Low-temperature rapid aluminizing method based on titanium alloy / titanium-aluminum alloy surface

Abstract

The invention belongs to the field of heat treatment, and particularly relates to a low-temperature rapid aluminizing method based on a titanium alloy / titanium-aluminum alloy surface. According to the method, different surface pretreatment process parameters are adopted for metal such as titanium alloy and titanium-aluminum alloy, and the parameters such as sand blasting pressure, sand blasting time and the distance between a nozzle and the surface of a sample are combined, so that the pre-permeation surface of a workpiece is activated to the maximum extent; the method can be used for preparing the high-temperature-oxidation-resistant and hot-corrosion-resistant protective coating with good binding force and high performance on the surfaces of various common alloy materials such as titanium alloy and titanium-aluminum alloy, and has important technical value and application prospect for application of the alloy in a high-temperature environment and hot-corrosion-resistant application.

Description

Technical Field

[0001] The invention belongs to the field of heat treatment, and in particular relates to a method for rapid low-temperature aluminum infiltration on the surface of a titanium alloy / titanium-aluminum alloy. Background Art

[0002] Titanium alloys and titanium aluminum alloys are currently used in large quantities in the fields of aviation, aerospace, automobiles, machinery, ships, and chemical industry. At the same time, these alloys have been widely used in civilian life due to their advantages such as low density, high strength, and good toughness. However, they have high chemical activity and are prone to chemical reactions with many substances. They are very prone to oxidation or corrosion in high temperature or humid environments, which leads to significant changes in the chemical composition and structure of the alloy matrix, causing corrosion cracking or instability of the parts during service.

[0003] Applying protective coatings on metal surfaces can improve the wear resistance, corrosion resistance, durability, etc. of the metal surface, and is a commonly used treatment method for metal surfaces. High-temperature resistant and corrosion-resistant coatings are applied to the surface of parts that are in service in high-temperature environments. A layer of material that is resistant to high-temperature oxidation and thermal corrosion is applied to the surface of parts that are in service in high-temperature environments to enhance the workpiece's resistance to high-temperature oxidation and thermal corrosion, and improve the workpiece's service life and work efficiency. Protective coatings have been applied to aircraft engines, gas turbine compressor blades, and turbine blades, and have achieved good results. For titanium alloy and titanium-aluminum alloy parts that work in high-temperature environments, applying protective coatings on their surfaces can produce many benefits during their use.

[0004] The protective coating applied to the surface of metal parts serving in high temperature environments is usually an aluminide coating. The preparation processes of aluminide coatings include powder embedding aluminization, slurry aluminization, multi-arc plasma aluminization and other technologies. Among them, the process of preparing aluminide coatings on its surface by powder embedding is widely used. It only needs to place the metal workpiece in a diffusing agent containing aluminum elements, heat it to a certain temperature, and keep it warm for a suitable time. The active atoms of aluminum elements produced by the thermal decomposition of the diffusing agent are adsorbed on the surface of the workpiece and diffuse into the surface of the workpiece, thereby changing the chemical composition, organization and properties of the surface of the workpiece. The preparation process of powder embedding aluminizing coating is simple and has good high-temperature oxidation resistance, but it also has many disadvantages. For example, the coating is brittle and easy to crack and peel off; the coating and the substrate are prone to mutual diffusion; it is not resistant to sulfidation and thermal corrosion. Compared with the infiltrated non-metals (carbon, nitrogen, etc.), the atomic radius of metal elements is large, it is not easy to penetrate, the infiltration layer is shallow, and generally needs to be diffused at a relatively high temperature. The compound or passivation film formed after the metal element penetrates has high resistance to high temperature oxidation and thermal corrosion, and can be used in different working environments. The materials to be plated can be carbon steel, stainless steel, nickel-based high-temperature alloy, cobalt-based high-temperature alloy, and iron-based high-temperature alloy.

[0005] The common aluminizing temperature is 850-1050℃. If the temperature is too low, the aluminizing speed will drop sharply; if the temperature is too high, the grains of the aluminized parts will grow rapidly and the mechanical properties of the materials will decrease. However, long-term high temperature environment will have a harmful effect on the organizational structure and related thermal physical properties of materials such as titanium alloys and titanium aluminum alloys, which will limit the later use of parts. Summary of the invention

[0006] In view of the problems in the prior art, the present invention provides a method for rapid low-temperature aluminizing of titanium alloy / titanium aluminum alloy surface. This method can prepare a protective coating with good bonding force, high performance, high-temperature oxidation resistance and thermal corrosion resistance on the surface of various commonly used alloy materials such as titanium alloy and titanium aluminum alloy, which has important technical value and application prospects for the application of such alloys in high-temperature environments and thermal corrosion resistance.

[0007] The technical solution of the present invention is: A method for rapid low-temperature aluminizing of titanium alloy / titanium-aluminum alloy surface, comprising the following steps: Step (1) Preparation of penetrant: rare earth oxide powder, ammonium chloride powder and iron-aluminum alloy powder are mixed in a proportion of 0.1%-1%: 1%-4%: the remainder by mass; the mixed powder is placed in a ball mill and ball milled; Step (2) inspecting the surface of the part to ensure that there are no surface defects that affect the quality of the infiltration layer, and protecting the non-infiltration surface; Step (3) using a sand blasting machine to blast sand on the surface of the part to be infiltrated, removing the oxide scale and other attachments on the surface of the part, and activating the surface to be infiltrated. After the sand blasting treatment, the surface state of the surface of the part to be infiltrated is uniform; Step (4) aluminizing: the parts treated by sandblasting in step (3) are placed in a muffle furnace for aluminizing within 8 hours, kept at 350°C to 650°C for 2h to 4h, and then air-cooled.

[0008] Furthermore, in the above-mentioned method for rapid low-temperature aluminum infiltration on the surface of titanium alloy / titanium-aluminum alloy, the rare earth oxide powder in step (1) is one of cerium oxide powder and yttrium oxide powder or a mixture of the two.

[0009] Furthermore, in the above-mentioned method for rapid low-temperature aluminum infiltration on the surface of titanium alloy / titanium-aluminum alloy, in step (1), the ball milling speed is 800-1200 r / min, and the ball milling time is 4-8 h.

[0010] Furthermore, in the above-mentioned method for low-temperature rapid aluminum infiltration on the surface of titanium alloy / titanium-aluminum alloy, in step (3), the sand blasting uses corundum sand with a particle size of 120 mesh to 220 mesh, the working pressure is 0.2 MPa to 0.5 MPa, the sand blasting time is 20 s to 50 s, and the distance from the spray gun nozzle to the surface to be infiltrated is 20 cm.

[0011] Furthermore, in the above-mentioned method of rapid low-temperature aluminum diffusion on the surface of titanium alloy / titanium-aluminum alloy, after the aluminum diffusion is completed, the thickness of the diffusion layer is 0.02mm~0.04mm, and the thickness of the aluminum oxide film formed on the surface is 0.5μm~2μm.

[0012] Advantages and beneficial effects of the present invention: (1) The present invention not only improves the high-temperature oxidation resistance and thermal corrosion resistance of the base alloy, but also shortens the temperature and time for preparing the aluminide coating by the powder embedding method, and the preparation process is energy-saving and environmentally friendly; (2) The present invention overcomes the shortcomings of the powder embedding method of aluminizing, such as high temperature, long time, large energy consumption and damage to the internal structure and mechanical properties of the workpiece; it avoids the harmful effects of traditional high temperature and long time aluminizing operation on the organizational structure and related thermal physical properties of titanium alloy and titanium aluminum alloy parts, so that the later use status of the parts is not restricted. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 (A) is the cross-sectional morphology of the titanium aluminum alloy surface after aluminum infiltration using the method of the present invention, and (B) is the cross-sectional morphology after oxidation at 900°C and a 100h heat resistance test; Figure 2 (A) is the cross-sectional morphology of the aluminized layer on the titanium aluminum alloy surface after aluminizing with ordinary aluminizing agent, and (B) is the cross-sectional morphology after oxidation at 900℃ and a 100h heat resistance test. DETAILED DESCRIPTION

[0014] The specific implementation modes of the present invention are further described in detail below in conjunction with the drawings and examples of the specification. The following examples are used to illustrate the present invention but cannot be used to limit the scope of the present invention. Example 1

[0015] This embodiment is a method for rapid low-temperature aluminum infiltration on the surface of titanium aluminum alloy, comprising the following steps: Step (1) Preparation of the penetrant: The rare earth oxide powder is selected from cerium oxide and yttrium oxide powder mixed in a ratio of 1:1, and the rare earth oxide powder, ammonium chloride powder, and iron-aluminum alloy powder are mixed in a ratio of 1:1:98, and the mixed powder is put into a ball mill for ball milling; the ball milling speed is 800 r / min, and the ball milling time is 4 hours; Step (2) inspect the surface of the parts to ensure that there are no surface defects such as knocks, bruises, cracks, pits, etc. that may affect the quality of the carburized layer, and protect the non-carburized surface; Step (3) using a sand blasting machine to blast sand on the surface of the part to be infiltrated, to remove the oxide scale and other attachments on the surface of the part, and to activate the surface to be infiltrated, using corundum sand with a particle size of 220 mesh, a working pressure of 0.5 MPa, a sand blasting time of 30 seconds, and a distance of 20 cm from the spray gun nozzle to the surface to be infiltrated. After the sand blasting treatment, the surface state of the surface of the part to be infiltrated is uniform; Step (4) Aluminizing: The parts treated by sandblasting in step (3) are placed in a muffle furnace for aluminizing within 8 hours, kept at 550°C for 4 hours, and then air-cooled.

[0016] The depth of the infiltration layer on the surface of the titanium-aluminum alloy after aluminizing in this embodiment is 0.02 mm, and a 0.5 μm aluminum oxide film is formed on the surface. Figure 1 As shown in the figure, after 900℃ oxidation and 100h heat resistance test, a complete oxide film can be formed, and the infiltration layer has no wrinkling, bubbling, cracking, warping, or shedding. The cross-sectional morphology of the infiltration layer after the titanium aluminum alloy surface is infiltrated with ordinary aluminizing agent is as follows Figure 2 As shown in the figure, it can be seen that after oxidation at 900℃ and 100h heat resistance test, there is no complete oxide film on the surface.

Claims

1. A method for rapid low-temperature aluminizing of titanium alloy / titanium aluminum alloy surface, characterized in that: The following steps are involved: Step (1) Preparation of penetrant: rare earth oxide powder, ammonium chloride powder and iron-aluminum alloy powder are mixed in a proportion of 0.1%-1%: 1%-4%: the remainder by mass, and the mixed powder is placed in a ball mill for ball milling; Step (2) Inspect the surface of the part to ensure that there are no surface defects that affect the quality of the carburized layer, and protect the non-carburized surface; Step (3) using a sand blasting machine to blast sand on the surface of the part to be infiltrated, removing the oxide scale and other attachments on the surface of the part, and activating the surface to be infiltrated. After the sand blasting treatment, the surface state of the surface of the part to be infiltrated is uniform; Step (4) aluminizing: the parts treated by sandblasting in step (3) are placed in a muffle furnace for aluminizing within 8 hours, kept at 350°C to 650°C for 2h to 4h, and then air-cooled.

2. The method for rapid low-temperature aluminizing of titanium alloy / titanium aluminum alloy surface according to claim 1, characterized in that: The rare earth oxide powder in step (1) is one or a mixture of cerium oxide and yttrium oxide, and the mixing ratio of cerium oxide to yttrium oxide is 1:1 to 4:

1.

3. The method for rapid low-temperature aluminizing of titanium alloy / titanium aluminum alloy surface according to claim 1, characterized in that: In step (1), the ball milling speed is 800-1200 r / min, and the ball milling time is 4-8 h.

4. The method for rapid low-temperature aluminizing of titanium alloy / titanium aluminum alloy surface according to claim 1, characterized in that: In step (3), the sand blasting uses corundum sand with a particle size of 120 mesh to 220 mesh, the working pressure is 0.2 MPa to 0.5 MPa, the sand blasting time is 20 s to 50 s, and the distance from the spray gun nozzle to the surface to be infiltrated is 20 cm.

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