Tough low-stress super-thick AlTiN-based coating as well as preparation method and application thereof

Abstract

The invention provides a tough low-stress super-thick AlTiN-based coating as well as a preparation method and application thereof, and belongs to the technical field of surface engineering and functional coatings. The coating is obtained through deposition of a high-power pulse magnetron sputtering technology, and the film-substrate binding force is enhanced through glow cleaning and ion source cleaning pretreatment in the preparation process; by utilizing the advantage of uniform and controllable energy of a high-power pulse magnetron sputtering technology, a high-density plasma region is constructed between a target material and a substrate, so that not only can an extremely high deposition rate be obtained, but also the residual stress of the coating is controllable. The prepared coating is excellent in mechanical property, the nanometer hardness is larger than or equal to 30 GPa, the binding force is larger than 100 N, the residual stress under the thickness of 21 micrometers is only-4.5 GPa, and the cutting edge of the prepared coating tool is sharp and smooth. The method can be widely applied to high-speed heavy-load cutting tools, molds and other wear-resistant parts, and the service life can be remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of surface engineering and functional coating technology, and particularly relates to a strong, tough, integrated, low-stress ultra-thick AlTiN-based coating, its preparation method, and its application. Background Technology

[0002] As modern manufacturing moves towards higher speeds, higher efficiency, and dry / near-dry machining, higher demands are placed on the service life and machining stability of cutting tools. AlTiN coatings, due to their excellent high-temperature hardness, oxidation resistance, and wear resistance, have become one of the commonly used PVD (physical vapor deposition) coatings for high-performance cutting tools. Studies have shown that under heavy-load cutting conditions, tool life has an approximately linear relationship with coating thickness; thick coatings (>10 μm) can effectively slow down the wear process and provide more durable thermal and mechanical protection.

[0003] However, traditional PVD technologies (such as arc ion plating (AIP)) face several bottlenecks in preparing thick coatings: on the one hand, as the deposition thickness increases, residual stress accumulates, easily leading to coating cracking or peeling; on the other hand, the arc process is accompanied by the generation of a large number of macroparticles, causing surface defects, affecting cutting edge accuracy, and becoming a source of crack initiation. Furthermore, Al is easily lost during arc sputtering due to resputtering, making it difficult to achieve high Al content doping and limiting further improvements in its oxidation resistance. While chemical vapor deposition (CVD) can obtain thicker coatings, it is usually accompanied by high tensile stress and high deposition temperatures (>800℃), easily leading to substrate degradation and making it unsuitable for tool steels or precision parts with low tempering temperatures.

[0004] In recent years, high-power pulsed magnetron sputtering (HiPIMS) technology has attracted widespread attention due to its extremely high metal ion ionization rate (up to 70% or more), controllable energy input, and good film uniformity. Existing research has attempted to use HiPIMS to prepare TiAlN-like coatings. For example, Cemecon achieved a 12μm thick TiAlN coating with low residual stress by simultaneously modulating the bias voltage between the HiPIMS cathode and the substrate, significantly improving the durability of milling inserts. Kobe Steel in Japan has also developed an SFC evaporation source for preparing low-stress, thick coatings. In my country, not only are equipment procurement and process licensing costs high, but the ability to independently optimize and iteratively innovate processes is also severely restricted.

[0005] Furthermore, existing technologies still face the following challenges: how to suppress the accumulation of residual stress while increasing coating thickness; how to avoid surface roughening caused by grain coarsening and columnar crystal growth; and how to reconcile the contradiction between hardness and toughness to achieve "integrated strength and toughness." Therefore, developing independently controllable thick coating preparation technology is crucial. This is not only a key measure to break the monopoly and reduce dependence on imported technology, but also a strategic need to enhance the core competitiveness of my country's high-end manufacturing industry and ensure the security of the industrial supply chain. Therefore, there is an urgent need for a method to prepare AlTiN-based thick coatings that can maintain high hardness and good bonding strength while possessing low residual stress, high density, fine-grained structure, and excellent toughness. This invention is proposed against this background, aiming to solve the above-mentioned key technical problems and provide a new generation of high-performance protective coating solutions for high-end manufacturing equipment. Summary of the Invention

[0006] To address the problems of high residual stress, decreased bonding strength, numerous surface defects, and insufficient toughness in existing AlTiN-based coatings during the thickening process, this invention proposes a strong and tough integrated low-stress ultra-thick AlTiN-based coating, its preparation method, and its application.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a strong, tough, integrated, low-stress, ultra-thick AlTiN-based coating, which is deposited on a substrate and has a thickness of 5–21 μm. The coating consists of a c-(Al,Ti)N main phase and a dispersed w-AlN secondary phase, wherein the atomic percentages of Al, Ti, and N are (35.0±5.0)%, (15±5)%, and (50±5.0)%, respectively. The coating has a nanocrystalline structure, and the (111) plane is preferentially oriented.

[0008] Furthermore, the thickness of the coating is 9.4–21 μm.

[0009] Furthermore, the surface roughness of the coating is ≤0.2μm, with no visible droplets or macroscopic defects.

[0010] Furthermore, the coating has a nanohardness ≥30GPa, an adhesion force to the substrate ≥100N, and a residual stress of -2 to -6GPa.

[0011] This invention also provides a method for preparing the above-mentioned strong and tough monolithic low-stress ultra-thick AlTiN-based coating, which employs high-power pulsed magnetron sputtering (HiPIMS) technology and includes the following steps: (1) Place the substrate in a vacuum chamber and evacuate to a vacuum level of 4-7 × 10⁻⁶. -3Pa, heated to 250-500℃; Ar (argon) gas was introduced for glow discharge cleaning and ion bombardment activation treatment; (2) Maintain the chamber temperature at 350-450℃, introduce a mixture of Ar and N2 gas, and the total pressure of the chamber is 0.4-1.0 Pa; turn on the planar target containing Al and Ti elements, and use high-power pulsed magnetron sputtering technology to deposit and prepare a strong and tough integrated low-stress ultra-thick AlTiN base coating.

[0012] Furthermore, step (1) specifically includes: The deposition chamber is heated to 250–500°C and then evacuated to a vacuum level of 4–7 × 10⁻⁶. -3 Pa; Introduce 200-300 sccm of Ar gas, adjust the chamber pressure to 2.0 Pa, and apply a negative bias voltage of -800 to -1000 V to the substrate for glow cleaning for 15-30 min. Then, adjust the chamber temperature to 350℃, the Ar gas flow rate to 70-100 sccm, and the chamber pressure to 0.5 Pa. Turn on the ion source or Cr target to perform ion bombardment activation treatment on the substrate surface. The substrate negative bias voltage is -800 to -1000 V, and the treatment lasts for 3-10 minutes.

[0013] Furthermore, in step (2), N2 accounts for 25% to 60% of the total pressure of the mixed gas.

[0014] Further, in step (2), the process parameters of the high-power pulsed magnetron sputtering are: deposition time of 1 to 4 hours, target power of 3 to 15 kW, peak current of 300 to 600 A, pulse frequency of 200 to 500 Hz, and pulse width of 50 to 250 μs.

[0015] Furthermore, in step (2), the distance between the substrate and the target during deposition is 8 to 12 cm, and the negative bias voltage applied to the substrate is -50 to -300 V.

[0016] Furthermore, the planar target material is an AlTi alloy target, wherein the atomic ratio of Al to Ti is 67:33.

[0017] The present invention also provides an application of the above-described strong and tough integrated low-stress ultra-thick AlTiN-based coating or the coating prepared according to the above method, wherein the coating is applied to the surface of high-speed heavy-duty cutting tools, molds or wear-resistant parts.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects: (1) The ultra-thick AlTiN-based coating of the present invention can be deposited with controllable thickness in the range of 5 to 21 μm to obtain a compressive stress state with residual stress ≤ -6 GPa; improve the coating bonding strength to Lc2 (critical load) ≥ 100 N, obtain nanocrystalline growth with near glass phase, and at the same time ensure that the prepared coated tool has a sharp and smooth cutting edge; achieve high Al content and improve oxidation resistance; construct w-AlN with c-(Al,Ti)N+ dispersed distribution to match the coating strength and toughness; significantly extend the tool life and meet the high-efficiency cutting requirements of difficult-to-machine materials (such as titanium alloys and high-temperature alloys).

[0019] (2) This invention utilizes high-power pulsed magnetron sputtering technology, which allows for controllable particle deposition. It constructs a high-density plasma region between the target and the substrate, achieving an effect similar to metal ion irradiation. This results in a high deposition rate while avoiding the increase in residual compressive stress caused by lattice distortion and defects resulting from gas ion implantation. Furthermore, enhanced ion bombardment promotes the diffusion and migration of film-forming ions, and also facilitates the relaxation phenomenon of the film and the diffusion and annihilation of defects during the deposition process, thereby releasing the film stress. Therefore, even at large thicknesses, the film can still be made dense and have low residual stress. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The diagram shows the deposition of the AlTiN coating in Example 1 (left) and the current and voltage waveforms when a single HiPIMS power supply is in operation (right). Figure 2 The results of nanoscale hardness, elastic modulus, H / E and residual stress tests for Comparative Examples 1-4 and Examples 1-2 are shown. Figure 3 The coating surface and cross-sectional SEM images, thickness, and EDS composition analysis results of Examples 1(a), 2(b), 1(c), 2(d), 3(e), and 4(f) are shown. Figure 4 The results of GIXRD tests for Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figure 5 The scratch test results are for Example 1 and each comparative example; Figure 6 The specific wear rate and average friction coefficient of Examples 1 and 2 and Comparative Examples 1 and 2; Figure 7 The wear track cross-sectional curves are for Examples 1 and 2 and Comparative Examples 1 and 2; Figure 8SEM images of the cutting edge and face of the coated cutting tools in Examples 1 and 2 and Comparative Examples 1 and 3; Figure 9 Three-dimensional morphology images of the coated cutting tools prepared in Examples 1 and 2 and Comparative Examples 1 and 3; Figure 10 The microscopic cutting edge radius values ​​are for the coated cutting tools and uncoated bare cutting tools in Examples 1 and 2 and Comparative Examples 1 and 3. Detailed Implementation

[0021] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0022] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0023] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0024] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0025] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0026] This invention provides a tough, integrated, low-stress, ultra-thick AlTiN-based coating, which is deposited on a substrate and has a thickness of 5–21 μm. The coating consists of a c-(Al,Ti)N main phase and a dispersed w-AlN secondary phase, wherein the atomic percentages of Al, Ti, and N are (35.0±5.0)%, (15±5)%, and (50±5.0)%, respectively. The coating has a nanocrystalline structure with an average grain size of ≤20nm and the (111) plane is preferentially oriented.

[0027] In a preferred embodiment of the present invention, the thickness of the prepared coating is 9.4–21 μm.

[0028] In a preferred embodiment of the present invention, the surface roughness of the prepared coating is ≤0.2μm, and there are no visible droplets or macroscopic defects.

[0029] In a preferred embodiment of the present invention, the prepared coating has a nanohardness ≥30GPa, an adhesion force to the substrate ≥100N, and a residual stress of -2 to -6GPa.

[0030] The coating prepared in this embodiment of the invention consists of a c-(Al,Ti)N main phase and a dispersed w-AlN secondary phase, combined with a nanocrystalline structure with an average grain size ≤20nm. This not only improves hardness (>32GPa) through nanocrystal refinement but also improves toughness through the synergistic effect of the two phases, thus resolving the contradiction of "hardness and toughness being mutually exclusive" in traditional thick coatings (>10μm) and meeting the impact resistance requirements in high-speed and heavy-load scenarios. It achieves high Al content and high hardness in sputtered coatings, significantly improving the high-temperature oxidation resistance of the coating and making it suitable for high-temperature working conditions in dry / near-dry processing. The coating is clearly defined as a dense nanocrystalline structure with a preferred orientation of (111) plane. Compared with traditional columnar crystal coatings, it can reduce stress concentration between grains. Combined with the two-phase structure, the coating can still control residual stress (≤-6GPa) in the ultra-thickness range of 5-21μm, avoiding cracking or peeling (the residual stress in Comparative Example 3 reached -13.4GPa when the thickness was 13.8μm). This invention achieves a thickness coverage of 5–21 μm, meeting the requirements of heavy-duty cutting for "long-lasting thermal barrier and mechanical protection" and is suitable for cutting scenarios of difficult-to-machine materials such as titanium alloys and high-temperature alloys.

[0031] This invention also provides a method for preparing the above-mentioned strong and tough monolithic low-stress ultra-thick AlTiN-based coating, which employs high-power pulsed magnetron sputtering (HiPIMS) technology and includes the following steps: (1) Place the substrate in a vacuum chamber and evacuate to a vacuum level of 4-7 × 10⁻⁶. -3 Pa, heated to 250-500℃; Ar (argon) gas was introduced for glow discharge cleaning and ion bombardment activation treatment; (2) Maintain the chamber temperature at 350-450℃, introduce a mixture of Ar and N2 gas, and the total pressure of the chamber is 0.4-1.0 Pa; turn on the planar target containing Al and Ti elements, and use high-power pulsed magnetron sputtering technology to deposit and prepare a strong and tough integrated low-stress ultra-thick AlTiN base coating.

[0032] More specifically, a method for preparing the above-mentioned strong and tough integrated low-stress ultra-thick AlTiN-based coating in an embodiment of the present invention includes the following steps: S1. Place the substrate in a vacuum chamber and evacuate to a vacuum level of 4–7 × 10⁻⁶. -3 Pa (preferably 7×10) -3 Once the required vacuum level in the chamber is reached, 200–300 sccm (preferably 300 sccm) of Ar gas is introduced to perform glow discharge cleaning on the sample. At this time, the pressure inside the chamber is 2.0 Pa. The negative bias voltage of the substrate is adjusted to -800 to -1000V (preferably -1000V) for glow discharge cleaning. The working time is 15–30 min (preferably 15 min). S2. Adjust the working temperature of the chamber to 350℃, adjust the Ar gas flow rate to 70~100sccm (preferably 100sccm), set the gas pressure of the deposition chamber to 0.5Pa, turn on the ion source or Cr target to perform ion bombardment activation treatment on the substrate surface, set the target current to 80A, adjust the substrate negative bias voltage to -800V, and work for 3min. S3. Move the substrate to the sputtering target, turn on the HiPIMS power supply equipped with an AlTi alloy target (Al to Ti atomic ratio of 67:33), and introduce a mixture of N2 and Ar gas (N2 accounts for 25%~60% of the total pressure of the mixture) into the vacuum chamber, controlling the chamber pressure to 0.7 Pa; the distance between the substrate and the target during deposition is 8~12 cm, the bias voltage of the substrate is set to -50~-300V (preferably -100V); the HiPIMS power supply power is set to 3~15kW (preferably 4kW), the pulse frequency is set to 200~500Hz (preferably 300Hz), the pulse width is set to 50~250μs (preferably 100μs), and the deposition time is 1~4h (preferably 1h), to obtain a strong and tough integrated low-stress ultra-thick AlTiN base coating.

[0033] Compared to the droplet defects and stress accumulation of arc ion plating (AIP) and the substrate degradation caused by the high temperature (>800℃) of chemical vapor deposition (CVD), this invention employs HiPIMS technology. Leveraging its high ionization rate (>70%) and controllable energy, a high-density plasma region is constructed between the target and the substrate, achieving a high deposition rate (5-21 μm deposition in 1-4 hours) while avoiding droplet formation and significant residual stress accumulation. The combined pretreatment of glow discharge cleaning and ion source etching effectively removes contaminants and oxide layers from the substrate surface, activating the surface and laying the foundation for subsequent deposition, resulting in an adhesion strength ≥100N. Parameters such as temperature, pressure, and gas ratios throughout the preparation process can be precisely controlled, ensuring consistency in coating composition (Al, Ti, N ratio), structure (nanocrystalline + dual-phase), and performance.

[0034] This invention also provides an application of the above-described strong and tough integrated low-stress ultra-thick AlTiN-based coating or the coating prepared according to the above method, wherein the coating is applied to the surface of high-speed heavy-duty cutting tools, molds or wear-resistant parts.

[0035] In the embodiments of this invention, room temperature refers to "25±2℃".

[0036] In this embodiment of the invention, the substrate used is a tool substrate with cemented carbide grade YG8.

[0037] The technical solution of the present invention will be further illustrated by the following embodiments.

[0038] Example 1 A method for preparing a strong, tough, integrated, low-stress, ultra-thick AlTiN-based coating specifically includes the following steps: S1. Place the tool substrate in the vacuum chamber and evacuate to 7×10⁻⁶. -3 Pa, once the vacuum level in the chamber reaches the required level, 300 sccm of Ar gas is introduced to perform glow discharge cleaning on the sample. At this time, the pressure in the chamber is 2.0 Pa. The negative bias voltage of the substrate is adjusted to -1000V to perform glow discharge cleaning, and the working time is 15 minutes. S2. Adjust the working temperature of the chamber to 350℃, the Ar gas flow rate to 100sccm, the gas pressure of the deposition chamber to 0.5Pa, perform ion bombardment activation treatment on the substrate surface, the target current is 80A, adjust the substrate negative bias voltage to -800V, and the working time is 3min. S3. Move the substrate to the sputtering target, turn on the HiPIMS power supply equipped with the AlTi alloy target (Al to Ti atomic ratio of 67:33), and introduce a mixture of N2 and Ar gas (N2 accounting for 55% of the total gas pressure) into the vacuum chamber, controlling the chamber pressure to 0.7 Pa; the distance between the substrate and the target during deposition is 8 cm, the substrate bias voltage is set to -100 V; the HiPIMS power supply power is set to 4 kW, the pulse frequency to 300 Hz, the peak current to 336 A, the pulse width to 100 μs, and the deposition time to 1 h. At this time, the average power density on the surface of the magnetron sputtering target is 13 W / cm². 2 The peak power density on the surface of the magnetron-controlled planar target is 1.275 kW / cm². 2 The peak current of the target material can reach 336A; S4. After deposition, wait for the temperature to drop to room temperature, remove the substrate, and obtain a tough, integrated, low-stress, ultra-thick AlTiN base coating with a thickness of 9.4 μm deposited on the substrate surface.

[0039] Example 2 Same as Example 1, except that in step S3, the deposition time is 4 hours, resulting in a tough, integrated, low-stress, ultra-thick AlTiN base coating with a thickness of 21 μm deposited on the substrate surface.

[0040] Comparative Example 1 The preparation of AlTiN coatings using arc ion plating specifically includes the following steps: S1. Place the tool substrate in the vacuum chamber and evacuate the base vacuum to 7×10⁻⁶. -3 Pa, once the chamber vacuum reaches the required level, introduce 300 sccm of Ar gas to perform glow discharge cleaning on the sample. At this time, the chamber pressure is 2.0 Pa. Adjust the substrate negative bias to -1000 V and work for 15 minutes. S2. Adjust the working temperature of the chamber to 350℃, use cathode arc evaporation to bombard the substrate with a Cr target, the distance between the substrate and the target is 25cm, the sample rotates in front of the target during the deposition process, the Ar gas flow rate is 100sccm, the gas pressure in the deposition chamber is 0.7Pa, the target current is 80A, adjust the substrate negative bias to -800V, and the working time is 5min; S3. AlTiN coating is deposited by cathodic arc evaporation of AlTi. The workpiece gantry rotates in front of the target at a speed of 3.0 rpm. Nitrogen gas is introduced into the vacuum chamber at 300 sccm, and the chamber pressure is controlled at 3.0 Pa. The average current density on the target surface is 1.03 A / cm². 2 The average power density of the target surface is 21.6 W / cm². 2 Adjust the substrate negative bias to -100V and operate for 180 minutes; S4. After deposition is complete, wait for the temperature to drop to room temperature, remove the substrate, and obtain an AlTiN coating with a thickness of 5.5 μm deposited on the substrate surface.

[0041] Comparative Example 2 Similar to Comparative Example 1, the only difference being that the AlTi alloy target used was an Al alloy with an Al to Ti atomic ratio of 50:50. 50 Ti 50 An alloy target was used, and the deposition time was 90 min to obtain an AlTiN coating with a thickness of 3.3 μm deposited on the substrate surface.

[0042] Comparative Example 3 Similar to Comparative Example 1, the only difference is that in step S3, the deposition time is 720 min, resulting in an arc-deposited AlTiN coating with a thickness of 13.8 μm deposited on the substrate surface.

[0043] Comparative Example 4 Same as Example 1, except that the peak current is 200A.

[0044] Performance testing Figure 1 The diagram shows the deposition of the AlTiN coating in Example 1 (left) and the current and voltage waveforms when a single HiPIMS power supply is in operation (right).

[0045] Using nanoindentation (Anton Paar TTX-NHT) 2 The hardness and elastic modulus of the coating were tested, and the residual stress of the film was measured using a residual stress tester (SuPro Instruments). The film stress was calculated using the Stoney formula by subtracting the stresses before and after coating. Figure 2The nanoscale hardness, elastic modulus, H / E ratio, and residual stress of each comparative example and embodiment are shown. It can be seen that the AlTiN coatings in the embodiments maintain high hardness even at large thicknesses, while exhibiting low residual stress. In contrast, the AlTiN coatings prepared in the comparative examples show a decrease in hardness and a significant increase in residual stress with increasing thickness. The decrease in hardness may be due to defect accumulation within the coating, while the decrease in elastic modulus is mainly related to the coating thickness. Furthermore, the high H / E value also reflects the improved coating toughness to some extent; the H / E values ​​of Examples 1 and 2 are both above 0.09. For thick coatings, residual stress increases significantly with increasing thickness. It can be observed that the residual stress of Comparative Example 3, with a thickness of 13.8 μm, is -13.4 GPa, more than twice that of Comparative Example 1 prepared using the same process. Although Comparative Example 4 has low residual stress, its hardness is also low. In contrast, the residual stresses of Examples 1 and 2 are only -2.1 and -4.5 GPa, respectively, while maintaining good mechanical properties. In addition, although Comparative Example 2 can obtain the same mechanical properties as the Example, its residual stress is larger, the coating exhibits obvious columnar crystal growth, the grains are coarser and the Al content is lower, thus demonstrating that the method of the embodiment of the present invention can maintain high hardness under high Al content.

[0046] The surface and cross-sectional morphology of the coating were analyzed using SEM (SEM; Hitachi SU8220), and the composition of the coating was analyzed using EDS (EDS; Oxford Instruments X-MaxN). The thickness of the coating was measured by cross-section. The surface and cross-sectional SEM images, thickness, and EDS composition of the coatings in the comparative examples and embodiments are shown below. Figure 3 As shown, (a)-(f) represent Examples 1 and 2, and Comparative Examples 1-4, respectively (the top shows SEM images and EDS analysis results of the coating surface, and the bottom shows SEM images of the coating cross-section). Comparative Examples 1 and 3 show that the number of droplets on the surface of the arc-prepared coating increases with deposition time. In terms of cross-sectional morphology, Comparative Examples 1 and 3 have denser cross-sections, while those using Ti... 50 Al 50 Comparative Example 2, prepared from the target material, exhibits typical columnar crystal growth. Comparative Example 4 shows slender columnar crystal growth in its cross-section, with a distinct cauliflower-like morphology and microscopic pores, although its composition is similar to that of the examples. The AlTiN coating prepared in the examples has a smooth surface, no droplet defects, and a similarly dense cross-section. While ensuring excellent mechanical properties, it also achieves a high Al content, which is beneficial for improving its oxidation resistance. The coating prepared in the examples of this invention consists of a c-(Al,Ti)N main phase and a dispersed w-AlN secondary phase, wherein the atomic percentages of Al, Ti, and N are (35.0±5.0)%, (15±5)%, and (50±5.0)%, respectively; the coating has a nanocrystalline structure with an average grain size ≤20 nm.

[0047] The phase structure of the coating was analyzed using XRD (GIXRD; Bruker D8 Advance) at an incident angle of 5° to avoid interference from matrix diffraction peaks. The scanning range was 30°–70°. The GIXRD test results for Example 1, Comparative Example 1, and Comparative Example 2 are shown below. Figure 4 It can be seen that Comparative Example 2 has a higher Ti content, and the coating exhibits typical columnar crystal growth, resulting in stronger diffraction peaks, which corresponds to the SEM results. Comparative Example 1, due to its higher Al content, exhibits a fine nanocrystal growth morphology, and its GIXRD diffraction peaks are significantly broader than those of Comparative Example 2. Using the Scherrer formula, the grain size of Comparative Example 1 on the 200 plane is calculated to be 6.9 nm, while the grain size of Example 1 on the 111 plane is 11.4 nm. The grain refinement also leads to a decrease in its elastic modulus. The excellent mechanical properties of the coating may be attributed to the grain refinement and the combination of the cubic structure and the w-AlN two-phase composite.

[0048] Good adhesion is fundamental to the excellent performance of the film. The scratch test load ranged from 1N to 100N, with a scratch length of 3mm and a speed of 3mm / min. The Anton Par Revetest scratch tester was used to characterize the adhesion strength between the coating and the substrate. Figure 5 The scratch test results for Example 1 and the comparative examples are shown. It can be seen that in Comparative Example 1, the coating broke and peeled off from the substrate when the scratch loading force was 72.7 N. In Comparative Example 3, due to the longer deposition time, stress and defects accumulated and increased, resulting in flaky peeling at 51.9 N, but without substrate exposure, indicating cohesive failure of the coating. In Comparative Example 4, the coating peeled off at a scratch loading force of 71.3 N, with substrate exposure occurring simultaneously with cohesive peeling. In Example 1, no coating peeling occurred throughout the scratching process; only numerous arc-shaped cracks were observed inside the scratch, indicating good adhesion between the coating and the substrate, and excellent scratch crack propagation toughness.

[0049] The tribological properties of each coating at room temperature were tested using an Anton Par ball-and-disc high-temperature friction and wear testing machine. Al₂O₃ grinding balls were used, with a wear track radius of 2 mm, a linear velocity of 10 cm / s, a load of 5 N, 8000 test revolutions, and an ambient humidity of 45 ± 5%. The specific wear rate and average coefficient of friction (COF) of Examples 1 and 2 and Comparative Examples 1 and 2 are as follows: Figure 6 As shown, the wear track cross-sectional curve is as follows: Figure 7 As shown. From Figure 6It can be seen that Examples 1 and 2 exhibit excellent wear resistance, with wear rates reduced by approximately two orders of magnitude compared to Comparative Examples 1 and 2. However, since the AlTiN coating primarily undergoes abrasive wear during dry friction, the differences in friction coefficients among the various coating groups are relatively small. The wear track cross-sectional curves after coating friction are shown in the figures. Figure 7 It can be seen that the wear in Examples 1 and 2 was minimal after 8000 cycles of friction and wear testing.

[0050] The SEM morphology of the cutting edge and rake face of the coated cutting tool was analyzed using a Hitachi SU8220 SEM, and the three-dimensional morphology of the cutting edge was analyzed using a Bruker Alicona optical 3D metrology instrument. The SEM morphologies of the cutting edge and face of the coated cutting tools in Examples 1 and 2 and Comparative Examples 1 and 3 are shown below. Figure 8 As shown, the upper part represents the cutting edge, and the lower part represents the blade surface. It can be seen that the coated blades of Examples 1 and 2 have sharp and smooth cutting edges, while the cutting edges of Comparative Examples 1 and 3 show coating peeling, resulting in significant dulling of the cutting edges. The three-dimensional morphologies of the bare blade substrate (YG8, tested twice), and the coated blades prepared in Examples 1 and 2 and Comparative Examples 1 and 3 are shown below. Figure 9 As shown, compared with the bare blade, the coated blades in Examples 1 and 2 show little change, while the cutting edges of Comparative Examples 1 and 3 are significantly roughened and dulled.

[0051] Figure 10 The figures show the micro-edge radius values ​​of the coated cutting tools (Examples 1 & 2) and the uncoated bare cutting tool (YG8, tested twice) in Examples 1 & 2 and Comparative Examples 1 & 3. These values ​​were obtained using a Bruker alicona optical 3D metrology instrument. As can be seen from the figures, the micro-edge radius values ​​of the thick AlTiN coated cutting tools in Examples 1 & 2 are almost the same as those of the uncoated bare cutting tool. However, the micro-edge radius values ​​of Comparative Examples 1 & 3, which were prepared using arc technology, are significantly increased. The micro-edge radius value of Comparative Example 3, with a thickness of 13.8 μm, increases to 82.238 μm, indicating that its cutting edge has undergone severe passivation.

[0052] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A robust, integrated, low-stress, ultra-thick AlTiN-based coating, characterized in that, The coating is deposited on the substrate; The coating thickness is 5–21 μm; The coating consists of a c-(Al,Ti)N main phase and a dispersed w-AlN secondary phase, wherein the atomic percentages of Al, Ti, and N are (35.0±5.0)%, (15±5)%, and (50±5.0)%, respectively. The coating has a nanocrystalline structure with an average grain size of ≤20nm.

2. The ultra-thick AlTiN-based coating according to claim 1, characterized in that, The thickness of the coating is 9.4–21 μm.

3. The ultra-thick AlTiN-based coating according to claim 1, characterized in that, The surface roughness of the coating is ≤0.2μm.

4. The ultra-thick AlTiN-based coating according to claim 1, characterized in that, The coating has a nanohardness ≥30GPa, an adhesion force to the substrate ≥100N, and a residual stress of -2 to -6GPa.

5. A method for preparing a strong and tough integral low-stress ultra-thick AlTiN-based coating as described in any one of claims 1-4, characterized in that, The high-power pulsed magnetron sputtering technology includes the following steps: (1) Place the substrate in a vacuum chamber and evacuate to a background vacuum of 4 to 7 × 10⁻⁶. -3 Pa, heated to 250-500℃; Ar gas was introduced for glow discharge cleaning and ion bombardment activation treatment; (2) Maintain the chamber temperature at 350-450℃, introduce a mixture of Ar and N2 gas, and the total pressure of the chamber is 0.4-1.0 Pa; turn on the planar target containing Al and Ti elements, and use high-power pulsed magnetron sputtering technology to deposit and prepare a strong and tough integrated low-stress ultra-thick AlTiN base coating.

6. The method according to claim 5, characterized in that, Step (1) specifically includes: The deposition chamber is heated to 250–500°C, and the background vacuum is reduced to 4–7 × 10⁻⁶. -3 Pa; Introduce 200-300 sccm of Ar gas, adjust the chamber pressure to 2.0 Pa, and apply a negative bias voltage of -800 to -1000 V to the substrate for glow cleaning for 15-30 min. Then, adjust the chamber temperature to 350℃, the Ar gas flow rate to 70-100 sccm, and the chamber pressure to 0.5 Pa. Turn on the ion source or Cr target to perform ion bombardment activation treatment on the substrate surface. The substrate negative bias voltage is -800 to -1000 V, and the treatment lasts for 3-10 minutes.

7. The method according to claim 5, characterized in that, In step (2), the process parameters of the high-power pulsed magnetron sputtering are: deposition time of 1 to 4 hours, target power of 3 to 15 kW, peak current of 300 to 600 A, pulse frequency of 200 to 500 Hz, and pulse width of 50 to 250 μs.

8. The method according to claim 5, characterized in that, In step (2), the distance between the substrate and the target material during deposition is 8 to 12 cm, and the negative bias voltage applied to the substrate is -50 to -300 V.

9. The method according to claim 5, characterized in that, The planar target is an AlTi alloy target, wherein the atomic ratio of Al to Ti is 67:

33.

10. The application of a strong and tough integrated low-stress ultra-thick AlTiN-based coating as described in any one of claims 1-4, or a coating prepared by the method according to any one of claims 5-9, characterized in that, The coating is applied to the surface of high-speed heavy-duty cutting tools, molds, or wear-resistant parts.

Images