AlCrN / TiSiN / AlCrTiSiON pre-oxidation multilayer composite coating and preparation process thereof

Abstract

The invention discloses an AlCrN / TiSiN / AlCrTiSiON pre-oxidation multi-layer composite coating and a preparation process of the AlCrN / TiSiN pre-oxidation multi-layer composite coating, and belongs to the technical field of coatings. The bottommost layer of the composite coating is an AlCrN transition layer, and an AlCrN / TiSiN nano multilayer film and a TiSiN high-hardness layer are sequentially overlaid on the transition layer for 1-4 times; the nano multilayer film is a modulated coating formed by AlCrN layers and TiSiN layers through alternate deposition, has good toughness and can effectively reduce crack propagation; and the outermost layer is an AlCrTiSiON pre-oxidation coating, and the compact AlCrTiSiON pre-oxidation coating has excellent wear resistance and heat resistance. The coating is prepared by adopting an arc ion plating technology. Through process design and optimization of the coating structure and pre-oxidation layer process parameters, the pre-oxidation coating with high hardness, high wear resistance and high heat resistance is prepared.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to an AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating and a preparation process thereof. Background Art

[0002] Hard coating is a protective layer applied to the surface of the tool to improve the cutting performance of the tool. Selecting the appropriate coating composition and structure can effectively improve the mechanical properties and wear resistance of the tool, while providing chemical and thermal barriers. These coatings are usually based on TiN or CrN binary coatings, and further developed into multi-component coatings such as Ti(C,N) and (Ti,Al)N. In recent years, modern high-speed and dry cutting technology has developed rapidly, and the cutting temperature of the tool has also risen accordingly, reaching 1200℃ or even higher. Under high temperature conditions, elements such as Al, Cr, Si, and Ti in the coating will react with O, and the Gibbs free energy (ΔGo) of Al2O3 and TiO2 formation is -1336J and -753J respectively. Therefore, Al will diffuse outward preferentially and form an Al2O3 film on the surface of the coating. As the temperature rises, when there is insufficient Al in the surface layer, oxygen will diffuse to the inner layer, and a porous TiO2 oxide layer will be quickly generated in the sublayer. Porous TiO2 will cause the Al2O3 layer to break due to compressive stress, and accelerate the diffusion of Ti through these cracks, forming a loose, porous mixed (Al, Ti) oxide film on the coating surface. Under the action of high temperature and high pressure, the oxides and chips are constantly squeezed and accumulated, and a bonding layer is accumulated, which seriously limits the service performance and life of the coated tool at high temperature. Therefore, expanding the application range of nitride coatings and improving the thermal stability of tool nitride coatings has become one of the current research hotspots.

[0003] Previous studies have shown that by adjusting the structure, grain size, chemical composition and phase composition of the coating, the thermal stability of the coating can be further optimized on the basis of the original performance of the coating. Previous studies have shown the influence of different temperatures on the phase structure of nanocomposite TiN / TiB2 coatings. It was found that below 1000°C, the phase structure of the coating is in a stable state. At higher temperatures, the coating grains begin to coarsen, the number of nucleation points and the interface energy decrease, which in turn affects the thermal stability of the coating. In the AlCrN coating with high aluminum content, aluminum atoms will replace chromium atoms, affecting the grain size of the coating and effectively improving the oxidation resistance of the coating. In addition, the influence of different Al contents on the TiAlCrN coating was explored, and it was found that when the Al and Cr contents were 65-70at% and about 20at%, respectively, the coating exhibited excellent mechanical properties and oxidation resistance at high temperatures. Similarly, the study found that different Ti:Al ratios affect the maximum temperature of oxidation resistance, which ranges from 750°C to 900°C. This is related to the two-phase structure of c-TiN and h-AlN in the TiAlN coating and the larger atomic volume and higher nucleation barrier of h-AlN. The Al-Cr-ON and Zr-ON tool coatings were prepared by introducing oxygen elements. The study found that the doping of oxygen elements makes the coatings have excellent mechanical properties and tribological properties required by general hard coatings, and also shows good thermal stability and chemical stability of oxides. In the high-speed cutting of high-strength austempered ductile iron, the service life and processing efficiency of the tool are greatly improved. Mo elements were added to the CrN film to study the microstructure and high-temperature mechanical properties of the CrMoN coating. The results show that the CrMoN film still maintains the crystal structure and mechanical properties at room temperature after oxidation at 500℃ for 1h. However, with the increase of oxidation temperature, the evaporation amount of MoO3 on the film surface increases, the oxidation degree of the film increases, and small pores appear along it. After oxidation at 700℃ for 1h, the mechanical properties and film-substrate bonding strength of the CrMoN film decreased significantly. However, summarizing previous studies, it is found that there are few studies on improving the thermal stability of coatings by pre-oxidation treatment. Summary of the invention

[0004] In view of the problems in the prior art of high-strength and high-toughness difficult-to-process materials such as high-temperature alloys, such as high-temperature alloys, high cutting temperature, large cutting force, and easy oxidation and wear of the tool when processing, the purpose of the present invention is to provide an AlCrN / TiSiN / AlCrTiSiON pre-oxidized multi-layer composite coating and a preparation process thereof. Arc ion plating technology is used to prepare a layer of oxide film with a thickness of 100 to 200 nanometers on the surface of the AlCrN / TiSiN coating to form an AlCrN / TiSiN / AlCrTiSiON coating. Through process design and optimization of the oxide film thickness, a pre-oxidized coating with high hardness, high wear resistance and high heat resistance is prepared.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] An AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating is deposited on the surface of a substrate, wherein: the bottom layer is an AlCrN transition layer, and the transition layer is stacked 1-4 times in sequence by AlCrN / TiSiN nano multilayer film and TiSiN high hardness layer; the outermost layer is an AlCrTiSiON pre-oxidized coating, and the dense AlCrTiSiON pre-oxidized coating has excellent wear resistance and heat resistance.

[0007] Furthermore, the AlCrN transition layer has a columnar crystal structure and has good bonding performance with the substrate.

[0008] Furthermore, the AlCrN / TiSiN nano-multilayer film is a modulated coating formed by alternately depositing AlCrN layers and TiSiN layers. The total thickness of the AlCrN / TiSiN nano-multilayer film is 1-3 μm, the periodic thickness is 0.012-0.036 μm, and the modulation ratio AlCrN / TiSiN=3:1~1:3; the nano-multilayer film has good toughness as a functional layer and can effectively reduce crack propagation.

[0009] Furthermore, the chemical composition of the AlCrTiSiON pre-oxidation coating is: Al is 10.66-11.25wt.%, Cr is 10.30-10.21wt.%, Ti is 36.93-38.47wt.%, Si is 2.53-2.59wt.%, O is 2.45-13.45wt.%, and N is 24.18-26.91wt.%.

[0010] Furthermore, the AlCrTiSiON pre-oxidation coating includes TiO, AlN, TiN, and CrN crystal phases, wherein the TiO crystal phase is mainly composed of a face-centered cubic (fcc) structure.

[0011] Furthermore, the preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating is as follows: using arc ion plating technology to first deposit an AlCrN / TiSiN nano-multilayer film on a substrate, then deposit a TiSiN high-hardness layer, and finally deposit an AlCrTiSiON pre-oxidized coating; when depositing the AlCrTiSiON pre-oxidized coating, the background vacuum degree is 6×10 -5 Pa or above, deposition temperature 480-520℃, turn on AlCr target and TiSi target, arc source current of AlCr target is 120-140A, arc source current of TiSi target is 140-150A; introduce N2 and O2 at the same time, N2 flow rate is 1200-1300sccm, O2 flow rate is 20-50sccm, and the thickness of pre-oxidation coating is selected according to different experimental requirements.

[0012] The process specifically includes the following steps:

[0013] (1) Wash and dry the substrate, fix it on the sample plate, and hang it on the rotating rack in the coating room. Evacuate the coating room to a vacuum degree of 3.0×10 -4 Pa or above;

[0014] (2) performing IET etching and cleaning on the substrate;

[0015] (3) Deposition of AlCrN transition layer: Turn on the AlCr target and introduce N2 for 30 to 35 min.

[0016] (4) Deposition of AlCrN / TiSiN nano-multilayer film: AlCr target and TiSi target were alternately turned on, and the flow rate of N2 introduced was adjusted to 1260-1380 sccm. The total deposition time was 20-25 min, and an AlCrN / TiSiN nano-multilayer film with an alternating arrangement of AlCrN layer and TiSiN layer was obtained;

[0017] (5) Deposition of TiSiN high hardness layer: turn off the AlCr target, keep the TiSi target on, adjust the N2 flow rate to 1200-1260sccm, and the deposition time to 30-35min;

[0018] (6) Repeat steps (4) to (5) 0 to 3 times;

[0019] (7) Depositing an AlCrTiSiON pre-oxidation coating for 5-20 min, and finally obtaining an AlCrN / TiSiN / AlCrTiSiON pre-oxidation multilayer composite coating on the substrate.

[0020] Furthermore, in step (2), the IET etching and cleaning process is as follows: heating the furnace to 480-520°C, turning on the Ti target, and introducing Ar at a flow rate of 170-300 sccm, so that the deposition pressure is stabilized at 0.28-0.30 Pa, the Ti target arc source current is 130-140 A, the DC bias is set to gradually increase from -10 V to -180 V, and the IET etching and cleaning time is 60 min;

[0021] Further, in step (3), an AlCrN transition layer is deposited after IET etching and cleaning, wherein: N2 with a flow rate of 1200 to 1260 sccm is introduced to stabilize the deposition pressure at 3.5 to 4.5 Pa, the arc source current of the AlCr target is 120 to 140 A, and the DC bias voltage is -40 to -60 V;

[0022] Furthermore, in step (4), when depositing the AlCrN / TiSiN nano-multilayer film, the AlCr target arc source current is 120A, the TiSi target arc source current is 150A, the deposition pressure is 3.5-4Pa, and the DC bias voltage is -60V;

[0023] Furthermore, when depositing the TiSiN high hardness layer in step (5), the TiSi target arc source current is 150A, the deposition pressure is 3.5-4Pa, and the DC bias voltage is -60V.

[0024] Furthermore, the substrate is a metal cemented carbide substrate; the target material purity of the AlCr target and the TiSi target is both above 99.95%.

[0025] Furthermore, when depositing the AlCrTiSiON pre-oxidation coating, when the oxygen flow time is 5 minutes, the O content in the coating is 2.45wt.%; when the oxygen flow time is 10 minutes, the O content in the coating is 3.48wt.%; when the oxygen flow time is 15 minutes, the O content in the coating is 8.52wt.%; when the oxygen flow time is 20 minutes, the O content in the coating is 13.45wt.%.

[0026] The hardness of the AlCrTiSiON pre-oxidized coating is as high as 46.58 GPa, the friction coefficient of the coating is as low as 0.657, and the wear rate of the coating is as low as 3.18×10 -10 mm 3 / (mm·N).

[0027] The design mechanism of the present invention is as follows:

[0028] The invention adopts arc ion plating technology to deposit AlCrN / TiSiN / AlCrTiSiON coating on a hard alloy substrate.

[0029] Transition metal nitrides are widely used in the field of tool coatings due to their high hardness and high purity. With the application of difficult-to-process alloy materials such as titanium alloys, tungsten-molybdenum alloys, and high-temperature alloys, the cutting force and cutting temperature have increased sharply, and higher requirements have been put forward for the heat resistance of the tool. There are two main reasons for the failure of the tool at high temperature: 1. The temperature is too high, the coating softens and the hardness decreases, and the wear is aggravated; 2. The coating is oxidized and corroded at high temperature, and atoms enter the interior of the coating, causing the coating to fail. In recent years, metal oxide films have been widely used in the field of high-temperature protection due to their excellent heat resistance. For example, dense oxide films such as Al2O3 and Cr2O3 can effectively block the diffusion of external oxygen elements into the interior of the coating under high temperature conditions, and block the diffusion of Ti atoms inside the coating to the outside of the coating, playing an excellent chemical barrier role. Therefore, the present invention regulates the thickness of the oxide layer and cooperates with other process parameters (each target power, bias voltage, pressure, etc.), designs process conditions and optimizes the thickness of the oxide layer, and designs a nano multilayer functional layer in the coating to provide sufficient mechanical performance support. A 100-200 nanometer oxide film is prepared on the outermost layer to act as a chemical barrier and thermal barrier.

[0030] The advantages and beneficial effects of the present invention are as follows:

[0031] 1. The AlCrN / TiSiN / AlCrTiSiON coating prepared by the present invention has high wear resistance and obvious wear resistance effect.

[0032] 2. The AlCrN / TiSiN / AlCrTiSiON coating of the present invention maintains the original high hardness and high toughness characteristics of the AlCrN / TiSiN coating, and by adding a pre-oxidation protective layer, the heat resistance of the coating is increased, thereby preparing a pre-oxidation coating with high hardness, high wear resistance and high heat resistance.

[0033] 3. The AlCrN / TiSiN / AlCrTiSiON coating of the present invention has broad application prospects and is suitable for various difficult-to-process materials, greatly improving cutting efficiency and tool service life.

[0034] 4. The AlCrN / TiSiN / AlCrTiSiON coating of the present invention has excellent mechanical and tribological properties, and the coated tool can be suitable for heavy-load continued processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of the AlCrN / TiSiN / AlCrTiSiON composite protective coating prepared by arc ion plating technology in Example 1.

[0036] Figure 2XRD patterns of AlCrN / TiSiN / AlCrTiSiON composite coatings deposited at different oxygen flow times prepared by arc ion plating technology in Example 1.

[0037] Figure 3 The surface morphologies of the AlCrN / TiSiN / AlCrTiSiON composite coatings deposited at different oxygen permeation times prepared by arc ion plating technology in Example 1; wherein: (a) oxygen permeation for 5 min; (b) oxygen permeation for 10 min; (c) oxygen permeation for 15 min; (d) oxygen permeation for 20 min; (e) elemental composition of the coating surface after oxygen permeation for 10 min; and (f) an enlarged view of the peeling area on the coating surface after oxygen permeation for 20 min.

[0038] Figure 4 The cross-sectional morphologies of the AlCrN / TiSiN / AlCrTiSiON composite coatings deposited at different oxygen permeation times prepared by arc ion plating technology in Example 1; among them: (a) oxygen permeation for 5 min; (b) oxygen permeation for 10 min; (c) oxygen permeation for 15 min; (d) oxygen permeation for 20 min.

[0039] Figure 5 The hardness (HIT) and elastic modulus (EIT) of the AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen flow times prepared by arc ion plating technology in Example 1.

[0040] Figure 6 H / E and H of AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen flow times prepared by arc ion plating technology in Example 1 3 / E* 2 .

[0041] Figure 7 The critical load of the AlCrN / TiSiN / AlCrTiSiON coating deposited at different oxygen flow times prepared by arc ion plating technology in Example 1.

[0042] Figure 8 The scratch morphology of the AlCrN / TiSiN / AlCrTiSiON coating deposited at different oxygen flow times prepared by arc ion plating technology in Example 1.

[0043] Fig. 9 The friction coefficient and wear rate of the AlCrN / TiSiN / AlCrTiSiON coating deposited at different oxygen flow times prepared by arc ion plating technology in Example 1.

[0044] Fig.10The three-dimensional wear scar morphology of the AlCrN / TiSiN / AlCrTiSiON coating deposited at different oxygen permeation times prepared by arc ion plating technology in Example 1; among them: (a) oxygen permeation for 5 minutes; (b) oxygen permeation for 10 minutes; (c) oxygen permeation for 15 minutes; (d) oxygen permeation for 20 minutes. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below by way of examples.

[0046] The present invention adopts the "coating + pre-oxidation" method to form a stable, dense protective oxide thin layer in situ on the coating surface, which prevents the diffusion of harmful elements, reduces the conduction of cutting heat to the tool, enhances the coating's resistance to high-temperature oxidation and thermal stability, and thus improves the tool coating's resistance to oxidation wear and diffusion wear, thereby increasing the tool's service life and processing efficiency.

[0047] In the following examples, Al:Cr=70:30 (atomic ratio) in the AlCr target, Ti:Si=85:15 (atomic ratio) in the TiSi target, and the purity is both 99.95%.

[0048] Embodiment 1:

[0049] This example is to prepare AlCrN / TiSiN / AlCrTiSiON composite coatings with different oxygen permeation times.

[0050] This embodiment is to deposit AlCrN / TiSiN / AlCrTiSiON coating on a cemented carbide sheet (25mm×25mm×3.0mm) by arc ion plating technology. The specific operation steps are as follows:

[0051] (1) Substrate pretreatment: After polishing the cemented carbide substrate, place it in an ultrasonic cleaning machine and use acetone and alcohol for ultrasonic cleaning for 20 minutes respectively. After cleaning, blow it dry with high-purity N2 (99.99%). The substrate is fixed on the sample plate. After the vacuum chamber is vented, open the vacuum chamber furnace door, fix the sample plate on the rotating rack in the coating chamber with iron wire, and install the AlCr target and TiSi target to the arc target position; adjust the fixed position of the sample plate so that the substrate is facing the target surface to prevent the surface deposition distance from being different during the deposition process, resulting in uneven coating preparation. Check that there is no foreign matter left in the vacuum chamber and close the furnace door.

[0052] (2) Vacuuming: When depositing the coating, high vacuum conditions are required. The vacuuming process of the coating system is divided into two steps: a) rough pumping, turning on the pre-pump and Roots pump to pump the vacuum degree of the vacuum chamber to above 40 Pa; b) fine pumping, turning on the turbomolecular pump to pump the vacuum degree of the vacuum chamber to 3×10 -4 Pa or above;

[0053] (3) Heating: Set the heating temperature to 500°C and heat to the specified temperature for 30 minutes.

[0054] (4) IET etching and cleaning: Argon ion etching and metal ion etching (Ti) are carried out simultaneously, and the active components of the plasma include: ions, electrons, active groups, excited nuclides (metastable states), photons, etc. Utilizing the properties of these active components, fine particles are continuously accelerated to bombard the material surface, thereby achieving the purpose of improving the surface cleanliness of the material and stimulating the surface activity of the material. During IET etching and cleaning in this embodiment, the Ar flow rate is 175sccm, the deposition pressure is guaranteed to be 0.29Pa, the Ti target arc source current is 130A, the DC bias is gradually increased from -10V to -150V, and the etching and cleaning time is 60min.

[0055] (5) AlCrN transition layer: Turn on the AlCr target, introduce N2 at a flow rate of 1200 sccm, stabilize the deposition pressure at 0.30 Pa, set the AlCr target arc source current to 120 A, and the DC bias voltage to -40 V for 30 min.

[0056] (6) Deposition of AlCrN / TiSiN nano-multilayer films: AlCr target and TiSi target were turned on alternately, with the arc source current of AlCr target being 120A and the arc source current of TiSi target being 150A; the N2 flow rate was adjusted to 1320sccm, the pressure was stabilized at 3.6Pa, the DC bias was -60V, and the deposition was carried out for 20min.

[0057] (7) Deposition of TiSiN high hardness layer: turn off the AlCr target and keep the TiSi target on, with the arc source current of the TiSi target being 150A; adjust the N2 flow rate to 1200sccm, the deposition pressure to 3.5Pa, the DC bias voltage to -60V, and the deposition time to 30min.

[0058] (8) Repeat steps (6)-(7) once.

[0059] (9) Deposition of AlCrTiSiON pre-oxidized coating: AlCr target and TiSi target are turned on at the same time, and vacuum is evacuated to a vacuum degree of 6×10 -5 Pa, the arc source current was 120A and 150A respectively. The N2 flow rate was adjusted to 1234sccm, the oxygen flow rate was 25sccm, the deposition pressure was 3.5Pa, the DC bias was -50V, and the oxygen flow time of different samples was 0min (nitrogen only for 10min without oxygen), 5min (nitrogen and oxygen for 5min), 10min (nitrogen and oxygen for 10min), 15min (nitrogen and oxygen for 15min), and 20min (nitrogen and oxygen for 20min).

[0060] The morphology and performance of the AlCrN / TiSiN / AlCrTiSiON coatings prepared in this example with different oxygen permeation times were characterized as follows:

[0061] The phase composition of the coating was analyzed by X-ray diffractometer (XRD). The data was collected by step scanning. The incident X-ray was radiated by Cu target Kα characteristic spectrum (λ=0.154056nm), tube voltage was 40kV, tube current was 40mA, diffraction angle (2θ) scanning range was 20°~80°, scanning step length was 0.02°, and counting time per step was 0.2s. The surface and cross-sectional morphology of the coating were observed by S4800 field emission scanning electron microscope (SEM), and the chemical composition of the coating was analyzed by electron probe (EPMA, Shimadzu, EPMA1600).

[0062] The hardness and elastic modulus of the coating were tested by a nanoindenter (Anton Paar, TTX-NHT-3). To eliminate the influence of the matrix effect on the measurement results, the tip penetration depth was ensured to be no more than 1 / 10 of the coating thickness, and the average value was taken by measuring 15 points. The bonding strength between the coating and the cemented carbide substrate was measured by a scratch tester (Anton Paar RST-3). The diameter of the diamond tip was 200 μm, and the parameters were as follows: loading speed 6 mm / min; scratch length 3 mm; set load 100 N, and the experimental data was recorded in real time by a computer.

[0063] The friction coefficient was tested on a friction and wear tester (Anton Paar THT). The friction pair was selected with a 6mm diameter Al2O3 ball (hardness 22±1GPa), a sliding linear velocity of 0.1m / s, a normal load of 4N, a rotation radius of 6mm, and a sliding distance of 100m. The friction test was carried out at room temperature of 22±3℃ and humidity of 30%. Each sample was tested 3 times. The coating wear rate W was calculated using the formula W=V / (F×S) (V is the wear volume, F is the normal load, and S is the sliding distance). In addition, an ultra-depth microscope (VHX-1000C, Keyence) was used to observe the morphology of the coating after wear.

[0064] The structure of the AlCrN / TiSiN / AlCrTiSiON composite coating prepared in this embodiment is as follows: Figure 1As shown. The bottom layer of the coating is an AlCrN transition layer, and the columnar crystal structure of AlCrN has good bonding performance with the cemented carbide substrate. On the transition layer is an AlCrN / TiSiN nano-multilayer film, which is a modulated coating formed by alternating deposition of AlCrN layers and TiSiN layers. The total thickness of the nano-multilayer film is about 2μm, the periodic thickness is about 0.024μm, and the modulation ratio AlCrN / TiSiN=3:1~1:3; the nano-multilayer film has good toughness as a functional layer and can effectively reduce crack propagation; above the nano-multilayer film is a TiSiN high-hardness layer, and the amorphous-encapsulated nanocrystalline structure in the high-hardness layer can improve the hardness; in this embodiment, the above nano-multilayer film and the high-hardness layer repeat a cycle to meet the coating thickness requirements; the outermost layer is an AlCrTiSiON pre-oxidized coating, and the dense surface oxide film can improve the wear resistance and heat resistance of the coating.

[0065] Figure 2 The XRD patterns of AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen flow times are shown in the figure. As can be seen from the figure, the AlCrN / TiSiN / AlCrTiSiON coatings are mainly composed of TiO, AlN, TiN, and CrN crystal phases. Among them, the TiO crystal phase is mainly composed of a face-centered cubic (fcc) structure. The fcc-TiO (PDF#89-5010) phase diffraction peak was detected at 2θ=43.27°, but the TiO2 diffraction peak was not detected, which may be attributed to the coating deposition temperature of 500°C, at which temperature, TiO is more easily formed. Since no silicon oxynitride peak was detected, it may exist as amorphous silicon oxynitride. In the AlCrN / TiSiN / AlCrTiSiON coating, silicon mostly exists in the form of amorphous Si3N4 to form a nanocomposite coating structure. When oxygen is introduced during the deposition process, silicon is more likely to react with oxygen first to form SiO2 because ΔH(SiO2)=-910.86kJ / mol is higher than ΔH(Si3N4)=-760.00kJ / mol.

[0066] Figure 3The surface morphology of the AlCrN / TiSiN / AlCrTiSiON coatings deposited under different oxygen permeation times. As the oxygen permeation time increases, the coating surface changes significantly. When the oxygen permeation time is 5 minutes, there are irregular pits and pores on the coating surface, while when the oxygen permeation time is 10 minutes, the coating surface is uniform and dense, and defects such as large particles and pores are significantly improved. This is because the oxygen permeation time is too short to form a continuous and dense oxide layer, and the thickness of the oxide layer is only about 80nm, which cannot fill the original defects of the coating. When the oxygen permeation time is increased to 10 minutes, the density of the coating surface is significantly improved, showing an obvious crystal structure. Compared with coatings with other oxygen permeation times, this is a unique surface structure feature of 10 minutes of oxygen permeation, indicating that the oxide film formed corresponding to the oxygen permeation time has good bonding performance with the underlying AlCrN / TiSiN coating, and the thickness of the oxide film is appropriate. By analyzing the elemental composition and stoichiometric ratio of the coating surface at this time, it can be determined that the coating surface is mainly composed of metal oxides such as TiO2, Al2O3, and Cr2O3; when the oxygen flow time is 15 minutes, the surface particles are refined and the density is further improved, which is an inherent feature of the oxide coating. However, the coating surface defects increase, and larger holes and coating peeling appear. Observing the enlarged image of the coating surface peeling after 20 minutes of oxygen flow, it can be found that there are bright white particles at the peeling site. This is formed by the molten droplets formed by the evaporation of the target material during the deposition process and solidified on the coating surface, indicating that large-scale peeling of the coating occurs during the deposition process. The coating deposition temperature is 500°C. In an overly thick oxide layer, brittle peeling occurs under the action of internal stress in the coating under high temperature conditions.

[0067] Figure 4 The cross-sectional morphology of the AlCrN / TiSiN / AlCrTiSiON coating deposited under different oxygen flow times. It can be clearly observed that when the oxygen flow time is 5min and 10min, the coating structure is complete, the thickness is uniform, and the nano-scale oxide layer structure and thickness can be clearly observed. The oxide layer thickness is 80.34nm and 102.82nm, respectively. When the oxygen flow time is 15min and 20min, the coating cross section has no obvious characteristic structure, the fluctuation is large, and the thickness is uneven. Due to the partial peeling of the oxide layer, the thickness of the oxide layer cannot be determined. In addition, AlCrN / TiSiN multilayer structure and nano multilayer structure are designed inside the coating, but no obvious interface and stratification phenomenon are observed. This is attributed to the universal magnetic field system and arc source technology of the multi-arc ion plating equipment, which makes the layers of the coating tightly bonded and the coating has high density.

[0068] Figure 5The hardness (HIT) and elastic modulus (EIT) of the AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen permeation times. The hardness of the coatings showed a trend of increasing first and then decreasing under different oxygen permeation times. The maximum value of 46.58 GPa was reached when the oxygen permeation time was 10 min, which was attributed to the formation of dense Al2O3, Cr2O3 and other hard oxide films on the surface of the coating. The hard oxide phase improved the ability of the coating to resist external loads pressing into its surface. However, as the oxygen permeation time continued to increase, the hardness and elastic modulus of the coating dropped sharply, and the hardness was only 24.91 GPa when the oxygen permeation time was 20 min. When the oxide film is too thick, vacancy defects will be generated in the cubic lattice of the coating, which will cause the nanohardness and elastic modulus of the coating to decrease. In addition. The oxide is relatively brittle, especially when the thickness increases, so the ability of the coating to resist elastic deformation decreases with the increase of oxygen permeation time.

[0069] Figure 6 H / E and H of AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen flow times 3 / E* 2 The ratio of H to E represents the ability of the coating to resist plastic deformation. The higher the ratio of hardness to elastic modulus, the better the wear resistance of the coating. 3 With E* 2 The ratio represents the ability of the coating to resist plastic deformation. With the increase of oxygen permeation time, the characteristic value of the AlCrN / TiSiN / AlCrTiSiON multilayer coating first increases and then decreases, reaching the maximum value of 0.101 and 0.390 GPa respectively when the oxygen permeation time is 10 minutes. This shows that the coating has good toughness when the oxygen permeation time is 10 minutes.

[0070] Figure 7 The critical load of the AlCrN / TiSiN / AlCrTiSiON coating deposited under different oxygen flow times. As can be seen from the figure, there is no significant difference in the critical load of the coating under different oxygen flow times, all reaching more than 70N. According to the mechanical industry standard JB / T 8554-1997, the critical load Lc3 when the coating is completely scratched to expose the substrate is used as the basis for judgment. The oxygen flow time is short, the thickness of the oxide layer is only 100 to 200 nanometers, and the overall thickness of the coating is about 2μm. Therefore, the critical load of the coating and the substrate mainly depends on the bonding performance of the transition layer and the substrate. On the other hand, it also shows that oxygen is introduced while the target is opened, and only a thin oxide film is formed on the surface of the coating. The oxygen element does not enter the interior of the coating to destroy the coating structure and performance.

[0071] Figure 8The scratch morphology of the AlCrN / TiSiN / AlCrTiSiON coating deposited under different oxygen flow times. By observing the scratch morphology, it can be found that the scratch morphology at the critical load Lc3 of the coating is very different under different oxygen flow times. When the oxygen flow is 5min and 10min, the two sides of the scratch are relatively complete, the scratch surface is smooth and there is no wear debris accumulation. When the oxygen flow is 10min and 20min, brittle peeling occurs on both sides of the scratch, and the coating at the scratch is plastically sheared and slipped. At this time, the toughness of the coating is low, and cracks appear in the coating under a larger load. As the load increases, hard oxide debris participates in the scratch, resulting in shell-shaped cracks and plastic deformation on the scratch surface. Therefore, it can be judged that the excessive thickness of the oxide film has a negative impact on the adhesion of the coating.

[0072] Fig. 9 The friction coefficient and wear rate of the AlCrN / TiSiN / AlCrTiSiON coating deposited at different oxygen permeation times. With the increase of oxygen permeation time, the friction coefficient of the coating first increases and then decreases. When the oxygen permeation time is 15 minutes, the average friction coefficient of the coating is the lowest, which is 0.657. Under different oxygen permeation times, the wear rate of the coating shows an upward trend, but it is still lower than that of the AlCrN / TiSiN coating before pre-oxidation, which proves that the preparation method of "coating + pre-oxidation" has significant advantages in improving wear resistance.

[0073] Fig.10 The three-dimensional wear scar morphology of AlCrN / TiSiN / AlCrTiSiON coatings deposited at different oxygen permeation times. It is observed that the coatings are completely worn through, the wear scar depth is about 0.5μm, and the two sides of the wear scar are relatively complete. When the oxygen permeation time is 10min, there are micro-grooves along the friction direction, with obvious abrasive wear characteristics. As the oxygen permeation time continues to increase, the wear scar width increases and more wear debris accumulates at the wear scar. Therefore, it can be preliminarily judged that the wear mechanism of the coating is adhesive wear. The change of this wear mechanism is closely related to the hardness and surface quality of the coating. When the oxygen permeation time is 10min, the coating hardness is the highest. During the friction and wear process, the hard oxide particles on the coating surface participate in the friction process to form micro-grooves. At 15min and 20min, the coating hardness is low and the surface quality is poor. The wear debris participates in the friction process and is crushed by the grinding pair and adheres to the friction area. In addition, with the increase of oxygen permeation time, the porous and brittle TiO2 on the coating surface grows rapidly, the thickness of the oxide film increases, the residual stress inside the coating deteriorates the Al2O3 protective layer, and reduces the wear resistance of the coating. .

[0074] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.

Claims

1. An AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating, characterized in that: The multi-layer composite coating is deposited on the surface of the substrate, wherein: the bottom layer is an AlCrN transition layer, and the transition layer is stacked 1-4 times in sequence by AlCrN / TiSiN nano multilayer film and TiSiN high hardness layer; the outermost layer is an AlCrTiSiON pre-oxidation coating, and the dense AlCrTiSiON pre-oxidation coating has excellent wear resistance and heat resistance.

2. The AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 1, characterized in that: The AlCrN transition layer has a columnar crystal structure and has good bonding performance with the substrate.

3. The AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 1, characterized in that: The AlCrN / TiSiN nano-multilayer film is a modulation coating formed by alternately depositing AlCrN layers and TiSiN layers. The total thickness of the AlCrN / TiSiN nano-multilayer film is 1-3 μm, the period thickness is 0.012-0.036 μm, and the modulation ratio AlCrN / TiSiN=3:1-1:

3. As a functional layer, the nano-multilayer film has good toughness and can effectively reduce crack propagation.

4. The AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 1, characterized in that: The chemical composition of the AlCrTiSiON pre-oxidized coating is: Al is 10.66-11.25wt.%, Cr is 10.30-10.21wt.%, Ti is 36.93-38.47wt.%, Si is 2.53-2.59wt.%, O is 2.45-13.45wt.%, and N is 24.18-26.91wt.%.

5. The AlCrN / TiSiN / AlCrTiSiON pre-oxidized multi-layer composite coating according to claim 1, characterized in that: The AlCrTiSiON pre-oxidation coating comprises TiO, AlN, TiN and CrN crystal phases, wherein the TiO crystal phase is mainly composed of a face-centered cubic (fcc) structure.

6. The preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to any one of claims 1 to 5, characterized in that: The process uses arc ion plating technology to first deposit AlCrN / TiSiN nano-multilayer film on the substrate, then deposit TiSiN high-hardness layer, and finally deposit AlCrTiSiON pre-oxidized coating; When depositing AlCrTiSiON pre-oxidized coating, the background vacuum is 6×10 -5 Pa or above, deposition temperature 480-520℃, turn on AlCr target and TiSi target, arc source current of AlCr target is 120-140A, arc source current of TiSi target is 140-150A; introduce N2 and O2 at the same time, N2 flow rate is 1200-1300sccm, O2 flow rate is 20-50sccm, and the thickness of pre-oxidation coating is selected according to different experimental requirements.

7. The preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 6, characterized in that: The process specifically includes the following steps: (1) Wash and dry the substrate, fix it on the sample plate, and hang it on the rotating rack in the coating room. Evacuate the coating room to a vacuum degree of 3.0×10 -4 Pa or above; (2) performing IET etching and cleaning on the substrate; (3) Deposition of AlCrN transition layer: Turn on the AlCr target and introduce N2 for 30 to 35 min. (4) Deposition of AlCrN / TiSiN nano-multilayer film: AlCr target and TiSi target were alternately turned on, and the flow rate of N2 introduced was adjusted to 1260-1380 sccm. The total deposition time was 20-25 min, and an AlCrN / TiSiN nano-multilayer film with an alternating arrangement of AlCrN layer and TiSiN layer was obtained; (5) Deposition of TiSiN high hardness layer: turn off the AlCr target, keep the TiSi target on, adjust the N2 flow rate to 1200-1260sccm, and the deposition time to 30-35min; (6) Repeat steps (4) to (5) 0 to 3 times; (7) Depositing an AlCrTiSiON pre-oxidation coating for 5-20 min, and finally obtaining an AlCrN / TiSiN / AlCrTiSiON pre-oxidation multilayer composite coating on the substrate.

8. The preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 7, characterized in that: In step (2), the IET etching and cleaning process is as follows: heating the furnace to 480-520°C, turning on the Ti target, and introducing Ar with a flow rate of 170-300 sccm, so that the deposition pressure is stabilized at 0.28-0.30 Pa, the Ti target arc source current is 130-140A, the DC bias is set to gradually increase from -10V to -180V, and the IET etching and cleaning time is 60min; In step (3), an AlCrN transition layer is deposited after IET etching and cleaning, wherein: N2 with a flow rate of 1200 to 1260 sccm is introduced to stabilize the deposition pressure at 3.5 to 4.5 Pa, the arc source current of the AlCr target is 120 to 140 A, and the DC bias voltage is -40 to -60 V; When depositing the AlCrN / TiSiN nano-multilayer film in step (4), the AlCr target arc source current is 120A, the TiSi target arc source current is 150A, the deposition pressure is 3.5-4Pa, and the DC bias voltage is -60V; When depositing the TiSiN high hardness layer in step (5), the TiSi target arc source current is 150A, the deposition pressure is 3.5-4Pa, and the DC bias voltage is -60V.

9. The preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 7, characterized in that: The substrate is a metal hard alloy substrate; the purity of the AlCr target and the TiSi target is both above 99.95%.

10. The preparation process of the AlCrN / TiSiN / AlCrTiSiON pre-oxidized multilayer composite coating according to claim 7, characterized in that: When depositing the AlCrTiSiON pre-oxidized coating, when the oxygen flow time is 5 minutes, the O content in the coating is 2.45wt.%; when the oxygen flow time is 10 minutes, the O content in the coating is 3.48wt.%; when the oxygen flow time is 15 minutes, the O content in the coating is 8.52wt.%; when the oxygen flow time is 20 minutes, the O content in the coating is 13.45wt.%.

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