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 invention relates to the technical field of metal material clean recovery 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 have high high-temperature strength, good oxidation and corrosion resistance, good fatigue performance and fracture toughness. They are widely used in important parts such as aerospace engines and are known as the jewel in the crown of industry. In recent years, the annual output of high-temperature alloys has reached 50,000 tons. Due to the low utilization rate, the amount of returned materials is also increasing year by year.

[0003] The returned materials mainly include waste materials generated during smelting and processing, as well as scrapped materials from service, etc. 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 nature and closely bonded to the alloy matrix.

[0004] The main method for recycling the return material is pyrometallurgical remelting. However, the reaction layer in the return material contains a large amount of oxygen and nitrogen gas impurity elements, which are easy to produce slag during the smelting process and form refractory inclusions with alloy 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 material and recycle it for reuse, which is conducive to reducing the consumption of strategic metal resources, reducing environmental pollution, and reducing the production cost of aircraft engines. At present, the removal methods of 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 performs shot blasting and grinding treatments in turn, and finally uses hydrochloric acid and nitric acid solutions for pickling to obtain a clean return material surface. The second related technology discloses a method for treating 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 oxide layers from 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 are mainly pickling combined with mechanical methods such as shot blasting and grinding. However, the pickling method requires a specific pickling device, the process is complicated, the cost is high, and the efficiency is low; pickling uses hydrochloric acid, nitric acid, hydrofluoric acid, hexamethylenetetramine and other volatile chemicals with pungent odor, flammable and highly corrosive, which have a high risk factor and are not friendly to the environment. In addition, mechanical methods such as shot blasting and grinding have the risk of causing secondary pollution during operation.

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

[0007] In view of this, the present invention provides a method for stripping the surface reaction layer of superalloy return materials, and the main purpose is to solve the problems of low efficiency and environmental unfriendliness existing in the existing methods for removing the surface reaction layer of superalloy return materials.

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

[0009] On the one hand, a method for stripping the surface reaction layer of superalloy return materials, which comprises the following steps:

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

[0011] Preferably, when the superalloy return material is a first - type superalloy 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 salt electrolyte additive is 1 - 1.5 mol / L, the current density of the electrolysis treatment is 0.45 - 0.8 A / cm 2 , and the electrolysis treatment time is 20 - 30 min;

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

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

[0015] Preferably, when the superalloy return material is a second - type superalloy 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 salt 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 electrolytic treatment time is 30 - 40 min;

[0017] Among them, the thickness of the surface reaction layer of the second type of superalloy return material is 20 - 60 μm.

[0018] Preferably, the surface reaction layer of the second type of superalloy return material includes a chromium-rich layer and an interdiffusion layer in sequence from the outside to the inside; preferably, the thickness of the chromium-rich layer is 8 - 20 μm, and the thickness of the interdiffusion layer is 25 - 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 superalloy return material includes superalloy smelting and / or processing waste.

[0019] Preferably, when the superalloy return material is the third type of superalloy return material, the parameters of the electrolytic 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 salt electrolyte additive is 2 - 3 mol / L, and the current density of the electrolytic treatment is 0.8 - 1 A / cm 2 ; after electrolytic treatment for 20 - 25 min, ultrasonic treatment is carried out and electrolysis is continued for 20 - 25 min; preferably, the power of the ultrasonic treatment is 300 - 500 W;

[0021] Among them, the thickness of the surface reaction layer of the third type of superalloy return material is 100 - 250 μm.

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

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

[0024] Preferably, before the electrolysis treatment step, the method further includes:

[0025] Classification step: Classify the superalloy return materials according to the type of reaction layer on the superalloy return materials, and divide the superalloy return materials into different categories;

[0026] Wherein, in the electrolysis treatment step, according to the category to which the superalloy return material belongs, control the parameters of the electrolysis treatment;

[0027] Preferably, in the classification step: the superalloy return materials are divided into the first-class superalloy return materials, the second-class superalloy return materials, and the third-class superalloy return materials.

[0028] Preferably, in the electrolysis treatment step:

[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 superalloy return material is the first-class superalloy return material, acetic acid is selected as the weak acid; when the superalloy return material is the second-class superalloy return material, malic acid is selected as the weak acid; when the superalloy return material is the third-class superalloy return material, citric acid is selected as the weak acid; and / or

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

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

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

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

[0034] On the other hand, an embodiment of the present invention provides a superalloy return material after stripping the surface reaction layer. Among them, after the superalloy return material is processed by using the method for stripping the surface reaction layer of the superalloy return material described in any one of the above, a superalloy return material after stripping the surface reaction layer is obtained; preferably, the difference in oxygen content between the surface layer of the superalloy return material after stripping the surface reaction layer and the oxygen content of the alloy matrix is within 5 ppm; preferably, the difference in nitrogen content between the surface layer of the superalloy return material after stripping the surface reaction layer and the nitrogen content of the alloy matrix is within 5 ppm.

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

[0036] An embodiment of the present invention provides a method for stripping the reaction layer on the surface of a superalloy return material. The superalloy return material is used as the anode and an inert material is used as the cathode. The anode and the cathode are placed in an electrolyte for electrolytic treatment to remove the reaction layer on the superalloy return material. Wherein, the electrolyte contains 1-3 mol / L of a chloride electrolyte additive and 0-2 mol / L of a weak acid. It should be noted here that: the electrolyte of the present invention contains Cl with a small ionic radius and strong penetration ability - , which can adsorb 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 using strong corrosive and volatile-smelling strong acids such as hydrochloric acid, nitric acid, and hydrofluoric acid, as well as flammable and sensitizing substances such as hexamethylenetetramine, and no toxic gases such as NO and Cl2 are generated during the operation process, no temperature control is required, and no violent reactions such as splashing occur during the experimental process, 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, has no special device requirements, no site requirements, saves production costs, and improves efficiency. After electrolytic treatment, there are no nitride and oxide residues on the surface of the superalloy return material, the whole is bright and clean, and the oxygen and nitrogen contents are effectively controlled, reaching the oxygen and nitrogen content levels of the alloy core, providing conditions for the next clean remelting and smelting of the return material.

[0037] Further, an embodiment of the present invention provides a method for stripping the reaction layer on the surface of a superalloy return material. For the first type of superalloy return material (the superalloy return material after serving at a lower temperature, the thickness of the surface reaction layer is less than 20 μm), the electrolyte is selected as a single chloride solution (the concentration of the chloride electrolyte additive is 1-1.5 mol / L) or an appropriate amount of acetic acid is added to enhance the acidity, and the electrode potential of the electrolyte is maintained at 400-600 mV vs. SHE, which is higher than the standard electrode potentials of the main metal elements Cr, Ti, Al, Ni, etc. in the reaction layer, facilitating the progress of the dissolution reaction. The applied electric field can accelerate the diffusion and migration rate of ions, and at the same time can ionize hydroxyl radicals in the solution: H2O → ·OH + H + +e - , enhancing the acidity while increasing the electrode potential of the system and improving the dissolution rate of the surface reaction layer. Under the combined action of the above acidic environment, Cl - and the electric field, the stability of Cr2O3, NiO, TiO2, etc. in the reaction is significantly reduced, and their occurrence states change to form loose and soluble chlorides and chlorine coordination compounds and dissociate.

[0038] Furthermore, an embodiment of the present invention provides a method for stripping the surface reaction layer of superalloy return materials. For the second type of superalloy return materials (smelting and / or processing waste of superalloys, the thickness of the surface reaction layer is 20 - 60 μm), malic acid is preferably used as the electrolyte, and the concentration of the chloride salt electrolyte additive in the electrolyte solution is controlled to be 1.5 - 2 mol / L, so that the electrode potential is maintained at 600 - 800 mV vs. SHE. It should be noted that during the electrolysis process, aluminum and chromium will form a passivation layer to hinder electrolysis. Malate ions can complex with them to form soluble substances, promoting electrolysis and contributing to the dissolution of thicker reaction layers containing Cr2O3, TiO2, etc. in such return materials. Specifically, malic acid, as a dibasic acid, has strong acidity and a complexing effect of forming soluble substances with metal ions; the chloride salt electrolyte additive with a concentration of 1.5 - 2 mol / L can increase the conductivity of the solution and enhance the penetration of chloride ions into the chromium-rich layer, and the electrode potential of 600 - 800 mV vs. SHE increases the oxidizing property of the solution. Here, malic acid, the electrolyte additive with a concentration of 1.5 - 2 mol / L, and the electrode potential maintained at 600 - 800 mV vs. SHE work together synergistically to promote the electrolysis reaction and the dissolution of thicker reaction layers containing Cr2O3, TiO2, etc.

[0039] Furthermore, an embodiment of the present invention provides a method for stripping the surface reaction layer of superalloy return materials. For the third type of superalloy return materials (superalloy return materials after service at higher temperatures, with the thickness of the surface reaction layer being 100 - 250 μm), the thickness increases significantly and a structurally stable TiN-coated Al2O3 is likely to form in the internal diffusion layer. Here, citric acid is used as the electrolyte, while the chloride salt electrolyte additive is controlled at 2 - 3 mol / L, and an ultrasonic field is added. As a ternary acid, citric acid exhibits stronger acidity under the action of an electric field, and its more hydroxyl carboxylic acid group ligand structures endow it with stronger complexing ability; at the same time, hydroxyl and carboxyl groups, as hydrophilic groups, give it stronger wettability, reducing the surface tension of the electrolyte solution and the contact angle between the droplet and the surface of the return material, inhibiting the adsorption of anode products on the surface, and all promoting the dissociation of more complex chromium-rich layers of such return materials. Based on the synergy of the 2 - 3 mol / L chloride salt electrolyte additive and the electrode potential of 1000 - 1500 mV vs. SHE., the huge heat and pressure generated by the ultrasonic field can accelerate the dissolution of the chromium-rich layer with chromium oxide as the core on the surface layer. Meanwhile, its cavitation effect generates more hydroxyl radicals in the electrolyte, which are all beneficial to the leaching of metal elements. For the compounds in the internal diffusion layer (such as TiN-coated Al2O3), they are more stable than the alloy matrix and are not easily involved in the dissolution process. During electrolysis, they tend to be preferentially selectively dissolved with respect to the matrix, creating voids between Al2O3 and TiN. Ultrasonic waves generate strong impact forces at the liquid-solid interface, destroying the solid film layer at the contact 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 be able to understand the technical means of the present invention more clearly and implement it in accordance with the content of the specification, the following describes in detail with reference to the preferred embodiments of the present invention and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 FIG. is a SEM cross-sectional view of the surface layer of the first type of superalloy return material before and after electrolytic treatment in Example 1. Among them, Figure 1 FIG. (a) is a SEM cross-sectional view of the surface layer (reaction layer) of the first type of superalloy return material in this embodiment before electrolytic treatment; Figure 1 FIG. (b) is a SEM cross-sectional view of the surface layer of the first type of superalloy return material in this embodiment after electrolytic treatment;

[0042] Figure 2 FIG. is a SEM cross-sectional view of the surface layer of the second type of superalloy return material before and after electrolytic treatment in Example 2. Among them, Figure 2 FIG. (a) is a SEM cross-sectional view of the surface layer (reaction layer) of the second type of superalloy return material in this embodiment before electrolytic 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 returned material before and after electrolytic treatment. DETAILED DESCRIPTION

[0045] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[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, the relevant 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 surface reaction layer (chromium-rich layer and interdiffusion layer) of the high-temperature alloy is removed by electrolysis, which does not require a site or special equipment. The overall process steps are streamlined, more efficient, and avoids the risk of secondary pollution during operation. In addition, the present invention uses a weak acid electrolysis method, which avoids 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, which is more environmentally friendly and safer; the cleanliness is significantly improved after electrolysis, meeting the requirements of remelting and smelting.

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

[0049] The 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 superalloy return material as the anode and an inert material as the cathode; placing the anode and cathode in an electrolyte for electrolytic treatment to remove the surface reaction layer on the superalloy return material; wherein, the electrolyte contains 1-3 mol / L of a chloride salt electrolyte additive and 0-2 mol / L of a weak acid.

[0051] Among them, in the electrolytic treatment step, according to the type of the superalloy return material, the parameters of the electrolytic treatment are controlled.

[0052] According to the type and structure of the reaction layer of the superalloy return material, it is mainly divided into three categories. The first category is the return material with a relatively simple reaction layer structure formed during service at a lower temperature (below 800 °C). Its surface reaction layer from the outside to the inside sequentially includes a chromium-rich layer and an interdiffusion layer; wherein, the chromium-rich layer includes Cr2O3, and preferably also includes TiO2; the interdiffusion layer includes TiO2 and Al2O3, and the overall thickness of the surface reaction layer is within 20 μm. The second category is mainly the waste materials from superalloy smelting and processing. The surface reaction layer of this type of return material from the outside to the inside sequentially includes a chromium-rich layer and an interdiffusion layer; wherein, the chromium-rich layer includes Cr2O3, TiO2, and Al2O3; the interdiffusion layer includes TiO2, Al2O3, NiCr2O4, and TiN, and the thickness of the surface reaction layer is about 20-60 μm. The third category is the return material with a complex chromium-rich layer structure formed during service at a higher temperature (not lower than 800 °C). Its surface reaction layer from the outside to the inside sequentially includes a chromium-rich layer and an interdiffusion layer; wherein, the chromium-rich layer includes Cr2O3, TiO2, and TiN; the interdiffusion layer includes NiCr2O4, Al2O3, TiO2, and Al2O3 wrapped by TiN, and the thickness of its reaction layer is about 100-250 μm.

[0053] Among them, when the superalloy return material is the first type of superalloy return material, the parameters of the electrolytic treatment are controlled as follows: the electrode potential is 400-600 mV vs. SHE. (Here, vs. SHE. means the reference hydrogen standard electrode. For the reference hydrogen standard electrode, the electrode potential is 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 salt electrolyte additive is 1-1.5 mol / L, and the current density of the electrolytic treatment is 0.45-0.8 A / cm 2 and the time of the electrolytic treatment is 20-30 min.

[0054] Among them, when the superalloy return material is the second type of superalloy return material, the parameter control of the electrolytic treatment is 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 salt 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 electrolytic treatment time is 30 - 40 min.

[0055] Among them, when the superalloy return material is the third type of superalloy return material, the parameter control of the electrolytic treatment is 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 salt electrolyte additive is 2 - 3 mol / L, and the current density of the electrolytic treatment is 0.8 - 1 A / cm 2 ; after electrolytic treatment for 20 - 25 min, ultrasonic treatment is carried out and electrolysis continues for 20 - 25 min; preferably, the power of the ultrasonic treatment is 300 - 500 W.

[0056] In addition, it should be noted that: (1) For the preparation of the electrolytic sample (anode), the embodiments of the present invention are applicable to superalloy return materials with various shapes and sizes, and no prior physical or chemical treatment is required. (2) The weak acid includes citric acid, glacial acetic acid, malic acid, oxalic acid, ethylenediaminetetraacetic acid, tartaric acid, etc. (3) The chloride salt electrolyte additive is used to improve the conductivity and electrolysis efficiency of the electrolyte, such as sodium chloride, potassium chloride, etc., but not limited thereto. (3) The electrolysis is carried out at room temperature, the anode is the superalloy return material, the cathode is graphite, the anode and cathode are placed in the above electrolyte and the distance between the two is fixed at 10 - 30 cm, and electrolysis is carried out with a constant current. (4) The mass ratio of the electrolyte to the superalloy return material is (5 - 30):1.

[0057] In addition, the electrolysis is carried out in an electrolytic cell, and well-known acid-resistant non-conductive materials can be used, including quartz glass, polytetrafluoroethylene, polyethylene, polypropylene, polyester, etc. After electrolysis, the sample is rinsed and dried with deionized water and alcohol in sequence.

[0058] Among them, Figure 4 are the SEM pictures and element distributions of the second type of return material before and after electrolytic treatment. From Figure 4 it can be seen that: the method of the embodiments of the present invention can effectively strip the reaction layer (chromium-rich layer and interdiffusion layer) in the superalloy return material. The main element components such as Ni and Co in the matrix after electrolysis are equivalent to those in the alloy core, the contents of Cr, Al, Ti, and O are significantly reduced, and the cleanliness of the return material is significantly improved, meeting the requirements of remelting and smelting.

[0059] The present invention will be further described below with specific embodiments:

[0060] Example 1

[0061] In this example, the surface reaction layer (oxygen content: 300 ppm, nitrogen content: 36 ppm) of the first type of superalloy return material was stripped. The main steps are as follows:

[0062] The first type of superalloy return material that had served at a temperature below 800 °C for 1000 h was processed into a bar sample of 0.4×0.4×3 cm 3 by wire cutting, and the cutting surface and both ends were polished brightly with sandpaper, then rinsed thoroughly with deionized water and anhydrous ethanol, and dried.

[0063] 100 mL of a mixed solution of acetic acid and sodium chloride was prepared with deionized water as the electrolyte. Among them, the concentration of acetic acid was 1 mol / L, and the concentration of sodium chloride was 1 mol / L. The anode was the superalloy bar prepared as described above, and the cathode was graphite. The cathode and anode were placed in the above electrolyte, and the distance between the two was fixed at 10 cm. Constant current electrolysis treatment was carried out, with the electrode potential of 500 mV vs. SHE, the current density of electrolysis treatment of 0.6 A / cm 2 , the pH value of the electrolyte of 2.5, and the electrolysis treatment time of 30 min.

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

[0065] After the electrolysis treatment of the first type of superalloy return material in this example, the O content in its surface layer was 4 ppm, the N content was 33 ppm, and the oxygen content removal rate was 98.7%, which was close to the oxygen content and nitrogen content of the alloy matrix.

[0066] Example 2

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

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

[0069] Use deionized water to prepare a mixed solution of malic acid and sodium chloride (100 mL) as the electrolyte. The concentration of malic acid is 1.5 mol / L, and the concentration of sodium chloride is 2 mol / L. The anode is a high-temperature alloy strip prepared in the above manner, and the cathode is graphite. The cathode and the 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 800 mV vs. SHE., and the current density of the electrolysis treatment is 0.65 A / cm 2 , the pH of the electrolyte is 2 and the electrolysis treatment time is 40 minutes.

[0070] The surface cross-sectional 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 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 high temperature alloy return material after electrolysis treatment in this embodiment. Figure 2 It can be clearly seen that before the electrolytic treatment, the thickness of the reaction layer of the second type high temperature alloy return material is 44μm, of which the thickness of the chromium-rich layer is 15μm, and the composition is Cr2O3, TiO2, Al2O3; the thickness of the interdiffusion layer is 29μm, and the composition is TiO2, Al2O3, NiCr2O4, TiN. After the treatment of this embodiment, the reaction layer is obviously 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 19ppm, a N content of 45ppm, and an oxygen content 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 600ppm and nitrogen content of 87ppm) of the third type high temperature alloy return material is stripped, and the main steps are as follows:

[0074] The third-class superalloy return materials that have served at 1200 °C for 200 h are processed into bar samples with dimensions of 0.4×0.4×3 cm by wire cutting. 3 The cutting surfaces and both ends are polished with sandpaper until shiny, then rinsed thoroughly with deionized water and absolute ethanol, and dried.

[0075] Prepare 100 mL of a mixed solution of citric acid and sodium chloride using deionized water as the electrolyte. Among them, the concentration of citric acid is 2 mol / L, and the concentration of sodium chloride is 2 mol / L. The anode is the superalloy bar prepared as described above, and the cathode is graphite. Place the cathode and anode in the above electrolyte and fix the distance between the two at 10 cm. Conduct constant-current electrolysis treatment with an electrode potential of 1000 mV vs. SHE and an electrolysis current density of 0.8 A / cm 2 , and the pH value of the electrolyte is 1.5. After preliminary electrolysis for 20 min, ultrasonic treatment is added and electrolysis is continued for another 20 min, with an ultrasonic power of 400 W.

[0076] The SEM cross-sectional images of the surface layer of the third-class superalloy return materials before and after electrolysis treatment in this example are as Figure 3 shown, where Figure 3 Figure (a) in Figure 3 is the SEM cross-sectional image of the surface layer (reaction layer) of the third-class superalloy return materials before electrolysis treatment in this example; Figure 3 Figure (b) in

[0077] is the SEM cross-sectional image of the surface layer of the third-class superalloy return materials after electrolysis treatment in this example. It can be clearly seen from

[0078] Comparative Example 1

[0079] In Comparative Example 1, the surface reaction layer of the first-class superalloy return materials is peeled off. 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] Other conditions are the same as those in Example 1.

[0081] Here, since the concentration of sodium chloride was reduced in Comparative Example 1, the resistance value of the electrolyte increased, and at the same time, the penetration effect of chloride ions on the chromium-rich layer was weakened, resulting in a reduction in the electrolysis effect.

[0082] After electrolytic treatment of the first type of superalloy return material in Comparative Example 1, in its surface layer: the O content was 59 ppm and the N content was 38 ppm; obviously, the oxygen element content was still excessive and the removal was incomplete.

[0083] Comparative Example 2

[0084] In Comparative Example 2, the surface reaction layer of the second type of superalloy return material was peeled off. The difference from Example 2 was that: the concentration of malic acid was 0.2 mol / L and the pH value of the electrolyte was 2.6.

[0085] Others were the same as in Example 2.

[0086] Here, since the concentration of malic acid in the electrolyte was reduced in Comparative Example 2, the acidity and conductivity of the electrolyte decreased, and at the same time, the complexing effect of malate ions was weakened, resulting in a reduction in the electrolysis effect.

[0087] After electrolytic treatment of the second type of superalloy return material in Comparative Example 2, in its surface layer, the O content was 54 ppm and the N content was 48 ppm.

[0088] Comparative Example 3

[0089] In Comparative Example 3, the surface reaction layer of the third type of superalloy return material was peeled off. The difference from Example 3 was that: the electrolytic treatment time in Comparative Example 3 was 40 min, but ultrasound was not added during the electrolysis process.

[0090] Others were the same as in Example 3.

[0091] After electrolytic treatment of the third type of superalloy return material in Comparative Example 3, in its surface layer, the O content was 106 ppm and the N content was 52 ppm.

[0092] Here, the thickness of the chromium-rich layer of the third type of return material increased significantly and the structure was complex, and the wrapping relationship between the nitride and alumina was difficult to break, and the nitride in the interdiffusion layer could not be effectively peeled off, resulting in incomplete removal of oxygen and nitrogen. Compared with Comparative Example 3, the ultrasonic cavitation effect in Example 3 would impact the chromium-rich layer to promote its detachment, and at the same time, it could increase the electrode potential of the electrolyte and promote the progress of the reaction, both of which were helpful for the dissociation of the chromium-rich layer of this type of return material.

[0093] Comparative Example 4

[0094] For Comparative Example 4, the surface reaction layer of the third type of superalloy return material was stripped. The difference from Example 3 is that: in Comparative Example 4, acetic acid was selected as the acid used in the electrolytic treatment, and the pH value of the electrolyte was 2.1.

[0095] Others were the same as in Example 3.

[0096] After replacing citric acid with acetic acid in Comparative Example 4, the acidity and complexing ability of the electrolyte decreased, and the electrolytic effect decreased slightly. After electrolytic treatment of the third type of superalloy return material in Comparative Example 4, in its surface layer, the O content was 42 ppm and the N content was 55 ppm.

[0097] Comparative Example 5

[0098] For Comparative Example 5, the surface reaction layer of the third type of superalloy return material was stripped. The difference from Example 3 is that:

[0099] NaCl was replaced with sodium hydroxyethyl sulfonate and a small amount of corrosion inhibitor sodium mercaptobenzothiazole was added. Others were the same as in Example 3.

[0100] Here, the aqueous solution of sodium hydroxyethyl sulfonate in Comparative Example 5 was alkaline, which reduced the acidity of the electrolyte. At the same time, this electrolyte lost the penetration effect of chloride ions on the chromium-rich layer, resulting in a reduction in the stripping efficiency of the chromium-rich layer.

[0101] After electrolytic treatment of the third type of superalloy return material in Comparative Example 5, in its surface layer: the O content was 38 ppm and the N content was 57 ppm.

[0102] In summary, the oxygen and nitrogen contents in the surface layer of the superalloy return material after electrolytic treatment in the embodiments of the present invention are equivalent to those in the alloy core and can be used for remelting and recycling. It can be seen that the method of the present invention has excellent removal effects on the surface reaction layers (chromium-rich layer and interdiffusion layer) of superalloys with different grades and under different service conditions. However, the surface reaction layers of the superalloy return materials after electrolytic treatment in Comparative Examples 1-5 were not completely removed, and the oxygen and nitrogen contents did not reach the core level and could not be directly used for recycling treatment. It can be seen that by controlling the composition and parameters of the electrolytic treatment according to the type of superalloy return material, the removal effect and efficiency of the surface reaction layer can be significantly improved.

[0103] The above are only preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments 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 reaction layer on the surface of a superalloy return material, characterized in that, It includes the following steps: Electrolytic treatment step: using the superalloy return material as the anode and an inert material as the cathode; placing the anode and cathode in an electrolyte for electrolytic treatment to remove the surface reaction layer on the superalloy return material; wherein, the electrolyte contains 1 - 3 mol / L of a chloride salt electrolyte additive and 0 - 2 mol / L of a weak acid.

2. The method for peeling the surface reaction layer of the superalloy return material according to claim 1, characterized in that, When the superalloy return material is a first - type superalloy return material, the parameters of the electrolytic 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 salt electrolyte additive is 1 - 1.5 mol / L, and the current density of the electrolytic treatment is 0.45 - 0.8 A / cm 2 , and the time of the electrolytic treatment is 20 - 30 min; Among them, the thickness of the surface reaction layer of the first - type superalloy return material is less than 20 μm.

3. The method for peeling the surface reaction layer of the superalloy return material according to claim 2, characterized in that The surface reaction layer of the first - type superalloy return material includes a chromium - rich layer and an interdiffusion layer in sequence from the outside to the inside; preferably, the thickness of the chromium - rich layer is 2 - 5 μm, and the thickness of the interdiffusion layer is 5 - 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 superalloy return material includes superalloy return materials after service at a temperature below 800°C.

4. The method for peeling the surface reaction layer of the superalloy return material according to claim 1, wherein When the superalloy return material is a second - type superalloy 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 salt electrolyte additive is 1.5 - 2 mol / L, and the current density of the electrolytic treatment is 0.65 - 0.8 A / cm 2 , and the time of the electrolytic treatment is 30 - 40 min; Among them, the thickness of the surface reaction layer of the second - type superalloy return material is 20 - 60 μm.

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

6. The method for peeling the surface reaction layer of the superalloy return material according to claim 1, characterized in that, When the superalloy return material is a third - type superalloy 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 salt electrolyte additive is 2 - 3 mol / L, and the current density of the electrolytic treatment is 0.8 - 1 A / cm 2 , after electrolytic treatment for 20 - 25 min, ultrasonic treatment is carried out and electrolysis is continued for 20 - 25 min; preferably, the power of the ultrasonic treatment is 300 - 500 W; Among them, the thickness of the surface reaction layer of the third - type superalloy return material is 100 - 250 μm.

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

8. The method for peeling the surface reaction layer of the superalloy return material according to any one of claims 1-7, characterized in that, Before the electrolytic treatment step, it further includes: Classification step: classifying the superalloy return materials according to the type of the reaction layer on the superalloy return materials, and dividing the superalloy return materials into different categories; Among them, in the electrolytic treatment step, the parameters of the electrolytic treatment are controlled according to the category to which the superalloy return material belongs. Preferably, in the classification step: the superalloy return materials are divided into the first-class superalloy return materials, the second-class superalloy return materials, and the third-class superalloy return materials.

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

1.

10. A superalloy return material after stripping the surface reaction layer, characterized in that, Using the method for stripping the surface reaction layer of the superalloy return material according to any one of claims 1 - 9 to process the superalloy return material, the superalloy return material after stripping the surface reaction layer is obtained; Preferably, the difference in oxygen content between the surface layer of the superalloy return material after stripping the surface reaction layer and the oxygen content of the alloy matrix is within 5 ppm; Preferably, the difference in nitrogen content between the surface layer of the superalloy return material after stripping the surface reaction layer and the nitrogen content of the alloy matrix is within 5 ppm.

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