Method for preparing TiAl / TiAlN / TiAlB / TiAlBN composite coating on surface of small milling cutter through direct current cathode arc

Abstract

A method for preparing a TiAl / TiAlN / TiAlB / YiAlBN composite coating on the surface of a small milling cutter through direct current cathode arc comprises the steps that the milling cutter is pretreated, a thin film is deposited, a circuit board is cut and tested, and ultrasonic cleaning is conducted on the milling cutter through absolute ethyl alcohol and deionized water, so that no impurity adheres to the surface of the milling cutter, and follow-up deposition is easy; vactime DLC type thin film deposition equipment is used for conducting four times of different coating deposition on the milling cutter in sequence, and a TiAl / TiAlN / TiAlB / TiAlBN composite coating is obtained; a circuit board cutting test is carried out by using the milling cutter deposited with the coating, and high bonding strength and wear resistance between the composite coating deposited by the method and a substrate are confirmed.

Description

Technical Field

[0001] The present invention relates to vacuum coating technology and the application field of cutting tool coatings, and specifically to a method for preparing a TiAl / TiAlN / TiAlB / TiAlBN composite coating on a milling cutter using a DC cathode arc. Background Art

[0002] With the rapid development of 5G communications, wearable devices, and microsensors, printed circuit boards (PCBs) are evolving toward high-density interconnection, ultra-thinness, and heterogeneous multilayer fabrication. These circuit boards require the processing of microvias and fine lines, placing stringent demands on the dynamic stability and cutting edge accuracy of small and micro milling cutters. For example, the microgrooves of embedded capacitors and inductors in 5G communication modules require a machining depth deviation of ±5μm, while the polyimide substrate of flexible printed circuit boards (FPCs) is susceptible to thermal damage due to its low thermal conductivity. Small milling cutters with a diameter of approximately 2mm, due to their moderate stiffness and flexibility, have become core tools for such applications. According to statistics from 2024, 2mm-class milling cutters accounted for 32% of the global PCB micromachining market. Their cutting stability is particularly superior to that of micro milling cutters (diameter <0.5mm) in the processing of blind grooves in multilayer boards. Research has shown that small milling cutters with TiAlN coatings have a lifespan three times longer than uncoated tools when machining glass fiber-reinforced epoxy resin boards. However, they still face problems such as copper sticking to the cutting edge and oxidation failure under complex working conditions.

[0003] The mainstream coating technologies for micro and small milling cutters are still dominated by single-layer TiAlN, TiAlSiN, and multi-layer TiN / TiAlN, but their performance faces significant bottlenecks. While TiAIN coatings offer high hardness, their columnar crystal structure is susceptible to oxidation failure at high temperatures, leading to adhesion of copper chips and resin pyrolysis products to the cutting edge, accelerating wear. TiAlSiN coatings refine the grain size through Si doping, but high Si content reduces coating toughness and increases the risk of brittle fracture. Multi-layer TiN / TiAlN coatings disperse stress through an alternating soft and hard structure, but sudden changes in interlayer composition can easily lead to interfacial stress concentration, significantly increasing the risk of interlayer delamination at the spiral cutting edge of the milling cutter.

[0004] DC Cathodic Arc Deposition is a physical vapor deposition technology based on arc discharge. Its principle is to locally evaporate the target material through the arc spots (cathode spots) formed on the surface of the cathode target material and generate a plasma flow. Subsequently, ions are deposited on the substrate surface under the action of the electric field to form a coating. After searching the literature on the prior art, it was found that Martin Kuczyk et al. published an article titled "The Influence of Nitrogen Partial Pressure on the Microstructure and Mechanical Properties of HfNbTaTiVZr High-EntropyNitride Coating Deposited via Direct Current Cathodic Vacuum Arc Deposition" in "Coatings". The article pointed out that the plasma ionization rate generated by the cathode arc can reach more than 80% (magnetron sputtering is usually <10%), and high-energy ion bombardment of the substrate can enhance atomic mobility and significantly improve the film-base bonding strength. At the same time, further searching found that Wang et al. published an article titled "Study on the Cutting Performance of CrN / AlCrN-Coated Carbide PCB Milling" in "Coatings". The article "Cutter" (Study on the Cutting Performance of CrN / AlCrN Coated Carbide PCB Milling Cutters) points out that cathode arc plasma has strong penetrability and directionality, and can achieve uniform deposition on the spiral groove and micron-level tip of the milling cutter. Magnetron sputtering is prone to produce a "shadow effect" due to low-energy particle scattering, resulting in a tip coating loss rate of up to 30%. The CrN / AlCrN coating prepared by the cathode arc has significantly better coverage uniformity at the curvature radius (5-10μm) of the PCB milling cutter tip than magnetron sputtering. Summary of the Invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for depositing a TiAl / TiAlN / TiAlB / TiAlBN composite coating on the surface of a small milling cutter using a DC cathode arc method.

[0006] The purpose of the present invention is achieved through the following technical solutions:

[0007] A method for preparing a TiAl / TiAlN / TiAlB / TiAlBN composite coating on the surface of a small milling cutter using a DC cathode arc comprises the following steps:

[0008] Step 1: Milling cutter pretreatment: Select two small milling cutters and ultrasonically clean them in anhydrous ethanol and deionized water for 30 minutes respectively. Then, remove them and place them in a constant temperature drying oven at 70°C. After drying, remove them and cool them to room temperature before use.

[0009] Step 2: Ar ion cleaning. Place the pre-treated milling cutter into the chamber and evacuate the chamber to 2×10 -3 Pa, introduce Ar gas, adjust the turntable speed to 15 rad / min, turn on the Ar ion sputtering source power supply, adjust the coil current to 0.5A, the cathode current to 10A, and the anode voltage to 100V, and allow sputtering and cleaning to proceed for 10 minutes.

[0010] Step 3: TiAl transition layer deposition: After Ar ion cleaning, cool for 10 minutes, keep the turntable rotating, turn on the TiAl target cathode arc power supply, adjust the cathode current to 80A, and deposit for 5 minutes.

[0011] Step 4: TiAlN hard layer deposition. After the transition layer deposition is completed, cool for 5 minutes, introduce N2 into the chamber, and turn on the TiAl target cathode arc power supply again. The deposition parameters are the same as in step 3, and the deposition time is 10 minutes.

[0012] Step 5: Deposition of the TiAlB toughening layer and TiAlBN functional surface layer. The deposition process is similar to the previous steps and will not be repeated here. The TiAlB toughening layer deposition time is 5 minutes, while the TiAlBN functional surface layer deposition times are 20 minutes, 30 minutes, and 40 minutes. Finally, a four-layer TiAl / TiAlN / TiAlB / TiAlBN composite coating is deposited on the surface of the small milling cutter.

[0013] Step 6: Circuit board cutting test: Place the deposited milling cutter into a cutting instrument for a circuit board cutting test, compare the cutting results of the composite coating milling cutter with different deposition parameters with the edge wear data, and obtain the optimal deposition solution.

[0014] Compared with the prior art, the present invention has significant advantages:

[0015] 1. The coating instrument used in the present invention is a Vactime DLC dual-excitation source DC cathode arc and pulsed cathode plasma arc evaporation system independently developed and manufactured by the China-Belarus Vacuum Plasma Technology International Joint Laboratory. The technical principle of this equipment belongs to a type of vacuum cathode arc evaporation deposition. Compared with other composite thin film deposition equipment, it has the following four advantages: (1) It is equipped with an arc plasma focusing and thrust combination system, which can effectively control the arc area and improve the stability and transmission efficiency of the plasma during the transmission process; (2) In terms of the magnetic filtration system, it is designed with a unique magnetic field layout, which can control the path of the plasma in the magnetic field, thereby realizing the formation of a large-area uniform film on the surface of a complex workpiece; (3) In terms of arc stability, it is equipped with an arc stabilization accessory to improve the continuous burning capability of the arc and reduce the generation of large particles; (4) Three independently controllable target material excitation sources are set inside the vacuum chamber to realize the preparation of various composite films. The content of various doping elements in the composite film is precisely controlled by adjusting the working parameters of each excitation source.

[0016] 2. The present invention is highly operable and can further regulate the deposition time and parameters between the four layers with different functions. At the same time, various heat treatment schemes can be added for flexible transformation to obtain materials with expected performance according to different needs.

[0017] 3. The deposition process of the present invention only requires two alloy target materials. The method is simple and easy to operate. It has higher safety and strong repeatability on the basis of strong operability.

[0018] 4. The data obtained from the actual circuit board cutting test of the present invention showed that the edge wear of the small milling cutter was 22.96 μm after cutting a 5-meter-long circuit board. The results reflect the high bonding strength and wear resistance between the composite coating deposited by this method and the substrate. The test shows that it can meet actual application needs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 Schematic diagram of the working principle of Vactime DLC thin film deposition equipment.

[0020] Figure 2 This is a picture of the milling cutter sample obtained by deposition.

[0021] Figure 3 Sample picture of the circuit board used

[0022] Figure 4 This is the edge wear diagram obtained from actual testing. DETAILED DESCRIPTION

[0023] With reference to the accompanying drawings, an embodiment of the present invention is described in detail below. This embodiment is implemented based on the technical solution of the present invention, and a detailed implementation method and specific operation process are given. However, the protection scope of the present invention is not limited to the following embodiment.

[0024] The present invention takes a 2mm small milling cutter as an example to provide a detailed implementation method and specific operation. The following embodiment involves a five-step process including: milling cutter pretreatment, Ar ion cleaning treatment, TiAl transition layer deposition, TiAlN hard layer deposition, TiAlB toughening layer and TiAlBN functional surface layer deposition, wherein:

[0025] Step 1: Select two small milling cutters, place them in anhydrous ethanol and deionized water for ultrasonic cleaning for 30 minutes respectively, then take them out and put them into a constant temperature drying oven, dry them at a constant temperature of 70℃, take them out, cool them to room temperature and set aside.

[0026] Step 2: Place the pre-treated milling cutter into the chamber and evacuate the chamber to 2×10 -3 Pa, introduce Ar gas, adjust the turntable speed to 15 rad / min, turn on the Ar ion sputtering source power supply, adjust the coil current to 0.5A, the cathode current to 10A, and the anode voltage to 100V, and allow sputtering and cleaning to proceed for 10 minutes.

[0027] Step 3: After Ar ion cleaning, cool for 10 minutes, keep the turntable rotating, turn on the TiAl target cathode arc power supply, adjust the cathode current to 80A, and deposit the TiAl transition layer for 5 minutes.

[0028] Step 4: After the transition layer deposition is completed, cool for 5 minutes, introduce N2 into the chamber, turn on the TiAl target cathode arc power supply again, and deposit the TiAlN hard layer with the same deposition parameters as step 3 for 10 minutes.

[0029] Step 5: After the hard layer deposition is completed, cool for 5 minutes, close the N2 inlet pipe, turn on the TiAlB target cathode arc power supply, adjust the cathode current to 100A, and deposit the TiAlB toughening layer for 5 minutes.

[0030] Step 6: After the toughening layer deposition is completed, cool for 5 minutes, open the N2 inlet pipe again, and turn on the TiAlB target cathode arc power supply at the same time. The deposition parameters are consistent with step 4, and the TiAlBN functional surface layer is deposited. The deposition time is 20 minutes, 30 minutes, and 40 minutes. Finally, close the air inlet pipe and the target cathode arc power supply, cool for 15 minutes, and take out the milling cutter. The TiAl / TiAlN / TiAlB / TiAlBN composite coating is successfully deposited on the surface of the small milling cutter.

[0031] Step 7: After obtaining the three coating milling cutters with different parameters, a circuit board cutting test was carried out. The cutting edge data obtained after cutting a 5m circuit board showed that the 30min TiAlBN deposition performance was the best.

Claims

1. A method for preparing a TiAl / TiAlN / TiAlB / TiAlBN composite coating on the surface of a small milling cutter using a DC cathode arc, comprising: Milling cutter pretreatment, instrument coating deposition, and circuit board cutting testing: First, the selected small milling cutter is ultrasonically cleaned with anhydrous ethanol and deionized water to remove impurities from the surface and facilitate subsequent deposition. Four different coatings are deposited on the milling cutter using a Vactime DLC thin film deposition device, resulting in a TiAl / TiAlN / TiAlB / TiAlBN composite coating. The milling cutter with deposited coating was used to test the circuit board cutting, and specific edge wear data was obtained, confirming that the high bonding strength and wear resistance between the composite coating deposited by this method and the substrate can meet actual application requirements.

2. The TiAl / TiAlN / TiAlB / TiAlBN composite coating deposition method according to claim 1, wherein the specific steps are as follows: Step 1: Milling cutter pretreatment: Select two small milling cutters and ultrasonically clean them in anhydrous ethanol and deionized water for 30 minutes respectively. Then, remove them and place them in a constant temperature drying oven at 70℃. After drying, remove them and cool them to room temperature before use. Step 2: Thin film deposition. The pretreated milling cutter is placed in a chamber and first cleaned with Ar ions to further enhance surface activity. Four coatings, TiAl / TiAlN / TiAlB / TiAlBN, are then deposited in sequence, ultimately resulting in a TiAl / TiAlN / TiAlB / TiAlBN composite coating. Step 3: Circuit board cutting test: The milling cutter obtained by deposition is placed in a circuit board cutting instrument for circuit board cutting test. The wear data of the milling cutter edge after cutting is obtained. After comparison, the high bonding strength and high wear resistance coating design scheme is confirmed.

3. The high bonding strength and high wear resistance coating design scheme according to claim 2, wherein the specific deposition parameters are: TiAl layer deposition for 5 minutes, TiAlN layer deposition for 10 minutes, TiAlB layer deposition for 5 minutes, and TiAlBN layer deposition for 30 minutes. At the same time, the turntable in the chamber is kept open during deposition to ensure uniform film deposition.

4. The Vactime DLC thin film deposition device according to claim 2, wherein: Two target materials can be installed at the same time to achieve continuous deposition at the same time. At the same time, the instrument also has a magnetic filtration system to ensure that large particles generated by the cathode arc during the evaporation of the target material are screened out, making the deposited film denser and more uniform, and the film-base bonding better.

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