AlCrMoTiSiN high-entropy alloy coating with self-lubricating property and preparation process thereof

Abstract

The invention discloses an AlCrMoTiSiN high-entropy alloy coating with a self-lubricating property and a preparation process of the AlCrMoTiSiN high-entropy alloy coating, and belongs to the technical field of coatings. The AlCrMoTiSiN high-entropy alloy coating comprises the following chemical components in percentage by weight: 9.84 at.% to 33.52 at.% of Al, 19.59 at.% to 38.16 at.% of Cr, 3.75 at.% to 6.98 at.% of Mo, 2.06 at.% to 5.31 at.% of Ti, 1.01 at.% to 5.5 at.% of Si, and 36.52 at.% to 44.26 at.% of N. The invention further discloses a preparation method of the AlCrMoTiSiN high-entropy alloy coating. And depositing the high-entropy alloy coating on the substrate by adopting an arc ion plating technology. 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] This invention relates to the field of coating technology, specifically to an AlCrMoTiSiN high-entropy alloy coating with self-lubricating properties and its preparation process. Background Technology

[0002] To achieve 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. Cutting tools, as the "teeth" of CNC machine tools, play a crucial role in the machining field. Tool coating technology, as a type of surface modification technology, provides chemical and thermal barriers for the tool, avoiding direct contact between the tool and the workpiece, hindering the interdiffusion of elements between the two, and improving the tool's mechanical strength, high-temperature oxidation resistance, anti-adhesion, and anti-abrasive wear properties. This results in extended tool life, reduced production costs, and optimized surface finish.

[0003] With the development of aerospace, automotive manufacturing, military, and medical fields, the demand for difficult-to-machine materials (tungsten-molybdenum alloys, hardened steel, titanium alloys, etc.) is increasing, while the requirements for material processing efficiency and quality are becoming increasingly stringent. Because these difficult-to-machine materials have low thermal conductivity, their chips are powdery, the contact range and time between the tool and the chips are short, heat conduction is inadequate, and the cutting temperature is high. This easily leads to adhesive wear on the tool's flank face. Furthermore, the high hardness of these materials results in significant cutting forces during machining, causing severe tool damage. Applying a self-lubricating wear-resistant coating to the tool surface is an effective way to reduce tool wear. Developing advanced tool coatings with self-lubricating properties can effectively reduce friction between the workpiece and the tool, reduce cutting heat, alleviate frictional wear between the tool and workpiece, extend tool life, and reduce production costs.

[0004] AlCrTiSiN coatings possess excellent mechanical properties, high-temperature oxidation resistance, and corrosion resistance, making them widely used as high-performance coatings. However, their high coefficient of friction and poor wear resistance limit their development in high-speed machining applications. Summary of the Invention

[0005] To further improve the wear resistance of existing AlCrTiSiN coatings, the present invention aims to provide an AlCrMoTiSiN high-entropy alloy coating with self-lubricating properties and its preparation process. The process involves using arc ion plating technology to dope Mo into the AlCrTiSiN coating to form an AlCrMoTiSiN high-entropy alloy coating. Through process design and optimization of the Mo content, an AlCrMoTiSiN high-entropy alloy coating with high hardness, high wear resistance, and self-lubricating properties is prepared.

[0006] To achieve the above object, the technical solutions adopted by the present invention are as follows:

[0007] A self-lubricating AlCrMoTiSiN high-entropy alloy coating has the following chemical composition: Al 9.84 at.%-33.52 at.%, Cr 19.59 at.%-38.16 at.%, Mo 3.75 at.%-6.98 at.%, Ti 2.06 at.%-5.31 at.%, Si 1.01 at.%-5.5 at.%, and N 36.52 at.%-44.26 at.%.

[0008] Furthermore, the AlCrMoTiSiN high-entropy alloy coating contains AlN, Mo2N, CrN, and TiN crystalline phases, all of which are composed of face-centered cubic (fcc) structures.

[0009] Furthermore, the AlCrMoTiSiN high-entropy alloy coating can achieve a hardness of 26.2 GPa, a friction coefficient as low as 0.571, and a wear rate as low as 0.822 × 10⁻⁶. -9 mm 3 ·mm -1 ·N -1 .

[0010] Furthermore, the preparation process of the AlCrMoTiSiN high-entropy alloy coating with self-lubricating properties involves depositing the AlCrMoTiSiN high-entropy alloy coating on the substrate using arc ion plating technology, specifically including the following steps:

[0011] (1) Clean and dry the substrate, fix it on the sample plate, and suspend it on the rotating rack in the coating chamber. Place the metal AlCrSi target, AlTiSi target, and CrMo target on their respective cathode target positions. Evacuate to a vacuum level of 3.0 × 10⁻⁶. -3 Pa or above;

[0012] (2) The substrate was sequentially subjected to glow discharge cleaning and ion bombardment cleaning;

[0013] (3) Deposit a CrMoN transition layer for 15 min to improve the bonding strength between the working layer and the substrate;

[0014] (4) Deposition of AlCrMoTiSiN high-entropy alloy coating.

[0015] In step (2) above, the glow discharge cleaning process is as follows: the furnace is heated to 400-480℃, and then the vacuum is continued until the vacuum degree is 3×10⁻⁶. -3Above Pa, introduce Ar at a flow rate of 380-420 sccm, adjust the deposition pressure to stabilize at 2.2-2.6 Pa, pulse bias voltage -780 to -800 V, frequency 10 kHz, pulse width 6 μs, and perform glow discharge cleaning for 18-22 min.

[0016] In step (2) above, the ion bombardment cleaning process is as follows: after glow discharge cleaning, Ar with a flow rate of 180-200 sccm is introduced, the deposition pressure is adjusted to be stable at 1.1-1.2 Pa, the CrMo target is turned on, the CrMo target current is 95 A, and the frequency and pulse width are kept the same as during glow discharge cleaning. First, it is bombarded for 10 min under a pulse bias voltage of -800 V, and then bombarded for 2 min each under pulse bias voltages of -600 V, -400 V, and -200 V in sequence.

[0017] In step (3) above, the process of depositing the CrMoN transition layer is as follows: after glow discharge cleaning and ion bombardment cleaning, keep the CrMo target on, introduce Ar with a flow rate of 180-220 sccm and N2 with a flow rate of 190-210 sccm, adjust the deposition pressure to stabilize at 1.6-1.7 Pa, pulse bias voltage -100 V, frequency 50 kHz, pulse width 8 μ, and deposition time 15 min.

[0018] During step (4) above, when depositing the AlCrMoTiSiN high-entropy alloy coating, the base vacuum level is 3×10⁻⁶. -3 The deposition temperature is 400-480℃ and the deposition pressure is 2.8Pa. The AlCrSi, AlTiSi, and CrMo targets are turned on. The AlCrSi target current is 100A, the AlTiSi target current is 90A, and the CrMo target current is 90-125A (preferably 98-120A). The protective gas Ar, the reactive gas N2, and the reducing gas H2 are introduced. The deposition time is 100-150min. The CrMo target current is selected according to different experimental requirements.

[0019] In step (4) above, when depositing the AlCrMoTiSiN high-entropy alloy coating, the flow rate of Ar is 50 sccm, the flow rate of N2 is 600 sccm, and the flow rate of H2 is 10 sccm; the pulse bias voltage is -100V, the frequency of the pulse bias voltage is 50KHz, and the pulse width is 6μs.

[0020] Furthermore, the substrate is a metal (hard alloy substrate or SUS 304 stainless steel sheet) or a silicon wafer. The purity of the CrMo target is 99.8%, and the purity of other target materials is 99.95%.

[0021] Furthermore, when depositing the AlCrMoTiSiN high-entropy alloy coating, the Mo content in the coating was 4.05 at.% when the CrMo target current was 95 A; 6.39 at.% when the CrMo target current was 100 A; 6.98 at.% when the CrMo target current was 110 A; and 6.57 at.% when the CrMo target current was 120 A.

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

[0023] This invention employs arc ion plating technology to deposit AlCrMoTiSiN high-entropy alloy coatings on cemented carbide sheets, SUS 304 stainless steel, and single-crystal Si wafers.

[0024] TiN coatings exhibit superior hardness and wear resistance compared to CrN coatings, making them widely used for surface protection of cutting tools. During high-speed dry cutting, the temperature between the tool tip and workpiece can reach 800℃. Due to its susceptibility to oxidation at high temperatures, this leads to a decrease in tool cutting performance and lifespan. Diversification is one effective way to improve tool coating performance. Currently, Ti is added to AlCrTiSiN coatings to form AlCrTiSiN nanocomposite coatings. AlCrTiSiN coatings possess high hardness, toughness, and thermal stability, thus enjoying widespread application. However, during dry cutting, the high coefficient of friction and poor toughness of AlCrTiSiN coatings cause tool damage. Mo, a transition metal, is an ideal solid lubricant. Mo readily reacts with O to form a layered MoO3 lubricating phase. The low shear modulus between MoO3 layers facilitates slippage, and the weakened van der Waals forces between the interlayer crystals provide a lubrication interface. Therefore, by adjusting the CrMo target current and coordinating with other process parameters (bias voltage, gas flow rate, pressure, etc.), and by designing process conditions and optimizing the Mo element content, this invention further improves the hardness and wear resistance of the AlCrTiSiN coating without significantly reducing its mechanical and tribological properties, thus fully leveraging 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 this 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 and stable chemical properties.

[0028] 3. In the deposition of the AlCrMoTiSiN high-entropy alloy coating of this invention, the Ar flow rate is 50 sccm, the N2 flow rate is 600 sccm, and the H2 flow rate is 10 sccm; the pulse bias voltage is -100V, the pulse bias voltage frequency is 50 kHz, and the pulse width is 6 μs. H2 is used as a reducing gas, and its flow rate is controlled. An appropriate amount of H2 is used to remove residual O impurities in the vacuum chamber without affecting the coating quality (for example, excessive H2 would reduce the mechanical properties of the coating). Finally, a high-purity, high-performance AlCrMoTiSiN high-entropy alloy coating is prepared.

[0029] 4. The AlCrMoTiSiN high-entropy alloy coating of this invention has broad application prospects and is suitable for high-speed dry cutting of various difficult-to-machine materials, which can greatly improve cutting efficiency and tool service life.

[0030] 5. The AlCrMoTiSiN high-entropy alloy coating of this invention has excellent mechanical and tribological properties, and the coated tools are suitable for heavy-duty continued machining. Attached Figure Description

[0031] Figure 1 The elemental composition of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents in Example 1 is shown.

[0032] Figure 2 The XRD patterns of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents are shown in Example 1.

[0033] Figure 3 The surface morphology of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents in Example 1 is shown below; where: (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 morphology of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents in Example 1 is shown below; where: (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 AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents are shown in Example 1.

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

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

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

[0039] Figure 9 The friction coefficient and wear rate of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents are shown in Example 1.

[0040] Figure 10 The wear track morphology of AlCrMoTiSiN high-entropy alloy coatings prepared by arc ion plating technology under different CrMo target currents in Example 1 is shown below; where: (a) target current 0A; (b) target current 95A; (c) target current 100A; (d) target current 110A; (e) target current 120A. Detailed Implementation

[0041] The present invention will be further described in detail below through embodiments.

[0042] Existing AlCrTiSiN coatings exhibit poor wear resistance. To further improve their friction performance without reducing their hardness and other properties, this invention optimizes the coating's service performance by doping with the lubricating phase Mo. The content of the lubricating phase has a significant impact on the coating. Extensive experimental research shows that if the lubricating phase content is low, the supply cannot meet the consumption during friction and wear, resulting in insignificant lubrication; when the lubricating phase content is high, the material's mechanical strength and other properties decrease; only when the lubricating phase content is moderate can an effective lubricating film be formed, reducing the coefficient of friction.

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

[0044] Example 1:

[0045] This example demonstrates the preparation of AlCrMoTiSiN high-entropy alloy coatings with different Mo contents.

[0046] In this embodiment, an AlCrMoTiSiN high-entropy alloy coating is deposited on a single-crystal Si wafer (30mm×30mm×0.67mm), a cemented carbide wafer (25mm×25mm×3.0mm), and a stainless steel wafer (35mm×35mm×1.0mm) using fully automated arc ion plating technology. The specific operation steps are as follows:

[0047] (1) Substrate Pretreatment: After polishing the cemented carbide substrate, it is placed in an ultrasonic cleaner along with pre-prepared single-crystal Si wafers and 304 stainless steel sheets. The substrates are then ultrasonically cleaned with acetone and alcohol for 20 minutes each, followed by drying with high-purity N2 (99.99%). The substrate is fixed to the sample plate. After the vacuum chamber is vented, the vacuum chamber door is opened, and the sample plate is fixed to the rotating frame inside the coating chamber with wire. The metal AlCrSi target, AlTiSi target, and CrMo target are placed on their respective cathode target positions. The position of the sample plate is adjusted so that the substrate faces the target surface to prevent uneven coating due to different deposition distances during the deposition process. The vacuum chamber is checked for any foreign matter residue, and the furnace door is closed.

[0048] (2) Vacuuming: Since the molecular pump cannot operate when the pressure inside the vacuum chamber exceeds 4.0 Pa, the vacuuming process is divided into two steps. First, vacuuming begins at atmospheric pressure using a TRP-90 coarse pump. When the vacuum level is roughly reduced to 4.0 Pa, the mechanical pump and molecular pump are activated to accelerate the molecular pump. Once acceleration is complete and the vacuum level drops below 4.0 Pa, the fine pump valve is opened to further evacuate the vacuum chamber until the pressure reaches 3.0 × 10⁻⁶ Pa. -3 Once the pressure exceeds a certain level (Pa), turn on the heating source to heat the vacuum chamber. Set the final temperature to 460℃ and the alarm temperature to 465℃. During heating, keep the rotating frame rotating clockwise at 40Hz to ensure uniform heating of the substrate. Continue heating until the temperature stabilizes at 460℃ and the vacuum level reaches 3.0 × 10⁻⁶. -3 Pa or above.

[0049] (3) Glow discharge cleaning vacuum chamber: When the temperature and vacuum level in the vacuum chamber meet the requirements, Ar400sccm is introduced into the vacuum chamber, the pressure in the vacuum chamber is adjusted to stabilize at 2.4Pa, the pulse bias voltage is -800V, the frequency is 10KHz, the pulse width is 6μs, and the deposition time is 20min. The purpose is to remove impurities and oxide layers from the substrate surface.

[0050] (4) Bombardment cleaning of target surface: Introduce Ar 200sccm, adjust the deposition pressure to stabilize at 1.2Pa, turn on CrMo target, CrMo target current is 95A, keep the frequency and pulse width unchanged (frequency 10KHz, pulse width 6μ), bombard for 10min under -800V pulse bias voltage, and then bombard for 2min each under -600V, -400V and -200V pulse bias voltages in sequence. The purpose is to remove impurities and oxide layer on the target surface.

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

[0052] (6) Deposition of AlCrMoTiSiN high-entropy alloy coating: Ar 50 sccm, N2 600 sccm and H2 10 sccm were introduced, the deposition pressure was adjusted to stabilize at 2.8 Pa, the pulse bias voltage was -100 V, the frequency was 50 KHz and the pulse width was 6 μs. The target currents of CrMo for different samples were set to 0 A, 95 A, 100 A, 110 A and 120 A, the target current of AlCrSi was 100 A and the target current of AlTiSi was 90 A, and the deposition time was 120 min.

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

[0054] The phase composition of the coating was analyzed using X-ray diffraction (XRD). Data was acquired using a stepped scanning method, with Cu target Kα characteristic spectral line (λ = 0.154056 nm) as the incident X-ray. The tube voltage was 40 kV, the tube current was 40 mA, the diffraction angle (2θ) scanning range was 20°–80°, the scanning step size was 0.02°, and the counting time per step was 0.2 s. The surface and cross-sectional morphology of the coating were observed using an S4800 field emission scanning electron microscope (SEM), and the chemical composition of the coating was analyzed using an electron probe microanalysis (EPMA, Shimadzu, EPMA1600).

[0055] The hardness and elastic modulus of the coating were tested using a nanoindenter (Anton Paar, TTX-NHT-3). To eliminate the influence of the matrix effect on the measurement results, the indentation depth of the needle tip was ensured to be no more than 1 / 10 of the coating thickness, and 15 points were measured and the average value was taken. The bonding strength between the coating and the SUS 304 stainless steel substrate was measured using a scratch tester (Anton Paar RST-3). The diamond needle tip diameter was 200 μm, and the parameters were as follows: loading speed 6 mm / min; scratch length 3 mm; set load 100 N. The experimental data were recorded in real time by computer.

[0056] The coefficient of friction was tested on a tribological testing machine (Anton Paar THT). Al₂O₃ balls with a diameter of 6 mm (hardness 22±1 GPa) were used for the friction pair. The sliding linear velocity was 0.1 m / s, the normal load was 4 N, the rotation radius was 6 mm, and the sliding distance was 100 m. The friction experiment was conducted at room temperature (22±3℃) and humidity (30%). Each sample was tested three times. The coating wear rate W was calculated using the formula W=V / (F×S) (where V is the wear volume, F is the normal load, and S is the sliding distance). Furthermore, the morphology of the coating after wear was observed using a super depth-of-field microscope (VHX-1000C, Keyence).

[0057] Figure 1 The elemental composition of AlCrMoTiSiN high-entropy alloy coatings prepared for different CrMo target currents is shown in the figure. As the CrMo target current increases, the Cr content increases from 19.59 at.% to 38.16 at.% and then decreases to 35.58 at.%, while the Al content decreases from 33.52 at.% to 9.84 at.%, and the Mo content increases from 0 to 6.98 at.% and then decreases to 6.57 at.%. The study indicates that the difference in Al and Cr content is related to the average valence state of the target elements in the plasma; elements with higher melting points have higher 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 influence of a negative bias power supply, Al exhibits negative segregation, while Cr exhibits positive segregation. With the increase of the CrMo target current, more Cr and Mo elements are sputtered, increasing the total number of atoms in the vacuum cavity, leading to a decrease in the relative atomic number of Al, Si, and Ti elements in the coating. The study found that the bond energy of Mo2N is 228.3 eV, which is much lower than the bond energy of AlN and CrN. During the coating preparation process, the ionized nitrogen element combines with the Mo element to form Mo2N. More Mo is sputtered out and combines with the N element, resulting in an increase in the N element content.

[0058] Figure 2XRD patterns of AlCrMoTiSiN high-entropy alloy coatings prepared for different CrMo target currents are shown. As can be seen from the figures, the coatings are mainly composed of AlN, Mo2N, CrN, and TiN crystalline phases, and all coatings exhibit a face-centered cubic (fcc) structure. No oxides were detected in the coatings, indicating that residual O elements in the vacuum chamber have been completely removed. No Si content was detected in the coatings either, indicating that silicon exists in an amorphous or solid-solution-strengthened state. With increasing CrMo target current and the increase in Mo content, more Mo atoms replace the Al, Cr, and Ti positions in the AlCrN and AlTiN lattices, forming (Al,Cr,Mo)N and (Al,Ti,Mo)N substitutional solid solutions, leading to lattice distortion, broadening of diffraction peaks, and grain refinement. As the CrMo target current increases, more Mo atoms replace more Cr atoms. The replaced Cr atoms combine with N to form fcc-CrN phase diffraction peaks. The intensity of the fcc-CrN phase diffraction peaks increases along the (200) and (311) crystal planes. Preferred 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 of minimum strain energy. At this time, there is a certain internal stress, which 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 for different CrMo target currents is shown in the figures. As can be seen from the figures, all coating surfaces show no obvious cracks, but defects such as large particles, droplets, and pits left by droplet detachment are present. These defects are caused by the arc ion plating technology. The working principle of arc ion plating is that during arc discharge, a large number of cathode arc spots appear on the cathode target surface. The movement of these arc spots on the target surface generates arc heat, and the target material evaporates to produce ions. Due to the excessively high arc heat temperature, some areas of the target surface melt, forming particulate liquid deposits on the coating surface. Without Mo doping, the coating surface shows large-diameter particles and voids formed by detachment. However, with Mo doping, the particle size of the coating surface becomes smaller. When the CrMo target current is 100A, the coating surface particles are smaller and fewer in number, resulting in a denser structure. Increasing the CrMo target current promotes enhanced particle surface migration, accelerates the crystallization process of the coating, increases the nucleation rate of crystals, and thus refines the grains. Grain refinement leads to a denser coating surface. Further increasing the CrMo target current resulted in a large number of voids on the coating surface. This is because the increase in target current increases the plasma density, causing solid solution to occur before the ions reach the substrate, resulting in pitted defects on the surface.

[0060] Figure 4The cross-sectional morphology of AlCrMoTiSiN high-entropy alloy coatings prepared for different CrMo target currents is shown in the figure. As can be seen from the figure, all coatings exhibit a dense columnar structure and grow perpendicular to the substrate. The cross-section of the AlCrMoTiSiN high-entropy alloy coating is relatively smooth, exhibiting a columnar crystal structure with regular arrangement, consistent with the surface morphology image. With increasing CrMo target current, the coating thickness initially decreases and then increases. When the CrMo target current is 100 A, the coating structure is the densest, with the fewest large particles on the surface. This is because during CrMo target sputtering, the particles have strong migration ability and high crystallinity, leading to grain growth and a denser coating structure. Further increases in the CrMo target current may be due to excessively high target current, causing particles to fail to migrate effectively upon reaching the substrate surface and instead be locked into nucleation regions by other particles, promoting grain recrystallization. Simultaneously, combined with the XRD pattern, the decrease in N content reduces the specific gravity of the amorphous phase of the coating, inhibiting the encapsulation of nanocrystals by amorphous particles, resulting in an increase in columnar crystal size.

[0061] Figure 5 The hardness and elastic modulus of AlCrMoTiSiN high-entropy alloy coatings prepared for different CrMo target currents were studied. Hardness represents the coating's resistance to deformation, while elastic modulus refers to the stress-to-strain ratio within the elastic deformation range. With increasing Mo content, both the hardness and elastic modulus of the coating initially increased and then decreased. When the CrMo target current was 100 A, both the hardness and elastic modulus reached their maximum values ​​of 26.192 GPa and 424.003 GPa, respectively. According to the solid solution strengthening mechanism, Mo atoms in the coating replace some Al and Cr atoms in the (Al,Cr)N lattice, forming an (Al,Cr,Mo)N solid solution phase. Due to the difference in atomic radii, lattice distortion occurs, increasing the hardness of the coating by increasing the number of grain boundary dislocations. As the CrMo target current further increases, the hardness of the coating decreases, possibly due to an increase in the Mo2N soft phase, which reduces the coating's hardness. Furthermore, according to the Hall-Page theory, smaller grains correspond to an increase in the number of grains per unit area, thereby improving the coating's strength. Conversely, larger grain sizes have a negative impact on the hardness of the coating.

[0062] Figure 6 H / E and H2 of AlCrMoTiSiN high-entropy alloy coatings with different Mo contents 3 / E *2 Figure. H / E characterizes the coating's resistance to elastic deformation, H 3 / E *2 Characterizes the coating's resistance to plastic deformation. H / E and H 3 / E *2 The higher the value, the better the toughness of the coating. With increasing 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 H values ​​of the coating are...3 / E *2 The maximum values ​​were reached, at 0.062 and 0.083 GPa respectively, indicating that the coating exhibited optimal resistance to elastic strain failure and plastic deformation, demonstrating that Mo enhances the coating's hardness and toughness. With increasing CrMo target current, H / E and H... 3 / E *2 The decreasing trend is attributed to the fact that excessively high target current increases the number of large droplets on the coating surface, resulting in a loose coating structure and thus reducing the characteristic value of the coating.

[0063] Critical load represents the magnitude of the external force required for the coating to detach from the substrate, i.e., the coating adhesion force. Figure 7 and Figure 8 The critical load and scratch morphology of AlCrMoTiSiN high-entropy alloy coatings with different Mo contents are shown in the figure. As can be seen from the figure, the adhesion of the coating first increases and then decreases with the increase of CrMo target current. When the CrMo target current is 0A, the adhesion of the coating is the worst at 64.91N, and the incorporation of Mo element improves the adhesion of the coating. When the CrMo target current is 110(2)A, the adhesion of the coating is the largest at 81.32N, which is due to the continuous linear increase of target current and the increase of heat flux density. At this time, high-energy particles directly bombard the substrate surface, causing the atoms on the surface to generate high temperature and high pressure in the nearby micro-region, thereby improving the adhesion between the coating and the substrate.

[0064] Figure 9 The friction coefficient and wear rate of AlCrMoTiSiN high-entropy alloy coatings with different CrMo target currents are shown. With increasing CrMo target current, both the friction coefficient and wear rate show a trend of first decreasing and then increasing. At a CrMo target current of 100 A, both the friction coefficient and wear rate reach their minimum values, which are 0.571 and 0.822 × 10⁻⁶, respectively. -9 mm 3 ·N -1 ·mm -1 The addition of Mo causes the AlCrMoTiSiN high-entropy alloy coating to generate a large amount of MoO3 lubricating phase during friction, transforming the direct contact between the wear pairs into indirect contact with a lubricating film, reducing interfacial friction and lowering the coefficient of friction. At this point, the coating exhibits optimal wear resistance. However, with further increases in the CrMo target current, the coating's hardness and H / E ratio show a decreasing trend, failing to guarantee wear resistance, thus increasing both the coefficient of friction and wear rate. For the AlCrTiSiN coating, the AlCrMoTiSiN high-entropy alloy coating shows a significant decrease in both the coefficient of friction and wear rate, indicating that the addition of Mo improves the tribological properties of the coating.

[0065] Figure 10The figure shows the three-dimensional wear track morphology of AlCrMoTiSiN high-entropy alloy coatings with different CrMo target currents after room temperature friction experiments. As can be seen from the figure, all five coatings exhibited varying degrees of wear. The AlCrTiSiN coating showed the most severe wear. Based on the surface morphology, a small number of large particles were present on the coating surface. During friction, the friction pair compressed the coating surface, causing some particles to peel off. Continued friction resulted in obvious banded micro-grooves, indicating abrasive wear. With increasing CrMo target current, the wear on the coating surface changed from abrasive wear to adhesive wear. The contact between the friction pair and the coating generated a lubricating phase to resist relative sliding. When the CrMo target current was 100 A, the coating showed the least wear, the narrowest wear track, the lowest coefficient of friction, and the least damage to the coating. No abrasive wear was observed at the wear track, indicating the best wear performance of the coating.

[0066] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. An AlCrMoTiSiN high entropy alloy coating with self-lubricating properties, characterized in that: The chemical composition of the AlCrMoTiSiN high entropy alloy coating is: 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.%.

2. The AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: The AlCrMoTiSiN high entropy alloy coating comprises AlN, Mo2N, CrN and TiN crystal phases, and all the crystal phases are composed of a face-centered cubic (fcc) structure.

3. The AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 1, characterized in that: The hardness of the AlCrMoTiSiN high entropy alloy coating can reach 26.2 GPa, the friction coefficient of the coating can be as low as 0.571, and the wear rate of the coating can be as low as 0.822×10 -9 mm 3 mm -1 ·N -1 .

4. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to any one of claims 1 to 3, 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.

5. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 4, 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.

6. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating function according to claim 4, 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.

7. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 4, 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.

8. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 4, 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.

9. The process for preparing the AlCrMoTiSiN high entropy alloy coating with self-lubricating properties according to claim 4, 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.

10. 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%; 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.%.

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