CN111910226A - Crack-free Fe-Cr alloy coating and preparation method and application thereof - Google Patents

Crack-free Fe-Cr alloy coating and preparation method and application thereof Download PDF

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CN111910226A
CN111910226A CN202010682844.4A CN202010682844A CN111910226A CN 111910226 A CN111910226 A CN 111910226A CN 202010682844 A CN202010682844 A CN 202010682844A CN 111910226 A CN111910226 A CN 111910226A
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alloy coating
crack
free
temperature
alloy
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罗鹏
彭晓
田礼熙
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Nanchang Hangkong University
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    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/56—Electroplating: Baths therefor from solutions of alloys
    • C25D3/562—Electroplating: Baths therefor from solutions of alloys containing more than 50% by weight of iron or nickel or cobalt
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    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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    • C22C45/00—Amorphous alloys
    • C22C45/02—Amorphous alloys with iron as the major constituent
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23G—CLEANING OR DE-GREASING OF METALLIC MATERIAL BY CHEMICAL METHODS OTHER THAN ELECTROLYSIS
    • C23G1/00—Cleaning or pickling metallic material with solutions or molten salts
    • C23G1/14—Cleaning or pickling metallic material with solutions or molten salts with alkaline solutions
    • C23G1/19—Iron or steel
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    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D3/00—Electroplating: Baths therefor
    • C25D3/02—Electroplating: Baths therefor from solutions
    • C25D3/12—Electroplating: Baths therefor from solutions of nickel or cobalt
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/10—Electroplating with more than one layer of the same or of different metals
    • C25D5/12—Electroplating with more than one layer of the same or of different metals at least one layer being of nickel or chromium
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    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/34—Pretreatment of metallic surfaces to be electroplated
    • C25D5/36—Pretreatment of metallic surfaces to be electroplated of iron or steel

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Abstract

The invention provides a crack-free Fe-Cr alloy plating layer and a preparation method and application thereof, wherein in the Fe-Cr alloy plating layer, the content of Cr is 10-60% and the balance is Fe in percentage by mass. The preparation method comprises the steps of putting high-purity graphite into electroplating solution to serve as an anode, and putting a metal workpiece with poor corrosion resistance or no high-temperature oxidation resistance into the electroplating solution to serve as a cathode; the power supply is switched on, and the current density is controlled to be 5-15A/dm2The temperature of the electroplating solution is 20-30 ℃, the pH value is 2-3, the mechanical stirring speed is 200-350 r/min, and the electroplating time is 10-30 min. The Fe-Cr alloy coating prepared by the invention can be used for normal temperature protection of metal materials serving in corrosive liquid media or high temperature protection of hot end metal structure materials in a high temperature corrosion environment.

Description

Crack-free Fe-Cr alloy coating and preparation method and application thereof
Technical Field
The invention relates to the technical field of alloy electrodeposition, in particular to a crack-free Fe-Cr alloy coating and a preparation method and application thereof.
Background
Carbon steel and alloy steel are widely used as metal structural materials of petrochemical, power generation and energy pipeline transportation facilities due to good comprehensive mechanical properties and low price. However, due to the limitation of Cr content, these structural steels cannot form Cr-rich steel in room temperature corrosive medium2O3The corrosion-resistant passive film can not form continuous protective Cr under the high-temperature working environment of less than 900 DEG C2O3Oxide films, their surfaces often being coated with a high Cr protective coating to improve their corrosion resistance or high temperature oxidation resistance. So far, the preparation of a normal temperature corrosion resistant/high temperature oxidation resistant high-Cr Fe-Cr alloy coating on the surface of the steel by a simple electrodeposition technology has been reported, and the key points of the problem are as follows: the co-electrodeposition of a high Cr content Fe-Cr alloy coating is difficult to overcome the generation of cracks penetrating through the coating.
Disclosure of Invention
In order to solve the technical problems, the invention provides a crack-free Fe-Cr alloy coating in a first aspect, wherein the Fe-Cr alloy coating comprises 10-60% of Cr by mass, and the balance of Fe.
Wherein, when the Cr content is increased to more than 35%, the Fe-Cr alloy is transformed from a crystalline state to an amorphous state.
In a second aspect, the invention provides a crack-free Fe-Cr alloyThe preparation method of the gold plating layer comprises the steps of putting high-purity graphite into electroplating solution to serve as an anode, and putting a metal workpiece with poor corrosion resistance or poor high-temperature oxidation resistance into the electroplating solution to serve as a cathode; the power supply is switched on, and the current density is controlled to be 5-15A/dm2The temperature of the electroplating solution is 20-30 ℃, the pH value is 2-3, the mechanical stirring speed is 200-350 r/min, and the electroplating time is 10-30 min.
Wherein, the components and the concentration of the electroplating solution are as follows: 0.5 to 0.7 mol.L-1CrCl3，0.04~0.06 mol·L- 1FeCl2，1.5~2.5 mol·L-10.2 to 0.4 mol/L of urea-10.1 to 0.3 mol/L of sodium citrate-1Sodium formate, 0.5 to 2 mol. L-1NH4Cl，0.5~0.7 mol·L-1H3BO3，5~15 g·L-1NaF，5~15 g·L-1NaBr，3~6 g·L-1Ascorbic acid, 0.05-0.2 g.L-1Sodium lauryl sulfate.
The electroplating solution is characterized in that the basic formula of the electroplating solution is a chloride system, and the mass percentage concentration of NaCl in the chloride system is 3.0-4.0%.
The metal workpiece is pretreated before electroplating, and the specific process comprises the following steps: mechanical polishing → chemical degreasing → flowing water washing → deionized water washing → acid washing activation → deionized water washing → pre-nickel plating → deionized water washing.
The metal workpiece is chemically degreased by using alkaline wash, and the alkaline wash comprises the following components in concentration: 40-60 g/L NaOH, 30-40 g/L Na2CO3、35~60 g/LNa3PO4·12H2O 、10 ~20 g/L Na2SiO3The technological parameters are as follows: the temperature is 50-60 ℃, the pH value is 8, and the time is 10-15 min.
The metal workpiece is subjected to acid washing activation by hydrochloric acid, the concentration of the hydrochloric acid is 30-40 mL/L, and the acid washing time is 2-3 min.
The formula for pre-plating nickel on the metal workpiece is as follows: 200 g/L of nickel chloride, 10 mL/L of hydrochloric acid and 0.1 g/L of lauryl sodium sulfate, wherein the parameters of the electroplating process are 50-60 ℃, the pH value is 1.0-3.0, the temperature is 55-60 ℃, the time is 1-2 min,Jc=3~5 A·dm-2the thickness of the nickel preplating is 1 to 2 μm.
Wherein, the metal workpiece with the electroplated surface containing the Fe-Cr alloy coating is placed at the high temperature of 850 ℃, and continuous protective Cr is thermally grown on the surface of the Fe-Cr alloy coating2O3And (5) oxidizing the film.
The third aspect of the invention provides an application of a crack-free Fe-Cr alloy coating, and the Fe-Cr alloy coating can be used for normal-temperature protection of metal materials serving in corrosive liquid media or high-temperature protection of hot-end metal structural materials in a high-temperature corrosion environment.
The invention has the beneficial effects that:
the invention aims to break through the technical bottleneck of crack-free preparation of the high-Cr Fe-Cr alloy coating and realize that the coating has excellent normal-temperature corrosion resistance/high-temperature oxidation resistance. In addition, the Fe-Cr alloy coating is used as a high-temperature protective coating of steel, and the interdiffusion of Fe and an alloy steel matrix can be greatly reduced.
The Fe-Cr alloy coating and the preparation method thereof provided by the invention have the following advantages:
1. the plating layer has no microcrack. The invention obtains a plating solution formula with excellent electroplating effect by screening the composite coordination agent and the additive of the plating solution, and can obtain the Fe-Cr alloy plating layer without cracks and with the Cr content of 60mass percent.
2. The thickness and the content of the plating layer are controllable. Compared with the prior art, the method can accurately control the coating composition and the coating thickness in the Fe-Cr alloy electroplating, and can regulate and control the Cr content in the coating according to the Cr content required by different environments, thereby achieving the purposes of meeting the performance requirement and saving the cost.
3. Can greatly improve the corrosion resistance of the steel base material in a corrosive medium.
4. Can form Cr at high temperature (less than 850℃)2O3The protective oxide film greatly improves the high-temperature oxidation resistance of the steel matrix.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it should be obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a graph showing the relationship between the current density and the Cr content in a Fe-Cr alloy coating layer in a method according to an embodiment of the present invention;
FIG. 2 shows a method of producing a polymer having a current density of 7A dm-2Preparing a surface topography of the obtained Fe-Cr alloy coating;
FIG. 3 shows a method of the present invention in which the current density is 16A dm-2Preparing a surface topography of the obtained Fe-Cr alloy coating;
FIG. 4 shows a method of producing a sheet having a current density of 23A dm-2Preparing a surface topography of the obtained Fe-Cr alloy coating;
FIG. 5 is a surface topography map of a Fe-30Cr alloy coating deposited for 4 minutes in a method provided by an embodiment of the invention;
FIG. 6 is a surface topography map of a Fe-30Cr alloy coating deposited for 10 minutes in a method provided by an embodiment of the invention;
FIG. 7 is a surface topography map of a Fe-30Cr alloy coating deposited for 20 minutes in a method provided by an embodiment of the invention;
FIG. 8 is an SEM surface topography of a Fe-25Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 9 is an SEM surface morphology of a Fe-45Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 10 is a power spectrum of a Fe-25Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 11 is a power spectrum of a Fe-45Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 12 is a surface XRD pattern of a Fe-25Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 13 is a surface XRD pattern of a Fe-35Cr alloy coating prepared by the method provided by the embodiment of the invention;
FIG. 14 is a polarization curve diagram of a T91 steel substrate and a Fe-30Cr alloy coating prepared by the method provided by the embodiment of the invention in a NaCl solution with the mass concentration of 3.5%;
FIG. 15 is a graph showing the oxidation kinetics of a T91 steel substrate and a Fe-30Cr alloy coating prepared by the method of the present invention oxidized in air at 850 ℃ for 100 hours;
FIG. 16 is an SEM surface topography of a T91 steel substrate after high temperature oxidation at 850 ℃ for 20 h;
FIG. 17 is an SEM surface morphology of a Fe-30Cr alloy coating prepared by the method provided by the embodiment of the invention after being oxidized at 850 ℃ for 20 h;
FIG. 18 is a surface energy spectrum analysis of a T91 steel substrate after high temperature oxidation at 850 ℃ for 20 h;
FIG. 19 is a surface energy spectrum analysis chart of a Fe-30Cr alloy coating prepared by the method provided by the embodiment of the invention after being oxidized at a high temperature of 850 ℃ for 20 h;
FIG. 20 is a surface XRD analysis of a T91 steel substrate after high temperature oxidation at 850 ℃ for 20 h;
FIG. 21 is a surface XRD analysis diagram of a Fe-30Cr alloy coating prepared by the method provided by the embodiment of the invention after being oxidized at 850 ℃ for 20 h;
FIG. 22 is an SEM cross-sectional profile of a T91 steel substrate after high temperature oxidation at 850 ℃ for 20 h;
FIG. 23 is an SEM cross-sectional view of the Fe-30Cr alloy coating prepared by the method provided by the embodiment of the invention after being oxidized at 850 ℃ for 20 h.
Detailed Description
The following is a preferred embodiment of the present invention, and it should be noted that it is obvious to those skilled in the art that various modifications and improvements can be made without departing from the principle of the present invention, and these modifications and improvements are also considered to be within the scope of the present invention.
The invention provides a crack-free Fe-Cr alloy coating and a preparation method thereof, wherein the method comprises the following steps:
s1, processing the steel into small samples with the size of 15 multiplied by 10 multiplied by 2mm by using T91 steel as base metal, and firstly carrying out pretreatment, wherein the steps are as follows: mechanical polishing → chemical degreasing → flowing water washing → deionized water washing → acid washing activation → deionized water washing → preplating → deionized water washing;
the mechanical grinding is to grind the T91 steel processed into small samples to 1000# by using water sand paper;
the chemical degreasing is to place T91 steel in alkaline wash, wherein the alkaline wash comprises the following components in concentration: 50 g/L NaOH, 35 g/L Na2CO3、50 g/LNa3PO4·12H2O、15 g/L Na2SiO3The technological parameters are as follows: the temperature is 55 ℃, the pH value is 8, and the time is 15 min;
the acid pickling activation is to place the T91 steel in hydrochloric acid, wherein the concentration of the hydrochloric acid is 35 mL/L, and the acid pickling time is 2 min;
the preplating nickel is to place T91 steel in a preplating solution, wherein the preplating solution comprises the following components in concentration: 200 g/L of nickel chloride, 10 mL/L of hydrochloric acid and 0.1 g/L of lauryl sodium sulfate, wherein the parameters of the electroplating process are 50-60 ℃, the pH value is 1.0-3.0, the temperature is 55-60 ℃, the time is 1-2 min,Jc=3~5 A·dm-2the thickness of the nickel preplating is 1 to 2 μm.
S2, processing high-purity graphite into a size of 20 x 30 x 2mm, polishing the graphite to 1000# by using water sand paper, ultrasonically cleaning the graphite in alcohol, putting the graphite into electroplating solution to serve as an anode, and putting the T91 steel pretreated in the step S1 into the electroplating solution to serve as a cathode; the power supply is switched on, and the current density is controlled to be 10A/dm2Electroplating at 25 deg.C and pH 2 at a mechanical stirring speed of 300r/min for 20 min;
s3, placing the T91 steel with the surface containing the Fe-Cr alloy coating after being electroplated in the step S2 below 850 ℃, and thermally growing continuous protective Cr on the surface of the Ni-Cr alloy coating2O3And (5) oxidizing the film.
The components and concentrations of the plating solution used in this example were:
0.6 mol·L-1CrCl3，0.05 mol·L-1FeCl2，2 mol·L-10.3 mol/L of urea-1Sodium citrate, 0.2 mol. L-1Sodium formate, 1 mol. L-1NH4Cl，0.6 mol·L-1H3BO3，10 g·L-1NaF，10 g·L-1NaBr，5 g·L-1Ascorbic acid, 0.1 g.L-1Sodium lauryl sulfate.
The compositions of the examples of the present invention using T91 steel as the base material are shown in Table 1.
Figure DEST_PATH_IMAGE001
In order to verify the influence of the current density on the Cr content of the Fe-Cr alloy coating, the other process parameters are controlled to be unchanged by taking the above embodiment as reference, the Cr content of the coating is tested by adjusting the current density, FIG. 1 shows the influence relationship of the current density on the Cr content of the Fe-Cr alloy coating, and it can be seen from FIG. 1 that the Cr content of the coating gradually increases with the increase of the cathode current density. This is because the current density is increased, and not only Fe but also Fe can be increased2+And Cr3+The electrodeposition rate of the alloy can increase the cathode polarization and is beneficial to the more negative Cr of the standard electrode potential3+And discharging the cathode to increase the Cr content in the coating. But when the current density is higher than 19A dm-2In the meantime, the Cr content in the coating layer is rapidly reduced because the cathode side reaction evolves hydrogen violently, the pH rises sharply and the OH in the cathode region is too high under the condition of overhigh current density-Too high a concentration of Cr results in3+Hydroxyl bridge reaction to form Cr3+Against Cr3+The Cr content of the plating layer is suddenly reduced by the electrodeposition. Experiments show that when the current density is lower than 4A dm-2When the coating is used, rust spots appear rapidly in the air, indicating that the coating is easy to oxidize. When the current density is more than 19A dm-2In the meantime, the entire plating layer is whitish and the plating layer edge is liable to be blackened due to Fe2+And Cr3+Colloids or precipitates formed by the hydroxyl bridging reaction prevent the electrodeposition from scorching the coating. Therefore, under the research system, the cathode current density is controlled to be 5-15 A.dm-2Preferably, the current density can be regulated to obtain a plating layer with the target Cr content.
FIG. 2 shows a current density of 7A dm-2Preparing the obtained Fe-Cr alloy coatingFIG. 3 is a graph showing a current density of 16A dm-2The surface topography of the prepared Fe-Cr alloy coating is shown in FIG. 4, which is a graph of current density 23A dm-2The surface topography of the prepared Fe-Cr alloy coating can be seen from figures 2-4, and the cathode current density is 5-15 A.dm-2The plating layer is compact and has no microcrack. When the cathode current density is increased from low to high, the crystal grains of the coating are more refined, because the driving force of electric crystallization is increased along with the increase of the cathode current density, the crystal grain crystallization speed is higher than the crystal grain growth speed, so the crystal grains are refined, and the surface of the coating is more bright and smooth. However, when the cathode current density is too high, the side reaction in the cathode region causes hydrogen evolution to be severe, the local pH value rises sharply, and OH is-Too high a concentration of Cr results in3+Hydroxyl bridge reaction to form Cr3+Against Cr3+The Cr content of the plating layer is suddenly reduced by the electrodeposition, and the quality of the plating layer is also reduced by the violent hydrogen evolution reaction.
FIGS. 5, 6 and 7 are graphs showing the changes of the thickness of the Fe-30Cr (Cr content: 30%) alloy coating with respect to the plating time, and the present invention can control the thickness of the plated coating by controlling the electrodeposition time. FIG. 5 shows the deposition time of the plating layer is 4 minutes, the thickness of the Fe-Cr alloy plating layer is 4.445 μm, and the thickness of the nickel pre-plating layer is 655.7 nm; FIG. 6 shows that the deposition time of the plating layer is 10 minutes, the thickness of the Fe-Cr alloy plating layer is 10.27 μm, and the thickness of the pre-nickel plating layer is 732.1 nm; the deposition time of the plating layer of FIG. 7 was 20 minutes, the thickness of the Fe-Cr alloy plating layer was 17.99 μm, and the thickness of the nickel pre-plating layer was 655.7 nm.
FIG. 8 is an SEM surface topography of an Fe-25Cr (Cr content is 25%), FIG. 9 is an SEM surface topography of an Fe-45Cr (Cr content is 45%), FIG. 10 is an energy spectrum of the Fe-25Cr alloy plating, and FIG. 11 is an energy spectrum of the Fe-45Cr alloy plating, from which it can be seen that the electrodeposited Fe-Cr alloy plating under the complex complexing agent system has a flat microstructure, no microcracks, a small grain size and spherical nanocrystals. Along with the increase of the cathode current density, the crystal grains of the Fe-Cr alloy coating are refined, and the flatness is better.
FIG. 12 is a surface XRD pattern of an Fe-25Cr alloy plating layer, FIG. 13 is a surface XRD pattern of an Fe-35Cr alloy plating layer, a plating layer with an expected Cr content is obtained by adjusting the cathode current density and controlling an electrodeposition experiment, when the Cr content in the Fe-Cr alloy plating layer is 25% (mass fraction), an X-ray diffraction analysis pattern shows that a strong characteristic peak exists at a diffraction angle of 2 theta ≈ 45 degrees, and when the Cr content in the Fe-Cr alloy plating layer is 35% (mass fraction), the obtained X-ray diffraction pattern shows that a very wide 'steamed bread peak' for representing an amorphous structure is formed when the diffraction angle of 2 theta = 42-47 degrees, besides the diffraction peak of Fe-Cr, and the two peaks are in a superposition state. This is because, when the thickness of the Fe-Cr coating is not large (20 μm or less), the texture of the substrate and the texture of the coating are reflected by X-ray. At this time, the diffraction peak of the matrix Fe-9Cr and the diffraction peak of the Fe-35Cr plating layer were superimposed. The X-ray diffraction pattern shows that the Fe-Cr alloy coating prepared by electrodeposition in the experiment has different coating structures under the condition of different Cr contents, and the structure is mainly represented by that the crystalline coating with low Cr content is changed into the amorphous coating with high Cr content.
The following comparison verifies the experimental comparison results of the corrosion resistance and the high-temperature oxidation resistance of the T91 steel substrate and the crack-free Fe-Cr alloy coating deposited on the surface of the T91 steel substrate.
FIG. 14 is a polarization diagram of a T91 steel substrate and a Fe-30Cr (30% Cr content) alloy coating in NaCl solution with a mass concentration of 3.5%, the self-corrosion current decreased significantly after electrodeposition of the Fe-30Cr coating, and the corrosion rate decreased to one third of that of the T91 substrate as calculated by fitting, since the Fe-30Cr coating formed a Cr-rich coating with good corrosion resistance in NaCl solution2O3The passivation film of (1).
FIG. 15 is an oxidation kinetics curve of T91 steel substrate and Fe-30Cr alloy coating oxidized for 100h in air at 850 ℃, and the oxidation kinetics curves of T91 sample and T91 sample of electrodeposited Fe-Cr alloy are in a parabola trend and accord with the law of parabola. Two groups of experiments show that the oxidation weight gain of the sample plated with the Fe-Cr alloy is obviously reduced, and the weight gain of the T91 sample is 26.89 mg cm after constant-temperature oxidation for 20 hours-2While the weight of the sample plated with the Fe-Cr alloy is increased by only 2.51 mg cm-2. After constant temperature oxidation for 100h, the weight of the T91 sample is increased by 50.12 mg cm-2While the weight of the sample plated with the Fe-Cr alloy is increased by only 5.02 mg cm-2The weight gain reduction is about one order of magnitude. The Fe-Cr alloy coating is shown to have obvious inhibition effect on oxidation in the air atmosphere environment.
FIG. 16 is an SEM surface topography of a T91 steel substrate after being oxidized for 20h at 850 ℃, and FIG. 17 is an SEM surface topography of an Fe-30Cr alloy coating after being oxidized for 20h at 850 ℃; FIG. 18 is a surface energy spectrum analysis chart of a T91 steel substrate after being oxidized for 20h at 850 ℃, and FIG. 19 is a surface energy spectrum analysis chart of an Fe-30Cr alloy coating after being oxidized for 20h at 850 ℃; FIG. 20 is a surface XRD analysis pattern of a T91 steel substrate after being subjected to high-temperature oxidation at 850 ℃ for 20h, and FIG. 21 is a surface XRD analysis pattern of an Fe-30Cr alloy coating after being subjected to high-temperature oxidation at 850 ℃ for 20 h; as can be seen from the figure, the surface morphology of the T91 sample plated with Fe-Cr alloy is obviously different from that of the T91 sample, the former is more fine and flaky in appearance, and the latter is mainly granular and can be observed to have obvious large-particle inclusion. The surface structure of the T91 sample electroplated with the Fe-Cr alloy after being oxidized is Cr2O3The texture of the oxidized surface of the T91 sample is Fe2O3. And after the oxidized sample is subjected to chemical Ni plating protection on the surface oxide layer, further grinding and polishing the section and observing and analyzing under scanning SEM.
FIG. 22 is an SEM sectional morphology of a T91 steel substrate after being oxidized for 20h at 850 ℃, FIG. 23 is an SEM sectional morphology of an Fe-30Cr alloy coating after being oxidized for 20h at 850 ℃, and the thickness of an oxide film of the T91 steel after being oxidized for 20h at 850 ℃ is about 220 μm. The oxidation section of the T91 material of the electro-deposition Fe-Cr alloy coating is greatly reduced compared with the oxidation section thickness of T91, the thickness of the oxidation film after being oxidized for 20 hours at the constant temperature of 850 ℃ is about 20 mu m, and as can be seen from the figure, a layer of Fe-Cr alloy coating is arranged between the substrate and the oxidation film, which shows that the Fe-Cr coating is not completely oxidized after being oxidized for 20 hours. The ratio of the thickness of the oxide film of T91 to that of T91 of the electroplated Fe-Cr alloy was about 10: 1, which is similar to the weight gain ratio obtained from the oxidation kinetics curve, and the weight gain ratio of the two samples was about 10: 1 after constant temperature oxidation at 850 ℃ for 20 h.
As is apparent from the above description, the present invention can provide a Fe-Cr alloy plating layer having a controlled thickness and Cr content, no microcracks, and excellent high-temperature oxidation resistance. Electroplating Fe-Cr alloy can effectively improveThe high temperature oxidation resistance of the liter T91 steel, and the oxidation weight gain of the T91 steel electroplated with the Fe-Cr alloy can be reduced by about one order of magnitude under the condition of high temperature oxidation at 850 ℃ for 100 hours in air. The chromium oxide film is formed by oxidizing the Fe-Cr alloy electroplated T91 steel at 850 ℃ for 100h in air, and the structure of the chromium oxide film is mainly divided into an outer layer of Cr2O3Inner layer of FeO + Cr2O3。
The Fe-Cr alloy coating can be used for normal temperature protection of metal materials (such as pipeline steel and the like) serving in corrosive liquid media, and can also be used for high temperature protection of metal materials (such as power plant boiler tubes) serving in high temperature corrosion environments and the like.
The above examples only express the specific embodiments of the present invention, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the present invention. It should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the spirit of the present invention, and these changes and modifications are all within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims (10)

1. A crack-free Fe-Cr alloy coating is characterized in that: in the Fe-Cr alloy coating, the content of Fe and Cr is 10-60% by mass, and the balance is Fe.
2. A preparation method of a crack-free Fe-Cr alloy coating is characterized by comprising the following steps: putting high-purity graphite into electroplating solution to be used as an anode, and putting a metal workpiece with poor corrosion resistance or poor high-temperature oxidation resistance into the electroplating solution to be used as a cathode; the power supply is switched on, and the current density is controlled to be 5-15A/dm2The temperature of the electroplating solution is 20-30 ℃, the pH value is 2-3, the mechanical stirring speed is 200-350 r/min, and the electroplating time is 10-30 min.
3. The method of claim 2, wherein the plating solution comprises the following components in concentration: 0.5 to 0.7 mol.L-1CrCl3，0.04~0.06 mol·L-1FeCl2，1.5~2.5 mol·L-10.2 to 0.4 mol/L of urea-10.1 to 0.3 mol/L of sodium citrate-1Sodium formate, 0.5 to 2 mol. L-1NH4Cl，0.5~0.7 mol·L-1H3BO3，5~15 g·L-1NaF，5~15 g·L-1NaBr，3~6 g·L-1Ascorbic acid, 0.05-0.2 g.L-1Sodium lauryl sulfate.
4. The method for preparing a crack-free Fe-Cr alloy coating according to claim 3, wherein: the electroplating solution is characterized in that the basic formula of the electroplating solution is a chloride system, and the mass percentage concentration of NaCl in the chloride system is 3.0-4.0%.
5. The method for preparing a crack-free Fe-Cr alloy coating according to claim 2, wherein: the metal workpiece is pretreated before electroplating, and the specific process comprises the following steps: mechanical polishing → chemical degreasing → flowing water washing → deionized water washing → acid washing activation → deionized water washing → pre-nickel plating → deionized water washing.
6. The method for preparing a crack-free Fe-Cr alloy coating according to claim 5, wherein: and chemically removing oil from the metal workpiece by using alkaline wash, wherein the alkaline wash comprises the following components in concentration: 40-60 g/L NaOH, 30-40 g/L Na2CO3、35~60 g/LNa3PO4·12H2O 、10 ~20 g/L Na2SiO3The technological parameters are as follows: the temperature is 50-60 ℃, the pH value is 8, and the time is 10-15 min.
7. The method for preparing a crack-free Fe-Cr alloy coating according to claim 5, wherein: and (3) carrying out acid washing activation on the metal workpiece by using hydrochloric acid, wherein the concentration of the hydrochloric acid is 30-40 mL/L, and the acid washing time is 2-3 min.
8. The method of claim 5, wherein the Fe-Cr alloy coating is formed without cracks: the formula for pre-plating nickel on the metal workpiece is as follows: 200 g/L of nickel chloride, 10 mL/L of hydrochloric acid and 0.1 g/L of lauryl sodium sulfate, wherein the parameters of the electroplating process are 50-60 ℃, the pH value is 1.0-3.0, the temperature is 55-60 ℃, the time is 1-2 min,Jc=3~5 A·dm-2the thickness of the nickel preplating is 1 to 2 μm.
9. The method for producing a crack-free Fe-Cr alloy coating according to any one of claims 2 to 8, wherein: placing the metal workpiece with the electroplated surface containing the Fe-Cr alloy coating at the high temperature of 850 ℃, and thermally growing continuous protective Cr on the surface of the Fe-Cr alloy coating2O3And (5) oxidizing the film.
10. The application of the crack-free Fe-Cr alloy coating is characterized in that: the Fe-Cr alloy coating can be used for normal-temperature protection of metal materials serving in corrosive liquid media or high-temperature protection of hot-end metal structural materials in a high-temperature corrosion environment.
CN202010682844.4A 2020-07-15 2020-07-15 Crack-free Fe-Cr alloy coating and preparation method and application thereof Pending CN111910226A (en)

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