A cBN / AlN nanocomposite cutter coating based on template effect growth and a preparation method thereof

Abstract

A cubic boron nitride / aluminum nitride (cBN / AlN) nanocomposite cutting tool coating based on template effect growth and a preparation method, characterized in that the composite cutting tool coating structure is sequentially from inside to outside: base template material-AlN coating-cBN coating-AlN coating-cBN coating-AlN coating-cBN coating……, wherein the outermost layer of the cBN / AlN nanocomposite cutting tool coating is the cBN coating, the AlN coating is alternately grown inside, and the thickness of the cBN coating and the AlN coating inside is within the critical coherent thickness range. The application can effectively reduce the residual stress in the film caused by ion bombardment. In the application, the cBN / AlN nanocomposite cutting tool coating based on template effect growth reaches or exceeds the hardness of the cBN coating, meanwhile, the hetero-interface in the coating increases the toughness of the composite coating, improves the wear resistance and impact resistance of the coating tool, and is used for high-speed cutting of difficult-to-machine materials such as titanium alloy, high-temperature alloy, high-strength steel and composite materials.

Description

TECHNICAL FIELD

[0001] The present application relates to a tool superhard coating preparation technology, mainly a cBN / AlN nano composite cutter coating based on template effect growth and a preparation method, in particular to a cBN / AlN nano composite cutter coating and a preparation method, which introduces a template transition layer on a hard alloy, high speed steel and ceramic cutter substrate through multi-target unbalanced magnetron sputtering on the surface of the cutter, grows a nano cubic aluminum nitride coating on the surface of the template transition layer, and then forms the cBN / AlN nano composite cutter coating through the alternative growth of the nano cubic aluminum nitride and nano cubic boron nitride as templates. BACKGROUND

[0002] With the continuous progress of the national economy and science and technology, new materials are developing rapidly, and difficult-to-machine materials such as titanium alloy, high-temperature alloy, ultra-high strength steel, composite material and engineering ceramics are increasingly applied in modern industry. However, the cutting tool is subjected to harsh working conditions such as high temperature and high pressure during cutting of difficult-to-machine materials, and the tool wears seriously and has a short service life. For example, in the milling process of high-temperature alloy blades of an aero-engine, the tool wears severely, and the tool consumption is 6-10 times that of milling ordinary materials, which has become a major factor affecting the quality and efficiency of workpiece machining. Traditional high speed steel and cemented carbide tools wear seriously during cutting, and the service life of the tool is short. Although ceramic tools have high hardness and wear resistance, the toughness of ceramic tools is low, and the tool is prone to collapse during high-speed cutting, causing tool failure. Therefore, it is necessary to develop and prepare high-quality tools with high hardness, high carrying capacity, good toughness, good chemical stability and excellent friction and wear properties to meet the urgent needs of the manufacturing industry for domestic high-performance tools.

[0003] Cubic Nitride Boron (cBN) is a high hardness material with the second highest hardness to diamond, high wear resistance, stable chemical properties, and thermal conductivity of 13 W / (cm×K), about 3-4 times of copper. It is very stable in chemical properties when machining black metals at high temperatures, and is an ideal tool material for machining superalloys, titanium alloys and high-strength steels. The cBN tool on the market is mainly polycrystalline cubic boron nitride (PcBN) tool, but due to the presence of the binder, the excellent wear resistance of cBN cannot be fully utilized. cBN coated tool is suitable for any complex shape of tool substrate, and the expected cost is much lower than that of PcBN tool after industrial production, which is one of the most promising tool coating materials for cutting of difficult-to-machine materials such as superalloys and high-strength steels. After years of efforts by researchers, the preparation technology of cBN coating has made significant progress, and the quality of cBN coating has been further improved. However, so far, the high stress and high brittleness of cBN coating have not been broken through, and the main reasons for the high stress of cBN coating are the large number of defects in the coating caused by the physical property difference between the cBN coating and the tool substrate and the huge ion bombardment energy required for the formation of cBN, which leads to poor anti-peeling performance of the coating. In addition, cBN coating is a brittle material, and high brittleness can easily cause tool coating fracture, which greatly restricts the application of cBN coated tool.

[0004] Under the condition of low-energy particle bombardment, forming high-quality cBN coating and increasing the toughness of tool coating without reducing the strength of the coating are the main problems to be solved for the application of cBN coated tool. The present application aims to improve the toughness of cBN coated tool and reduce the stress of the coating, and selects cubic aluminum nitride (AlN) as a modulation layer to grow cBN / AlN nanometer multilayer composite coating through the template effect of the modulation layer, to obtain a cBN / AlN multilayer structure coating tool preparation technology with independent intellectual property rights, to break through the technical bottleneck existing in the industrial application of cBN coated tool, and to meet the demand of modern manufacturing industry for high-performance coated tool. SUMMARY

[0005] The purpose of the present application is to solve the problems of large internal stress and low toughness of cBN tool coating, and to invent a cBN / AlN nanocomposite tool coating based on template effect growth, and to provide a corresponding preparation method.

[0006] One of the technical solutions of the present application is:

[0007] The application discloses a cubic boron nitride / aluminum nitride (cBN / AlN) nano-composite cutter coating based on template effect growth, characterized by the following structure from inside to outside: a substrate template material-AlN coating-cBN coating-AlN coating-cBN coating-AlN coating-cBN coating-…, wherein the outermost layer of the cBN / AlN nano-composite cutter coating is the cBN coating, and the AlN coating is alternately grown in the inside, and the thickness of the cBN coating and the AlN coating in the inside is within the range of critical co-crystal thickness.

[0008] The substrate template material comprises TiN or other thin film materials.

[0009] The second technical scheme of the application is:

[0010] A preparation method of the cBN / AlN nano-composite cutter coating based on template effect growth, characterized by the following steps:

[0011] 1) Pre-sputtering of the cutter surface;

[0012] The cutter substrate cleaned by the acetone solution is placed into a vacuum deposition cavity, gas Ar is introduced, an anode linear ion source is turned on, and at the same time, the cutter substrate is subjected to particle bombardment for 10-20 min by applying a bias to the cutter substrate; then N2 is introduced, and the cutter substrate is subjected to Ar and N2 mixed particle bombardment for 5-10 min.

[0013] 2) Growth of a template transition layer;

[0014] The sputtering target 1 in a multi-target unbalanced magnetron sputtering system is turned on to grow a template layer on the pretreated cutter substrate surface, and the coating thickness is kept between 400 nm and 600 nm.

[0015] 3) Co-crystal growth of c-AlN and cBN coatings;

[0016] The sputtering target 2 in the multi-target unbalanced magnetron sputtering system is used to co-crystal grow a c-AlN coating on the substrate template coating surface, and the coating thickness is controlled to be within the critical co-crystal thickness or below; then the sputtering target 3 in the multi-target unbalanced magnetron sputtering system is used to co-crystal grow a cBN coating by taking the c-AlN coating as a template material for cBN growth, and the coating thickness is controlled to be within the critical co-crystal thickness or below.

[0017] 4) Preparation of the cBN / AlN nano multi-layer cutter coating;

[0018] The c-AlN and cBN nano-coating layers are alternately grown on the surface of the tool substrate by alternately sputtering and depositing the sputtering target 2 and the sputtering target 3 in a multi-target non-equilibrium magnetron sputtering system, and the process parameters are controlled. The total thickness of the adjacent cBN and AlN coating layers is a modulation period, the thickness ratio of the adjacent cBN and AlN coating layers is a modulation ratio, the modulation period and the modulation ratio are controllable and adjustable, but the thickness of each layer is below the critical coherent thickness of the coating, and the total thickness of the coating is controlled between 3-5 microns.

[0019] The tool substrate comprises a cemented carbide, a high-speed steel or a ceramic tool.

[0020] The tool surface pre-sputtering comprises an Ar particle bombardment substrate surface stage (pure Ar=40 sccm) and an Ar / N2 particle co-bombardment substrate surface stage, and the total gas flow is 40 sccm, wherein Ar / N2=1:4; the working gas pressure during the bombardment process is kept at 0.4Pa-0.8Pa, the anode layer linear ion source power is 50W-300W, and the substrate applied bias is -250V~ -350V.

[0021] The template layer mainly comprises TiN and VC coatings.

[0022] The c-AlN and cBN coating layers are coherently grown, that is, the c-AlN is sputtered and grown on the surface of the template layer, the sputtering target material is a metal Al target with a purity of 99.99%, a direct current sputtering power source is adopted, and the sputtering power is 100W; the c-AlN is sputtered and grown on the surface of the c-AlN, the sputtering target material is a hot-pressed hBN target with a purity of 99.99%, a radio frequency sputtering power source is adopted, and the radio frequency power is 250W. Other process parameters include: base vacuum degree: 5.0*10 -4 Pa; substrate temperature: 500°C; anode source power 100W; total gas flow 35sccm, wherein N2:Ar=1:6; deposition gas pressure: 0.8Pa. The critical coherent thickness of the c-AlN coating layer is 10nm, and the critical coherent thickness of the cBN is 16nm, and no substrate bias is applied during the growth process.

[0023] In the preparation of the cBN / AlN nano-multilayer coating tool, the cBN and AlN coating preparation process parameters refer to the two coating growth process parameters in claim 3, and the specific coating thickness is adjusted by controlling the growth time.

[0024] The present application utilizes at least three sputtering targets to work, wherein the first target sputtering grows a substrate template film, the second target sputtering grows an AlN film, and the third target sputtering grows a cBN film, wherein the bottom film is a template layer of the upper film, and the stable phase to metastable phase transition of the film is realized through the coherent stress at the interface of the template film and the hetero film, so as to obtain metastable phase c-AlN and cBN films.

[0025] The application adopts a radio frequency magnetron sputtering device to grow cBN based on a template effect and alternately deposit AlN coating and cBN coating to form a cBN / AlN composite cutter coating with a nano multi-layer composite structure.

[0026] 1) The cBN coating grown based on a template effect can significantly reduce particle bombardment energy in the cBN growth process, reduce internal defects of the coating, and improve the compactness of the coating.

[0027] 2) Reducing the bombardment energy in the cBN growth process can significantly reduce the internal stress of the coating and improve the adhesion of the coating to the cutter substrate.

[0028] 3) The cBN / AlN multi-layer composite structure increases the hetero-interface in the coating, hinders the crack propagation in the coating, and thus improves the toughness and fatigue resistance of the coating.

[0029] 4) The process has low cost and high efficiency, which is conducive to the large-scale production of the coating cutter. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The cBN / AlN nano composite cutter coating structure grown based on a template effect according to the application.

[0031] Figure 2 XPS spectrum of the surface of the boron nitride coating.

[0032] Figure 3 SEM morphology diagram of the surface of the cubic boron nitride coating. EMBODIMENT

[0033] The application will be further described below in combination with the drawings and examples: EXAMPLE

[0034] A cBN / AlN nano composite cutter coating grown based on a template effect is prepared by the following steps:

[0035] 1) Pre-sputtering of the cutter surface;

[0036] The cemented carbide or high-speed steel cutter substrate cleaned with an acetone solution is placed into a vacuum deposition cavity, the base vacuum degree of the cavity is adjusted to 5.0x10 -4 Pa; argon gas is introduced with a total flow rate of 40 sccm, the anode layer linear ion source is turned on with a power of 100 W, the cutter substrate is biased at -250 V, and the cutter substrate is subjected to particle bombardment for 15 min; then the flow rate control valve is adjusted, N2 is introduced at a flow rate of 8 sccm, the flow rate control valve reduces the Ar flow rate to 32 sccm, and the cutter substrate is subjected to Ar and N2 mixed particle bombardment for 5 min.

[0037] 2) Template transition layer growth

[0038] The background vacuum of the chamber was adjusted to 5.0 x 10 -4 Pa; substrate temperature: 400 °C; anode source power 100 W; total gas flow 35 sccm, wherein N2: Ar = 1:6; deposition pressure: 0.8 Pa, and the base bias was -50 V. The direct current sputtering power (sputtering target 1) was turned on, the sputtering power was adjusted to 100 W, the metal Ti target with a purity of 99.999% was sputtered, and a TiN template layer was grown on the surface of the cutter base, and the deposition time was 20 min.

[0039] 3) Epitaxial growth of c-AlN and cBN coatings

[0040] The background vacuum of the chamber was adjusted to 5.0 x 10 -4 Pa; substrate temperature: 500 °C; anode source power 100 W; total gas flow 35 sccm, wherein N2: Ar = 1:6; deposition pressure: 0.8 Pa. The bias power supply and sputtering target 1 were turned off in turn, the direct current sputtering power (sputtering target 2) was turned on, the sputtering power was adjusted to 100 W, the metal Al target with a purity of 99.999% was sputtered, and the sputtering growth time was 3 min; then the sputtering target 2 was turned off, the radio frequency sputtering power (sputtering target 3) was turned on, the radio frequency power was 250 W, the hot-pressed hBN target with a purity of 99.999% was sputtered, and the sputtering growth time was 10 min.

[0041] 4) Preparation of cBN / AlN nanolayer coated cutters

[0042] By repeating step 3, a cBN / AlN nanolayer coating was formed as shown in Figure 1 The total thickness of adjacent cBN and AlN coatings was a modulation period, the thickness ratio of adjacent cBN and AlN coatings was a modulation ratio, and the modulation period and modulation ratio were controllable and adjustable, but the total thickness of the coating was controlled at about 3 μm. A cBN / AlN nanolayer coated cutter with low stress and good toughness was prepared, and the surface morphology is shown in Figure 3 . Example

[0043] A cBN / AlN nanocomposite cutter coating based on template effect growth was prepared by the following steps:

[0044] 1) Cutter surface pre-sputtering;

[0045] After cleaning the cemented carbide or high-speed steel tool substrate with acetone solution, place it into the vacuum deposition chamber, introduce Ar gas at a total flow rate of 40 sccm, turn on the linear ion source of the anode layer and adjust the power to 100W, apply a bias voltage of -250V to the tool substrate, and bombard the tool substrate with particles for 15 minutes; then adjust the flow control valve to introduce N2 at a flow rate of 8 sccm, reduce the Ar flow rate to 32 sccm, and bombard the tool substrate with mixed Ar and N2 particles for 5 minutes.

[0046] 2) Template transition layer growth;

[0047] Adjust the base vacuum level of the chamber: 5.0 × 10 -4 Pa; Substrate temperature: 400°C; Anode source power: 100W; Total gas flow rate: 35 sccm, where N2:Ar = 1:6; Deposition gas pressure: 0.8 Pa; Substrate bias: -50V. Turn on the DC sputtering power supply (sputtering target 1), adjust the sputtering power to 100W, and sputter a 99.999% pure V metal target to grow a VN template layer on the tool substrate surface. The deposition time is 20 min.

[0048] 3) Coherent growth of c-AlN and cBN coatings;

[0049] Adjust the base vacuum level of the chamber: 5.0 × 10 -4 Pa; Substrate temperature: 500°C; Anode source power: 100W; Total gas flow rate: 35sccm, where N2:Ar = 1:6; Deposition gas pressure: 0.8Pa. The bias power supply and sputtering target 1 were sequentially turned off, and the DC sputtering power supply (sputtering target 2) was turned on. The sputtering power was adjusted to 100W, and a 99.999% pure Al metal target was sputtered for 3 minutes. Then, sputtering target 2 was turned off, and the RF sputtering power supply (sputtering target 3) was turned on. The RF power was 250W, and a 99.999% pure hBN target was sputtered for 10 minutes.

[0050] 4) Preparation of cBN / AlN nano-multilayer coated cutting tools;

[0051] By repeating step 3 using a multi-target unbalanced magnetron sputtering method, a product is formed as shown in the image. Figure 1 The cBN / AlN nanolayered coating is shown. The total thickness of adjacent cBN and AlN coatings is the modulation period, and the thickness ratio of adjacent cBN and AlN coatings is the modulation ratio. The modulation period and modulation ratio are controllable and adjustable, but the total coating thickness is controlled to be around 3 μm. A cBN / AlN nanolayered tool with low stress and good toughness was prepared, and the surface morphology is shown in the figure. Figure 3 As shown. Example

[0052] The difference between the embodiment and the embodiments one and two is that the insulating Si3N4 blade is used as the base material, and the following conditions are met: before the TiN or VN is deposited on the surface of the Si3N4 blade, a layer of metal Ti or metal V is deposited on the surface of the blade, and the specific deposition process parameters are as follows: the base vacuum degree of the cavity is adjusted to 5.0*10 -4 Pa; the anode source power is 100 W; the total flow of Ar gas is 35 sccm; the deposition gas pressure is 0.8 Pa; and the base bias is -100 V. The direct current sputtering power (sputtering target 1) is turned on, the sputtering power is adjusted to 100 W, the metal Ti or V target with a purity of 99.99% is sputtered, the conductive transition layer is grown on the surface of the blade base, and the deposition time is 10 min. The rest is the same as in the embodiments one and two.

[0053] The part not involved in the application and the prior art is the same as or can be realized by using the prior art.

Claims

1. A method for preparing a nanocomposite coating for cutting tools based on template effect growth, characterized by: The method comprises the following steps: 1) pre-sputtering the tool surface; placing the tool substrate cleaned with an acetone solution into a vacuum deposition chamber, introducing Ar gas, opening an anode layer linear ion source, and applying a bias voltage to the tool substrate to bombard the tool substrate with particles for 10-20 min; then introducing N2 and using Ar and N2 mixed particles to bombard the tool substrate for 5-10 min; 2) growing a template layer; opening a first sputtering target in a multi-target unbalanced magnetron sputtering system to grow a template layer on the surface of the pre-sputtered tool substrate, and keeping the thickness of the coating layer at 400-600 nm; the template layer is a TiN or VN coating layer; 3) growing a c-AlN and cBN coating layer in a coherent manner; using a second sputtering target in the multi-target unbalanced magnetron sputtering system to grow a c-AlN coating layer on the surface of the template layer, and controlling the thickness of the c-AlN coating layer to be below the critical coherent thickness; then using the c-AlN coating layer as a template material for cBN growth, using a third sputtering target in the multi-target unbalanced magnetron sputtering system to grow a cBN coating layer in a coherent manner, and controlling the thickness of the cBN coating layer to be below the critical coherent thickness; no bias voltage is applied to the substrate during the growth process; 4) preparing a cBN / c-AlN nanometer multi-layer tool coating layer; alternately sputtering and depositing through the second and third sputtering targets in the multi-target unbalanced magnetron sputtering system to alternately grow c-AlN and cBN nanometer coating layers on the surface of the tool substrate by controlling the process parameters; taking the total thickness of adjacent cBN and c-AlN coating layers as the modulation period and the thickness ratio of adjacent cBN and c-AlN coating layers as the modulation ratio, and the modulation period and the modulation ratio are controllable and adjustable, but the thickness of each layer is below the critical coherent thickness of the coating layer, and the total thickness of the coating layer is controlled to be 3-5 μm; thereby obtaining a nanometer composite tool coating layer, and the structure of the nanometer composite tool coating layer from inside to outside is: template layer-(c-AlN coating layer)-cBN coating layer-(c-AlN coating layer)-cBN coating layer-(c-AlN coating layer)-cBN coating layer……, and the outermost layer is a cBN coating layer.

2. The method of claim 1, wherein: The tool substrate comprises a cemented carbide, a high-speed steel, or a ceramic tool.

3. The method of claim 1, wherein: The working gas pressure during the bombardment process is maintained at 0.4-0.8 Pa, the anode layer linear ion source power is 50-300 W, and the bias voltage applied to the substrate is-250 to-350 V.

4. The method of claim 1, wherein: In step 3), the c-AlN is sputtered and grown on the surface of the template layer, the sputtering target material is an Al target with a purity of 99.999%, a direct current sputtering power source is used, and the sputtering power is 100 W; the cBN is sputtered and grown on the surface of the c-AlN, the sputtering target material is a hot-pressed hBN target with a purity of 99.999%, a radio frequency sputtering power source is used, and the radio frequency power is 250 W; the critical coherent thickness of the c-AlN coating layer is 10 nm, and the critical coherent thickness of the cBN coating layer is 12 nm.

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