Corrosion-resistant spoke forming process

Abstract

The invention discloses a corrosion-resistant spoke forming process which comprises the following steps: firstly, refining an austenitic stainless steel wire into an ultra-fine grain / nanocrystalline structure through equal-channel angular extrusion in combination with low-temperature rolling, and improving the grain boundary density; then, surface pollutants are sequentially removed by adopting pulse fiber laser, an amorphous / nanocrystalline mixed activation layer is formed, and the surface activity is enhanced; mixed reaction gas is introduced into a closed reaction chamber, a gradient composite permeation layer composed of a ceramic phase outer layer, a mixed middle layer and a Cr / Ni-rich inner layer is formed at the temperature of 450-650 DEG C, and metallurgical bonding with a base body is achieved; finally, a porous ceramic membrane is generated on the surface of the permeation layer, and an indicator sensitive to Cl <-> or pH is filled through vacuum impregnation, so that the corrosion early warning function is achieved. The gradient infiltrated layer binding force critical load of the spoke obtained through the method is larger than or equal to 80 N, the salt spray test corrosion resistance time is larger than or equal to 2000 hours, and the spoke has the self-repairing capacity and the rapid corrosion early warning response, is suitable for various scenes such as bicycles, automobiles and ocean engineering and has the remarkable industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of spoke processing technology, and more specifically, relates to a corrosion-resistant spoke forming process. Background Technology

[0002] Spokes have a wide range of applications, generally serving as a key component of bicycle wheel hubs. They are also used in various other scenarios such as automobiles and marine engineering. However, prolonged exposure to corrosive environments such as humidity and salt spray makes them susceptible to pitting corrosion and stress corrosion cracking. Traditional spokes are mostly made of austenitic stainless steel (such as 304L or 316L), but conventional processes result in a coarse grain structure and low grain boundary density, limiting their corrosion resistance. Furthermore, existing surface treatment technologies (such as electroplating and spraying) often form a single coating with weak adhesion to the substrate, making it prone to peeling and unable to monitor corrosion status in real time.

[0003] To improve corrosion resistance, some processes employ surface modification techniques, such as chemical vapor deposition (CVD) or physical vapor deposition (PVD). However, these methods involve high processing temperatures, which can easily lead to substrate deterioration and poor coating uniformity. Other processes attempt to introduce self-monitoring functions, but these are mostly implemented through external sensors, resulting in complex structures and high costs. Therefore, there is an urgent need for an integrated molding process that can improve the performance of the spoke substrate while forming a gradient composite diffusion layer and a self-monitoring functional layer, achieving long-term corrosion protection and early corrosion monitoring. Summary of the Invention

[0004] In view of this, the technical problem to be solved by the present invention is to provide a corrosion-resistant spoke forming process, which solves the problems of insufficient corrosion resistance of spokes, poor coating adhesion and lack of corrosion monitoring function in the prior art by optimizing the steps of substrate pretreatment, laser activation, vapor phase infiltration deposition and micro-arc oxidation.

[0005] To address the aforementioned technical problems, this invention discloses a corrosion-resistant spoke forming process, comprising: S1. Substrate pretreatment: Austenitic stainless steel wire is selected and ultrafine grain or nanocrystalline structure is obtained through a violent plastic deformation process. The grain size of the ultrafine grain or nanocrystalline structure is 100nm-5μm, and the grain boundary density is increased by 10-15 times compared with the original substrate. S2. Laser Cleaning and Activation: The spokes pretreated in step S1 are scanned using a pulsed fiber laser, initially at a speed of 0.5-1.5 J / cm². 2 Surface contaminants are removed using an energy density and a scanning speed of 500-1000 mm / s, followed by a process of 2-5 J / cm². 2 The energy density and scanning speed of 100-300 mm / s enable the formation of an amorphous / nanocrystalline hybrid activation layer in the 5-20 μm region of the spoke surface, with a dislocation density ≥102.14 m -2 Vacancy concentration ≥10 20 cm -3 ; S3. In-situ reactive vapor infiltration deposition: The spokes activated in step S2 are placed in a sealed reaction chamber and evacuated to ≤1×10⁻⁶. -4 After Pa, a mixed reaction gas is introduced, and the mixture is heated at 450-650℃ for 2-4 hours to allow the reaction gas to undergo a chemical reaction on the spoke surface and diffuse towards the surface layer, forming a gradient composite diffusion layer. The mixed reaction gas includes a metal-organic compound gaseous precursor, a non-metallic reaction gas, and a carrier gas. The gradient composite diffusion layer consists of a dense ceramic phase outer layer, a mixed intermediate layer of ceramic and intermetallic compounds, and a Cr / Ni rich alloy diffusion inner layer from the outside to the inside, with a total thickness of 50-100 μm. S4. Integration of Micro-arc Oxidation and Self-Early Warning Function: The spokes with gradient composite infiltration layers obtained in step S3 are subjected to micro-arc oxidation treatment to generate a porous ceramic membrane with a thickness of 10-30 μm on the surface of the infiltration layer. Then, the micropores of the porous ceramic membrane are filled with chlorine using vacuum impregnation technology. - Or a pH-sensitive indicator to form a corrosion self-warning functional layer.

[0006] Further, in step S1, the austenitic stainless steel wire is 304L or 316L, wherein 304L has a Cr content of 18-20% and a Ni content of 8-12%, and 316L has a Cr content of 16-18%, a Ni content of 10-14%, and a Mo content of 2-3%; the intense plastic deformation process is equal channel angle extrusion combined with low temperature rolling, wherein the inner angle of the die for equal channel angle extrusion is 90° and the outer angle is 30°, the extrusion temperature is 250-350℃, the extrusion rate is 5-10mm / s, and the number of extrusion passes is 4-8; the cumulative reduction rate of low temperature rolling is 30-50%, and the rolling temperature is 100-150℃.

[0007] In a further step S2, the wavelength of the pulsed fiber laser is 1064 nm, the pulse width is 10-100 ns, the repetition frequency is 10-100 kHz, and the maximum single pulse energy is 50 mJ; the laser scanning spot diameter is 50-100 μm, the spot overlap rate in the surface nano-sizing stage is 50-70%, and the number of scans is 2-3.

[0008] Furthermore, the organometallic gaseous precursor includes titanium tetrachloride (TiCl4) and chromium trichloride (CrCl3), wherein TiCl4 is vaporized by heating to 80-100℃, and CrCl3 is introduced in the form of an aerosol at a concentration of 5-10 g / m³. 3The non-metallic reactive gases include nitrogen (N2), acetylene (C2H2), and silane (SiH4), all with a purity ≥99.9%; the carrier gas is argon (Ar) with a purity ≥99.999%.

[0009] Furthermore, the volume ratio of the mixed reaction gases is: TiCl4:CrCl3 aerosol:N2:C2H2:SiH4:Ar = (5-8):(2-3):(30-40):(10-15):(5-10):(30-40), and the total flow rate is 500-1000 sccm.

[0010] Further, in step S3, the thickness of the dense ceramic phase outer layer is 5-10 μm, and the main components are titanium nitride (TiN), titanium carbide (TiC) and chromium carbide (Cr7C3), with a hardness of 1800-3200 HV; the thickness of the mixed intermediate layer is 20-30 μm, and the ceramic phase accounts for 30-50%; the thickness of the Cr / Ni rich alloy diffusion inner layer is 30-60 μm, the Cr content is 25-30%, and the Ni content is 15-20%.

[0011] Further, in step S4, the electrolyte for micro-arc oxidation treatment is an alkaline aluminate system, comprising 8-12 g / L NaAlO2, 2-5 g / L NaOH and 3-5 g / L Na2SiO3, pH=11-13, temperature 25-40℃; a DC pulse power supply is used, with a forward voltage of 300-450V, a forward duty cycle of 30-50%, a frequency of 50-100Hz, and a treatment time of 15-30 min.

[0012] Furthermore, in step S4, for Cl - The sensitive indicator is a complex of sodium fluorescein and silver nitrate (FL-Ag). + The concentration of the reagent is 0.5-1 g / L; the pH-sensitive indicator is bromocresol purple (BCP), with a concentration of 0.1-0.3 g / L; the vacuum degree of vacuum impregnation is ≤1×10⁻⁶. -3 Pa, impregnation time 30min, and then drying at 80℃ for 1 hour.

[0013] Furthermore, in step S3, the reaction chamber is equipped with a rotating fixture, and the rotation speed of the spokes is 5-10 rpm; in step S1, the tensile strength of the pretreated substrate is ≥800MPa, the elongation is ≥20%, and the surface roughness Ra is ≤0.8μm.

[0014] Compared with the prior art, the present invention can achieve the following technical effects: A fine-grained structure is achieved through intense plastic deformation, significantly improving the strength, toughness, and resistance to grain boundary corrosion of the spokes. Laser treatment forms a highly active surface layer, enhancing the adhesion and uniformity of subsequent deposition layers. Vapor infiltration deposition forms a multi-layered composite infiltration layer, achieving a smooth transition from hard ceramic to a tough matrix, avoiding interfacial stress concentration, and improving corrosion and wear resistance. Indicators in the micro-arc oxidation film can respond to the corrosive environment in real time, providing visual warnings and extending the spokes' service life. The entire process is continuous and controllable, suitable for large-scale production, and cost-effective.

[0015] Of course, any product implementing this invention does not necessarily need to achieve all of the technical effects described above at the same time. Attached Figure Description

[0016] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings: Figure 1 This is a flowchart of the corrosion-resistant spoke forming process according to an embodiment of the present invention. Detailed Implementation

[0017] The following will describe in detail the implementation of the present invention with reference to the accompanying drawings and embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0018] Please refer to Figure 1 , Figure 1 This is a flowchart of the corrosion-resistant spoke forming process according to an embodiment of the present invention.

[0019] Example 1: Surface modification and functional integration of 304L stainless steel spokes (5mm in diameter): S1. Substrate Pretreatment The substrate and initial condition were selected from 304L austenitic stainless steel wire (purchased from a steel group, specification φ5mm×1000mm), with the following chemical composition (mass fraction): Cr 19.2%, Ni 10.5%, C 0.02%, Si 0.4%, Mn 1.2%, and the remainder Fe. The initial microstructure consisted of equiaxed austenitic grains with an average grain size of 85μm (detected by EBSD, equipment model: ZEISS Gemini SEM 500, detection area 100μm×100μm), tensile strength of 580MPa, and elongation of 35% (tested by INSTRON 5969 universal testing machine, tensile rate 2mm / min).

[0020] Equipment selected for equal channel angle extrusion (ECAP) process: self-made ECAP die (material H13 hot work die steel, quenched and tempered, hardness 50-52HRC), die inner angle α=90°, outer angle β=30°, channel diameter 5mm (matching wire); extrusion equipment is a four-column hydraulic press (model Y32-100, rated pressure 1000kN).

[0021] Operating steps: (1) Wire pretreatment: Remove the surface oxide scale by sanding with sandpaper, ultrasonically clean with anhydrous ethanol for 15 min (power 300W, frequency 40kHz), dry and then coat with MoS2 grease (thickness about 5μm). (2) Extrusion parameters: extrusion temperature 300℃ (controlled by heating belt wrapped around the outside of the die, temperature control accuracy ±2℃), extrusion rate 8mm / s (hydraulic press piston movement speed), the wire rotates 90° (along the axial direction) after each extrusion, and a total of 6 extrusions are performed; (3) Intermediate inspection: Samples were taken after the 4th pass and observed by TEM (model JEOL JEM-2100). The grain size was refined to 2-3 μm; after the 6th pass, the grain size was 1.2 μm (average size of 50 grains). The grain boundary density decreased from the initial 1.2 × 10⁻⁶. 8 m -1 Increased to 1.5×10 9 m -1 (Calculated using EBSD grain boundary distribution map).

[0022] The equipment used in the low-temperature rolling process is a two-roll mill (model XK-160, roll diameter 160mm) equipped with a low-temperature constant temperature chamber (temperature control range -50℃~200℃, accuracy ±1℃).

[0023] Operating steps: (1) Place the ECAP-treated wire into a constant temperature chamber, heat it to 120℃ and keep it at that temperature for 30 minutes; (2) Rolled in 4 passes, with single pass reduction rates of 15%, 10%, 8% and 7% respectively, and cumulative reduction rate of 40%; during the rolling process, the wire temperature is monitored in real time by an infrared thermometer (model FLIR E60) and kept at 110-130℃; (3) Final dimensions: Diameter 3.8 mm (meets the finished spoke size requirements). The cross-section was observed by SEM. The grains were arranged in a fibrous pattern along the axial direction, and the dislocation density was 1.1 × 10⁻⁶. 14 m -2 (Calculated by XRD peak broadening method, using Cu Kα rays, scanning speed 2° / min).

[0024] The final mechanical properties of the substrate were measured as follows: tensile strength 860 MPa, elongation 23% (tensile test, gauge length 50 mm); surface condition: polished to Ra=0.5 μm with metallographic sandpaper (1200#) (measured with a TIME 3200 surface roughness tester, sampling length 0.8 mm), and ultrasonically cleaned with anhydrous ethanol for later use (to proceed to the next process within 1 hour to avoid secondary oxidation).

[0025] S2. Laser cleaning and activation Laser: Model IPG YLR-1000-MOPA, wavelength 1064nm, maximum output power 1000W, pulse width adjustable from 10-100ns, repetition frequency adjustable from 10-100kHz; Scanning system: Galvanometer model SCANLAB hurrySCAN 20, focal length 160mm, spot diameter can be adjusted by beam expander (adjusted to 80μm in this embodiment); Calibration steps: Power on and warm up for 30 minutes. Then, calibrate the output power using a power meter (model Ophir Vega) to ensure that the energy density error is ≤5%.

[0026] The selective cleaning process aims to remove residual grease (MoS2) and oxide film (approximately 30 nm thick) from the surface after rolling. Its parameter settings are as follows: Pulse width: 50ns (balancing cleaning efficiency with avoiding substrate damage); Repetition rate: 50kHz; Energy density: 1.0J / cm³ 2 (Calculated using the formula E=P / (f×v×d), where P=100W, f=50kHz, v=800mm / s=800000μm / s, d=80μm); Scanning path: spiral scan (pitch 50μm), 1 scan. Effect detection: (1) Cleanliness: The water contact angle was reduced from 85° before cleaning to 15° by a contact angle measuring instrument (model KRÜSS DSA100) (indicating that the surface oil has been removed). (2) Matrix integrity: SEM observation showed no craters or cracks on the surface, and EDS analysis showed that the oxygen content decreased from 3.2% to 0.5% (the oxide film has been removed).

[0027] The goal of the surface nano-activation process is to form an amorphous / nanocrystalline hybrid layer on the surface to enhance chemical activity. The parameter settings are as follows: Pulse width: 30ns (shortening the pulse width to improve the cooling rate); Repetition frequency: 30kHz; Energy density: 3.5 J / cm³ 2 (P=200W, f=30kHz, v=200mm / s, d=80μm); Scanning path: Orthogonal bidirectional scanning (XY axis cross scanning), spot overlap rate 60% (center distance between adjacent spots 32μm), number of scans 2; Effect detection: (1) Cross-sectional morphology: Cross-sectional samples were prepared using FIB (Focused Ion Beam, model FEI Helios G4), and TEM observation showed: The surface layer of 1-2 μm is completely amorphous (electron diffraction shows diffuse rings); The subsurface layer (2-12 μm) consists of nanocrystals (grain size 50-150 nm, polycrystalline rings observed by selected area electron diffraction). (2) Activity test: The self-corrosion current density of the activated layer in 3.5% NaCl solution was 1.2 × 10⁻⁶ using an electrochemical workstation (CHI660E). -8 A / cm 2 It is the original substrate (8.5×10 -7 A / cm 2 The surface activity was 1 / 70 of that of the target surface, indicating a significant improvement.

[0028] S3. In-situ reactive vapor infiltration deposition Reaction chamber: Horizontal stainless steel reactor (model GSL-1700X, volume 80L, heating zone length 500mm), equipped with: Vacuum system: mechanical pump + molecular pump (ultimate vacuum 5×10⁻⁶). -5 Pa, vacuum gauge model Pfeiffer PKR 251); gas control system: mass flow controller (MFC, model SevenStar D07-19B, accuracy ±1% FS), TiCl4 vaporization bottle (with heating jacket, temperature control accuracy ±1℃), CrCl3 aerosol generator (model TOPAS SMAG-4); rotary fixture: motor driven, speed 8rpm (to ensure uniform heating of spokes); The sample loading steps are as follows: (1) The laser-activated spokes (500mm in length) are vertically suspended on the rotating fixture with a spacing of 50mm to avoid mutual obstruction; (2) Close the reaction chamber, first use a mechanical pump to evacuate to 1 Pa, then turn on the molecular pump to evacuate to 5 × 10⁻⁶ Pa. -5 Pa, keep for 30 minutes (to remove residual air).

[0029] Preparation and introduction of mixed reactive gases: Gas composition and parameters are as follows: TiCl4: purity 99.9% (Aladdin reagent), vaporization bottle heated to 90℃ (saturated vapor pressure approximately 13 kPa), MFC controlled flow rate 48 sccm; CrCl3 aerosol: CrCl3 powder (99.9% purity, 5μm particle size) forms an aerosol through an Ar gas carrier, with a concentration of 8g / m³. 3 Flow rate 20 sccm; N2: purity 99.999%, flow rate 280 sccm; C2H2: purity 99.9%, flow rate 96 sccm; SiH4: purity 99.99%, flow rate 64 sccm; Ar (carrier gas): purity 99.999%, flow rate 292 sccm; Volume ratio: TiCl4:CrCl3:N2:C2H2:SiH4:Ar=6:2.5:35:12:8:36.5, total flow rate 800 sccm; Ventilation procedure: (1) First, purge with Ar gas (flow rate 500 sccm) for 10 minutes to remove residual air from the pipeline; (2) Turn on each gas MFC in sequence, introduce the mixed gas at the above flow rate, and start heating after stabilizing for 30 minutes.

[0030] Then, the heating and reaction process is carried out: Heating program: Room temperature → 500℃, heating rate 8℃ / min, set by a programmable temperature controller; Keep warm at 500℃ for 3 hours (reaction stage); After the heat preservation is completed, turn off the heating, continue to circulate Ar gas to cool down to below 100°C, and then turn off all gas. Reaction process monitoring: Temperature is monitored in real time by thermocouple (inserted in the middle of the reaction chamber, 10 mm away from the spoke surface), and the exhaust gas composition (mainly Cl2, the concentration of which gradually decreases as the reaction proceeds) is monitored by mass spectrometer (model Pfeiffer OmniStar).

[0031] Gradient composite seepage layer performance testing: Cross-sectional structure: Observation using SEM (ZEISS Gemini SEM 500) showed that the total thickness of the infiltrated layer was 82 μm, and the layers were as follows: Outer layer (0-8μm): dense and non-porous, EDS analysis shows it contains 35% Ti, 12% Cr, 20% N, and 15% C, corresponding to the TiN / TiC / Cr7C3 ceramic phase; Intermediate layer (8-33 μm): a mixture of ceramic phase (40%) and intermetallic compounds (FeTi, FeCr), with elements distributed in a gradient; Inner layer (33-82μm): Cr content 28.5%, Ni content 18.2% (more than 80% higher than the matrix), with no obvious interface with the matrix; Test mechanical properties: Microhardness: Tested by a microhardness tester (HVS-1000), the outer layer is 2250HV, the middle layer is 1100HV, and the inner layer is 450HV (load 100g, holding pressure 10s). The adhesion was tested using a scratch tester at a loading rate of 10 N / min and a critical load of 85 N (the load at which the coating is first peeled off).

[0032] S4. Integration of micro-arc oxidation and self-early warning function Micro-arc oxidation process Electrolyte preparation: The solvent is deionized water (conductivity ≤10μS / cm); Solutes: NaAlO2 (analytical grade) 10 g / L, NaOH (analytical grade) 3 g / L, Na2SiO3 (analytical grade) 4 g / L; Preparation steps: Dissolve each solute sequentially, stir magnetically for 30 minutes, adjust the pH to 12.0 with NaOH or HCl, and degas by sonication for 10 minutes (to remove air bubbles). Equipment and parameters: Power supply: Pulse DC power supply (model MAO-3000, output voltage 0-1000V, current 0-50A). Electrolytic cell: made of polytetrafluoroethylene (5L capacity), with built-in cooling coil (circulating water to control temperature at 30±2℃); Electrical parameters: forward voltage 400V, forward duty cycle 40%, reverse voltage 50V, reverse duty cycle 10%, frequency 80Hz, processing time 20min; Electrode connection: The spokes are the anodes, and the stainless steel plate on the inner wall of the electrolytic cell is the cathode, with an electrode spacing of 100 mm; Membrane properties: Thickness: 20μm (measured by TIME 2500 eddy current thickness gauge, averaged from multiple points); Morphology: SEM observation showed that the surface was porous, with pore size of 1-3 μm and porosity of 20% (Statistical analysis using Image-Pro Plus software). Composition: EDS analysis shows that it contains 35% Al, 8% Ti, and 55% O, making it an Al2O3-TiO2 composite ceramic.

[0033] Preparation of indicator solution: Solvent: Ethanol-deionized water mixture (volume ratio 1:1); Solutes: Sodium fluorescein (FL, analytical grade) 0.8 g / L, silver nitrate (analytical grade) 0.5 g / L (forming FL-Ag⁺ complex), bromocresol purple (BCP, analytical grade) 0.2 g / L; Stir for 30 minutes until completely dissolved, then filter to remove impurities; Next, a vacuum impregnation process was carried out using a vacuum drying oven (model DZF-6050, ultimate vacuum 1Pa), and the steps are as follows: (1) The spokes after micro-arc oxidation were ultrasonically cleaned with deionized water for 10 min and dried at 60℃ for 2 hours; (2) Place it in a beaker containing the indicator solution, put it in a vacuum drying oven, and evacuate it to 5×10⁻⁶. -4 Pa, maintain for 30 min (bubbling of the solution is observed on the spoke surface, indicating that the air in the pores has been expelled); (3) Break the vacuum, remove the spokes, wipe the excess solution on the surface with anhydrous ethanol, and dry at 80°C for 1 hour (to solidify the indicator in the pores).

[0034] The self-warning effect was tested through a corrosion simulation experiment: the spokes were immersed in a 3.5% NaCl solution (temperature 25℃, pH=6.5), and a 10mm long and 50μm deep scratch was made on the surface with a blade (exposing the middle layer). Observation results: After 18 hours, the solution at the scratch site began to turn pale yellow (BCP color change, visible to the naked eye); after 20 hours, when irradiated with a 365nm ultraviolet lamp, the scratch site emitted obvious green fluorescence (FL release, fluorescence intensity was measured by a fluorescence spectrophotometer LS55, peak wavelength 520nm); the unscratched area showed no color change or fluorescence, indicating that the warning is localized and targeted.

[0035] Corrosion resistance was tested using a neutral salt spray test according to ASTM B117 standard (5% NaCl solution, temperature 35℃, pH 6.5-7.2): Scratch-free sample: After 2200 hours, there was no red rust on the surface, only slight whitening of the micro-arc oxide film; Scratched samples: After 550 hours, only corrosion spots with a diameter of ≤1mm appeared at the scratched area, and they did not expand (the corrosion of traditional chrome-plated samples expanded to more than 5mm after 100 hours). Wear resistance: Tested by a pin-disc wear tester (HT-1000), with Al2O3 balls (φ5mm) as the wear pair, a load of 5N, a rotation speed of 300rpm, and after 1 hour of wear, the wear amount of the sample of this invention was 0.8mg, while the wear amount of the traditional PVD-TiN coating sample was 3.2mg (wear resistance improved by 4 times).

[0036] Example 2: 316L stainless steel large-diameter spokes (8mm in diameter) S1. Substrate Pretreatment: 316L stainless steel wire (Cr 17.5%, Ni 12.0%, Mo 2.5%) was selected to match the nanocrystalline structure and high strength. The initial grain size was 90μm. To meet heavy-load requirements, nanoscale refinement was achieved through deep plastic deformation. Equal channel angle extrusion (ECAP) was performed using an 8mm channel die at an extrusion temperature of 350℃ (balancing deformation resistance and grain stability), a speed of 10mm / s, and 8 passes (each pass rotating 90°). TEM analysis showed that the grain size was refined to 100-300nm (nanocrystalline content ≥70%), and the grain boundary density reached 2.0×10⁻⁶. 9 m -1 ; The low-temperature rolling process is carried out in 5 passes, with a cumulative reduction of 35% (7-8% reduction per pass to avoid uneven deformation of large-diameter wire). The rolling temperature is 150℃, and the final diameter is 5.2mm. Mechanical property tests show that the tensile strength reaches 920MPa and the elongation is 20% (meeting the strength and toughness requirements under heavy loads). The surface is polished with 1500# sandpaper to Ra=0.4μm, and then undergoes laser treatment within 1 hour after cleaning.

[0037] S2. Laser Processing: Uniform Activation of Large-Diameter Surfaces. Large-diameter spokes have small curvature but large area, requiring optimization of laser parameters to ensure radial uniformity. The cleaning stage uses 1.0 J / cm 2 Energy density, scanning speed of 800 mm / s, spot diameter of 100 μm (to expand coverage), spiral scanning path (pitch of 60 μm) to ensure no cleaning blind spots on an 8 mm diameter surface, water contact angle of 16° after cleaning, and oxygen content of 0.4%; The activation phase increases the energy density to 4.0 J / cm³. 2 (Larger diameters require higher energy to ensure surface melting). The scanning speed was 180 mm / s, the spot overlap was 65%, and the scan was performed three times, forming an 18 μm thick activation layer (2 μm amorphous surface layer + 16 μm nanocrystalline sub-surface layer, grain size 50-200 nm). Electrochemical testing showed that the self-corrosion current density of the activation layer was 9 × 10⁻⁶. -9 A / cm2 Its surface activity is superior to that of narrow spokes, providing ample reaction sites for subsequent vapor deposition.

[0038] S3. Vapor-phase infiltration deposition: Heavy-load adaptation of thick gradient infiltration layers requires increasing the thickness of the infiltration layer and improving the surface hardness to resist heavy-load friction. The mixed reaction gas was adjusted to: TiCl4 7%, CrCl3 aerosol (9 g / m³). 3 3%, N2 32%, C2H2 14%, SiH4 10%, Ar 34% (increasing the SiH4 proportion to improve the ceramic phase density), total flow rate 900 sccm; The reaction temperature was increased to 600℃ (316L containing Mo, offering better high-temperature resistance), and held at that temperature for 2.5 hours to promote deep atomic diffusion. This resulted in a 95μm thick gradient composite diffusion layer: an outer 10μm layer (primarily TiC / Cr7C3, hardness 2300HV), a middle 30μm layer (45% ceramic phase, relieving surface stress), and an inner 55μm layer (30.2% Cr, 19.5% Ni, metallurgically bonded to the matrix). Scratch tests showed a critical bonding force of 90N (suitable for heavy-duty impact loads).

[0039] S4. Micro-arc oxidation and early warning integration: Dual enhancement of wear resistance and early warning. The micro-arc oxidation electrolyte uses a high-concentration formula (NaAlO2 12g / L, NaOH 4g / L, Na2SiO3 5g / L), with a treatment time of 25min, to generate a 25μm thick Al2O3-TiO2-MoO3 composite film (containing Mo elements diffused from the substrate), with a hardness of 1100HV and a porosity of 18% (pore size 2-4μm, balancing wear resistance and indicator storage). The indicator filling uses a high-concentration solution (FL-Ag) + 1.0 g / L, BCP 0.25 g / L), vacuum degree 5 × 10 -4 Immerse for 35 minutes under Pa to ensure that the large-diameter surface pores are fully filled. After drying at 80°C, wipe off any excess indicator on the surface with ethanol.

[0040] Performance verification: Corrosion resistance: No red rust after 2500 hours of neutral salt spray test (ASTM B117), and no corrosion propagation after 600 hours of scratching (10% improvement over 304L spokes); Wear resistance: The pin wear test (load 10N) showed that the wear amount was 0.6mg (1 / 5 of that of traditional chrome plating), which is suitable for high-frequency friction under heavy load; Early warning response: Color change and fluorescence appear 15 hours after scratching in 3.5% NaCl solution. The response speed is better than that of small-diameter spokes, which meets the early warning requirements of heavy equipment.

[0041] In summary, this embodiment addresses the challenge of uniform processing of large-diameter spokes by optimizing plastic deformation parameters, increasing reaction temperature, and adjusting gas ratio. Its performance is suitable for the high load and high wear conditions of heavy machinery, further demonstrating the universality of this invention for spokes of different sizes and materials.

[0042] Example 3: Surface treatment of 304L stainless steel narrow spokes (3mm in diameter) S1. Substrate Pretreatment: 304L wire (initial grain size 75μm, tensile strength 570MPa) was used for low-stress ultrafine grain preparation. Considering the easy fracture characteristics of thin diameter wires, the plastic deformation parameters were adjusted as follows: Equal channel angle extrusion (ECAP) was performed using a 3mm channel die, with the extrusion temperature reduced to 280℃ (to decrease deformation resistance), a speed of 5mm / s, and only 4 passes (to reduce cumulative stress). EBSD testing showed that the grain size was refined to 2.5μm and the grain boundary density was 1.2×10⁻⁶. 9 m -1 ; Low-temperature rolling controls the single-pass reduction rate to ≤10%, with a cumulative reduction rate of 25%. Rolled to a diameter of 2.2 mm at 100℃, TEM analysis shows short fibrous grains and a dislocation density of 8 × 10⁻⁶. 13 m -2 The final tensile strength is 780 MPa and the elongation is 25% (retaining sufficient toughness). After pretreatment, the surface is polished to Ra=0.6 μm, and after cleaning, it enters the next process within 30 minutes to avoid secondary oxidation.

[0043] S2. Laser Processing: For low-damage activation of narrow-diameter spokes with small surface areas, the laser energy needs precise control to prevent overheating. During the cleaning stage, use 0.8 J / cm 2 Energy density, 1000 mm / s scanning speed (shortening single-area irradiation time), 50 μm spot coverage of the edge, water contact angle of 18° after cleaning, oxygen element residue of 0.6%, no ablation traces; The activation phase is at 3.0 J / cm 2 Three scans were performed at 250 mm / s (to improve uniformity), with a 50% overlap of the light spots, ultimately forming an 8 μm thick activation layer (1 μm amorphous + 7 μm nanocrystalline). Electrochemical testing showed a self-corrosion current density of 1.5 × 10⁻⁶. -8 A / cm 2 This meets the requirements for gas-phase reaction activity.

[0044] S3. Vapor Permeation Deposition: Thin gradient permeation layer design to avoid excessively thick permeation layers affecting assembly, controlling diffusion depth: The TiCl4 content in the mixed gas was reduced to 5%, and the CrCl3 aerosol concentration was 6 g / m³. 3 Total flow rate: 500 sccm; The material was held at 480℃ for 2 hours (to shorten the diffusion time), resulting in a 55μm thick gradient layer: an outer 5μm layer (TiN / Cr7C3 ceramic, hardness 2100HV), a middle 15μm layer (a ceramic-metal intermetallic compound mixed phase), and an inner 35μm layer (Cr 26%, Ni 17%). The critical load for the scratch test was 75N, meeting the bonding strength requirements for small-diameter spokes.

[0045] S4. Micro-arc oxidation and early warning integration: Lightweight functional design Micro-arc oxidation uses a low-concentration electrolyte (NaAlO2 8g / L, NaOH 2g / L) to generate a 12μm thick porous membrane (pore size 1-2μm) in 15 minutes, reducing weight gain; Low concentration indicator (FL-Ag) + Vacuum impregnation for 20 minutes with 0.5 g / L BCP (0.1 g / L) to avoid pore blockage.

[0046] Performance verification: No red rust after 1800 hours of salt spray test; corrosion controllable after 450 hours of scratching; no breakage after bending 90° (traditional coatings peel off at 60°); single piece weight gain ≤0.5g, fully suitable for light equipment requirements.

[0047] This embodiment 3 addresses the scenario of "lightweight equipment with small diameters," achieving performance adaptation through targeted parameter adjustments. The process logic is coherent and the details are complete, demonstrating the versatility and optimizability of the present invention.

[0048] The foregoing description illustrates and describes several preferred embodiments of the present invention. However, as previously stated, it should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the inventive concept described herein through the foregoing teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A corrosion-resistant spoke forming process, characterized in that, Includes the following steps: S1. Substrate pretreatment: Austenitic stainless steel wire is selected and ultrafine grain or nanocrystalline structure is obtained through a severe plastic deformation process. The grain size of the ultrafine grain or nanocrystalline structure is 100nm-5μm, and the grain boundary density is increased by 10-15 times compared with the original substrate. S2. Laser Cleaning and Activation: The spokes pretreated in step S1 are scanned using a pulsed fiber laser, initially at a speed of 0.5-1.5 J / cm². 2 Surface contaminants are removed using an energy density and a scanning speed of 500-1000 mm / s, followed by a process of 2-5 J / cm². 2 The energy density and scanning speed of 100-300 mm / s enable the formation of an amorphous / nanocrystalline hybrid activation layer in a 5-20 μm region on the surface of the spokes, wherein the dislocation density of the activation layer is ≥10. 14 m -2 Vacancy concentration ≥10 20 cm -3 ; S3. In-situ reactive vapor infiltration deposition: The spokes activated in step S2 are placed in a sealed reaction chamber and evacuated to ≤1×10⁻⁶. -4 After Pa, a mixed reactive gas is introduced, and the mixture is heated at 450-650℃ for 2-4 hours to allow the reactive gas to undergo a chemical reaction on the spoke surface and diffuse towards the surface layer, forming a gradient composite diffusion layer. The mixed reactive gas includes a metal-organic compound gaseous precursor, a non-metallic reactive gas, and a carrier gas. The gradient composite diffusion layer consists of a dense ceramic phase outer layer, a mixed intermediate layer of ceramic and intermetallic compounds, and a Cr / Ni rich alloy diffusion inner layer from the outside to the inside, with a total thickness of 50-100 μm. S4. Integration of Micro-arc Oxidation and Self-Early Warning Function: The spokes with gradient composite infiltration layers obtained in step S3 are subjected to micro-arc oxidation treatment to generate a porous ceramic membrane with a thickness of 10-30 μm on the surface of the infiltration layer. Then, the micropores of the porous ceramic membrane are filled with chlorine using vacuum impregnation technology. - Or a pH-sensitive indicator to form a corrosion self-warning functional layer.

2. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S1, the austenitic stainless steel wire is 304L or 316L, wherein 304L has a Cr content of 18-20% and a Ni content of 8-12%, and 316L has a Cr content of 16-18%, a Ni content of 10-14%, and a Mo content of 2-3%; the intense plastic deformation process is equal channel angle extrusion combined with low-temperature rolling, wherein the inner angle of the die for equal channel angle extrusion is 90° and the outer angle is 30°, the extrusion temperature is 250-350℃, the extrusion rate is 5-10mm / s, and the number of extrusion passes is 4-8; the cumulative reduction rate for low-temperature rolling is 30-50%, and the rolling temperature is 100-150℃.

3. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S2, the pulsed fiber laser has a wavelength of 1064 nm, a pulse width of 10-100 ns, a repetition frequency of 10-100 kHz, and a maximum single pulse energy of 50 mJ; the laser scanning spot diameter is 50-100 μm, the spot overlap rate in the surface nano-sizing stage is 50-70%, and the number of scans is 2-3.

4. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S3, the organometallic gaseous precursor comprises titanium tetrachloride (TiCl4) and chromium trichloride (CrCl3), wherein TiCl4 is heated to 80-100°C to vaporize, and CrCl3 is introduced in the form of an aerosol at a concentration of 5-10 g / m³. 3 The non-metallic reactive gases include nitrogen (N2), acetylene (C2H2), and silane (SiH4), all with a purity ≥99.9%; the carrier gas is argon (Ar) with a purity ≥99.999%.

5. The corrosion-resistant spoke forming process according to claim 4, characterized in that, The volume ratio of the mixed reaction gases is: TiCl4:CrCl3 aerosol:N2:C2H2:SiH4:Ar = (5-8):(2-3):(30-40):(10-15):(5-10):(30-40), and the total flow rate is 500-1000 sccm.

6. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S3, the thickness of the dense ceramic phase outer layer is 5-10 μm, and its main components are titanium nitride (TiN), titanium carbide (TiC), and chromium carbide (Cr7C3), with a hardness of 1800-3200 HV; the thickness of the mixed intermediate layer is 20-30 μm, and the ceramic phase accounts for 30-50%; the thickness of the Cr / Ni rich alloy diffusion inner layer is 30-60 μm, the Cr content is 25-30%, and the Ni content is 15-20%.

7. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S4, the electrolyte for the micro-arc oxidation treatment is an alkaline aluminate system, comprising 8-12 g / L NaAlO2, 2-5 g / L NaOH, and 3-5 g / L Na2SiO3, with a pH of 11-13 and a temperature of 25-40°C. A DC pulse power supply is used, with a forward voltage of 300-450V, a forward duty cycle of 30-50%, a frequency of 50-100Hz, and a treatment time of 15-30 min.

8. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S4, the action on Cl - The sensitive indicator is a complex of sodium fluorescein and silver nitrate (FL-Ag). + The concentration of the reagent is 0.5-1 g / L; the pH-sensitive indicator is bromocresol purple (BCP) with a concentration of 0.1-0.3 g / L; the vacuum degree of the vacuum impregnation is ≤1×10⁻⁶. -3 Pa, impregnation time 30min, and then drying at 80℃ for 1 hour.

9. The corrosion-resistant spoke forming process according to claim 1, characterized in that, In step S3, the reaction chamber is equipped with a rotating fixture, and the rotation speed of the spokes is 5-10 rpm; in step S1, the tensile strength of the pretreated substrate is ≥800MPa, the elongation is ≥20%, and the surface roughness Ra is ≤0.8μm.

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