TC4 titanium alloy hot-dip aluminum plating method

Abstract

The invention relates to the technical field of hot-dip aluminum plating, in particular to a TC4 titanium alloy hot-dip aluminum plating method which comprises the steps that TC4 titanium alloy subjected to surface treatment is immersed in molten aluminum with different components for hot-dip plating, the temperature of the molten aluminum is controlled to be 700-1200 DEG C, the time is 0.5-5 min, the thickness of a plating layer is 10-100 micrometers, the thickness of a reaction layer is 5-50 micrometers, and the TC4 titanium alloy is subjected to hot-dip aluminum plating. The environment is protected by combining high-purity argon, and molten aluminum is prevented from being oxidized; the surface of the TC4 titanium alloy is subjected to heat treatment after dip plating is finished, the temperature in the heat treatment process is controlled to range from 400 DEG C to 600 DEG C, the time is controlled to range from 1 h to 3 h, a more uniform and compact reaction layer can be formed by adjusting the content of alloy elements in molten aluminum, especially by adding 4%-6% of magnesium element or 5%-7% of silicon element, technological parameters are easy to control, and the method is suitable for large-scale industrialization and has good application prospects. And the coating performance can be optimized according to actual application requirements.

Description

Technical Field

[0001] The invention relates to the technical field of hot-dip aluminum plating, and in particular to a TC4 titanium alloy hot-dip aluminum plating method. Background Art

[0002] Titanium alloys and aluminum alloys are key materials in industries such as aerospace and automobile manufacturing. TC4 titanium alloy is an α+β type alloy. During the process of temperature increase and decrease, there will be mutual transformation between the α phase and the β phase. Titanium alloys are widely used in high-performance equipment due to their excellent corrosion resistance, high temperature resistance and high strength; and aluminum alloys are widely used in lightweight structural materials due to their light weight and excellent processing performance. However, the physical and chemical properties of titanium and aluminum are quite different. Brittle intermetallic compounds such as TiAl3 are easily generated at high temperatures, which leads to increased brittleness and reduced strength of welded joints when dissimilar metals are connected.

[0003] The existing hot-dip aluminum coating technology has the following defects: (1) Poor corrosion resistance. Aluminum slag is easily adhered to the surface of the hot-dip aluminum coating, affecting its appearance. The coating contains brittle phases of intermetallic compounds, resulting in poor processability. (2) Surface defects are easily formed on the surface of titanium alloys. Point defects may appear on the surface of hot-dip aluminum-coated aluminum silicon steel plates, and the surface is easily oxidized. (3) The thickness of hot-dip aluminum coating is difficult to control, the metal loss is large, and the coating structure is unstable. (4) Cost and equipment requirements. During the hot-dip aluminum coating process, the plating solution has a short life, high temperature, and high cost. In addition, the metal elements in the coating will react with the strip equipment at high temperature to generate solid particle slag, affecting product quality and equipment status.

[0004] Hot-dip aluminum coating technology has gradually attracted attention because it can pre-form a protective layer on the titanium surface, reduce interface reactions, and improve connection quality. By optimizing the composition of aluminum liquid, dipping temperature and time, and heat treatment technology, the growth of interface brittle compounds can be effectively inhibited to achieve a uniform and dense interface structure. Summary of the invention

[0005] In view of the problem that poor corrosion resistance exists in the existing hot-dip aluminum plating technology and brittle compounds are generated at the interface, the present invention provides a TC4 titanium alloy hot-dip aluminum plating method, which is performed by immersing the surface of the TC4 titanium alloy in aluminum liquid of different compositions for dip plating, controlling the dip plating temperature and the dip plating time, and combining with high-purity argon protection to prevent oxidation of the aluminum liquid, adjusting the content of alloy elements in the aluminum liquid to inhibit the excessive growth of intermetallic compounds, and having excellent corrosion resistance and high temperature resistance.

[0006] The invention provides a TC4 titanium alloy hot-dip aluminum plating method, comprising: immersing the pretreated TC4 titanium alloy into molten aluminum liquid for hot-dip aluminum plating, wherein the aluminum liquid is pure aluminum, Al-Mg alloy or Al-Si alloy, the aluminum liquid temperature is set to 700°C-1200°C, the hot-dip aluminum plating time is 1-5min, a coating is formed on the surface of the TC4 titanium alloy during the hot-dip aluminum plating, the coating comprises a reaction layer and an aluminum plating layer from inside to outside, the coating thickness is 10μm-100μm, the reaction layer thickness is 5μm-50μm, and after the dipping is completed, the surface of the TC4 titanium alloy is heat treated, the temperature in the heat treatment process is controlled to be 400°C-600°C, and the time is controlled to be 1-3h.

[0007] Furthermore, the pretreatment includes degreasing, pickling, cleaning and drying; degreasing is to use ethanol solution to degrease and clean the surface of TC4 titanium alloy; pickling is to place TC4 titanium alloy in mixed acid for pickling, the pickling time is 15-20 minutes, and after pickling, the TC4 titanium alloy is rinsed with deionized water and anhydrous ethanol, and dried for use.

[0008] Further, the mixed acid solution is one of 40% HNO3 and 5% HF, 30% HNO3 and 70% deionized water or 50% HCl aqueous solution.

[0009] Furthermore, hot-dip aluminum plating is carried out in a high-purity argon protection environment with a volume fraction of 99.999%.

[0010] Furthermore, the aluminum content of pure aluminum in the aluminum liquid is ≥99%, the magnesium content by weight in the Al-Mg alloy is 4%-6%, and the silicon content in the Al-Si alloy is 5%-7%.

[0011] Furthermore, when the temperature of the aluminum liquid is [700-900)°C, the thickness of the reaction layer is 5μm-15μm.

[0012] Furthermore, when the temperature of the aluminum liquid is [900-1200]°C, the thickness of the reaction layer is 15 μm-50 μm.

[0013] Furthermore, after the immersion plating is completed, the TC4 titanium alloy is taken out from the aluminum liquid and placed in the air for natural cooling.

[0014] The beneficial effects of the present invention are: (1) After hot-dip aluminum plating, the corrosion resistance and oxidation resistance of the TC4 titanium alloy surface can be improved by heat treatment of the TC4 titanium alloy surface.

[0015] (2) The present invention immerses the surface-treated TC4 titanium alloy into Al-Mg, Al-Si or pure aluminum liquid, and controls the immersion plating temperature and time to form a more uniform and dense reaction layer.

[0016] (3) The process parameters of the present invention are easy to control and suitable for large-scale industrialization. The coating performance can be optimized according to actual application requirements. In a high-purity argon protection environment, the oxidation of aluminum liquid can be effectively prevented. DETAILED DESCRIPTION

[0017] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0018] Example 1 A TC4 titanium alloy hot-dip aluminum plating method comprises the following steps: (1) The TC4 titanium alloy was pretreated by placing it in a mixed acid solution of 40% HNO3 and 5% HF, pickling it for 15 minutes to remove the surface oxide layer and impurities, then cleaning it with deionized water and anhydrous ethanol, and drying it for later use.

[0019] (2) The pretreated TC4 titanium alloy was placed in molten pure aluminum liquid. The aluminum liquid temperature was set to 700°C and the immersion time was 1 min. The entire process was carried out in an Ar atmosphere with a purity of 99.999% to prevent oxidation of the aluminum liquid. After immersion plating, the titanium alloy was taken out and naturally cooled in the air. A uniform coating was formed on the surface of the TC4 titanium alloy, including a reaction layer and an aluminum plating layer from the inside to the outside. After natural cooling, heat treatment was performed at a temperature of 400°C and a time of 1 min.

[0020] The surface of the obtained aluminum-plated layer is smooth and uniform, and a continuous intermetallic compound reaction layer is formed on the interface. The thickness of the reaction layer is 5μm and the thickness of the coating is 10μm. This coating is suitable for application scenarios with high corrosion resistance requirements.

[0021] Example 2 (1) The TC4 titanium alloy is pretreated by placing the TC4 titanium alloy in a 50% HCl solution for 20 minutes to remove the surface oxide film, and then thoroughly cleaned with deionized water, cooled naturally in the air, and then dried for later use.

[0022] (2) The pretreated titanium alloy was immersed in an Al-Mg alloy melt (containing 6% Mg) at a temperature of 950°C for 2 min. The entire process was carried out in an Ar atmosphere with a purity of 99.999% to prevent oxidation of the aluminum liquid. After immersion plating, the titanium alloy was taken out and naturally cooled in the air. A uniform coating was formed on the surface of TC4, which included a reaction layer and an aluminum coating from the inside to the outside. After natural cooling, heat treatment was carried out at a temperature of 500°C for 2 h.

[0023] In the reaction layer of the coating obtained in Example 2, the reaction layer thickness is 25 μm, and the coating thickness is 50 μm, which is suitable for application fields requiring improved wear resistance and impact resistance.

[0024] Example 3 (1) The TC4 titanium alloy is pretreated by placing the TC4 titanium alloy in a 50% HCl solution for 20 minutes to remove the surface oxide film, and then thoroughly cleaned with deionized water, cooled naturally in the air, and then dried for later use.

[0025] (2) The pretreated TC4 titanium alloy was immersed in an Al-Si alloy melt (containing 7% Si) at a temperature of 1200°C for 5 min. The entire process was carried out in an Ar atmosphere with a purity of 99.999% to prevent oxidation of the aluminum liquid. After immersion plating, the titanium alloy was taken out and naturally cooled in the air. A uniform coating was formed on the surface of the TC4 titanium alloy, including a reaction layer and an aluminum coating from the inside to the outside. After natural cooling, heat treatment was performed at a temperature of 600°C for 3 h.

[0026] The interface reaction layer thickness of the coating obtained in Example 3 is 50 μm, and the coating thickness is 100 μm. It has good high temperature resistance and is suitable for high temperature working environments in the aerospace field.

[0027] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and such changes or substitutions shall be within the scope of protection of the present invention.

Claims

1. A TC4 titanium alloy hot-dip aluminum coating method, characterized in that: The method comprises immersing the pretreated TC4 titanium alloy into molten aluminum liquid for hot-dip aluminum plating, wherein the aluminum liquid is pure aluminum, Al-Mg alloy or Al-Si alloy, the aluminum liquid temperature is set to 700°C-1200°C, the hot-dip aluminum plating time is 1-5min, a coating is formed on the surface of the TC4 titanium alloy during hot-dip aluminum plating, the coating comprises a reaction layer and an aluminum plating layer from the inside to the outside, the coating thickness is 10μm-100μm, the reaction layer thickness is 5μm-50μm, and after the dipping is completed, the surface of the TC4 titanium alloy is heat treated, the temperature during the heat treatment process is controlled to be 400°C-600°C, and the time is controlled to be 1-3h.

2. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: The pretreatment includes degreasing, pickling, cleaning and drying; degreasing is to use ethanol solution to degrease and clean the surface of TC4 titanium alloy; pickling is to place TC4 titanium alloy in a mixed acid solution for pickling, the pickling time is 15-20 minutes, and after pickling, the TC4 titanium alloy is rinsed with deionized water and anhydrous ethanol, and dried for use.

3. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 2, characterized in that: The mixed acid solution is one of 40% HNO3 and 5% HF, 30% HNO3 and 70% deionized water or 50% HCl aqueous solution.

4. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: Hot-dip aluminum plating is carried out in a high-purity argon protection environment with a volume fraction of 99.999%.

5. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: The aluminum content of pure aluminum in aluminum liquid is ≥99%, the magnesium content by weight in Al-Mg alloy is 4%-6%, and the silicon content in Al-Si alloy is 5%-7%.

6. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: When the aluminum liquid temperature is [700-900)℃, the thickness of the reaction layer is 5μm-15μm.

7. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: When the aluminum liquid temperature is [900-1200]℃, the thickness of the reaction layer is 15μm-50μm.

8. A TC4 titanium alloy hot-dip aluminum coating method as claimed in claim 1, characterized in that: After the immersion plating is completed, the TC4 titanium alloy is taken out from the aluminum liquid and placed in the air to cool naturally.