CN113231898B - Ultrasonic vibration auxiliary processing method for difficult-to-process SiCf/SiC ceramic matrix composite - Google Patents

Abstract

The invention discloses an ultrasonic vibration-assisted processing method for difficult-to-machine SiC _f /SiC ceramic matrix composite materials. Firstly, the difficult-to-machine SiC _f /SiC ceramic matrix composite materials are cut into samples, and clamped on a three-coordinate axis numerical control milling machine; Then connect the ultrasonic vibration equipment with the three-axis CNC milling machine and set the initial ultrasonic vibration parameters; then use the self-designed PDC tool to perform ultrasonic vibration-assisted cutting, down milling and milling processing on the sample; finally use the tool scanner to measure The amount of tooth wear on the end face of the PDC layer. When the tapered teeth on the end face of the PDC layer are completely worn, it is judged that the PDC tool is worn out and the tool is no longer used for processing, and the volume of material removed by the PDC tool is recorded. The method of the invention achieves the purpose of reducing tool wear, improving tool life and greatly reducing cost.

Description

Ultrasonic vibration-assisted machining method for difficult-to-machine SiCf/SiC ceramic matrix composites

technical field

The invention belongs to the technical field of material processing, and in particular relates to an ultrasonic vibration-assisted processing method for composite materials.

Background technique

SiC _f /SiC ceramic matrix composite material is a SiC fiber reinforced SiC ceramic matrix composite material researched and developed in recent years, which retains the characteristics of SiC ceramic materials such as high temperature resistance, oxidation resistance, wear resistance, and corrosion resistance. With the presence of fiber-reinforced phase, the toughness of the material is enhanced, and the impact load resistance performance is significantly improved. SiC _f /SiC ceramic matrix composites can work at a temperature above 1200°C without using air cooling and thermal barrier coatings, and their density is 1/3 of that of superalloys. They are used in aerospace, automobile manufacturing, and transportation and other industries have shown very attractive application prospects.

However, due to the high hardness of SiC material, its hardness is even much higher than that of most commonly used cutting tool materials. At the same time, the material is brittle, has low fracture toughness, and strong wear resistance, which makes SiC _f /SiC ceramic matrix composites in machining. Faced with a series of problems, such as: severe tool wear, high cutting force, and even difficult cutting materials; poor machined surface quality, there are processing quality defects such as delamination, tearing, and chipping, which are typical hard and brittle difficult-to-machine materials. In order to improve the cutting performance of SiC _f /SiC ceramic matrix composites and reduce cutting force and tool wear, ultrasonic vibration assisted machining technology has been widely used in the cutting of SiC _f /SiC ceramic matrix composites. However, the selection and matching of tools still remain It is one of the difficult problems in the processing of SiC _f /SiC ceramic matrix composites.

Chi Xian and other researchers published the paper "Research on Surface Morphology of SiC _f /SiC Ceramic Matrix Composites by Ultrasonic Vibration High-speed Milling Hole Making" in the Proceedings of the 21st National Conference on Composite Materials (NCCM-21), 2020: 7 In the process of ultrasonic vibration-assisted drilling of SiC _f /SiC ceramic matrix composites, the cutting performance of cemented carbide tools, diamond-coated tools, electroplated superabrasive tools, brazed diamond tools, and PCD tools was compared, and it was found that Cemented carbide tools cannot be used for cutting SiC _f /SiC ceramic matrix composites, and PCD tools should be preferred for machining SiC _f /SiC ceramic matrix composites. Chen Yurong and other researchers published the paper "Experimental Research on Ultrasonic Vibration Assisted Dry Drilling of SiC _f /SiC Ceramic Matrix Composites" in Aeronautical Manufacturing Technology, 61 (2018) 47-51, in order to overcome the serious problem of tool wear under dry cutting , the drilling process of SiC _f /SiC ceramic matrix composites was carried out by orderly arranged brazed diamond bushing drills. In addition, Jiang Wenzhuang used PCD milling cutters and electroplated diamond grinding heads to perform ultrasonic vibration-assisted processing on SiC _f /SiC composite materials in his master's thesis "Study on the Processing Technology of SiC _f /SiC Composite Material Slender and Thin-walled Pipe Fittings", and found that PCD tools have wear such as chipping and tool fracture, and are not suitable for cutting SiC _f /SiC composite materials. Electroplated diamond grinding heads should be used. In the above-mentioned documents, when SiC _f /SiC ceramic matrix composites are processed by ultrasonic vibration assisted cutting, there are problems such as severe tool wear and poor processing quality. The selection and matching of tools limit the industrial application of SiC _f /SiC ceramic matrix composites. Rapid promotion and engineering application.

Polycrystalline diamond composite (PDC) cutting tools are made by sintering diamond micropowder and cemented carbide substrate under ultra-high pressure and high temperature conditions. The diamond content in the composite sheet is as high as 99%, and the diamond layer has extremely high hardness and excellent wear resistance. , and the thickness is thin, generally controlled at about 0.5-1 mm, the cutting edge of the tool is always self-sharpening, while maintaining the high hardness, high wear resistance and thermal conductivity of diamond, it also has the strength and impact resistance of cemented carbide Toughness is one of the ideal tools for processing hard and brittle difficult-to-machine materials. However, at present, tools such as electroplated diamond grinding heads and brazed diamond grinding heads are commonly used in the process of ultrasonic vibration-assisted machining of SiC _f /SiC ceramic matrix composites. , The tool is prone to wear such as abrasive damage, shedding, chipping, etc., which makes the tool wear invalid and greatly reduces the service life of the tool. At the same time, PDC tools with better bonding performance and higher hardness have not been engineeringly applied in ultrasonic vibration-assisted processing of SiC _f /SiC ceramic matrix composites, and there are no relevant reports and standards for the structure and design of PDC tools.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a ultrasonic vibration-assisted processing method for difficult-to-machine SiC _f /SiC ceramic matrix composites. First, the difficult-to-machine SiC _f /SiC ceramic matrix composites are cut into samples, and clamped On the three-axis CNC milling machine; then connect the ultrasonic vibration equipment with the three-coordinate axis CNC milling machine and set the initial ultrasonic vibration parameters; then use the self-designed PDC tool to perform ultrasonic vibration-assisted cutting, down milling and milling on the sample Processing; finally, use a tool scanner to measure the wear amount of the end face of the PDC layer. When the tapered teeth on the end face of the PDC layer are completely worn, it is determined that the PDC tool is worn out, and the tool is no longer used for processing, and the volume of material removed by the PDC tool is recorded. The method of the invention achieves the purpose of reducing tool wear, improving tool life and greatly reducing cost.

The technical solution adopted by the present invention to solve its technical problems comprises the steps:

Step 1: Cut the difficult-to-machine SiC _f /SiC ceramic matrix composite material into a sample of a given size, and clamp it on a three-axis CNC milling machine;

Step 2: Connect the ultrasonic vibration equipment with the three-axis CNC milling machine and set the initial ultrasonic vibration parameters of the ultrasonic vibration equipment;

Step 3: Use the self-designed PDC tool to perform ultrasonic vibration-assisted cutting on the sample;

The self-designed PDC cutter includes a tip and a main body;

The top is a PDC layer; the end face of the PDC layer is composed of a plurality of uniformly arranged tapered teeth;

The main body is hard alloy, which is divided into two sections. The main body near the top is the front section, which has not been polished; the main body far away from the top is the rear section, which is polished to facilitate clamping;

The top and the main body are crimped together by high temperature and high pressure process; the top and the main body are hollow cylinders, which are convenient for chip removal;

Step 4: Use the laser displacement amplitude meter to measure the actual amplitude of the tool and feed back the current parameters of the ultrasonic vibration equipment, then adjust the vibration parameters of the ultrasonic vibration equipment and measure until the ultrasonic vibration frequency and ultrasonic amplitude matching the tool are obtained;

Step 5: Use the self-designed PDC tool to perform ultrasonic vibration-assisted down milling on the sample, and the processing method is dry milling without adding coolant;

Step 6: Set the milling parameters, and use the self-designed PDC tool to perform ultrasonic vibration-assisted milling on the sample;

Step 7: Use a tool scanner to measure the wear of the cutter teeth on the end face of the PDC layer;

Step 8: When the conical cutter teeth on the end face of the PDC layer are completely worn out, it is determined that the PDC tool is worn out, and the tool is no longer used for processing, and the volume of material removed by the PDC tool is recorded.

Preferably, the method for cutting the difficult-to-machine SiC _f /SiC ceramic matrix composite in step 1 is high-pressure water cutting.

Preferably, the size of the sample is 80×45×3.8mm.

Preferably, the initial ultrasonic vibration parameters are: a vibration frequency of 27-29 kHz, and an ultrasonic amplitude of 2-8 μm; a vibration frequency matching the cutter is 28.3 kHz, and an amplitude of 6 μm.

Preferably, the conical shape of the conical cutter teeth is a regular pyramid, the side length of the bottom surface of the conical cutter teeth is 0.23mm, and the height of the conical cutter teeth is 0.3mm.

Preferably, the cemented carbide is K20 cemented carbide.

Preferably, the length l of the PDC cutter is 55 mm, the thickness of the PDC layer is 1.0 mm; the outer diameter D of the hollow cylinder is 6 mm, and the inner diameter d is 3 mm.

Preferably, the model of the three-axis CNC milling machine is CY-VMC850; the model of the laser displacement amplitude meter is LK-H020.

Preferably, the milling parameters are as follows: the spindle speed of the three-axis CNC milling machine is 2500-7000r/min, the feed rate is 200-500mm/min, the cutting depth is 0.05-0.20mm, and the cutting width is 5mm; after testing The optimal milling and grinding parameters obtained afterward are: the spindle speed is 5500r/min, the feed rate is 300mm/min, the cutting depth is 0.15mm, and the cutting width is 5mm.

The beneficial effects of the present invention are as follows:

1. The method of the present invention selects a self-designed PDC cutter, and by selecting reasonable ultrasonic vibration-assisted processing parameters, the purpose of reducing tool wear and improving tool life is achieved in the ultrasonic-vibration-assisted processing of difficult-to-machine SiC _f /SiC ceramic matrix composite materials .

2. Using the processing method of the present invention, compared with the commonly used 100-mesh electroplated diamond grinding head, 50-mesh and 200-mesh brazed diamond grinding head for processing ceramic matrix composite materials, under the same processing conditions, SiC _f /SiC ceramic matrix composite The service life of the PDC tool in ultrasonic vibration assisted machining of materials is 50, 4, and 12 times that of the above three types of tools, respectively, and the tool life has been significantly improved.

3. Since the thickness of the PDC thin layer is 1.0mm and the height of the cutter tooth is 0.3mm, after the tool wears out and fails, the cutter can be repaired and processed again to meet the requirements of the cutter to continue cutting, which greatly reduces the cost.

Description of drawings

Figure 1 is a schematic diagram of the structure of a PDC cutter.

Fig. 2 is a schematic diagram of the structure of the PDC end face cutter.

Fig. 3 is a schematic diagram of the PDC tool wear failure judgment standard.

Figure 4 is a diagram of comparative tool 1: 100-mesh electroplated diamond grinding head, in which (a) a new tool before wear, (b) tool wear and failure.

Figure 5 is a diagram of the second comparison tool: 50 mesh brazed diamond grinding head, in which (a) the new tool before wear, (b) the tool wears out and fails.

Fig. 6 is a diagram of the third comparative tool: 200 mesh brazed diamond grinding head, in which (a) new tool before wear, (b) tool wear and failure.

In the figure: 1-top, 2-main body, 3-anterior segment, 4-posterior segment.

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

In order to select and match suitable machining tools in ultrasonic vibration assisted cutting of SiC _f /SiC ceramic matrix composites, reduce tool wear and prolong tool life, the present invention proposes ultrasonic vibration assisted machining of difficult-to-machine SiC _f /SiC ceramic matrix composites. Machining methods are used to realize the cutting of hard and brittle SiC _f /SiC ceramic matrix composites, and the cutting tools suitable for this type of composite materials are designed.

The ultrasonic vibration-assisted processing method for difficult-to-machine SiC _f /SiC ceramic matrix composites proposed in this example is suitable for ultrasonic vibration-assisted processing of SiC fiber-reinforced SiC ceramic matrix composites. The following only uses SiC _f /SiC ceramic matrix composites for illustration.

An ultrasonic vibration-assisted processing method for difficult-to-machine _SiCf /SiC ceramic matrix composite materials, comprising the following steps:

Step 1: Prepare the processing sample, use high-pressure water cutting to cut the difficult-to-machine SiC _f /SiC ceramic matrix composite material into a processing sample of 80×45×3.8mm, then clean the water stains on the sample, and wait for the sample After drying, it was clamped on a CY-VMC850 three-axis CNC milling machine.

Step 2: Connect the ultrasonic vibration equipment with the three-axis CNC milling machine and set the initial ultrasonic vibration parameters of the ultrasonic vibration equipment; the initial ultrasonic vibration parameters are: vibration frequency 27-29 kHz, ultrasonic amplitude 2-8 μm.

Step 3: Select the self-designed PDC tool and clamp it on the CY-VMC850 three-axis CNC milling machine, so that the tool overhang (tool exposed length) is 40mm. The geometric parameters of the selected PDC cutter are: the blade body is divided into two parts, as shown in Figure 1, the top of which is a 1.0 mm thick PDC thin layer, and a regular pyramidal geometric structure as shown in Figure 2 is processed on the end face of the PDC thin layer ; followed by the 54 mm long K20 series hard alloy main cutter body section, the front section is not polished and appears gray black, the rear section is polished to facilitate the clamping of the handle lock, the color is bright, and the ultrasonic energy is transmitted through the K20 hard alloy material Medium loss is low. During the tool manufacturing process, the PDC thin layer is tightly extruded and bonded to the end face of the K20 tool body through a high temperature and high pressure process. The whole tool is designed as a hollow structure in order to prevent chip blockage from affecting processing. The outer diameter of the tool is D=6mm, the inner diameter is d=3mm, and the total length of the tool is l=55mm.

Step 4: Use the LK-H020 laser displacement amplitude meter to measure the actual amplitude of the tool and feed back the current parameters of the ultrasonic vibration equipment, then adjust the ultrasonic energy output of the ultrasonic vibration equipment, the strength of the current, etc. to change the vibration parameters and measure until the corresponding tool is obtained. Matching ultrasonic vibration frequency and ultrasonic amplitude, the ultrasonic frequency is 28.3kHz, and the amplitude is 6μm;

Step 5: Use the self-designed PDC tool to perform ultrasonic vibration-assisted down milling on the sample, and the processing method is dry milling without adding coolant;

Step 6: Set milling and grinding processing parameters, and perform ultrasonic vibration-assisted milling and grinding processing on the clamped and difficult-to-machine SiC _f /SiC ceramic matrix composite material sample. Processing parameters: spindle speed is 2500-7000r/min, feed speed It is 200-500mm/min, the cutting depth is 0.05-0.20mm, and the cutting width is 5mm. Under the above range of cutting parameters, a single factor test and an orthogonal test with 4 factors and 4 levels were carried out on ultrasonic vibration assisted milling and grinding. According to the test results, the parameters suitable for ultrasonic vibration-assisted milling and grinding in this embodiment are analyzed and screened: the spindle speed is 5500r/min, the feed rate is 300mm/min, the cutting depth is 0.15mm, and the cutting width is 5mm.

Step 7: Use a tool scanner to measure the wear of the cutter teeth on the end face of the PDC layer;

Step 8: When the tapered cutter teeth on the end face of the PDC layer are completely worn and the end face of the PDC thin layer is exposed as shown in Figure 3, it is judged that the PDC tool is worn out, and the tool is no longer used for processing, and the volume of material removed by the PDC tool is recorded.

In this example, the difficult-to-machine SiC _f /SiC ceramic matrix composite material wears out after the PDC tool removes a material volume of 9720 mm ³ during the ultrasonic vibration-assisted machining.

Comparative tool 1: The technical measures are the same as those of the above-mentioned embodiment, only in "Step 3: Selecting a processing tool", a 100-mesh electroplated diamond grinding head is selected for ultrasonic vibration-assisted processing. It was found that when the tool of the electroplated diamond grinding head was completely worn out, as shown in Fig. 4, the volume of material removed by the tool was 192 mm ³ , which was 1/50 of the tool life of this embodiment.

Comparative tool 2: The technical measures are the same as those of the above-mentioned embodiment, only in "Step 3: Selecting the processing tool", a 50-mesh brazed diamond grinding head is selected for ultrasonic vibration-assisted processing. It was found that when the brazed diamond grinding head tool was completely worn out, as shown in Figure 5, the volume of material removed by the tool was 2362.5 mm ³ , which was 1/4 of the tool life of this example.

Comparative tool 3: The technical measures are the same as the above-mentioned embodiment, only in "Step 3: Selecting a processing tool", a 200-mesh brazed diamond grinding head is selected for ultrasonic vibration-assisted processing. It was found that when the brazed diamond grinding head tool was completely worn out, as shown in Figure 6, the volume of material removed by the tool was 810 mm ³ , which was 1/12 of the tool life of this example.

From the above data, it can be seen that the tool life of this embodiment is 50, 12, and 4 times that of the 100-mesh electroplated diamond grinding head, 200-mesh and 50-mesh brazed diamond grinding head tools commonly used in processing ceramic matrix composites, and the reduction has been achieved. Tool wear, the goal of increasing tool life.

Claims (5)

1. A difficult-to-machine SiC _f /SiC ceramic matrix composite material ultrasonic vibration-assisted processing method, is characterized in that, comprises the following steps: Step 1: Cut the difficult-to-machine SiC _f /SiC ceramic matrix composite material into a sample of a given size, and clamp it on a three-axis CNC milling machine; Step 2: Connect the ultrasonic vibration equipment with the three-axis CNC milling machine and set the initial ultrasonic vibration parameters of the ultrasonic vibration equipment; The initial ultrasonic vibration parameters are: the vibration frequency is 27-29 kHz, the ultrasonic amplitude is 2-8 μm; the vibration frequency matched with the tool is 28.3 kHz, and the amplitude is 6 μm; Step 3: Use the self-designed PDC tool to perform ultrasonic vibration-assisted cutting on the sample; The self-designed PDC cutter includes a tip and a main body; The top is a PDC layer; the end face of the PDC layer is composed of a plurality of uniformly arranged conical cutter teeth; the conical shape of the conical cutter teeth is a regular quadrangular pyramid, and the side length of the bottom surface of the conical cutter teeth is 0.23mm. The height of the conical cutter tooth is 0.3mm; The main body is hard alloy, which is divided into two sections. The main body near the top is the front section, which has not been polished; the main body far away from the top is the rear section, which is polished to facilitate clamping; The top and the main body are crimped together by high temperature and high pressure process; the top and the main body are hollow cylinders, which are convenient for chip removal; The length of the PDC cutter is l=55mm, and the thickness of the PDC layer is 1.0mm; the outer diameter of the hollow cylinder is D=6mm, and the inner diameter is d=3mm; Step 4: Use the laser displacement amplitude meter to measure the actual amplitude of the tool and feed back the current parameters of the ultrasonic vibration equipment, then adjust the vibration parameters of the ultrasonic vibration equipment and measure until the ultrasonic vibration frequency and ultrasonic amplitude matching the tool are obtained; Step 5: Use the self-designed PDC tool to perform ultrasonic vibration-assisted down milling on the sample, and the processing method is dry milling without adding coolant; Step 6: Set the milling parameters, and use the self-designed PDC tool to perform ultrasonic vibration-assisted milling on the sample; The milling and grinding parameters are as follows: the spindle speed of the three-axis CNC milling machine is 2500-7000r/min, the feed rate is 200-500mm/min, the cutting depth is 0.05-0.20mm, and the cutting width is 5mm; obtained after testing The optimal milling parameters are: the spindle speed is 5500r/min, the feed rate is 300mm/min, the cutting depth is 0.15mm, and the cutting width is 5mm; Step 7: Use a tool scanner to measure the wear of the cutter teeth on the end face of the PDC layer; Step 8: When the conical cutter teeth on the end face of the PDC layer are completely worn out, it is determined that the PDC tool is worn out, and the tool is no longer used for processing, and the volume of material removed by the PDC tool is recorded. 2. A kind of difficult-to-machine _SiCf /SiC ceramic matrix composite material ultrasonic vibration assisted processing method according to claim 1, it is characterized in that, the method for cutting difficult-to-machine _SiCf /SiC ceramic matrix composite material in the step 1 is High pressure water cutting. 3 . The ultrasonic vibration-assisted machining method for difficult-to-machine SiC _f /SiC ceramic matrix composites according to claim 1 , wherein the size of the sample is 80×45×3.8 mm. 4 . The ultrasonic vibration-assisted machining method for difficult-to-machine SiC _f /SiC ceramic matrix composites according to claim 1 , wherein the cemented carbide is K20 cemented carbide. 5. A kind of difficult-to-machine SiC _f /SiC ceramic matrix composite material ultrasonic vibration assisted processing method according to claim 1, it is characterized in that, the model of described three-axis numerical control milling machine is CY-VMC850; The laser displacement amplitude meter The model is LK-H020.

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