Chromium-nickel cladding coating suitable for outer wall of flue gas side of boiler pipeline and preparation method of chromium-nickel cladding coating

Abstract

The invention discloses a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of a boiler pipeline, which is characterized in that cladding powder is prepared according to a mass ratio, and after the surface of a workpiece to be plated is cleaned, a chromium-nickel anti-oxidation coating is prepared through plasma cladding; wherein the solid-phase cladding powder comprises the following components in percentage by mass: 50 to 80 percent of Cr, 10 to 40 percent of Ni, 2 to 5 percent of CeO2, 2 to 5 percent of FeV80 and 0 to 5 percent of NH4Cl. The chromium-nickel cladding coating suitable for the outer wall of the flue gas side of the boiler pipeline is uniform in structure, moderate in thickness, sufficient in Cr atom diffusion, good in metallurgical bonding with a base body, not prone to falling off, suitable for austenitic steel and high-temperature alloy parts used for workpieces with large length-diameter ratios and various complex shapes such as large boilers and oil and gas field transportation pipelines, and capable of achieving the purpose of improving the performance of the coating and the application of the chromium-nickel cladding coating on the outer wall of the flue gas side of the boiler pipeline. And the method has excellent industrial batch production benefits.

Description

Technical Field

[0001] The invention belongs to the field of material surface alloying and coating preparation, and specifically relates to a chromium-nickel cladding coating suitable for the outer wall of a flue gas side of a boiler pipeline and a preparation method thereof. Background Art

[0002] The high-temperature corrosion on the flue gas side of the boiler tube in coal-fired thermal power plants has become a major hidden danger to the safe operation of the power plant. The corrosion of the metal on the flue gas side heating surface is mainly caused by the material surface and the surrounding corrosive media, such as SO in the flue gas formed after the combustion of coal powder. 2 , boiler feed water, boiler water, steam, air and fly ash / waste residue, etc., a series of chemical reactions occur, resulting in metal corrosion damage. In addition, high-temperature corrosion on the flue gas side is also related to the deposition of low-melting-point sulfates. The melting points of these sediment components are all in the range of 400-900°C, which will also promote high-temperature corrosion of boiler tubes. As the operating parameters of thermal power units continue to increase, the target parameters of advanced supercritical units have increased to 700°C / 35MPa, which puts more stringent requirements on the corrosion resistance / oxidation performance and organizational structure stability of boiler tube materials.

[0003] In order to improve the flue gas corrosion resistance and oxidation resistance of boiler tube walls, the tube wall structure is generally changed to enable the alloy to quickly grow Cr 2 O 3 But Cr 2 O 3 The stability in steam above 600℃ is poor, and the loose oxide film caused by volatile products will cause the oxide film to peel off, and further lead to pipe blockage and pipe explosion accidents; in addition, the Cr content in the alloy matrix is ​​relatively low. With the increase of service time, when the Cr content required for the growth of the oxide film cannot be replenished, the oxidation resistance of the alloy will also drop sharply. Therefore, it is of great practical significance to research and develop corrosion-resistant and oxidation-resistant coatings suitable for the inner and outer wall surfaces of pipelines for boiler units. Summary of the invention

[0004] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of a boiler pipe.

[0007] In order to solve the above technical problems, the present invention provides the following technical solution: a method for preparing a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of a boiler pipe, characterized in that: it comprises:

[0008] Weigh and prepare each solid phase component according to the mass ratio, and prepare the solid phase cladding infiltrant after stirring, ball milling and drying for use;

[0009] Clean the surface of the workpiece to be plated and pour enough cladding powder into the feeding port;

[0010] The workpiece is placed in an inert atmosphere for plasma cladding, and a chromium-nickel anti-oxidation coating is obtained after cooling, and the cladding residue is treated.

[0011] As a preferred embodiment of the preparation method of the present invention, the solid phase components include Cr and Ni powders as infiltration sources, NH 4 Cl, modifier CeO 2 and FeV 80 ; Among them, Cr and Ni powders were sieved through a 1000-mesh sieve.

[0012] As a preferred embodiment of the preparation method of the present invention, the solid phase components are weighed by mass percentage and include 50-80% Cr, 10-40% Ni, 2-5% CeO 2 , 2~5%FeV 80 and 0-5% NH 4 Cl.

[0013] As a preferred embodiment of the preparation method of the present invention, the wet grinding medium of the ball mill is anhydrous ethanol, the ball milling speed is 350-400 rpm, and the time is 12-24 hours.

[0014] As a preferred embodiment of the preparation method of the present invention, the drying condition is vacuum drying at 80-120° C. for 12-24 hours.

[0015] As a preferred embodiment of the preparation method of the present invention, the plasma cladding process parameters are as follows: cladding current is 80-120A, feed rate is 18-22g / min, scanning rate is 20-40cm / min, nozzle height is 8-12mm, rotation speed is 2-5r / min, ion gas flow rate is 0.2-0.3L / min, protective gas flow rate is 18-20L / min, inert gas is Ar or N 2 .

[0016] Another object of the present invention is to overcome the deficiencies in the prior art and provide a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of a boiler pipe.

[0017] As a preferred embodiment of the chromium-nickel cladding coating of the present invention, the chromium-nickel cladding coating is metallurgically bonded to the substrate, has a thickness of 0.1 to 2 mm, and has a corrosion rate of less than 0.2 mg / cm2 in a 650°C flue gas environment for 200 h. 3 .

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention adds a modifier CeO to the cladding powder. 2 , FeV 80 , which reduces Cr 2 O 3 The critical concentration of oxide film formation and the formation of network chromium carbide are reduced, thus improving the corrosion resistance of the coating. The addition of rare earth oxides can pin the grain boundaries, refine the matrix structure, improve the surface hardness, and enhance the bonding strength between the coating and the base material in the form of second phase precipitation on the basis of halide-promoted diffusion. In addition, rare earth oxides can reduce Cr 2 O 3 The critical concentration of oxide film formation; in addition, the modifier FeV80 can inhibit the formation of network chromium carbide and increase Cr 2 O 3 Oxide film density.

[0020] (2) The present invention adds NH 4 Cl plays a role in promoting penetration and activation, improving the penetration rate and coating quality;

[0021] (3) The present invention prepares the coating by a plasma cladding process, which has concentrated heat, short action time, small thermal impact in the cladding zone, and high bonding strength between the coating and the base material;

[0022] (4) The present invention prepares the coating through an integrated production line, and the coating production efficiency is high, the thickness is controllable, the process repeatability is high, and it has strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0024] Figure 1 The cross-sectional morphology of the chromium-nickel cladding coating suitable for the outer wall of the flue gas side of the boiler pipe in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0026] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0027] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0028] The raw materials used in the present invention are: TP347H seamless steel pipe, Shengde Xintai New Materials Co., Ltd.; metal powder, Shanghai Jinxindun Metal Materials Technology Co., Ltd.

[0029] The instruments used in the embodiments of the present invention include: laser cladding equipment (Golden Weike Laser Technology Co., Ltd., model: GKS-LC3008R); scanning electron microscope SEM (model Zeiss-Sigma HD) with energy spectrum EDS (model Oxford) and backscattering HDBSD (model Zeiss-Sigma HD).

[0030] The performance testing method in the embodiment of the present invention is: in a synthetic coal ash and synthetic flue gas environment at 650°C, the coal ash component SiO 2 47.36%, Al2O323.96, Fe 2 O 3 16.50%, CaO4.06%, MgO1.38%, Na 2 SO 4 1.81%, K 2 SO 4 1.18% TiO 2 2.94%, flue gas composition CO 2 12.600%, CO2.100%, SO 2 0.296%、N 2 74.640%、H 2 O6.510%, O 2 3.780%. The fly ash is fully ground in a mortar and diluted with alcohol to form a suspension. The amount of fly ash applied is controlled to be about 20 mg / cm 2The synthetic flue gas flow rate is 1L / min. After 200 hours, a sample is taken out and washed in boiling water for 48 hours and then dried and weighed. Calculate the weight loss per unit area (unit: mg / cm 3 ), evaluate the corrosion resistance of materials.

[0031] Example 1

[0032] (1) Weigh the solid phase components according to mass ratio, including 50% Cr, 40% Ni, and 5% CeO 2 and 5% FeV 80 , place it in a planetary ball mill at 400rpm for ethanol wet grinding for 24h, and then dry it in vacuum at 100℃ for 24h to obtain the cladding powder.

[0033] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0034] (3) The plasma cladding process parameters are: cladding current 80A, feed rate 18g / min, scanning rate 25cm / min, nozzle height 12mm, rotation speed 2r / min, ion gas flow rate 0.2L / min, shielding gas flow rate 19L / min, inert gas Ar or N 2 After cladding, use a high-pressure water gun or high-pressure air flow to flush the residue on the workpiece surface and let it dry naturally.

[0035] The processes of Examples 2 to 11 are the same as those of Example 1. Examples 1 to 11 maintain the same penetrant component ratio. The specific conditions are detailed in Table 1. Table 1 is the specific parameters of Examples 1 to 11 of the method for preparing the chromium-nickel cladding coating on the surface of the boiler tube wall. According to the preparation steps in the above Example 1 and the specific preparation parameters in the table, chromium-nickel coatings of different thicknesses can be obtained.

[0036] Table 1

[0037]

[0038]

[0039] By analyzing and studying the above examples, the thickness of the infiltration layer is measured to be about 0.15 to 1.39 mm. The specific results are shown in Table 1. The cross-sectional morphology of the typical coating is as follows: Figure 1 As shown in Table 1 and the cross-sectional morphology, it is found that the diffusion layer has a uniform structure, moderate thickness, sufficient diffusion of Cr atoms, a good metallurgical bond between the diffusion layer and the matrix, and is not easy to fall off.

[0040] Example 12

[0041] (1) Weigh the solid components according to mass ratio, including 80% Cr, 10% Ni, and 2% CeO 2, 3% FeV 80 and 5% NH 4 Cl, placed it in a planetary ball mill at 350 rpm with ethanol wet grinding for 24 h, and then dried at 100 °C in vacuum for 24 h to obtain the cladding powder.

[0042] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0043] (3) The plasma cladding process parameters are: cladding current 80A, feed rate 20g / min, scanning rate 40cm / min, nozzle height 12mm, rotation speed 3r / min, ion gas flow rate 0.2L / min, shielding gas flow rate 19L / min, inert gas Ar or N 2 After cladding, use a high-pressure water gun or high-pressure air flow to flush the residue on the workpiece surface and let it dry naturally.

[0044] Example 13

[0045] (1) Weigh the solid phase components according to mass ratio, including 65% Cr, 30% Ni, and 2% CeO 2 , 2% FeV 80 and 1% NH 4 Cl, placed it in a planetary ball mill with ethanol wet grinding at 400 rpm for 24 h, and then dried in vacuum at 100 °C for 24 h to obtain the cladding powder.

[0046] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0047] (3) The plasma cladding process parameters are: 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, shielding gas flow rate is 19L / min, and inert gas is Ar. After cladding, the residue on the surface of the workpiece is washed with a high-pressure water gun and naturally dried.

[0048] Embodiment 14

[0049] (1) Weigh the solid phase components according to mass ratio, including 70% Cr, 20% Ni, and 3% CeO 2 , 3% FeV 80 and 4% NH 4 Cl, placed it in a planetary ball mill with ethanol wet grinding at 400 rpm for 24 h, and then dried in vacuum at 100 °C for 24 h to obtain the cladding powder.

[0050] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0051] (3) 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, shielding gas flow rate is 19L / min, and inert gas is Ar. After cladding, the residue on the workpiece surface is washed with a high-pressure water gun and naturally air-dried.

[0052] Embodiment 15

[0053] (1) Weigh the solid components according to mass ratio, including 65% Cr, 25% Ni, and 4% CeO 2 , 4% FeV 80 and 2% NH 4 Cl, placed it in a planetary ball mill with ethanol wet grinding at 400 rpm for 24 h, and then dried in vacuum at 100 °C for 24 h to obtain the cladding powder.

[0054] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0055] (3) 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, shielding gas flow rate is 19L / min, and inert gas is Ar. After cladding, the residue on the workpiece surface is washed with a high-pressure water gun and naturally air-dried.

[0056] Example 16

[0057] (1) Weigh the solid phase components according to mass ratio, including 55% Cr, 35% Ni, and 3% CeO 2 , 3% FeV 80 and 4% NH 4 Cl, placed it in a planetary ball mill with ethanol wet grinding at 400 rpm for 24 h, and then dried in vacuum at 100 °C for 24 h to obtain the cladding powder.

[0058] (2) Use a high-pressure water gun to clean the workpiece surface for 5 minutes and then rinse it with alcohol or acetone.

[0059] (3) 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, shielding gas flow rate is 19L / min, and inert gas is Ar. After cladding, the residue on the workpiece surface is washed with a high-pressure water gun and naturally air-dried.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 13 is that the solid phase components in step (1) are replaced by: 65% Cr, 30% Ni, 4% CeO 2 and 1% NH 4 Cl.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 13 is that the solid phase components in step (1) are replaced by: 65% Cr, 30% Ni, 4% FeV 80 and 1% NH 4 Cl.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 13 is that the solid phase components in step (1) are replaced by: 65% Cr, 30% Ni, 4% TiO 2 and 1% NH 4 Cl.

[0066] Comparative Example 4

[0067] The difference between this comparative example and Example 13 is that the solid phase components in step (1) are replaced by: 65% Cr, 30% Ni, 2% CeO 2 , 2% FeV 80 and 1% NH 4 Br.

[0068] Comparative Example 5

[0069] The difference between this comparative example and Example 13 is that the solid phase components in step (1) are replaced by: 65% Cr, 30% Ni, 2% CeO 2 , 2% FeV 80 and 1% NH 4 I.

[0070] The performance of the materials prepared in Example 1, Examples 12 to 16 and Comparative Examples 1 to 6 was tested, and the test results are shown in Table 2.

[0071] Table 2

[0072]

[0073] From the above table, it can be seen that Example 13 has the best effect. From Comparative Examples 1, 2, and 3, it can be seen that CeO 2 and FeV 80 Each has a certain modification effect. Compared with Example 13, CeO 2 and FeV80 It has a synergistic modification effect. From Comparative Examples 4 and 5, it can be seen that NH 4 The Cl modifier has the most outstanding effect. In addition, the weight loss of TP347H parent material in the flue gas environment for 200 hours is 3.2mg / cm 3 Compared with the embodiment, the corrosion resistance of the present invention is up to 64 times higher than that of the parent material.

[0074] In summary, the present invention prepares a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of the boiler pipe. Under the conditions of adjusting the main process parameters such as the cladding powder composition and plasma cladding parameters, a chromium-nickel coating with a good metallurgical bond of 0.15 to 1.39 mm is prepared; the chromium-nickel coating obtained by the present invention has a corrosion resistance that is 20 to 64 times higher than that of the parent material in a 650°C flue gas corrosion environment, and a corrosion resistance that is 22 to 74 times higher than that of the parent material in a 750°C flue gas corrosion environment. This shows that the chromium-nickel coating prepared by the method of the present invention effectively improves the corrosion resistance of the alloy parent material in a flue gas corrosion environment.

[0075] The present invention prepares a chromium-nickel cladding coating suitable for the outer wall of the flue gas side of the boiler pipe, which is suitable for austenitic steel and high-temperature alloy components used in large boilers, oil and gas field transportation pipelines and other workpieces with large aspect ratios and various complex shapes. It has strong practicality, high permeation rate, excellent membrane-base bonding, and extremely good industrial mass production benefits.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the present invention.

Claims

1. A method for preparing a chromium-nickel cladding coating suitable for the outer wall of a boiler pipe on the flue gas side, characterized in that: include, Weigh and prepare each solid phase component according to the mass ratio, and prepare the solid phase cladding infiltrant after stirring, ball milling and drying for use; Clean the surface of the workpiece to be plated and pour enough cladding powder into the feeding port; Placing the workpiece in an inert atmosphere for plasma cladding, obtaining a chromium-nickel anti-oxidation coating after cooling, and performing cladding residue treatment; The solid phase components include Cr, Ni powder, NH4Cl activator, CeO2 modifier and FeV 80 .

2. The preparation method according to claim 1, characterized in that: The Cr and Ni powders were sieved through a 1000-mesh sieve.

3. The preparation method according to claim 2, characterized in that: The solid phase components are weighed by mass percentage and include 50-80% Cr, 10-40% Ni, 2-5% CeO2, 2-5% FeV 80 And 0-5% NH4Cl.

4. The preparation method according to claim 1, characterized in that: The wet grinding medium of the ball mill is anhydrous ethanol, the ball milling speed is 350-400 rpm, and the time is 12-24 hours.

5. The preparation method according to claim 1, characterized in that: The drying condition is vacuum drying at 80-120° C. for 12-24 hours.

6. The preparation method according to claim 1, characterized in that: The plasma cladding process parameters are: cladding current is 80-120A, feed rate is 18-22g / min, scanning rate is 20-40cm / min, nozzle height is 8-12mm, rotation speed is 2-5r / min, ion gas flow rate is 0.2-0.3L / min, shielding gas flow rate is 18-20L / min, and inert gas is Ar or N2.

7. The chromium-nickel cladding coating suitable for the outer wall of the flue gas side of a boiler pipe obtained by the preparation method according to any one of claims 1 to 6.

8. The chromium-nickel cladding coating according to claim 7, characterized in that: The chromium-nickel cladding coating is metallurgically bonded to the substrate, has a thickness of 0.1 to 2 mm, and a corrosion rate of less than 0.2 mg / cm2 in a 650°C flue gas environment for 200 hours. 3 .

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