Ti-6Al-4V alloy lattice structure solid lubrication composite material and preparation method thereof

Abstract

The invention discloses a Ti-6Al-4V alloy lattice structure solid lubrication composite material which comprises a solid matrix layer on the lower portion and a lattice structure layer located on the upper portion of the solid matrix layer, and the solid matrix layer is made of Ti-6Al-4V alloy; the lattice structure layer is obtained by forming a framework of a lattice structure by a Ti-6Al-4V alloy and filling pores formed by the framework with a Sn-Ag-Cu-In alloy solid lubricant. A lattice structure and a Sn-Ag-Cu-In multiphase solid lubricant are integrated in a Ti-6Al-4V matrix through a multi-material LPBF process, so that the characteristics of high strength and light weight of the material are ensured, the antifriction and antiwear properties of the material in a lubrication-lacking environment and under a high-load working condition are also remarkably improved, the integrated design of the bearing property and the lubricating function is realized, and the service life of the material is prolonged. Compared with a traditional lubricating and coating technology, the lubricating oil has better long-term stability and higher wear resistance, the service life of key components of the aero-engine can be remarkably prolonged, and the reliability of the key components of the aero-engine can be improved.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology for metallic materials, specifically to a Ti-6Al-4V alloy lattice structure solid lubricating composite material and its preparation method. Background Technology

[0002] As aero-engine technology advances towards higher thrust-to-weight ratios and higher reliability, key components such as compressor blades and turbine blades endure harsh conditions during service, including high-speed rotation, cyclic frictional contact, and vibration shocks. Especially under high temperature, high speed, and impact load conditions, the lubricating film is prone to failure, leading to "lack of lubrication," which in turn causes adhesive wear, material spalling, and friction pair failure, severely impacting engine safety and service life. Traditional solutions to address this challenge include external lubrication, solid lubricant coatings, and surface alloying. However, these methods suffer from drawbacks under high temperature, high speed, and impact load conditions, such as rapid lubricant loss, coating spalling, or reduced substrate strength, making it difficult to provide long-term stable lubrication and reliable protection.

[0003] Due to its lightweight and high-strength properties, Ti-6Al-4V alloy is widely used in key components of aero-engines, such as compressor blades and turbine blades. These components require extremely high wear resistance and fatigue resistance. In existing technologies, Ti-6Al-4V alloys are typically improved in terms of friction performance through surface treatment methods such as surface alloying and laser cladding. Lubrication improvements are also achieved by applying solid lubricants to the surface. However, although these methods improve the friction performance of Ti-6Al-4V alloys to some extent, they still face problems such as a high coefficient of friction and poor wear resistance after lubrication film failure in low-lubrication environments. Summary of the Invention

[0004] This invention addresses the technical problems of adhesive wear, lubricant film failure, coating peeling, and lubricant loss in Ti-6Al-4V alloy components under oil-deficient lubrication conditions. It proposes a Ti-6Al-4V alloy lattice structure solid lubricating composite material and its preparation method, which enables the material to maintain excellent load-bearing and self-lubricating properties under high load, intermittent oil supply, or oil-free conditions, while also meeting the requirements for lightweighting.

[0005] The technical solution adopted by the present invention to solve the above-mentioned problems is as follows: A Ti-6Al-4V alloy lattice structure solid lubricant composite material includes a lower solid matrix layer and a lattice structure layer located above the solid matrix layer. The solid matrix layer is a Ti-6Al-4V alloy. The lattice structure layer is formed by using Ti-6Al-4V alloy to form the lattice structure skeleton, and Sn-Ag-Cu-In alloy solid lubricant is used to fill the pores formed by the skeleton.

[0006] According to the above scheme, the lattice structure layer is formed by arranging single-cell units in a single layer, with an array size of M×N×1, where 1 represents a single-cell unit layer vertically and an M×N array horizontally, and M and N are both integers greater than 2 (preferably both greater than 5). The side length of each single-cell unit is 1–3 mm, and the single-cell lattice is body-centered cubic (BCC) or face-centered cubic (FCC) with a porosity of 30%–70%. The framework of the single-cell lattice is formed of Ti-6Al-4V alloy, and Sn-Ag-Cu-In alloy solid lubricant fills the pores formed by the framework. This lattice structure layer provides sufficient storage and release space for the lubricant while ensuring the mechanical support capability of the lattice structure itself.

[0007] According to the above scheme, the composition of the Ti-6Al-4V alloy by mass percentage is: Al 5%~6.75%, V 3.5%~4.5%, Fe≤0.3%, C≤0.1%, Si≤0.12%, others≤0.4%, and the balance is Ti.

[0008] According to the above scheme, the composition of the Sn-Ag-Cu-In solid lubricant by mass percentage is: Sn 90%~95%, Ag 2%~4%, Cu 0.5%~1.5%, In 2%~5%.

[0009] According to the above scheme, the Sn-Ag-Cu-In solid lubricant is a spherical powder with an average particle size of 30-40 μm, a particle sphericity of ≥85% and uniform distribution, which can ensure uniform accumulation in the lattice pores and stable melting under subsequent laser action and reliable bonding with the lattice pore walls.

[0010] According to the above scheme, the thickness of the solid substrate layer is 2 to 3 mm.

[0011] The preparation method of the above-mentioned Ti-6Al-4V alloy lattice structure solid lubricant composite material includes the following steps: according to the preset model of the Ti-6Al-4V alloy lattice structure solid lubricant composite material, namely the structural design of the solid matrix layer and the lattice structure layer, a multi-material laser powder bed melting process is used to prepare the skeleton of the solid matrix layer and the lattice structure layer with Ti-6Al-4V alloy powder; in this process, Sn-Ag-Cu-In alloy solid lubricant powder is directionally fed into the pore region of the lattice structure, and a low-energy laser is used to selectively melt the lubricant region, so that the Sn-Ag-Cu-In lubricant melts in situ and combines with the Ti-6Al-4V alloy skeleton to obtain the lubricant-filled lattice composite material.

[0012] The above preparation method employs multi-material laser powder bed melting (LPBF) integrated forming, using multi-material configuration equipment with dual powder feeding and selective powder suction functions. For example...Figure 4 As shown, during the printing process, Ti-6Al-4V alloy powder is oriented and laid in the solid area and lattice framework area through a powder feeding tube. Under the action of a high-power laser, it completely melts and densifies, constructing a supporting matrix structure. Sn-Ag-Cu-In lubricant powder is oriented and laid in the lattice pore area through another powder feeding tube. Under low energy density laser parameters, it locally melts and rapidly solidifies. During this process, a suction tube simultaneously removes lubricant powder from non-target areas, thereby avoiding cross-contamination between different powders and ensuring clear spatial partitioning between the lubricant, the solid matrix, and the lattice framework. Through this process, Sn-Ag-Cu-In solid lubricant can be directly embedded in situ into the lattice pores during printing, achieving a firm bond with the solid matrix and the lattice framework.

[0013] Compared to the traditional method of printing the substrate and then filling it with lubricant, this invention achieves integrated forming of the load-bearing and lubrication zones through a multi-material LPBF process and a dual powder feeding / suction method, avoiding problems such as uneven lubricant filling, insufficient interfacial bonding, and easy loss during service. This invention effectively overcomes the difficulties of low-melting-point Sn-Ag-Cu-In lubricants easily undergoing overall melting, volatilization, and excessive reaction with Ti alloys under high-energy laser conditions. It allows the lubricant to remain in a stable form within the lattice pores, and during friction, it is gradually and slowly released to the friction interface, dominated by the Sn-In soft phase, forming a continuous lubricating film. This maintains good friction-reducing and anti-wear performance under conditions of insufficient lubrication and high load.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: First, the Ti-6Al-4V alloy lattice structure solid lubricant composite material of this invention constructs an in-situ lattice structure with open-pore characteristics within a Ti-6Al-4V alloy matrix. The framework of this lattice structure is formed by a high-melting-point Ti-6Al-4V alloy, ensuring overall load-bearing capacity. The lattice pores are formed by introducing Sn-Ag-Cu-In solid lubricant powder, which undergoes local melting and solidification under low-energy laser irradiation, thus firmly bonding with the lattice framework. This lattice structure provides a three-dimensional storage and slow-release space for the lubricant. When friction occurs, the lubricant is gradually released to the friction interface under shear force and frictional heat, forming a stable self-lubricating film, effectively reducing the coefficient of friction and wear. Compared with traditional surface coatings or post-filled lubricants, this "in-situ forming of lattice structure and solid lubricant" method significantly extends the lubricant's action time, enabling the material to maintain excellent friction-reducing and anti-wear properties even under low-oil lubrication and high-load conditions, effectively avoiding failure problems caused by lubricant loss or coating peeling.

[0015] Secondly, this invention introduces a lattice structure with a certain porosity and unit cell size into the Ti-6Al-4V alloy, and combines it with built-in solid lubricating materials, which can effectively maintain the lightweight of parts while improving friction reduction and wear resistance. This invention utilizes a multi-material laser powder bed melting process to construct a lattice structure in situ within the Ti-6Al-4V matrix. By adjusting geometric parameters such as porosity and unit cell size, a balance between mechanical properties and lightweight is achieved. While maintaining the overall mechanical strength of the composite material, the mass of the composite material is significantly reduced, achieving a unity of load-bearing capacity and lightweight. It meets load-bearing requirements while also considering friction reduction, making it particularly suitable for key components of aero-engines with stringent requirements for structural strength and weight reduction.

[0016] Third, this invention introduces 2%–5% In element into the Sn-Ag-Cu-In system to form a Sn-Ag-Cu-In multiphase solid lubricant alloy, which can form a Sn-In soft phase. The Sn-In soft phase has lower shear strength and better spreading ability at the friction interface, and is more likely to form a continuous and dense metal lubricating film under shear force and frictional heat. In addition, it inhibits the instantaneous extrusion or complete compaction of the lubricant under high load, thereby significantly extending the effective action time of the lubricant while maintaining a low coefficient of friction. The Sn-Ag-Cu-In multiphase lubricating alloy of this invention, combined with the lattice three-dimensional storage structure and the multi-material LPBF in-situ forming process, enables the lubricant to be stably embedded during the forming stage and gradually released during the service stage, which is significantly better than the traditional single Sn-Ag-Cu lubricant, which is prone to melting, volatilization or failure under high load and low oil conditions.

[0017] In summary, this invention integrates a lattice structure and a Sn-Ag-Cu-In multiphase solid lubricant into a Ti-6Al-4V matrix using a multi-material LPBF process. This not only ensures the material's high strength and lightweight characteristics but also significantly improves its friction reduction and wear resistance under low-lubrication environments and high-load conditions. It achieves an integrated design of load-bearing performance and lubrication function. Compared with traditional lubrication and coating technologies, it has better long-term stability and higher wear resistance, which can significantly extend the service life of key components of aero-engines and improve their reliability. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structure of a single BCC cell in Embodiment 1 of the present invention when it is not filled with solid lubricant; wherein, the framework is formed of Ti-6Al-4V alloy, and the pores between the framework are used to fill solid lubricant, thereby forming a single cell that constitutes the lattice structure layer.

[0019] Figure 2This is a schematic diagram of the Ti-6Al-4V alloy lattice structure described in Embodiment 1 of the present invention; wherein, (a) is a front view, (b) is a side view, (c) is a top view, and (d) is an isometric view.

[0020] Figure 3 This is a schematic diagram of the Ti-6Al-4V alloy lattice structure solid lubricating composite material described in Embodiment 1 of the present invention; wherein, (a) is a front view, (b) is a side view, (c) is a top view, and (d) is an isometric view.

[0021] Figure 4 This is a schematic diagram of the dual powder delivery / powder suction system used in Embodiment 1 of the present invention.

[0022] Figure 5 These are the SEM and EDS images of the Ti-6Al-4V alloy lattice structure solid lubricating composite material described in Example 1 of this invention.

[0023] Figure 6 It is the coefficient of friction of the Ti-6Al-4V alloy lattice structure solid lubricating composite material described in Example 1 of the present invention as a function of time under a 10N load.

[0024] Figure 7 The average wear amount of the Ti-6Al-4V alloy lattice structure solid lubricating composite material and the control sample described in Example 1 of this invention varies with time under different loads, where Ti-6Al-4V represents the control sample and BCC represents Example 1. Detailed Implementation

[0025] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the present invention is not limited to the following embodiments.

[0026] In the following examples, the chemical composition of the Ti-6Al-4V alloy powder is as follows: Al 5-6.75 wt.%, V 3.5-4.5 wt.%, Fe ≤0.3 wt.%, C ≤0.1 wt.%, Si ≤0.12 wt.%, other impurities ≤0.4 wt.%, and Ti as the balance. This Ti-6Al-4V alloy powder can be prepared by plasma atomization, with a particle size distribution controlled between 15 and 45 μm, an average particle size of approximately 30 μm, a loose packing density of approximately 2.5 g / cm³, and good sphericity, making it suitable for selective laser melting.

[0027] In the following embodiments, the Sn-Ag-Cu-In solid lubricant powder used was prepared by the following method: First, each elemental metal raw material was weighed according to the mass percentages of Sn 90%–95%, Ag 2%–4%, Cu 0.5%–1.5%, and In 2%–5%. Inert gas was introduced into a vacuum induction furnace for protection, and the mixture was heated and melted to form a Sn-Ag-Cu-In alloy melt with uniform composition. The melting temperature was 50–100 °C higher than the alloy liquidus temperature, and the mixture was then refined and held at that temperature. Subsequently, the alloy melt was introduced into a gas atomizing device via bottom injection and subjected to high-pressure atomization cooling under Ar gas pressure of 5 MPa to obtain spherical Sn-Ag-Cu-In alloy powder with an average particle size of 30–40 μm. The particle size distribution was controlled by sieving to ensure that the sphericity of the powder was not less than 0.85. The obtained spherical Sn-Ag-Cu-In alloy powder was subjected to low-temperature aging treatment at 150–220 °C for 0.5–2 h in an inert atmosphere to obtain Sn-Ag-Cu-In solid lubricant powder with good fluidity and forming stability, which was used in subsequent embodiments.

[0028] Example 1 A Ti-6Al-4V alloy lattice structure solid lubricating composite material includes a solid matrix layer and a lattice structure layer located on the solid matrix layer; the solid matrix layer is a Ti-6Al-4V alloy with a thickness of 2 mm, used to ensure the overall load-bearing strength; the lattice structure layer is composed of body-centered cubic single-cell lattices (i.e., single cells) arranged in an array scale of 5×7×1, the cross-sectional size of the entire lattice structure layer is 10×14 mm, and the side length of the single cell is 2 mm.

[0029] like Figure 1 As shown, the single cell is a body-centered cubic lattice, including a cubic framework structure and prisms extending from the body center of the cube to the eight vertices, which together form the skeleton of the single cell lattice. The skeleton has a three-dimensional open array feature. The non-skeleton part (i.e., pores) is used to fill Sn-Ag-Cu-In alloy solid lubricant. The porosity of the single cell is controlled at 80-85%.

[0030] The preparation method of the above-mentioned Ti-6Al-4V alloy lattice structure solid lubricating composite material includes the following steps: based on the preset three-dimensional model of the Ti-6Al-4V alloy lattice structure solid lubricating composite material, its structure is divided into a lower solid matrix layer and an upper lattice structure layer. In the slicing software, the lattice structure layer is further divided into two material domains: the skeleton voxel domain (Ti-6Al-4V only) and the porous voxel domain (Sn-Ag-Cu-In only). Two sets of process parameter libraries are established simultaneously. Then, a multi-material selective laser melting device (such as Fraunhofer IGCV+SLM 280) is used to prepare the solid matrix layer and the skeleton of the lattice structure layer with Ti-6Al-4V alloy powder. In this process, Sn-Ag-Cu-In alloy solid lubricant powder is directionally fed into the porous voxel domain of the lattice structure. The lubricant is composed of Sn 94.5%, Ag 3%, Cu 0.5%, and In 2% by mass percentage. Subsequently, the porous voxel domain is selectively melted using a low-energy laser, causing the Sn-Ag-Cu-In lubricant to undergo local shallow melting and rapid solidification, thereby forming a stable bond with the pore walls of the Ti-6Al-4V lattice framework, resulting in a lubricant-filled lattice composite material.

[0031] The forming parameters for the solid matrix region and the voxel domain of the lattice framework are as follows: laser power 500 W, support scanning speed 2000 mm / s, filling scanning speed 1200 mm / s, contour scanning speed 1100 mm / s, layer thickness 0.04 mm, argon gas protection throughout, and oxygen content in the cavity ≤0.02%; the forming parameters for the voxel domain of the lattice pores are as follows: laser power 300 W, scanning speed 1000 mm / s, and the melting depth of the Sn-Ag-Cu-In lubricant region is controlled at δ=150 μm to achieve local melting and solidification of the lubricant and avoid excessive melting loss and elemental ablation.

[0032] like Figure 5 As shown, the SEM morphology and EDS elemental distribution of the Ti-6Al-4V alloy lattice structure solid lubricant composite material obtained in Example 1 are shown. Sn is continuously and uniformly distributed in the pore-filling region, while Ti is significantly reduced in this region and concentrated in the skeleton region. No obvious element agglomeration or stratification is observed, indicating that the lubricant is fully and uniformly filled and has good bonding with the Ti-6Al-4V alloy.

[0033] The performance of the Ti-6Al-4V alloy lattice structure solid lubricated composite material obtained in Example 1 was tested. The test used an MFT-5000 multi-functional friction testing machine, equipped with Si3N4 ceramic balls with a diameter of 6 mm and a hardness of 1400–1700 HV as the grinding pair. The friction mode was ball-disc reciprocating motion, and dry friction tests were conducted without any lubricating oil or grease to simulate the insufficient lubrication condition of critical components in aero-engines. The test conditions were: room temperature 20–26 ℃, relative humidity 40%–60%, loads of 10 N, 15 N, and 20 N, stroke 8 mm, frequency 1 Hz, and time 60 min. The test results are as follows: Figure 6 and Figure 7 As shown, compared with the pure solid Ti-6Al-4V control sample, the friction coefficient of the Ti-6Al-4V alloy lattice structure solid lubricated composite material obtained in Example 1 is significantly reduced under different loads, and the wear volume is reduced by about 18% to 29%, exhibiting good tribological properties.

[0034] Example 2 The difference between Example 2 and Example 1 is that: the thickness of the solid substrate layer is 3 mm, the edge length of the single crystal cell is 1.5 mm, the array size is 6×8×1, and the cross-sectional size of the entire lattice structure layer is 9×12 mm; the Sn-Ag-Cu-In solid lubricant powder is composed of Sn 95%, Ag 2.5%, Cu 0.5%, and In 2% by mass percentage; and the laser power of the voxel domain of the lattice pores is 260 W.

[0035] Example 3 The difference between Example 3 and Example 1 is that the solid lubricant filling the lattice porous voxel domain is composed of Sn-Ag-Cu-In alloy, which consists of Sn 92%, Ag 3%, Cu 1%, and In 4% by mass percentage; the laser power of the lattice porous voxel domain is 280 W, the scanning speed is 900 mm / s, and the other conditions are the same as in Example 1.

[0036] Example 4 The difference between Example 4 and Example 1 is that the scanning speed of the lattice pore voxel domain is 800 mm / s.

[0037] Example 5 The difference between Example 5 and Example 1 is that the body-centered cubic (BCC) lattice of the unit cell is replaced with a face-centered cubic (FCC) structure, while the other parameters are the same as in Example 1.

[0038] The above are merely exemplary embodiments of the present invention and do not constitute any limitation on the scope of protection of the present invention. All technical solutions formed by equivalent exchange or substitution fall within the scope of protection of the present invention.

Claims

1. A Ti-6Al-4V alloy lattice structure solid lubricating composite material, characterized in that, It includes a lower solid substrate layer and a lattice structure layer located above the solid substrate layer. The solid substrate layer is a Ti-6Al-4V alloy. The lattice structure layer is formed by using Ti-6Al-4V alloy to form the lattice structure framework, and filling the pores formed by Sn-Ag-Cu-In alloy solid lubricant.

2. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The lattice structure layer is formed by arranging single cells in a single layer to form a lattice structure layer. The array size is M×N×1, where 1 represents a single-layer single cell in the vertical direction and an M×N array in the horizontal direction. M and N are both integers greater than 2.

3. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The side length of the single cell is 1 to 3 mm; the lattice of the single cell is body-centered cubic or face-centered cubic with a porosity of 30% to 70%; the framework of the single cell lattice is formed by Ti-6Al-4V alloy, and Sn-Ag-Cu-In alloy solid lubricant fills the pores formed by the framework.

4. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The composition of the Ti-6Al-4V alloy by mass percentage is: Al 5%~6.75%, V 3.5%~4.5%, Fe≤0.3%, C≤0.1%, Si≤0.12%, other ≤0.4%, with the balance being Ti; the Ti-6Al-4V alloy powder is spherical, with a particle size distribution controlled between 15 and 45 μm.

5. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The Sn-Ag-Cu-In solid lubricant has the following composition by mass percentage: Sn 90%~95%, Ag 2%~4%, Cu 0.5%~1.5%, In 2%~5%.

6. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The Sn-Ag-Cu-In solid lubricant is a spherical powder with an average particle size of 30-40 μm and a particle sphericity ≥85%.

7. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The preparation method of the Sn-Ag-Cu-In solid lubricant powder includes the following steps: (1) Weigh out each elemental metal raw material according to the mass percentage of Sn 90%~95%, Ag 2%~4%, Cu 0.5%~1.5% and In 2%~5%, respectively, pass in inert gas into a vacuum induction furnace for protection, and then heat and melt and refine it at a temperature 50~100 ℃ higher than the alloy liquidus temperature, and hold it at the temperature to form a Sn-Ag-Cu-In alloy melt with uniform composition; (2) The alloy melt is subjected to high-pressure atomization and cooled to room temperature to obtain spherical Sn-Ag-Cu-In alloy powder with an average particle size of 30-40 μm and a powder sphericity of not less than 0.85; (3) The obtained spherical Sn-Ag-Cu-In alloy powder is subjected to low-temperature aging treatment at 150-220 °C for 0.5-2 h in an inert atmosphere to obtain the Sn-Ag-Cu-In solid lubricant powder.

8. The Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, The thickness of the solid substrate layer is 2 to 3 mm.

9. A method for preparing the Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 1, characterized in that, Includes the following steps: According to the pre-designed model of the Ti-6Al-4V alloy lattice structure solid lubricant composite material, namely the structural design of the solid matrix layer and the lattice structure layer, a multi-material laser powder bed melting process is adopted to prepare the skeleton of the solid matrix layer and the lattice structure layer with Ti-6Al-4V alloy powder. In this process, Sn-Ag-Cu-In alloy solid lubricant powder is directionally fed into the pore region of the lattice structure, and the lubricant region is selectively melted by laser to melt the Sn-Ag-Cu-In lubricant in situ and combine it with the Ti-6Al-4V alloy skeleton to obtain the Ti-6Al-4V alloy lattice structure solid lubricant composite material.

10. The method for preparing the Ti-6Al-4V alloy lattice structure solid lubricating composite material according to claim 9, characterized in that, The forming parameters for the solid substrate region and the lattice framework are as follows: laser power 400–600 W, support scanning speed 1800–2200 mm / s, filling scanning speed 1150–1250 mm / s, contour scanning speed 1050–1150 mm / s, layer thickness 0.03–0.05 mm, inert gas protection throughout, and oxygen content in the cavity ≤0.02%; the forming parameters for the lattice pores are as follows: laser power 250–350 W, scanning speed 800–1000 mm / s, and the melting depth of the Sn-Ag-Cu-In lubricant region is controlled at 50–200 μm.

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