Steel surface enhancement method based on high-power ultrasonic-assisted plasma electrolytic oxidation and application of steel surface enhancement method

Abstract

The invention provides a steel surface enhancement method based on high-power ultrasonic-assisted plasma electrolytic oxidation and application of the steel surface enhancement method. The method specifically comprises the following steps: performing micro-arc oxidation by taking a meta-aluminate, phosphate or silicate solution system as an electrolyte, taking filamentous or columnar steel as a micro-arc oxidation anode and taking an annular inert electrode as a micro-arc oxidation cathode. And during micro-arc oxidation, the electrolyte is subjected to uniform high-power ultrasonic treatment, so that a ceramic film layer with high bonding strength and layering characteristics can be generated on the surface of the anode in situ. The overall thickness of the prepared ceramic film layer does not exceed 20 microns, and an inner layer in contact with a substrate is compact, so that the corrosion resistance is provided; the outer layer has a layering defect, and when the external stress is too large, the layering defect promotes the ceramic film layer to gradually fall off so as to prolong the fatigue life of the film layer. Therefore, the method can be used as a surface treatment method for the steel wire and the rigging thereof for ocean engineering, and the marine environment adaptability of the filiform or columnar steel is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of material surface treatment, and specifically relates to a steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation and an application thereof. Background Art

[0002] Special steel cables are spiral steel wire bundles made by twisting a large number of steel wires together according to certain rules. They are composed of steel wires, rope cores and lubricating grease. They are often accompanied by repeated action of external loads, so they have extremely high requirements for the fatigue performance of the filamentary or cylindrical steel involved. At the same time, with the extensive application of special steel cables in marine engineering, their special service environment requires the steel wire ropes to be in contact with seawater or marine atmospheric environment for a long time. Therefore, it is necessary to ensure that the steel wire has excellent seawater corrosion resistance to ensure that the rigging can operate stably and for a long time in the marine environment without being damaged.

[0003] Plasma electrolytic oxidation is a common surface enhancement method for valve metals (such as Al, Ti, Mg, etc.). It uses a combination of electrolyte and corresponding electrical parameters to grow a ceramic film layer mainly composed of matrix metal oxide on the surface of valve metal and its alloys by relying on the instantaneous high temperature and high pressure generated by plasma discharge. The obtained ceramic film layer has high chemical stability and can be used as a physical barrier to prevent the contact between the external corrosive medium and the substrate, so it has excellent corrosion resistance; at the same time, the ceramic film layer itself also has excellent wear resistance, high temperature impact resistance and electrical insulation, which helps to extend the life of the treated parts. However, the ceramic film layer obtained by plasma electrolytic oxidation is generally a porous structure and because its process involves transient high temperature and high pressure, there are often a large number of micro defects in the film layer (such as the formation of thermal cracks). These defects will significantly affect the fatigue performance of the steel wire and seriously reduce its fatigue life, especially the strain-controlled low-cycle fatigue life.

[0004] Therefore, in response to the common problems of ceramic films obtained by existing plasma electrolytic oxidation, how to reduce the negative impact on fatigue life while ensuring the corrosion resistance of the obtained ceramic film layer through process design, and then apply the plasma electrolytic oxidation process to the field of special marine engineering steel cables, is an important issue that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation, which solves the technical problem in the prior art that plasma electrolytic oxidation treatment has a negative impact on the fatigue life of filamentary or columnar steel.

[0006] Specifically, the method provided by the present invention ensures the uniformity of plasma discharge by adding uniform ultrasonic assistance and designing an annular inert counter electrode; with the help of high-power ultrasonic action, the thickness of the obtained ceramic film layer is reduced, and on the basis of obtaining a dense ceramic film inner layer, stratification defects are successfully introduced into the ceramic film outer layer.

[0007] Among them, the dense inner layer of the ceramic film will effectively isolate the external corrosive environment and improve the corrosion resistance of the filamentary or columnar steel; the reduction of the film thickness will help improve the fatigue life, and when the external stress is too large and causes the initiation and growth of fatigue cracks inside the film, the delamination defects will cause the ceramic film to gradually fall off to delay the appearance of fatigue cracks, thereby improving its fatigue life. Therefore, the film with this feature will reduce its negative impact on fatigue life while improving the corrosion resistance of filamentary or columnar steel, thereby solving the problems of the existing technology.

[0008] To achieve the above-mentioned purpose, the present invention provides a steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation, which specifically includes: using a filamentous or columnar steel as an anode and a ring-shaped inert electrode as a cathode to improve the uniformity of the electric field during micro-arc oxidation, so that the obtained ceramic film layer grows uniformly; at the same time, high-power ultrasound treatment is performed during the micro-arc oxidation process to generate a large number of pores and strong shock waves, induce layered defects in the obtained ceramic film layer, destroy non-tightly deposited oxides, reduce the thickness of the ceramic film layer, and then form a ceramic film layer with a double-layer structure;

[0009] In the double-layer ceramic film layer, the inner layer is in contact with the substrate and is dense, providing corrosion resistance; the outer layer has a delamination defect. When the external stress is too large, the delamination defect causes the ceramic film layer to gradually fall off to increase the fatigue life of the film layer; the overall thickness of the ceramic film layer does not exceed 20μm; preferably, the thickness of the inner layer is 2-10μm, and the thickness of the outer layer is 2-10μm.

[0010] In a preferred embodiment, the filamentary or columnar steel includes one or more of carbon steel, microalloyed steel and alloy steel based on Fe; preferably, the filamentary or columnar steel includes common steel series such as Q235, 25Cr2Ni4MoV, X80, etc.; more preferably, the diameter of the filamentary or columnar steel is 1-10mm; most preferably, the filamentary or columnar steel is pre-treated for degreasing and decontamination by conventional methods known to those skilled in the art.

[0011] In a preferred embodiment, the inert electrode comprises one or more of platinum sheet, graphite and stainless steel; the inert electrode is ring-shaped; preferably, the filamentary or cylindrical steel is placed at the center of the ring-shaped inert electrode.

[0012] In a preferred embodiment, the distance between the anode and the cathode is 3-20 cm.

[0013] In a preferred embodiment, the electrolyte of the micro-arc oxidation process includes one or more of aluminates, phosphates and silicates; preferably, acidic and alkaline substances are added to the electrolyte to adjust the pH to 8.5-9.5.

[0014] In a preferred embodiment, the micro-arc oxidation process has an operating voltage of 100-1200 V, an operating frequency of 100-2500 Hz, and a current density of 0.01-3.00 A / cm 2 , the duty cycle is 5-60%, the processing time is 5-30min, and the reaction temperature is 0-40℃.

[0015] In a preferred embodiment, the power of the ultrasonic treatment is 2500-5000 W and the frequency is 20-50 kHz.

[0016] In a preferred embodiment, the ultrasonic treatment comprises evenly distributing at least four ultrasonic probes at equal distances within the electrolysis device.

[0017] In the present invention, the ultrasonic field is applied after the plasma appears, and the power is far greater than that of the traditional ultrasonic-assisted plasma electrolytic oxidation process. Through the cavitation effect of the high-power ultrasonic field, a large number of pores and corresponding strong shock waves are generated, causing defects in the plasma electrolytic oxidation ceramic film layer. On the one hand, the defects improve the plasma discharge density and its uniformity, and reduce the breakdown potential. On the other hand, the defects gradually develop under the continuous ultrasonic action, and eventually form a layered feature, that is, induce layered defects in the ceramic film layer. Then, through the cavitation effect and mechanical effect of the high-power ultrasonic field, combined with its shock wave and mechanical action, the deposited oxides in the film layer are destroyed, thereby reducing the thickness of the ceramic film layer. Finally, a ceramic film layer with a double-layer structure is formed, in which: the inner layer is dense and provides corrosion resistance; the outer layer has a layered feature, and the overall film thickness does not exceed 20μm, ensuring the fatigue life of the filamentous or columnar steel.

[0018] Another object of the present invention is to provide an application of any of the above-mentioned steel surface enhancement methods based on high-power ultrasound-assisted plasma electrolytic oxidation in the preparation of steel wires and rigging for marine engineering.

[0019] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0020] (1) The present invention only requires a one-step micro-arc oxidation process to prepare a micro-arc oxidation film layer with good corrosion resistance, which can be effectively applied to the surface treatment method of filamentary or cylindrical steel wire ropes for marine engineering, and significantly improves their marine corrosion resistance without affecting their fatigue life.

[0021] (2) The present invention promotes the homogenization of plasma discharge and reduces its energy density by introducing ultrasonic-assisted technology and annular electrode design, thereby ensuring the smooth growth of the micro-arc oxidation film layer, thereby promoting the preparation of a micro-arc oxidation ceramic film layer with good bonding strength, few defects and excellent corrosion resistance.

[0022] (3) The present invention is realized by adding an ultrasonic generator to the existing equipment, and there is no need to make large-scale improvements to the existing system. The method not only retains the original micro-arc oxidation characteristics of high hardness and high wear resistance, but also is simple and convenient to operate, has low requirements on equipment, is simple and fast, and is conducive to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] These and / or other aspects and advantages of the present invention will become more clear and easier to understand from the following detailed description of the embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0024] Figure 1 A schematic cross-sectional view of a ceramic membrane with layered defects prepared in the present invention;

[0025] Figure 2 This is a photograph of a cross section of a ceramic membrane prepared in Example 1 of the present invention;

[0026] Figure 3 This is the 0.01 Hz electrochemical impedance comparison of the ceramic membrane prepared in Example 1 of the present invention;

[0027] Figure 4 The effect of the ceramic membrane prepared in Example 1 of the present invention on fatigue life;

[0028] Figure 5 This is a photograph of a cross section of a ceramic membrane prepared in Example 2 of the present invention;

[0029] Figure 6 This is the 0.01 Hz electrochemical impedance comparison of the ceramic membrane prepared in Example 2 of the present invention;

[0030] Figure 7 The effect of the ceramic membrane prepared in Example 2 of the present invention on fatigue life;

[0031] Figure 8 This is a photograph of a cross section of a ceramic membrane obtained in Example 3 of the present invention;

[0032] Fig. 9 This is the 0.01 Hz electrochemical impedance comparison of the ceramic membrane prepared in Example 3 of the present invention;

[0033] Fig.10 This is the effect of the ceramic membrane prepared in Example 3 of the present invention on fatigue life. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods, but it should be understood that the protection scope of the present invention is not limited to the specific implementation methods.

[0035] The embodiment of the present invention solves the problem in the prior art that after plasma electrolytic oxidation on the surface of filamentary or columnar steel, the fatigue life of the ceramic film layer obtained is poor by providing a steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation and its application.

[0036] The general idea of ​​the surface enhancement method of the filamentary or columnar steel provided in the present invention includes: using aluminate, phosphate or silicate solution system as electrolyte, using filamentary or columnar steel as micro-arc oxidation anode, and using an annular inert electrode as micro-arc oxidation cathode to perform micro-arc oxidation. While micro-arc oxidation, the electrolyte is uniformly subjected to high-power ultrasonic treatment, so that a ceramic film layer with high bonding strength and stratification characteristics can be generated in situ on the anode surface. The schematic diagram of the obtained ceramic cross section is shown as follows Figure 1 As shown in the figure, it can be seen that the inner layer in contact with the substrate is dense and can provide excellent corrosion resistance; while the outer layer has multiple layer defects. When the external stress is too large, fatigue cracks will be initiated and grown inside the film layer. The layered defects will cause the ceramic film layer to gradually fall off to delay the appearance of fatigue cracks, thereby increasing its fatigue life. Therefore, the ceramic film layer prepared by the present invention has excellent marine corrosion resistance and does not affect its strain-controlled low-cycle fatigue performance. It can be used as a surface treatment method for steel wire and its rigging for marine engineering.

[0037] The technical solution of the present application is described in detail below through specific embodiments:

[0038] Unless otherwise specified, the technical means used in the present invention are conventional means well known to those skilled in the art, and the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods. The reagents used in the present invention are analytically pure unless otherwise specified.

[0039] Example 1

[0040] (1) A high-carbon steel wire with a diameter of 2.6 mm was degreased and then polished with sandpaper step by step, cleaned with acetone and dried; the sample was wrapped with insulating tape to ensure that the size exposed to the solution was 20 mm;

[0041] (2) preparing a plasma electrolytic oxidation solution, comprising 20 g / L sodium silicate and 1.2 g / L sodium dihydrogen phosphate, and adding a small amount of NaOH / HCl to adjust the pH to about 9.0; stirring the solution thoroughly with a magnetic stirrer to uniformly disperse the electrolyte;

[0042] (3) The pretreated high-carbon steel wire was used as the anode and the annular stainless steel was used as the cathode. The anode and cathode were connected to a pulse power supply, and the distance between the cathode and the anode plates was 6 cm. The anode and cathode were placed in the above electrolyte. Four ultrasonic generators were evenly distributed in the solution. The ultrasonic field with a power of 2000 W and a frequency of 50 kHz was used to assist the plasma electrolytic oxidation process. The power supply parameters were set as follows: the current density was 1.20 A / cm 2 , frequency is 2000Hz, total duty cycle is 15%, temperature is 30℃, and time is 1200s.

[0043] (4) After the reaction is completed, the sample with the ceramic film layer is taken out, rinsed with deionized water, and naturally dried to obtain the corresponding plasma electrolytic oxidation ceramic film layer.

[0044] The cross-sectional morphology of the prepared plasma electrolytic oxidation ceramic film is as follows: Figure 2 As shown, it can be seen that through high-power ultrasound-assisted plasma electrolytic oxidation treatment, the inner layer maintains a high density, while the outer layer shows significant stratification characteristics, and the overall thickness of the film layer is only ~20μm.

[0045] Comparison of electrochemical impedance spectroscopy of the prepared ceramic membrane Figure 3 As shown, it can be seen that high-power ultrasonic-assisted plasma electrolytic oxidation (UPEO) treatment greatly improves the corrosion resistance of filamentary steel (Bare).

[0046] Comparison of strain-controlled low-cycle fatigue life of the prepared ceramic film Figure 4 As shown, it can be seen that the fatigue life (strain amplitude 0.2-1.0%) of the high carbon steel wire after high power ultrasonic assisted plasma electrolytic oxidation is equivalent to that of the high carbon steel wire without surface treatment, and no deterioration phenomenon occurs.

[0047] Example 2

[0048] (1) Degrease and cleanse a low-carbon steel wire with a diameter of 1.25 mm, then polish it step by step with 600#, 1000#, 1500#, and 2000# SiC sandpaper, clean it with acetone, and dry it; wrap the sample with insulating tape to ensure that the size exposed to the solution is 20 mm;

[0049] (2) preparing a micro-arc oxidation solution, comprising 10 g / L sodium aluminate and 10 g / L sodium silicate, and adding a small amount of NaOH / HCl to adjust the pH to about 9.0; and stirring the solution fully with a magnetic stirrer to uniformly disperse the electrolyte;

[0050] (3) The pretreated low-carbon steel wire was used as the anode and the annular stainless steel was used as the cathode. The anode and cathode were connected to a pulse power supply, and the distance between the cathode and the anode plates was 10 cm. The anode and cathode were placed in the above electrolyte. The ultrasonic field assisted plasma electrolytic oxidation process with a power of 2500 W and a frequency of 20 kHz was used. The power supply parameters were set as follows: the current density was 0.25 A / cm 2 , frequency is 1000Hz, total duty cycle is 10%, temperature is 30℃, time is 600s;

[0051] (4) After the reaction is completed, the sample with the ceramic film layer is taken out, rinsed with deionized water, and naturally dried to obtain the corresponding micro-arc oxidation ceramic film layer.

[0052] The cross-sectional morphology of the prepared plasma electrolytic oxidation ceramic film is as follows: Figure 5 As shown, it can be seen that through high-power ultrasound-assisted plasma electrolytic oxidation treatment, the inner layer maintains a high density, while the outer layer shows significant stratification characteristics, and the overall thickness of the film layer is only ~20μm.

[0053] Comparison of electrochemical impedance spectroscopy of the prepared ceramic membrane Figure 6 As shown, it can be seen that high-power ultrasonic-assisted plasma electrolytic oxidation (UPEO) treatment greatly improves the corrosion resistance of filamentary steel (Bare).

[0054] Comparison of strain-controlled low-cycle fatigue life of the prepared ceramic film Figure 7 As shown, it can be seen that the fatigue life (strain amplitude 0.2-1.2%) of the low-carbon steel wire after high-power ultrasonic assisted plasma electrolytic oxidation is equivalent to that of the low-carbon steel wire without surface treatment, and no deterioration phenomenon occurs.

[0055] Example 3

[0056] (1) A microalloyed steel wire (25Cr2Ni4MoV) with a diameter of 1.6 mm was degreased and then polished step by step, cleaned with acetone, and dried; the specimen was wrapped with insulating tape to ensure that the size exposed to the solution was 30 mm;

[0057] (2) preparing a plasma electrolytic oxidation solution comprising 40 g / L sodium silicate and 2 g / L sodium dihydrogen phosphate; and stirring the solution thoroughly with a magnetic stirrer to uniformly disperse the electrolyte;

[0058] (3) The pretreated microalloyed steel wire was used as the anode and the annular stainless steel was used as the cathode. The anode and cathode were connected to a pulse power supply, and the distance between the cathode and the anode plates was 12 cm. The anode and cathode were placed in the above electrolyte. The power was 5000 W and the frequency was 50 kHz. The ultrasonic field assisted plasma electrolytic oxidation process. The power supply parameters were set as follows: the current density was 2.40 A / cm 2, frequency is 1500Hz, total duty cycle is 15%, temperature is 30℃, time is 1200s;

[0059] (4) After the reaction is completed, the sample with the ceramic film layer is taken out, rinsed with deionized water, and naturally dried to obtain the corresponding ceramic film layer.

[0060] The cross-sectional morphology of the prepared plasma electrolytic oxidation ceramic film is as follows: Figure 8 As shown, it can be seen that through high-power ultrasound-assisted plasma electrolytic oxidation treatment, the inner layer maintains a high density, while the outer layer shows significant stratification characteristics, and the overall thickness of the film layer is only ~20μm.

[0061] Comparison of electrochemical impedance spectroscopy of the prepared ceramic membrane Fig. 9 As shown, it can be seen that high-power ultrasonic-assisted plasma electrolytic oxidation (UPEO) treatment greatly improves the corrosion resistance of filamentary steel (Bare).

[0062] Comparison of strain-controlled low-cycle fatigue life of the prepared ceramic film Fig.10 As shown, it can be seen that the fatigue life (strain amplitude 0.2-1.3%) of the microalloyed steel wire after high-power ultrasonic assisted plasma electrolytic oxidation is equivalent to that of the microalloyed steel wire without surface treatment, and no deterioration phenomenon occurs.

[0063] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is clear that many changes and variations can be made based on the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes. The scope of the present invention is intended to be limited by the claims and their equivalents.

Claims

1. A method for surface enhancement of steel based on high-power ultrasound-assisted plasma electrolytic oxidation, characterized in that: Micro-arc oxidation is performed using a filamentary or cylindrical steel material as an anode and a ring-shaped inert electrode as a cathode to improve the uniformity of the electric field during the micro-arc oxidation process so that the resulting ceramic film layer grows uniformly; at the same time, high-power ultrasonic treatment is performed during the micro-arc oxidation process to generate a large number of pores and strong shock waves, thereby inducing layered defects in the resulting ceramic film layer, destroying non-compactly deposited oxides, reducing the thickness of the ceramic film layer, and thereby forming a ceramic film layer with a double-layer structure; In the double-layer ceramic film layer, the inner layer is in contact with the substrate and is dense, providing corrosion resistance; the outer layer has a delamination defect. When the external stress is too large, the delamination defect causes the ceramic film layer to gradually fall off to increase the fatigue life of the film layer; the overall thickness of the ceramic film layer does not exceed 20μm.

2. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The filamentary or columnar steel material includes one or more of carbon steel, microalloyed steel and alloy steel based on Fe.

3. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The inert electrode comprises one or more of platinum sheet, graphite and stainless steel; and the inert electrode is in a ring shape.

4. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The distance between the anode and the cathode is 3-20 cm.

5. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The electrolyte of the micro-arc oxidation process includes one or more of aluminate, phosphate and silicate.

6. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The operating voltage of the micro-arc oxidation process is 100-1200V, the operating frequency is 100-2500Hz, and the current density is 0.01-3.00A / cm 2 , the duty cycle is 5-60%, the processing time is 5-30 minutes, and the reaction temperature is 0-40°C.

7. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 1, characterized in that: The power of the ultrasonic treatment is 2500-5000W, and the frequency is 20-50kHz.

8. The steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation according to claim 7, characterized in that: The ultrasonic treatment includes evenly distributing at least four ultrasonic probes at equal distances within the electrolysis device.

9. Application of the steel surface enhancement method based on high-power ultrasound-assisted plasma electrolytic oxidation as described in any one of claims 1 to 8 in the preparation of steel wire and rigging for marine engineering.

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