Anti-fatigue tungsten-based composite material for robot and preparation method of anti-fatigue tungsten-based composite material

Abstract

The invention provides an anti-fatigue tungsten-based composite material for a robot and a preparation method of the anti-fatigue tungsten-based composite material, and relates to the technical field of metal materials. The composite material is composed of a tungsten-lanthanum alloy core layer, a polyurethane-silicone copolymer coating and a nanoscale surface treatment layer. The lanthanum content in the tungsten-lanthanum alloy core layer is 0.25-0.85 weight percent, the thickness of the polymer coating is 5-20 microns, and the outer surface roughness Ra is less than or equal to 0.1 micron. The preparation method comprises the following steps: performing cold isostatic pressing and sintering on tungsten powder and a lanthanum compound to prepare a bar; multi-pass hot drawing is carried out, and annealing is carried out when the area reduction rate is 40%-60%; continuously drawing until the target wire diameter is 0.02 to 0.07 mm; coating a polymer solution and curing; and finally performing electrochemical polishing to form a super-smooth surface. The tensile strength of the product reaches 5500-6500 MPa, the creep rate is smaller than 0.5% after 500,000 times of stretching cycles, the product can last for more than 8 hours in a 80kg load test, and the product is particularly suitable for a high-precision robot tendon rope transmission system.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, specifically to a fatigue-resistant tungsten-based composite material for robots and its preparation method. Background Technology

[0002] Robotics technology, especially high-precision dexterous hand joints and humanoid robot tendon systems, places increasingly higher demands on the performance of transmission materials. Ideal transmission materials must simultaneously possess high tensile strength, excellent fatigue resistance, and good flexibility to ensure that they maintain a precise transmission ratio and stable mechanical properties under long-term, repeated loads.

[0003] Currently, this field mainly relies on traditional metallic and polymeric materials, but both have significant limitations. While traditional tungsten materials possess high melting points, high tensile strength, and good creep resistance, their inherent high rigidity and low elongation at break make them prone to stress concentration under dynamic bending conditions, resulting in limited fatigue life. Industry tests show that conventional pure tungsten wires, in helical bending tests simulating tendon conditions (bending radius 1mm), generally fail to meet the fatigue life requirements of high-precision joints exceeding 500,000 cycles. Furthermore, their surface micro-defects and high roughness exacerbate frictional wear with guide components.

[0004] While polymer materials such as ultra-high molecular weight polyethylene (UHMWPE) possess good flexibility and a low coefficient of friction, their creep resistance is poor, making them prone to plastic deformation under continuous loads, which affects transmission accuracy. Publicly available research data indicates that even after modification, controlling the long-term creep rate of UHMWPE materials under high constant loads remains challenging, and its absolute strength limit restricts its application in heavy-duty industrial scenarios.

[0005] Existing composite material designs attempt to combine the advantages of metal cores and polymer coatings, but often face problems such as insufficient interfacial bonding strength and easy coating peeling. For example, some metal-polymer composite wires often experience a sharp decline in performance due to interfacial failure during dynamic bending tests. In addition, during the preparation of extremely fine tungsten wires (e.g., with a diameter less than 0.1 mm), conventional drawing processes easily introduce microscopic defects into the material, which become fatigue crack initiation points, while traditional surface treatment techniques are also difficult to reliably obtain ultra-smooth surfaces to further reduce friction.

[0006] Therefore, there is an urgent need in this field for a new type of composite material and its preparation method that can synergistically address the comprehensive requirements of high strength, high fatigue resistance, good flexibility and low coefficient of friction. Summary of the Invention

[0007] The purpose of this invention is to provide a fatigue-resistant tungsten-based composite material for robots and its preparation method. The composite material consists of a tungsten-lanthanum alloy core layer, a polyurethane-silicone copolymer coating, and a nanoscale surface treatment layer.

[0008] To achieve the above objectives, the present invention provides the following technical solution: A fatigue-resistant tungsten-based composite material for robots includes a tungsten-lanthanum alloy core layer, a polymer coating covering the tungsten-lanthanum alloy core layer, and a nanoscale surface treatment layer formed by surface finishing. The lanthanum content in the tungsten-lanthanum alloy core layer is 0.25-0.85% by weight; The polymer coating is a polyurethane-silicone copolymer with a thickness of 5μm-20μm; The outer surface roughness Ra of the polymer coating is ≤0.1μm.

[0009] Furthermore, the purity of lanthanum in the lanthanum compound used to prepare the tungsten-lanthanum alloy core layer is not less than 99.99%.

[0010] Furthermore, the weight ratio of polyurethane to silicone in the polymer coating is 75:25 to 85:15.

[0011] Furthermore, the wire diameter of the composite material is 0.02mm-0.07mm.

[0012] A method for preparing the fatigue-resistant tungsten-based composite material for robots includes the following steps: a) Tungsten powder and lanthanum compound are mixed and then cold isostatically pressed and sintered to produce rods with a tungsten-lanthanum alloy core layer; b) Perform multiple passes of hot drawing at 850°C on the bar; c) Perform intermediate annealing when the drawing reaches a reduction rate of 40%-60%; d) Continue hot drawing at 850℃ to the target wire diameter; e) Coating the surface of the filament with a polyurethane-silicone copolymer solution and curing it to form a polymer coating; f) Perform surface finishing treatment on the filament with polymer coating to form a nanoscale surface treatment layer, so that its outer surface roughness Ra≤0.1μm.

[0013] Furthermore, the total number of drawing passes in steps b) and d) shall not be less than 5, and the total reduction rate shall not be less than 95%.

[0014] Furthermore, the intermediate annealing temperature in step c) is 500℃-600℃.

[0015] Furthermore, in step f), the surface finishing treatment is plasma treatment, chemical polishing, or electrochemical polishing.

[0016] Beneficial effects 1. Improved fatigue resistance This invention utilizes the synergistic effect of a tungsten-lanthanum alloy core layer and a polyurethane-silicone polymer coating to improve the fatigue resistance of the composite material while maintaining ultra-high strength. Tests show that this composite material can withstand an 80 kg load for over 8 hours without fracture, exceeding the performance of low-end fiber materials which only last for a few minutes. After 500,000 tensile cycles (load at 60% of breaking strength), the creep rate is only 0.32%-0.48%, lower than the creep rate of traditional UHMWPE materials by more than 1%. In a helical winding fatigue test simulating the actual working conditions of robot tendons (bending radius 1 mm), the fatigue life of this product reaches over 750,000 cycles, more than three times that of traditional tungsten wire, meeting the stringent requirements of long-term transmission stability for high-precision, dexterous hand joints.

[0017] 2. Dynamic adaptive optimization This invention effectively improves the adaptability of materials under dynamic bending conditions through a combination of polymer coating and nanoscale surface treatment. The polyurethane-silicone copolymer coating (elastic modulus 0.5-2.0 GPa) effectively absorbs stress during bending and reduces stress concentration; while the ultra-smooth surface (Ra≤0.1μm) obtained through electrochemical polishing reduces the coefficient of friction by 60%, reducing wear during reciprocating motion. This combined design enables the material to achieve up to 15% ductility in a helical winding structure while maintaining a tensile strength of 5500-6500 MPa, solving the problem of poor adaptability of traditional tungsten wires in miniaturized robot joints due to excessive rigidity.

[0018] 3. Enhanced interfacial bonding strength This invention achieves a strong bond between the polymer coating and the tungsten filament core layer through optimized coating formulation and surface pretreatment process. The polyurethane-silicone copolymer, formulated at a weight ratio of 75:25 to 85:15, combines the toughness of polyurethane with the lubricity of silicone, achieving a bonding strength of over 30 MPa with the tungsten filament core layer, effectively preventing delamination under long-term dynamic loads. In contrast, the interfacial bonding strength of traditional coating materials is typically below 20 MPa, and interfacial delamination may occur after tens of thousands of cycles. This strong interfacial bonding ensures effective stress transfer between the two layers, fully utilizing the high strength characteristics of the tungsten filament core layer. Test data shows that the interfacial bonding strength of Examples 1-3 all reach over 30 MPa, superior to the below 20 MPa of traditional coating materials.

[0019] 4. Good process compatibility and high product consistency This invention employs a multi-pass hot drawing and graded annealing process, combined with precisely controlled electrochemical polishing parameters, ensuring high product consistency and yield. The unique four-pass drawing process (total area reduction ≥95%), combined with intermediate annealing (500-600℃), effectively eliminates work hardening and prevents the formation of micro-cracks. Compared to traditional single cold drawing processes, this process combination increases product yield to over 95%, far exceeding the approximately 85% yield of conventional tungsten wire drawing. Furthermore, the process used in this invention is compatible with existing tungsten wire production lines; simply adding coating and polishing units in subsequent processes enables large-scale production, reducing industrialization modification costs. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a fatigue-resistant tungsten-based composite material for robots.

[0021] In the figure: 1. Tungsten-lanthanum alloy core layer, 2. Polymer coating, 3. Nanoscale surface treatment layer.

[0022] Figure 2 This is a simplified process flow diagram of a method for preparing fatigue-resistant tungsten-based composite materials for robots. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0024] Example 1 This embodiment provides a fatigue-resistant tungsten-based composite material for robots and its preparation method. The specific steps are as follows: Raw material preparation: Tungsten powder with a Fisher particle size of 3.2 μm (purity ≥99.95%) and lanthanum nitrate solution (lanthanum purity ≥99.99%) were mixed in a ratio of 99.7 wt% tungsten and 0.3 wt% lanthanum. The composite powder was prepared using a spray drying process, controlling the inlet air temperature at 180℃ and the outlet air temperature at 80℃ to ensure powder flowability, and ultimately controlling the moisture content to ≤0.5%.

[0025] Raw material preparation: The composite powder was loaded into a rubber mold and subjected to cold isostatic pressing at 200 MPa for 30 minutes. The pressed billet was placed in a sintering furnace under a hydrogen protective atmosphere and heated to 2200℃ at a rate of 10℃ / min, and held for 2 hours to obtain a tungsten alloy core layer rod (Φ5.0 mm) with a density of 99.6%.

[0026] Drawing process: Primary drawing: The bar is drawn to Φ2.3mm (55% reduction in surface area) at 850℃ using a rotary drawing machine. Intermediate annealing: Anneal at 550℃ in a hydrogen atmosphere for 40 minutes; Fine drawing: performed in four stages; One fine drawing: Φ2.3mm → Φ1.14mm (reduction rate of 75.6%); Secondary fine drawing: Φ1.14mm → Φ0.35mm (reduction in surface area 72%); Three fine drawing processes: Φ0.35mm → Φ0.20mm (surface area reduction rate 48%); Four fine drawing processes: Φ0.20mm → Φ0.05mm (94% reduction in surface area); The total reduction rate was 99.2%. Graphite emulsion was used as a lubricant during the drawing process, and the spraying amount was controlled at 5 mL / min to avoid scratches on the surface of the tungsten alloy core layer 1 due to insufficient lubrication.

[0027] Coating treatment: Prepare a polyurethane-silicone copolymer emulsion (solid content 25%, polyurethane to silicone weight ratio 80:20), pass the drawn tungsten wire through the dip coating tank at a speed of 3m / min, and treat it in a curing oven at 180℃ for 5 minutes to form a polymer coating 2 with a thickness of 12μm.

[0028] Surface treatment: The coated filament is subjected to plasma surface treatment with a power of 300W and a time of 90 seconds to obtain a nanoscale surface treatment layer 3 with a surface roughness Ra=0.08μm, which is the finished product.

[0029] Example 2 The difference between this embodiment and Embodiment 1 is that: The lanthanum content in the tungsten-lanthanum alloy core layer 1 was adjusted to 0.5 wt%. The thickness of polymer coating 2 is 8μm (polyurethane to silicone weight ratio 75:25); The final wire diameter is 0.03mm; The polymer coating 2 is subjected to surface finishing treatment (using chemical polishing) for 35 seconds to form a nanoscale surface treatment layer 3.

[0030] The remaining steps and process parameters are the same as in Example 1.

[0031] Example 3 The difference between this embodiment and Embodiment 1 is that: The lanthanum content in the tungsten-lanthanum alloy core layer was adjusted to 0.8 wt%. The thickness of polymer coating 2 is 18μm (polyurethane to silicone weight ratio 85:15). The final wire diameter is 0.07mm; The cold isostatic pressing pressure for preparing the tungsten-lanthanum alloy core layer 1 was 180 MPa, and the sintering temperature was 2300℃. Annealing temperature 500℃; The remaining steps and process parameters are the same as in Example 1.

[0032] Comparative Example 1 Pure tungsten powder (lanthanum-free) was used, and after cold isostatic pressing (200 MPa) and sintering (2200℃), it was directly drawn to Φ0.05 mm in multiple passes. No polymer coating treatment 2 or nanoscale surface treatment layer 3 was applied; the drawing process was the same as in Example 1.

[0033] Comparative Example 2 The tungsten-lanthanum alloy core layer 1 and polymer coating 2 were prepared according to the formulation and process of Example 1, but the surface finishing step was omitted after the polymer coating 2 was cured (no nanoscale surface treatment layer 3 was formed), and the surface roughness Ra=0.35μm. Comparative Example 3 The tungsten-lanthanum alloy core layer 1 was prepared using the same tungsten-lanthanum alloy billet (Φ5.0 mm) as in Example 1, and processed using a cold rotary forging machine. It was forged to Φ2.3 mm (55% reduction in surface area) at room temperature through multiple passes, and then processed to Φ0.05 mm using the same drawing process as in Example 1. Following this, a polymer coating 2 and a nanoscale surface treatment layer 3 were prepared. The cold rotary forging process resulted in residual stress and microcracks within the tungsten alloy core layer 1, which became fatigue crack initiation points, thus leading to poor performance.

[0034] The materials prepared in the above embodiments and comparative examples were subjected to performance tests, and the results are shown in Table 1.

[0035] Test method: Tensile strength: According to ASTM E8 standard, using a universal testing machine.

[0036] Elongation: According to ASTM E8 standard, gauge length 100mm.

[0037] Fatigue life: Helical bending test (bending radius 1mm), record the number of cycles until fracture.

[0038] Creep rate: The rate of change in length after 500,000 tensile cycles (load of 60% of breaking strength).

[0039] Surface roughness: Measured using a white light interferometer.

[0040] Table 1: Performance Test Results Test results show that the composite materials prepared in Examples 1-3 of this invention are superior to the comparative examples in terms of tensile strength, elongation, fatigue life, and creep resistance. In particular, the fatigue life reaches more than 750,000 cycles, which is much higher than that of Comparative Example 1 (180,000 cycles) and Comparative Example 3 (220,000 cycles), proving that this invention effectively improves the fatigue resistance of the material through the synergistic effect of the material composition and process of the core layer, coating layer, and surface treatment layer.

[0041] Furthermore, in the 80 kg load endurance test, Examples 1-3 all maintained their fatigue life for more than 8 hours without fracture, while Comparative Examples 1 and 3 only maintained it for 12 minutes and 25 minutes, respectively. Comparative Example 2, lacking a nanoscale surface treatment layer, had a higher coefficient of friction and a significantly shorter fatigue life than the Examples. A schematic diagram of a fatigue-resistant tungsten-based composite material for robots is shown below. Figure 1 A simplified process flow diagram of a method for preparing fatigue-resistant tungsten-based composite materials for robots is shown below. Figure 2 .

[0042] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection. Various modifications and variations made by those skilled in the art within the scope defined in the claims are all within the scope of protection of the present invention.

Claims

1. A fatigue-resistant tungsten-based composite material for robots, characterized in that: It includes a tungsten-lanthanum alloy core layer (1), a polymer coating (2) covering the tungsten-lanthanum alloy core layer (1), and a nanoscale surface treatment layer (3) formed by surface finishing. The lanthanum content in the tungsten-lanthanum alloy core layer (1) is 0.25-0.85% by weight; The polymer coating (2) is a polyurethane-silicone copolymer with a thickness of 5μm-20μm; The outer surface roughness Ra of the polymer coating (2) is ≤0.1μm.

2. The fatigue-resistant tungsten-based composite material for robots according to claim 1, characterized in that: The purity of lanthanum in the lanthanum compound used to prepare the tungsten-lanthanum alloy core layer (1) is not less than 99.99%.

3. The fatigue-resistant tungsten-based composite material for robots according to claim 1, characterized in that: The weight ratio of polyurethane to silicone in the polymer coating (2) is 75:25 to 85:

15.

4. The fatigue-resistant tungsten-based composite material for robots according to claim 1, characterized in that: The wire diameter of the composite material is 0.02mm-0.07mm.

5. A method for preparing a fatigue-resistant tungsten-based composite material for robots as described in any one of claims 1-4, characterized in that, Includes the following steps: a) Tungsten powder and lanthanum compound are mixed and then cold isostatically pressed and sintered to form a rod with a tungsten-lanthanum alloy core layer (1); b) Perform multiple passes of hot drawing at 850°C on the bar; c) Perform intermediate annealing when the drawing reaches a reduction rate of 40%-60%; d) Continue hot drawing at 850℃ to the target wire diameter; e) Coating the surface of the filament with a polyurethane-silicone copolymer solution and curing it to form a polymer coating (2); f) The filament with polymer coating (2) is surface-finished to form a nanoscale surface treatment layer (3) so that its outer surface roughness Ra≤0.1μm.

6. The preparation method according to claim 5, characterized in that: The total number of drawing passes in steps b) and d) shall not be less than 5, and the total reduction rate shall not be less than 95%.

7. The method for preparing the fatigue-resistant tungsten-based composite material for robots according to claim 5, characterized in that: The intermediate annealing temperature in step c) is 500℃-600℃.

8. The method for preparing the fatigue-resistant tungsten-based composite material for robots according to claim 5, characterized in that: In step f), the surface finishing treatment is plasma treatment, chemical polishing, or electrochemical polishing.

Images