A polishing method and device for nickel-based alloy based on photocatalysis-photo thickening cooperation

Abstract

This invention discloses a polishing method and apparatus for nickel-based alloys based on photocatalysis and photothickening synergy. It achieves dual-driven processing by simultaneously triggering photocatalytic workpiece surface modification and photo-triggered thickening of the polishing slurry through an integrated dual-light system, realizing surface softening and medium thickening. Composite abrasive particles loaded with TiO2 / ZnO photocatalysts form a low-hardness oxide layer on the nickel-based alloy surface under ultraviolet light irradiation, reducing processing resistance. Precise viscosity control of the polishing slurry is achieved through azobenzene / cinnamic acid photochromic molecules, combined with shear-induced particle agglomeration to form a dual thickening system, improving viscosity stability. This invention solves the technical pain points of work hardening in nickel-based alloys, large viscosity fluctuations in traditional shear-thickening polishing slurries, and poor processing uniformity, improving processing efficiency and workpiece surface quality. It is suitable for efficient and precise machining of difficult-to-machine nickel-based alloys such as Inconel 718 and GH4169.

Description

Technical Field

[0001] This invention belongs to the field of precision machining technology of metal materials, specifically relating to a polishing method and apparatus for nickel-based alloys based on photocatalysis-photothickening synergy. Background Technology

[0002] Nickel-based alloys (such as Inconel 718 and GH4169) are widely used in critical fields such as core components of aero-engines and structural parts of nuclear reactors due to their excellent high-temperature strength, corrosion resistance, and fatigue resistance. However, the high hardness (HRC 38-45) and toughness of nickel-based alloys make them prone to work hardening during traditional machining processes. This leads to high material removal resistance, severe tool wear, and problems such as grain boundary damage and excessive residual stress on the machined surface, which seriously affect the service life and reliability of the parts.

[0003] Shear-thickening polishing (STP), as a novel precision machining technology, utilizes the viscosity abrupt change (shear-thickening effect) of the polishing slurry at high shear rates to achieve uniform coating of abrasive grains and controllable cutting, effectively improving the surface quality of the machined material. However, traditional shear-thickening polishing slurries have significant limitations: on the one hand, their viscosity mainly depends on shear force-induced particle agglomeration, which is easily affected by temperature and shear rate fluctuations, resulting in poor stability, uneven abrasive grain dispersion, and insufficient machining uniformity; on the other hand, for ultra-high hardness materials such as nickel-based alloys, relying solely on the shear-thickening effect is insufficient to effectively reduce material removal resistance, leading to low machining efficiency and failing to meet the demands of high-efficiency precision machining.

[0004] To address the aforementioned issues, two types of improvement solutions have emerged in existing technologies: one is photo-triggered thickening polishing slurry technology (such as CN112518561A), which regulates the viscosity of the polishing slurry through the isomerization reaction of photochromic molecules, thereby improving viscosity stability. However, this solution only affects the polishing slurry and does not improve the surface hardness of the workpiece, resulting in limited improvement in the processing efficiency of nickel-based alloys. The other is photocatalytic surface modification technology, which utilizes active free radicals generated by semiconductor photocatalysts under light irradiation to oxidize and soften the workpiece surface, reducing processing resistance. However, this solution does not optimize the performance of the polishing slurry, leading to problems such as uneven abrasive particle dispersion and surface quality fluctuations. Furthermore, traditional single photocatalytic modification and single photo-triggered thickening are both simple irradiation schemes with a single light source, fixed mode, and no linkage control. Without auxiliary light sources or real-time feedback dynamic adjustment, they cannot form a uniform low-hardness oxide layer, the viscosity of the polishing slurry is unstable, and the reaction process cannot be precisely controlled, affecting processing efficiency and accuracy.

[0005] Currently, there is no existing dual-light synergistic processing scheme that combines "photocatalytic workpiece surface modification" with "photo-triggered polishing slurry thickening." This fails to simultaneously address the three core pain points of nickel-based alloy work hardening, unstable polishing slurry viscosity, and poor processing uniformity, thus hindering the development of precision machining technology for nickel-based alloys. Furthermore, existing photo-triggered / shear thickeners are all single-function materials, lacking a composite system that simultaneously satisfies "photocatalysis, photo-triggered thickening, and shear thickening." Conventional shear-thickening polishing slurries only fulfill the basic functions of shear-induced thickening and abrasive cutting, with components mainly consisting of a base liquid, abrasive particles, and conventional thickeners. Nickel-based alloy surface modification liquids (such as photocatalytic modification liquids) only achieve workpiece surface oxidation softening, with components mainly consisting of photocatalysts and solvents. Both types of liquids are single-function directed, and there is no compatibility design between components. Direct mixing can lead to problems such as abrasive particle agglomeration, photocatalyst deactivation, and thickening effect failure. Therefore, developing a processing method that combines the synergistic effects of surface softening and medium thickening has become a pressing technical challenge in this field. Summary of the Invention

[0006] This invention addresses the core shortcomings of existing nickel-based alloy precision machining technologies, such as the fragmented and single-functional designs of photocatalytic surface modification, polishing slurry performance regulation, and equipment integration and synergy. It provides a nickel-based alloy polishing method and device based on photocatalysis-photothickening synergy, which overcomes the technical bottleneck of traditional technologies that cannot simultaneously achieve efficient workpiece surface softening and precise control of polishing slurry viscosity. Relying on the multifunctional formula and preparation process innovation of dual-response polishing slurry, and the integrated design and dynamic synergistic regulation innovation of dual-light irradiation system, it fundamentally solves the four core technical challenges in the shear-thickening polishing process of nickel-based alloys.

[0007] In a first aspect, the present invention provides a polishing method for nickel-based alloys based on a photocatalytic-photothickening synergy, comprising: spraying a polishing slurry onto a nickel-based alloy workpiece or immersing the workpiece in the polishing slurry; and polishing the surface of the workpiece. The polishing slurry is a dual-response polishing slurry, comprising a base liquid, composite abrasive particles, and a photochromic thickener. The composite abrasive particles comprise an abrasive matrix and a photocatalyst supported on the surface of the abrasive matrix. The photocatalyst is a catalyst that catalyzes the oxidation of the nickel-based alloy surface under ultraviolet light.

[0008] During the polishing process, ultraviolet light is used to irradiate the polishing slurry on the workpiece surface. The ultraviolet light simultaneously triggers photocatalytic oxidation on the workpiece surface and increases the viscosity of the dual-response polishing slurry with a photochromic thickener. At the same time, visible light pulses are used to irradiate the polishing slurry on the workpiece surface. The viscosity of the dual-response polishing slurry is detected. When the measured viscosity is not within the target viscosity range, the viscosity of the dual-response polishing slurry is controlled to remain within the preset target viscosity range by adjusting one or more of the visible light intensity and irradiation duty cycle.

[0009] As a preferred method, the surface hardness of the workpiece is detected during the polishing process; the reaction rate of photocatalytic oxidation is controlled by adjusting the intensity of ultraviolet light so that the surface hardness of the workpiece is less than or equal to the target hardness threshold.

[0010] Preferably, when the viscosity is greater than the target viscosity range, the intensity of visible light and / or the duty cycle of illumination are increased; when the viscosity is less than the target viscosity range, the intensity of visible light and / or the duty cycle of illumination are decreased.

[0011] Preferably, the target hardness threshold is 200 HV.

[0012] Preferably, after the polishing operation is completed, the workpiece surface is irradiated with infrared light to reduce the viscosity of the dual-response polishing fluid on the workpiece surface through the thermal effect; the workpiece is then rinsed to remove any residual polishing fluid.

[0013] Preferably, before polishing begins, the workpiece sprayed with or immersed in the dual-response polishing slurry is pre-irradiated with ultraviolet light to achieve combined activation of photocatalysis and photothickening. The activation target for photocatalysis is that the concentration of hydroxyl radicals in the dual-response polishing slurry is greater than or equal to a concentration threshold; the activation target for photothickening is that the viscosity of the dual-response polishing slurry is within a target viscosity range; the target viscosity range is 200 mPa·s to 300 mPa·s.

[0014] Preferably, the base liquid is polyethylene glycol with a number average molecular weight of 400-600. The abrasive matrix is ​​a mixture of SiO2 and Al2O3 abrasive particles. The photocatalyst is TiO2 and / or ZnO, loaded onto the surface of the abrasive matrix via a sol-gel method. The mass fraction of the photocatalyst in the composite abrasive particles is 5%-15%.

[0015] Preferably, the particle size of the composite abrasive is 50 nm to 200 nm.

[0016] Preferably, the photochromic thickener is an inclusion complex formed by an azobenzene derivative and cyclodextrin. The molar ratio of the azobenzene derivative to cyclodextrin is 1:(1-3).

[0017] Preferably, the azobenzene derivative is azobenzene-4-benzoic acid. The cyclodextrin is β-cyclodextrin.

[0018] Preferably, the dual-response polishing slurry further includes a pH adjuster and a dispersant to inhibit abrasive particle aggregation. The dispersant is sodium polyacrylate. The pH value of the dual-response polishing slurry is 8–10.

[0019] Preferably, in the dual-response polishing slurry, the volume fraction of the composite abrasive particles is 35 vol% to 45 vol; and the volume fraction of the photochromic thickener is 5 vol% to 10 vol.

[0020] Secondly, this invention provides a nickel-based alloy polishing apparatus based on photocatalysis-photothickening synergy, used to perform the aforementioned nickel-based alloy polishing method. The nickel-based alloy polishing apparatus includes a circulating liquid supply module, an industrial five-axis machine tool, a combined light source module, a detection module, a polishing head, and a workpiece fixture. The industrial five-axis machine tool has a polishing tank on its worktable. The workpiece fixture is installed in the polishing tank. The polishing head is mounted on the spindle of the industrial five-axis machine tool; the industrial five-axis machine tool is configured to polish the workpiece using the polishing head.

[0021] The circulating fluid supply module includes a polishing fluid output component and a polishing fluid return component. The polishing fluid output component includes a supply metering pump, a damper, a back pressure valve, a pressure gauge, a pressure regulating valve, and a fluid nozzle connected in sequence. The fluid nozzle is positioned above the polishing tank, facing the workpiece fixture. The polishing fluid return component includes a drain port, a recovery metering pump, a stirring tank, and a return pipe connected in sequence. The drain port is located at the bottom of the polishing tank. The return pipe is connected to the supply metering pump.

[0022] The combined light source module includes a main ultraviolet light source, an infrared light source, and an auxiliary visible light source facing the workpiece fixture. The detection module includes a viscosity sensor for detecting the viscosity of the polishing fluid and a surface hardness monitor for detecting the hardness of the polished surface of the workpiece.

[0023] Preferably, the main ultraviolet light source, infrared light source, and auxiliary visible light source are all equipped with optical lens assemblies at their light emission positions.

[0024] The present invention has the following beneficial effects.

[0025] 1. This invention constructs a dual-light synergistic processing mechanism of "photocatalytic surface modification + photo-triggered polishing fluid thickening" to simultaneously regulate the surface state of the workpiece and the rheological properties of the processing medium. This allows for the simultaneous oxidation softening of the nickel-based alloy surface and the stable increase of the polishing fluid viscosity during processing. This overcomes the problem of existing technologies that only improve the polishing fluid or only improve the workpiece surface on one side. It can simultaneously reduce material removal resistance and improve the stability of abrasive action, significantly improving the efficiency and surface quality of precision machining of nickel-based alloys.

[0026] 2. This invention achieves the effect of forming a low-hardness oxide layer on the workpiece surface by loading a photocatalyst on the surface of composite abrasive particles and triggering a photocatalytic oxidation reaction under ultraviolet light. This reduces the cutting resistance and work hardening degree during the processing of nickel-based alloys, reduces tool or abrasive wear and grain boundary damage, and helps to improve material removal efficiency and improve the residual stress state of the surface after processing.

[0027] 3. This invention sets up a photochromic thickening system formed by azobenzene derivatives and cyclodextrin, and uses light to regulate its molecular isomerization process, thereby achieving the effect of reversibly adjusting the viscosity of the polishing slurry. This enhances the ability of the polishing slurry to coat and hold abrasive particles, improves the uniformity of abrasive particle dispersion and the stability of the processing, and avoids the problem of viscosity instability caused by traditional shear-thickened polishing slurries being easily affected by shear rate and temperature fluctuations.

[0028] 4. This invention constructs a combined light source system comprising a main ultraviolet light source, an auxiliary visible light source, and an infrared light source, and combines a viscosity sensor and a surface hardness monitoring device for real-time detection and feedback control, thereby achieving dynamic adjustment of the viscosity of the polishing slurry and the surface oxidation reaction rate. This realizes the decoupled control of photocatalytic surface modification and photo-triggered thickening of the polishing slurry, enabling the processing to achieve a stable and controllable precision processing state.

[0029] 5. This invention designs a dual-response polishing fluid system that integrates photocatalysis, photo-triggered thickening, and shear thickening functions, and optimizes the synergistic ratio of the base fluid, composite abrasive particles, photochromic thickener, and dispersion system to achieve a multi-functional synergistic effect. This avoids problems such as abrasive particle agglomeration, photocatalyst deactivation, or thickening effect failure caused by direct mixing of traditional single-function processing fluids, thereby improving the stability and recyclability of the polishing fluid system. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the overall structure of Embodiment 1 of the present invention.

[0031] Figure 2 This is a process flow diagram of the nickel-based alloy polishing method provided in Embodiment 2 of the present invention.

[0032] Reference numerals: 1. Metering pump; 2. Damper; 3. Back pressure valve; 4. Pressure gauge; 5. Pressure regulating valve; 6. Industrial five-axis machine tool; 601. X-axis displacement assembly; 602. Y-axis displacement assembly; 603. Lifting adjustment assembly; 604. Rotary drive assembly; 605. Angle adjustment assembly; 7. Fluid nozzle; 8. Main ultraviolet light source; 9. Viscosity sensor; 10. Polishing head; 11. Infrared light source; 12. Auxiliary visible light source; 13. Workpiece to be processed; 14. Surface hardness monitor; 15. Workpiece fixture; 16. Drain port; 17. Stirring blade; 18. Recovery metering pump; 19. Controller; 20. Electrical control cabinet; 21. Return pipeline. Detailed Implementation

[0033] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0034] Example 1

[0035] like Figure 1 As shown, an apparatus for a nickel-based alloy processing method based on photocatalysis-photothickening synergy includes a circulating liquid supply module, an industrial five-axis machine tool 6, a combined light source module, a detection module, a polishing head 10, a workpiece fixture 15, a main controller 19, and an electrical control cabinet 20. The industrial five-axis machine tool 6 has a polishing tank on its worktable. The workpiece fixture is installed inside the polishing tank and is used to clamp the workpiece 13 to be processed. The polishing head 10 is mounted on the spindle of the industrial five-axis machine tool 6 and is used to polish the workpiece 13.

[0036] The circulating fluid supply module includes a polishing fluid output component and a polishing fluid return component. The polishing fluid output component, polishing tank, and polishing fluid return component are connected in sequence to form a circulation loop for conveying the polishing fluid. The polishing fluid is a dual-response polishing fluid with photocatalysis and photothickening.

[0037] The polishing fluid output assembly includes a supply metering pump 1, a damper 2, a back pressure valve 3, a pressure gauge 4, a pressure regulating valve 5, and a fluid nozzle 7 connected in sequence. The fluid nozzle 7 is positioned above the polishing tank and faces the workpiece clamp, and is used to continuously spray polishing fluid onto the clamped workpiece 13.

[0038] The polishing slurry reflux assembly includes a drain port 16, a recovery metering pump 18, a stirring tank, and a reflux pipe 21 connected in sequence. The drain port 16 is located at the bottom of the side wall of the polishing tank. The end of the reflux pipe 21 is connected to the inlet of the supply metering pump 18. The stirring tank is equipped with stirring blades 17 driven by a motor.

[0039] During operation, the supply metering pump (1) is started, and the polishing liquid is delivered from the mixing tank to the fluid nozzle (7) after being stabilized by the damper (2) and the back pressure valve (3), and sprayed into the processing area. The polishing liquid then flows to the collection area at the bottom of the workpiece and is recovered into the mixing tank by the recovery metering pump (18).

[0040] The industrial five-axis machine tool 6 includes an X-axis displacement assembly 601, a Y-axis displacement assembly 602, a lifting adjustment assembly 603, a rotary drive assembly 604, and an angle adjustment assembly 605. The Y-axis displacement assembly 602 is horizontally mounted on the base of the industrial five-axis machine tool 6. The X-axis displacement assembly 601 is mounted on the Y-axis displacement assembly 602. The rotary drive assembly 604 is mounted on the X-axis displacement assembly 601, with the axis of rotation vertically positioned. The lifting adjustment assembly 603 is vertically mounted on the base of the industrial five-axis machine tool 6. The angle adjustment assembly 605 is mounted on the lifting adjustment assembly 603. The spindle is mounted on the angle adjustment assembly 605. The worktable of the industrial five-axis machine tool 6 is mounted on the rotary drive assembly 604. The X-axis displacement assembly 601 and the Y-axis displacement assembly 602 are used to drive the workpiece 13 in the polishing tank to move horizontally with two degrees of freedom. The rotary drive assembly 604 drives the workpiece 13 in the polishing tank to rotate; the lifting adjustment assembly 603 and the angle adjustment assembly 605 are used to drive the spindle to lift and rotate around the Y-axis.

[0041] The combined light source module includes a main ultraviolet light source 8, an infrared light source 11, an auxiliary visible light source 12, and a power regulator. The main ultraviolet light source 8, infrared light source 11, and auxiliary visible light source 12 are all mounted on the base of the industrial five-axis machine tool 6, facing downwards towards the workpiece fixture 15 in the polishing tank. Optical lens assemblies are provided at the light emission positions of the main ultraviolet light source 8, infrared light source 11, and auxiliary visible light source 12. The optical lens assemblies are used to adjust the light coverage range and improve the uniformity of light intensity. The power regulator is used to adjust the output power of the main ultraviolet light source 8, infrared light source 11, and auxiliary visible light source 12, and can receive commands from the main controller 19.

[0042] The detection module includes a viscosity sensor 9 and a surface hardness monitor 14 that communicate with the main controller 19. In some embodiments, the viscosity sensor 9 is an immersion vibrating tuning fork viscosity sensor, with the probe extending into the polishing tank and directly contacting the polishing fluid, achieving real-time viscosity detection based on the liquid shear damping effect; the surface hardness monitor 14 is a non-contact laser ultrasonic hardness sensor, installed on the side of the polishing tank to monitor the workpiece surface, achieving non-destructive online surface hardness detection based on the laser ultrasonic response characteristics. Both the viscosity sensor 9 and the surface hardness monitor 14 are installed in the polishing tank and are used to detect the viscosity of the polishing fluid and the surface hardness of the clamped workpiece 13, respectively.

[0043] In some embodiments, instead of a surface hardness monitor 14, the degree of oxidation of the workpiece surface is predicted by detecting the concentration of hydroxyl radicals. The corresponding surface hardness of the workpiece is then predicted based on the degree of oxidation.

[0044] The device provided in this embodiment drives the dual-response polishing slurry to be sprayed onto the workpiece in a circulating manner, simultaneously carrying out photocatalytic reaction and photo-thickening polishing.

[0045] The combined light source module in the nickel-based alloy polishing device of this embodiment is the core equipment for realizing dual-light synergistic processing. It needs to meet the dual photoresponse requirements of photocatalyst and photochromic thickener, and at the same time have the characteristics of precise power adjustment, adjustable angle, and high integration. The specific design is as follows:

[0046] (1) Light source design

[0047] The main light source integrates a primary ultraviolet light source 8, an auxiliary visible light source 12, and an infrared light source 11. The uniformity of illumination from these three sources is ≥90%. Specific parameters are as follows:

[0048] Main UV light source 8: Employs 365 nm high-power LED chips, with 16 light-emitting units, an array radius of 8 cm, a unit spacing of 1.5 cm, and a power density adjustment range of 20-50 mW / cm². 2 Adjustment accuracy ±1 mW / cm 2 Continuous irradiation mode is used to simultaneously activate photocatalysts and photochromic thickeners.

[0049] Auxiliary visible light source 12: Employs 550 nm high-power LED chips, with 12 light-emitting units, an array radius of 8 cm, a unit spacing of 2 cm, and a power density adjustment range of 10-30 mW / cm². 2 Adjustment accuracy ±1 mW / cm 2 It supports switching between continuous irradiation and pulse irradiation modes, with a pulse frequency of 1-10 Hz, for precise viscosity compensation.

[0050] Infrared Light Source 11: Employs a 900 nm high-power LED chip, with 8 light-emitting units, an array radius of 8 cm, a unit spacing of 2.5 cm, and a power density adjustment range of 30-60 mW / cm². 2 Adjustment accuracy ±1 mW / cm 2 Continuous irradiation mode is used to reduce the viscosity of the polishing slurry in the final stage.

[0051] (2) Design of optical lens assembly

[0052] The optical lens assembly uses a quartz convex lens with a focal length of 15 cm and a light transmittance of ≥95% (300-1000 nm wavelength range). The lens surface is coated with an anti-reflective film (reflectivity ≤2%) to focus light, improve the uniformity of irradiation intensity, ensure uniform light intensity distribution in the workpiece processing area and the polishing fluid action area, and avoid uneven oxide layer thickness or viscosity fluctuations caused by excessively strong or weak local light.

[0053] (3) Power Regulator Design

[0054] The power regulator employs a PID feedback control algorithm. Its core components include a microcontroller, a power drive chip, a current sensor, and a voltage sensor, with the following specific functions:

[0055] Signal acquisition: Receives real-time data from viscosity sensor 9 and surface hardness monitor 14, with an acquisition frequency of 1 time / s.

[0056] Algorithm processing: The collected data is processed by the PID algorithm to calculate the required adjustment amount of the light source power. The PID parameters are: proportional coefficient Kp=2.5, integral coefficient Ki=0.5, and derivative coefficient Kd=0.1.

[0057] Power output: The power output is precisely adjusted by controlling the drive current of the LED chip through the power driver chip, with a response time of ≤500 ms.

[0058] (4) Design of lighting control module

[0059] The illumination control module uses a microcontroller (STM32F103) and a relay module (SSR-25DA), supporting switching between continuous illumination and pulsed illumination modes. Its specific functions are as follows:

[0060] Mode switching: Select the irradiation mode via buttons or host computer software. The pulse frequency adjustment range is 1-10 Hz, and the pulse duty cycle adjustment range is 10%-90%.

[0061] Time control: Supports timed illumination function, allowing you to set the on time, off time and illumination duration of each light source, with a time accuracy of ±1 second.

[0062] Synchronous control: Enables the synchronous activation and deactivation of the main ultraviolet light source 8, auxiliary visible light source 12, and infrared light source 11, ensuring the coordination of the processing.

[0063] Example 2

[0064] A nickel-based alloy polishing method based on photocatalysis-photothickening synergy is proposed. The polishing device provided in Example 1 is used to process the workpiece. Its core lies in constructing a "dual-light synergy + dual-response system". That is, by using an integrated dual-light system in conjunction with a dual-response polishing liquid, the photocatalytic oxidation response on the workpiece surface and the photochromic thickening response of the polishing liquid are triggered simultaneously, forming a dual-drive processing mechanism of "surface softening + medium thickening", thereby achieving dual optimization of processing efficiency and surface quality.

[0065] In this embodiment, the parameters for the workpiece and the processing device are set as follows:

[0066] The workpiece is an Inconel 718 sheet material with dimensions of 50 mm × 50 mm × 5 mm, an initial surface roughness Ra = 0.45 μm, an initial hardness HRC 42 (corresponding to Vickers hardness 430 HV), an initial residual stress of 95 MPa, and a surface oxide layer thickness of approximately 2 μm.

[0067] In some embodiments, the formulation (volume percentage) of the dual-response polishing slurry is as follows: PEG400 (i.e., polyethylene glycol with an average molecular weight of approximately 400 and a viscosity of 60 mPa·s / 25℃) 35 vol%; SiO2 / Al2O3 composite abrasive particles (mass ratio 1:1, particle size 100 nm) supported on TiO2 photocatalyst (loading 10%, abrasive particle mass ratio) 40 vol%; azobenzene-4-benzoic acid + β-cyclodextrin (molar ratio 1:2) 8 vol%; sodium polyacrylate 2 vol%; triethanolamine 3 vol%; deionized water 12 vol%.

[0068] The parameters of the combined light source module are: main ultraviolet light source 8, power density 30 mW / cm². 2 Auxiliary visible light source 12, power density 20 mW / cm² 2 Pulse frequency 5 Hz; infrared light source 11 power density 40 mW / cm² 2 .

[0069] The polishing parameters are: polishing pressure 0.2 MPa, workpiece rotation speed 1000 rpm, polishing head amplitude 8 μm, and processing time 25 min.

[0070] like Figure 2 As shown, the process of the nickel-based alloy polishing method is as follows:

[0071] Step 1: Workpiece pretreatment

[0072] The core purpose of the workpiece pretreatment is to remove surface oil, scale, and contaminants to ensure the uniformity of the photocatalytic reaction and the quality of processing. The specific steps are as follows:

[0073] 1-1. Ultrasonic Cleaning: Mix ethanol (purity ≥99.7%) and deionized water (conductivity ≤10μS / cm) at a volume ratio of 1:1. Place the workpiece in the ultrasonic cleaning tank and pour in the ethanol and deionized water mixture, ensuring the liquid level is 10 mm above the workpiece surface. Set the cleaning frequency to 40 kHz, power to 100 W, and temperature to 25-30℃ (28℃ in this example). Clean for 15-20 minutes (15 minutes in this example). During this period, manually rotate the workpiece once every 5 minutes to ensure thorough removal of oil stains from both sides. The principle of ultrasonic cleaning is: utilizing the cavitation effect of ultrasound, a large number of tiny bubbles are generated in the cleaning solution. The impact force generated when the bubbles burst can effectively remove oil stains and attached micro-contaminants from the workpiece surface.

[0074] 1-2. Pickling to Remove Oxide Scale: Prepare the pickling solution (5% dilute hydrochloric acid + 1% ammonium bifluoride + 94% deionized water, volume percentage), and control the temperature at 28±1℃. The dilute hydrochloric acid is obtained by diluting 37% hydrochloric acid 7 times. Completely immerse the cleaned workpiece in the pickling solution at a temperature of 25-30℃ for 3-5 minutes (3 minutes in this example). During this time, use PTFE tweezers to gently scrape the workpiece surface every minute to accelerate oxide scale removal. Immediately after pickling, remove the workpiece and rinse the surface with deionized water to remove the acid. The pickling principle is as follows: dilute hydrochloric acid is mainly used to dissolve oxides such as Fe2O3 and Cr2O3 in the oxide scale, while ammonium bifluoride reacts with NiO to form soluble fluoronickelates, accelerating oxide scale removal and simultaneously inhibiting excessive corrosion of the substrate by the pickling solution.

[0075] 1-3. Rinsing and Drying: Place the workpiece in a deionized water rinsing tank and rinse 3 times, 5 minutes each time. After the third rinse, check that the pH value of the rinsing water is ≥6.5. Then place it in a vacuum drying oven, set the temperature to 60℃ and the vacuum degree to -0.095 MPa, and dry for 10-15 minutes (10 minutes in this example).

[0076] Pretreatment effect testing: The particle size of surface contaminants was detected by a laser particle size analyzer to ensure that the particle size of surface contaminants is ≤5μm; the surface roughness was detected by a white light interferometer to ensure that Ra≤0.5 μm; and the removal of surface oxide scale was observed by a scanning electron microscope to ensure that the removal rate is ≥99%.

[0077] Step 2: Activation of polishing slurry

[0078] The core purpose of activating the polishing slurry is to trigger the initial thickening of the photochromic thickener and simultaneously activate the photocatalyst, preparing it for subsequent polishing. The specific steps are as follows:

[0079] 2-1. Polishing solution preparation: In a preparation container, add PEG400 and deionized water sequentially according to the formula ratio of the dual-response polishing solution, and stir in a 30℃ water bath (300 rpm) for 5 min until uniformly mixed; add sodium polyacrylate and triethanolamine, continue stirring for 10 min, and adjust the pH value to 9.0±0.2; add composite abrasive particles, and ultrasonically disperse for 30 min (frequency 40 kHz, power 150 W) to ensure that the abrasive particles do not agglomerate; finally, add azobenzene-cyclodextrin complex, stir at 50℃ for 30 min until completely dissolved, and cool to 25℃ for later use.

[0080] 2-2. Activation Operation:

[0081] (1) Start the supply metering pump 1 in the fluid circulation system, and deliver the prepared dual-light response polishing liquid from the stirring tank to the fluid nozzle 7 after being stabilized by the damper 2 and the back pressure valve 3. Spray it onto the workpiece processing area. The amount of polishing liquid injected is just enough to cover the workpiece processing area. The polishing liquid then flows to the collection area at the bottom of the workpiece and is recovered into the stirring tank by the recovery metering pump 18.

[0082] (2) Turn on the main ultraviolet light source 8 of the integrated dual light source device and set the power density to 30-40 mW / cm².

[0083] Pre-irradiation time: 5-10 min. The viscosity of the polishing fluid is monitored in real time by the viscosity sensor 9. Activation is complete when the viscosity reaches 200-300 mPa·s.

[0084] Activation effect testing: The viscosity of the polishing slurry was tested to ensure it reached 200-300 mPa·s; the isomerization rate of the photochromic thickener was tested using a UV-Vis spectrophotometer to ensure it was ≥85%; and the concentration of hydroxyl radicals was tested using an electron spin resonance analyzer to ensure it was ≥1.0×10⁻⁶. -4 mol / L.

[0085] In this embodiment, the pre-irradiation time was 8 minutes, during which viscosity was measured every 2 minutes. Activation was considered complete when the viscosity increased from the initial 60 mPa·s to 250 mPa·s. Simultaneously, an electron spin resonance (ESR) instrument was used to detect the concentration of hydroxyl radicals, ensuring that the concentration was ≥1.2 × 10⁻⁶. -4 mol / L, meaning the photocatalyst is qualified for activation.

[0086] Step 3: Dual-light co-polishing

[0087] Dual-light synergistic polishing is the core processing step. Continuous irradiation by the main ultraviolet light source 8 simultaneously softens the surface and thickens the medium, while viscosity compensation is achieved through an auxiliary visible light source 12, ensuring the stability and quality of the processing. The specific steps are as follows:

[0088] 3-1. Workpiece clamping: The pre-treated workpiece is clamped on the workpiece fixture 15. The fixture adopts an elastic clamping method to avoid damaging the workpiece surface. The flatness of the upper surface of the workpiece is ≤0.01 mm and the clamping accuracy is ±1.5μm, which is detected by a coordinate measuring machine.

[0089] 3-2. Processing Start-up:

[0090] The workpiece is rotated by the rotary drive assembly on the workpiece fixture 15, and the machine tool spindle drives the polishing head to polish the workpiece surface. In some embodiments, the polishing head and the workpiece rotate at different speeds. The speed difference between the polishing head and the workpiece is set to a reasonable value, and the two maintain a speed difference of 200 to 500 rpm to form a composite motion trajectory, ensuring uniform removal of material from the workpiece surface and uniform processing. The workpiece rotation speed is adjusted according to the workpiece size. For large workpieces (size > 100 mm), 500-1000 rpm is used; for small workpieces (size ≤ 100 mm), 1000-1500 rpm is used. The vibration frequency of the polishing head 10 is 30 kHz, and the vibration amplitude is 5-10 μm (8 μm in this embodiment), controlled by a vibration motor. The polishing pressure is 0.1-0.3 MPa (0.2 MPa in this embodiment), controlled by a pneumatic control system with a pressure accuracy of ±0.01 MPa. The processing time is set according to the initial roughness of the workpiece and the processing requirements. When the initial Ra = 0.5 μm, processing for 20-30 minutes can achieve Ra ≤ 0.02 μm; when the initial Ra = 1.0 μm, processing for 40-60 minutes can achieve Ra ≤ 0.02 μm.

[0091] 3-3. Dynamic Regulation:

[0092] (1) Control of main ultraviolet light source 8: continuous irradiation, the power density is dynamically adjusted according to the surface hardness monitoring results. When the surface hardness is >200 HV, the power density is increased in a gradient of 5 mW / cm², and the maximum is no more than 50 mW / cm².

[0093] (2) Control of auxiliary visible light source 12: In the initial state, the auxiliary visible light source 12 is turned on and the pulse irradiation mode is adopted (frequency 5 Hz, duty cycle 50%). Visible light can promote the conversion of cis azobenzene to trans azobenzene and reduce viscosity. Based on this principle, when the viscosity sensor 9 detects that the viscosity of the polishing fluid is greater than 300 mPa·s, the irradiation duty cycle of visible light is increased to further promote the conversion of cis azobenzene to trans azobenzene and reduce the viscosity of the polishing fluid. When the viscosity is less than 200 mPa·s, the irradiation duty cycle of visible light is reduced to reduce the conversion of cis azobenzene to trans azobenzene and increase the viscosity of the polishing fluid under the action of the main ultraviolet light source.

[0094] In this embodiment, the viscosity sensor 9 monitors the viscosity of the polishing slurry in real time (detection frequency 1 time / s). After 10 minutes of processing, the viscosity of the polishing slurry drops to 230 mPa·s (approaching the lower limit of the target range). By adjusting the aperture ratio of the auxiliary visible light source 12, the viscosity is finely adjusted. Using a pulse mode (single activation for 1 second, interval of 1 second), under the continuous thickening effect of the main ultraviolet light source, the viscosity rises back to 245 mPa·s after 30 seconds. This mode is maintained until the end of processing.

[0095] (3) Surface hardness control: The surface hardness monitor measures the surface hardness of the workpiece every 5 minutes (3 points are randomly selected). After processing for 15 minutes, the average hardness is 220 HV (higher than the target ≤200 HV). The power density of the main ultraviolet light source is increased to 35 mW / cm². 2 After 5 minutes, the hardness was tested again and dropped to 180 HV. This power was maintained until the processing was completed.

[0096] (4) Process monitoring: During the processing, the flow of polishing fluid is observed through a visual window to ensure that there is no splashing or local accumulation; the temperature of polishing fluid is monitored by an infrared thermometer and maintained at 25-28℃.

[0097] In this embodiment, the linkage control of light source parameters and processing parameters is realized through the development of host computer software based on LabVIEW. Parameters such as viscosity, surface hardness, and processing time are displayed in real time, and real-time adjustment of parameters and fault alarms are supported.

[0098] Step 4: Finishing and Cleaning

[0099] The core purpose of finishing and cleaning is to reduce the viscosity of the polishing fluid, remove residual media from the workpiece surface, and ensure processing quality. The specific steps are as follows:

[0100] 4-1. Viscosity Reduction: 3-5 minutes before the end of processing (4 minutes in this example), turn off the main ultraviolet light source 8 and the auxiliary visible light source 12, turn on the infrared light source 11, and set the power density to 30-60 mW / cm² (40 mW / cm² in this example). 2 When the viscosity of the polishing slurry drops to 50-100 mPa·s (65 mPa·s in this embodiment), the infrared light source 11 is turned off. In this embodiment, the irradiation time of the infrared light source 11 is 4 minutes. The principle of viscosity reduction: The thermal effect of the infrared light source 11 increases the temperature of the polishing slurry. For every 10°C increase, the viscosity of the PEG-based liquid decreases by 15-20%, thereby reducing viscosity and facilitating the removal of residual media.

[0101] 4-2. Workpiece Removal and Cleaning: Stop the rotation of the worktable and the vibration of the polishing head (10), and remove the workpiece. Use a high-pressure water gun at a pressure of 0.5 MPa to rinse the surface of the workpiece for 5 minutes to remove most of the residual media; the rinsing direction should be at a 45° angle to the surface of the workpiece to avoid vertical rinsing that could cause residual media to embed into the surface; then use a lint-free cloth soaked in anhydrous ethanol (purity ≥99.7%) to gently wipe the surface of the workpiece to remove trace amounts of residue; finally, place the cleaned workpiece in a vacuum drying oven and dry it at 60℃ and -0.09MPa for 10 minutes to remove surface moisture.

[0102] Step 5: Processing quality inspection

[0103] 5-1. Surface roughness inspection: White light interferometry is used to inspect surface roughness. The number of inspection points is ≥10, and the average value is taken to ensure that Ra≤0.02 μm. In this embodiment, the white light interferometer inspects 10 points, and the obtained surface roughness Ra values ​​are 0.017, 0.018, 0.019, 0.017, 0.018, 0.019, 0.018, 0.017, 0.019, and 0.018 μm, respectively, with an average value of 0.018 μm, which meets the requirement of Ra≤0.02 μm. SEM observation of the surface morphology shows no defects such as scratches or pits.

[0104] 5-2. Surface Hardness and Oxide Layer: The hardness of the surface oxide layer and the substrate of the workpiece were tested using a microhardness tester. In this embodiment, the surface oxide layer hardness was measured to be 180±5 HV, while the substrate hardness remained at 430 HV (no significant decrease); the oxide layer thickness was observed to be 25 nm using TEM, with a thickness uniformity error of ±3 nm (10 observation points). The main components of the oxide layer were NiO and Cr2O3 (detected by X-ray diffraction).

[0105] 5-3. Residual stress detection: Residual stress was detected using an X-ray stress analyzer, with the sin²ψ method. At least 5 points were tested, and the average value was taken to ensure residual stress ≤ 50 MPa. In this embodiment, the X-ray stress analyzer detected 5 points, with residual stresses of 40, 42, 43, 41, and 44 MPa respectively, and an average value of 42 MPa, a 55.8% reduction from the initial value. This residual stress was residual compressive stress (improving fatigue life).

[0106] 5-3. Dimensional accuracy inspection: The dimensional accuracy of the workpiece is inspected using a coordinate measuring machine to ensure that the dimensional error is ≤ ±5 μm.

[0107] 5-4. Surface integrity inspection: The surface morphology is observed using a scanning electron microscope to ensure that there are no defects such as scratches and pits; the oxide layer thickness and grain boundary state are observed using a transmission electron microscope to ensure that the oxide layer thickness uniformity error is ≤ ±5nm and the grain boundary damage rate is ≤1%.

[0108] In this embodiment, the workpiece mass before processing was 102.568 g, and the mass after processing was 102.403 g, with a mass difference of 0.165 g. The material removal amount was 0.165 / 8.2 = 0.0201 cm³, and the processing efficiency was 0.0201 cm³ / (25 min × 0.05 m × 0.05 m) = 12 μm / h, which is 60% higher than that of single photocatalytic modification processing (7.5 μm / h) and 30.4% higher than that of single phototriggered thickening processing (9.2 μm / h).

[0109] In this embodiment, the settling rate of the polishing slurry after processing is 4.2% / 24 h, the reversibility of the photochromic molecules is 96% (cis-trans isomer conversion rate detected by UV-Vis), and the viscosity fluctuation range is ±8 mPa·s, which meets the requirements for recycling.

[0110] The principle of the dual-light collaborative mechanism constructed in this embodiment is as follows:

[0111] The dual-light synergistic mechanism refers to the simultaneous activation of two complementary photoresponse processes during the processing stage using a main ultraviolet light source 8: photocatalytic surface modification and photo-triggered thickening of the polishing slurry. Simultaneously, an auxiliary visible light source 12 fine-tunes the isomer ratio of photochromic molecules, achieving precise viscosity compensation. In the final polishing stage, an infrared light source 11 is activated to reduce viscosity, facilitating cleaning. The two response processes work together: the softening layer reduces abrasive cutting resistance, improving processing efficiency; the stabilized, thickened polishing slurry ensures uniform abrasive action, improving surface quality, ultimately achieving a dual optimization of processing efficiency and surface quality, resulting in a synergistic processing effect. The theoretical foundations involved in the processing include photocatalytic oxidation theory, photochromic isomerization theory, shear thickening rheology theory, and the coupling and synergistic theory of these three, as detailed below:

[0112] (1) Mechanism of photocatalytic surface modification

[0113] This embodiment uses TiO2 or ZnO as the photocatalyst, which belongs to wide bandgap semiconductors (TiO2 has a bandgap energy E). g =3.2 eV, E of ZnO g =3.37 eV), according to formula (1), when the wavelength of the irradiated light λ≤λ0, the valence band electrons of the photocatalyst will be excited to the conduction band, forming photogenerated electrons (e - ) and photogenerated holes (h + ):

[0114] λ0 = hc / E g Equation (1)

[0115] Where λ0 is the critical wavelength; h is Planck's constant (6.626 × 10⁻⁶). -34 J·s), c is the speed of light (3×10⁻⁶ s), and c is the speed of light (3×10⁻⁶ s).8 m / s), E g ν is the band gap energy (eV) of the photocatalyst.

[0116] Calculations show that the critical excitation wavelength of TiO2 is λ_TiO2 = 1240 eV·nm / 3.2 eV = 387 nm, and the critical excitation wavelength of ZnO is λ_ZnO = 1240 eV·nm / 3.37 eV = 368 nm. Therefore, selecting a main ultraviolet light source with a wavelength range of 300-380 nm and a peak wavelength of 365 nm can simultaneously activate both TiO2 and ZnO photocatalysts.

[0117] Photogenic hole (h) + It possesses extremely strong oxidizing properties (redox potential of approximately +2.7 eV), and can directly oxidize OH groups adsorbed on the surface of the photocatalyst. - Or H2O molecules, generating hydroxyl radicals (·OH), as shown in reaction (2); photogenerated electrons (e - It combines with O2 in the air to generate superoxide anions (·O2). - As shown in reaction formula (3):

[0118] h + + OH - → ·OH Formula (2)

[0119] e - + O2 → ·O2 - Equation (3)

[0120] Hydroxyl radicals (·OH) and superoxide anions (·O2) - All of them have extremely high oxidation activity (the redox potential of ·OH is about +2.8 eV), which can rapidly oxidize the metal elements such as Ni, Cr, and Fe on the surface of nickel-based alloys to form low-hardness oxides (such as NiO, Cr2O3, and Fe2O3), as shown in reaction formulas (4)-(6):

[0121] Ni + 2·OH → NiO + H2O Formula (4)

[0122] 2Cr + 6·OH → Cr2O3 + 3H2O Equation (5)

[0123] 2Fe + 6·OH → Fe2O3 + 3H2O (Equation 6)

[0124] The generated oxide layer has a thickness of 10-50 nm and a Vickers hardness of ≤200 HV, which is much lower than the hardness of the nickel-based alloy matrix (HRC 38-45, corresponding to a Vickers hardness of about 400-500 HV), thus significantly reducing the cutting resistance of abrasive grains on the workpiece surface and inhibiting work hardening.

[0125] To achieve precise control of oxide layer thickness, this invention regulates the photocatalytic reaction rate through the following mechanism:

[0126] ①. The photocatalyst is loaded onto the surface of the abrasive grains to form a "abrasive grain-photocatalyst" composite structure. The contact distance between the photocatalyst and the workpiece surface is closer, and the utilization rate of active free radicals is higher.

[0127] ②. By adjusting the power density of the main ultraviolet light source 8 (20-50 mW / cm²), 2 This regulates the generation rate of photogenerated carriers, thereby regulating the production of active free radicals and the oxidation reaction rate.

[0128] The pH of the polishing solution is adjusted to 8-10 by using a pH adjuster. This pH range can suppress the recombination of photogenerated carriers (recombination rate ≤15%), improve photocatalytic efficiency, and avoid corrosion of the workpiece surface by strong acid or strong alkali environments.

[0129] (2) Photo-triggered thickening mechanism of polishing fluid

[0130] In this embodiment, a complex of azobenzene-4-benzoic acid and cyclodextrin is used as a photochromic thickener. Its thickening mechanism is based on the cis-trans isomerism of azobenzene molecules and the host-guest inclusion effect of cyclodextrin, as detailed below:

[0131] ① Azobenzene exists in two isomers, cis and trans. Under ultraviolet light irradiation, trans-azobenzene (stable state) transforms into cis-azobenzene (metastable state), resulting in a change in molecular configuration and an increase in dipole moment (the dipole moment of trans-azobenzene is approximately 0.5 D, while that of cis-azobenzene is approximately 3.1 D). Intermolecular forces (hydrogen bonds and van der Waals forces) are significantly enhanced, thereby increasing the viscosity of the dual-response polishing slurry. Furthermore, visible light in the wavelength range of 400–700 nm can trigger the reverse isomerization reaction of azobenzene-4-benzoic acid. Under visible light irradiation, cis-azobenzene can reversibly revert back to trans-azobenzene, restoring the molecular configuration to a stable state, reducing the dipole moment, and weakening intermolecular forces, leading to a decrease in the viscosity of the polishing slurry, achieving precise viscosity compensation and adjustment. Therefore, when viscosity fluctuates, the viscosity of the polishing slurry can be adjusted using visible light without affecting the photocatalytic reaction process.

[0132] ② Cyclodextrin molecules have a hollow cylindrical structure with a hydrophobic inner cavity and a hydrophilic outer cavity. The hydrophobic group of trans-azobenzene can be embedded in the inner cavity of cyclodextrin to form a stable host-guest inclusion complex. Under ultraviolet light irradiation, trans-azobenzene is converted to the cis configuration. Due to the increased steric hindrance of cis-azobenzene, it cannot be embedded in the inner cavity of cyclodextrin. The host-guest inclusion complex dissociates, and the released azobenzene molecules aggregate with each other through intermolecular forces to form a network structure, resulting in a significant increase in the viscosity of the polishing slurry.

[0133] ③ Under the action of a shear field, the SiO2 / Al2O3 composite abrasive particles in the polishing slurry will agglomerate, forming a shear-thickened body. This, combined with the photo-triggered thickening effect, constructs a "photo-triggered + shear-induced" dual thickening system, further improving the viscosity stability and abrasive particle holding force of the polishing slurry. The core driving force of shear-induced thickening is mechanical shear force, triggered by the mechanical shear field generated by the workpiece rotation (500-1500 rpm). This is a mechanically driven rheological effect and has no direct triggering relationship with ultraviolet, visible, or infrared light. Irradiation will not directly cause abrasive particle agglomeration or deagglomeration. The viscosity of the polishing slurry can also be adjusted by regulating the shear force. For example, increasing the polishing rotation speed or providing vibration to the polishing head can increase the shear force. The total thickening effect = photo-triggered thickening (light-controlled) + shear-induced thickening (shear force controlled).

[0134] In this embodiment, shear-induced thickening does not merely increase the thickening amplitude, but rather complements light-triggered thickening by "dynamically adapting to the shear field and constructing a stable particle structure," thereby suppressing viscosity fluctuations at their source and improving viscosity stability. The specific reasons are as follows:

[0135] 1) Shear-induced thickening is a dynamic compensation that counteracts viscosity decay during processing. During polishing, the static basic viscosity is provided solely by photochromic molecules, which will experience viscosity decay and fluctuations under continuous shear force. Workpiece rotation (500-1500 rpm) and polishing head vibration (30 kHz) create a real-time changing shear field. Shear-induced thickening can dynamically respond to the shear rate. The stronger the shear force, the denser the shear-thickened body formed by the agglomeration of SiO2 / Al2O3 composite abrasive particles, automatically compensating for the viscosity loss caused by photo-triggered thickening, keeping the total viscosity stable within the target range of 200-300 mPa·s.

[0136] 2) Shear thickener locks in the abrasive grain structure, eliminating viscosity fluctuations caused by uneven dispersion.

[0137] The shear thickener formed by abrasive agglomeration under shear field uniformly coats the composite abrasive particles and fixes their spatial structure, thus avoiding viscosity fluctuations caused by abrasive particle sedimentation, agglomeration, and uneven dispersion. Photo-triggered thickening is responsible for molecular-level basic thickening, while shear-induced thickening is responsible for particle-level structural reinforcement. The two-layer system prevents viscosity from fluctuating significantly with abrasive particle state and processing time.

[0138] 3) The dual-thickening system doubles the anti-interference ability and improves long-term stability.

[0139] Photo-triggered thickening is easily affected by temperature and light uniformity, resulting in large viscosity fluctuations; shear-triggered thickening is easily affected by shear rate fluctuations, resulting in uncontrollable viscosity; when the two are combined, photo-triggered thickening determines the basic viscosity, while shear-induced thickening stabilizes the dynamic viscosity, together resisting the interference of shear, temperature, and light, ultimately achieving a stable viscosity fluctuation of ≤±8 mPa·s.

[0140] Based on the above theory, this embodiment further optimizes the light-triggered thickening effect through the following design:

[0141] The optimal molar ratio of azobenzene-4-benzoic acid to cyclodextrin is 1:(1-3), preferably 1:2, to ensure the stability of host-guest inclusion and the reversibility of isomerization.

[0142] Among α-, β-, and γ-cyclodextrins, the β-cyclodextrin exhibits the highest degree of matching between its luminal size (internal diameter approximately 0.6 nm) and the size of the azobenzene molecule (length approximately 0.8 nm), resulting in the largest inclusion constant (approximately 10). 4 β-cyclodextrin (L / mol) is the most effective thickening agent, therefore, β-cyclodextrin was chosen in this embodiment.

[0143] The complex of azobenzene-4-benzoic acid and cyclodextrin can achieve a solubility of greater than or equal to 20 g / L in the base liquid, which can avoid molecular aggregation and ensure uniform thickening. This high solubility depends on the combined effect of the following factors:

[0144] 1) Hydrophilic modification of molecular structure: Azobenzene-4-benzoic acid is selected as the photochromic unit. The carboxyl group (-COOH) on its molecule can enhance the hydrophilicity of the molecule and greatly improve its solubility in PEG base liquid, solving the problem that ordinary azobenzene derivatives are difficult to dissolve in polar base liquid.

[0145] 2) Preferred type of cyclodextrin: β-cyclodextrin is combined with azobenzene-4-benzoic acid. The structure of β-cyclodextrin, with its hydrophilic outer cavity and hydrophobic inner cavity, can not only stably encapsulate the hydrophobic azobenzene unit, but also promote the uniform dissolution of the entire complex in the PEG base solution by means of its own hydrophilicity.

[0146] 3) Precise control of the molar ratio of the complex: control the ratio of azobenzene-4-benzoic acid to cyclodextrin to 1:1~1:3, ensure sufficient inclusion reaction without excess unreacted raw materials, avoid the formation of insoluble by-products or agglomerates, and ensure the pure phase and high solubility of the complex.

[0147] 4) Dedicated preparation process ensures: The process of preparing the compound with a mixed solvent of ethanol / water → removing ethanol by vacuum distillation → vacuum drying is adopted to obtain a pure phase complex with molecular uniformity, without poorly soluble particles caused by physical mixing, and the dissolution rate and solubility are significantly improved.

[0148] 5) Base solution and dissolution process compatibility: The base solution is PEG400-600 (polarity matched with the complex), and a dissolution process of heating and stirring at 50-60℃ (300-500 rpm) is adopted to further promote the full dissolution of the complex and achieve a solubility target of ≥20 g / L.

[0149] 6) Dispersant-assisted stabilization: Sodium polyacrylate dispersant is added to the polishing solution to inhibit the re-aggregation of the dissolved complex molecules through steric hindrance, thus maintaining the stability of the dissolved state.

[0150] Photochromic thickeners exhibit an isomerization response time ≤10 s, enabling rapid viscosity control and meeting the real-time compensation requirements during processing. This rapid response and high solubility depend on the combined effects of the following factors:

[0151] 1) Optimal molecular structure: Azobenzene-4-benzoic acid is used as the photoresponsive unit. The carboxyl substitution makes its photoisomerization activity much higher than that of ordinary azobenzene, and the cis-trans configuration switching rate is faster.

[0152] 2) Precise matching of cyclodextrin: β-cyclodextrin is selected because its internal cavity size has the highest matching degree with azobenzene-4-benzoic acid molecules, resulting in fast host-guest inclusion / dissociation rates and no response delay caused by steric hindrance.

[0153] 3) Precise optimization of molar ratio: Controlling the ratio of azobenzene-4-benzoic acid to cyclodextrin to 1:1~1:3 ensures inclusion stability while avoiding excessive cyclodextrin from hindering isomer switching and guaranteeing response rate.

[0154] 4) Complex preparation process: The process involves solution mixing → vacuum distillation → vacuum drying to achieve molecular-level uniform composites without physical agglomeration. Photoirradiation can directly trigger photoisomerization without diffusion delay.

[0155] 5) Polishing fluid system compatibility: The solubility of the complex in PEG base fluid is ≥20g / L. It can achieve molecular-level dispersion with sodium polyacrylate dispersant and light-triggered activation without concentration gradient delay.

[0156] 6) Precise matching of light source wavelength: The peak wavelength of the main ultraviolet light source is 365nm, which is perfectly matched with the excitation wavelength of azobenzene isomerization, resulting in high photon absorption efficiency and further shortening the response time.

[0157] (3) Two-light cooperative coupling mechanism

[0158] The dual-light synergistic effect in this embodiment is not a simple superposition of two independent processes, but rather achieves precise matching and coordinated control of "surface softening" and "medium thickening" through the synergistic effect of the main ultraviolet light source 8, the auxiliary visible light source 12, and the infrared light source 11. The coupling mechanism is as follows:

[0159] Timing Synergy: During the polishing slurry activation stage, the main ultraviolet light source 8 simultaneously activates the photocatalyst and the photochromic thickener, enabling the oxide layer formation and polishing slurry thickening to start synchronously; during the polishing stage, the main ultraviolet light source 8 continuously irradiates to maintain the stability of the oxide layer thickness and polishing slurry viscosity, while the auxiliary visible light source 12 finely adjusts the isomer ratio of the photochromic molecules to achieve precise viscosity compensation; in the finishing stage, the infrared light source 11 is turned on to reduce the viscosity of the polishing slurry, facilitating workpiece cleaning.

[0160] Spatial coordination: The integrated dual light source device has an adjustable illumination angle of 0-90°, ensuring that the light simultaneously covers the workpiece processing area and the polishing fluid action area, so that the photocatalytic reaction and the photo-triggered thickening reaction can be carried out synchronously in the same space.

[0161] Performance Synergy: The low hardness of the surface oxide layer reduces the cutting resistance of the abrasive grains, enabling them to achieve uniform and efficient micro-cutting in a stable and thickened polishing slurry; the stable and thickened polishing slurry ensures the uniform distribution and controllable movement of the abrasive grains, avoiding over-cutting or under-cutting of the oxide layer by the abrasive grains, and ensuring the stability of the oxide layer thickness and the uniformity of the processing.

[0162] Coordinated regulation: Data is collected in real time by viscosity sensor 9 and surface hardness monitor 14 and fed back to power regulator to dynamically adjust the power and irradiation mode of each light source, so as to realize the linkage between viscosity compensation and oxide layer thickness control and ensure the stability of the processing.

[0163] (4) Shear thickening rheological model

[0164] To accurately describe the rheological properties of the polishing slurry, this embodiment uses the Carreau rheological model to fit the viscosity-shear rate relationship of the polishing slurry. The model formula is as follows:

[0165] η(γ') = η∞ + (η0 - η∞) / [1 + (λγ') n Equation (7)

[0166] Where η(γ') is the viscosity at shear rate γ', η0 is the zero shear viscosity, η∞ is the viscosity at infinite shear rate, λ is the characteristic time constant, and n is the flow behavior exponent.

[0167] The polishing slurry formulation was optimized through experiments to ensure that the Carreau model parameters met the following requirements: η0 = 50-100 mPa·s, η∞ = 200-300 mPa·s, λ = 0.1-0.5 s, n = 0.3-0.5, ensuring that the polishing slurry could operate at shear rates of 500-1000 s⁻¹. -1 Under a shear field (corresponding to a polishing head vibration frequency of 30 kHz and a workpiece rotation speed of 500-1500 rpm), the viscosity can be stabilized in the range of 200-300 mPa·s, meeting the requirements of precision machining.

[0168] Example 3

[0169] A method for optimizing a dual-light-responsive polishing slurry is provided to improve the formulation of the dual-light-responsive polishing slurry provided in Example 2. The dual-light-responsive polishing slurry is the core carrier for achieving synergistic processing with both light and light, and must simultaneously meet the three functional requirements of photocatalysis, photo-triggered thickening, and shear-thickening, while ensuring good compatibility among its components. The specific formulation design and optimization are as follows:

[0170] (1) Selection and optimization of base liquid

[0171] The core function of the base liquid is to provide a shear-thickening matrix and disperse the various components; its performance directly affects the rheological properties and stability of the polishing slurry. In this embodiment, PEG400-600 was chosen as the base liquid for the following reasons:

[0172] PEG has good chemical stability, biocompatibility and solubility, and does not react chemically with photochromic thickeners, photocatalysts, abrasive particles and other components.

[0173] The viscosity of PEG increases with increasing molecular weight. PEG with a number average molecular weight of 400-600 has a viscosity of 50-100 mPa·s at 25℃, which can provide a suitable matrix viscosity for shear thickening.

[0174] PEG has good moisturizing and lubricating properties, which can reduce friction between abrasive particles and the workpiece surface, reduce heat generation during processing, and avoid thermal damage to the workpiece surface.

[0175] To further optimize the performance of the base liquid, the present invention performs vacuum drying pretreatment on PEG (60℃, -0.09 MPa, 8-12 h) to remove moisture (moisture content ≤0.5%), thereby avoiding the influence of moisture on the photocatalytic reaction and the photochromic thickening reaction.

[0176] (2) Design and optimization of composite abrasive particles

[0177] Composite abrasive particles are the core component for material removal and also serve as a carrier for photocatalysts; their performance directly affects processing efficiency and photocatalytic effect. This invention uses SiO2 / Al2O3 composite particles to support a TiO2 / ZnO photocatalyst, with the specific design as follows:

[0178] Abrasive material selection: SiO2 has the advantages of moderate hardness (Mohs hardness 7), good chemical stability, and easy surface modification, while Al2O3 has the advantages of high hardness (Mohs hardness 9) and good wear resistance. Combining the two in a mass ratio of (1~2):1 can balance cutting efficiency and surface quality.

[0179] Abrasive particle size optimization: Select composite abrasive particles with a particle size distribution of 50-200 nm and D50 (called median particle size, the particle size value corresponding to the cumulative distribution percentage reaching 50%) = 100±10 nm. This particle size range can achieve efficient micro-cutting while avoiding scratches on the workpiece surface by large abrasive particles.

[0180] Photocatalyst loading: TiO2 or ZnO photocatalysts are loaded onto the surface of composite abrasives using the sol-gel method. The loading amount is 5-15% of the mass of the composite abrasives. The particle size of the loaded photocatalyst is 5-20 nm, and the coverage is ≥90%, thus avoiding the influence of free photocatalysts on the performance of the polishing slurry.

[0181] Dispersion stability optimization: By adding sodium polyacrylate dispersant (molecular weight 5000-10000), the steric hindrance effect is used to inhibit abrasive particle agglomeration, so that the settling rate of polishing fluid is ≤5% / 24 h.

[0182] (3) Design and optimization of photochromic thickeners

[0183] Photochromic thickeners are the core components for achieving photo-triggered thickening, and their performance directly affects the viscosity control effect and service life of the polishing slurry. This invention employs a complex of azobenzene-4-benzoic acid and cyclodextrin, specifically designed as follows:

[0184] ①. Selection of azobenzene derivatives: Azobenzene-4-benzoic acid has good photoresponsiveness, solubility and stability. Its carboxyl group can form hydrogen bonds with the hydroxyl group of cyclodextrin, which enhances the stability of host-guest inclusion.

[0185] ②. Cyclodextrin selection: β-cyclodextrin has the highest matching degree between its internal cavity size and azobenzene molecule, the largest inclusion constant, and the best thickening effect.

[0186] ③. Molar ratio optimization: The molar ratio of azobenzene-4-benzoic acid to cyclodextrin is 1:(1~3). When the molar ratio is too low, the inclusion of host and guest components is insufficient, resulting in poor thickening effect. When the molar ratio is too high, excessive cyclodextrin will increase the viscosity of the polishing slurry and affect the fluidity during processing.

[0187] ④. Complex preparation: The complex was prepared by solution mixing-reduced pressure distillation-vacuum drying to ensure that azobenzene-4-benzoic acid and cyclodextrin were fully combined and to avoid performance instability caused by physical mixing.

[0188] (4) Selection and optimization of additives

[0189] The additives include dispersants and pH adjusters, which enhance the stability and light response efficiency of the polishing slurry. The specific design is as follows:

[0190] Dispersant: Sodium polyacrylate (molecular weight 5000-10000) is selected and added at a rate of 0.5-2 vol%. The carboxyl groups on its molecular chain can be adsorbed on the surface of the abrasive particles, forming electrostatic repulsion and steric hindrance, thus inhibiting the abrasive particle aggregation.

[0191] pH adjuster: Select triethanolamine, add 0.5-3 vol%, and adjust the pH of the polishing solution to 8-10. This pH range can improve the separation efficiency of photogenerated carriers of the photocatalyst, while avoiding corrosion of the workpiece surface.

[0192] Additive compatibility: The dispersant and pH adjuster are highly compatible with the base liquid, composite abrasives, and photochromic thickeners, and will not undergo chemical reactions or agglomeration.

[0193] (5) Orthogonal optimization experiment of polishing slurry formulation

[0194] To obtain the optimal polishing slurry formulation, this invention employs an orthogonal experimental method, using surface roughness Ra, processing efficiency, viscosity fluctuation range, and settling rate as evaluation indicators. A three-level orthogonal experiment was conducted on four factors: base liquid type (PEG400, PEG500, PEG600), composite abrasive particle ratio (35 vol%, 40 vol%, 45 vol%), photochromic thickener ratio (5 vol%, 8 vol%, 10 vol%), and pH value (8, 9, 10). Analysis of the orthogonal experiments revealed that the optimal formulation combination is: base liquid PEG400, composite abrasive particle ratio of 40 vol%, photochromic thickener ratio of 8 vol%, and pH value of 9. Under this formulation, the polishing slurry exhibits the best overall performance: surface roughness Ra = 0.018 μm, processing efficiency = 12.0 μm / h, viscosity fluctuation range = ±8 mPa·s, and settling rate = 4.2% / 24 h.

[0195] To verify the stability of the polishing slurry used in this embodiment, a verification experiment was conducted, as follows:

[0196] Using the polishing slurry formulation and processing parameters provided in this embodiment, an Inconel 718 planar workpiece was continuously processed 50 times (after each processing, the polishing slurry was filtered through a 0.22 μm filter membrane and replenished with 1% volume of deionized water and 0.5% volume of azobenzene-cyclodextrin complex). The performance of the polishing slurry and the processing quality of the workpiece were tested after each processing. The experimental results are shown in Table 1.

[0197] Table 1. Comparison of performance changes in dual-response polishing slurry during recycling.

[0198] Loop count Polishing fluid viscosity (mPa·s) Settlement rate (% / 24 h) Photochromic reversibility (%) Workpiece Ra (μm) Residual stress (MPa) Processing efficiency (μm / h) 1 250 4.2 96 0.018 42 12.0 10 248 4.3 95 0.019 43 11.8 20 245 4.5 94 0.020 45 11.5 30 242 4.7 93 0.020 46 11.2 40 238 4.8 92 0.021 48 10.9 50 235 4.9 91 0.022 50 10.5

[0199] As shown in the table above, after 50 cycles, the viscosity of the dual-response polishing slurry decreased from 250 mPa·s to 235 mPa·s (a decrease of 6%), the settling rate was ≤4.9% / 24 h, and the photochromic reversibility was ≥91%. The workpiece processing quality still met the requirements of Ra≤0.025 μm, residual stress≤50 MPa, and processing efficiency≥10.5 μm / h, proving that the dual-response polishing slurry has excellent stability, can be used repeatedly for a long time, and reduces processing costs.

[0200] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A polishing method for nickel-based alloys based on photocatalysis-photothickening synergy, comprising: Spray polishing liquid onto nickel-based alloy workpieces or immerse the workpieces in polishing liquid; Polishing operation on the surface of a workpiece; characterized in that the polishing liquid is a dual-response polishing liquid, comprising a base liquid, composite abrasive particles and a photochromic thickener; the composite abrasive particles comprise an abrasive matrix and a photocatalyst supported on the surface of the abrasive matrix; the photochromic thickener is an inclusion complex formed by an azobenzene derivative and cyclodextrin; During the polishing process, the polishing slurry on the workpiece surface is irradiated with ultraviolet light. The ultraviolet light simultaneously triggers photocatalytic oxidation of the workpiece surface and isomerization viscosity adjustment of the photochromic thickener. At the same time, the polishing slurry on the workpiece surface is irradiated with visible light pulses. By adjusting the intensity of the visible light and / or the duty cycle of the irradiation, the viscosity of the dual-response polishing slurry is controlled to remain within the preset viscosity target range.

2. The nickel-based alloy polishing method according to claim 1, characterized in that: During the polishing process, the surface hardness of the workpiece is detected; the reaction rate of photocatalytic oxidation is controlled by adjusting the intensity of ultraviolet light so that the surface hardness of the workpiece is less than or equal to the target hardness threshold; when the viscosity is greater than the target viscosity range, the intensity of visible light and / or the irradiation duty cycle are increased; when the viscosity is less than the target viscosity range, the intensity of visible light and / or the irradiation duty cycle are decreased.

3. The nickel-based alloy polishing method according to claim 1, characterized in that: After the polishing operation is completed, infrared light is used to irradiate the workpiece surface to reduce the viscosity of the residual dual-response polishing fluid on the workpiece surface through the thermal effect. Rinse the workpiece to remove any residual polishing solution.

4. The nickel-based alloy polishing method according to claim 1, characterized in that: Before polishing begins, the workpiece sprayed with or immersed in the dual-response polishing slurry is pre-irradiated with ultraviolet light to perform combined activation of photocatalysis and photothickening. The activation target of photocatalysis is that the concentration of hydroxyl radicals in the dual-response polishing slurry is greater than or equal to the concentration threshold. The activation target of photothickening is that the viscosity of the dual-response polishing slurry is within the viscosity target range, which is 200 mPa·s to 300 mPa·s.

5. The nickel-based alloy polishing method according to claim 1, characterized in that: The base liquid is polyethylene glycol with a number average molecular weight of 400-600; the abrasive matrix is ​​a mixture of SiO2 and Al2O3 abrasive particles; the photocatalyst is TiO2 and / or ZnO, which is loaded onto the surface of the abrasive matrix by a sol-gel method; the mass fraction of the photocatalyst in the composite abrasive particles is 5%-15%.

6. The nickel-based alloy polishing method according to claim 5, characterized in that: The particle size of the composite abrasive is 50 nm to 200 nm.

7. The nickel-based alloy polishing method according to claim 1, characterized in that: The molar ratio of the azobenzene derivative to cyclodextrin is 1:(1-3).

8. The nickel-based alloy polishing method according to claim 1, characterized in that: The dual-response polishing slurry also includes a pH adjuster and a dispersant to inhibit abrasive particle aggregation; the dispersant is sodium polyacrylate; the pH value of the dual-response polishing slurry is 8-10.

9. The nickel-based alloy polishing method according to claim 1, characterized in that: In the dual-response polishing slurry, the volume fraction of the composite abrasive particles is 35 vol% to 45 vol; and the volume fraction of the photochromic thickener is 5 vol% to 10 vol.

10. A nickel-based alloy polishing device based on photocatalysis-photothickening synergy, characterized in that: The device is used to perform the nickel-based alloy polishing method according to claim 1; the nickel-based alloy polishing device includes a circulating liquid supply module, an industrial five-axis machine tool (6), a combined light source module, a detection module, a polishing head (10), and a workpiece fixture (15); the worktable of the industrial five-axis machine tool (6) is provided with a polishing tank; the workpiece fixture is installed in the polishing tank; the polishing head (10) is installed on the spindle of the industrial five-axis machine tool (6); the industrial five-axis machine tool (6) is configured to polish the workpiece (13) being processed using the polishing head (10); The circulating liquid supply module includes a polishing liquid output component and a polishing liquid return component; the polishing liquid output component includes a supply metering pump (1), a damper (2), a back pressure valve (3), a pressure gauge (4), a pressure regulating valve (5), and a fluid nozzle (7) connected in sequence; the fluid nozzle (7) is located above the polishing tank and faces the workpiece fixture; the polishing liquid return component includes a drain port (16), a recovery metering pump (18), a stirring tank, and a return pipe (21) connected in sequence; the drain port (16) is located inside the polishing tank; the return pipe (21) is connected to the supply metering pump (1); The combined light source module includes a main ultraviolet light source (8), an infrared light source (11), and an auxiliary visible light source (12) facing the workpiece fixture (15); the detection module includes a viscosity sensor (9) for detecting the viscosity of the polishing fluid, and a surface hardness monitor (14) for detecting the hardness of the polished surface of the workpiece.

Images