A method for preparing a Ti-Al intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface

Abstract

The present invention discloses a method for preparing Ti-Al system interphase layer / pure aluminum carburizing layer composite coating on the surface of a titanium or titanium alloy. The method comprises the following steps: 1. using a metal cleaning agent to remove oil from the surface of a titanium or titanium alloy workpiece and then placing it in a drying oven for drying; 2. the titanium or titanium alloy workpiece in step one is immersed in the pure aluminum liquid protected by argon and hot-dip aluminized, after a certain period of heat preservation, the titanium or titanium alloy workpiece is extracted from the pure aluminum liquid, and a TiAl3 interphase layer and a pure aluminum layer are formed on the surface of the titanium or titanium alloy workpiece; 3. the titanium or titanium alloy workpiece in step two is subjected to hydrogen-free carburizing treatment, and the surface pure aluminum layer reacts with activated carbon atoms to generate a pure aluminum carburizing layer, and the aluminum element in the TiAl3 interphase layer continues to diffuse into the matrix, and Al reacts with Ti to generate more Ti-Al system interphase layers, finally forming a Ti-Al system interphase layer / pure aluminum carburizing layer composite coating. The coating preparation method of the present invention is applicable to complex components, and the method is simple, low in cost and easy to implement.

Description

Technical Field

[0001] The invention relates to the technical field of titanium or titanium alloy surface treatment, and in particular to a method for preparing a Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy. Background Art

[0002] Titanium and its alloys possess excellent comprehensive properties, including light weight, high specific strength, strong heat resistance, and corrosion resistance. Hailed as the "metal of the future," they represent a promising new structural material. Titanium alloys are widely used across various sectors of the national economy. They are an indispensable material in rockets, missiles, and space shuttles. They are also now widely used in many other industrial sectors, including shipbuilding, chemical engineering, and power generation.

[0003] Titanium alloys have the advantages of high strength, high hardness, low density, good corrosion resistance and heat resistance. They are currently widely used in advanced aircraft engines, and the amount of high-temperature titanium alloys has accounted for 25%-40% of the total weight of the engine. Although titanium and titanium alloys have many excellent properties and are widely used in various fields, they also have some disadvantages. The common disadvantages of titanium and titanium alloys are low surface hardness (the hardness of pure titanium is about 150-200HV, and titanium alloys usually do not exceed 350HV), high friction coefficient and poor wear resistance. Titanium alloys have a "thermal barrier" temperature of 600°C. That is, when the service temperature of titanium alloys is higher than 600°C, the high-temperature oxidation resistance of titanium alloys drops sharply, which is one of the important reasons restricting the development of titanium alloys. In order to improve the high-temperature oxidation resistance of titanium alloys, people have adopted a variety of methods to modify the surface of titanium alloys. Initially, people chose to form an aluminum coating on the surface of titanium alloys in the hope of obtaining a TiAl3 intermediate phase layer with excellent high-temperature oxidation resistance. Then, the pure aluminum layer was used to react with active carbon atoms to form a pure aluminum carburized layer that is wear-resistant, high-temperature oxidation-resistant, and corrosion-resistant. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy. The method adopts a step-by-step coating method of first hot-dip aluminum plating and then hydrogen-free carburizing to ensure that a TiAl3 interphase layer with excellent high-temperature oxidation resistance is formed first, and then a pure aluminum layer is reacted with activated carbon atoms to form a pure aluminum carburized layer that is wear-resistant, high-temperature oxidation-resistant, and corrosion-resistant. The present invention is suitable for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on titanium or titanium alloy workpieces with complex structures. The coating is tightly bonded to the substrate, and the preparation method is simple, low-cost, and easy to implement.

[0005] Another object of the present invention is to provide a method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface, characterized in that the preparation method comprises the following steps:

[0006] Step 1: Use a metal cleaning agent to degrease and clean the surface of the titanium or titanium alloy workpiece, and then dry it in a drying oven;

[0007] Step 2: immersing the titanium or titanium alloy workpiece in step 1 into pure aluminum liquid protected by argon gas for hot-dip aluminum plating. After holding the temperature for a certain period of time, the titanium or titanium alloy workpiece is extracted from the pure aluminum liquid, and a TiAl3 intermediate phase layer and a pure aluminum layer are formed on the surface of the titanium or titanium alloy workpiece;

[0008] Step 3: Carburize the titanium or titanium alloy workpiece in step 2 without hydrogen. The pure aluminum layer on the surface reacts with the active carbon atoms to form a pure aluminum carburized layer. The aluminum element in the TiAl3 intermediate phase layer continues to diffuse into the matrix. Al reacts with Ti to form more Ti-Al intermediate phase layers, and finally forms a Ti-Al intermediate phase layer / pure aluminum carburized layer composite coating.

[0009] A method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy is to hot-dip aluminum on the titanium alloy to first form a TiAl3 interphase layer with excellent high-temperature oxidation resistance on the surface, and then use the pure aluminum layer to react with active carbon atoms to form a pure aluminum carburized layer with wear resistance, high-temperature oxidation resistance and corrosion resistance. The present invention provides a method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy. The method combines the advantages of two coating preparation methods, hot-dip aluminum plating and hydrogen-free carburizing. The thickness of the TiAl3 interphase layer is controlled by controlling the hot-dip aluminum plating temperature and hot-dip aluminum plating time; the thickness of the pure aluminum layer is controlled by controlling the withdrawal speed of the hot-dip aluminum plating workpiece; and the hydrogen-free carburizing technology is then used to react the surface pure aluminum layer with activated carbon atoms to form a pure aluminum carburized layer. The aluminum element in the TiAl3 interphase layer continues to diffuse into the substrate, and Al reacts with Ti to form more Ti-Al interphase layers such as TiAl3, TiAl2, TiAl, Ti2Al, Ti3Al, etc., ultimately forming a Ti-Al interphase layer / pure aluminum carburized layer composite coating. Therefore, the Ti-Al interphase layer / pure aluminum carburized layer composite coating formed by hydrogen-free carburizing after hot-dip aluminum plating is controllable.

[0010] The method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface is characterized in that the hot-dip aluminum coating temperature in step 2 is 720-760°C and the hot-dip coating time is 5-10 minutes. This temperature range ensures the formation of the target TiAl3 interphase layer after hot-dip coating while avoiding the problem of uneven Al distribution caused by rapid aluminum infiltration due to excessively high temperatures. This time range also controls the thickness of the TiAl3 interphase layer, resulting in a TiAl3 interphase layer with a thickness of 20-60 microns.

[0011] The method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface is characterized in that the TiAl3 interphase layer described in step 2 has a thickness of 20-60 microns. This thickness range ensures that sufficient aluminum in the TiAl3 interphase layer continues to diffuse into the substrate during the subsequent hydrogen-free carburizing treatment, allowing Al to react with Ti to form more Ti-Al interphase layers.

[0012] The above-mentioned method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface is characterized in that the titanium or titanium alloy workpiece is withdrawn from the pure aluminum liquid in step 2 at a speed of 5-10 cm / s. This withdrawal speed ensures that the pure aluminum layer on the workpiece surface has a thickness of 20-30 microns, thereby ensuring that a pure aluminum carburized layer is formed during subsequent hydrogen-free carburizing treatment.

[0013] The above-mentioned method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy is characterized in that the hydrogen-free carburizing temperature described in step three is 1000-1050°C, and the hydrogen-free carburizing time is 2-6 hours. The above-mentioned carburizing temperature can provide sufficient reaction driving force for the aluminum element in the TiAl3 interphase layer to continue to diffuse into the matrix, and Al and Ti react to generate more Ti-Al interphase layers, and ensure that the pure aluminum carburized layer can obtain a higher hardness. The above-mentioned carburizing time can ensure that Al and Ti fully react to generate more Ti-Al interphase layers, while avoiding the phenomenon of severe burn-off of the material surface due to excessive carburizing time, and also avoid the situation where the pure aluminum carburized layer generated by the reaction of the surface pure aluminum layer with the active carbon atoms is too thin due to insufficient carburizing time.

[0014] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the technical principle of the method for preparing the Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating on the surface of titanium or titanium alloy of the present invention.

[0016] Figure 2 3 is a scanning electron microscope microstructure photograph of the Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating obtained in Example. DETAILED DESCRIPTION

[0017] The titanium or titanium alloy surface Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating structure can be variously designed according to actual use requirements. The thickness of the generated titanium aluminum alloy intermediate phase TiAl3 intermediate phase layer can be controlled by controlling the hot dip coating temperature and hot dip coating time. The thickness of the pure aluminum layer can be controlled by controlling the speed at which the workpiece is extracted from the pure aluminum liquid. The phase structure and phase layer thickness of the Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating can also be controlled by controlling the carburizing temperature and carburizing time. Therefore, the titanium or titanium alloy surface Ti-Al system intermediate phase layer / pure aluminum carburized layer composite coating has good controllability.

[0018] Example

[0019] like Figure 1 As shown, the preparation method of this embodiment includes the following steps:

[0020] Step 1: Use a metal cleaning agent to degrease and clean the surface of the T65 titanium alloy sample, and then dry it in a drying oven;

[0021] Step 2: Immerse the T65 titanium alloy sample prepared in step 1 in pure aluminum liquid protected by argon gas for hot-dip aluminum coating. The hot-dip coating temperature is controlled to 760°C, kept at this temperature for 8 minutes, and withdrawn at a speed of 5 cm / s to form a TiAl3 intermediate phase layer and a pure aluminum layer on the surface of the T65 titanium alloy sample.

[0022] Step 3: Place the T65 titanium alloy sample from Step 2 in a hydrogen-free carburizing furnace for hydrogen-free carburizing at a temperature of 1050°C for 4 hours. The surface pure aluminum layer reacts with the activated carbon atoms to form a pure aluminum carburized layer. The aluminum element in the TiAl3 interphase layer continues to diffuse into the matrix. Al reacts with Ti to form a Ti-Al interphase layer containing TiAl3, TiAl, and Ti3Al. The final Ti-Al interphase layer is 60 microns thick, and the pure aluminum carburized layer is 25 microns thick.

[0023] The scanning electron microscope microstructure of the Ti-Al intermediate phase layer / pure aluminum carburized layer composite coating obtained in this embodiment is shown in FIG. Figure 2 shown.

[0024] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent variation made to the above embodiment based on the essence of the invention technology shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for preparing a Ti-Al interphase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface, characterized in that: The following steps are involved: Step 1: Use a metal cleaning agent to degrease and clean the surface of the titanium or titanium alloy workpiece, and then dry it in a drying oven; Step 2: immersing the titanium or titanium alloy workpiece in step 1 into pure aluminum liquid protected by argon gas for hot-dip aluminum plating. After holding the temperature for a certain period of time, the titanium or titanium alloy workpiece is extracted from the pure aluminum liquid, and a TiAl3 intermediate phase layer and a pure aluminum layer are formed on the surface of the titanium or titanium alloy workpiece; Step 3: Carburize the titanium or titanium alloy workpiece in step 2 without hydrogen. The pure aluminum layer on the surface reacts with the active carbon atoms to form a pure aluminum carburized layer. The aluminum element in the TiAl3 intermediate phase layer continues to diffuse into the matrix. Al reacts with Ti to form more Ti-Al intermediate phase layers, and finally forms a Ti-Al intermediate phase layer / pure aluminum carburized layer composite coating.

2. The method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface according to claim 1, characterized in that: The hot-dip aluminum plating temperature in step 2 is 720-760° C., and the hot-dip aluminum plating time is 5-10 minutes.

3. The method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface according to claim 1, characterized in that: The titanium or titanium alloy workpiece described in step 2 is extracted from the pure aluminum liquid at a speed of 5-10 cm / s.

4. The method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface according to claim 1, characterized in that: The thickness of the TiAl3 intermediate phase layer in step 2 is 20-60 microns, and the thickness of the pure aluminum layer is 20-30 microns.

5. The method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface according to claim 1, characterized in that: The non-hydrogen carburizing temperature in step 3 is 1000-1050° C., and the non-hydrogen carburizing time is 2-6 hours.

6. The method for preparing a Ti-Al based intermediate phase layer / pure aluminum carburized layer composite coating on a titanium or titanium alloy surface according to claim 1, characterized in that: The thickness of the Ti-Al intermediate phase layer described in step 3 is 30-70 microns, and the thickness of the pure aluminum carburized layer is 20-30 microns.

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