Preparation process of AlCrMoTiSiN high-entropy alloy coating with self-lubricating performance

Abstract

The invention discloses a preparation process of an AlCrMoTiSiN high-entropy alloy coating with a self-lubricating property, and belongs to the technical field of coatings. And depositing the high-entropy alloy coating on the substrate by adopting an arc ion plating technology. When the AlCrMoTiSiN high-entropy alloy coating is prepared, the background pressure intensity is pumped to be 3 * 10 <-3 > Pa, the deposition pressure intensity is 2.8 Pa, the pulse bias voltage is-100 V, the frequency is 50 KHz, and the pulse width is 6 microseconds; the deposition temperature is 400-480 DEG C, the AlCrSi target current is 100 A, the CrMo target current is 80-125 A, the AlTiSi target current is 90 A, and Ar, N2 and H2 are introduced; according to the preparation method, the high-entropy alloy coating with high hardness and a self-lubricating function is prepared through process design and optimization of the Mo element content.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, and in particular to a preparation process of an AlCrMoTiSiN high entropy alloy coating with self-lubricating properties. Background Art

[0002] In order to realize the machining concept of "high-precision manufacturing and efficient processing, green and low-pollution emissions", high-speed dry cutting has become the mainstream of modern manufacturing technology. As the "teeth" of CNC machine tools, cutting tools play a vital role in the field of machine tool processing. As a kind of surface modification technology, tool coating technology provides chemical and thermal barriers for cutting tools, avoids direct contact between cutting tools and workpieces, hinders the mutual diffusion of elements between cutting tools and workpieces, improves the mechanical strength, high-temperature oxidation resistance, anti-adhesion, and abrasive wear resistance of cutting tools, and achieves the effect of improving the service life of cutting tools, reducing production costs, and optimizing surface processing quality.

[0003] With the development of aerospace, automobile production, military and medical fields, the demand for some difficult-to-process materials (tungsten-molybdenum alloys, hardened steel, titanium alloys, etc.) is increasing, and at the same time, the requirements for material processing efficiency and quality are becoming more and more stringent. Due to the low thermal conductivity of these difficult-to-process materials, the chips are in powder form, the contact range and time between the tool and the chips are short, the heat conduction is not timely, and the cutting temperature is high, which easily causes adhesive wear on the back face of the tool. At the same time, the hardness of the difficult-to-process materials themselves is high, and the cutting force is large during processing, resulting in serious damage to the tool. Applying a wear-resistant coating with a self-lubricating function on the surface of the tool is an effective protective method to reduce tool wear. The development of advanced tool coatings with self-lubricating functions can effectively reduce the friction between the workpiece and the tool, reduce cutting heat, alleviate friction and wear between the tool and the workpiece, achieve "life extension" of the tool, and reduce production costs.

[0004] AlCrTiSiN coating has excellent mechanical properties, high temperature oxidation resistance and corrosion resistance, and is widely used as a high-performance coating. However, its high friction coefficient and poor wear resistance limit its development in the field of high-speed cutting. Summary of the invention

[0005] In order to further improve the wear resistance of the existing AlCrTiSiN coating, the purpose of the present invention is to provide a preparation process of an AlCrMoTiSiN high entropy alloy coating with self-lubricating properties, and the Mo element is doped into the AlCrTiSiN coating by arc ion plating technology to form an AlCrMoTiSiN high entropy alloy coating. The AlCrMoTiSiN high entropy alloy coating with high hardness, high wear resistance and self-lubricating properties is prepared by process design and optimization of the Mo element content.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A preparation process of an AlCrMoTiSiN high entropy alloy coating with self-lubricating properties, the process is to deposit the AlCrMoTiSiN high entropy alloy coating on a substrate using arc ion plating technology, and specifically comprises the following steps:

[0008] (1) The substrate was cleaned, blown dry, fixed on the sample plate, and hung on the rotating rack in the coating chamber. The metal AlCrSi target, AlTiSi target, and CrMo target were placed on the corresponding cathode target positions respectively; the vacuum was evacuated to a vacuum degree of 3.0×10 -3 Pa or above;

[0009] (2) performing glow discharge cleaning and ion bombardment cleaning on the substrate in sequence;

[0010] (3) Depositing a CrMoN transition layer for 15 min to improve the bonding strength between the working layer and the substrate;

[0011] (4) Deposition of AlCrMoTiSiN high entropy alloy coating.

[0012] In the above step (2), the glow discharge cleaning process is as follows: the furnace is heated to 400-480°C, and the vacuum is continuously evacuated to a vacuum degree of 3×10 -3 Pa, introduce Ar with a flow rate of 380-420sccm, adjust the deposition pressure to be stable at 2.2-2.6Pa, pulse bias -780~-800V, frequency 10KHz, pulse width 6μs, and glow cleaning for 18-22min.

[0013] In the above step (2), the ion bombardment cleaning process is as follows: after glow discharge cleaning, introduce Ar with a flow rate of 180-200sccm, adjust the deposition pressure to be stable at 1.1-1.2Pa, turn on the CrMo target, the CrMo target current is 95A, keep the same frequency and pulse width as during glow discharge cleaning, first bombard for 10 minutes under a pulse bias of -800V, and then bombard for 2 minutes each under pulse biases of -600V, -400V, and -200V in sequence.

[0014] In the above step (3), the process of depositing the CrMoN transition layer is as follows: after glow discharge cleaning and ion bombardment cleaning, keep the CrMo target open, introduce Ar with a flow rate of 180-220sccm and N2 with a flow rate of 190-210sccm, adjust the deposition pressure to be stable at 1.6-1.7Pa, pulse bias voltage -100V, frequency 50KHz, pulse width 8μ, and deposition time 15min.

[0015] When the AlCrMoTiSiN high entropy alloy coating is deposited in step (4), the background vacuum is 3×10 -3 Pa or above, deposition temperature 400-480 ℃, deposition pressure 2.8Pa; turn on AlCrSi target, AlTiSi target and CrMo target, AlCrSi target current 100A, AlTiSi target current 90A, CrMo target current 90-125A (preferably 98-120A), introduce protective gas Ar, reaction gas N2 and reducing gas H2, deposition time 100-150min, select CrMo target current according to different experimental requirements.

[0016] When depositing the AlCrMoTiSiN high entropy alloy coating in the above step (4), the Ar flow rate is 50sccm, the N2 flow rate is 600sccm, and the H2 flow rate is 10sccm; the pulse bias voltage is -100V, the pulse bias frequency is 50KHz, and the pulse width is 6μs.

[0017] Furthermore, the substrate is a metal (hard alloy substrate or SUS 304 stainless steel sheet) or a silicon sheet. The purity of the CrMo target material is 99.8%, and the purity of other target materials is 99.95%.

[0018] Furthermore, in the AlCrMoTiSiN high entropy alloy coating, Al is 9.84 at.%-33.52 at.%, Cr is 19.59 at.%-38.16 at.%, Mo is 3.75 at.%-6.98 at.%, Ti is 2.06 at.%-5.31 at.%, Si is 1.01 at.%-5.5 at.%, and N is 36.52 at.%-44.26 at.%.

[0019] Furthermore, when depositing the AlCrMoTiSiN high-entropy alloy coating, when the CrMo target current is 95A, the Mo content in the coating is 4.05at.%; when the CrMo target current is 100A, the Mo content in the coating is 6.39at.%; when the CrMo target current is 110A, the Mo content in the coating is 6.98at.%; when the CrMo target current is 120A, the Mo content in the coating is 6.57at.%.

[0020] Furthermore, the AlCrMoTiSiN high entropy alloy coating mainly contains AlN, Mo2N, CrN, and TiN crystal phases, and all crystal phases are composed of a face-centered cubic (fcc) structure.

[0021] The hardness of the AlCrMoTiSiN high entropy alloy coating is as high as 26.2 GPa, the friction coefficient of the coating is as low as 0.571, and the wear rate of the coating is as low as 0.822×10 -9 mm 3mm -1 ·N -1 .

[0022] The design mechanism of the present invention is as follows:

[0023] The invention adopts arc ion plating technology to deposit AlCrMoTiSiN high entropy alloy coating on hard alloy sheet, SUS 304 stainless steel and single crystal Si sheet.

[0024] TiN coating has better hardness and wear resistance than CrN coating, and is widely used in cutting tool surface protection. During high-speed dry cutting, the temperature between the tool tip and the workpiece is as high as 800℃. Since it is easily oxidized at high temperature, the cutting performance and life of the tool are reduced. Diversification is one of the effective ways to improve the performance of tool coatings. Ti element is now added to AlCrSiN coating to form AlCrTiSiN nanocomposite coating. AlCrTiSiN coating has high hardness, toughness and thermal stability, so it is widely used. However, during dry cutting, the friction coefficient and poor toughness of AlCrTiSiN coating cause damage to the tool. The transition metal Mo element is an ideal solid lubricant. Mo element is easy to react with O to form a layered MoO3 lubricating phase. The MoO3 layer has a low shear modulus, which is easy to slip, and provides a lubricating interface due to the weakening of the van der Waals force of the interlayer crystals. Therefore, the present invention adjusts the CrMo target current and coordinates other process parameters (bias voltage, gas flow rate, pressure, etc.), designs process conditions and optimizes the Mo element content, so as to further improve the hardness and wear resistance of the coating without significantly reducing the mechanical properties and tribological properties of the AlCrTiSiN coating, and give full play to the high hardness, high toughness and low wear characteristics of the high entropy alloy coating with self-lubricating properties.

[0025] The advantages and beneficial effects of the present invention are as follows:

[0026] 1. The AlCrMoTiSiN high entropy alloy coating prepared by the present invention has high wear resistance and obvious wear resistance effect.

[0027] 2. The AlCrMoTiSiN high entropy alloy coating of the present invention maintains the original high hardness, high strength and high toughness characteristics of the AlCrTiSiN coating, and gives full play to the synergistic effect of the high entropy alloy coating and the self-lubricating coating, and has the advantages of high hardness, high wear resistance, stable chemical properties, etc.

[0028] 3. When depositing the AlCrMoTiSiN high entropy alloy coating, the Ar flow rate is 50sccm, the N2 flow rate is 600sccm, and the H2 flow rate is 10sccm; the pulse bias voltage is -100V, the frequency of the pulse bias voltage is 50KHz, and the pulse width is 6μs. Among them, H2 is used as a reducing gas, and its flow rate is controlled. On the one hand, an appropriate amount of H2 is used to remove the residual O impurities in the vacuum chamber, and on the other hand, it will not affect the coating quality (such as excessive H2 will reduce the mechanical properties of the coating), and finally a high-purity and high-performance AlCrMoTiSiN high entropy alloy coating is prepared.

[0029] 4. The AlCrMoTiSiN high entropy alloy coating of the present invention has broad application prospects and is suitable for high-speed dry cutting of various difficult-to-cut materials, greatly improving cutting efficiency and tool service life.

[0030] 5. The AlCrMoTiSiN high entropy alloy coating of the present invention has excellent mechanical properties and tribological properties, and the coated tool can be suitable for heavy-load continued processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The elemental compositions of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology under different CrMo target currents in Example 1.

[0032] Figure 2 XRD patterns of the AlCrMoTiSiN high entropy alloy coatings prepared by arc ion plating technology at different CrMo target currents in Example 1.

[0033] Figure 3 Surface morphologies of AlCrMoTiSiN high entropy alloy coatings prepared by arc ion plating technology in Example 1 at different CrMo target currents; wherein: (a) target current 0A; (b) target current 95A; (c) target current 100A; (d) target current 110A; (e) target current 120A.

[0034] Figure 4 The cross-sectional morphologies of the AlCrMoTiSiN high entropy alloy coatings prepared by arc ion plating technology in Example 1 at different CrMo target currents; among them: (a) target current 0A; (b) target current 95A; (c) target current 100A; (d) target current 110A; (e) target current 120A.

[0035] Figure 5 The hardness and elastic modulus of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology under different CrMo target currents in Example 1.

[0036] Figure 6H / E and H of AlCrMoTiSiN high entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents in Example 1 3 / E* 2 .

[0037] Figure 7 The critical load of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology under different CrMo target currents in Example 1.

[0038] Figure 8 The scratch morphology of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology in Example 1 under different CrMo target currents; among them: (a) target current 0A; (b) target current 95A; (c) target current 100A; (d) target current 110A; (e) target current 120A.

[0039] Fig. 9 The friction coefficient and wear rate of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology under different CrMo target currents in Example 1.

[0040] Fig.10 The wear scar morphology of the AlCrMoTiSiN high entropy alloy coating prepared by arc ion plating technology in Example 1 under different CrMo target currents; among them: (a) target current 0A; (b) target current 95A; (c) target current 100A; (d) target current 110A; (e) target current 120A. DETAILED DESCRIPTION

[0041] The present invention is further described in detail below by way of examples.

[0042] The existing AlCrTiSiN coating has poor wear resistance. In order to further improve its friction performance without reducing its hardness and other properties, the present invention optimizes the service performance of the coating by doping the lubricating phase Mo element. The content of the lubricating phase has a great influence on the coating. The present invention has concluded through a large number of experimental studies that if the content of the lubricating phase is low, the supply cannot meet the consumption during the friction and wear process, and the lubrication effect is not obvious; when the content of the lubricating phase is high, the mechanical strength and other properties of the material will decrease; only when the content of the lubricating phase is moderate, an effective lubricating film can be formed to reduce the friction coefficient.

[0043] In the following embodiments, the metal target AlCrSi target has Al:Cr:Si=6:3:1 (atomic ratio), the AlTiSi target has Al:Ti:Si=6:3:1 (atomic ratio), and the CrMo target has Cr:Mo=85:15 (atomic ratio). The purity of the CrMo target is 99.8%, and the purity of the other targets is 99.95%.

[0044] Embodiment 1:

[0045] This embodiment is to prepare AlCrMoTiSiN high entropy alloy coatings with different Mo contents.

[0046] This embodiment deposits AlCrMoTiSiN high entropy alloy coating on single crystal Si wafer (30mm×30mm×0.67mm), cemented carbide wafer (25mm×25mm×3.0mm) and stainless steel wafer (35mm×35mm×1.0mm), using fully automatic arc ion plating technology for coating. The specific operation steps are as follows:

[0047] (1) Substrate pretreatment: After polishing the cemented carbide substrate, place it in an ultrasonic cleaning machine with the pre-prepared single crystal Si wafer and 304 stainless steel sheet, and use acetone and alcohol for ultrasonic cleaning for 20 minutes each. 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 place the metal AlCrSi target, AlTiSi target, and CrMo target on the corresponding cathode target position respectively; 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.

[0048] (2) Vacuuming: Since the molecular pump cannot work when the pressure in the vacuum chamber is higher than 4.0Pa, vacuuming is divided into two steps. First, vacuuming is started at atmospheric pressure. The vacuum chamber is evacuated using a TRP-90 roughing pump. When the vacuum degree is roughly drawn to 4.0Pa, the mechanical pump and the molecular pump are turned on to accelerate the molecular pump. When the acceleration is completed and the vacuum degree is lower than 4.0Pa, the fine pumping valve is opened to further evacuate the chamber until the pressure in the vacuum chamber reaches 3.0×10 -3 Pa, turn on the heating source to heat the vacuum chamber, set the final temperature to 460°C, and the alarm temperature to 465°C. During the heating process, the turntable keeps rotating at 40Hz to ensure that the substrate is heated evenly. -3 Pa or above.

[0049] (3) Glow discharge cleaning of the vacuum chamber: When the temperature and vacuum degree in the vacuum chamber meet the requirements, introduce Ar400sccm into the vacuum chamber, adjust the pressure in the vacuum chamber to be stable at 2.4Pa, pulse bias -800V, frequency 10KHz, pulse width 6μs, deposition time 20min, the purpose is to remove impurities and oxide layer on the surface of the substrate.

[0050] (4) Bombard and clean the target surface: introduce 200 sccm of Ar, adjust the deposition pressure to be stable at 1.2 Pa, turn on the CrMo target, the CrMo target current is 95 A, keep the frequency and pulse width unchanged (frequency 10 kHz, pulse width 6 μ), bombard at a pulse bias of -800 V for 10 min, and then bombard at pulse biases of -600 V, -400 V, and -200 V for 2 min each, in order to remove impurities and oxide layers on the target surface.

[0051] (5) Deposition of CrMoN transition layer: Keep the CrMo target open, introduce 200 sccm of N2 and 200 sccm of Ar, adjust the deposition pressure to be stable at 1.65 Pa, pulse bias voltage -100 V, frequency 50 kHz, pulse width 8 μs, and deposition for 15 min.

[0052] (6) Deposition of AlCrMoTiSiN high entropy alloy coating: introduce Ar 50sccm, N2 600sccm and H210sccm, adjust the deposition pressure to be stable at 2.8Pa, pulse bias -100V, frequency 50KHz, pulse width 6μs, set the CrMo target current of different samples to 0A, 95A, 100A, 110A, 120A, AlCrSi target current 100A, AlTiSi target current 90A, and deposition time 120min.

[0053] The morphology and performance of the AlCrMoTiSiN high entropy alloy coatings with different Mo contents prepared in this example were characterized as follows:

[0054] 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).

[0055] 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 SUS 304 stainless steel 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.

[0056] 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)0 (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.

[0057] Figure 1 The element composition of the AlCrMoTiSiN high entropy alloy coating prepared with different CrMo target currents. As can be seen from the figure, with the increase of the CrMo target current, the Cr content increases from 19.59at.% to 38.16at.% and then decreases to 35.58at.%, and the Al content shows a downward trend, from 33.52at.% to 9.84at.%, and the Mo content increases from 0 to 6.98at.% and then decreases to 6.57at.%. Studies have shown that the difference in the content of Al and Cr elements is related to the average valence state of the target elements in the plasma, and the elements with high melting points have high average valence states. Since the melting point of Cr is higher than that of Al, the average valence state of Cr is also higher than that of Al. Under the action of the negative bias power supply, Al exhibits negative segregation and Cr exhibits positive segregation. With the increase of the CrMo target current, more Cr and Mo elements are sputtered out, and the total number of atoms in the vacuum chamber increases, resulting in a decrease in the relative number of atoms of Al, Si, and Ti elements in the coating. The study found that the bond energy of Mo2N is 228.3eV, which is much lower than the bonding energy of AlN and CrN. During the preparation process of the coating, the ionized nitrogen element combines with the Mo element to generate Mo2N, and more Mo is sputtered out to combine with the N element, resulting in an increase in the N element content.

[0058] Figure 2XRD patterns of AlCrMoTiSiN high entropy alloy coatings prepared with different CrMo target currents. As can be seen from the figure, the coatings are mainly composed of AlN, Mo2N, CrN, and TiN crystal phases, and all coatings present a face-centered cubic (fcc) structure. No oxides were detected in the coatings, indicating that the residual O element in the vacuum chamber has been completely removed. No Si content was detected in the coatings, indicating that the silicon element exists in an amorphous or solid solution-strengthened form. With the increase of the CrMo target current and the increase of the Mo element, more Mo atoms replace the positions of Al, Cr, and Ti in the AlCrN and AlTiN lattices, forming (Al, Cr, Mo) N and (Al, Ti, Mo) N substitutional solid solutions, resulting in lattice distortion, broadening of the diffraction peaks, and grain refinement. As the CrMo target current increases, more Mo atoms replace more Cr atoms, and the replaced Cr combines with N to form fcc-CrN phase diffraction peaks. The diffraction peak intensity of the fcc-CrN phase along the (200) and (311) crystal planes increases. The preferential growth along the (111) crystal plane gradually transitions to the (200) crystal plane, which is related to the surface energy and strain energy of the coating. In order to reduce the internal stress of the coating, the face-centered cubic structure coating will grow along the direction with the minimum strain energy. At this time, there is a certain internal stress that causes the coating to preferentially grow along the (200) crystal plane with lower strain energy.

[0059] Figure 3 The surface morphology of AlCrMoTiSiN high entropy alloy coatings prepared with different CrMo target currents. As can be seen from the figure, there are no obvious cracks on the surface of all coatings, but defects such as large particles, droplets, and pits left by droplet peeling appear on the surface. These defects are caused by arc ion plating technology. The working principle of arc ion plating technology is that when the arc is discharged, a large number of cathode arc spots appear on the cathode target surface. The arc spots move on the target surface to generate arc heat, and the target material evaporates to produce ions. Due to the high arc heat temperature, some areas of the target surface melt, forming a granular liquid deposited on the coating surface. When the Mo element is not doped, large-diameter particles and cavities formed by shedding appear on the coating surface, but the particle size of the coating surface doped with Mo element becomes smaller. When the CrMo target current is 100A, the particles on the coating surface are smaller, the number is reduced, and the structure is dense. The increase in the CrMo target current promotes the enhancement of the particle surface migration ability, promotes the crystallization process of the coating, increases the nucleation rate of crystallization, and thus refines the grains. Grain refinement makes the coating surface more dense. Further increasing the CrMo target current will cause a large number of voids to appear on the coating surface. The reason is that the increase in target current increases the plasma density, causing solid solution of ions before they reach the substrate, resulting in pit defects on the surface.

[0060] Figure 4The cross-sectional morphology of the AlCrMoTiSiN high entropy alloy coating prepared with different CrMo target currents. As can be seen from the figure, all coatings present a dense columnar structure and grow perpendicular to the substrate. The cross section of the AlCrMoTiSiN high entropy alloy coating is relatively smooth, with a columnar crystal structure and regular arrangement, which is consistent with the surface morphology. With the increase of the CrMo target current, the film thickness of the coating decreases first and then increases. When the CrMo target current is 100A, the coating structure is the most dense, and the surface large particles are the least. The reason is that during the sputtering process of the CrMo target, the particles have strong migration ability, high crystallinity, and the grains grow, making the coating structure more dense. With the further increase of the CrMo target current, it may be due to the excessive target current that the particles fail to migrate effectively when they reach the surface of the substrate and are locked in the nucleation area by other particles, promoting the recrystallization of the grains. At the same time, combined with the XRD graph, the reduction of N content reduces the amorphous specific gravity of the coating, inhibits the amorphous encapsulation of nanocrystals, and leads to the increase of columnar crystals.

[0061] Figure 5 The hardness and elastic modulus of the AlCrMoTiSiN high entropy alloy coating prepared with different CrMo target currents. The hardness represents the ability of the coating to resist deformation, while the elastic modulus refers to the ratio of stress to strain within the elastic deformation range. With the increase of Mo content, the hardness and elastic modulus of the coating both show a trend of increasing first and then decreasing. When the CrMo target current is 100A, the hardness and elastic modulus of the coating both reach the maximum value, i.e., 26.192GPa and 424.003GPa. According to the solid solution strengthening mechanism, the Mo atoms in the coating replace part of the Al and Cr atoms in the (Al,Cr)N lattice to form the (Al,Cr,Mo)N solid solution phase. Due to the different atomic radii, the lattice distortion is caused, and the hardness of the coating is increased by increasing the grain boundary dislocation. When the CrMo target current is further increased, the hardness of the coating decreases. The reason may be that the Mo2N soft phase in the coating increases, which reduces the hardness of the coating. In addition, according to the Hall-Petch theory, the smaller the grain size, the more grains per unit area, thereby improving the strength of the coating. In contrast, larger grain size has a negative impact on the hardness of the coating.

[0062] Figure 6 H / E and H of AlCrMoTiSiN high entropy alloy coatings with different Mo contents 3 / E *2 Fig. H / E characterizes the coating's ability to resist elastic deformation, H 3 / E *2 Characterizes the coating's ability to resist plastic deformation. H / E and H 3 / E *2 The larger the value, the better the toughness of the coating. With the increase of Mo content, the characteristic values ​​of the coating generally show a trend of first increasing and then decreasing. When the CrMo target current is 100A, the H / E and H3 / E *2 The maximum values ​​of H / E and H / E are 0.062 and 0.083 GPa, respectively. At this time, the coating has the best resistance to elastic strain failure and plastic deformation, indicating that the Mo element improves the hardness and toughness of the coating. 3 / E *2 It shows a decreasing trend, which is attributed to the fact that the excessively high target current increases the large particles of molten droplets on the coating surface, resulting in a loose coating structure, thereby reducing the characteristic values ​​of the coating.

[0063] The critical load indicates the external force that the coating is subjected to when it is separated from the substrate, that is, the magnitude of the coating adhesion. Figure 7 and Figure 8 The critical load and scratch morphology of AlCrMoTiSiN high entropy alloy coatings with different Mo contents. As can be seen from the figure, with the increase of CrMo target current, the bonding strength of the coating shows a trend of first increasing and then decreasing. When the CrMo target current is 0A, the worst bonding strength of the coating is 64.91N, and the incorporation of Mo element improves the bonding strength of the coating. When the CrMo target current is 110(2)A, the bonding strength of the coating is the largest, which is 81.32N. This is because the target current increases linearly and the heat flux increases. At this time, the high-energy particles directly bombard the substrate surface, causing the surface atoms to produce high temperature and high pressure in the nearby micro-region, thereby improving the bonding strength between the coating and the substrate.

[0064] Fig. 9 The friction coefficient and wear rate of the AlCrMoTiSiN high entropy alloy coating with different CrMo target currents are shown in Figure 2. With the increase of CrMo target current, the friction coefficient and wear rate both decrease first and then increase. When the CrMo target current is 100A, the friction coefficient and wear rate both reach the minimum value, which are 0.571 and 0.822×10 -9 mm 3 ·N -1 mm -1 The addition of Mo element causes AlCrMoTiSiN high entropy alloy coating to produce a large amount of MoO3 lubricating phase during the friction process, which changes the direct contact between the grinding pairs into indirect contact with a lubricating film, reduces the interface friction, and reduces the friction coefficient. At this time, the wear resistance of the coating is the best. With the further increase of CrMo target current, the hardness and H / E of the coating show a downward trend, and the wear resistance cannot be guaranteed, so the friction coefficient and wear rate both increase. For AlCrTiSiN coating, the friction coefficient and wear rate of AlCrMoTiSiN high entropy alloy coating are significantly reduced, indicating that the addition of Mo element improves the tribological properties of the coating.

[0065] Fig.10The three-dimensional wear scar morphology of AlCrMoTiSiN high entropy alloy coatings with different CrMo target currents after room temperature friction test. As can be seen from the figure, all five coatings show different degrees of wear. The AlCrTiSiN coating wears the most seriously. Combined with the surface morphology of the coating, there are a small number of large particles on the surface of the coating. During the friction process, the friction pair squeezes the surface of the coating to cause some particles to peel off. Continued friction will cause obvious band-shaped micro-grooves, causing abrasive wear. With the increase of CrMo target current, the wear on the coating surface changes from abrasive wear to adhesive wear, and the contact between the friction pair and the coating produces a lubricating phase to resist relative sliding. When the CrMo target current is 100A, the degree of wear of the coating is the smallest and the wear scar is the narrowest. At this time, the friction coefficient is the smallest, the damage capacity of the coating is the smallest, no abrasive wear occurs at the wear scar, and the wear performance of the coating is the best.

[0066] 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. A preparation process of an AlCrMoTiSiN high entropy alloy coating with self-lubricating properties, characterized in that: The process uses arc ion plating technology to deposit AlCrMoTiSiN high entropy alloy coating on the substrate, which specifically includes the following steps: (1) The substrate was cleaned, blown dry, fixed on the sample plate, and hung on the rotating rack in the coating chamber. The metal AlCrSi target, AlTiSi target, and CrMo target were placed on the corresponding cathode target positions respectively; the vacuum was evacuated to a vacuum degree of 3.0×10 -3 Pa or above; (2) performing glow discharge cleaning and ion bombardment cleaning on the substrate in sequence; (3) Depositing a CrMoN transition layer for 15-20 min to improve the bonding strength between the working layer and the substrate; (4) Deposition of AlCrMoTiSiN high entropy alloy coating.

2. The preparation process of the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: In step (2), the glow discharge cleaning process is as follows: heating the furnace to 400-480°C, and continuing to evacuate the furnace to a vacuum degree of 3×10 -3 Pa, introduce Ar with a flow rate of 380-420sccm, adjust the deposition pressure to be stable at 2.2-2.6Pa, pulse bias -780~-800V, frequency 10KHz, pulse width 6μs, and glow cleaning for 18-22min.

3. The preparation process of the AlCrMoTiSiN high entropy alloy coating with self-lubricating function according to claim 1, characterized in that: In step (2), the ion bombardment cleaning process is as follows: after glow discharge cleaning, introduce Ar with a flow rate of 180-200sccm, adjust the deposition pressure to be stable at 1.1-1.2Pa, turn on the CrMo target, the CrMo target current is 95-100A, keep the same frequency and pulse width as those during glow discharge cleaning unchanged, first bombard for 9-12min under a pulse bias of -780V to -810V, then bombard for 2-4min each under pulse bias of -590 to -602V, -390 to -410V, and -195V to -205V in sequence.

4. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: In step (3), the process of depositing the CrMoN transition layer is as follows: after glow discharge cleaning and ion bombardment cleaning, keep the CrMo target open, introduce Ar with a flow rate of 180-220sccm and N2 with a flow rate of 190-210sccm, adjust the deposition pressure to be stable at 1.6-1.7Pa, pulse bias voltage -90 to -110V, frequency 50KHz, pulse width 8μ, and deposition time 15-18min.

5. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: When depositing the AlCrMoTiSiN high entropy alloy coating in step (4), the background vacuum is 3×10 -3 Pa or above, deposition temperature 400-480 ° C, deposition pressure 2.7-2.8Pa; turn on AlCrSi target, AlTiSi target and CrMo target, AlCrSi target current 95-100A, AlTiSi target current 85-95A, CrMo target current 90-125A (preferably 98-120A), introduce protective gas Ar, reaction gas N2 and reducing gas H2, deposition time 100-150min, select CrMo target current according to different experimental requirements.

6. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 5, characterized in that: When depositing the AlCrMoTiSiN high entropy alloy coating in step (4), the Ar flow rate is 48-52sccm, the N2 flow rate is 590-605sccm, and the H2 flow rate is 8-12sccm; the pulse bias voltage is -95 to -110V, the pulse bias frequency is 50KHz, and the pulse width is 6μs.

7. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: The substrate is a metal (hard alloy substrate or SUS 304 stainless steel sheet) or a silicon sheet. The purity of the CrMo target material is 99.8%, and the purity of other target materials is 99.95%.

8. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: In the AlCrMoTiSiN high entropy alloy coating, Al is 9.84 at.%-33.52 at.%, Cr is 19.59 at.%-38.16 at.%, Mo is 3.75 at.%-6.98 at.%, Ti is 2.06 at.%-5.31 at.%, Si is 1.01 at.%-5.5 at.%, and N is 36.52 at.%-44.26 at.%.

9. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: When depositing AlCrMoTiSiN high entropy alloy coating, when the CrMo target current is 95A, the Mo content in the coating is 4.05at.%; when the CrMo target current is 100A, the Mo content in the coating is 6.39at.%; when the CrMo target current is 110A, the Mo content in the coating is 6.98at.%; when the CrMo target current is 120A, the Mo content in the coating is 6.57at.%.

10. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: The AlCrMoTiSiN high entropy alloy coating mainly contains AlN, Mo2N, CrN and TiN crystal phases, and all the crystal phases are composed of face-centered cubic (fcc) structures.

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