AlCrSiWN / Mo nano-composite coating with high hardness and high wear resistance and preparation process of AlCrSiWN / Mo nano-composite coating

Abstract

The invention discloses an AlCrSiWN / Mo nano-composite coating with high hardness and high wear resistance and a preparation process of the AlCrSiWN / Mo nano-composite coating, and belongs to the technical field of coatings. The nano-composite coating is formed by doping Mo element in an AlCrSiWN high-hardness coating by adopting an arc ion plating technology, and the thickness of the nano-composite coating is 3-4 microns. The preparation process of the coating comprises the steps that an AlCrN transition layer of a columnar crystal structure is prepared firstly, then an AlCrSiW target and a CrMo target are started at the same time, the AlCrSiWN / Mo nano-composite coating with the high hardness and the self-lubricating performance is obtained by regulating and controlling the evaporation current of the CrMo target to be 122-150 A and utilizing the synergistic effect of the self-lubricating characteristic of the Mo element and the high hardness characteristic of the AlCrSiWN coating, and the self-lubricating performance of the AlCrSiWN / Mo nano-composite coating is improved while the high hardness of the coating is kept. The toughness and the self-lubricating performance of the coating are improved, and the friction coefficient is reduced while crack propagation is inhibited.

Description

Technical Field

[0001] This invention relates to the field of coating technology, specifically to an AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance, and its preparation process. Background Technology

[0002] High-speed dry cutting technology, as a green manufacturing process, has shown significant advantages in reducing the use and emission of cutting fluid, lowering processing costs, and improving production efficiency, and has become an important direction for the green development of the manufacturing industry. High-speed dry cutting faces challenges such as rapid tool wear, easy adhesion between workpiece material and tool, and high temperatures in the cutting zone. Preparing a high-performance coating on the tool surface can form an effective thermal barrier, hindering the transfer of cutting heat to the tool substrate, reducing the temperature of the tool substrate, maintaining the cutting performance and stability of the tool, improving wear resistance and high-temperature resistance, and extending tool life. In the machining of high-strength, high-toughness, and difficult-to-machine materials such as titanium alloys, the core bottleneck of current machining technology lies in the extreme cutting forces and high temperatures generated during the cutting process, which exacerbate tool wear and thus severely restrict machining efficiency and surface quality. Coated tools face even more complex and demanding working conditions, placing higher requirements on the mechanical properties and wear resistance of the coating.

[0003] In AlCrSiN coatings, the amorphous Si3N4 phase formed by Si and N elements is distributed along the grain boundaries, creating an amorphous encapsulated nanocrystalline structure, which improves the coating's thermal stability and oxidation resistance. Introducing W into the AlCrSiN coating effectively enhances its hardness and high-temperature resistance through solid solution strengthening and grain refinement effects. Hard coatings possess high hardness but are brittle, easily developing microcracks and spalling during friction or under impact loads, resulting in poor wear resistance. Summary of the Invention

[0004] To address the aforementioned shortcomings in existing technologies, the present invention aims to provide an AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance, and its preparation process. Using arc ion plating technology, Mo is doped into a high-hardness AlCrSiWN coating to form a nanocomposite coating. Utilizing the synergistic effect of the self-lubricating properties of Mo and the high hardness of the AlCrSiWN coating, an AlCrSiWN / Mo nanocomposite coating exhibiting both high hardness and high wear resistance is obtained. While maintaining high coating hardness, the coating's toughness and self-lubricating properties are improved, crack propagation is inhibited, and the coefficient of friction is reduced.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: An AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance is deposited on the surface of a cemented carbide substrate. It is formed by doping Mo into an AlCrSiWN high-hardness coating and has a thickness of 3~4μm. The surface of the nanocomposite coating has banded clusters, and the banded clusters are tightly bonded to the coating surface.

[0006] Furthermore, the chemical composition of the nanocomposite coating, by atomic percentage, is as follows: Al 6.03~20.74 at.%, Cr 21.78~35.59 at.%, Mo 5.0~10.13 at.%, Si 1.71~5.01 at.%, W 1.1~3.74 at.%, and N 46.37~48.87 at.%.

[0007] Furthermore, in the chemical composition of this nanocomposite coating, the Mo content is preferably 5.6~9.8 at.%.

[0008] Furthermore, the microstructure of the AlCrSiWN / Mo nanocomposite coating includes c-WN, h-Cr2N, h-W2N and t-Mo2N phases.

[0009] Furthermore, an AlCrN transition layer is deposited between the nanocomposite coating and the substrate. The AlCrN transition layer has a columnar crystal structure and a thickness of 100~130 nm.

[0010] Furthermore, the AlCrSiWN / Mo nanocomposite coating can achieve a hardness of 41.49 GPa and an elastic modulus of 458 GPa.

[0011] Furthermore, the AlCrSiWN / Mo nanocomposite coating exhibits a friction coefficient and wear rate as low as 0.42 and 1.46 × 10⁻⁶, respectively. -10 mm 3 / (N•mm).

[0012] Furthermore, the preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance is as follows: using arc ion plating technology, first depositing an AlCrN transition layer on the substrate, and then simultaneously turning on the AlCrSiW target and the CrMo target to deposit the AlCrSiWN / Mo nanocomposite coating.

[0013] Furthermore, during the deposition of the AlCrSiWN / Mo nanocomposite coating, N2 was introduced into the vacuum deposition chamber, and the N2 flow rate was adjusted to 1260~1390 sccm. Simultaneously, the AlCrSiW and CrMo targets were turned on, and the vacuum level was controlled to be 3×10⁻⁶. -3The deposition temperature is 400~500℃ above Pa; the evaporation current of AlCrSiW target is controlled at 120~160 A, and the evaporation current of CrMo target is controlled at 122~150 A.

[0014] Furthermore, the preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance specifically includes the following steps: (1) After ultrasonic cleaning and drying, the substrate is fixed on the sample holder and suspended on the rotating frame in the coating chamber to ensure that the substrate is facing the coating target. (2) Evacuate the coating chamber to a vacuum level of 3.0 × 10⁻⁶. -3 Above Pa, heat the vacuum coating chamber temperature to 400~500 ℃ and hold it at that temperature for 30 min; (3) Etching and cleaning: Turn on the etching Ti target and etch and clean the substrate in an Ar atmosphere; (4) Deposition of AlCrN transition layer: Introduce N2 and turn on AlCr target, deposition time is 30~35 min; (5) Deposit AlCrSiWN / Mo nanocomposite coating. The total deposition time is 100~130 min. The content of Mo element in the coating is controlled by adjusting the evaporation current of CrMo target. Finally, AlCrSiWN / Mo nanocomposite coating is obtained.

[0015] Further, in step (3), the etching and cleaning process is as follows: after the vacuum coating chamber is heated and kept at a constant temperature for 30 minutes, Ar is introduced with an Ar flow rate of 150~300 sccm. The deposition pressure is controlled at 0.26~0.35 Pa, and the Ti target etching is turned on with a Ti target evaporation current of 120~140 A. The DC bias voltage is set to increase from -10 V to -180 V in a gradient. The etching and cleaning time is 60~90 minutes.

[0016] Further, in step (4), after etching and cleaning, an AlCrN transition layer is deposited. During the deposition process, N2 with a flow rate of 1220~1280 sccm is introduced, the deposition pressure is 3.2~4.5 Pa, the AlCr target evaporation current is 120~140 A, and the bias voltage is -40~-60 V.

[0017] Furthermore, in step (5), when depositing the AlCrSiWN / Mo nanocomposite coating, the rotation speed of the rotating frame is 2.3 r / min to 3 r / min, the deposition pressure is 3.5 to 4 Pa, and the DC bias voltage is -120 to -160 V.

[0018] Furthermore, during step (5) when depositing the AlCrSiWN / Mo nanocomposite coating, as the Mo content increases, the diffraction peak of the t-Mo2N phase (220) crystal plane shifts to a higher angle.

[0019] The design mechanism of this invention is as follows: During high-speed dry cutting, the cutting tool is subjected to a large amount of cutting heat and cutting force. In order to reduce the cutting heat generated by the cutting tool during the cutting process, a coating with high hardness, high wear resistance and self-lubricating properties is prepared on the surface of the cutting tool. This can achieve solid lubrication, reduce wear and adhesion between the cutting tool and the workpiece, and enable the cutting tool to maintain good cutting performance even at high cutting temperatures.

[0020] This invention employs arc ion plating technology to deposit an AlCrSiWN / Mo nanocomposite coating on a cemented carbide substrate. Addressing the challenges of plastic deformation, rapid tool wear, and chipping during titanium alloy machining, an appropriate amount of Mo is incorporated into the AlCrSiWN hard coating. Utilizing the synergistic effect of Mo's self-lubricating properties and the high hardness of the AlCrSiWN coating, a composite coating with high hardness and high wear resistance is obtained. At high temperatures, the Mo-containing coating readily oxidizes to form a MoO3 oxide lubricating phase with low shear strength, easy slippage, and good thermal stability, thus improving the coating's wear resistance. Simultaneously, the incorporation of Mo helps form a dense and stable composite oxide film on the coating surface, effectively blocking oxygen diffusion inward, delaying oxidation, and endowing the coating with excellent wide-temperature-range self-lubricating properties. During cutting, Mo readily forms a transfer film with low shear modulus, reducing the coefficient of friction, minimizing adhesive wear, and inhibiting built-up edge formation, thereby improving tool life and workpiece surface quality. Furthermore, by controlling the Mo element content and deposition process, the growth stress and thermal stress within the coating can be adjusted, reducing brittleness, minimizing the generation and propagation of microcracks, improving the bonding strength between the coating and the substrate, and preventing peeling under impact or heavy load conditions. This invention prepares a series of AlCrSiWN / Mo nanocomposite coatings by changing the CrMo target current to control the Mo element content in the coating.

[0021] The advantages and beneficial effects of this invention are as follows: 1. The AlCrSiWN / Mo nanocomposite coating prepared by this invention has high friction reduction ability and obvious wear resistance effect.

[0022] 2. The AlCrSiWN / Mo nanocomposite coating of this invention maintains the high hardness of the AlCrSiWN coating, and by introducing Mo element, forms an oxide lubricating film with low shear strength and easy slippage, thereby achieving the friction reduction effect of the coating and preparing a nanocomposite coating with high hardness, high wear resistance and self-lubricating properties.

[0023] 3. The AlCrSiWN / Mo nanocomposite coating of this invention shows broad application prospects in the field of machining difficult-to-machine materials. While maintaining high hardness during tool cutting, it generates an oxide lubricating film, which can significantly reduce the coefficient of friction, reduce the generation of cutting heat, extend the service life of tools, and improve cutting efficiency.

[0024] 4. The AlCrSiWN / Mo nanocomposite coating of this invention has both excellent mechanical and tribological properties, and the coated tool is capable of high-speed, heavy-load continuous machining conditions. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the AlCrSiWN / Mo nanocomposite coating structure prepared by arc ion plating technology in Example 1.

[0026] Figure 2 The elemental composition and content of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 are shown.

[0027] Figure 3 The XRD patterns of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 are shown.

[0028] Figure 4 The surface morphology of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 is shown.

[0029] Figure 5 The cross-sectional morphology of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 is shown.

[0030] Figure 6 The hardness and elastic modulus of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 are shown.

[0031] Figure 7 The critical load and scratch morphology of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 are shown.

[0032] Figure 8 The friction coefficient curves are shown for AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1.

[0033] Figure 9 The friction coefficient and wear rate of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 are shown.

[0034] Figure 10 The two-dimensional wear morphology of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared by arc ion plating technology in Example 1 is shown below; where: (a) 0 at.%; (b) 4.69 at.%; (c) 6.06 at.%; (d) 7.79 at.%; (e) 10.13 at.%. Detailed Implementation

[0035] The present invention will be further described in detail below through embodiments.

[0036] This invention incorporates an appropriate amount of Mo into an AlCrSiWN coating. By leveraging the synergistic effect of Mo's self-lubricating properties and the high hardness of the AlCrSiWN coating, a composite coating exhibiting both high hardness and high wear resistance is obtained. This reduces the coefficient of friction, minimizes adhesive wear, inhibits built-up edge formation, and improves tool life and workpiece surface quality.

[0037] In the following embodiments, a high-purity Ti target is used for etching and cleaning, a high-purity AlCr alloy target is used for depositing a transition layer, and a high-purity AlCrSiW alloy target and a high-purity CrMo alloy target are used for depositing a nanocomposite functional layer. The purity of the Ti target, AlCr alloy target, AlCrSiW alloy target, and CrMo alloy target is all above 99.95%.

[0038] In AlCr alloy targets, Al:Cr = 70:30 (atomic ratio); in AlCrSiW alloy targets, Al:Cr:Si:W = 52:28:15:5 (atomic ratio); and in CrMo alloy targets, Cr:Mo = 85:15 (atomic ratio).

[0039] Example 1:

[0040] This embodiment describes the preparation of AlCrSiWN / Mo nanocomposite coatings with different Mo contents.

[0041] In this embodiment, an AlCrSiWN / Mo nanocomposite coating was deposited on a cemented carbide substrate (25 mm × 25 mm × 3 mm) of grade YG8. The deposition was performed using arc ion plating technology, and the specific operation process is as follows: (1) Pretreatment before coating: The cemented carbide substrate was polished and then ultrasonically cleaned. The cleaning process was carried out in an ultrasonic cleaner, using acetone and alcohol as solvents in sequence, and ultrasonic cleaning for 15 min each. After cleaning, the sample was dried with high-purity nitrogen. Then, the sample was mounted on the fixture and pressed and fixed. After the vacuum chamber was depressurized, the furnace door was opened, and the clamped substrate was fixed on the rotating frame in the coating chamber with iron wire. The position of the substrate was adjusted so that its surface was facing the target.

[0042] (2) Vacuuming: The coating deposition process needs to be carried out in a high vacuum environment. The vacuuming process of the coating system is divided into two stages: First, rough evacuation is performed, that is, the pre-evacuation pump and the Roots pump are started to reduce the pressure in the vacuum chamber to below 30 Pa; then fine evacuation is performed, at which time the turbomolecular pump is turned on to further increase the system vacuum to 3×10 Pa. -4 Pa or above.

[0043] (3) Heating and constant temperature: Set the heating temperature of the coating system to 500 ℃, and keep it at this temperature for 30 min after heating is completed.

[0044] (4) Etching and Cleaning: A simultaneous etching process using argon ions and titanium metal ions is employed. This process relies on various active components in the plasma, such as ions, electrons, active groups, metastable excited nuclides, and photons. These components work together on the material surface, effectively removing surface contaminants and activating its surface chemical activity through continuous particle bombardment. Specific process parameters are as follows: argon gas is introduced at a flow rate of 180 sccm, the deposition pressure is 0.31 Pa, and the Ti target etching is activated with an arc source current of 140 A. The DC bias voltage is gradually increased from -10 V to -150 V, and the etching time is 75 min. After etching, the etching arc source and bias voltage are turned off, the gas is shut off, and the furnace is evacuated for 10 min to remove residual gas. Etching and cleaning remove oxides and other impurities from the substrate surface and activate the substrate surface.

[0045] (5) Deposition of transition layer: Turn on AlCr target, introduce N2 flow rate of 1230 sccm, stabilize the deposition pressure at 3.3Pa, AlCr target arc source current of 130 A, DC bias of -40 V, deposit for 30 min to obtain AlCrN transition layer.

[0046] (6) Deposition of AlCrSiWN / Mo nanocomposite coating: AlCrSiW target and CrMo target are turned on at the same time. The evaporation current of AlCrSiW target is 150 A, and the evaporation current of CrMo target is 0 A, 120 A, 130 A, 140 A and 150 A respectively. The N2 flow rate is adjusted to 1310 sccm to stabilize the pressure at 3.6 Pa. The rotation speed of the rotating frame is 3 r / min. The DC bias voltage is -150 V. The deposition time is 120 min.

[0047] (7) Cooling in the furnace: After the coating is completed, all arc sources and bias voltages are turned off, and the coated sample is cooled in the vacuum furnace.

[0048] The microstructure and performance of AlCrSiWN / Mo nanocomposite coatings with different Mo contents prepared in this embodiment were characterized and tested as follows: The phase structure of the coating was characterized by X-ray diffraction (XRD). The test was conducted using Cu target Kα radiation (λ=0.154056 nm). Diffraction patterns in the range of 20° to 80° (2θ) were acquired in step scan mode under tube voltage of 40 kV and tube current of 40 mA. The scan step size was 0.02° and the dwell time was 0.2 s per step.

[0049] The hardness and elastic modulus of the coating were tested using a nanoindenter (Anton Paar, TTX-NHT-3). To minimize the influence of the matrix effect, the indentation depth was controlled to not exceed one-tenth of the total coating thickness, and data from 15 measuring points were collected under the same conditions and averaged.

[0050] The film-substrate adhesion strength of the coating was evaluated using an Anton Paar RST-3 scratch tester. The test used a diamond indenter with a diameter of 200 μm, which scratched a 3 mm length at a speed of 6 mm / min under a set load of 100 N. All data were automatically collected and recorded by a computer.

[0051] The tribological properties of the coating were evaluated using an Anton Paar THT tribological testing machine. Al₂O₃ spheres (hardness 22±1 GPa) with a diameter of 6 mm were used as the friction pair. Under a normal load of 6 N, sliding friction was conducted over 180 m at a linear velocity of 0.1 m / s and a rotation radius of 6 mm. All tests were performed in a constant temperature and humidity environment (22±3 ℃, relative humidity 30%), and each sample was tested three times to ensure data reliability.

[0052] The surface morphology of the worn coating was observed using a super depth-of-field microscope (Keyence VHX-1000C), and the wear rate was calculated using the formula W=V / (F×S) based on the wear volume V, normal load F and sliding distance S.

[0053] The AlCrSiWN / Mo nanocomposite coating structure prepared in this embodiment is as follows: Figure 1 As shown, the bottom layer of the coating is an AlCrN transition layer, whose typical columnar crystal structure helps to improve the bonding performance between the coating and the cemented carbide substrate. The functional layer is an AlCrSiWN / Mo nanocomposite coating with a thickness of about 3 μm. This nanocomposite functional layer has high hardness and toughness, which can effectively reduce crack propagation, while also having a low coefficient of friction, thus improving the wear resistance of the coating.

[0054] Figure 2The elemental composition and content variations of AlCrSiWN / Mo coatings with different Mo contents are shown. The Mo content in the coating was controlled by varying the CrMo target evaporation current. With increasing target evaporation current, the Mo content in the coating increased. The Mo contents in the coatings at CrMo target evaporation currents of 0 A, 120 A, 130 A, 140 A, and 150 A were 0 at.%, 4.69 at.%, 6.06 at.%, 7.79 at.%, and 10.13 at.%, respectively. Both Al and Si elements in the coating showed a decreasing trend with increasing target evaporation current.

[0055] Figure 3 XRD patterns of AlCrSiWN / Mo coatings with different Mo contents are shown. Without Mo doping, the AlCrSiWN hard coating mainly consists of c-WN, h-Cr2N, and h-W2N phases. Due to the introduction of Mo, a t-Mo2N tetragonal phase is formed in the AlCrSiWN hard coating and preferentially oriented along the (200) crystal plane. The diffraction peaks of the c-WN phase disappear because the binding energy between Mo and N is higher than that between W and N. Therefore, during coating preparation, N preferentially reacts with Mo to form the more stable Mo2N phase, inhibiting the formation of the WN phase. Since the atomic radius of Mo is smaller than that of W, Mo atoms may replace W or occupy interstitial positions, leading to local lattice distortion and disrupting long-range order. This results in a decrease in the intensity of the (102), (110), and (201) diffraction peaks of the h-W2N phase. When the Mo content is moderate, Mo atoms can completely dissolve into the t-Mo2N lattice, which avoids phase separation caused by excessive Mo content and compensates for nitrogen vacancy defects at low Mo content, promoting continuous grain growth and reducing grain boundary scattering. At this time, the stress reaches equilibrium. Therefore, when the Mo content is 6.06 at.%, the diffraction peak of the (200) crystal plane of the t-Mo2N phase is narrowed and the intensity is increased. When the Mo content increases to 7.79 at.%, the uniform compressive stress generated by Mo solid solution offsets part of the tensile stress, stabilizing the (220) crystal plane spacing and sharpening the peak shape.

[0056] Figure 4The surface morphology of AlCrSiWN / Mo coatings with different Mo contents is shown. Although the coatings prepared by arc ion plating exhibit excellent mechanical properties, during the deposition process, the cathode arc spot generates high-density plasma and a large number of molten metal droplets as it moves across the target surface. These molten particles co-deposit with metal ions, forming microscopic defects such as large particles and droplets on the coating surface. Without Mo doping, the coating surface has fewer droplets but more uneven pits and particles. After Mo doping, the coating surface shows more large particles and droplets, with gaps between the large particles and the coating surface, resulting in a loose structure at the bonding sites. EDS elemental analysis of the large particles revealed that the large particle clusters are aggregates of Cr, Mo, and N elements. This is attributed to the high melting points of Cr and Mo, which are not easily completely evaporated during arc discharge and deposit as molten droplets on the substrate surface, forming large particles. Al and Si, with their lower melting points, are more easily vaporized during preparation and deposited uniformly on the substrate surface in an ionic state. Furthermore, Mo has a larger atomic mass and higher deposition energy. High-energy Mo atoms have stronger kinetic energy when migrating on the coating surface, making them prone to aggregation in localized areas to form clusters. As the Mo content increases to 6.06 at.%, banded clusters appear on the coating surface, with the clusters tightly bonded to the surface. This is attributed to the high melting point of Mo during coating preparation, leading to Mo atom enrichment at grain boundaries or defects, resulting in surface segregation and promoting the precipitation of the Mo₂N phase. XRD patterns confirm that the intensity of the diffraction peak on the (200) crystal plane of the t-Mo₂N phase increases when the Mo content reaches 6.06 at.%. The precipitated phase exhibits a banded distribution on the coating surface, forming a cluster structure. When the Mo content is 7.79 at.%, the number of particles and clusters on the coating surface decreases significantly. This is attributed to the increased full width at half maximum (FWHM) of the diffraction peaks, reduced grain size, and fewer defects on the coating surface. When the Mo content increases to 10.13 at.%, partial peeling occurs on the coating surface. The magnified view shows gaps between the cauliflower-like crystal clusters and the coating surface. This is attributed to the increased particle size and kinetic energy at this point, which causes localized micro-regional plastic deformation or micro-cracks on the coating surface during the deposition process.

[0057] Figure 5The cross-sectional morphology of AlCrSiWN / Mo coatings with different Mo contents is shown. All coatings exhibit uniform and dense structures, and Mo doping refines the columnar crystal structure. With increasing CrMo target current, the interaction between the electric and magnetic fields near the target surface becomes stronger, resulting in incident particles with higher energy. This allows for more complete diffusion of deposited particles within the coating, increasing the deposition rate. Consequently, the coating thickness increases from 2.91 μm to 4.28 μm with increasing Mo content. Furthermore, the higher-energy incident particles, during their movement towards the substrate surface and deposition to form the coating, overcome the interatomic bonding forces, resulting in more uniform and complete diffusion, improved coating density, and reduced porosity and defects. The thermal expansion coefficient of AlCrN falls between that of the cemented carbide substrate and the AlCrSiWN / Mo coating, effectively buffering thermal mismatch stress caused by temperature changes and preventing coating peeling. Therefore, preparing an AlCrN transition layer with columnar crystal growth characteristics perpendicular to the interface between the AlCrSiWN / Mo coating and the substrate helps improve the bonding strength between the coating and the substrate.

[0058] Figure 6The hardness and elastic modulus of AlCrSiWN / Mo coatings with different Mo contents are shown. The coating without Mo doping exhibits the highest hardness and elastic modulus values, at 41.49 GPa and 458 GPa, respectively. This is attributed to the high hardness of the cubic WN phase in the AlCrSiWN coating and the high content of the WN phase at this stage. Furthermore, Mo promotes the formation of a denser nanocomposite structure. The Si3N4 amorphous phase can uniformly encapsulate the WN nanocrystals, effectively hindering dislocation movement and suppressing local plastic deformation through a high-energy interface, resulting in higher macroscopic stiffness and forming an ultra-hard structure. The tetragonal Mo2N phase formed after Mo doping has significantly lower hardness than the cubic WN phase. Combined with XRD patterns, it can be seen that Mo doping inhibits the formation of the high-hardness cubic WN phase. Mo doping may also promote grain growth, interfere with the amorphous phase distribution, reduce the strengthening effect of the nanocrystal-amorphous interface, and increase nitrogen vacancy defects in the coating, thus reducing bonding strength. When the Mo content is 4.69 at.%, the hardness and elastic modulus of the AlCrSiWN / Mo coating both decrease significantly. As the Mo content increases to 6.06 at.%, the increased concentration of dissolved Mo atoms leads to greater lattice distortion, and the elastic modulus of the coating begins to recover. When the Mo content is 7.79 at.%, the hardness and elastic modulus of the coating increase to 36.75 GPa and 445.04 GPa, respectively. Considering the phase composition and microstructure of the coating, the grain size decreases at this point. Based on the Hall-Petch principle, smaller grain size and more grain boundaries create a stronger barrier to dislocation movement, improving the coating's resistance to external loads and enhancing its mechanical properties. When the Mo content is 10.13 at.%, the hardness and elastic modulus of the AlCrSiWN / Mo coating both reach their lowest values, at 30.52 GPa and 385.08 GPa, respectively. The decline in mechanical properties is attributed to two aspects: Firstly, as can be seen from the surface morphology of the coating, there is partial peeling on the coating surface, and some microcracks exist at the junction of the particles and the coating surface, which reduces the coating's ability to resist external loads. Secondly, the doping of Mo introduces more interfaces or phase boundaries, and the newly added interface structure leads to uneven distribution of local stress. Under the action of external force, the interface area is prone to elastic deformation, resulting in a decrease in the coating's hardness and elastic modulus.

[0059] Figure 7The scratch morphology and critical load of AlCrSiWN / Mo coatings with different Mo contents are shown. With increasing Mo content, the critical load increases from 69.91 N to 85.01 N. Without Mo doping, the coating exhibits high hardness and brittleness, making it difficult to achieve stress homogenization through plastic flow under high normal loads. Hard particles experience severe friction or brittle fracture with the indenter during scratch loading, leading to a sudden increase in acoustic emission signal and significant fluctuations in the signal curve. Obvious blocky peeling of the coating occurs near the critical load, while no wavy plastic deformation is observed at the critical load, indicating low coating toughness and susceptibility to brittle peeling. With Mo doping, no coating peeling is observed at the scratches, but wavy plastic deformation marks appear at the critical loads. Stress is dissipated through plastic deformation rather than interfacial peeling, indicating that the coating undergoes three stages during the scratching process: elastic deformation, plastic deformation, and failure. The AlCrSiWN / Mo coating exhibited stable acoustic emission (AE) signal curves during scratching, but high peak values ​​appeared near the critical load. This is attributed to the energy released during the cracking or peeling of the coating from the substrate under the scratching action of the indenter, generating AE signals. When the critical load is reached, significant bonding failure occurs between the coating and the substrate, such as microcracks, fractures, and peeling, releasing a large amount of energy instantaneously and causing a sudden increase in the AE signal peaks. With increasing CrMo target current, ions acquire higher migration energies, enhancing their diffusion ability on the substrate surface and increasing the critical load of the coating. The critical load of the coating reaches its highest value of 85.01 N when the CrMo target current is 7.79 at.%.

[0060] Figure 8 The friction coefficient curves for AlCrSiWN / Mo coatings with different Mo contents are shown. All AlCrSiWN / Mo coatings with different Mo contents exhibit distinct running-in and stable wear stages during friction. This is attributed to the presence of numerous microscopic protruding particles on the coating surface prepared by arc ion plating. At the beginning of friction, these particles undergo shearing and plastic deformation under the action of frictional force, causing a sudden increase in frictional resistance and a sharp rise in the friction coefficient. As the friction process continues, the particles are gradually worn down or peeled off under the action of abrasive wear mechanism, and the wear between the friction pair and the coating begins to enter a relatively stable stage. After doping with Mo, under load, the Mo-containing solid lubricating particles on the coating surface soften in the friction contact area and fill into adjacent microscopic depressions, forming a discontinuous initial lubricating film. As friction continues, the lubricating phase further diffuses and extends, eventually forming a uniformly covered continuous lubricating film on the coating surface. When the Mo content is 6.06 at.%, the friction coefficient curve fluctuates between 0.45 and 0.6. This is attributed to the fact that during the friction process, some of the wear debris fails to detach from the contact area in time and remains at the friction interface, repeatedly participating in the friction process.

[0061] Figure 9 The friction coefficient and wear rate of AlCrSiWN / Mo coatings with different Mo contents were compared. Without Mo doping, the coating mainly consisted of highly brittle WN and W₂N phases, which easily led to cracking and spalling during friction. The coating's friction coefficient and wear rate reached their highest values, at 0.76 and 3.14 × 10⁻⁶, respectively. -9 mm 3 / (N·mm). Mo doping promotes the formation of the lubricating phase, resulting in a layered, low-shear-modulus MoO3 and other Magnéli phase oxide lubricating film on the coating surface. Both the coating friction coefficient and wear rate decrease significantly. The friction coefficient reaches its lowest value (0.42) when the Mo content is 7.79 at.%. Combined with surface morphology and mechanical properties, it can be seen that the coating surface has relatively few defects at this level, and the hardness value begins to recover after a significant decrease. When the Mo content increases to 10.13 at.%, the high Mo content generates the largest coverage MoO3 lubricating film during friction, and the wear rate reaches its lowest value (1.46 × 10⁻⁶). -10 mm 3 / (N·mm).

[0062] Figure 10 The two-dimensional wear track morphology of AlCrSiWN / Mo coatings with different Mo contents is shown. Without Mo doping, the coating adhesion is low, and the bonding strength between the hard phase and the matrix is ​​weak. Under cyclic frictional shear force, the hard particles on the coating surface brittlely peel off and participate in the friction process. Under the vertical load of Al2O3 on the wear pair, numerous scratches appear in the wear track area, forming three-body wear, resulting in deep furrows and some pits within the wear track. As the Mo content continues to increase to 6.06 at.%, the number of furrows inside the wear track decreases, and some adhesive wear and oxidative wear appear, forming a continuous and uniform debris accumulation area around the wear track. When the Mo content is 7.79 at.%, the wear track is the narrowest, and the wear debris at the edge of the wear track is the least, because at this point the coating hardness value is high and the critical load is highest, resulting in high resistance to deformation during friction. When the Mo content increases to 10.13 at.%, there are many granular protrusions inside the wear track. Combined with the surface morphology, it can be seen that at this point, the coating surface has a large number of large particles with large sizes.

[0063] 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.

[0064] The above description 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 scope of protection of the present invention.

Claims

1. An AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance, characterized in that: The nanocomposite coating is deposited on the surface of a cemented carbide substrate and is formed by doping Mo into an AlCrSiWN high-hardness coating. Its thickness is 3~4μm. The surface of the nanocomposite coating has banded clusters, and the banded clusters are tightly bonded to the coating surface. The microstructure of the AlCrSiWN / Mo nanocomposite coating includes c-WN, h-Cr2N, h-W2N and t-Mo2N phases.

2. The AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 1, characterized in that: The chemical composition of the nanocomposite coating, by atomic percentage, is as follows: Al 6.03~20.74 at.%, Cr 21.78~35.59 at.%, Mo 5.0~10.13 at.%, Si 1.71~5.01 at.%, W 1.1~3.74 at.%, and N 46.37~48.87 at.%.

3. The AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 1, characterized in that: An AlCrN transition layer is deposited between the nanocomposite coating and the substrate. The AlCrN transition layer has a columnar crystal structure and a thickness of 100~130 nm.

4. The AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 1, characterized in that: The AlCrSiWN / Mo nanocomposite coating can achieve a hardness of 41.49 GPa and an elastic modulus of 458 GPa.

5. The AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 1, characterized in that: The AlCrSiWN / Mo nanocomposite coating exhibits a friction coefficient and wear rate as low as 0.42 and 1.46 × 10⁻⁶, respectively. -10 mm 3 / (N•mm).

6. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to any one of claims 1-5, characterized in that: This process employs arc ion plating technology, first depositing an AlCrN transition layer on the substrate, and then simultaneously activating AlCrSiW and CrMo targets to deposit an AlCrSiWN / Mo nanocomposite coating.

7. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 6, characterized in that: During the deposition of the AlCrSiWN / Mo nanocomposite coating, N2 was introduced into the vacuum deposition chamber, and the N2 flow rate was adjusted to 1260~1390 sccm. Simultaneously, the AlCrSiW and CrMo targets were turned on, and the vacuum level was controlled at 3×10⁻⁶. -3 The deposition temperature is 400~500℃ above Pa; the evaporation current of AlCrSiW target is controlled at 120~160 A, and the evaporation current of CrMo target is controlled at 122~150 A.

8. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 6 or 7, characterized in that: The process specifically includes the following steps: (1) After ultrasonic cleaning and drying, the substrate is fixed on the sample holder and suspended on the rotating frame in the coating chamber to ensure that the substrate is facing the coating target. (2) Evacuate the coating chamber to a vacuum level of 3.0 × 10⁻⁶. -3 Above Pa, heat the vacuum coating chamber temperature to 400~500 ℃ and hold it at that temperature for 30 min; (3) Etching and cleaning: Turn on the etching Ti target and etch and clean the substrate in an Ar atmosphere; (4) Deposition of AlCrN transition layer: Introduce N2 and turn on AlCr target, deposition time is 30~35 min; (5) Deposit AlCrSiWN / Mo nanocomposite coating. The total deposition time is 100~130 min. The content of Mo element in the coating is controlled by adjusting the evaporation current of CrMo target. Finally, AlCrSiWN / Mo nanocomposite coating is obtained.

9. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 8, characterized in that: In step (3), the etching and cleaning process is as follows: after the vacuum coating chamber is heated and kept at a constant temperature for 30 minutes, Ar is introduced with an Ar flow rate of 150~300 sccm. The deposition pressure is controlled at 0.26~0.35 Pa, and the Ti target etching is turned on with a Ti target evaporation current of 120~140 A. The DC bias voltage is set to increase from -10 V to -180 V in a gradient. The etching and cleaning time is 60~90 minutes.

10. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 8, characterized in that: In step (4), after etching and cleaning, an AlCrN transition layer is deposited. During the deposition process, N2 with a flow rate of 1220~1280 sccm is introduced, the deposition pressure is 3.2~4.5 Pa, the AlCr target evaporation current is 120~140 A, and the bias voltage is -40~-60 V.

11. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 8, characterized in that: In step (5), when depositing the AlCrSiWN / Mo nanocomposite coating, the rotation speed of the rotating frame is 2.3 r / min to 3 r / min, the deposition pressure is 3.5 to 4 Pa, and the DC bias voltage is -120 to -160 V.

12. The preparation process of the AlCrSiWN / Mo nanocomposite coating with high hardness and high wear resistance according to claim 8, characterized in that: In step (5), when depositing the AlCrSiWN / Mo nanocomposite coating, as the Mo content increases, the diffraction peak of the t-Mo2N phase (220) crystal plane shifts to a higher angle.

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