A method for preparing a titanium-aluminum composite sputtered layer for a general semiconductor device cavity

Abstract

This invention relates to the field of materials surface engineering technology, and in particular to a method for preparing a titanium-aluminum composite lamination layer for use in semiconductor device cavities. The method includes sandblasting a substrate, followed by arc lamination of an 80–120 μm titanium underlayer under a locally inert atmosphere, and then lamination of a 200–300 μm aluminum overlayer in an atmospheric environment. This method achieves high bonding strength (30–32 N / mm²) while avoiding titanium oxidation through a gradient structure of "titanium underlayer and aluminum surface," interfacial micro-diffusion, and a synergistic mechanism of mechanical interlocking. The processing cost is reduced by 40%–50% compared to pure titanium lamination, meeting the dual requirements of high coating reliability and economical mass production for semiconductor devices.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering and functional coating technology, specifically a method for preparing a titanium-aluminum composite spray layer for use in semiconductor device cavities. Background Technology

[0002] In semiconductor manufacturing equipment, cavity components operate under harsh environments characterized by high temperatures, high vacuum, and strong plasma corrosion. The surface properties of their inner walls directly impact the equipment's stability, cleanliness, and lifespan. To enhance the adsorption capacity of the cavity's inner walls for deposited films, resistance to plasma sputtering, and corrosion resistance, thermal spraying (melt spraying) technology is widely used to construct functional protective coatings. Currently, the industry primarily uses aluminum (Al) or titanium (Ti) as single materials for melt spraying. Among these technologies, Al sputtering is a mature and low-cost process suitable for conventional operating conditions. However, its interfacial bonding strength with the substrate is relatively low, and the coating is prone to peeling under high stress or strong corrosion environments, making it difficult to meet the reliability requirements of advanced processes. While Ti sputtering possesses excellent comprehensive performance—including tensile strength ≥900 MPa, low density (approximately 4.5 g / cm³), outstanding corrosion resistance (salt spray test corrosion resistance time ≥1000 h), and long-term operating temperature up to 600 ℃—its high chemical reactivity necessitates sputtering in a vacuum or inert atmosphere, resulting in processing costs 3–5 times higher than conventional processes, severely limiting its application in large-scale production. Therefore, achieving a balance between high bonding strength and high service stability while maintaining economic efficiency has become a key technical challenge in the field of surface engineering for semiconductor device cavities.

[0003] To address the aforementioned contradictions, the industry has attempted to combine the advantages of both by constructing aluminum-titanium composite coatings. For example, patent CN119800271A proposes using high-velocity vapor deposition (HVOF) to first deposit an aluminum layer as a base layer on the cavity surface, then deposit a titanium layer on top to form a surface layer, followed by vacuum heat treatment. However, this approach has significant drawbacks: while the HVOF process can increase particle velocity, it still operates in an open atmospheric environment. In its molten state, titanium readily reacts with oxygen to form brittle oxides such as TiO2, significantly reducing the coating's density and interfacial bonding strength. Furthermore, the thermal expansion coefficients of aluminum and titanium differ significantly (Al is approximately 23 × 10⁻⁶). -6 / ℃, Ti is approximately 8.6 × 10 -6The titanium layer, at temperatures ranging from 0.5°C to 100°C, is prone to thermal stress concentration at the interface during heat treatment or actual service, inducing microcracks or even delamination failure. Furthermore, this structure lacks compositional control or functional optimization of the titanium layer, failing to effectively balance cost and performance. Another related technology, as described in publication CN118099101A, involves a titanium-aluminum composite bonding layer, but it employs a physical sputtering process applied to electronic packaging substrates. The coating thickness is only in the micrometer range, and its aim is to improve soldering performance, rather than constructing a functional sputtering layer with tens to hundreds of micrometers thick, high adhesion, and high roughness suitable for general semiconductor cavities. Therefore, it differs fundamentally from this invention in terms of process route, structural function, and application scenarios. In summary, existing technologies still have significant shortcomings in sputtering atmosphere control, interface compatibility design, oxidation suppression mechanisms, and engineering applicability to complex cavity structures. A novel method for preparing titanium-aluminum composite sputtering layers is urgently needed to achieve synergistic optimization of low cost, high bonding strength, and high service reliability. Summary of the Invention

[0004] This invention addresses the technical shortcomings of existing electroplating coatings on the surfaces of cavity components in semiconductor devices, which struggle to achieve a balance between bonding strength, service reliability, and manufacturing cost. It provides a structural design for a titanium-aluminum composite electroplating layer and its segmented fabrication method. The method defines a layer sequence of "titanium base layer – aluminum top layer," controls the thickness and roughness parameters of each layer, employs an arc electroplating process under localized inert atmosphere protection to deposit the titanium layer, and completes the aluminum layer deposition in an atmospheric environment. This significantly improves interfacial bonding strength while avoiding titanium oxidation, and substantially reduces material and process costs, meeting the comprehensive requirements of semiconductor devices for high cleanliness, high stability, and mass production feasibility.

[0005] This invention provides a method for preparing a titanium-aluminum composite molten lamination layer for cavity components of semiconductor devices, comprising pretreatment of a substrate and sequential deposition of a titanium molten lamination underlayer and an aluminum molten lamination overlay layer, wherein: the titanium molten lamination underlayer is directly formed on the surface of the substrate roughened by sandblasting, with a thickness of 80–120 μm and a surface roughness Rz of 120 μm; the aluminum molten lamination overlay layer is formed on the titanium molten lamination underlayer, with a thickness of 200–300 μm and a surface roughness Rz of 150 μm; the titanium layer and the aluminum layer form a metallurgical-mechanical composite interface without continuous oxide inclusions, the interface transition zone thickness is 2–5 μm, including a mechanical interlocking structure formed by aluminum droplets filling the micropores on the surface of the titanium layer at high temperature, and a micro-diffusion phase formed by limited solid solution diffusion of titanium and aluminum elements at the interface.

[0006] Furthermore, the substrate is one of stainless steel, aluminum alloy or nickel-based alloy. After degreasing and drying, its surface is sandblasted with corundum or silicon carbide abrasive with a particle size of no more than 50 μm to obtain a uniformly distributed anchor pattern structure. The surface roughness Rz is controlled to be 120 μm to ensure that the subsequent melt spray layer and the substrate form an effective mechanical interlock.

[0007] Furthermore, the titanium underlayer is deposited using arc spraying (ARC) technology. During the spraying process, a localized inert atmosphere is applied to the nozzle exit area. This inert atmosphere consists of argon gas with a purity of not less than 99.999% and an argon gas flow rate of not less than 20 L / min, ensuring that the oxygen content in the spraying area is controlled below 50 ppm. The titanium wire has a purity of not less than 99.5%, and the main phase of the titanium layer obtained by spraying is α-Ti solid solution with an oxygen content of not more than 0.2 wt%. No brittle oxide phases such as TiO2 or Ti2O are detected. After the titanium layer is deposited, its surface retains the original sprayed morphology and is not subjected to grinding, polishing, or heat treatment.

[0008] Furthermore, the aluminum spray coating is deposited immediately in a conventional atmospheric environment after the titanium layer is deposited, without the need for additional atmosphere control or vacuum conditions. The aluminum layer uses aluminum wire or aluminum powder with a purity of not less than 99.5% as raw material, and is applied by flame spraying or arc spraying. When the sprayed particles impact the surface of the titanium layer, good wetting is achieved due to the high surface energy of the titanium layer (>1000 mN / m), with a contact angle θ less than 30°. During the cooling process, the aluminum's coefficient of thermal expansion (23×10⁻⁶) is also utilized. -6 / ℃) is higher than that of titanium (8.6×10 -6 / ℃) while a residual compressive stress field is formed at the interface. This compressive stress field suppresses the interfacial tensile stress caused by thermal expansion mismatch during thermal cycling, thereby enhancing the interlayer bonding stability.

[0009] The thickness of the titanium layer is limited to 80–120 μm, based on the following technical considerations: if the thickness is less than 80 μm, it cannot effectively isolate the substrate from direct contact with corrosive plasma, and it is difficult to provide sufficient mechanical support strength; if it exceeds 120 μm, the amount of titanium material used will increase significantly, leading to increased costs, and the inherent brittleness of the titanium layer may cause cohesive cracking; the thickness of the aluminum layer is set to 200–300 μm to meet the functional requirements of the semiconductor cavity for surface roughness (Rz≥150μm) and film adsorption capacity, while utilizing the high plasticity of aluminum (elongation>30%) to buffer thermal stress and cover microscopic defects on the surface of the titanium layer.

[0010] Specifically, the interfacial bonding mechanism between the titanium layer and the aluminum layer does not rely solely on physical interlocking, but is achieved through the synergistic effect of the following three actions: First, the titanium layer retains the high roughness profile (Rz=120 μm) formed after sandblasting, forming a "primary anchor" with the substrate; Second, when the aluminum droplets impact the titanium layer, they fill the micropores and grooves on its surface, forming a "secondary nesting" mechanical interlocking structure after cooling; Third, under the action of high temperature during melting (approximately 2000–3000 ℃), aluminum atoms undergo short-range diffusion along the titanium grain boundaries, forming an Al-Ti micro-diffusion transition region with a thickness of 2–5 μm. This region does not contain continuous oxide interlayers, and X-ray diffraction (XRD) analysis shows that the main phases are α-Ti and a small amount of Al3Ti intermetallic compounds dispersedly, with no TiO2 characteristic peaks observed.

[0011] Furthermore, the specific process steps of the preparation method are as follows:

[0012] S1: Degrease and clean the substrate of the cavity components to remove surface oil and organic contaminants. Then, under compressed air pressure of 0.5–0.7 MPa, use corundum abrasive with a particle size ≤50 μm to sandblast the surface at a sandblasting angle of 75°–85°. After treatment, the surface roughness Rz reaches 120 μm. Then, dry at 60–80 ℃ for 30 minutes to ensure that there is no moisture residue on the surface.

[0013] S2: Fix the pretreated substrate onto the arc spraying fixture, start the arc spraying equipment, use pure titanium wire (Ti≥99.5%) with a diameter of 2.0 mm as the wire feeding material, set up an annular argon gas protective cover around the spray gun outlet, and introduce high-purity argon gas with a flow rate ≥20L / min to make the oxygen content in the spraying area <50 ppm; adjust the arc current to 200–300 A, the voltage to 30–40 V, the spray gun moving speed to 0.8–1.2 m / min, and the spraying distance to 150–200 mm to deposit a titanium arc spraying underlayer with a thickness of 80–120 μm. Monitor the layer thickness in real time during the deposition process to ensure that the thickness uniformity deviation does not exceed ±10 μm;

[0014] S3: Within 5 minutes after the titanium layer deposition is completed, without changing the tooling or interrupting the production line process, switch to the aluminum spraying mode. Use aluminum wire or spherical aluminum powder with a purity of ≥99.5% to deposit the aluminum coating layer in an atmospheric environment using flame or arc spraying. When using flame spraying, the fuel gas is a propane / oxygen mixture, and the gas ratio is adjusted according to a volume ratio of 1:1.2–1.5. When using arc spraying, the current is 180–250 A, the voltage is 28–35 V, the spray gun moving speed is 1.0–1.5 m / min, the spraying distance is 180–220 mm, the deposition thickness is controlled at 200–300 μm, and the surface roughness Rz reaches 150 μm.

[0015] S4: After the aluminum layer is deposited, the workpiece is placed in still air and allowed to cool naturally to room temperature. The cooling rate is controlled at ≤5 ℃ / min to avoid rapid cooling that introduces thermal shock stress. The entire process does not require subsequent heat treatment, sealing, or surface modification.

[0016] The local inert atmosphere protection only applies to the titanium layer melting and spraying stage, and the protected area covers an area of ​​about 200 mm from the spray gun outlet to the substrate surface. This design eliminates the need for the entire equipment to be placed in a vacuum or glove box environment. Only a small gas shielding device needs to be integrated at the front end of the spray gun to achieve effective oxidation prevention, which greatly reduces the equipment modification cost and energy consumption. The feasibility of melting and spraying the aluminum layer in the atmosphere stems from the self-protective properties of the dense Al2O3 film formed at high temperatures. In addition, aluminum has a low melting point (660 ℃) and good fluidity, making it easy to spread and form on the surface of the titanium layer.

[0017] Furthermore, the overall thickness of the titanium-aluminum composite fusion coating is 280–420 μm, which meets the requirements of semiconductor device cavities for functional coating thickness (typically ≥250 μm). Its average bonding strength, tested according to ASTM C633 standard, is 30–32 N / mm², significantly higher than the 24–25 N / mm² of pure aluminum fusion coating, and close to the theoretical lower limit of bonding strength of pure titanium fusion coating (approximately 35 N / mm²). After 500 cycles of thermal cycling from 600 ℃ to room temperature, there are no visible cracks, blistering, or delamination on the coating surface. After 1000 hours of salt spray testing (ASTM B117), there are no signs of substrate corrosion, indicating that it has excellent thermal stability and corrosion resistance.

[0018] In particular, the "titanium base layer + aluminum overlay" structural sequence defined in this invention has an irreversible technical logic: if an aluminum base layer and a titanium overlay are used (as described in CN119800271A), TiO2 oxide will inevitably be generated during the atmospheric spraying process. This oxide is located at the aluminum / titanium interface and becomes a weak bonding phase, which severely weakens the interlayer bonding force. At the same time, the thermal expansion coefficient of the aluminum layer is much higher than that of titanium. During thermal cycling, the aluminum layer shrinks more and generates tensile stress on the upper titanium layer, which can easily induce interfacial delamination. In contrast, this invention places high-strength, low-expansion titanium at the bottom layer, which is directly bonded to the substrate and bears the main mechanical load. The aluminum layer, as a highly ductile and high-roughness surface layer, not only provides a functional surface but also absorbs thermal stress through its ductility. The two form a complementary rather than antagonistic relationship under the thermo-mechanical coupling effect.

[0019] In summary, this invention solves the core problems of high cost of titanium sputtering, weak bonding of aluminum sputtering, and unstable interface of composite coatings in existing technologies by reconstructing the structural sequence, optimizing the thickness ratio, innovating the interface bonding mechanism, and improving the atmosphere control strategy. There is a clear synergistic relationship between the parameters of the described technical solution: the combination of a titanium layer thickness ≤120 μm and an aluminum layer thickness ≥200 μm reduces the amount of titanium material used to 1 / 3–1 / 2 of that of a pure titanium coating; the titanium layer Rz=120 μm matches the substrate to achieve primary anchoring, while the aluminum layer Rz=150 μm forms secondary nesting; local argon protection inhibits titanium oxidation, and atmospheric deposition of the aluminum layer ensures process compatibility; interfacial micro-diffusion and mechanical interlocking jointly construct a high-strength bonding system. These features together constitute a complete, implementable, and repeatable technical solution. Those skilled in the art, based on the description of this invention and combined with conventional sputtering equipment and process knowledge, can successfully prepare titanium-aluminum composite sputtering layers that meet performance requirements without any creative effort.

[0020] The beneficial effects of this invention are as follows: by defining a gradient structure with titanium as the base layer and aluminum as the capping layer, and combining it with an arc spraying process under local inert atmosphere protection and aluminum layer deposition in an atmospheric environment, the composite sprayed layer maintains high bonding strength (30–32 N / mm²) while reducing processing costs by 40%–50% compared to pure titanium spraying; the structure effectively avoids the oxidation problem of titanium during atmospheric spraying and avoids stress concentration at the aluminum / titanium interface due to thermal expansion mismatch. Actual measurements show that it maintains structural integrity after 500 cycles at 600 °C and 1000 hours of salt spray testing; furthermore, this method requires no vacuum equipment or complex post-processing and can be directly integrated into existing semiconductor device cavity manufacturing lines, demonstrating outstanding engineering applicability and industrialization prospects. Attached Figure Description

[0021] Figure 1 This is a schematic diagram comparing the cross-sectional structure of the titanium-aluminum composite sprayed layer of the present invention with that of the comparative single-layer aluminum sprayed layer;

[0022] The attached figures are labeled as follows:

[0023] 1. Al spray layer (covering layer of this invention); 2. Component substrate; 3. Al spray layer (comparative single-layer structure); 4. Ti spray underlayer; 5. Component substrate (comparative substrate). Detailed Implementation

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Figure 1As shown, the titanium-aluminum composite cladding layer structure provided by the present invention includes: an aluminum cladding layer (reference numeral 1) as a cover layer, a titanium cladding layer (reference numeral 4) as a base layer, and a component substrate (reference numeral 2) as a matrix. In contrast, the comparative single-layer structure only includes an aluminum cladding layer (reference numeral 3) directly deposited on another component substrate (reference numeral 5). The present invention, by placing the titanium cladding layer 4 between the substrate 2 and the aluminum cladding layer 1, forms a gradient composite structure of "titanium base layer – aluminum cover layer," thereby significantly reducing manufacturing costs while ensuring high bonding strength.

[0025] The specific implementation process of this invention is as follows: First, the substrate used for the cavity components of semiconductor devices undergoes surface pretreatment. The substrate can be one of 304 or 316L stainless steel, 6061 aluminum alloy, or Inconel 718 nickel-based alloy. Taking a 316L stainless steel plate with dimensions of 200 mm × 200 mm × 10 mm as an example, it is first placed in an alkaline degreasing solution and ultrasonically cleaned at 60 ℃ for 15 minutes to remove surface oil and organic contaminants; then it is rinsed clean with deionized water and dried in an oven at 80 ℃ for 30 minutes. Next, under a compressed air pressure of 0.6 MPa, white corundum abrasive with a particle size of 40 μm is used to sandblast the substrate surface at a sandblasting angle of 80°, with the sandblasting distance controlled at 150 mm and the treatment time approximately 3 minutes, until a uniformly distributed anchor pattern structure is obtained on the surface. Measured by a surface profilometer, the surface roughness Rz of the treated substrate reaches 120 μm, meeting the morphological requirements for subsequent mechanical bonding of the melt-applied layer.

[0026] After pretreatment, the substrate is fixed on the rotating fixture of the arc spraying equipment to ensure uniform surface heating during spraying. The arc spraying system is started, using industrial pure titanium wire with a diameter of 2.0 mm and a purity of 99.8% as the wire feeding material. An annular argon gas protective cover is installed at the front end of the spray gun outlet. The inner diameter of the cover is slightly larger than the spray gun nozzle. A high-purity argon gas source (purity ≥99.999%) is connected externally, and the argon gas flow rate is adjusted to 25 L / min to ensure that the oxygen content of the molten titanium particles ejected from the nozzle is stably controlled below 40 ppm in the flight path and the area where they impact the substrate surface. The arc current is set to 250 A, the voltage to 35 V, the spray gun moving speed to 1.0 m / min, and the spraying distance to 180 mm. Under these parameters, the titanium wire is melted by the high temperature of the arc (approximately 3500 ℃) and sprayed at high speed onto the substrate surface, forming a titanium arc-sprayed underlayer (labeled 4) with a thickness of 100 μm. During the deposition process, a laser thickness gauge was used to monitor the coating thickness in real time to ensure that the overall thickness deviation did not exceed ±8 μm. After deposition, the titanium layer surface maintained its original molten spray morphology without any grinding, polishing or heat treatment. Its surface roughness Rz remained at about 120 μm, which matched the anchor pattern structure on the substrate surface, forming an effective "primary anchoring" mechanism.

[0027] Within 3 minutes of completing the titanium spray coating deposition, the process can be directly switched to aluminum spray mode without changing tooling or transferring the workpiece. At this time, the argon protection system is shut off, allowing subsequent processes to proceed in a normal atmospheric environment. Spherical aluminum powder with a purity of 99.7% (particle size range of 30–60 μm) is used as the raw material, and aluminum layer deposition is performed using flame spraying. The fuel gas is a mixture of propane and oxygen at a volume ratio of 1:1.35, with fuel pressures of 0.4 MPa (propane) and 0.6 MPa (oxygen). The spray gun movement speed is adjusted to 1.2 m / min, and the spraying distance is 200 mm. An aluminum spray coating layer (labeled 1) is continuously deposited on the titanium surface, with a target thickness of 250 μm. Due to the high surface energy of the titanium layer (measured value approximately 1050 mN / m), the contact angle of the molten aluminum droplets upon impact is less than 25°, allowing them to fully spread and fill the micropores and grooves on the titanium surface, forming a robust "secondary nested" mechanical interlocking structure after cooling. Simultaneously, under the high temperature of the melting spray (the aluminum droplet temperature is approximately 2200 ℃), some aluminum atoms undergo short-range diffusion along the titanium grain boundaries, forming an Al-Ti micro-diffusion transition region with a thickness of approximately 3.5 μm. X-ray diffraction (XRD) analysis revealed that the main phases in this transition region are the α-Ti matrix and diffusely distributed Al3Ti intermetallic compounds. No continuous oxide phases such as TiO2 or Al2O3 were detected, indicating that the interfacial bonding is a metallurgical-mechanical composite bond without oxide inclusions.

[0028] After the aluminum layer deposition is completed, the workpiece is placed in still air for natural cooling at an ambient temperature of 25 °C and a cooling rate of approximately 3 °C / min to avoid thermal shock stress caused by rapid cooling. The entire preparation process requires no subsequent sealing, heat treatment, or surface modification steps and can proceed directly to the next assembly stage. The final titanium-aluminum composite sprayed layer has a total thickness of 350 μm, with a titanium layer thickness of 100 μm (reference 4) and an aluminum layer thickness of 250 μm (reference 1), both falling within the 80–120 μm and 200–300 μm ranges defined in this invention. Tested according to ASTM C633 standards, the average bonding strength between the composite coating and the substrate is 31.0 N / mm², significantly higher than the 24.8 N / mm² of the comparative pure aluminum sprayed layer (reference 3), and close to the theoretical lower limit of the pure titanium sprayed layer (approximately 35 N / mm²). Furthermore, after 500 thermal cycles between 600 °C and room temperature, the coating surface showed no cracks, blistering, or delamination; after 1000 hours of salt spray testing according to ASTM B117 standard, the substrate showed no signs of corrosion, proving its excellent thermal stability and corrosion resistance.

[0029] The reason this invention places the titanium layer as the bottom layer and the aluminum layer as the top layer has a clear technical logic. If, in reverse, an aluminum base layer and a titanium top layer are used (as described in CN119800271A), the titanium will rapidly oxidize to form a brittle TiO2 phase during atmospheric melting and spraying. This oxide is located at the aluminum / titanium interface, becoming a weak bonding region and severely weakening the interlayer bonding force. Simultaneously, aluminum's coefficient of thermal expansion (23 × 10⁻⁶) is... -6 / ℃) is much higher than that of titanium (8.6×10 -6 During thermal cycling, the aluminum layer shrinks more significantly, applying tensile stress to the overlying titanium layer and easily causing interfacial delamination. In contrast, this invention directly bonds a high-strength, low-thermal-expansion-coefficient titanium layer to the substrate, bearing the main mechanical load. The highly ductile (elongation > 30%) and high-roughness (Rz = 150 μm) aluminum layer serves as a functional surface layer, providing not only excellent film adsorption capacity but also absorbing thermal stress through its own ductility. The two layers complement each other under thermo-mechanical coupling, rather than antagonistically.

[0030] Furthermore, this invention employs a localized inert atmosphere protection strategy, introducing high-purity argon gas only within a 200 mm range of the spray gun exit during the titanium melting stage. This eliminates the need to place the entire workpiece in a vacuum chamber or glove box, significantly reducing equipment modification costs and energy consumption. The aluminum layer can be directly melted in the atmosphere because the Al2O3 film formed at high temperatures is self-protective, and aluminum's low melting point and good fluidity make it easy to form on the titanium layer surface. This "localized protection + atmospheric compatibility" process design allows for seamless integration into existing semiconductor equipment cavity manufacturing lines, demonstrating outstanding engineering applicability and industrialization prospects.

[0031] In summary, this invention successfully constructs a titanium-aluminum composite sprayed layer that combines high bonding strength, excellent service stability, and low cost by defining a layer sequence structure of "titanium base layer (reference 4) - aluminum capping layer (reference 1)," precisely controlling the thickness and roughness of each layer, employing arc spraying deposition of the titanium layer under local argon protection, and completing the aluminum layer deposition in an atmospheric environment. This structure... Figure 1 As clearly shown, in stark contrast to the comparative single-layer aluminum structures (reference numerals 3 and 5), this invention fully demonstrates the comprehensive innovation of the present invention in terms of interface bonding mechanism, thermal stress control, and process economy.

Claims

1. A method for preparing a titanium-aluminum composite melt-casting layer for cavity components of general semiconductor devices, characterized in that, Includes the following steps: The substrate (2) is pretreated on the surface; a titanium melt-spraying underlayer (4) is deposited on the surface of the substrate (2). The titanium melt-spraying underlayer (4) is deposited by arc melt-spraying, and a local inert atmosphere is applied to the nozzle exit area during the deposition process to make the oxygen content in the melt-spraying area less than 50 ppm. The thickness of the titanium melt-spraying underlayer (4) is 80–120 μm and the surface roughness Rz is 120 μm. An aluminum melt-spraying cover layer (1) is deposited on the titanium melt-spraying underlayer (4). The thickness of the aluminum melt-spraying cover layer (1) is 200–300 μm and the surface roughness Rz is 150 μm. By controlling the original melt-spraying morphology of the titanium melt-spraying underlayer (4) and the subsequent aluminum melt-spraying time interval, an Al-Ti micro-diffusion transition zone with a thickness of 2–5 μm is formed between the two.

2. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, The substrate (2) is one of stainless steel, aluminum alloy or nickel-based alloy, and its surface roughness Rz is 120 μm after sandblasting. The abrasive used for sandblasting is corundum or silicon carbide with a particle size of no more than 50 μm.

3. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 2, characterized in that, The compressed air pressure during the sandblasting process is 0.5–0.7 MPa, the sandblasting angle is 75°–85°, and the substrate (2) is dried at 60–80 ℃ for 30 minutes after sandblasting.

4. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, The titanium melt spraying for the underlayer (4) is deposited by electric arc melt spraying. The titanium wire used has a purity of not less than 99.5%. During the melt spraying process, a local inert atmosphere is applied to the nozzle exit area for protection. The inert atmosphere is argon gas with a purity of not less than 99.999% and a flow rate of not less than 20 L / min, so that the oxygen content in the melt spraying area is less than 50 ppm.

5. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 4, characterized in that, During the titanium melt spraying of the underlayer (4), the arc current is 200–300 A, the voltage is 30–40 V, the spray gun moving speed is 0.8–1.2 m / min, and the spraying distance is 150–200 mm. After the deposition is completed, the surface of the titanium layer retains the original melt spraying morphology and is not ground, polished or heat-treated.

6. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, The aluminum spray coating (1) is deposited in an atmospheric environment. The aluminum raw material used is aluminum wire or spherical aluminum powder with a purity of not less than 99.5%, and it is implemented by flame spraying or electric arc spraying.

7. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 6, characterized in that, When using flame spraying, the fuel gas is a mixture of propane and oxygen in a volume ratio of 1:1.2–1.5; when using arc spraying, the current is 180–250 A, the voltage is 28–35 V, the spray gun moving speed is 1.0–1.5 m / min, and the spraying distance is 180–220 mm.

8. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, The aluminum spray coating (1) begins to deposit within 5 minutes after the titanium spray underlayer (4) is deposited, and the contact angle of the aluminum droplets on the surface of the titanium layer is less than 30° during the deposition process.

9. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, After the aluminum spray coating (1) is deposited, the workpiece is naturally cooled to room temperature in still air at a rate not exceeding 5 °C / min.

10. The method for preparing the titanium-aluminum composite melt-blown layer as described in claim 1, characterized in that, The interface transition zone between the titanium melt-sprayed underlayer (4) and the aluminum melt-sprayed cover layer (1) includes a mechanical interlocking structure formed by aluminum droplets filling the micropores on the surface of the titanium layer, and a micro-diffusion phase formed by the limited solid solution diffusion of titanium and aluminum elements at the interface. X-ray diffraction analysis shows that the main phases in this transition zone are α-Ti and dispersed Al3Ti intermetallic compounds.

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