Method for stripping reaction layer on surface of high-temperature alloy return scrap

Abstract

The invention relates to a stripping method for a reaction layer on the surface of a high-temperature alloy return scrap, and relates to the technical field of cleaning, recycling and reusing of metal materials. According to the main technical scheme, the stripping method for the reaction layer on the surface of the high-temperature alloy return scrap comprises the steps that the high-temperature alloy return scrap serves as an anode, and an inert material serves as a cathode; the anode and the cathode are placed in an electrolyte for electrolytic treatment so as to remove a surface reaction layer on the high-temperature alloy return scrap; wherein the electrolyte contains 1 to 3 mol / L of chlorine salt electrolyte additive and 0 to 2 mol / L of weak acid. The green and efficient stripping method for the reaction layer on the surface of the high-temperature alloy return scrap is mainly provided, the content of gas impurity elements is reduced, and the cyclic utilization rate of the return scrap is increased.

Description

Technical Field

[0001] The present invention relates to the technical field of metal material cleaning, recycling and reuse, and in particular to a method for stripping a surface reaction layer of a high-temperature alloy return material. Background Art

[0002] High-temperature alloys, known as the crown jewels of industry, boast high high-temperature strength, excellent oxidation and corrosion resistance, good fatigue performance, and fracture toughness. They are widely used in critical components such as aerospace engines. In recent years, annual production of high-temperature alloys has reached 50,000 tons. However, due to low utilization rates, the amount of returned material is increasing year by year.

[0003] The returned materials mainly include waste materials generated during smelting and processing, as well as scrapped materials from service. The surface contains reaction layers (chromium-rich layers and interdiffusion layers) with complex types and structures, including Cr2O3, Al2O3, TiO2, TiN, Ni-Cr-O spinel, etc. They are stable in properties and closely bonded to the alloy matrix.

[0004] The main method for recycling return materials is pyrometallurgical remelting. However, the reaction layer in the return materials contains a large amount of oxygen and nitrogen gas impurity elements, which easily produce slag during the smelting process and form refractory inclusions with alloying elements, seriously affecting the purity and various properties of the alloy. Therefore, it is necessary to remove the reaction layer of the high-temperature alloy return materials and recycle them for reuse, which is conducive to reducing the consumption of strategic metal resources, alleviating environmental pollution, and reducing the production cost of aircraft engines. At present, the methods for removing the reaction layer on the surface of high-temperature alloys mainly include shot blasting and pickling. For example: The first related technology discloses a surface treatment method for high-temperature alloy return materials, which classifies the high-temperature alloy return materials and then performs shot blasting and grinding treatments in sequence, and finally uses hydrochloric acid and nitric acid solutions for pickling to obtain a clean return material surface. The second related technology discloses a treatment method for aluminum-nickel-based high-temperature alloy return materials, which uses a pickling solution composed of nitric acid, hydrofluoric acid, hydrochloric acid, and hexamethylenetetramine to pickle the aluminum-nickel-based high-temperature alloy after annealing and shot blasting to remove the oxide layer on the surface of the high-temperature alloy. The third related technology discloses a method and equipment for removing the oxide layer of titanium and titanium alloy wires, which removes the oxide layer on the surface of the alloy through steps such as straightening, dephosphorization, polishing, cooling and dust removal.

[0005] The methods used in the above-mentioned prior art primarily involve pickling combined with mechanical methods such as shot blasting and grinding. However, pickling requires specialized pickling equipment, resulting in a complex process, high costs, and low efficiency. Pickling also involves the use of volatile, pungent, flammable, and highly corrosive chemicals such as hydrochloric acid, nitric acid, hydrofluoric acid, and hexamethylenetetramine, making it highly hazardous and environmentally unfriendly. Furthermore, mechanical methods such as shot blasting and grinding carry the risk of secondary contamination during operation.

[0006] In summary, there is an urgent need for a green and efficient method for stripping the surface reaction layer of high-temperature alloy return materials. Summary of the Invention

[0007] In view of this, the present invention provides a method for stripping the surface reaction layer of high-temperature alloy return material, the main purpose of which is to solve the problems of low efficiency and environmental unfriendliness in the existing method for removing the surface reaction layer of high-temperature alloy return material.

[0008] To achieve the above objectives, the present invention mainly provides the following technical solutions:

[0009] In one aspect, a method for stripping a reaction layer on the surface of a high-temperature alloy return material comprises the following steps:

[0010] Electrolytic treatment step: using the high-temperature alloy return material as an anode and an inert material as a cathode; placing the anode and cathode in an electrolyte and performing electrolytic treatment to remove a surface reaction layer on the high-temperature alloy return material; wherein the electrolyte contains 1 to 3 mol / L of a chloride salt electrolyte additive and 0 to 2 mol / L of a weak acid.

[0011] Preferably, when the high-temperature alloy return material is the first type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows:

[0012] The electrode potential is 400-600 mV vs. SHE. The pH of the electrolyte is 2.5-7. The concentration of the weak acid in the electrolyte is 0-1 mol / L. The concentration of the chloride electrolyte additive is 1-1.5 mol / L. The current density of the electrolytic treatment is 0.45-0.8 A / cm 2 , the electrolysis treatment time is 20 to 30 minutes;

[0013] Wherein, the thickness of the surface reaction layer of the first type high-temperature alloy return material is less than 20 μm.

[0014] Preferably, the surface reaction layer of the first type of high-temperature alloy return material includes a chromium-rich layer and an interdiffusion layer from the outside to the inside; preferably, the thickness of the chromium-rich layer is 2 to 5 μm, and the thickness of the interdiffusion layer is 5 to 15 μm; preferably, the chromium-rich layer includes Cr2O3, and preferably also includes TiO2; the interdiffusion layer includes TiO2 and Al2O3; and / or the first type of high-temperature alloy return material includes high-temperature alloy return material after service at a temperature below 800°C.

[0015] Preferably, when the high-temperature alloy return material is the second type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows:

[0016] The electrode potential is 600-800 mV vs. SHE. The pH of the electrolyte is 2-2.5. The concentration of the weak acid in the electrolyte is 1-1.5 mol / L. The concentration of the chloride electrolyte additive is 1.5-2 mol / L. The current density of the electrolytic treatment is 0.65-0.8 A / cm 2 , the electrolysis treatment time is 30 to 40 minutes;

[0017] Wherein, the thickness of the surface reaction layer of the second type high-temperature alloy return material is 20 to 60 μm.

[0018] Preferably, the surface reaction layer of the second type of high-temperature alloy return material includes a chromium-rich layer and an interdiffusion layer from the outside to the inside; preferably, the thickness of the chromium-rich layer is 8 to 20 μm, and the thickness of the interdiffusion layer is 25 to 50 μm; preferably, the chromium-rich layer includes Cr2O3, TiO2, and Al2O3; the interdiffusion layer includes TiO2, Al2O3, NiCr2O4, and TiN; and / or the second type of high-temperature alloy return material includes high-temperature alloy smelting and / or processing waste.

[0019] Preferably, when the high-temperature alloy return material is a third type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows:

[0020] The electrode potential is 1000-1500 mV vs. SHE. The pH of the electrolyte is 1.5-2. The concentration of the weak acid in the electrolyte is 1.5-2 mol / L. The concentration of the chloride electrolyte additive is 2-3 mol / L. The current density of the electrolytic treatment is 0.8-1 A / cm 2 , after electrolysis for 20 to 25 minutes, ultrasonication is performed and electrolysis is continued for 20 to 25 minutes; preferably, the power of the ultrasound is 300 to 500W;

[0021] Wherein, the thickness of the surface reaction layer of the third type high-temperature alloy return material is 100-250 μm.

[0022] Preferably, the surface reaction layer of the third type high temperature alloy return material includes, from the outside to the inside, a chromium-rich layer and an interdiffusion layer; preferably, the thickness of the chromium-rich layer is 15 to 50 μm, and the thickness of the interdiffusion layer is 80 to 200 μm; preferably, the chromium-rich layer includes Cr2O3, TiO2 and TiN; the interdiffusion layer includes NiCr2O4 spinel, Al2O3 (preferably dispersed), TiO2 (preferably continuous), and continuous TiN wrapped Al2O3 (preferably strip-shaped continuous TiN wrapped Al2O3); and / or

[0023] The third type of high-temperature alloy return material includes high-temperature alloy return material after service at a temperature not lower than 800°C.

[0024] Preferably, before the electrolytic treatment step, the method further comprises:

[0025] Classification step: classifying the high-temperature alloy return material according to the type of the reaction layer on the high-temperature alloy return material, and dividing the high-temperature alloy return material into different types;

[0026] Wherein, in the electrolytic treatment step, the parameters of the electrolytic treatment are controlled according to the type of the high-temperature alloy return material;

[0027] Preferably, in the classification step, the high-temperature alloy return material is classified into a first type of high-temperature alloy return material, a second type of high-temperature alloy return material, and a third type of high-temperature alloy return material.

[0028] Preferably, in the step of electrolytic treatment:

[0029] The weak acid includes one or more of citric acid, acetic acid, malic acid, oxalic acid, ethylenediaminetetraacetic acid, and tartaric acid; preferably, when the high-temperature alloy return material is a first-type high-temperature alloy return material, the weak acid is acetic acid; when the high-temperature alloy return material is a second-type high-temperature alloy return material, the weak acid is malic acid; when the high-temperature alloy return material is a third-type high-temperature alloy return material, the weak acid is citric acid; and / or

[0030] The chloride electrolyte additive includes sodium chloride and / or potassium chloride; and / or

[0031] The distance between the anode and cathode is 10 to 30 cm; and / or

[0032] The cathode is made of graphite; and / or

[0033] The mass ratio of the electrolyte to the high-temperature alloy return material is (5-30):1.

[0034] On the other hand, an embodiment of the present invention provides a high-temperature alloy return material after stripping off the surface reaction layer, wherein the high-temperature alloy return material is treated by any of the above-mentioned methods for stripping off the surface reaction layer of the high-temperature alloy return material to obtain the high-temperature alloy return material after stripping off the surface reaction layer; preferably, the oxygen content in the surface layer of the high-temperature alloy return material after stripping off the surface reaction layer is within 5 ppm of the oxygen content of the alloy matrix; preferably, the nitrogen content in the surface layer of the high-temperature alloy return material after stripping off the surface reaction layer is within 5 ppm of the nitrogen content of the alloy matrix.

[0035] Compared with the prior art, the method for stripping the surface reaction layer of high-temperature alloy return material of the present invention has at least the following beneficial effects:

[0036] The embodiment of the present invention provides a method for stripping the reaction layer on the surface of high-temperature alloy return material, which uses the high-temperature alloy return material as an anode and an inert material as a cathode; the anode and cathode are placed in an electrolyte and electrolytically treated to remove the reaction layer on the high-temperature alloy return material; wherein the electrolyte contains 1 to 3 mol / L of chloride electrolyte additives and 0 to 2 mol / L of weak acid. It should be noted that the electrolyte of the present invention contains Cl with a small ion radius and strong penetrating ability. - , they can be adsorbed on the reaction layer, enter the reaction layer through tiny pores and occupy the oxygen vacancies in the reaction layer, destroying the dynamic balance of the reaction layer structure and promoting its dissolution. Here, the above method of the present invention avoids the use of strong corrosive and volatile odorous strong acids such as hydrochloric acid, nitric acid, and hydrofluoric acid, as well as flammable and allergenic substances such as hexamethylenetetramine, and no toxic gases such as NO and Cl2 are generated during the operation, there is no need to control the temperature, and no violent reactions such as splashing occur during the experiment, which is more environmentally friendly and improves safety. In addition, the above method of the present invention is simple to operate, takes a short time, does not require special equipment, and has no site requirements, which saves production costs and improves efficiency. After electrolytic treatment, there is no nitride and oxide residue on the surface of the high-temperature alloy return material, the overall surface is bright and clean, and the oxygen and nitrogen content is effectively controlled to reach the oxygen and nitrogen content level of the alloy core, providing conditions for the next clean remelting and smelting of the return material.

[0037] Furthermore, an embodiment of the present invention provides a method for stripping the surface reaction layer of high-temperature alloy return material. For the first type of high-temperature alloy return material (high-temperature alloy return material after service at a lower temperature, the thickness of the surface reaction layer is less than 20μm), the electrolyte is a single chloride solution (the concentration of the chloride salt electrolyte additive is 1-1.5mol / L) or an appropriate amount of acetic acid is added to enhance the acidity, and the electrode potential of the electrolyte is maintained at 400-600mV vs. SHE., which is higher than the standard electrode potential of the main metal elements Cr, Ti, Al, Ni, etc. in the reaction layer, which is conducive to the dissolution reaction. The external electric field can accelerate the diffusion and migration rate of ions and at the same time ionize hydroxyl radicals in the solution: H2O→·OH+H + +e - , while increasing the electrode potential of the system, it also enhances the acidity and increases the dissolution rate of the surface reaction layer. - Under the combined action of the electric field, the stability of Cr2O3, NiO, TiO2, etc. in the reaction is significantly reduced, and the occurrence state changes to form loose, soluble chlorides and chlorine coordination compounds and dissociate.

[0038] Furthermore, embodiments of the present invention provide a method for stripping the surface reaction layer of high-temperature alloy return material. For the second type of high-temperature alloy return material (high-temperature alloy smelting and / or processing waste, with a surface reaction layer thickness of 20 to 60 μm), malic acid is preferably used as the electrolyte, and the concentration of a chloride electrolyte additive in the electrolyte is controlled to 1.5 to 2 mol / L, maintaining the electrode potential at 600 to 800 mV vs. SHE. It should be noted that during electrolysis, aluminum and chromium form a passivation layer that hinders electrolysis. Malate ions can complex with these passivation layers to form soluble substances, promoting electrolysis and aiding in the dissolution of thicker reaction layers containing Cr2O3, TiO2, and the like in this type of return material. Specifically, malic acid, as a dibasic acid, possesses strong acidity and can complex with metal ions to form soluble substances. A chloride electrolyte additive at a concentration of 1.5 to 2 mol / L can increase the solution's conductivity and enhance the penetration of chloride ions into the chromium-rich layer. An electrode potential of 600 to 800 mV vs. SHE improves the solution's oxidizing properties. Here, malic acid, an electrolyte additive at a concentration of 1.5 to 2 mol / L, and an electrode potential maintained at 600 to 800 mV vs. SHE. synergistically promote the electrolysis reaction and promote the dissolution of a thicker reaction layer containing Cr2O3, TiO2, etc.

[0039] Furthermore, embodiments of the present invention provide a method for stripping the surface reaction layer of high-temperature alloy return material. This method targets the third type of high-temperature alloy return material (high-temperature alloy return material after service at higher temperatures, with a surface reaction layer thickness of 100 to 250 μm), which has a significantly increased thickness and an internal diffusion layer that easily forms a structurally stable TiN-encapsulated Al2O3. Citric acid is used as the electrolyte, while the chloride electrolyte additive is controlled to 2 to 3 mol / L, and an ultrasonic field is introduced. Citric acid, as a triprotic acid, exhibits stronger acidity under the action of an electric field, and its ligand structure, containing more hydroxycarboxylic acid groups, provides it with stronger complexing ability. Furthermore, the hydroxyl and carboxyl groups, as hydrophilic groups, enhance wettability, reducing the surface tension of the electrolyte solution and the contact angle between the droplet and the return material surface, inhibiting the adsorption of anode products on the surface, and promoting the dissociation of the more complex chromium-rich layer of this type of return material. With a 2-3 mol / L chloride electrolyte additive and an electrode potential of 1000-1500 mV vs. SHE, the tremendous heat and pressure generated by the ultrasonic field accelerate the dissolution of the surface chromium-rich layer, centered around chromium oxide. Simultaneously, the cavitation effect generates more hydroxyl radicals in the electrolyte, both of which facilitate the leaching of metallic elements. Compounds in the internal diffusion layer (e.g., TiN encapsulating Al2O3) are more stable than the alloy matrix and less likely to participate in the dissolution process. During electrolysis, they preferentially dissolve the matrix, creating voids between the Al2O3 and TiN. Ultrasound exerts a strong impact force at the liquid-solid interface, destroying the solid film at the interface while accelerating the shedding of Al2O3 and TiN, thereby improving the stripping efficiency of the reaction layer.

[0040] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is a SEM image of the surface cross section of the first type of high-temperature alloy return material in Example 1 before and after electrolysis treatment, wherein: Figure 1 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the first type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 1 Figure (b) is a SEM image of the surface cross-section of the first type of high-temperature alloy return material after electrolysis treatment in this embodiment;

[0042] Figure 2 : is a surface cross-sectional SEM image of the second type of high-temperature alloy return material before and after electrolysis treatment in Example 2, wherein: Figure 2 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the second type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 2Figure (b) is a SEM image of the surface cross-section of the second type of high-temperature alloy return material after electrolysis treatment in this embodiment;

[0043] Figure 3 : is a surface cross-sectional SEM image of the second type of high-temperature alloy return material before and after electrolysis treatment in Example 3, wherein: Figure 3 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the second type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 3 Figure (b) is a SEM image of the surface cross-section of the second type of high-temperature alloy return material after electrolysis treatment in this embodiment;

[0044] Figure 4 These are the SEM images and element distribution of the second type of return material before and after electrolytic treatment. DETAILED DESCRIPTION

[0045] To further illustrate the technical means and effects employed by the present invention to achieve its intended objectives, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention is provided in conjunction with the accompanying drawings and preferred embodiments. In the following description, different references to "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0046] There are few reports on the use of electrolysis to remove the surface reaction layer (chromium-rich layer and interdiffusion layer; the chromium-rich layer is located on the surface of the interdiffusion layer) of high-temperature alloys. The electrolysis method is mostly used to dissolve alloys. For example, related technology reports a method for electrochemical dissolution of ruthenium-cobalt alloys. This method uses 50-75wt% sulfuric acid and 1-10wt% sodium chloride or potassium chloride as electrolytes to electrochemically dissolve the alloy and recover the alloy elements in the solution.

[0047] The electrolytic method removes the surface reaction layer (chromium-rich layer and interdiffusion layer) of the high-temperature alloy, eliminating the need for space or special equipment. The overall process is streamlined, more efficient, and avoids the risk of secondary contamination during operation. Furthermore, the present invention uses a weak acid electrolysis method, avoiding the use of highly corrosive and volatile strong acids such as hydrochloric acid, nitric acid, and hydrofluoric acid. No toxic or irritating gases are produced during the process, making it more environmentally friendly and safer. Cleanliness is significantly improved after electrolysis, meeting remelting requirements.

[0048] The main scheme of the present invention is as follows:

[0049] An embodiment of the present invention provides a method for stripping a reaction layer on the surface of a high-temperature alloy return material, which comprises the following steps:

[0050] Electrolytic treatment step: using the high-temperature alloy return material as an anode and an inert material as a cathode; placing the anode and cathode in an electrolyte and performing electrolytic treatment to remove a surface reaction layer on the high-temperature alloy return material; wherein the electrolyte contains 1 to 3 mol / L of a chloride salt electrolyte additive and 0 to 2 mol / L of a weak acid.

[0051] Wherein, in the electrolytic treatment step, the parameters of the electrolytic treatment are controlled according to the type of the high-temperature alloy return material.

[0052] High-temperature alloy return materials can be divided into three main categories based on the type and structure of their reaction layers. The first category is return materials with a relatively simple reaction layer structure formed during service at relatively low temperatures (below 800°C). The surface reaction layer comprises a chromium-rich layer and an interdiffusion layer from the outside to the inside. The chromium-rich layer comprises Cr2O3 and preferably also TiO2. The interdiffusion layer comprises TiO2 and Al2O3, and the overall thickness of the surface reaction layer is within 20μm. The second category is mainly waste from high-temperature alloy smelting and processing. The surface reaction layer of this type of return material comprises a chromium-rich layer and an interdiffusion layer from the outside to the inside. The chromium-rich layer comprises Cr2O3, TiO2, and Al2O3. The interdiffusion layer comprises TiO2, Al2O3, NiCr2O4, and TiN. The thickness of the surface reaction layer is approximately 20 to 60μm. The third category is the return material with a complex chromium-rich layer structure formed by service at a higher temperature (not less than 800℃). Its surface reaction layer includes a chromium-rich layer and an interdiffusion layer from the outside to the inside; among them, the chromium-rich layer includes Cr2O3, TiO2 and TiN; the interdiffusion layer includes NiCr2O4, Al2O3, TiO2, and TiN wrapped Al2O3. The thickness of the reaction layer is about 100 to 250μm.

[0053] When the high-temperature alloy return material is the first type of high-temperature alloy return material, the parameters of the electrolytic treatment are controlled as follows: the electrode potential is 400-600 mV vs. SHE. (vs. SHE. here refers to the reference hydrogen standard electrode. The reference hydrogen standard electrode has an electrode potential of 400-600 mV), the pH of the electrolyte is 2.5-7, the concentration of the weak acid in the electrolyte is 0-1 mol / L, the concentration of the chloride electrolyte additive is 1-1.5 mol / L, and the current density of the electrolytic treatment is 0.45-0.8 A / cm 2 , the electrolysis treatment time is 20 to 30 minutes.

[0054] When the high-temperature alloy return material is the second type of high-temperature alloy return material, the parameters of the electrolytic treatment are controlled as follows: the electrode potential is 600-800 mV vs. SHE., the pH of the electrolyte is 2-2.5, the concentration of the weak acid in the electrolyte is 1-1.5 mol / L, the concentration of the chloride electrolyte additive is 1.5-2 mol / L, and the current density of the electrolytic treatment is 0.65-0.8 A / cm 2 , the electrolysis treatment time is 30 to 40 minutes.

[0055] When the high-temperature alloy return material is the third type of high-temperature alloy return material, the parameters of the electrolytic treatment are controlled as follows: the electrode potential is 1000-1500 mV vs. SHE., the pH of the electrolyte is 1.5-2, the concentration of the weak acid in the electrolyte is 1.5-2 mol / L, the concentration of the chloride electrolyte additive is 2-3 mol / L, and the current density of the electrolytic treatment is 0.8-1 A / cm 2 After electrolysis for 20 to 25 minutes, ultrasound is performed and electrolysis is continued for 20 to 25 minutes; preferably, the power of ultrasound is 300 to 500W.

[0056] In addition, it should be noted that: (1) For the preparation of the electrolysis sample (anode), the embodiment of the present invention is applicable to high-temperature alloy return materials of various shapes and sizes, and does not require prior physical or chemical treatment. (2) Weak acids include citric acid, glacial acetic acid, malic acid, oxalic acid, ethylenediaminetetraacetic acid, tartaric acid, etc. (3) Chloride electrolyte additives are used to improve the conductivity of the electrolyte and the electrolysis efficiency, such as sodium chloride, potassium chloride, etc., but not limited to these. (3) The electrolysis is carried out at room temperature, the anode is the high-temperature alloy return material, and the cathode is graphite. The anode and cathode are placed in the above-mentioned electrolyte and the distance between the two is fixed at 10 to 30 cm, and the electrolysis is carried out at a constant current. (4) The mass ratio of the electrolyte to the high-temperature alloy return material is (5 to 30):1.

[0057] Furthermore, electrolysis is performed in an electrolytic cell, which can be made of well-known acid-resistant non-metallic non-conductive materials, including quartz glass, polytetrafluoroethylene, polyethylene, polypropylene, polyester, etc. After electrolysis, the sample is rinsed with deionized water and then with alcohol, and then dried.

[0058] in, Figure 4 The SEM images and element distribution of the second type of return material before and after electrolysis treatment. Figure 4 It can be seen that the method of the embodiment of the present invention can effectively strip the reaction layer (chromium-rich layer and interdiffusion layer) in the high-temperature alloy return material. The main element composition of Ni, Co, etc. in the matrix after electrolysis is equivalent to that in the alloy core, the content of Cr, Al, Ti, and O is significantly reduced, and the cleanliness of the return material is significantly improved, meeting the requirements of remelting smelting.

[0059] The present invention is further described below by means of specific examples:

[0060] Example 1

[0061] In this embodiment, the surface reaction layer (oxygen content of 300 ppm and nitrogen content of 36 ppm) of the first type of high-temperature alloy return material is stripped. The main steps are as follows:

[0062] The first type of high temperature alloy return material that has been in service for 1000 hours at a temperature below 800℃ is processed into 0.4×0.4×3cm 3 The strip sample was taken and the cut surface and the two top ends were polished with sandpaper. They were rinsed with deionized water and anhydrous ethanol in turn and blown dry.

[0063] Use deionized water to prepare a mixed solution of acetic acid and sodium chloride (100 mL) as the electrolyte. The concentration of acetic acid is 1 mol / L, and the concentration of sodium chloride is 1 mol / L. The anode is a high-temperature alloy bar prepared in the above manner, and the cathode is graphite. The cathode and anode are placed in the above electrolyte and the distance between them is fixed at 10 cm. Constant current electrolysis treatment is carried out, the electrode potential is 500 mV vs. SHE., and the current density of the electrolysis treatment is 0.6 A / cm 2 , the pH value of the electrolyte is 2.5, and the electrolysis treatment time is 30 minutes.

[0064] The surface cross-section SEM images of the first type of high-temperature alloy return material in this embodiment before and after electrolysis treatment are as follows: Figure 1 As shown, Figure 1 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the first type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 1 Figure (b) is a cross-sectional SEM image of the surface layer of the first type of high-temperature alloy return material after electrolysis treatment in this embodiment. Figure 1 It can be clearly seen that before electrolysis treatment, the reaction layer thickness of the first type of high-temperature alloy return material was 7 μm, the chromium-rich layer thickness was 2 μm, and the chromium-rich layer composition was Cr2O3 and TiO2; the interdiffusion layer thickness was 5 μm, and the interdiffusion layer composition was TiO2 and Al2O3. After treatment in this embodiment, the reaction layer was significantly removed.

[0065] After electrolysis treatment, the surface layer of the first type high-temperature alloy return material of this embodiment has an O content of 4 ppm, a N content of 33 ppm, and an oxygen removal rate of 98.7%, which is close to the oxygen and nitrogen contents of the alloy matrix.

[0066] Example 2

[0067] In this embodiment, the surface reaction layer (oxygen content of 400 ppm and nitrogen content of 67 ppm) of the second type high temperature alloy return material is stripped. The main steps are as follows:

[0068] The nickel-based cast high-temperature alloy pouring head is used as the second type of high-temperature alloy return material and is processed into 0.4×0.4×3cm by wire cutting. 3 The strip sample was taken and the cut surface and the two top ends were polished with sandpaper. They were rinsed with deionized water and anhydrous ethanol in turn and blown dry.

[0069] 100 mL of a mixed solution of malic acid and sodium chloride was prepared using deionized water as the electrolyte. The concentration of malic acid was 1.5 mol / L, and the concentration of sodium chloride was 2 mol / L. The anode was a high-temperature alloy bar prepared in the above manner, and the cathode was graphite. The cathode and anode were placed in the above electrolyte and the distance between them was fixed at 10 cm. Constant current electrolysis was performed, with an electrode potential of 800 mV vs. SHE. and a current density of 0.65 A / cm 2 , the pH of the electrolyte is 2, and the electrolysis treatment time is 40 minutes.

[0070] The surface cross-section SEM images of the second type of high-temperature alloy return material in this embodiment before and after electrolysis treatment are as follows: Figure 2 As shown, Figure 2 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the second type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 2 Figure (b) is a cross-sectional SEM image of the surface layer of the second type of high-temperature alloy return material after electrolysis treatment in this embodiment. Figure 2 It can be clearly seen that before electrolysis treatment, the reaction layer thickness of the second type high-temperature alloy return material was 44 μm, of which the chromium-rich layer was 15 μm thick and composed of Cr2O3, TiO2, and Al2O3; the interdiffusion layer was 29 μm thick and composed of TiO2, Al2O3, NiCr2O4, and TiN. After treatment in this embodiment, the reaction layer was significantly removed.

[0071] After electrolytic treatment, the surface layer of the second type high-temperature alloy return material of this embodiment has an O content of 19 ppm, a N content of 45 ppm, and an oxygen removal rate of 95.3%. After treatment, the oxygen content and nitrogen content are close to those of the alloy matrix.

[0072] Example 3

[0073] In this embodiment, the surface reaction layer (oxygen content of 600 ppm and nitrogen content of 87 ppm) of the third type high temperature alloy return material is stripped. The main steps are as follows:

[0074] The third type of high temperature alloy returned material that had been in service at 1200℃ for 200h was processed into 0.4×0.4×3cm 3 The strip sample was taken and the cut surface and the two top ends were polished with sandpaper. They were rinsed with deionized water and anhydrous ethanol in turn and blown dry.

[0075] Use deionized water to prepare a mixed solution of citric acid and sodium chloride (100 mL) as the electrolyte. The concentration of citric acid is 2 mol / L, and the concentration of sodium chloride is 2 mol / L. The anode is a high-temperature alloy bar prepared in the above manner, and the cathode is graphite. The cathode and anode are placed in the above electrolyte and the distance between them is fixed at 10 cm. Constant current electrolysis treatment is carried out, the electrode potential is 1000 mV vs. SHE., and the current density of the electrolysis treatment is 0.8 A / cm 2 The pH value of the electrolyte was 1.5. After the initial electrolysis for 20 min, ultrasound was added and electrolysis was continued for another 20 min at an ultrasound power of 400 W.

[0076] The surface cross-section SEM images of the third type of high-temperature alloy return material before and after electrolysis treatment are as follows: Figure 3 As shown, Figure 3 Figure (a) is a cross-sectional SEM image of the surface layer (reaction layer) of the third type of high-temperature alloy return material of this embodiment before electrolysis treatment; Figure 3 Figure (b) is a cross-sectional SEM image of the surface layer of the third type high temperature alloy return material after electrolysis treatment in this embodiment. Figure 3 It can be clearly seen that before electrolysis treatment, the reaction layer thickness of the Type III high-temperature alloy return material was 213 μm, of which the chromium-rich layer was 43 μm thick and composed of Cr2O3, TiN, and TiO2. The interdiffusion layer was 170 μm thick and composed of NiCr2O4 spinel, continuous TiO2, dispersed Al2O3 (approximately 3 μm in size), and continuous TiN-encapsulated Al2O3 strips (approximately 20 μm or larger in size). After treatment in this embodiment, the reaction layer was significantly removed.

[0077] After electrolytic treatment, the surface layer of the third type high-temperature alloy return material of this embodiment has an O content of 13ppm, a N content of 45ppm, and an oxygen removal rate of 97.8%. After treatment, the oxygen content and nitrogen content are close to those in the alloy matrix.

[0078] Comparative Example 1

[0079] Comparative Example 1 is to peel off the surface reaction layer of the first type high-temperature alloy return material. The difference from Example 1 is that the concentration of sodium chloride in the electrolyte in Comparative Example 1 is 0.5 mol / L.

[0080] The rest is the same as Example 1.

[0081] Here, since the concentration of sodium chloride is reduced in Comparative Example 1, the resistance of the electrolyte increases, and the penetration of chloride ions into the chromium-rich layer is weakened, resulting in a decrease in the electrolysis effect.

[0082] In the surface layer of the first type of high-temperature alloy return material of Comparative Example 1 after electrolytic treatment, the O content was 59 ppm and the N content was 38 ppm. It was obvious that the oxygen content was still excessive and the removal was not complete.

[0083] Comparative Example 2

[0084] Comparative Example 2 is to peel off the surface reaction layer of the second type high temperature alloy return material. The difference from Example 2 is that the concentration of malic acid is 0.2 mol / L and the pH value of the electrolyte is 2.6.

[0085] The rest is the same as Example 2.

[0086] Here, since Comparative Example 2 reduces the concentration of malic acid in the electrolyte, the acidity and conductivity of the electrolyte decrease, and the complexation of malate ions is weakened, thereby reducing the electrolysis effect.

[0087] After electrolysis treatment, the surface layer of the second type of high-temperature alloy return material of Comparative Example 2 has an O content of 54 ppm and a N content of 48 ppm.

[0088] Comparative Example 3

[0089] Comparative Example 3 peels off the surface reaction layer of the third type high-temperature alloy return material. The difference from Example 3 is that the electrolysis treatment time in Comparative Example 3 is 40 minutes, but ultrasound is not added during the electrolysis process.

[0090] The rest is the same as Example 3.

[0091] After electrolysis treatment, the surface layer of the third type high-temperature alloy return material of Comparative Example 3 has an O content of 106 ppm and a N content of 52 ppm.

[0092] Here, the chromium-rich layer in the third type of return material is significantly thicker and more complex in structure. Furthermore, the encapsulation between the nitride and alumina is difficult to disrupt, preventing the effective stripping of the nitride from the interdiffusion layer, resulting in incomplete oxygen and nitrogen removal. Compared with Comparative Example 3, the ultrasonic cavitation in Example 3 impacts the chromium-rich layer, promoting its shedding. It also increases the electrode potential of the electrolyte, accelerating the reaction, both of which contribute to the dissociation of the chromium-rich layer in this type of return material.

[0093] Comparative Example 4

[0094] Comparative Example 4 peels off the surface reaction layer of the third type high-temperature alloy return material. The difference from Example 3 is that the acid used in the electrolytic treatment in Comparative Example 4 is acetic acid, and the pH value of the electrolyte is 2.1.

[0095] The rest is the same as Example 3.

[0096] In Comparative Example 4, after replacing citric acid with acetic acid, the acidity and complexing ability of the electrolyte decreased, and the electrolysis effect was slightly reduced. After electrolysis, the surface layer of the third type high-temperature alloy return material in Comparative Example 4 had an O content of 42 ppm and a N content of 55 ppm.

[0097] Comparative Example 5

[0098] Comparative Example 5 peels off the surface reaction layer of the third type of high-temperature alloy return material. The difference from Example 3 is that:

[0099] The NaCl was replaced with sodium isethionate and a small amount of corrosion inhibitor sodium mercaptobenzothiazole was added. Other aspects were the same as in Example 3.

[0100] Here, the aqueous sodium hydroxyethyl sulfonate solution in Comparative Example 5 is alkaline, which reduces the acidity of the electrolyte. At the same time, the electrolyte loses the penetration effect of chloride ions on the chromium-rich layer, which reduces the stripping efficiency of the chromium-rich layer.

[0101] After electrolysis treatment, the surface layer of the third type high-temperature alloy return material of Comparative Example 5 has an O content of 38 ppm and a N content of 57 ppm.

[0102] In summary, the surface oxygen and nitrogen content of the high-temperature alloy return material after electrolytic treatment in the embodiment of the present invention is equivalent to that of the alloy core, and can be used for remelting and recycling. It can be seen that the method of the present invention has an excellent removal effect on the surface reaction layer (chromium-rich layer and interdiffusion layer) of high-temperature alloys of different grades and after different service conditions. However, the surface reaction layer of the high-temperature alloy return material after electrolytic treatment in Comparative Examples 1 to Comparative Examples 5 was not completely removed, and the oxygen and nitrogen content did not reach the core level, and could not be directly used for recycling. It can be seen that according to the type of high-temperature alloy return material, controlling the composition and parameters of the electrolytic treatment can significantly improve the removal effect and efficiency of the surface reaction layer.

[0103] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Any simple modifications, equivalent changes and modifications made to the above embodiment based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for stripping the surface reaction layer of high-temperature alloy return material, characterized in that: It includes the following steps: Electrolytic treatment step: using the high-temperature alloy return material as an anode and an inert material as a cathode; placing the anode and cathode in an electrolyte and performing electrolytic treatment to remove a surface reaction layer on the high-temperature alloy return material; wherein the electrolyte contains 1 to 3 mol / L of a chloride salt electrolyte additive and 0 to 2 mol / L of a weak acid.

2. The method for stripping the surface reaction layer of high-temperature alloy return material according to claim 1, characterized in that: When the high-temperature alloy return material is the first type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows: The electrode potential is 400-600 mV vs. SHE. The pH of the electrolyte is 2.5-7. The concentration of the weak acid in the electrolyte is 0-1 mol / L. The concentration of the chloride electrolyte additive is 1-1.5 mol / L. The current density of the electrolytic treatment is 0.45-0.8 A / cm 2 , the electrolysis treatment time is 20 to 30 minutes; Wherein, the thickness of the surface reaction layer of the first type high-temperature alloy return material is less than 20 μm.

3. The method for stripping the surface reaction layer of the high-temperature alloy return material according to claim 2, characterized in that: The surface reaction layer of the first type high temperature alloy return material comprises, from the outside to the inside, a chromium-rich layer and an interdiffusion layer; preferably, the thickness of the chromium-rich layer is 2 to 5 μm, and the thickness of the interdiffusion layer is 5 to 15 μm; preferably, the chromium-rich layer comprises Cr2O3, and preferably also comprises TiO2; the interdiffusion layer comprises TiO2 and Al2O3; and / or The first type of high temperature alloy return materials includes high temperature alloy return materials after being served at a temperature below 800°C.

4. The method for stripping the surface reaction layer of high-temperature alloy return material according to claim 1, characterized in that: When the high-temperature alloy return material is the second type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows: The electrode potential is 600-800 mV vs. SHE. The pH of the electrolyte is 2-2.

5. The concentration of the weak acid in the electrolyte is 1-1.5 mol / L. The concentration of the chloride electrolyte additive is 1.5-2 mol / L. The current density of the electrolytic treatment is 0.65-0.8 A / cm 2 , the electrolysis treatment time is 30 to 40 minutes; Wherein, the thickness of the surface reaction layer of the second type high-temperature alloy return material is 20 to 60 μm.

5. The method for stripping the surface reaction layer of high-temperature alloy return material according to claim 4, characterized in that: The surface reaction layer of the second type high temperature alloy return material includes a chromium-rich layer and an interdiffusion layer from the outside to the inside; preferably, the thickness of the chromium-rich layer is 8 to 20 μm, and the thickness of the interdiffusion layer is 25 to 50 μm; preferably, the chromium-rich layer includes Cr2O3, TiO2, and Al2O3; the interdiffusion layer includes TiO2, Al2O3, NiCr2O4, and TiN; and / or The second type of high-temperature alloy return materials includes high-temperature alloy smelting and / or processing waste.

6. The method for stripping the surface reaction layer of high-temperature alloy return material according to claim 1, characterized in that: When the high-temperature alloy return material is the third type of high-temperature alloy return material, the parameters of the electrolysis treatment are controlled as follows: The electrode potential is 1000-1500 mV vs. SHE. The pH of the electrolyte is 1.5-2. The concentration of the weak acid in the electrolyte is 1.5-2 mol / L. The concentration of the chloride electrolyte additive is 2-3 mol / L. The current density of the electrolytic treatment is 0.8-1 A / cm 2 , after electrolysis for 20 to 25 minutes, ultrasonication is performed and electrolysis is continued for 20 to 25 minutes; preferably, the power of the ultrasound is 300 to 500W; Wherein, the thickness of the surface reaction layer of the third type high-temperature alloy return material is 100-250 μm.

7. The method for stripping the surface reaction layer of high-temperature alloy return material according to claim 6, characterized in that: The surface reaction layer of the third type high temperature alloy return material includes a chromium-rich layer and an interdiffusion layer from the outside to the inside; preferably, the thickness of the chromium-rich layer is 15 to 50 μm, and the thickness of the interdiffusion layer is 80 to 200 μm; preferably, the chromium-rich layer includes Cr2O3, TiO2 and TiN; the interdiffusion layer includes NiCr2O4 spinel, Al2O3, TiO2, and TiN wrapped Al2O3; and / or The third type of high-temperature alloy return material includes high-temperature alloy return material after service at a temperature not lower than 800°C.

8. The method for stripping the surface reaction layer of high-temperature alloy return material according to any one of claims 1 to 7, characterized in that: Before the electrolytic treatment step, the method further comprises: Classification step: classifying the high-temperature alloy return material according to the type of the reaction layer on the high-temperature alloy return material, and dividing the high-temperature alloy return material into different types; Wherein, in the electrolytic treatment step, the parameters of the electrolytic treatment are controlled according to the type of the high-temperature alloy return material; Preferably, in the classification step, the high-temperature alloy return material is classified into a first type of high-temperature alloy return material, a second type of high-temperature alloy return material, and a third type of high-temperature alloy return material.

9. The method for stripping the surface reaction layer of high-temperature alloy return material according to any one of claims 1 to 8, characterized in that: In the step of electrolytic treatment: The weak acid includes one or more of citric acid, acetic acid, malic acid, oxalic acid, ethylenediaminetetraacetic acid, and tartaric acid; preferably, when the high-temperature alloy return material is a first-type high-temperature alloy return material, the weak acid is acetic acid; when the high-temperature alloy return material is a second-type high-temperature alloy return material, the weak acid is malic acid; when the high-temperature alloy return material is a third-type high-temperature alloy return material, the weak acid is citric acid; and / or The chloride electrolyte additive includes sodium chloride and / or potassium chloride; and / or The distance between the anode and cathode is 10 to 30 cm; and / or The cathode is made of graphite; and / or The mass ratio of the electrolyte to the high-temperature alloy return material is (5-30):

1.

10. A high-temperature alloy return material after stripping the surface reaction layer, characterized in that: The method for stripping the surface reaction layer of the high-temperature alloy return material according to any one of claims 1 to 9 is used to treat the high-temperature alloy return material to obtain the high-temperature alloy return material after the surface reaction layer is stripped; Preferably, the oxygen content in the surface layer of the high-temperature alloy return material after stripping the surface reaction layer is within 5 ppm of the oxygen content in the alloy matrix; Preferably, the nitrogen content in the surface layer of the high-temperature alloy return material after stripping the surface reaction layer differs from the nitrogen content in the alloy matrix by within 5 ppm.

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