A hard CrAlSiNO gradient composite coating and a method for preparing the same

Abstract

The present application relates to a kind of hard CrAlSiNO gradient composite coating and its preparation method, the gradient composite coating includes CrN primer layer (2) sequentially deposited on the surface of substrate (1), CrAlN transition layer (3), CrAlSiN intermediate layer (4) and CrAlSiNO layer (5), the total thickness of the gradient composite coating is 6.5 ~ 8.5 μm;The method is prepared gradient composite coating by cathodic arc ion plating process, including substrate (1) surface activation, CrN primer layer (2) preparation, CrAlN transition layer (3) preparation, CrAlSiN intermediate layer (4) preparation and CrAlSiNO layer (5) preparation.Compared with prior art, the gradient composite coating of the present application shows excellent high-temperature oxidation resistance, good mechanical properties and wear resistance, and the preparation method is simple, easy to implement, applied to high-temperature bearing makes the service life of high-temperature bearing further improve.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of mechanical friction protection and high-temperature protection, and relates to a hard CrAlSiNO gradient composite coating and a preparation method thereof. BACKGROUND

[0002] The changes in the organizational structure and composition of the friction surface of mechanical parts under high-temperature conditions, such as oxidation, phase change and element diffusion, cause the mechanical properties of the parts to decrease, resulting in a decrease in the service life of the parts and great safety hazards. At present, the improvement of the service life of bearings in high-temperature environments has always been a bottleneck. Nitride ceramic-based coatings are widely used in the field of mechanical parts and metal processing as protective layers due to their high hardness, good wear resistance and high-temperature stability. The ternary CrAlN coating formed by doping Al elements into the CrN lattice effectively improves the hardness and oxidation resistance temperature of the binary CrN coating due to solid solution strengthening and the generation of dense Al2O3 and Cr2O3 oxides at high temperatures, and is widely used. In recent years, with the complexity of application conditions, coated workpieces are often used in high-temperature (such as 1000℃) and high-load environments, and the ternary CrAlN coating cannot meet the demand.

[0003] In order to further improve the oxidation resistance, mechanical properties and tribological properties of the CrAlN coating, doping Si elements into the ternary CrAlN coating can effectively improve the mechanical properties of the original coating, but the internal stress is large, which accelerates the invasion of oxygen during high-temperature friction and causes the coating to be easily oxidized and fail. In addition, nitrogen molecules or weakly adsorbed nitrogen ions existing in the coating at high temperatures will be released along the grain boundaries and pinholes, resulting in a decrease in the tribological properties.

[0004] Patent CN109207938A discloses a Ti / TiN / TiAlSiN / TiAlCrSiN nano-multilayer gradient film and a preparation method thereof. The nano-multilayer gradient film is composed of a Ti primer layer, a TiN transition layer, a TiAlSiN transition layer and a TiAlCrSiN film layer deposited in sequence on a low-alloy steel or die steel substrate by a multi-arc ion plating method. The total thickness of the nano-multilayer gradient film is 1.8-3.6μm. The total content ranges of Ti, Al, Cr and Si elements are 30-34at%, 20-24at%, 5-10at% and 3-5at%, respectively. However, the coating prepared by the patent has a large internal stress and poor toughness, and microcracks are easily generated during fatigue wear, resulting in premature failure.

[0005] Patent CN114231901A discloses a CrAlSiN gradient composite coating and a preparation method thereof, and the steps of coating the CrAlSiN superhard gradient coating on the workpiece by cathodic arc ion plating process include four stages of preparing a Cr base layer, preparing a CrN adhesive layer, preparing a CrAlN transition layer and preparing a CrAlSiN surface layer in sequence, and polishing the coating surface after the coating is completed. However, the coating prepared by the patent has low hardness and poor wear resistance. SUMMARY

[0006] The purpose of the present application is to overcome at least one of the above-mentioned defects in the prior art and provide a hard CrAlSiNO gradient composite coating and a preparation method thereof. The gradient composite coating of the present application exhibits excellent high-temperature oxidation resistance, good mechanical properties and wear resistance, and the preparation method is simple and easy to implement. The application in high-temperature bearings further improves the service life of high-temperature bearings.

[0007] The purpose of the present application can be achieved by the following technical solutions:

[0008] One of the technical solutions of the present application is to provide a hard CrAlSiNO gradient composite coating, which comprises a CrN base layer, a CrAlN transition layer, a CrAlSiN intermediate layer and a CrAlSiNO layer deposited on the surface of the substrate in sequence. The total thickness of the gradient composite coating is 6.5-8.5pm.

[0009] Further, the thickness of the CrN base layer is 0.1-0.3pm, the thickness of the CrAlN transition layer is 0.15-0.45pm, the thickness of the CrAlSiN intermediate layer is 1.85-2.15pm, and the thickness of the CrAlSiNO layer is 4.4-5.6pm.

[0010] One of the technical solutions of the present application is to provide a preparation method of a hard CrAlSiNO gradient composite coating, which is prepared by a cathodic arc ion plating process, comprising the following steps:

[0011] (1) Substrate surface activation: pre-evacuation, set the furnace cavity temperature, introduce inert gas, set the Cr target current, connect the substrate to the voltage etching, and obtain an activated substrate surface;

[0012] (2) CrN base layer preparation: control the vacuum degree and the furnace cavity temperature, connect the Cr target current, introduce the reaction gas, and deposit to obtain a CrN base layer;

[0013] (3) CrAlN transition layer preparation: control the vacuum degree and the furnace cavity temperature, connect the CrAl target current, introduce the reaction gas, and deposit to obtain a CrAlN transition layer;

[0014] (4) CrAlSiN intermediate layer preparation: control vacuum degree and furnace cavity temperature, CrAl target access current, CrSi target access current, reaction gas, deposition, obtain CrAlSiN intermediate layer;

[0015] (5) CrAlSiNO layer preparation: control vacuum degree and furnace cavity temperature, CrAl target access current, CrSi target access current, reaction gas, deposition, obtain CrAlSiNO layer.

[0016] Further, the step (1) before the substrate pretreatment: polishing the substrate, ultrasonic oscillation, cleaning and then drying.

[0017] Further, the polishing mesh is 2400-3200 mesh, the ultrasonic oscillation time is 10-15 min, the cleaning time is 8-12 min, and the drying temperature is 60-65℃.

[0018] As a preferred technical solution, the polishing uses sandpaper or cotton cloth, the ultrasonic oscillation is carried out in acetone and ethanol in turn, and the cleaning uses water.

[0019] Further, the vacuum degree in step (1) is 8x10 -4 -2x10 -3 Pa, and the furnace cavity temperature is 400-450℃;

[0020] The inert gas flow is 170-200sccm;

[0021] The Cr target current is 100-130A;

[0022] The substrate voltage is -750--650V, and the etching time is 8-12min.

[0023] As a preferred technical solution, the inert gas in step (1) is argon.

[0024] Further, the vacuum degree in step (2) is 2x10 -2 -4x10 -2 Pa, and the furnace cavity temperature is 400-450℃;

[0025] The Cr target current is 120-140A;

[0026] The reaction gas is nitrogen, and the flow is 100-150sccm;

[0027] The deposition bias voltage is -120--100V, and the time is 10-15min.

[0028] Further, the vacuum degree in step (3) is 2x10 -2 -4x10-2 Pa, the furnace cavity temperature is 400-450 DEG C;

[0029] The CrAl target current is 110-130 A;

[0030] The reaction gas is nitrogen, and the flow rate is 130-170 sccm;

[0031] The deposition bias is -140--110 V, and the time is 12-18 min.

[0032] Further, the vacuum degree in step (4) is 2*10 -2 ~4*10 -2 Pa, the furnace cavity temperature is 400-450 DEG C;

[0033] The CrAl target current is 110-130 A, and the CrSi target current is 130-160 A;

[0034] The reaction gas is nitrogen, and the flow rate is 160-220 sccm;

[0035] The deposition bias is -130--100 V, and the time is 60-80 min.

[0036] Further, the vacuum degree in step (5) is 2*10 -2 ~4*10 -2 Pa, the furnace cavity temperature is 400-450 DEG C;

[0037] The CrAl target current is 150-180 A, and the CrSi target current is 170-200 A;

[0038] The reaction gas is nitrogen and oxygen, and the flow rates are 150-190 sccm and 20-45 sccm respectively;

[0039] The deposition bias is -150--120 V, and the time is 90-140 min.

[0040] The coating gradient design can reduce the thermal expansion coefficient difference between the interval layers, and the intermediate layer can play a moderating role; when receiving external impact or fatigue force, the intermediate layer plays a transition role, and the comprehensive performance of the coating can be effectively improved. Meanwhile, the nitride and the oxide are combined, the coating grain boundary is increased, the hindering effect on the intracrystalline dislocation is enhanced, the resistance to external force deformation ability is improved, and the hardness of the coating is increased.

[0041] Compared with the prior art, the present application has the following advantages:

[0042] (1) The gradient composite coating of the present application is obtained by reducing the superposition of the difference in the thermal expansion coefficient between layers, and by using the composite of nitride and oxide, so that the coating exhibits excellent high-temperature oxidation resistance, good mechanical properties and wear resistance;

[0043] (2) The preparation method of the present application is simple and easy to implement;

[0044] (3) The gradient composite coating of the present application has higher hardness, oxidation resistance and wear resistance compared with nitride coatings such as CrAlN and CrAlSiN, due to the composite of nitride and oxide;

[0045] (4) The gradient composite coating of the present application has higher hardness, oxidation resistance and wear resistance compared with nitride coatings such as TiAlN and TiAlSiN, due to the composite of nitride and oxide;

[0046] (5) The present application has obvious advantages in wear resistance, high-temperature resistance and high hardness, etc., and can significantly improve the service life of high-temperature bearings. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The structure of the hard CrAlSiNO gradient composite coating in the embodiment of the present application is shown in the figure.

[0048] Marking in the figure:

[0049] 1 - substrate, 2 - CrN undercoat layer, 3 - CrAlN transition layer, 4 - CrAlSiN intermediate layer, 5 - CrAlSiNO layer. DETAILED DESCRIPTION

[0050] The present application will be described in detail below in conjunction with specific embodiments. The present embodiment is implemented on the basis of the technical solution of the present application, and detailed implementation and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0051] The equipment used in the following embodiments is conventional in the art unless otherwise specified; the reagents used are commercially available or prepared by conventional methods in the art unless otherwise specified; and the following embodiments are implemented by conventional experimental means in the art.

[0052] The Cr target, CrAl target and CrSi target used in this embodiment have a purity of greater than 99.8%.

[0053] Example 1:

[0054] A hard CrAlSiNO gradient composite coating and a preparation method thereof, the specific steps are as follows:

[0055] (1) Substrate 1 pretreatment: The substrate 1 polished with 3000 mesh sandpaper was sequentially ultrasonically oscillated in acetone, anhydrous ethanol for 12 min, washed with deionized water for 10 min, and then placed in a 65°C drying oven for drying;

[0056] (2) Substrate 1 surface activation: The vacuum was pre-extracted to 9x10 -4 Pa, the furnace cavity temperature was 420°C, 170 sccm of argon was introduced, the Cr target current was 100 A, the substrate was connected to a voltage of -650 V for etching for 9 min, and an activated substrate 1 surface was obtained;

[0057] (3) CrN primer layer 2 preparation: The vacuum degree was 2x10 -2 Pa, the furnace cavity temperature was 420°C, the Cr target was connected to a current of 130 A, 150 sccm of nitrogen was introduced, and a CrN primer layer 2 was obtained by deposition under a bias voltage of -120 V for 10 min;

[0058] (4) CrAlN transition layer 3 preparation: The vacuum degree was 2x10 -2 Pa, the furnace cavity temperature was 420°C, the CrAl target was connected to a current of 130 A, 170 sccm of nitrogen was introduced, and a CrAlN transition layer 3 was obtained by deposition under a bias voltage of -140 V for 12 min;

[0059] (5) CrAlSiN intermediate layer 4 preparation: The vacuum degree was 2x10 -2 Pa, the furnace cavity temperature was 420°C, the CrAl target was connected to a current of 130 A, the CrSi target was connected to a current of 150 A, 200 sccm of nitrogen was introduced, and a CrAlSiN intermediate layer 4 was obtained by deposition under a bias voltage of -120 V for 65 min;

[0060] (6) CrAlSiNO layer 5 preparation: The vacuum degree was 2x10 -2 Pa, the furnace cavity temperature was 420°C, the CrAl target was connected to a current of 150 A, the CrSi target was connected to a current of 200 A, 190 sccm of nitrogen and 20 sccm of oxygen were introduced, and a CrAlSiNO layer 5 was obtained by deposition under a bias voltage of -140 V for 110 min.

[0061] As Figure 1As shown, the CrAlSiNO gradient composite coating prepared in the embodiment is composed of four layers of CrN primer layer 2, CrAlN transition layer 3, CrAlSiN intermediate layer 4 and CrAlSiNO layer 5 deposited on the surface of substrate 1 in sequence, and follows the principle of gradually reducing the difference in thermal expansion coefficient. The total thickness of the gradient composite coating is 7.2 μm, the thickness of the CrN primer layer 2 is 0.2 μm, the thickness of the CrAlN transition layer 3 is 0.3 μm, the thickness of the CrAlSiN intermediate layer 4 is 1.9 μm, and the thickness of the CrAlSiNO layer 5 is 4.8 μm. In addition, the coating is composed of nitrides and oxides, and exhibits high hardness, excellent high-temperature oxidation resistance and wear resistance.

[0062] Example 2:

[0063] A hard CrAlSiNO gradient composite coating and a preparation method thereof, the specific steps are as follows:

[0064] (1) Substrate 1 pretreatment: the substrate polished with 2800 mesh sandpaper is sequentially ultrasonically oscillated in acetone and anhydrous ethanol for 15 min, washed with deionized water for 9 min, and then placed in a 60°C drying box for drying;

[0065] (2) Surface activation of substrate 1: pre-evacuate to 8×10 -4 Pa, the furnace cavity temperature is 450°C, 180sccm of argon is introduced, the Cr target current is 100A, the substrate is connected to a voltage of -700V for etching for 12 min, and an activated substrate 1 surface is obtained;

[0066] (3) Preparation of CrN primer layer 2: vacuum degree 4×10 -2 Pa, the furnace cavity temperature is 450°C, the Cr target is connected to a current of 120A, 110sccm of nitrogen is introduced, and the CrN primer layer 2 is obtained by deposition under a bias voltage of -110V for 13 min;

[0067] (4) Preparation of CrAlN transition layer 3: vacuum degree 4×10 -2 Pa, the furnace cavity temperature is 450°C, the CrAl target is connected to a current of 130A, 160sccm of nitrogen is introduced, and the CrAlN transition layer 3 is obtained by deposition under a bias voltage of -125V for 15 min;

[0068] (5) Preparation of CrAlSiN intermediate layer 4: vacuum degree 4×10 -2 Pa, the furnace cavity temperature is 450°C, the CrAl target is connected to a current of 120A, the CrSi target is connected to a current of 150A, 190sccm of nitrogen is introduced, and the CrAlSiN intermediate layer 4 is obtained by deposition under a bias voltage of -120V for 70 min;

[0069] (6) Preparation of CrAlSiNO layer 5: vacuum degree 4×10-2 Pa, furnace cavity temperature 450°C, CrAl target connected to 165A current, CrSi target connected to 185A current, 180sccm of nitrogen and 25sccm of oxygen were introduced, and the CrAlSiNO layer 5 was deposited under a bias of -150V for 120min.

[0070] As shown in Figure 1 the CrAlSiNO gradient composite coating prepared in the embodiment is composed of four layers of CrN primer layer 2, CrAlN transition layer 3, CrAlSiN intermediate layer 4 and CrAlSiNO layer 5 deposited on the surface of the substrate 1 in sequence, and the principle of gradually reducing the difference in thermal expansion coefficient is followed. The total thickness of the gradient composite coating is 7.7μm, the thickness of the CrN primer layer 2 is 0.24μm, the thickness of the CrAlN transition layer 3 is 0.36μm, the thickness of the CrAlSiN intermediate layer 4 is 1.95μm, and the thickness of the CrAlSiNO layer 5 is 5.15μm. In addition, the coating is composed of nitrides and oxides, and exhibits high hardness, excellent high-temperature oxidation resistance and wear resistance.

[0071] Comparative Example 1:

[0072] A CrAlSiN gradient composite coating, the preparation method is basically the same as steps (1) to (5) in Example 1, except that the deposition time of step (5) is 180min, and the total thickness of the gradient composite coating is 7.2μm.

[0073] Application of a gradient composite coating, coated on a bearing, the following tests are based on high-temperature bearing workpieces.

[0074] Hardness test of a gradient composite coating, the specific steps are as follows:

[0075] The nano-hardness and Young's modulus of the coating were tested and calculated by using Hysitron Ti-950 nanoindenter, and the continuous stiffness indentation mode was selected, and the loading force was 15mN. At the same time, in order to ensure the accuracy of the hardness of the coating, the indentation depth is not more than 1 / 10 of the thickness of the coating.

[0076] The hardness of the CrAlSiN coating is 41.21±2.45GPa, and the hardness of the CrAlSiNO coating is 48.43±2.65GPa. Compared with Comparative Example 1, Example 1 has higher hardness due to the combination of nitrides and oxides.

[0077] Wear resistance test of a gradient composite coating, the specific steps are as follows:

[0078] UMT-3 friction tester under atmospheric environment was used to test the tribological properties of the coating, the friction mode was ball-disc type, the diameter of Si3N4 ceramic ball was 9.5mm, the load was 10N, the rotation speed was 200r / min, the diameter of the wear scar was 10mm, and the friction time was 10min. Contour GT-K0 white light interferometer was used to measure the wear volume of the coating, and the wear rate of the coating was calculated according to the formula W=V / FS, wherein V was the wear volume, F was the load, and S was the friction distance.

[0079] The friction coefficient of the CrAlSiN coating was 0.31, and the wear rate was 2.8*10 -5 mm 3 / (N*m), and the friction coefficient of the CrAlSiNO coating was 0.26, and the wear rate was 1.4*10 -5 mm 3 / (N*m). Compared with Comparative Example 1, Example 1 had higher wear resistance due to the combination of nitride and oxide.

[0080] The oxidation resistance of a gradient composite coating was tested, and the specific steps were as follows:

[0081] A muffle furnace (SX-10-120, China) was used for heat treatment of the coating, and the muffle furnace cavity was heated to 800 DEG C and 1000 DEG C respectively, and then the high-temperature workpiece was placed in the furnace cavity with the tray, and the temperature was kept for 120 min, and the furnace was cooled.

[0082] The oxidation depth of the CrAlSiN coating at 800 DEG C was 1.8μm, and the oxidation depth at 1000 DEG C was 5.3μm, while the oxidation depth of the CrAlSiNO coating at 800 DEG C was 0.2μm, and the oxidation depth at 1000 DEG C was 1.5μm. Compared with Comparative Example 1, Example 1 had higher oxidation resistance due to the combination of nitride and oxide.

[0083] Comparative Example 2:

[0084] A TiAlSiN gradient composite coating, the preparation method was basically the same as steps (1) to (5) in Example 1, except that Cr element was replaced by corresponding Ti element, the deposition time of step (5) was 180min, and the total thickness of the gradient composite coating was 6.9μm.

[0085] The application of a gradient composite coating was applied to a bearing, and the following tests were based on high-temperature bearing workpieces.

[0086] The hardness test of a gradient composite coating, the specific steps were as follows:

[0087] The nano-hardness and Young's modulus of the coating were tested and calculated by using Hysitron Ti-950 nanoindenter. The continuous stiffness indentation mode was selected, and the loading force was 15 mN. At the same time, in order to ensure the accuracy of the hardness of the coating, the indentation depth was not more than 1 / 10 of the thickness of the coating.

[0088] The hardness of the TiAlSiN coating was 43.21±2.19 GPa, and the hardness of the CrAlSiNO coating was 48.43±2.65 GPa. Compared with Comparative Example 2, Example 1 had higher hardness due to the combination of nitride and oxide.

[0089] The wear resistance of a gradient composite coating was tested, and the specific steps were as follows:

[0090] The UMT-3 friction tester was used to test the tribological properties of the coating in the atmospheric environment. The friction mode was ball-disc type, the diameter of the Si3N4 ceramic ball was 9.5 mm, the load was 10 N, the rotation speed was 200 r / min, the wear scar diameter was 10 mm, and the friction time was 10 min. The Contour GT-K0 white light interferometer was used to measure the wear volume of the coating, and the wear rate of the coating was calculated according to the formula W=V / FS, wherein V was the wear volume, F was the load, and S was the friction distance.

[0091] The friction coefficient of the TiAlSiN coating was 0.32, and the wear rate was 3.2×10 -5 mm 3 / (N·m), and the friction coefficient of the CrAlSiNO coating was 0.26, and the wear rate was 1.4×10 -5 mm 3 / (N·m). Compared with Comparative Example 2, Example 1 had higher wear resistance due to the combination of nitride and oxide.

[0092] The oxidation resistance of a gradient composite coating was tested, and the specific steps were as follows:

[0093] The coating was heat treated by using a muffle furnace (SX-10-120, China). The muffle furnace cavity was heated to 800°C and 1000°C respectively, and then the high-temperature workpiece was placed in the furnace cavity with the tray, and the temperature was kept for 120 min and the furnace was cooled.

[0094] The oxidation depth of the TiAlSiN coating at 800°C was 2.1 μm, and the coating was completely oxidized at 1000°C. The oxidation depth of the CrAlSiNO coating at 800°C was 0.2 μm, and the oxidation depth at 1000°C was 1.5 μm. Compared with Comparative Example 2, Example 1 had higher oxidation resistance due to the combination of nitride and oxide.

[0095] The foregoing description of the embodiments has been presented for the purpose of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed. Modifications and variations are possible in light of the above teachings or can be acquired from practice of the application. As well, the description is presented in the context of the preferred embodiments as a number of alternatives. It is not intended to limit the application to the precise form described.

Claims

1. A hard CrAlSiNO gradient composite coating, characterized in that, The gradient composite coating is applied to a high-temperature bearing, and the gradient composite coating comprises a CrN primer layer (2), a CrAlN transition layer (3), a CrAlSiN intermediate layer (4) and a CrAlSiNO layer (5) deposited on the surface of a substrate (1) in sequence, and the total thickness of the gradient composite coating is 6.5-8.5 microns; The thickness of the CrN primer layer (2) is 0.1-0.3 microns, the thickness of the CrAlN transition layer (3) is 0.15-0.45 microns, the thickness of the CrAlSiN intermediate layer (4) is 1.85-2.15 microns, and the thickness of the CrAlSiNO layer (5) is 4.4-5.6 microns; When the CrN primer layer (2) is prepared, the Cr target current is 120-140 A; The reaction gas is nitrogen, and the flow rate is 100-150 sccm; The deposition bias is -120 to -100 V, and the time is 10-15 min; When the CrAlN transition layer (3) is prepared, the CrAl target current is 110-130 A; The reaction gas is nitrogen, and the flow rate is 130-170 sccm; The deposition bias is -140 to -110 V, and the time is 12-18 min; When the CrAlSiN intermediate layer (4) is prepared, the CrAl target current is 110-130 A, and the CrSi target current is 130-160 A; The reaction gas is nitrogen, and the flow rate is 160-220 sccm; The deposition bias is -130 to -100 V, and the time is 60-80 min; When the CrAlSiNO layer (5) is prepared, the CrAl target current is 150-180 A, and the CrSi target current is 170-200 A; The reaction gas is nitrogen and oxygen, and the flow rates are 150-190 sccm and 20-45 sccm, respectively; The deposition bias is -150 to -120 V, and the time is 90-140 min.

2. A method of producing a hard CrAlSiNO gradient composite coating according to claim 1, characterized in that The method for preparing the gradient composite coating by a cathodic arc ion plating process comprises the following steps: (1) Surface activation of the substrate (1): pre-evacuation, setting the furnace cavity temperature, introducing inert gas, setting the Cr target current, connecting the substrate (1) to the voltage etching, and obtaining the activated surface of the substrate (1); (2) Preparation of the CrN primer layer (2): controlling the vacuum degree and the furnace cavity temperature, connecting the Cr target to the current, introducing the reaction gas, and depositing to obtain the CrN primer layer (2); (3) Preparation of the CrAlN transition layer (3): controlling the vacuum degree and the furnace cavity temperature, connecting the CrAl target to the current, introducing the reaction gas, and depositing to obtain the CrAlN transition layer (3); (4) Preparation of the CrAlSiN intermediate layer (4): controlling the vacuum degree and the furnace cavity temperature, connecting the CrAl target to the current, connecting the CrSi target to the current, introducing the reaction gas, and depositing to obtain the CrAlSiN intermediate layer (4); (5) Preparation of CrAlSiNO layer (5): control the vacuum degree and furnace cavity temperature, connect the CrAl target with current, connect the CrSi target with current, input the reaction gas, deposit, and obtain the CrAlSiNO layer (5).

3. The method according to claim 2, wherein the method is characterized in that Step (1) Pretreatment of the front substrate (1): polish the substrate (1), ultrasonic oscillation, clean and then dry.

4. The method according to claim 3, wherein the method is characterized by, The polishing mesh number is 2400-3200 mesh, the ultrasonic oscillation time is 10-15 min, the cleaning time is 8-12 min, and the drying temperature is 60-65 ℃.

5. The method of claim 2, wherein the hard CrAlSiNO gradient composite coating is prepared by a method comprising: depositing a CrAlSiN layer on a substrate; and depositing a CrAlSiO layer on the CrAlSiN layer. The vacuum degree in step (1) is 8×10 -4 ~2×10 -3 Pa, furnace cavity temperature is 400~450 ℃; The inert gas flow is 170-200 sccm; The Cr target current is 100-130 A; The substrate voltage is -750 to -650 V, and the etching time is 8-12 min.

6. The method of claim 2, wherein the hard CrAlSiNO gradient composite coating is prepared by a method comprising: The vacuum degree in steps (2) to (5) is 2x10 -2 Pa, and the furnace cavity temperature is 400-450 ℃. -2 Pa, and the furnace cavity temperature is 400-450 ℃.

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