A flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces and its preparation method

Abstract

This invention relates to a flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces and its preparation method, belonging to the field of material surface treatment technology. The invention provides a hot-dip titanium plating solution with a special Al-KBF4 composition and a specific pretreatment process for the solution composition. This process involves degreasing with potassium carbonate, immersing the workpiece in the solution at room temperature for rust removal and activation, followed by immersion plating in the hot-dip plating solution at high temperature and then cooling. The method provided by this invention greatly simplifies the pretreatment process, achieving a fluxing effect through the rust removal byproducts, and simultaneously obtaining a composite coating containing TiAl3, TiB2, and AlB2, which significantly improves hardness and wear resistance. This invention features a simple process, convenient operation, and uses inexpensive materials, requiring no large amounts of chemicals. While achieving a high-performance coating, it meets current green and environmentally friendly principles and is suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of material surface treatment technology, specifically relating to a flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces and its preparation method. Background Technology

[0002] Titanium and titanium alloys possess high specific strength, excellent corrosion resistance, and high-temperature heat resistance, earning them the title of "strategic metal for national defense" in the aerospace field. They are primarily used to manufacture structural components for aircraft engines, rockets, missiles, and high-speed aircraft, and also have broad application prospects in other fields, such as biology. However, the low hardness and poor wear resistance of titanium and titanium alloys reduce the reliability and safety of titanium alloy components, limiting their application in some areas. To address this deficiency, scholars from various countries have conducted in-depth research on surface modification technologies for titanium alloys.

[0003] Currently, the main technologies developed for surface modification of titanium alloys include electroplating, thermal diffusion, electroless plating, vapor deposition, ion implantation, and micro-arc oxidation. Although these technologies can improve the hardness and wear resistance of titanium alloys to some extent, their inherent limitations make them difficult to promote in industrial production. For example, during electroplating, an oxide film easily forms on the surface of the titanium alloy, placing extremely stringent requirements on the electroplating process; thermal diffusion has a long production cycle, and the thickness of the diffusion layer is difficult to control during the diffusion process; the surface pretreatment process of electroless plating has a significant impact on the coating, easily leading to a loose coating and failing to achieve the desired effect; the vapor deposition process involves high ambient temperatures, which can easily generate toxic gases; and the equipment required for ion implantation and micro-arc oxidation technologies is expensive.

[0004] Hot-dip galvanizing is an economical, effective, and simple surface treatment technology for metal materials, producing coatings that offer excellent corrosion resistance, wear resistance, and anti-corrosion properties. Compared to other surface treatment technologies, hot-dip galvanizing's main advantages are: thicker coatings and a dense, strong metallurgical bond between the coating and the substrate. Therefore, it is widely used in industrial production for surface modification of metals such as steel and titanium alloys. However, while hot-dip galvanizing technology for steel is mature, with a complete process flow from pretreatment to immersion and post-treatment, the composition of the plating solution for titanium and titanium alloys remains limited to aluminum-silicon or aluminum-zinc based solutions. Furthermore, in earlier fluxing processes, potassium fluorozirconate was the primary flux, resulting in higher costs.

[0005] Based on current research, the main pretreatment processes before hot-dip galvanizing are degreasing, rust removal, and fluxing, which are quite complicated. In addition, the aluminum-coated substrates obtained on the surface of titanium and titanium alloys, such as aluminum-silicon, are prone to voids in the diffusion layer, leading to cracks and reducing the wear resistance of the coating. Although adding rare earth elements can suppress the formation of voids and microcracks in the diffusion layer, the thickening of the alloy layer will undoubtedly affect the processing performance of the material. Summary of the Invention

[0006] To address the issues of low hardness and poor wear resistance of titanium and titanium alloys, as well as some problems with existing hot-dip aluminum plating of titanium and titanium alloys, this invention provides a flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces and its preparation method. This method provides a hot-dip titanium plating solution with a special Al-KBF4 composition and a specific pretreatment process for the solution composition. This involves degreasing with 60-100 g / L potassium carbonate, immersion in a 2-4% HF + 10-15% KCl alcohol solution at room temperature for rust removal and activation, followed by immersion in the hot-dip plating solution at 700-800°C for 10-30 minutes, and then cooling at a rate of 15-75°C / s. This method greatly simplifies the pretreatment process, achieves a fluxing effect through the products after rust removal, and simultaneously obtains a composite coating containing TiAl3, TiB2, and AlB2, resulting in significantly improved hardness and wear resistance. The present invention has a simple process, is easy to operate, and uses inexpensive materials. It does not require a large amount of chemicals and meets the current green and environmentally friendly concept while obtaining a coating with good performance, making it suitable for widespread application.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces, the composition of which is by mass percentage: potassium borofluoride (KBF4): 10%~20%, with the balance being Al and unavoidable impurities, wherein the impurity content does not exceed 0.01%.

[0009] A method for preparing a flux-free hot-dip aluminum-boron plating solution for titanium alloy surfaces, comprising adding the following ingredients:

[0010] (1) Weigh the metallic aluminum and potassium borofluoride according to the composition of the hot-dip aluminizing and boronizing solution;

[0011] (2) The aluminum metal is heated to 690~700℃ in the furnace until it is completely melted to obtain molten aluminum;

[0012] (3) Keep the furnace temperature at 650℃~660℃, add preheated potassium borofluoride wrapped in aluminum foil to the molten aluminum liquid, and press it to the bottom of the furnace with a graphite cover. Stir for 10~15 minutes until no bubbles are generated on the liquid surface to obtain a hot-dip aluminum-boron plating solution for titanium alloy surface without auxiliary plating.

[0013] The preheating parameters are: 40~60℃ for 10~15 minutes.

[0014] A method for hot-dip plating aluminum boron onto titanium alloys, using the aforementioned aluminum boron plating solution, comprises the following specific steps:

[0015] Step 1: Surface pretreatment of titanium alloy parts

[0016] (1) After degreasing, washing with water and draining the water, the titanium alloy plated parts are obtained after degreasing.

[0017] (2) Use hydrofluoric acid with a mass concentration of 2~5% and potassium chloride alcohol solution with a mass concentration of 10~15% to remove rust and activate the titanium plate after degreasing, remove the oxide film, and air dry at room temperature to obtain the pretreated titanium alloy plate.

[0018] Step 2: Hot-dip plating

[0019] (1) The pretreated titanium alloy plating part is vertically immersed in the aluminum-boron plating solution. The temperature of the plating solution is 700~800℃ and the immersion time is 10~30min. The part is then removed to obtain the plating part after immersion.

[0020] (2) After immersion plating, the plated part is left in the air for 10~30s, then cooled to room temperature with water. The cooling rate of the plating layer is controlled at 15~70℃ / s to obtain the hot-dip aluminum boron plated part.

[0021] In step 1(1), the degreasing agent used is potassium carbonate with a mass concentration of 60~100g / L;

[0022] In step 1(1), degreasing involves immersing the titanium alloy plated part in a degreasing solvent at room temperature for 5-10 minutes.

[0023] In step 1 (2), rust removal and activation are carried out simultaneously for 5 to 15 minutes.

[0024] In step 2(1), the titanium alloy plated part is vertically removed from the aluminum-boron plating solution, wherein the immersion rate and the removal rate are equal, preferably 0.05~0.15m / s.

[0025] In step 2(1), before removing the titanium-plated parts after immersion plating, a scraper is used to remove the oxide residue from the plating solution, exposing a clean and fresh liquid surface, so as to avoid oxide residue remaining on the surface of the plating parts, affecting the immersion plating effect, and causing problems such as missed plating.

[0026] In step 2(1), the temperature of the plating solution during the immersion plating process is different depending on the characteristics of the workpiece.

[0027] Using the above-mentioned method of hot-dip aluminum boron plating on the surface of titanium alloy, the surface wear rate of the hot-dip aluminum boron coated titanium alloy parts is 50% to 75% of that of the titanium alloy, and the surface wear resistance is greatly improved.

[0028] The hot-dip aluminum-boron plating solution for titanium alloys in this invention consists of pure aluminum and potassium borofluoride. Because boron has a high melting point, and the eutectic point of boron-aluminum compounds is also high, in-situ generated AlB2 is used to strengthen the wear resistance of the substrate surface. The reaction equation is as follows:

[0029] 2KBF4 + 3Al = AlB2 + 2KAlF4

[0030] The preparation method of the titanium hot-dip aluminum-boron plating solution of the present invention adopts a segmented heating mode, which can effectively improve the stability of the plating solution composition and avoid excessive decomposition of potassium borofluoride at too high a temperature, thereby reducing the content of hard phase in the matrix. Therefore, the temperature is first set at about 690~700℃ to melt pure aluminum, and then the furnace temperature is reduced to about 650~660℃. Potassium borofluoride wrapped in aluminum foil is added and pressed to the bottom of the furnace with a graphite cover. Stirring is carried out to allow it to react fully for 10min~15min. Then the temperature is raised to 700~800℃ to improve the fluidity of the melt and also increase the diffusion temperature, and then immersion plating is carried out.

[0031] In the method for hot-dip aluminum boron plating of titanium of the present invention, potassium carbonate is selected as the degreasing agent for the titanium alloy surface, which achieves the purpose of degreasing on the one hand, and retains the K on the surface on the other hand. + It will participate in the subsequent rust removal and activation processes, further improving the quality of the pretreatment of the plated parts.

[0032] In the method for hot-dip aluminum boron plating of titanium of the present invention, during the pretreatment of the titanium alloy surface, potassium fluorotitanate generated in situ on the surface of the titanium alloy substrate during rust removal can achieve the effect of fluxing the plating process. The principle is as follows:

[0033] TiO2 + HF = H2TiF6 + H2O

[0034] H2TiF6 + K + —— K2TiF6 (alcohol solution)

[0035] The potassium fluorotitanate produced in the reaction effectively protects the substrate surface, preventing further oxidation. During immersion plating, the potassium fluorotitanate undergoes an aluminothermic reaction with pure aluminum, instantly generating a large amount of heat and causing micro-explosions. This causes it to detach from the substrate surface, activating the surface of the workpiece. This reduces the surface tension of the titanium substrate, enhances the wetting effect between the titanium substrate and the low-temperature hot-dip galvanizing solution, promotes the diffusion reaction between the workpiece and the solution, and facilitates better coating of the workpiece with the solution, preventing incomplete plating. The principle is as follows:

[0036] 3K2TiF6 +13Al =3TiAl3+ 3KAlF4 + K3AlF6

[0037] In the method for hot-dip aluminum boron plating of titanium alloy provided by the present invention, the activated workpiece is dried in order to remove moisture from the workpiece and avoid phenomena such as liquid bursting during the immersion plating process, which would affect the quality of the plating layer.

[0038] The method for hot-dip aluminum-boron plating of titanium alloys provided by this invention uses a hot-dip plating solution with a temperature maintained at 700-800℃, good fluidity, and a glossy surface. The immersion time is 10-30 minutes, which can efficiently complete the immersion plating experiment of titanium alloys and greatly improve the process efficiency.

[0039] In the method of hot-dip aluminum boron plating on titanium alloy of the present invention, the pretreated titanium alloy workpiece is immersed in the plating solution at a 90° angle to the surface of the plating solution, which reduces the oxide film adhering to the workpiece on the surface of the plating solution, thereby enhancing the diffusion reaction between the workpiece and the plating solution and improving the bonding strength between the workpiece and the plating layer.

[0040] In the method of hot-dip aluminum-boron plating on titanium alloy of the present invention, after the titanium alloy part is taken out of the plating solution after immersion plating, it is kept in the air for 10 to 30 seconds and then water-cooled. By controlling the cooling rate of the coating at 15 to 70°C / s, the growth process of the coating is controlled. A larger cooling rate can refine the grain structure of the Al-AlB2 coating, and the resulting phase structure is dense and uniformly distributed, which greatly improves the wear resistance of the coating and avoids the coating from not being fully bonded due to a large cooling rate.

[0041] Compared with the prior art, the features and beneficial effects of the present invention are as follows:

[0042] (1) The plating solution used in this invention consists of pure aluminum and potassium borofluoride, and the raw material cost is low.

[0043] (2) Under the simple hot-dip galvanizing process of the present invention, hard phase AlB2 is obtained by in-situ generation, which greatly saves production costs compared with other processes.

[0044] (3) This invention eliminates the plating process by using potassium fluorotitanate, the product after rust removal, as a plating flux. In addition, during immersion plating, an aluminothermic reaction occurs, generating a large amount of heat, which improves the diffusion of elements and generates trace amounts of TiAl3. Compared with other plating processes, this invention not only saves chemical reagents and is environmentally friendly, but also has a good plating effect. The process is simple, low-cost, and easy to promote.

[0045] (4) Compared with other hot-dip plating processes, the alloy phases in the coating obtained by the present invention are mainly AlB2, TiAl3, and trace amounts of TiB2. All of these are hard phases, forming a multiphase composite coating, which effectively reduces the tendency of the coating to crack. Attached Figure Description

[0046] Figure 1 This is a SEM image of the microstructure of the coating in Example 1 of the present invention;

[0047] Figure 2 The hardness and wear rate of the coating in the embodiments of the present invention;

[0048] Figure 3This is a SEM image of the coating in Comparative Example 2 of the present invention. Detailed Implementation

[0049] The invention will be further described below with reference to process examples and accompanying drawings.

[0050] Unless otherwise specified, the equipment and raw materials used in the following examples are all commercially available. The purity of the pure aluminum is 99.99%, and the purity of the potassium borofluoride (KBF4) is 99.99%.

[0051] Example 1

[0052] The specific steps for hot-dip galvanizing a 50×30×2mm titanium alloy are as follows:

[0053] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0054] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution of aluminum / potassium borofluoride was selected, with a mass content of 80% Al and 20% KBF4.

[0055] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0056] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 700°C in the furnace until they were completely melted to obtain molten aluminum. The temperature was then lowered to 660°C. In the second stage, potassium borochlore, preheated at 40°C for 10 minutes, was wrapped in aluminum foil and added to the molten aluminum. It was then pressed down with a graphite cover and stirred for 10 minutes to allow it to fully react with the molten aluminum below the liquid surface. The furnace temperature was then raised to 700°C to obtain the Al-AlB2 plating solution.

[0057] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0058] The process for hot-dip galvanizing titanium alloy with aluminum boron is carried out according to the following steps:

[0059] Step 1: Surface pretreatment of the plated parts

[0060] (1) Immerse the titanium alloy in 60g / L potassium carbonate for 5min at room temperature to remove oil from the titanium alloy and obtain the degreased plated part.

[0061] (2) Use 5% hydrofluoric acid and 10% potassium chloride alcohol solution to remove rust and activate the titanium alloy for 5 minutes. After taking it out, place it at room temperature to dry.

[0062] Step 2: Hot-dip plating process

[0063] (1) The pretreated parts are vertically immersed in the aluminum-boron plating solution, the temperature of the plating solution is maintained at 700℃, and the parts are immersed for 10 minutes. After removing the oxide residue of the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.05.

[0064] (2) After the dip-plated part is left in the air for 30 seconds, it is cooled with water at a rate of 70℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0065] The microstructure of the hot-dip aluminum boron coated titanium alloy parts was analyzed using SEM images, as shown below. Figure 1 As shown, from Figure 1 It can be seen that the coating is tightly bonded to the substrate, without defects such as cracks or shrinkage cavities, indicating that the coating has good adhesion.

[0066] Example 2

[0067] The specific steps for hot-dip galvanizing titanium with dimensions of 50×30×2mm are as follows:

[0068] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0069] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution of aluminum / potassium borofluoride was selected, with a mass content of 90% Al and 10% KBF4.

[0070] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0071] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 690°C in the furnace until they were completely melted to obtain molten aluminum. The temperature was then lowered to 650°C. In the second stage, potassium borochlore, which had been preheated to 60°C for 15 minutes, was wrapped in aluminum foil and added to the molten aluminum. The mixture was then pressed down with a graphite cover and stirred for 13 minutes to allow it to react with the molten aluminum below the surface. After thorough stirring to ensure uniform mixing, the furnace temperature was raised to 800°C to obtain the Al-AlB2 plating solution.

[0072] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0073] The aforementioned process for hot-dip galvanizing titanium with aluminum boron is carried out according to the following steps:

[0074] Step 1: Surface pretreatment of the plated parts

[0075] (1) Immerse the titanium alloy in 70g / L potassium carbonate for 10min at room temperature to remove oil from the titanium alloy and obtain the degreased plated part.

[0076] (2) Use 2% hydrofluoric acid and 15% potassium chloride alcohol solution to remove rust and activate the titanium alloy for 15 minutes. After taking it out, place it at room temperature to dry.

[0077] Step 2: Hot-dip plating process

[0078] (1) The pretreated parts are vertically immersed in the aluminum-boron plating solution. The temperature of the plating solution is maintained at 800℃. The parts are immersed for 15 minutes. After removing the oxide residue from the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.1 m / s.

[0079] (2) After the dip-plated part is left in the air for 10 seconds, it is cooled with water at a rate of 15℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0080] Example 3

[0081] The specific steps for hot-dip galvanizing a 50×30×2mm titanium alloy are as follows:

[0082] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0083] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution of aluminum / potassium borofluoride was selected, with a mass content of 80% Al and 20% KBF4.

[0084] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0085] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium alloys. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 695°C in the furnace until they were completely melted to obtain molten aluminum. Then, the temperature was lowered to 655°C. In the second stage, potassium borochlore preheated at 60°C for 15 minutes was wrapped in aluminum foil and added to the molten aluminum. The mixture was then pressed down with a graphite cover and stirred for 11 minutes to allow it to fully react with the molten aluminum below the surface. The furnace temperature was then raised to 730°C to obtain the Al-AlB2 plating solution.

[0086] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0087] The aforementioned process for hot-dip galvanizing titanium with aluminum boron is carried out according to the following steps:

[0088] Step 1: Surface pretreatment of the plated parts

[0089] (1) Immerse the titanium alloy in 60g / L potassium carbonate for 8min at room temperature to remove oil from the titanium alloy and obtain the degreased plated part.

[0090] (2) Use 3% hydrofluoric acid and 14% potassium chloride alcohol solution to remove rust and activate the titanium alloy for 10 minutes. After taking it out, place it at room temperature to dry.

[0091] Step 2: Hot-dip plating process

[0092] (1) The pretreated parts are vertically immersed in the aluminum-boron plating solution. The temperature of the plating solution is maintained at 730℃. The parts are immersed for 20 minutes. After removing the oxide residue from the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.15 m / s.

[0093] (2) After the dip-plated part is left in the air for 30 seconds, it is cooled with water at a rate of 70℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0094] pass Figure 2 In tests conducted on Examples 1-3, the hardness of the coating was approximately 2.2-2.9 times that of the substrate, with the hardness decreasing sequentially from the interface to the surface. Analysis suggests this is due to the distribution of elements. It is worth noting that... Figure 2 (b) Although the coefficient of friction of the substrate is lower than that of the coating, this precisely indicates that the substrate has low hardness and poor wear resistance, while the coating has high hardness. During the wear process, the hard phase will antagonize the friction pair, leading to an increase in the coefficient of friction. Figure 2 (c) The wear rate of the substrate was much higher than that of the coating, and severe plastic deformation occurred, proving that the coating can effectively improve the wear resistance of the titanium substrate.

[0095] Example 4

[0096] The specific steps for hot-dip galvanizing a 50×30×2mm titanium alloy are as follows:

[0097] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0098] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution with aluminum / potassium borofluoride composition was selected, with a mass content of 85% Al and 15% KBF4.

[0099] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0100] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium alloys. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 700°C in the furnace until they were completely melted to obtain molten aluminum. Then, the temperature was lowered to 660°C. In the second stage, potassium borofluoride preheated at 50°C for 13 minutes was wrapped in aluminum foil and added to the molten aluminum. The mixture was then pressed down with a graphite cover and stirred for 10 minutes to allow it to fully react with the molten aluminum below the surface. Subsequently, the furnace temperature was raised to 700°C to obtain the Al-AlB2 plating solution.

[0101] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0102] The aforementioned process for hot-dip galvanizing titanium with aluminum boron is carried out according to the following steps:

[0103] Step 1: Surface pretreatment of the plated parts

[0104] (1) Immerse the titanium alloy in 80g / L potassium carbonate for 8min at room temperature to remove oil from the titanium alloy and obtain the degreased plated part.

[0105] (2) Use 3% hydrofluoric acid and 12% potassium chloride alcohol solution to remove rust and activate the titanium alloy for 12 minutes. After taking it out, place it at room temperature to dry.

[0106] Step 2: Hot-dip plating process

[0107] (1) The pretreated parts are vertically immersed in the aluminum-boron plating solution, the temperature of the plating solution is maintained at 700℃, and the parts are immersed for 10 minutes. After removing the oxide residue of the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.12 m / s.

[0108] (2) After the dip-plated part is left in the air for 20 seconds, it is cooled by water at a rate of 35℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0109] Example 5

[0110] The specific steps for hot-dip galvanizing a 50×30×2mm titanium alloy are as follows:

[0111] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0112] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution with aluminum / potassium borofluoride composition was selected, with a mass content of 82% Al and 18% KBF4.

[0113] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0114] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium alloys. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 700°C in the furnace until they were completely melted to obtain molten aluminum. Then, the temperature was lowered to 660°C. In the second stage, potassium borofluoride preheated at 55°C for 11 min was wrapped in aluminum foil and added to the molten aluminum. The mixture was then pressed down with a graphite cover and stirred for 10 min to allow it to react with the molten aluminum below the surface. The furnace temperature was then raised to 800°C to obtain the Al-AlB2 plating solution.

[0115] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0116] The aforementioned process for hot-dip galvanizing titanium with aluminum boron is carried out according to the following steps:

[0117] Step 1: Surface pretreatment of the plated parts

[0118] (1) Immerse the titanium alloy in 100g / L potassium carbonate for 6min at room temperature to remove oil from the titanium alloy and obtain the degreased plated part.

[0119] (2) Use 3% hydrofluoric acid and 11% potassium chloride alcohol solution to remove rust from titanium alloy for 10 minutes. After taking it out, place it at room temperature to dry.

[0120] Step 2: Hot-dip plating process

[0121] (1) The pretreated parts are vertically immersed in the aluminum-boron plating solution. The temperature of the plating solution is maintained at 800℃. The parts are immersed for 24 minutes. After removing the oxide residue from the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.11 m / s.

[0122] (2) After the dip-plated part is left in the air for 25 seconds, it is cooled with water at a rate of 50℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0123] Example 6

[0124] The specific steps for hot-dip galvanizing a 50×30×2mm titanium alloy are as follows:

[0125] Step 1: Preparation of a hot-dip aluminum-boron plating solution with special composition

[0126] Step 1: Based on the characteristics of hot-dip aluminum-boron plating on titanium alloys, a special plating solution with aluminum / potassium borofluoride composition was selected, with a mass composition of 86% Al and 14% KBF4.

[0127] Step 2: Preparation of hot-dip aluminum-boron plating solution for titanium alloy

[0128] A segmented heating method was used to prepare the hot-dip aluminum-boron plating solution for titanium alloys. In the first stage, a crucible resistance melting method was used. Pure aluminum ingots were placed in a crucible and heated to 700°C in the furnace until they were completely melted to obtain molten aluminum. Then, the temperature was lowered to 660°C. In the second stage, potassium borofluoride preheated at 40°C for 14 minutes was wrapped in aluminum foil and added to the molten aluminum. The mixture was then pressed down with a graphite cover and stirred for 13 minutes to allow it to fully react with the molten aluminum below the surface. The furnace temperature was then raised to 750°C to obtain the Al-AlB2 plating solution.

[0129] Step 2: Hot-dip galvanizing of titanium alloy with aluminum boron

[0130] The aforementioned process for hot-dip galvanizing titanium with aluminum boron is carried out according to the following steps:

[0131] Step 1: Surface pretreatment of the plated parts

[0132] (1) Immerse the titanium alloy in 90g / L potassium carbonate for 9min at room temperature to remove oil and obtain the degreased plated part.

[0133] (2) Use 3% hydrofluoric acid and 15% potassium chloride alcohol solution to remove rust and activate the titanium alloy for 8 minutes. After taking it out, place it at room temperature to dry.

[0134] Step 2: Hot-dip plating process

[0135] (1) The pretreated parts are vertically immersed in the aluminum boron plating solution, the temperature of the plating solution is maintained at 750℃, and the parts are immersed for 16 minutes. After removing the oxide residue of the plating solution with a scraper, the parts are taken out. The immersion and removal rates of the parts are both 0.09 m / s.

[0136] (2) After the dip-plated part is left in the air for 12 seconds, it is cooled with water at a rate of 20℃ / s to obtain a hot-dip aluminum boron titanium alloy part.

[0137] Comparative Example 1

[0138] A method for preparing a plating solution for titanium hot plating, wherein the plating solution is prepared by a segmented heating mode.

[0139] The first stage: using crucible resistance melting, pure aluminum ingots are placed in a crucible and heated to 700°C in the furnace until they are completely melted to obtain molten aluminum, which is then held at 700°C.

[0140] Second stage: Potassium borofluoride, preheated at 40℃ for 40 minutes, is wrapped in aluminum foil and added to the molten aluminum. It is then pressed down with a graphite cover and stirred for 10 minutes to allow it to react with the molten aluminum below the liquid surface. After thorough stirring to ensure uniform mixing, the furnace temperature is raised to 700℃ to obtain the Al-AlB2 plating solution.

[0141] Because the temperature of the molten aluminum in the crucible was too high when potassium borofluoride was added in the second stage, and potassium borofluoride has relatively poor high-temperature stability, it decomposed significantly without reacting with the molten aluminum. The principle is as follows:

[0142] KBF4→KF+BF3

[0143] As a result, the boron content in the coating was significantly reduced. This was because the generated BF3 had a low melting point, causing the boron to sinter into slag instead of entering the melt. Therefore, no boron was detected in the composition analysis of the coating.

[0144] Comparative Example 2

[0145] Similar to Example 1, the difference is that in step 2(1), the immersion time is increased to 60 minutes, resulting in an increase in coating thickness and cracking, such as Figure 3 As shown, this is because the coefficient of thermal expansion of titanium-based materials differs significantly from that of TiAl3 and AlB2. As the coating thickness increases, stress concentration leads to cracking.

[0146] Comparative Example 3

[0147] Similar to Example 1, the difference is that in step 2, Si and Fe elements are added to the plating solution, which severely hinders the reaction in the plating solution, reduces the AlB2 content in the coating, and is not conducive to improving the wear resistance of the coating.

Claims

1. A method for hot-dip plating aluminum boron onto titanium alloys, characterized in that, The specific steps are as follows: Step 1: Surface pretreatment of titanium alloy parts (1) After degreasing, washing with water and draining the water, the titanium alloy plated parts are obtained after degreasing. (2) The titanium plate coatings after degreasing were derusted and activated by hydrofluoric acid and potassium chloride alcohol solution, the oxide film was removed, and the pretreated titanium alloy coatings were obtained after being dried at room temperature. Step 2: Hot-dip plating (1) The pretreated titanium alloy plating part is vertically immersed into the aluminum-boron plating solution for plating and then taken out to obtain the plating part after plating. (2) The plated part after immersion plating is kept in the air for 10s~30s, then cooled to room temperature with water. The cooling rate of the coating is controlled at 15℃ / s~70℃ / s to obtain the hot-dip aluminum boron plated part. The composition of the hot-dip aluminum-boron plating solution on the titanium alloy surface, by mass percentage, is: 10%~20% potassium borofluoride, with the balance being Al and unavoidable impurities, wherein the impurity content does not exceed 0.01%; The preparation method of the hot-dip aluminum-boron plating solution on the titanium alloy surface includes the following steps: S1. Weigh the metallic aluminum and potassium borofluoride according to the composition of the hot-dip aluminizing and boronizing solution; S2. The aluminum metal is heated to 690℃~700℃ in the furnace until it is completely melted to obtain molten aluminum. S3. Maintain the furnace temperature at 650℃~660℃, add preheated potassium borofluoride wrapped in aluminum foil to the molten aluminum, and press it to the bottom of the furnace with a graphite cover. Stir for 10min~15min until no bubbles are generated on the surface of the liquid to obtain a hot-dip aluminum-boron plating solution for titanium alloy surface without fluxing. The preheating method of potassium borofluoride is as follows: preheat potassium borofluoride at 40℃~60℃ for 10min~15min.

2. The method for hot-dip aluminizing boron into titanium alloy according to claim 1, characterized in that, In step 1(1), the degreasing agent used is potassium carbonate with a mass concentration of 60g / L~100g / L; the degreasing is performed by immersing the titanium alloy plated part in the degreasing solvent and soaking it at room temperature for 5min~10min.

3. The method for hot-dip aluminizing boron into titanium alloy according to claim 1, characterized in that, In step 1 (2), the mass concentration of hydrofluoric acid is 2%~5%, and the concentration of potassium chloride alcohol solution is 10%~15%. Rust removal and activation are carried out simultaneously for 5 to 15 minutes.

4. The method for hot-dip plating aluminum boron onto titanium alloy according to claim 1, characterized in that, In step 2 (1), the temperature of the immersion plating solution is 700℃~800℃, and the immersion plating time is 10min~30min; The titanium alloy plated parts are vertically removed from the aluminum-boron plating solution after immersion, with the immersion rate and removal rate being equal, ranging from 0.05 to 0.15 m / s.

5. The method for hot-dip aluminizing boron into titanium alloy according to claim 1, characterized in that, In step 2(1), before removing the titanium-plated parts after immersion plating, a scraper is used to remove the oxide residue from the plating solution.

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