Chromium coating based on V2O5 modification and preparation method thereof

Abstract

The invention discloses a chromium coating based on V2O5 modification and a preparation method thereof. A used solid phase permeating agent comprises the following components: 30 to 50 percent of Cr, 2 to 7 percent of V2O5, 30 to 50 percent of SiC, 1 to 5 percent of NH4Cl, 5 to 5 percent of La2O3 and 2 to 5 percent of Y2O3. The prepared chromium coating is uniform in organization structure, moderate in thickness, sufficient in Cr atom diffusion, good in metallurgical bonding with a base body, 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 conveying pipelines, and excellent in industrial batch production benefit.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface alloying and coating preparation, and specifically relates to a chromium coating based on V2O5 modification and a preparation method thereof. Background Art

[0002] The high-temperature corrosion on the flue gas side of the boiler tubes in thermal power plants has become a major hidden danger to the safe operation of the power station. The corrosion of the metal on the heating surface on the flue gas side is mainly caused by a series of chemical reactions between the material surface and the surrounding corrosive media, such as SO2 in the flue gas formed after the combustion of coal powder, boiler feed water, boiler water, steam, air and fly ash / waste residue, resulting in metal corrosion damage. At present, the problem of corrosion on the flue gas side of boiler pipes is mostly solved by depositing chromium high-temperature coating on the surface of austenitic steel pipes.

[0003] Existing high-temperature coating technology is mostly used for hot-end parts such as aircraft engine blades, rotors, and turbine disks with high temperature, short action time, and small size. For the characteristics of large aspect ratio structure, high temperature, long time, and low stress service environment of energy equipment flow parts, the existing coating technology is no longer applicable; on the other hand, the stability of Cr2O3 in steam above 600℃ is poor, and the loose oxide film caused by volatile products will cause the oxide film to peel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 supplemented, the corrosion resistance of the alloy will also drop sharply. Therefore, it is of great practical significance to study and develop high-performance corrosion-resistant coatings and their preparation processes 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, another object of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a chromium coating based on V2O5 modification.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0008] The solid phase component is ball-milled to obtain solid phase infiltration agent powder;

[0009] The workpiece to be infiltrated and the solid phase infiltrant powder are subjected to vacuum high temperature heat treatment, and taken out after cooling to obtain a workpiece containing a chromium coating;

[0010] The solid phase components include, by mass percentage, 30-60% Cr powder, 2-7% V2O5, 30-50% SiC, 1-5% NH4Cl, 0-5% La2O3, and 2-5% Y2O3;

[0011] The Cr powder was sieved through a 1000-mesh sieve.

[0012] As a preferred solution of the method for modifying a workpiece with a solid phase infiltration agent described in the present invention, the mass percentage of the Cr powder is 40-60%.

[0013] As a preferred solution of the method for modifying a workpiece with a solid phase infiltration agent described in the present invention, the rotation speed of the ball mill is 350-400 rpm.

[0014] As a preferred solution of the method for modifying a workpiece with a solid phase infiltration agent described in the present invention, the ball milling time is 12 to 24 hours.

[0015] As a preferred solution of the method for modifying a workpiece with a solid phase penetrant according to the present invention, the workpiece to be infiltrated is placed in the middle of the solid phase penetrant powder, and the distance between adjacent workpieces to be infiltrated is not less than 10 cm.

[0016] As a preferred solution of the method for modifying a workpiece with a solid phase infiltration agent described in the present invention, the temperature of the vacuum high-temperature heat treatment is 1000-1150°C.

[0017] As a preferred solution of the method for modifying a workpiece with a solid phase infiltration agent described in the present invention, the holding time of the vacuum high-temperature heat treatment is 1 to 5 hours.

[0018] As a preferred solution of the workpiece containing chromium coating obtained by the modification method of the present invention, the vacuum degree of the vacuum high temperature heat treatment is 1×10 -3 ~9×10 -3 Pa.

[0019] Another object of the present invention is to overcome the deficiencies in the prior art and provide a chromium coating prepared by the preparation method of the chromium coating modified by V2O5, wherein: the thickness of the chromium coating is 8.6 to 40.2 μm, and the Cr atomic content is 22.2% to 35.4%.

[0020] As a preferred embodiment of the chromium coating described in the present invention, the chromium coating improves the heat corrosion resistance of the workpiece in a flue gas environment. After 500 hours in a 650°C flue gas corrosion environment, the weight loss of the workpiece containing the chromium coating is only 2% to 4.16% of the workpiece to be infiltrated. After 500 hours in a 750°C flue gas corrosion environment, the weight loss of the workpiece containing the chromium coating is only 2.13% to 3.81% of the workpiece to be infiltrated.

[0021] Beneficial effects of the present invention:

[0022] (1) The present invention adds rare earth oxides to the solid phase infiltration agent component, which has the effect of promoting infiltration and activation, thereby improving the infiltration rate and coating quality. In addition, the rare earth oxides can strengthen the matrix structure and enhance the surface hardness on the basis of promoting infiltration.

[0023] (2) The addition of V2O5 in the present invention can enhance the corrosion resistance and thermal strength of the base material. The V element can bind free carbon atoms, inhibit the formation of network chromium carbides, and enhance the compactness and oxidation resistance of the Cr coating. The addition of V2O5 can pin the grain boundaries, strengthen 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.

[0024] (3) The present invention increases the vapor pressure of the halide and reduces the influence of other residual gases on the diffusion layer by carrying out embedding diffusion in a vacuum environment.

[0025] (4) The infiltration agent components used in the present invention do not contain any toxic, harmful or polluting components, and the remaining infiltration agent powder after embedding can be recovered and reused multiple times. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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:

[0027] Figure 1 This is a cross-sectional morphology diagram of the V2O5-modified chromium coating in Example 1 of the present invention.

[0028] Figure 2 This is a cross-sectional morphology diagram of the chromium coating in Example 10 of the present invention.

[0029] Figure 3 This is a cross-sectional morphology diagram of the chromium coating in Comparative Example 1 of the present invention.

[0030] Figure 4 This is a cross-sectional morphology diagram of the chromium coating in Comparative Example 2 of the present invention.

[0031] Figure 5 This is a cross-sectional morphology diagram of the chromium coating in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0032] 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.

[0033] 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.

[0034] 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.

[0035] The workpiece material to be infiltrated in the present invention is generally a heating surface steel pipe of a power station boiler, such as Super304H, TP347H, TP347HFG and other grades of steel pipes.

[0036] The method for measuring the thickness of the chromium coating in the present invention is: taking a cross section of a chromium coating sample, and measuring the coating thickness according to the coating appearance and a corresponding scale under a scanning electron microscope (SEM).

[0037] The method for determining the Cr atomic content in the chromium coating of the present invention is as follows: taking a cross section of the chromium coating sample, and determining the Cr content at the corresponding position of the coating using energy dispersive spectrum analysis (EDS) under a scanning electron microscope (SEM).

[0038] The method for determining the corrosion resistance of the material under high temperature conditions in the present invention is: placing the material sample in a boiler flue gas simulation environment (gas containing CO2, SO2, CO, H2O, etc., temperature 650°C) for a corrosion resistance test for 500 hours.

[0039] The quantitative index of the corrosion resistance of the material of the present invention is the corrosion weight gain of the sample per unit area, and the calculation method is: corrosion weight gain = (sample weight at target corrosion time - original sample weight) / sample surface area.

[0040] Example 1

[0041] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0042] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0043] Weigh the solid phase components according to mass proportion, including 30% Cr, 7% V2O5, 50% SiC, 5% NH4Cl, 4% La2O3 and 4% Y2O3, wherein Cr powder is the infiltration source, V2O5 is the modifier, SiC is the filler, NH4Cl is the activator, La2O3 and Y2O3 are the infiltration catalysts, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0044] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1000 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0045] Example 2

[0046] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0047] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 10s, and then rinse with deionized water and alcohol in turn and dry;

[0048] Weigh solid phase components according to mass ratio, including 50% Cr, 7% V2O5, 30% SiC, 5% NH4Cl, 4% La2O3 and 4% Y2O3, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0049] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1000 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0050] Example 3

[0051] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0052] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0053] Solid phase components, including 40% Cr, 7% V2O5, 43% SiC, 5% NH4Cl and 5% La2O3, were weighed according to mass ratio, and ball-milled in a planetary ball mill at 400 rpm for 24 h to obtain a solid phase infiltration agent;

[0054] Place the workpiece to be infiltrated and the penetrant in the embedding tank, with the workpiece in the middle of the penetrant powder, and the distance between adjacent workpieces should not be less than 10 cm; -3 Pa vacuum degree, the heat treatment temperature is 1000 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0055] Example 4

[0056] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0057] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0058] Solid phase components, including 40% Cr, 7% V2O5, 43% SiC, 5% NH4Cl and 5% Y2O3, were weighed according to mass ratio, and ball-milled in a planetary ball mill at 350 rpm for 20 h to obtain a solid phase infiltration agent;

[0059] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1000 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0060] Example 5

[0061] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0062] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0063] Weigh solid phase components according to mass ratio, including 40% Cr, 2% V2O5, 45% SiC, 5% NH4Cl, 4% La2O3 and 4% Y2O3, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0064] Place the workpiece to be infiltrated and the infiltrant together in the embedding infiltration tank, with the workpiece to be infiltrated placed in the middle of the infiltrant powder, with the distance between adjacent workpieces not less than 10 cm; -3 Pa vacuum degree, the heat treatment temperature is 1050 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0065] Example 6

[0066] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0067] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 5 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0068] Weigh solid phase components according to mass ratio, including 40% Cr, 4% V2O5, 45% SiC, 1% NH4Cl, 5% La2O3 and 5% Y2O3, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0069] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1100 ℃, the insulation time is 5h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0070] Example 7

[0071] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0072] Take out the workpiece to be infiltrated, use a high-pressure water gun to rinse for 10 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 20s. After completion, rinse with deionized water and alcohol in turn and dry;

[0073] Weigh solid phase components according to mass ratio, including 40% Cr, 7% V2O5, 42% SiC, 5% NH4Cl, 2% La2O3 and 4% Y2O3, place them in a planetary ball mill at 400 rpm for 18 hours to obtain a solid phase infiltration agent;

[0074] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1150 ℃, the insulation time is 2h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0075] Example 8

[0076] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0077] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0078] Weigh solid phase components according to mass ratio, including 40% Cr, 7% V2O5, 42% SiC, 5% NH4Cl, 4% La2O3 and 2% Y2O3, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0079] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1150 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0080] Example 9

[0081] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0082] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0083] Solid phase components, including 35% Cr, 5% V2O5, 50% SiC, 5% NH4Cl, 2% La2O3 and 3% Y2O3, were weighed according to mass ratio, and ball-milled in a planetary ball mill at 350 rpm for 24 h to obtain a solid phase infiltration agent;

[0084] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1050 ℃, the insulation time is 5h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0085] Example 10

[0086] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0087] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0088] Solid phase components, including 45% Cr, 5% V2O5, 40% SiC, 5% NH4Cl, 3% La2O3 and 2% Y2O3, were weighed according to mass ratio, and ball-milled in a planetary ball mill at 350 rpm for 24 h to obtain a solid phase infiltration agent;

[0089] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1150℃, the heat treatment time is 4h, and after the heat treatment is completed, it is cooled to room temperature to obtain a workpiece containing a chromium coating. Figure 3 shown.

[0090] Embodiment 11

[0091] This embodiment provides a chromium coating based on V2O5 modification and a preparation method thereof.

[0092] Take out the workpiece to be infiltrated, use high-pressure air flow to wash for 15 minutes to remove oil stains, dust, etc. on the workpiece surface and remove the oxide skin. After cleaning, use metallographic sandpaper to grind the workpiece surface to a roughness Ra less than 0.8μm, then use 0.5% hydrochloric acid and hydrofluoric acid to clean the workpiece surface for 30s, and then rinse with deionized water and alcohol in turn and dry;

[0093] Weigh solid phase components according to mass ratio, including 60% Cr, 7% V2O5, 50% SiC, 5% NH4Cl, 4% La2O3 and 4% Y2O3, place them in a planetary ball mill at 400 rpm for 24 hours to obtain a solid phase infiltration agent;

[0094] Place the workpiece to be infiltrated and the penetrant in the embedding infiltration tank. The workpiece to be infiltrated is placed in the middle of the penetrant powder. The distance between adjacent workpieces should not be less than 10 cm. -3 Pa vacuum degree, the heat treatment temperature is 1000 ℃, the insulation time is 4h, and after the insulation is completed, it is cooled to room temperature to obtain a workpiece containing chromium coating.

[0095] The thickness of the chromium coatings, Cr atomic content and corrosion resistance of the materials prepared in Comparative Examples 1-11 are shown in Table 1.

[0096] Table 1 Comparison of the thickness, Cr atomic content and corrosion resistance of the chromium coating in Examples 1-11

[0097]

[0098]

[0099] The corrosion resistance of the base material (workpiece to be infiltrated) in a 650℃ flue gas corrosion environment is 15mg / cm2 in 500h. 2 In the 750℃ flue gas corrosion environment, the corrosion resistance is 500h and the weight loss is 18mg / cm 2 .

[0100] The thicker the chromium coating, the higher the chromium content, and the better the quality of the dense chromium oxide formed on the surface, the higher the corrosion resistance is. The thickness of the chromium coating in the workpiece containing the chromium coating is 8.6-40.2μm, the Cr atomic content is 22.2%-35.4%, and it is well bonded with the parent material; after 500h in a 650℃ flue gas corrosion environment, the weight loss is only 2%-4.16% of the parent material, and after 500h in a 750℃ flue gas corrosion environment, the weight loss is only 2.13%-3.81% of the parent material.

[0101] Comparative Example 1

[0102] The difference between this comparative example and Example 10 is that the solid phase infiltration agent component does not contain La2O3 and Y2O3, and the other steps are the same as those in Example 10 to prepare a chromium coating.

[0103] The cross-sectional microstructure Figure 3 As shown, the thickness of the chromized layer is uneven and discontinuous, and the quality is quite different from that of the chromized layer in Example 10, which shows that the two catalysts La2O3 and Y2O3 play a key role in promoting the formation of chromium coating on the surface of the workpiece to be chromized.

[0104] Comparative Example 2

[0105] The difference between this comparative example and Example 1 is that the solid phase infiltration agent does not contain V2O5, and other operations are the same as those in Example 1 to obtain a workpiece containing a chromium coating.

[0106] This comparative example does not contain V2O5, and the cross-sectional microstructure is as follows Figure 4 As shown, the thickness of the chromized layer is uneven and discontinuous, and the quality is quite different from that of the chromized layer in Example 1, which shows that the two chromized agents V2O5 play a key role in promoting the formation of chromium coating on the surface of the workpiece to be chromized.

[0107] Comparative Example 3

[0108] The difference between this comparative example and Example 1 is that the solid phase infiltration agent component contains only Cr powder, and other operations are the same as those in Example 1 to obtain a workpiece containing a chromium coating.

[0109] The solid phase infiltration agent component of this comparative example only contains Cr powder, and the cross-sectional microstructure is as follows Figure 5 As shown in the figure, Cr did not penetrate into the matrix material, only partially melted and adhered to the surface of the matrix, and no effective penetration layer was produced, indicating that other solid phase penetration agents play a specific key role in the formation of the penetration layer.

[0110] Comparative Example 4

[0111] The difference between this comparative example and Example 1 is that the solid phase infiltration agent component does not contain filler SiC, and other operations are the same as Example 1.

[0112] The infiltration layer obtained in this comparative example is discontinuous, uneven, and has a morphology similar to Figure 3 Similarly, it can be seen that the mixture of filler SiC and Cr can make Cr evenly dispersed, and when the mixed solid phase is attached to the surface of the substrate, Cr maintains an appropriate concentration, indicating that SiC filler plays a key role in the formation of chromium coating.

[0113] Comparative Example 5

[0114] The difference between this comparative example and Example 1 is that the solid phase infiltration agent component does not contain NH4Cl, and other operations are the same as those in Example 1 to obtain a workpiece containing a chromium coating.

[0115] This comparative example does not contain NH4Cl, and the obtained coating is thinner, about 10% of that in Example 1. It can be seen that during the sintering process, the infiltration-aiding effect produced by the decomposition of NH4Cl is more obvious, and plays a key role in promoting the formation of chromium coating on the surface of the workpiece to be infiltrated.

[0116] In summary, the present invention prepares a chromium coating with good metallurgical bonding having a thickness of 8.6 to 40.2 μm and a Cr atomic content of 22.2% to 35.4% under the conditions of adjusting main process parameters such as the content of the penetrant component, the added content of the rare earth oxide and the heat treatment parameters. The chromium coating effectively improves the heat corrosion resistance of the alloy base material in a flue gas environment.

[0117] 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 may 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 claims of the present invention.

Claims

1. A method for preparing a chromium coating based on V2O5 modification, characterized in that: include, The solid phase component is ball-milled to obtain solid phase infiltration agent powder; The workpiece to be infiltrated and the solid phase infiltrant powder are subjected to vacuum high temperature heat treatment, and taken out after cooling to obtain a workpiece containing a chromium coating; The solid phase components include, by mass percentage, 30-60% Cr powder, 2-7% V2O5, 30-50% SiC, 1-5% NH4Cl, 0-5% La2O3, and 2-5% Y2O3.

2. The method for preparing a chromium coating based on V2O5 modification according to claim 1, characterized in that: The mass percentage of the Cr powder is 40-60%.

3. The method for preparing a chromium coating based on V2O5 modification according to claim 1, characterized in that: The rotation speed of the ball mill is 350-400 rpm.

4. The method for preparing a chromium coating based on V2O5 modification according to claim 3, characterized in that: The ball milling time is 12 to 24 hours.

5. The method for preparing a chromium coating based on V2O5 modification according to claim 1, characterized in that: The workpiece to be infiltrated is placed in the middle of the solid phase infiltrant powder, and the distance between adjacent workpieces to be infiltrated is not less than 10 cm.

6. The method for preparing a chromium coating based on V2O5 modification according to claim 1, characterized in that: The temperature of the vacuum high temperature heat treatment is 1000-1150°C.

7. The method for preparing a chromium coating based on V2O5 modification according to claim 6, characterized in that: The heat preservation time of the vacuum high temperature heat treatment is 1 to 5 hours.

8. The method for preparing a chromium coating based on V2O5 modification according to claim 7, characterized in that: The vacuum degree of the vacuum high temperature heat treatment is 1×10 -3 ~9×10 -3 Pa.

9. The chromium coating prepared by the method for preparing a chromium coating modified by V2O5 according to any one of claims 1 to 8, characterized in that: The thickness of the chromium coating is 8.6-40.2 μm, and the Cr atomic content is 22.2%-35.4%.

10. The chromium coating according to claim 9, characterized in that: The chromium coating improves the heat corrosion resistance of the workpiece in a flue gas environment. After 500 hours in a 650°C flue gas corrosion environment, the weight loss of the workpiece containing the chromium coating is only 2% to 4.16% of the workpiece to be infiltrated. After 500 hours in a 750°C flue gas corrosion environment, the weight loss of the workpiece containing the chromium coating is only 2.13% to 3.81% of the workpiece to be infiltrated.

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