A high toughness high-entropy AlCrNbSiTi composite hard coating and a preparation method thereof

Abstract

The application discloses a high-entropy AlCrNbSiTi composite hard coating with high toughness and a preparation method thereof. The composite hard coating has a gradient layer structure and is composed of an adhesion barrier layer and a tough layer which are sequentially deposited on a substrate by an arc ion plating method. The adhesion barrier layer is a pure Cr layer, and the tough layer is an AlCrNbSiTi layer. The AlCrNbSiTi layer has a composite structure in which nanocrystals and amorphous phases coexist. The AlCrNbSiTi composite hard coating with high hardness, high toughness, excellent high-temperature stability and high film-substrate adhesion can be flexibly designed and prepared according to requirements, so as to meet the required performance of cutting tools, precision molds and wear-resistant parts. The prepared coating has good adhesion and high deposition rate, the performance and production efficiency of the coating are improved, the production cost is reduced, and it is also possible to prepare a relatively thick functional coating.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering technology, specifically relating to a high-toughness, high-entropy AlCrNbSiTi composite hard coating and its preparation method. Background Technology

[0002] Hard coatings are widely used for surface protection and strengthening of machining tools, molds, and critical components, significantly improving their surface properties and extending their service life. Currently, the most common hard coatings in industry are nitride systems, including TiN, CrN, TiAlN, AlCrN, and TiSiN. These coatings are typically prepared using physical vapor deposition (PVD) or chemical vapor deposition (CVD) techniques, which improve the surface hardness and wear resistance of the substrate to a certain extent.

[0003] However, as modern manufacturing continues to develop towards high-speed cutting, dry machining, and the processing of difficult-to-machine materials (such as titanium alloys, high-temperature alloys, and hardened steel), existing hard coating systems have revealed many prominent problems in practical applications: First, there is a general contradiction between hardness and toughness; high hardness is often accompanied by increased brittleness, leading to easy crack propagation and even peeling of the coating; second, under high-temperature service conditions, the coating's high-temperature stability is insufficient, and its resistance to oxidation and softening is limited; third, the bonding strength between the coating and the substrate still needs to be improved, especially under complex stress conditions, where interface failure becomes the main cause of early damage; in addition, the wear resistance and high-temperature softening resistance of the coating are still insufficient to meet increasingly stringent processing requirements.

[0004] To overcome these performance bottlenecks, researchers have explored various optimization strategies, such as constructing multilayer structures (e.g., TiAlN / AlCrN multilayer films), designing gradient composition distributions, and adding alloying elements (e.g., V, Y, Si) to the coating. However, these approaches often only improve one specific property, making it difficult to simultaneously achieve a synergistic improvement in ultra-high hardness, good toughness, excellent high-temperature stability, and high film-substrate adhesion.

[0005] In recent years, high-entropy alloys (HEAs) have attracted widespread attention in the field of structural materials due to their four unique core effects: thermodynamic high-entropy effect, kinetic hysteresis diffusion effect, significant lattice distortion effect, and "cocktail" effect. However, applying HEAs to hard coatings, especially as wear-resistant protective coatings, still faces a series of technical challenges: how to control their microstructure to achieve a balance between high hardness and good toughness; how to ensure sufficiently high bonding strength between the coating and the substrate; and how to achieve a low-cost, high-efficiency preparation process. These are the key technical problems that this invention aims to solve. Summary of the Invention

[0006] To address the problems of existing technologies, the present invention aims to provide a high-toughness, high-entropy AlCrNbSiTi composite hard coating and its preparation method.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions.

[0008] In a first aspect, the present invention provides a high-toughness, high-entropy AlCrNbSiTi composite hard coating, wherein the composite hard coating has a gradient layer structure, and the composite hard coating is formed by sequentially depositing an adhesion barrier layer and a toughening layer on a substrate using an arc ion plating method, wherein the adhesion barrier layer is a pure Cr layer, and the toughening layer is an AlCrNbSiTi layer, wherein the AlCrNbSiTi is a composite structure in which nanocrystalline and amorphous phases coexist.

[0009] Furthermore, the thickness of the adhesion barrier layer is 10~1000 nm, and the thickness of the toughening layer is 1~20 μm. Not only can thicker coatings (>10 μm) be prepared, but AlCrNbSiTi composite hard coatings with high hardness, high toughness, excellent high-temperature stability, and high film-substrate adhesion can also be flexibly designed and prepared according to needs.

[0010] Preferably, the thickness of the adhesion barrier layer is 300-600 nm, and the thickness of the toughening layer is 1-8 μm. Coatings of this thickness exhibit good overall performance, improving coating performance and production efficiency while reducing production costs.

[0011] Secondly, the present invention provides a method for preparing a high-strength, high-entropy AlCrNbSiTi composite hard coating as described in the first aspect, wherein the coating is obtained by arc ion plating in the following steps: (1) After vacuuming, the ambient temperature is maintained at 50~500℃. In an argon atmosphere, the ambient pressure is controlled at 0.1~2Pa. A Cr target is used, the duty cycle of the Cr target arc power supply pulse is 10%~80%, and the bias voltage is -50~-150 V. A Cr adhesion barrier layer is deposited on the substrate surface. (2) Continue to introduce argon gas and adjust the ambient pressure to 1~5 Pa. Turn off the Cr target power supply and use an AlCrNbSiTi target. The duty cycle of the arc power supply pulse of the AlCrNbSiTi target is 10%~80% and the bias voltage is 0~-250 V. An AlCrNbSiTi tough layer is deposited on the surface of the Cr adhesion barrier layer to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0012] Furthermore, in steps (1) and (2), the ambient temperature is maintained at 150~300℃. The ambient temperature mainly affects the surface diffusion ability of the deposited particles and the microstructure evolution of the coating, thereby affecting the density, hardness and adhesion of the coating; depositing the adhesion barrier layer and toughening layer at a suitable ambient temperature helps to improve the hardness of the coating and its adhesion to the substrate.

[0013] Furthermore, in step (1), the ambient air pressure is 0.5~1 Pa, the Cr target arc power supply pulse duty cycle is 50%~70%, and the bias voltage is -50~-100 V. By optimizing the ambient air pressure, pulse duty cycle, and bias voltage, the adhesion and blocking effects of the pure Cr adhesion barrier layer are optimally balanced.

[0014] Furthermore, in step (2), the ambient air pressure is 3~5 Pa, the duty cycle of the arc power supply pulse of the AlCrNbSiTi target is 40%-60%, and the bias voltage is -50~-100 V. By optimizing the ambient air pressure, pulse duty cycle, and bias voltage, the high-temperature stability, toughness, hardness, and oxidation resistance of the AlCrNbSiTi toughened layer are brought into the closest balance.

[0015] Furthermore, the deposition time in step (2) is 1~60 min. The deposition time can be adjusted according to the required thickness of the AlCrNbSiTi toughening layer.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1) The synergistic effect of the gradient two-layer structure enhances the adhesion between the coating and the substrate, preventing the formation of brittle phases at the interface during high-temperature service: A pure Cr adhesion barrier layer is directly deposited on the substrate. Cr has good chemical affinity with common substrate materials (such as cemented carbide WC-Co, high-speed steel, stainless steel, etc.), and the adhesion of Cr can form strong chemical bonds, significantly improving the adhesion between the coating and the substrate. At the same time, the Cr layer can also act as a diffusion barrier, effectively preventing the diffusion of elements such as Co and Fe in the substrate to the high-entropy alloy layer, thus avoiding the formation of brittle phases at the interface during high-temperature service. Compared with traditional single-layer coatings or simple multi-layer coatings, the Cr adhesion barrier layer of this invention forms a soft / hard gradient transition with the AlCrNbSiTi toughening layer, alleviating the residual stress caused by the mismatch of thermal expansion coefficients and improving the adhesion between the coating and the substrate.

[0017] 2) The AlCrNbSiTi toughened layer exhibits superior high-temperature stability, toughness, hardness, and oxidation resistance: When the AlCrNbSiTi toughened layer is deposited using arc ion plating, the hysteretic diffusion effect of the multi-principal-element alloy and the high undercooling result in a composite structure of nanocrystalline and amorphous phases coexisting in the coating. This structure, on the one hand, imparts high hardness to the coating through the grain refinement and dislocation pinning effect of the nanocrystalline phase; on the other hand, the amorphous phase can absorb crack propagation energy, significantly improving the fracture toughness of the coating and overcoming the disadvantage of traditional hard coatings being "more brittle the harder they are." AlCrNbSiTi contains five main elements: Al, Cr, Nb, Si, and Ti. These elements have large differences in atomic size and extremely slow diffusion rates. After annealing at 1000 °C, almost no matrix elements were detected in the coating, indicating that the matrix elements could not diffuse through the Cr layer into the high-entropy layer. This allows the coating of this invention to maintain compositional stability and no significant decrease in hardness under high-temperature cutting conditions, and its oxidation resistance is superior to that of traditional TiAlN coatings.

[0018] 3) This invention employs an arc ion plating process, which has a high ionization rate and high deposition particle energy, enabling the formation of an atomic spray welding effect on the substrate surface, further enhancing the film-substrate bonding. Simultaneously, arc ion plating has a fast deposition rate (3-10 times higher than magnetron sputtering), allowing for the preparation of thicker (>10 μm) coatings, making it suitable for heavy-duty cutting tools.

[0019] 4) The method for preparing the high-strength, high-entropy AlCrNbSiTi composite hard coating provided by this invention allows for the flexible design and preparation of AlCrNbSiTi composite hard coatings with high hardness, high toughness, excellent high-temperature stability, and high film-substrate adhesion, to meet the performance requirements of cutting tools, precision molds, and wear-resistant parts. The prepared coating exhibits good adhesion and a high deposition rate, improving coating performance and production efficiency while reducing production costs. It also makes it possible to prepare thicker functional coatings. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the coating preparation device used in this invention. In the diagram: 1 represents the AlCrNbSiTi target, 2 represents the Cr target, 3 represents the AlCrNbSiTi target, 4 represents the Cr target, 5 represents the sample holder, 6 represents the heater, and 7 represents the vacuum port.

[0021] Figure 2 The image shows the surface morphology of the high-entropy AlCrNbSiTi composite hard coating of Example 1. Figure 3 This is a cross-sectional morphology diagram of the high-toughness, high-entropy AlCrNbSiTi composite hard coating of Example 1. Figure 4This is a high-resolution transmission electron microscope image of the cross-section of the tough, high-entropy AlCrNbSiTi composite hard coating of Example 1. Figure 5 The wear resistance test results are for the high-toughness, high-entropy AlCrNbSiTi composite hard coating of Example 1. Figure 6 The graph shows the changes in elemental composition of the high-toughness, high-entropy AlCrNbSiTi composite hard coating of Example 1 after annealing at different temperatures. Detailed Implementation

[0022] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0023] In the following embodiments, the following are used: Figure 1 The coating preparation apparatus shown is used for preparation. The vacuum chamber of the apparatus is enclosed by the furnace wall, and the dimensions of the vacuum chamber are 800×800×800mm. The vacuum chamber is equipped with a vacuum port 7, through which the vacuum pump unit evacuates the vacuum chamber. Heaters 6 are located at the four corners of the vacuum chamber, with a heating power of 10~30kW to improve heating efficiency. Eight arc targets are installed in four rows on the furnace wall, with four Cr targets and four AlCrNbSiTi targets respectively. The sample is mounted on a sample holder 5. This layout significantly increases the plasma density in the vacuum chamber, completely immersing the workpiece in the plasma. This greatly improves the coating deposition rate, hardness, and adhesion. Due to the optimized target structure, the magnetic field distribution is more uniform, allowing the arc to ignite evenly on the target surface, thus improving the uniformity of the coating.

[0024] To more clearly illustrate the technical solutions and advantages of the present invention, the present invention will be further explained below in conjunction with embodiments and comparative examples.

[0025] Example 1 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 200°C, then introduce argon gas, control the ambient pressure to 1 Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 60% and the bias voltage to -100V, and then deposit a Cr adhesion barrier layer with a thickness of 500nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 4 Pa. Turn off the Cr target power supply and use the AlCrNbSiTi target for deposition. Set the duty cycle of the AlCrNbSiTi target to 60% and the bias voltage to 0.5. At -100 V for 40 min, a 5 μm thick AlCrNbSiTi tough layer was deposited on the surface of the obtained Cr adhesion barrier layer. After preparation, the layer was allowed to cool naturally to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0026] The surface and cross-sectional morphology of the tough, high-entropy AlCrNbSiTi composite hard coating of this embodiment were observed using emission scanning electron microscopy (MIRA3 TESCAN). Figure 2 As can be seen, the coating surface is dense, the particle size is small, and there are no obvious defects. Figure 3 It can be seen that the coating and the substrate are tightly bonded together, with no obvious pores.

[0027] Transmission electron microscopy was used to observe the tough, high-entropy AlCrNbSiTi composite hard coating. Figure 4 The HR-TEM image of the intermediate coating shows that the AlCrNbSiTi coating also contains a crystalline phase separating the AlCrNbSiTi amorphous phase, forming a nanocrystalline / amorphous nanocomposite structure. This structure, on the one hand, imparts high hardness to the coating through the grain refinement and dislocation pinning effect of the nanocrystals, and on the other hand, the amorphous phase can absorb crack propagation energy, significantly improving the fracture toughness of the coating and overcoming the disadvantage of traditional hard coatings that are "more brittle the harder they are".

[0028] The wear resistance of the coating was tested using a tribometer. Figure 5 It can be seen that after the friction and wear test, the surface of the coating showed no obvious wear marks, and no cracks or peeling occurred, indicating that it has a good protective effect on the substrate.

[0029] The high-toughness, high-entropy AlCrNbSiTi composite hard coating of this embodiment was annealed at 700℃, 800℃, 900℃, and 1000℃, respectively, and the changes in elemental composition were subsequently analyzed. Figure 6 The compositional changes show that when the annealing temperature is between 700 and 800°C, there is almost no loss of metal elements in the coating. When the temperature increases to 1000°C, almost no matrix elements are detected in the coating, meaning that the matrix elements cannot diffuse through the Cr layer into the high-entropy layer, exhibiting excellent chemical composition stability. This indicates that the coating of the present invention can still maintain compositional stability under high-temperature conditions.

[0030] Example 2 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 150°C, then introduce argon gas, control the ambient pressure to 0.5Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 70% and the bias voltage to -100V, and then deposit a Cr adhesion barrier layer with a thickness of 500 nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 3.5 Pa. Turn off the Cr target power supply and perform deposition using an AlCrNbSiTi target. Set the duty cycle of the AlCrNbSiTi target to 60% and the bias voltage to [value missing]. At -100 V for 20 min, a 1 μm thick AlCrNbSiTi tough layer was deposited on the surface of the obtained Cr adhesion barrier layer. After preparation, the layer was allowed to cool naturally to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0031] Example 3 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 150°C, then introduce argon gas, control the ambient pressure to 1 Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 70% and the bias voltage to -50V, and then deposit a Cr adhesion barrier layer with a thickness of 500 nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 3.5 Pa. Turn off the Cr target power supply and perform deposition using an AlCrNbSiTi target. Set the duty cycle of the AlCrNbSiTi target to 60% and the bias voltage to [value missing]. At -50 V for 18 min, a 1 μm thick AlCrNbSiTi tough layer was deposited on the surface of the obtained Cr adhesion barrier layer. After preparation, the layer was allowed to cool naturally to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0032] Example 4 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 150°C, then introduce argon gas, control the ambient pressure to 0.5 Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 60% and the bias voltage to -100V, and then deposit a Cr adhesion barrier layer with a thickness of 300 nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 5 Pa. Turn off the Cr target power supply and use an AlCrNbSiTi target for deposition. Set the duty cycle of the AlCrNbSiTi target to 60% and the bias voltage to [value missing]. At -50 V for 20 min, a 1 μm thick AlCrNbSiTi tough layer was deposited on the surface of the obtained Cr adhesion barrier layer. After preparation, the layer was allowed to cool naturally to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0033] Example 5 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 300°C, then introduce argon gas, control the ambient pressure to 0.5 Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 60% and the bias voltage to -50V, and then deposit a Cr adhesion barrier layer with a thickness of 500 nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 3.5 Pa. Turn off the Cr target power supply and use the AlCrNbSiTi target for deposition. Set the duty cycle of the AlCrNbSiTi target to 60% and the bias voltage to -50 V. Deposit for 30 min to form a 3 μm thick AlCrNbSiTi tough layer on the surface of the obtained Cr adhesion barrier layer. After the preparation is completed, it is naturally cooled to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0034] Example 6 Preparation of high-entropy, tough AlCrNbSiTi composite hard coating: (1) Place the substrate in the sample holder of the coating preparation device, evacuate the device and raise the ambient temperature to 150°C, then introduce argon gas, control the ambient pressure to 0.5 Pa, turn on the bias voltage and arc power supply, set the duty cycle of the Cr target to 70% and the bias voltage to -50V, and then deposit a Cr adhesion barrier layer with a thickness of 600 nm on the surface of the substrate. (2) Continue to introduce argon gas and adjust the ambient pressure to 3 Pa. Turn off the Cr target power supply and use the AlCrNbSiTi target for deposition. Set the duty cycle of the AlCrNbSiTi target to 40% and the bias voltage to -100 V. Deposit for 50 min to form an AlCrNbSiTi tough layer with a thickness of 8 μm on the surface of the obtained Cr bonding layer. After the preparation is completed, it is naturally cooled to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

[0035] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-toughness, high-entropy AlCrNbSiTi composite hard coating, characterized in that, The composite hard coating has a gradient layer structure. The composite hard coating is formed by sequentially depositing an adhesion barrier layer and a toughening layer on the substrate using an arc ion plating method. The adhesion barrier layer is a pure Cr layer, and the toughening layer is an AlCrNbSiTi layer. The AlCrNbSiTi layer is a composite structure in which nanocrystalline and amorphous phases coexist.

2. The high-toughness, high-entropy AlCrNbSiTi composite hard coating according to claim 1, characterized in that, The thickness of the adhesion barrier layer is 10~1000 nm, and the thickness of the toughening layer is 1~20 μm.

3. The high-toughness, high-entropy AlCrNbSiTi composite hard coating according to claim 1, characterized in that, The thickness of the adhesion barrier layer is 300~600 nm, and the thickness of the toughening layer is 1~8 μm.

4. A method for preparing a high-strength, high-entropy AlCrNbSiTi composite hard coating as described in any one of claims 1 to 3, characterized in that, The composite hard coating is obtained by arc ion plating in the following steps: (1) After vacuuming, maintain the ambient temperature at 50~500℃, control the ambient pressure at 0.1~2 Pa in an argon atmosphere, use a Cr target, the duty cycle of the Cr target arc power supply pulse is 10%~80%, the bias voltage is -50~-150 V, and deposit a Cr adhesion barrier layer on the substrate surface. (2) Continue to introduce argon gas and adjust the ambient pressure to 1~5 Pa. Turn off the Cr target power supply and use an AlCrNbSiTi target. The duty cycle of the arc power supply pulse of the AlCrNbSiTi target is 10%~80% and the bias voltage is 0~-250 V. An AlCrNbSiTi tough layer is deposited on the surface of the Cr adhesion barrier layer to obtain a tough and high-entropy AlCrNbSiTi composite hard coating.

5. The preparation method according to claim 4, characterized in that: In steps (1) and (2), the ambient temperature is maintained at 150~300℃.

6. The preparation method according to claim 4, characterized in that: In step (1), the ambient air pressure is 0.5~1 Pa, the duty cycle of the Cr target arc power supply pulse is 50%~70%, and the bias voltage is -50~-100 V.

7. The preparation method according to claim 4, characterized in that: In step (2), the ambient air pressure is 3~5 Pa, the duty cycle of the arc power supply pulse of the AlCrNbSiTi target is 40%~60%, and the bias voltage is -50~-100 V.

8. The preparation method according to claim 4, characterized in that: The deposition time in step (2) is 1~60 min.

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