1.54mm is obtained on the surface of the workpiece to be plated.

[0062] Example 6

[0063] In this example, each step is the same as in Example 1, except that the feed rate in the plasma cladding process parameters in step S3 is changed to 18 g / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.32 mm on the surface of the workpiece to be plated.

[0064] Example 7

[0065] In this example, each step is the same as in Example 1, except that the feed rate in the plasma cladding process parameters in step S3 is changed to 22 g / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.41 mm on the surface of the workpiece to be plated.

[0066] Example 8

[0067] In this example, each step is the same as in Example 1, except that the scanning rate in the plasma cladding process parameters in step S3 is changed to 20 cm / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.37 mm on the surface of the workpiece to be plated.

[0068] Example 9

[0069] In this example, each step is the same as in Example 1, except that the scanning rate in the plasma cladding process parameters in step S3 is changed to 40 cm / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.68 mm on the surface of the workpiece to be plated.

[0070] Example 10

[0071] In this example, each step is the same as in Example 1, except that the nozzle height in step S3 of the plasma cladding process is changed to 8 mm and the rotation speed is changed to 5 r / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.51 mm on the surface of the workpiece to be plated.

[0072] Example 11

[0073] In this example, each step is the same as in Example 1, except that the nozzle height in step S3 of the plasma cladding process is changed to 12mm and the rotation speed is changed to 5r / min, while other conditions remain unchanged, resulting in a chromium-nickel anti-oxidation coating with a thickness of 2.36mm on the surface of the workpiece to be plated.

[0074] According to the results of Examples 1-11, the cladding current has a significant impact on the coating thickness. Reducing the cladding current results in a decrease in coating thickness. The nozzle height, rotation speed, feed rate, and scanning rate have relatively small effects on coating thickness. However, a higher scanning rate, a lower nozzle height, and a higher rotation speed all contribute to increasing the coating thickness.

[0075] Table 1. Plasma cladding process parameters and coating thickness in Examples 1-11

[0076]

[0077]

[0078] Example 12

[0079] Step 1: Weigh the components of the solid cladding alloy powder according to the mass ratio, including 80% Cr, 15% Ni, 2% NH4Cl and 3% Hf, place them in a planetary ball mill and wet-mill with ethanol at 350 rpm for 24 h, and then vacuum dry at 100℃ for 24 h to obtain the solid cladding alloy powder.

[0080] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0081] Step 3: Place the solid phase cladding alloy powder into the feed port of the plasma cladding machine, and place the workpiece to be plated in an inert atmosphere for plasma cladding treatment and cooling treatment. A chromium-nickel anti-oxidation coating with a thickness of 1.38 mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0082] The plasma cladding process parameters are as follows: cladding current is 80A, feed rate is 20g / min, scanning rate is 40cm / min, nozzle height is 12mm, rotation speed is 3r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar or N2. After cladding, the workpiece surface residue is rinsed with a high-pressure water gun or high-pressure airflow and then air-dried naturally.

[0083] Example 13

[0084] Step 1: Weigh the solid components according to the mass ratio, including 60% Cr, 30% Ni, 5% NH4Cl and 5% Hf, place them in a planetary ball mill and wet-mill with ethanol at 400 rpm for 24 h, and then vacuum dry at 100℃ for 24 h to obtain cladding powder.

[0085] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0086] Step 3: Place the solid phase cladding alloy powder into the feed port of the plasma cladding machine, and place the workpiece to be plated in an inert atmosphere for plasma cladding treatment and cooling treatment. A chromium-nickel anti-oxidation coating with a thickness of 1.87 mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0087] The plasma cladding process parameters are as follows: cladding current is 100A, feed rate is 18g / min, scanning rate is 35cm / min, nozzle height is 10mm, rotation speed is 3r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar. After cladding, the workpiece surface residue is rinsed with a high-pressure water gun and then air-dried.

[0088] Example 14

[0089] Step 1: Weigh the solid components according to the mass ratio, including 70% Cr, 25% Ni, 2% NH4Cl and 3% Hf, place them in a planetary ball mill and wet-mill with ethanol at 400 rpm for 24 h, and then vacuum dry at 100℃ for 24 h to obtain cladding powder.

[0090] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0091] Step 3: Place the solid phase cladding alloy powder into the feed port of the plasma cladding machine, and place the workpiece to be plated in an inert atmosphere for plasma cladding treatment and cooling treatment. A chromium-nickel anti-oxidation coating with a thickness of 2.33 mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0092] The plasma cladding process parameters are as follows: cladding current is 120A, feed rate is 20g / min, scanning rate is 35cm / min, nozzle height is 10mm, rotation speed is 2r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar. After cladding, the workpiece surface residue is rinsed with a high-pressure water gun and then air-dried.

[0093] Example 15

[0094] Step 1: Weigh the solid components according to the mass ratio, including 65% Cr, 30% Ni, 2% NH4Cl and 3% Hf, place them in a planetary ball mill and wet-mill with ethanol at 400 rpm for 24 h, and then vacuum dry at 100℃ for 24 h to obtain cladding powder.

[0095] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0096] Step 3: Place the solid phase cladding alloy powder into the feed port of the plasma cladding machine, and place the workpiece to be plated in an inert atmosphere for plasma cladding treatment and cooling treatment. A chromium-nickel anti-oxidation coating with a thickness of 2.27 mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0097] The plasma cladding process parameters are as follows: cladding current is 120A, feed rate is 20g / min, scanning rate is 35cm / min, nozzle height is 10mm, rotation speed is 2r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar. After cladding, the workpiece surface residue is rinsed with a high-pressure water gun and then air-dried.

[0098] Example 16

[0099] Step 1: Weigh the solid components according to the mass ratio, including 55% Cr, 40% Ni, 2% NH4Cl and 3% Hf, place them in a planetary ball mill and wet-mill with ethanol at 400 rpm for 24 h, and then vacuum dry at 100℃ for 24 h to obtain cladding powder.

[0100] Step 2: Clean the surface of the workpiece with a high-pressure water gun for 5 minutes, and then rinse it with alcohol or acetone.

[0101] Step 3: Place the solid phase cladding alloy powder into the feed port of the plasma cladding machine, and place the workpiece to be plated in an inert atmosphere for plasma cladding treatment and cooling treatment. A chromium-nickel anti-oxidation coating with a thickness of 2.06 mm is obtained on the surface of the workpiece. After cladding, use a high-pressure water gun or high-pressure airflow to rinse off the residue on the surface of the workpiece and let it air dry naturally.

[0102] The plasma cladding process parameters are as follows: cladding current is 120A, feed rate is 20g / min, scanning rate is 35cm / min, nozzle height is 10mm, rotation speed is 2r / min, ion gas flow rate is 0.2L / min, protective gas flow rate is 19L / min, and inert gas is Ar. After cladding, the workpiece surface residue is rinsed with a high-pressure water gun and then air-dried.

[0103] Table 2. Plasma cladding process parameters and coating thickness in Examples 12-16

[0104]

[0105] In summary, based on the results of Examples 1-16, the coating formed by this disclosure is relatively thick, with a thickness between 1.15-2.85 mm. Compared with the current coatings with a thickness of micrometers, it can effectively improve the oxidation resistance of the inner and outer walls of the workpiece, thereby extending the service life of the workpiece.

[0106] This disclosure proposes a method for improving the oxidation resistance of the inner and outer walls of a workpiece, which has the following advantages compared to the prior art:

[0107] First, the present disclosure uses a plasma cladding process to prepare a coating. This process has concentrated heat, short action time, small heat-affected zone in the cladding area, and high bonding strength between the coating and the base material.

[0108] Secondly, this disclosure achieves the effects of catalytic penetration and activation by adding activators such as NH4Cl to the solid phase cladding alloy powder components, thereby improving the penetration rate and coating quality.

[0109] Third, this disclosure can pin the oxide film and improve the bonding strength between the anti-oxidation coating and the substrate by adding modifying elements such as Hf to the solid phase cladding alloy powder components;

[0110] Fourth, the coating obtained by this disclosure has a uniform microstructure, moderate thickness, and sufficient Cr atom diffusion. The diffusion layer and the substrate have a good metallurgical bond and are not easy to fall off. It is suitable for austenitic steel and high-temperature alloy parts with large length-to-diameter ratios and various complex shapes, such as large boilers and oil and gas field pipelines, and has excellent industrial mass production benefits.

[0111] 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 for improving the oxidation resistance of the inner and outer walls of a workpiece, characterized in that, The method comprises the following steps: Cr, Ni source, modifier and activator are mixed, stirred, wet ball-milled and dried to obtain a solid-phase cladding alloy powder; the modifier is any one of Hf, La, Y, Nd and Zr; the activator is any one of NH4Cl, NH4I, CrCl3 and CrCl3·6H2O; in the solid-phase cladding alloy powder, the content of Cr is 50-80% by mass; the content of Ni is 15-45% by mass; the content of the modifier is 2-5% by mass; the content of the activator is 1-5% by mass; The content of the activator is 1-5% by mass; The surface of the workpiece to be plated is cleaned; The solid-phase cladding alloy powder is placed in a powder storage tank, and is uniformly delivered to a plasma generating device by a powder feeder of a plasma cladding machine; the cleaned workpiece to be plated is placed in an inert atmosphere for plasma cladding treatment, and a chromium-nickel oxidation-resistant coating with a thickness of 1.15-2.85 mm is obtained on the surface of the workpiece to be plated after cooling.

2. The method of claim 1, wherein, The Cr and Ni source is Cr powder and Ni powder with a particle size of 1000 mesh or less.

3. The method according to any one of claims 1 to 2, characterized in that, In the plasma cladding treatment, the cladding current is 80-120 A, the feeding rate is 18-22 g / min, the scanning rate is 20-40 cm / min, the nozzle height is 8-12 mm, the rotation speed is 2-5 r / min, the ion gas flow rate is 0.2-0.3 L / min, and the protective gas flow rate is 18-20 L / min.

4. The method according to any one of claims 1 to 2, characterized in that, The inert atmosphere is Ar or N2.

5. The method according to any one of claims 1 to 2, characterized in that, In the wet ball-milling treatment, the medium is anhydrous ethanol, the ball-milling rotation speed is 350-400 rpm, and the ball-milling time is 12-24 h.

6. The method according to any one of claims 1 to 2, characterized in that, In the drying treatment, the drying temperature is 80-120℃, and the drying time is 12-24 h.

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