Preparation method of fine structure surface RB-SiC friction pair based on throttling expansion self-suction multiphase jet flow

Abstract

The invention discloses a preparation method of a fine structure surface RB-SiC friction pair based on throttling expansion self-suction type multiphase jet flow, and aims to solve the technical problems of poor uniformity and easy generation of microcracks in fine machining of an RB-SiC material. According to the method, negative pressure is formed through the throttling expansion effect generated when micron diamond gas jet flows through a Laval nozzle, nano diamond slurry with the shear thinning characteristic is automatically sucked in, and cell type diamond cluster abrasive multiphase jet is formed through online mixing; when the surface of a workpiece is impacted, grinding material clusters are depolymerized, uniform fragile region erosion of the material is achieved through the micron diamond, flexible finishing is conducted by means of ploughing and micro-cutting effects of the nano diamond, and therefore generation of micro cracks is synergistically inhibited. And in combination with a mask plate technology, the preparation of the high-quality fine structure surface is finally realized. Through the synergistic effect of multi-phase jet flow online mixing and cell type grinding materials, the quality of the machined surface is remarkably improved, and the method is suitable for preparing the high-performance RB-SiC friction pair.

Description

Technical Field

[0001] This invention relates to the field of microstructure surface processing technology, specifically a method for preparing microstructure surface RB-SiC friction pairs based on throttling expansion self-absorbing multiphase jet. Background Technology

[0002] Wear and failure of reaction sintered silicon carbide (RB-SiC) sealing pairs in deep-sea oil and gas drilling and production can easily lead to multiple consequences such as oil leaks, well abandonment, and casualties. It has become one of the key issues affecting the safe operation of my country's existing deep-sea oil and gas equipment.

[0003] Currently, the tribological properties of RB-SiC sealing pairs can be effectively improved by machining microstructures of specific shapes, sizes, and arrangements on their surfaces. However, the extreme environment of the deep sea places extremely high demands on the machining quality of these microstructures.

[0004] Micro-abrasive air jet machining (AJM) offers significant advantages such as non-contact operation, no tool wear, no heat-affected zone, controllable material removal rate, high process stability, low cost, and chamfering of microstructured edges. Using the crack propagation stress intensity factor K as a criterion, uniform erosion removal of RB-SiC composite materials can be achieved through brittle fracture of the Si and SiC phases, overcoming the bottleneck problem of achieving uniform material removal during the micromachining of RB-SiC composite materials. However, the nucleation and propagation of microcracks during the brittle erosion removal of RB-SiC composite materials are uncontrollable factors. Therefore, research on the theory and methods of high-quality micro-abrasive jet machining of RB-SiC is urgent, forward-looking, and innovative.

[0005] Patent (ZL202310026757.7) discloses an ultrasonic cavitation-assisted abrasive jet processing system and method; patent (ZL201911425998.9) discloses a split-phase control cavitation enhanced abrasive microjet polishing system; patent (ZL202010119034.8) discloses an immersion-type gas jet driven polishing device and polishing method; and patent (ZL202210604223.3) discloses an ultrasonic cavitation-assisted submerged pulsating gas jet polishing system. Although the above can improve the quality of jet processing to some extent, they are mostly used in the polishing field and are difficult to achieve efficient and high-quality micro-processing of RB-SiC ceramic material microstructures.

[0006] Patents (2017109524307), (2018100144364), (2023106746325), and (2023105031109) disclose an abrasive jet processing technology based on throttling expansion negative pressure drive. However, the abrasives used are all abrasive particles with a single particle size range, which cannot achieve effective mixing of abrasives with multiple particle size ranges, making it difficult to meet the needs of preparing microstructures on the surface of the sealing pair of the multiphase hard and brittle material RB-SiC. Patent (ZL202311399390.X) discloses an immersion microjet processing system and method for RB-SiC ceramic microstructure mixed abrasive synergistic enhancement, which finds that the processing efficiency and forming accuracy of RB-SiC microstructures are effectively improved through the synergistic erosion effect of abrasives with different particle sizes. However, the residue of mixed-size abrasives in the immersion processing environment will cause changes in the rheological properties of the slurry and the turbulent state of the jet flow field, which will greatly increase the difficulty of material removal function stability and surface processing quality control, thus limiting its widespread application. Summary of the Invention

[0007] To address the aforementioned technical bottlenecks, this invention provides a method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorption multiphase jet, thereby solving the problems encountered in the preparation process of microstructured surface RB-SiC friction pairs.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorbing multiphase jets, characterized in that the method is implemented based on a processing system, which mainly includes:

[0010] The jet generating unit includes an air compressor, dryer, pressure regulating valve, micron diamond particle feeder, slurry tank, magnetic stirrer, and jet nozzle assembly.

[0011] Motion control unit: including the milling machine's X-axis, Y-axis, and Z-axis, as well as the jet angle adjustment device;

[0012] Workpiece clamping unit: includes machining chamber, workpiece clamping platform, platform shaft, magnetic coupling I and magnetic coupling II;

[0013] The jet nozzle assembly includes a jet nozzle, a replaceable Laval nozzle, and a nozzle connector. The replaceable Laval nozzle is installed inside the inner hole of the jet nozzle. The nozzle connector is threaded to the jet nozzle to fix the replaceable Laval nozzle. The gas-solid input end of the nozzle connector is securely connected to the gas-solid delivery pipe, and the slurry suction end of the jet nozzle is securely connected to the slurry pipe. The jet nozzle assembly is fixed to the end face of the jet angle adjustment device by a jet nozzle assembly clamp.

[0014] The workpiece clamping assembly includes a machining chamber, a workpiece clamping platform, a platform shaft, magnetic coupling I, and magnetic coupling II. Magnetic coupling I is connected to the workpiece clamping platform via the platform shaft, and the workpiece mask assembly is fixed to the workpiece clamping platform. Magnetic coupling II is installed at the bottom of the machining chamber and drives magnetic coupling I through magnetic force, thereby enabling the workpiece clamping platform to rotate.

[0015] The preparation method includes the following steps:

[0016] S1. Clamping and preparation: Select the appropriate workpiece mask assembly according to the shape of the microstructure to be prepared and fix it on the workpiece clamping platform; pour the nano-diamond slurry into the slurry tank and start the magnetic stirrer; position the jet nozzle to the processing start position by adjusting each motion axis and angle adjustment device.

[0017] S2. Jet Generation and Processing: The air compressor, dryer, and micron diamond particle feeder are started sequentially, and the working pressure is adjusted by the pressure regulating valve. When the high-speed micron diamond gas jet flows through the Laval nozzle, it generates a throttling expansion effect, forming a negative pressure and automatically drawing in the nano-diamond slurry to form a gas-solid-liquid multiphase jet. At the same time, the rotational motion of the motion unit and the workpiece clamping platform is controlled by the CNC system to generate a predetermined progressive processing trajectory.

[0018] S3. End and Post-processing: After the processing trajectory is completed, turn off the powder feeder, air compressor and dryer in sequence, return the motion axis to zero, take out the processed workpiece mask assembly and clean it to obtain the required microstructure surface RB-SiC friction pair.

[0019] Preferably, the solid abrasive in the multiphase jet is a "cellular" diamond cluster abrasive with mixed particle size characteristics. Its formation mechanism lies in utilizing the shear-thinning properties of the nanodiamond slurry. At high shear rates, the slurry viscosity decreases, and its fluidity increases, effectively dispersing and encapsulating micron-sized diamond particles. In the impact zone at low shear rates, the slurry viscosity recovers, allowing the abrasive to form a stable cluster structure. By adjusting the mass flow rate of the micron-sized diamond particles, the content of micron-sized particles in this cluster abrasive can be controlled.

[0020] Preferably, the replaceable Laval nozzle in the jet nozzle assembly is a detachable structure, facilitating replacement after wear to maintain a stable throttling effect. By changing the geometric parameters of this nozzle, the intake volume of the nanodiamond slurry can be adjusted, thereby controlling the composition of the multiphase jet.

[0021] Preferably, the workpiece mask assembly includes a type I mask and a type II mask. The surface of the type I mask has 20 sinusoidal contour grooves evenly distributed. The surface of the type II mask has contour grooves of four shapes—circular, hexagonal, crescent-shaped, and scimitar-shaped—distributed sequentially from the inside out, with 20 grooves of each shape evenly distributed.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By using a throttling expansion self-absorption design, micron-sized diamond gas jets are mixed online with nano-diamond slurry with shear-thinning properties to form stable "cellular" multi-scale abrasive clusters, solving the problems of poor uniformity and insufficient stability of single-particle-size abrasives or premixed abrasives when processing multiphase materials. 2. During the processing, the "cellular" abrasive clusters deagglomerate when impacting the workpiece surface. Micron-sized diamonds mainly achieve brittle erosion and uniform material removal, while nano-diamonds achieve flexible finishing of the processed surface through tilling and micro-cutting action, which can effectively suppress the generation of micro-cracks and improve the quality of the processed surface. 3. The use of replaceable and parameterizable Laval nozzles facilitates maintenance and allows for flexible control of jet performance, improving process adaptability and economy. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below;

[0024] Figure 1 This is a schematic diagram of the overall structure of the apparatus used in the preparation method of microstructured surface RB-SiC friction pairs based on throttling expansion self-absorption multiphase jet;

[0025] Figure 2 This is a schematic diagram of the jet nozzle assembly used in the method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorbing multiphase jet;

[0026] Figure 3 This is a schematic diagram of the workpiece clamping assembly used in the method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorbing multiphase jet;

[0027] Figure 4 This is a schematic diagram of the structure of the type I mask used in the method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorption multiphase jet;

[0028] Figure 5 This is a schematic diagram of the structure of the type I mask used in the method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorption multiphase jet;

[0029] In the diagram: 1-Milling machine Z-axis, 2-Milling machine Z-axis clamping table, 3-Cross slide, 4-Jet angle adjustment device, 5-Jet nozzle assembly, 6-Jet nozzle assembly fixture, 7-Milling machine Y-axis, 8- 9-Workpiece mask assembly, 10-Workpiece clamping assembly, 11-Milling machine X-axis, 12-Slurry pipe, 13-Slurry tank, 14-Material cart, 15-Nano diamond slurry, 16-Magnetic stirrer, 17-Pressure regulating valve, 18-Air compressor, 19-Dryer, 20-Micron diamond particle feeder, 21-Gas-solid conveying pipe, 501-Jet nozzle, 502-Slurry suction end, 503-Replaceable Laval nozzle, 504-Thread, 505-Nozzle connector, 506-Gas-solid input end, 901-Machining chamber, 902-Workpiece clamping platform, 903-Platform shaft, 904-Magnetic coupling I, 905-Magnetic coupling II, 801-Type I mask, 802-Type II mask. Detailed Implementation

[0030] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0031] Example: Using Figure 1 The apparatus shown is used to prepare the microstructure on the surface of the RB-SiC friction pair.

[0032] First, perform step S1: Select type II mask 802 as the workpiece mask assembly 8 and fix it on the workpiece clamping platform 902. Pour the prepared nano-diamond slurry 14 into the slurry tank 12 and start the magnetic stirrer 15 to disperse it evenly. Adjust the milling machine's X-axis 10, Y-axis 7, Z-axis 1 and jet angle adjustment device 4 to align the jet nozzle assembly 5 with the machining starting point.

[0033] Next, step S2 is executed: the machining trajectory code is input through the CNC system to control the translation of the X-axis 10 and Y-axis 7 and the rotation of the workpiece clamping platform 902 driven by the magnetic coupling II 905. The air compressor 17, dryer 18, and micron-sized diamond particle feeder 19 are started sequentially. The pressure regulating valve 16 is adjusted to the predetermined working pressure (e.g., 0.3 MPa). At this time, the micron-sized diamond particles are mixed with the gas and transported to the jet nozzle assembly 5 through the gas-solid delivery pipe 20. Throttling expansion occurs when flowing through the replaceable Laval nozzle 503, forming a negative pressure at the slurry suction end 502, drawing in the nano-diamond slurry 14, and finally forming a gas-solid-liquid multiphase jet to process the workpiece.

[0034] Finally, execute step S3: After the processing trajectory has finished running, turn off the micron-sized diamond particle feeder 19, air compressor 17, and dryer 18 in sequence. Reset each motion axis to its origin, remove the workpiece mask assembly 8, and perform ultrasonic cleaning with anhydrous ethanol to obtain the RB-SiC friction pair surface with a specific microstructure.

[0035] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention. Meanwhile, although this paper extensively uses the following components: milling machine Z-axis 1, milling machine Z-axis clamping table 2, cross slide 3, jet angle adjustment device 4, jet nozzle assembly 5, jet nozzle assembly fixture 6, milling machine Y-axis 7, workpiece mask assembly 8, workpiece clamping assembly 9, milling machine X-axis 10, slurry pipe 11, slurry tank 12, material cart 13, nano-diamond slurry 14, magnetic stirrer 15, pressure regulating valve 16, air compressor 17, dryer 18, micron diamond particle feeder 19, gas-solid conveying pipe 20, jet nozzle 501, slurry suction end 502, replaceable Laval nozzle 503, thread 504, nozzle connector 505, gas-solid input end 506, machining chamber 901, workpiece clamping platform 902, platform shaft 903, magnetic coupling I 904, magnetic coupling II The terms 905, Type I mask 801, Type II mask 802, etc., are used, but the possibility of using other terms is not excluded. These terms are used merely for the convenience of describing and explaining the essence of the invention; interpreting them as any additional limitation would contradict the spirit of the invention.

[0036] This embodiment is just one example of the present invention, and any technical solution that adopts a similar structure is within the protection scope of the present invention.

[0037] The parts not covered in this invention are the same as or can be implemented using existing technologies.

Claims

1. A method for preparing microstructured surface RB-SiC friction pairs based on throttling expansion self-absorbing multiphase jet, characterized in that, Includes the following steps: S1: Fix the workpiece mask assembly (8) on the workpiece clamping platform (902), pour the nano-diamond slurry (14) into the slurry tank (12), and start the magnetic stirrer (15); by adjusting the milling machine X-axis (10), milling machine Y-axis (7), milling machine Z-axis (1) and jet angle adjustment device (4), position the jet nozzle assembly (5) to the required processing position; S2: Control the movement of the milling machine X-axis (10), milling machine Y-axis (7) and magnetic coupling II (905) through CNC instruction code to generate a progressive machining trajectory based on throttling expansion self-priming multiphase jet; start the air compressor (17) and dryer (18) in sequence, adjust the airflow pressure through the pressure regulating valve (16), and turn on the micron diamond particle feeder (19); S3: After the trajectory control system finishes running, turn off the micron diamond particle feeder (19), air compressor (17) and dryer (18) in sequence, reset the milling machine X-axis (10) and milling machine Y-axis (7) to the machine origin, take out the workpiece mask assembly (8) and clean it to complete the preparation of the microstructure surface RB-SiC friction pair; The method uses the following equipment components: milling machine Z-axis (1), milling machine Z-axis clamping table (2), cross slide (3), jet angle adjustment device (4), jet nozzle assembly (5), jet nozzle assembly fixture (6), milling machine Y-axis (7), milling machine X-axis (10), slurry pipe (11), material cart (13), magnetic stirrer (15), pressure regulating valve (16), air compressor (17), dryer (18), micron diamond particle feeder (19), gas-solid conveying pipe (20), and workpiece clamping assembly (9); The jet nozzle assembly (5) includes a jet nozzle (501), a replaceable Laval nozzle (503), and a nozzle connector (505). The replaceable Laval nozzle (503) is installed in the inner hole of the jet nozzle (501). The nozzle connector (505) is connected to the jet nozzle (501) by a thread (504) to fix the replaceable Laval nozzle (503). The gas-solid input end (506) of the nozzle connector (505) is connected to the gas-solid delivery pipe (20). The slurry suction end (502) of the jet nozzle (501) is connected to the slurry pipe (11). The jet nozzle assembly (5) is fixed to the end face of the jet angle adjustment device (4) by a jet nozzle assembly clamp (6). The workpiece clamping assembly (9) includes a processing chamber (901), a workpiece clamping platform (902), a platform shaft (903), a magnetic coupling I (904), and a magnetic coupling II (905). The workpiece clamping platform (902) is connected to the magnetic coupling I (904) through the platform shaft (903). The workpiece mask assembly (8) is fixed on the workpiece clamping platform (902). The magnetic coupling II (905) is installed at the bottom of the processing chamber (901) and drives the magnetic coupling I (904) to rotate the workpiece clamping platform (902) through magnetic force.

2. The preparation method according to claim 1, characterized in that, The multiphase jet is a gas-solid-liquid dispersion jet, wherein the solid abrasive dispersion is a "cellular" diamond cluster abrasive with mixed particle size characteristics; and the content of micron diamond particles in the "cellular" diamond cluster abrasive is controlled by adjusting the mass flow rate of micron diamond particles in the micron diamond particle feeder (19).

3. The preparation method according to claim 1, characterized in that, The replaceable Laval nozzle (503) in the jet nozzle assembly (5) is a detachable structure. When the inner wall wear affects the throttling effect, it can be replaced with a new nozzle. The replaceable Laval nozzle (503) and the jet nozzle (501) constitute a self-priming multiphase jet injection system. Furthermore, the intake amount of nanodiamond slurry (14) can be adjusted by changing the geometric parameters of the replaceable Laval nozzle (503).

4. The preparation method according to claim 1, characterized in that, The multiphase jet contains a liquid dispersion with shear-thinning properties.

5. The preparation method according to claim 1, characterized in that, The workpiece mask assembly (8) includes a type I mask (801) and a type II mask (802). The type I mask (801) has 20 sinusoidal contour grooves evenly distributed on its surface, and the type II mask (802) has four shapes of contour grooves distributed on its surface, which are circular, hexagonal, crescent-shaped and scimitar-shaped from the inside out, and 20 of each shape are evenly distributed.

6. The preparation method according to claim 1, characterized in that, Step S1 further includes: selecting and installing the workpiece mask assembly (8) according to the preparation requirements of the microstructure surface RB-SiC friction pair.

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