A cold-sprayed nickel-based titanium-aluminum-carbon composite coating, a preparation method and application thereof

Abstract

The present application belongs to the technical field of composite coating, and particularly relates to a cold sprayed nickel-based titanium-aluminum-carbon composite coating, a preparation method and application thereof. The nickel-based titanium-aluminum-carbon composite coating prepared by cold spraying has low porosity, dense coating, high hardness, good bonding strength, good mechanical properties, excellent wear resistance, and can replace the cylinder liner and bearing bush parts in the equipment engine for use in severe working conditions, so as to realize the lightweight and full-aluminum of the equipment engine, and improve the overall performance of the equipment engine.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of composite coating, and particularly relates to a cold sprayed nickel-based titanium aluminum carbon composite coating and a preparation method and application thereof. BACKGROUND

[0002] Heavy equipment such as aircraft, ships, tanks and cars plays a vital role in the fields of aerospace, mechanical manufacturing and military. However, due to the large size and heavy weight of the heavy equipment, the overall performance is severely limited. Equipment lightening is an important development trend in the current industrial manufacturing field, especially the equipment engine as the heart of the car accounts for a considerable proportion in terms of size and weight. The engine is usually cast with heavy gray cast iron material, and its own weight seriously limits the overall performance improvement.

[0003] Although aluminum alloy has been widely used in existing automobile engines, the key components that directly bear friction and gas impact must be embedded with higher strength and larger specific gravity bushings, bearing bushings and other "local reinforcement" or use expensive and heavy steel materials as a whole to adapt to severe and complex working conditions. This forced embedded combination design not only reduces the "all-aluminum, lightweight" level of the equipment engine, but also may cause serious failure problems such as mismatching of the embedded interface, water leakage, abnormal noise and deformation, which poses a great safety hazard.

[0004] Typical components such as engine bearing seat and cylinder wall are made of aluminum alloy material. Due to the low surface hardness, high friction coefficient and poor wear resistance, they have to be designed in an embedded combination with steel bearing bushings and cast iron cylinder liners to reduce problems such as wear, corrosion and scratching. The cast iron and steel materials improve the wear resistance of the cylinder wall and bearing seat to some extent due to their sufficient hardness, but increase the overall weight of the engine. In addition, the thermal conductivity coefficients of cast iron and steel materials are quite different from that of aluminum alloy, which can easily cause deformation and wear of the cylinder body and bearing seat, and seriously affect the performance and service life of the engine. SUMMARY

[0005] Therefore, the present application aims to provide a cold sprayed nickel-based titanium aluminum carbon composite coating and a preparation method and application thereof. The cold sprayed nickel-based titanium aluminum carbon composite coating prepared by the present application is dense, has high hardness, good bonding strength, excellent mechanical properties and wear resistance, and can replace the cylinder liner and bearing bushing components in the equipment engine for use under severe working conditions, thereby achieving lightweight and all-aluminum of the equipment engine and improving the overall performance of the equipment engine.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions.

[0007] The present application provides a preparation method of a cold sprayed nickel-based titanium aluminum carbon composite coating, comprising the following steps:

[0008] The cold spraying of the composite powder on the surface of the pretreated base material obtains a cold sprayed nickel-based titanium aluminum carbon composite coating;

[0009] The composite powder comprises Ni powder and Ti3AlC2 powder.

[0010] The base material is an aluminum alloy.

[0011] Preferably, the mass ratio of the Ni powder to the Ti3AlC2 powder is (5-8):(2-5).

[0012] Preferably, the parameters of the cold spraying include that the powder feeding gas is nitrogen, the spraying pressure is 3-5 MPa, the spraying temperature is 500-700 DEG C, the spraying distance is 10-20 mm, the powder feeding rate is 3-4 r / min, the spraying angle is 90 DEG, the reciprocating frequency of the spraying gun is 8-12 times, and the speed of the spraying gun is 300-400 mm / s.

[0013] Preferably, the average particle size of the Ni powder is 10-50 mu m, and the average particle size of the Ti3AlC2 powder is 10-50 mu m.

[0014] Preferably, the Ni powder comprises spherical particles and irregularly shaped particles, and the Ti3AlC2 powder is irregularly layered polygonal.

[0015] Preferably, the pretreatment comprises sequentially performing first ultrasonic cleaning, first drying, sand blasting roughening treatment, second ultrasonic cleaning and second drying on the base material.

[0016] Preferably, the particle size of the sand used in the sand blasting roughening treatment is 500-700 mu m, the sand blasting angle of the sand blasting roughening treatment is 70-80 DEG, the sand blasting distance is 180-240 mm, and the pressure is 0.7-0.8 MPa; the roughness Sq of the surface of the base material after the sand blasting roughening treatment is 10-12.8 mu m, and the roughness Sa is 5-7.81 mu m.

[0017] Preferably, the cleaning liquid used in the first ultrasonic cleaning and the second ultrasonic cleaning is anhydrous ethanol; and the frequency of the first ultrasonic cleaning and the second ultrasonic cleaning is independently 28-40 kHz, and the time is independently 5-10 min.

[0018] The application further provides a cold sprayed nickel-based titanium aluminum carbon composite coating prepared by the preparation method. 0.2 .

[0019] The application further provides application of the cold sprayed nickel-based titanium aluminum carbon composite coating in a light-weight engine.

[0020] The application provides a preparation method of a cold sprayed nickel-based titanium aluminum carbon composite coating, comprising the following steps: cold spraying a composite powder on a surface of a pretreated base material to obtain the cold sprayed nickel-based titanium aluminum carbon composite coating; the composite powder comprises Ni powder and Ti3AlC2 powder; and the base material is an aluminum alloy. During the cold spraying process, the composite powder is deformed, the base material is also plastically deformed to a certain degree after being subjected to a great impact, the interface is relatively blurred, the coating and the base material interface are embedded in each other in a wave shape, a strong combination is formed between the coating and the base material in a mechanical combination mode, the shot peening effect of the Ti3AlC2 ceramic particles, the Ni particles become flat or irregular, the Ti3AlC2 is a ceramic material and cannot be deformed, and the Ti3AlC2 is directly deposited in the coating, the Ni particles are compacted, the deformation of the Ni particles is promoted, the coating density is improved, and the porosity is reduced; in addition, the particles of the composite powder are subjected to severe plastic deformation during the impact process, a work hardening effect is caused, and the internal stress of the coating, especially the compressive stress, and the dislocation density at the grain boundary are increased, so that the hardness of the coating is improved. Therefore, the nickel-based titanium aluminum carbon composite coating prepared by the cold spraying method has low porosity, dense coating, high hardness, good combination strength, good mechanical properties, excellent wear resistance, can replace the cylinder sleeve and bearing parts in the engine under severe working conditions, can realize the light-weight full-aluminumization of the engine, and can improve the overall performance of the engine. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The figure is the morphology and particle size diagram of the Ni powder used in example 1 of the application;

[0022] Figure 2 The figure is the morphology and particle size diagram of the Ti3AlC2 powder used in example 1 of the application;

[0023] Figure 3 The figure is a cold spraying equipment used in example 1 of the application;

[0024] Figure 4 The figure is the morphology and particle size diagram of the composite powder in example 1 of the application;

[0025] Figure 5 The figure is the morphology and EDS analysis diagram of the composite powder in example 1 of the application;

[0026] Figure 6 The figure is the XRD diffraction diagram of the surface of the Ni-Ti3AlC2 composite coating in examples 1-3 of the application;

[0027] Figure 7 The surface scanning topography of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0028] Figure 8 The cross-section micro-morphology of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0029] Figure 9 The cross-section morphology and EDS analysis of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0030] Figure 10 The porosity and Ti3AlC2 ceramic content of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0031] Figure 11 The hardness change curve of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0032] Figure 12 The elastic modulus of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0033] Figure 13 The indentation morphology of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application under 0.01Kgf load;

[0034] Figure 14 The bonding strength of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0035] Figure 15 The macroscopic fracture morphology of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0036] Figure 16 The tensile fracture morphology of the Ni-Ti3AlC2 composite coating prepared in the different mass ratios in the embodiments 1-3 of the application;

[0037] Figure 17 The wear test result of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coating prepared in the embodiments 1-3 under dry friction condition;

[0038] Figure 18 The wear scar three-dimensional morphology of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coating prepared in the embodiments 1-3;

[0039] Figure 19 SEM scan of the wear track of the aluminum alloy substrate after dry friction test;

[0040] Figure 20 SEM scan of the wear track of the aluminum alloy substrate after dry friction test;

[0041] Figure 21 SEM scan of the wear track of the cold sprayed Ni-20% Ti3AlC2 coating in Example 1 after dry friction test;

[0042] Figure 22 SEM scan of the wear track of the cold sprayed Ni-40% Ti3AlC2 coating in Example 2 after dry friction test;

[0043] Figure 23 SEM scan of the wear track of the cold sprayed Ni-50% Ti3AlC2 coating in Example 3 after dry friction test;

[0044] Figure 24 Wear test results of the aluminum alloy substrate and the cold sprayed Ni-Ti3AlC2 coatings in Examples 1-3 under oil lubrication;

[0045] Figure 25 Three-dimensional morphology of the wear track of the aluminum alloy substrate and the cold sprayed Ni-Ti3AlC2 coatings in Examples 1-3 under oil lubrication;

[0046] Figure 26 Three-dimensional morphology of the wear track of the aluminum alloy substrate and the cold sprayed Ni-Ti3AlC2 coatings in Examples 1-3 under oil lubrication;

[0047] Figure 27 Morphology of the wear track of the aluminum alloy substrate after 30 min of friction and wear under oil lubrication;

[0048] Figure 28 Morphology of the wear track of the Ni-20% Ti3AlC2 coating after 30 min of friction and wear under oil lubrication;

[0049] Figure 29 Morphology of the wear track of the Ni-40% Ti3AlC2 coating after 30 min of friction and wear under oil lubrication;

[0050] Figure 30 Morphology of the wear track of the Ni-50% Ti3AlC2 coating after 30 min of friction and wear under oil lubrication;

[0051] Figure 31 Schematic diagram of the indentation method;

[0052] Figure 32 Figure 1 is a schematic diagram of a coating bonding strength test;

[0053] Figure 33 Figure 4 is a schematic diagram of a dry friction principle. DETAILED DESCRIPTION

[0054] The application provides a preparation method of a cold sprayed nickel-based titanium aluminum carbon composite coating.

[0055] The cold sprayed nickel-based titanium aluminum carbon composite coating is obtained by cold spraying of the composite powder on the surface of the pretreated base material.

[0056] The composite powder comprises Ni powder and Ti3AlC2 powder.

[0057] The base material is an aluminum alloy.

[0058] Unless otherwise specified, the application does not have special requirements for the source of the raw materials used for preparation, and commercially available goods known to those skilled in the art can be used.

[0059] The cold sprayed nickel-based titanium aluminum carbon composite coating is obtained by cold spraying of the composite powder on the surface of the pretreated base material.

[0060] In the application, the base material is an aluminum alloy, preferably an ADC12 aluminum alloy.

[0061] In the application, the chemical composition of the ADC12 aluminum alloy is shown in Table 1.

[0062] Table 1 Chemical composition of ADC12 aluminum alloy

[0063] Chemical composition Si Fe Cu Mn Mg Ni Sn Zn Al Content / % 9.6-12 ≤1.3 ≤1.5-3.5 ≤0.5 ≤0.3 ≤0.5 ≤0.3 ≤1.0 Balance

[0064] In this invention, the pretreatment preferably includes: sequentially subjecting the matrix material to a first ultrasonic cleaning, a first drying, a sandblasting roughening treatment, a second ultrasonic cleaning, and a second drying. In this invention, the cleaning solution used for the first and second ultrasonic cleaning is preferably anhydrous ethanol; the power of the first and second ultrasonic cleaning is preferably 28–40 kHz, more preferably 35–40 kHz, and the time is preferably 5–10 min, more preferably 10 min; the particle size of the abrasive used in the sandblasting roughening treatment is preferably 500–700 μm, more preferably 550–650 μm; the abrasive used in the sandblasting roughening treatment is preferably brown corundum abrasive; and the sandblasting angle of the sandblasting roughening treatment is preferably 70–80°, more preferably... The blasting angle is 75°, the blasting distance is preferably 180-240 mm, more preferably 200-220 mm, and the pressure is preferably 0.7-0.8 MPa, more preferably 0.7 MPa; the surface roughness Sq of the substrate material after the blasting roughening treatment is preferably 10-12.8 μm, more preferably 10-11 μm, and the surface roughness Sa is preferably 5-7.81 μm, more preferably 6-7.5 μm; the first drying and the second drying are preferably carried out independently at 60-80°C, more preferably 70-80°C, and the time is preferably 2-5 min, more preferably 3-4 min.

[0065] This invention employs a first ultrasonic cleaning process to remove grease, rust, and other contaminants from the substrate material surface. Sandblasting further roughens the substrate material surface, providing a larger contact area with the coating and facilitating mechanical interlocking, thus resulting in a stronger bond between the substrate material and the coating. A second ultrasonic cleaning process removes stains and residual sand particles from the substrate material surface. This pretreatment creates a clean, rough surface on the substrate material, increasing the mechanical interlocking force between the sprayed particles and the substrate surface, thereby improving the bonding strength.

[0066] In this invention, the Ni powder preferably comprises spherical particles and irregularly shaped particles; the Ti3AlC2 powder preferably has an irregular layered polygonal morphology; the average particle size of the Ni powder is preferably 10-50 μm, more preferably 20-40 μm; the average particle size of the Ti3AlC2 powder is preferably 10-50 μm, more preferably 20-40 μm; the purity of the Ni powder is preferably ≥99.5%, more preferably ≥99.8%; the purity of the Ti3AlC2 powder is preferably ≥98%, more preferably 98%; the mass ratio of the Ni powder to the Ti3AlC2 powder is preferably (5-8):(2-5), more preferably (5-6):(4-5).

[0067] In this invention, the physical properties of the composite powder are shown in Table 2.

[0068] Table 2 Physical properties of composite powder particles

[0069]

[0070] In this invention, the preferred method for preparing the composite powder is as follows: the Ni powder and Ti3AlC2 powder are mechanically mixed and dried sequentially; the mechanical mixing time is preferably 20-40 min, more preferably 30 min; the mechanical mixing is preferably carried out under mechanical stirring conditions; the mechanical stirring speed is preferably 400-500 rpm, more preferably 450 rpm; the drying is preferably oven drying; the drying temperature is preferably 70-90℃, more preferably 70-80℃; the drying time is preferably 20-40 min, more preferably 30 min.

[0071] This invention uses mechanical mixing to uniformly mix Ni powder and Ti3AlC2 powder, resulting in a composite powder with uniform composition. Drying prevents the composite powder from being affected by moisture, thus ensuring its spray flowability. Furthermore, during the mechanical mixing process, the powders of different phases retain their original shape and do not react with each other, preserving the original physical and chemical properties of the powder material. This is crucial for the performance of the subsequent deposited coating.

[0072] In this invention, the parameters of the cold spraying include: the powder feeding gas is preferably nitrogen, the spraying pressure is preferably 3-5 MPa, more preferably 5 MPa, the spraying temperature is preferably 500-700℃, more preferably 700℃, the spraying distance is preferably 10-20 mm, more preferably 20 mm, the powder feeding rate is preferably 3-4 r / min, more preferably 3.5 r / min, the spraying angle is preferably 90°, the number of reciprocating strokes of the spray gun is preferably 8-12 times, more preferably 10-12 times, and the spray gun speed is preferably 300-400 mm / s, more preferably 300 mm / s.

[0073] In this invention, the equipment used for cold spraying is preferably the PCS-1000 cold spraying equipment manufactured by PlasmaGiken Co., Ltd. of Japan. This equipment mainly includes five parts: spray gun, power supply, control cabinet, heat exchanger and powder feeder.

[0074] In cold spraying, spraying pressure and spraying temperature are the most critical parameters, as they have the most significant impact on particle velocity. Increasing spraying pressure and temperature both increase the velocity and temperature of the powder particles. Increased particle velocity leads to greater kinetic energy during particle impact, while increased particle temperature softens the particles and reduces deformation resistance. The combined effect of these two factors improves the microstructure and density of the cold spray coating, directly determining the deposition process of the composite powder and the final coating performance.

[0075] The inter-particle bonding of cold sprayed coating is mainly dependent on the kinetic energy during particle impact and the deformation capability of the particles themselves. The increase of spraying temperature improves the deformation capability of the powder particle material upon impact, resulting in a tightly bonded coating with low porosity and better microstructure morphology.

[0076] The cold spraying pressure is also a key parameter in the cold spraying process, directly affecting the impact velocity and deformation behavior of the particles, and thus having an important influence on the quality and performance of the deposited layer. Lower spraying pressure can result in insufficient plastic deformation of the particles to fill surface defects and voids, thereby forming higher porosity. On the contrary, higher spraying pressure can increase the velocity and kinetic energy of the powder particles, producing higher energy upon impact with the substrate surface, which is beneficial for particle melting and fusion, promoting densification of the coating and reducing porosity. At the same time, it also enhances the bonding process at the particle-substrate and particle-particle contact points. Therefore, appropriate cold spraying pressure helps to form a dense and uniform coating structure, thereby reducing porosity and also improving the metallurgical bonding of the coating with the substrate, enhancing the adhesion of the coating.

[0077] The present application also provides a cold sprayed nickel-based titanium aluminum carbon composite coating prepared by the preparation method described in the above technical solution.

[0078] In the present application, the chemical composition includes Ni and Ti3AlC2; the thickness of the cold sprayed nickel-based titanium aluminum carbon composite coating is 500-800 μm, preferably 600-700 μm, the porosity is 0.3-0.6%, preferably 0.4-0.5%, and the hardness is 242-310 HV 0.2 , preferably 250-300 HV 0.2 .

[0079] The present application also provides the application of the cold sprayed nickel-based titanium aluminum carbon composite coating described in the above technical solution in lightweight engine equipment.

[0080] The application of the cold sprayed nickel-based titanium aluminum carbon composite coating in lightweight engine equipment is not specially limited in the present application, and can be applied in a manner well known in the art.

[0081] The technical solutions in the present application will be described clearly and completely below in conjunction with the embodiments in the present application, but they should not be understood as limiting the scope of protection of the present application.

[0082] Example 1

[0083] The ADC12 aluminum alloy is ultrasonically cleaned in anhydrous ethanol at 30 kHz for 10 min, dried at 80°C for 5 min, sandblasted with brown corundum sand particles (particle size of 500-700 pm) at a sandblasting angle of 75°, a sandblasting distance of 220 mm, and a pressure of 0.7 MPa, and finally ultrasonically cleaned in anhydrous ethanol at 30 kHz for 10 min and dried at 80°C for 5 min to obtain the pretreated ADC12 aluminum alloy;

[0084] The Ni powder (particle size of 10-50 pm, purity of 99.8%) and the Ti3AlC2 powder (particle size of 10-50 pm, purity of 98%) are mechanically stirred at a mass ratio of 8:2 at 450 rpm for 30 min, uniformly mixed, and dried at 70°C for 30 min to obtain a composite powder; the SEM images and particle size distribution of the Ni powder and the Ti3AlC2 powder are shown in Figure 1 and 2 The Ni powder is manufactured by a gas atomization process, most of the sprayed powder is spherical, and a small amount is irregular in shape, so that the powder has good fluidity, the spherical powder surface is smooth and has good sphericity, but a few small satellite-shaped particles are attached, which is a common phenomenon in the gas atomization powder manufacturing process and is a typical feature of the gas atomization process. The Ti3AlC2 powder is irregularly layered and polygonal in shape, which is more conducive to increasing the spraying deposition effect, improving the density of the coating, and reducing the porosity.

[0085] The composite powder is cold sprayed on the surface of the pretreated ADC12 aluminum alloy, and the equipment used is preferably a PCS-1000 cold spraying device produced by Plasma Giken Co., Ltd., Japan (as shown in Figure 3 The device mainly includes a spray gun, a power supply, a control cabinet, a heat exchanger, and a powder feeder, and the conditions are that the powder feeding gas is preferably nitrogen, the spraying pressure is 5 MPa, the spraying temperature is 700°C, the spraying distance is 20 mm, the powder feeding rate is 3.5 r / min, the spraying angle is 90°, the spray gun reciprocation frequency is 12 times, and the spray gun speed is 300 mm / s. A cold sprayed nickel-based titanium aluminum carbon composite coating with a thickness of 600 pm is obtained.

[0086] Example 2

[0087] The difference from Example 1 is that the mass ratio of the Ni powder and the Ti3AlC2 powder is 6:4, and the rest is the same as Example 1.

[0088] Example 3

[0089] The difference from Example 1 is that the mass ratio of the Ni powder and the Ti3AlC2 powder is 5:5, and the rest is the same as Example 1.

[0090] Example 4

[0091] The difference from Example 1 is that the spraying temperature is 500℃, and the rest is the same as Example 1.

[0092] Example 5

[0093] The difference from Example 1 is that the spraying temperature is 600℃, and the rest is the same as Example 1.

[0094] Example 6

[0095] The difference from Example 1 is that the spraying pressure is 3MPa, and the rest is the same as Example 1.

[0096] Example 7

[0097] The difference from Example 1 is that the spraying pressure is 4MPa, and the rest is the same as Example 1.

[0098] Comparative Example 1

[0099] The difference from Example 1 is that the mass ratio of Ni powder and Ti3AlC2 powder is 2:8, and the rest is the same as Example 1.

[0100] Comparative Example 2

[0101] The difference from Example 1 is that the mass ratio of Ni powder and Ti3AlC2 powder is 4:6, and the rest is the same as Example 1.

[0102] Performance test

[0103] (1) The morphology and particle size of the composite powder in Example 1 were tested, and the results are shown in Figure 4 , where (a) is SEM, and (b) is the particle size distribution of the powder.

[0104] It can be seen from Figure 4 that the Ni-Ti3AlC2 composite powder is uniformly mixed, and the Ti3AlC2 ceramic powder is distributed around the Ni powder. Such powder structure is beneficial to full deformation during collision, which can effectively improve the deposition efficiency of ceramic particles in the spraying process and reduce defects in the coating.

[0105] (2) The morphology and EDS analysis of the composite powder in Example 1 were tested, and the results are shown in Figure 5 , where (a) is SEM, and (b) is the EDS analysis of areas A and B.

[0106] It can be seen from Figure 5 that the Ni-Ti3AlC2 composite powder is uniformly mixed, and the Ti3AlC2 ceramic powder is distributed around the Ni powder. Such powder structure is beneficial to full deformation during collision, which can effectively improve the deposition efficiency of ceramic particles in the spraying process and reduce defects in the coating.It can be seen that no other phase is generated in the Ni-Ti3AlC2 composite powder, which indicates that the Ni powder and Ti3AlC2 powder do not decompose, and the original physical and chemical properties of the powder are retained, which is crucial to the performance of the later deposited coating.

[0107] (3) The surface of the Ni-Ti3AlC2 composite coating prepared in Examples 1-3 was tested by XRD diffraction, and the results are shown in Figure 6

[0108] Figure 6 It can be seen that the three coatings with different ceramic contents are composed of pure Ni phase and Ti3AlC2 hard phase, and no other new reaction phase is generated. This indicates that all the substances in the coating do not decompose or change phase during spraying, and the coating does not oxidize, which benefits from the low working temperature and short spraying time of cold spraying. It also indicates that the phase-change-free Ni-Ti3AlC2 composite coating is successfully prepared by cold spraying technology. The diffraction peak of the hard particle Ti3AlC2 is not obvious, which is caused by the fact that most of the ceramic particles are far from the coating surface, the XRD scanning depth is limited, and secondly, the intensity of Ti3AlC2 is much weaker than that of Ni, so the XRD of the coating surface is not obvious.

[0109] (4) The surface scanning morphology of the Ni-Ti3AlC2 composite coating prepared in Examples 1-3 with different mass ratios was tested, and the results are shown in Figure 7 , where (a) is Ni-20% Ti3AlC2, (b) is Ni-40% Ti3AlC2, and (c) is Ni-50% Ti3AlC2.

[0110] As Figure 7 can be seen, the surfaces of the three coatings are rough, which is determined by the nature of the deposition of cold sprayed solid particles. As Figure 7 (a) can be seen, there are many pores and cracks on the surface of the Ni-20% Ti3AlC2 coating, which is mainly due to the lack of ramming effect of subsequent particles during the deposition process, causing the Ni particles to deform slightly but still maintain a near-spherical shape, resulting in obvious pores at the junction with other particles. When the Ti3AlC2 ceramic particle content in the raw powder increases to 40%, as shown in Figure 7 (b), the Ti3AlC2 ceramic content in the coating increases, the ramming effect of Ti3AlC2 is enhanced, the plastic deformation degree of Ni particles is increased, the pores and cracks of the coating are reduced, and the roughness of the coating is improved, but there are also a few slightly deformed Ni particles, which is significantly improved compared with the Ni-20% Ti3AlC2 coating. As Figure 7 ​​As shown in (c), when the Ti3AlC2 ceramic content is 50%, the ceramic content deposited in the coating reaches its highest level, and the Ti3AlC2 ceramic particles play the greatest compaction role. The degree of plastic deformation of the particles on the coating surface increases, followed by huge plastic deformation due to the high-speed impact of the subsequently sprayed particles, resulting in a flattened state and forming a tight mechanical bond with the previously deposited part. The figure also shows the presence of unbonded state between particles and the formation of detachment pits. This is because some sprayed particles have a low velocity and fail to deposit effectively after impacting the coating, instead rebounding and leaving only impact detachment pits on the surface.

[0111] (5) The cross-sectional microstructure of the Ni-Ti3AlC2 composite coatings prepared under different mass ratios in Examples 1-3 was tested, and the results are as follows: Figure 8 As shown, (ac) is Ni-20%Ti3AlC2, (df) is Ni-40%Ti3AlC2, and (gi) is Ni-50%Ti3AlC2.

[0112] like Figure 8 It can be seen that there are no obvious pores or cracks at the interface between the coating and the substrate. The interface between the coating and the substrate is wavy and interlocked, which is a typical mechanical bonding method of cold spraying. The light gray structure is Ni, and the dark gray structure is Ti3AlC2. It can be seen that as the ceramic content of Ti3AlC2 deposited in the coating increases, the cross-sectional morphology of the three coatings becomes denser, the internal quality of the coating is good, and no cracks or obvious gaps are present between the coatings. The particles are tightly bonded and maintain a high density. This indicates that the shot peening effect of Ti3AlC2 ceramic particles promotes the deformation of Ni and Ti3AlC2, thereby playing a compacting role and leading to an increase in coating density. The high magnification morphology of the cold-sprayed coating cross-section is shown in the image. Figure 8 From (c), (f), and (i), it can be observed that... Figure 8 In (c), a significant number of cracks, pores, and defects were observed inside the Ni-20% Ti3AlC2 coating. This was attributed to incomplete deformation caused by the low velocity of some sprayed particles, resulting in inefficient bonding between particles during the stacking process. Figure 8 As shown in (f), the Ni-40% Ti3AlC2 coating exhibits areas of Ti3AlC2 particle agglomeration. Pores, cracks, and defects are often present around the contact area between Ni and Ti3AlC2. This is mainly due to the difference in particle structure between Ti3AlC2 and Ni, leading to stress concentration at the interface. Secondly, a certain amount of porosity also exists within the agglomerated Ti3AlC2 particles, due to the weak bonding force between ceramic particles caused by their physical properties. When the Ti3AlC2 ceramic content in the raw material powder increases to 50%, such as... Figure 8(i)As shown, the deposition efficiency of ceramic particles increases, the content of Ti3AlC2 deposited in the coating increases, the ceramic particles break up and uniformly distribute in the coating, playing a dispersion strengthening role, the ramming effect of Ti3AlC2 is further enhanced than that of the Ni-40% Ti3AlC2 coating, the Ni particles produce strong plastic deformation, present a flattened shape, are elongated in the direction perpendicular to the spraying direction, and the flattening degree of the pre-deposited particles is higher, proving that the impact of the subsequent particles on the pre-deposited particles further compacts them and makes their plastic deformation more severe. Therefore, the Ni-50% Ti3AlC2 coating is well combined with the substrate, the coating is dense, and there are almost no obvious cracks, pores and defects in the coating.

[0113] (6) The cross-sectional morphology and EDS analysis of the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 with different mass ratios were tested, and the results are shown in Figure 9 , wherein (a) is the cross-section of the Ni-20% Ti3AlC2 coating, (b) is the EDS analysis result, (c) is the cross-section of the Ni-40% Ti3AlC2 coating, (d) is the EDS analysis result, (e) is the cross-section of the Ni-50% Ti3AlC2 coating, and (f) is the EDS analysis result.

[0114] As can be seen from Figure 9 , each colored curve represents an element. According to the EDS line scanning results, only Al element exists in the substrate area, and no Ni, Ti and other elements exist, therefore, there is no obvious diffusion of Ni and Ti elements at the interface between the coating and the substrate, indicating that the bonding mode between the cold sprayed coating and the substrate is mechanical bonding. As can be clearly seen from Figure 9 (b), (d) and (f), the content change curves of Ni, Ti, Al and C elements along the measurement direction are uniformly distributed in the coating. With the increase of the ceramic content deposited in the coating, the curve change trend of the EDS line scanning experimental results is not large, indicating that the Ti3AlC2 ceramic particles are uniformly deposited in the three composite coatings, especially in the Ni-50% Ti3AlC2 composite coating. Therefore, the uniformity of the cold sprayed Ni-50% Ti3AlC2 coating is higher.

[0115] (7) The porosity and Ti3AlC2 ceramic content of the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 with different mass ratios were tested, and the results are shown in Figure 10 .

[0116] As can be seen from Figure 10As can be seen from (a), the porosities of the coatings with three ceramic contents are 0.524, 0.485 and 0.386 respectively, and the porosity of the Ni-50%Ti3AlC2 coating is the lowest, 0.386. It can be seen that the porosity of the coating decreases with the increase of the ceramic content, but does not change significantly, and is at a low level (<1%). This is mainly because with the increase of the Ti3AlC2 content, the Ti3AlC2 particles play a ramming role, greatly increasing the plastic deformation of the Ni particles, making the interfacial bonding between the particles more compact, and the ramming effect of the ceramic particles improves the density of the coating, and the microstructure of the composite coating is obviously improved, and the porosity is reduced. From Figure 10 (b) can be seen that the retained Ti3AlC2 ceramic content in the coating also increases with the increase of the Ti3AlC2 ceramic content in the raw powder, and the retained Ti3AlC2 ceramic content in the coating is up to 23.7% when the raw powder contains 50wt% Ti3AlC2 ceramic powder, but the loss rate of Ti3AlC2 ceramic is relatively high, up to 26.3%. Since the mechanical mixed powder is used for spraying, the loss rate of Ti3AlC2 ceramic powder is too high, but it is consistent with the results of other researchers.

[0117] (8) The hardness variation curves of the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 with different mass ratios were tested, and the results are shown in Figure 11 .

[0118] As can be seen from Figure 11 , the hardness of the substrate is 110HV 0.2 , and in the work-hardened area, the average hardness of the substrate is slightly improved, being 125HV 0.2 . This is because the substrate is work-hardened after sandblasting, resulting in the improvement of the hardness of the substrate. In addition, the hardness of the Ni-Ti3AlC2 composite coating is higher than that of the substrate (110HV 0.2 ), and increases with the increase of the hard phase Ti3AlC2 content, and the hardness of the three composite coatings reaches the highest between 100-150μm from the interface, and then the hardness decreases with the distance from the interface, and the highest hardness of the three coatings is 242HV 0.2 , 256HV 0.2 and 310HV 0.2When the Ti3AlC2 content is 50%, the hardness of the Ni-50%Ti3AlC2 composite coating reaches its maximum. The main reasons for the increased coating hardness can be summarized in two aspects. Firstly, during the cold spraying process, Ni and Ti3AlC2 particles undergo high strain rate deformation upon impact with the substrate, increasing the concentration of dislocation density within the deformed material. This leads to increased particle hardness and a work-hardening effect. Subsequent impacts on particles with dislocation concentration also result in intense plastic deformation, further enhancing the coating's hardness. Secondly, the increased hardness of the Ti3AlC2 particle reinforcing phase deposited in the coating is a significant factor contributing to the increased hardness of the Ni-Ti3AlC2 composite coating. Higher Ti3AlC2 ceramic content in the coating makes it easier for Ti3AlC2 ceramic particles to collide and break down, resulting in a more uniform distribution within the coating. This strengthens the dispersion reinforcement effect of the ceramic reinforcement, further promoting the plastic deformation of Ni particles, reducing internal defects, increasing coating density, and ultimately increasing the hardness of the composite coating.

[0119] (9) The elastic modulus of the Ni-Ti3AlC2 composite coatings prepared at different mass ratios in Examples 1-3 was tested, and the results are as follows: Figure 12 As shown, (a) is the load-displacement curve of the specimen obtained by nanoindentation test under a maximum load of 100mN, and (b) is the average elastic modulus of the coating.

[0120] Depend on Figure 12 (b) It can be seen that the elastic moduli of the three coatings are 152 GPa, 184 GPa, and 192 GPa, respectively. When the ceramic content in the powder increases from 20% to 50%, the elastic modulus of the coating increases by 26.3%. This can be explained by the fact that the increase in the ceramic particle content in the coating promotes the plastic deformation of the sprayed particles and improves the bonding force between particles, resulting in a denser coating structure and thus increasing the elastic modulus of the coating. This also indicates that under the same loading load, the Ni-50%Ti3AlC2 composite coating experiences less plastic deformation.

[0121] from Figure 12As shown in (a), the indentation depth of the Ni-50%Ti3AlC2 coating is smaller than that of the other two coatings, and the indentation depth decreases with increasing distance from the coating surface. The indentation depths of the Ni-50%Ti3AlC2 and Ni-40%Ti3AlC2 coatings are similar, and the elastic modulus of both coatings is not significantly improved, but it is significantly higher than that of the Ni-20%Ti3AlC2 coating. This is due to the dispersion strengthening effect of Ti3AlC2 ceramic particles in the Ni-Ti3AlC2 composite coating, which reduces the indentation depth of the coating under the same stress. This reveals that the addition of Ti3AlC2 ceramic particles increases the ability of the Ni-Ti3AlC2 composite coating to resist plastic deformation. Therefore, the Ni-50%Ti3AlC2 coating has the highest elastic modulus, which means that under the same compressive stress, the coating exhibits the least elastic deformation, which is more conducive to ensuring the accuracy of parts during operation. During wear, it can effectively prevent the indentation of hard micro-protrusions, improving the coating's wear resistance.

[0122] (10) The indentation morphology of the Ni-Ti3AlC2 composite coatings prepared at different mass ratios in Examples 1-3 was tested under a load of 0.01 kgf, and the results are as follows: Figure 13 As shown, (a) is a Ni-20% Ti3AlC2 coating, (b) is a Ni-40% Ti3AlC2 coating, and (c) is a Ni-50% Ti3AlC2 coating.

[0123] Table 3 Calculation parameters for fracture toughness of cold-sprayed Ni-Ti3AlC2 composite coating

[0124]

[0125] Depend on Figure 13 It can be observed that under the same loading conditions, the indentation size of the Ni-Ti3AlC2 composite coating decreases with increasing ceramic content in the coating, which also verifies that... Figure 11 The correctness of the conclusion that the Ni-50% Ti3AlC2 coating has a higher hardness than the other two coatings. From Figure 13 As can be seen, the crack length of the indentation for the Ni-20% Ti3AlC2 coating is 13.10 μm, the crack length for the Ni-40% Ti3AlC2 coating is 10.26 μm, and the crack length for the Ni-50% Ti3AlC2 coating is 9.33 μm. This indicates that the Ni-50% Ti3AlC2 coating has higher fracture toughness. Based on the parameters given in Table 3, the fracture toughness of the three cold-sprayed coatings was calculated using formula (2.1). The calculated fracture toughness of the Ni-20% Ti3AlC2 coating is 84.57 MPa·m. 1 / 2 The fracture toughness of the Ni-40%Ti3AlC2 coating is 130.52 MPa·m.1 / 2 The fracture toughness of the Ni-50% Ti3AlC2 coating is 225.59 MPa·m. 1 / 2 The value increased by 166.7%. Indentation cracks originate from microcracks or pores on the coating surface, and the cracks begin to propagate under stress. Since Ti3AlC2 ceramic particles can inhibit crack propagation and deflect it, the length of the crack propagation path is increased, thereby improving the fracture toughness of the Ni-50%Ti3AlC2 coating. On the other hand, the Ni-50%Ti3AlC2 coating has the highest ceramic content, resulting in the strongest compaction effect, promoting the plastic deformation capacity of Ni particles, making the internal structure of the coating dense, with fewer defects, and a lower tendency for crack initiation and instability. The coating contains a large number of dislocations, effectively improving the strength and hardness of the coating. In addition, the large residual compressive stress inside the coating also plays a toughening role. Therefore, the fracture toughness of the Ni-50%Ti3AlC2 coating is higher than that of the other two coatings.

[0126] (11) The bonding strength of the Ni-Ti3AlC2 composite coatings prepared at different mass ratios in Examples 1-3 was tested, and the results are as follows: Figure 14 As shown.

[0127] Depend on Figure 14 It can be seen that the bonding strength of the coating increases with the increase of Ti3AlC2 content in the raw material powder. The bonding strengths of the Ni-Ti3AlC2 composite coatings are approximately 24.8 MPa, 36.8 MPa, and 44.7 MPa, corresponding to Ti3AlC2 contents of 20%, 40%, and 50% in the raw material powder. This indicates that adding hard cermet particles not only increases the deformation degree of Ni particles but also enhances the mechanical interlocking between the Ni-Ti3AlC2 composite coating and the substrate. For the Ni-20%Ti3AlC2 coating, due to the larger particle size and higher density of Ti3AlC2 particles, their deposition content in the coating is relatively low, resulting in less impact on Ni particles. This leads to less plastic deformation of the composite particles, more porosity and cracks in the coating, further reducing the bonding strength. Therefore, the Ni-20%Ti3AlC2 coating has the lowest bonding strength. In contrast, the Ni-40%Ti3AlC2 coating has a higher ceramic content, resulting in enhanced deformation of the composite particles and thus achieving higher bonding strength. Furthermore, with the increase of Ti3AlC2 content, the impact of Ti3AlC2 particles is enhanced, promoting the plastic deformation ability of Ni particles, significantly improving the coating microstructure and increasing density. This leads to an increase in the mechanical bonding area between the particles and the substrate, thereby improving the interfacial bonding strength between the coating and the substrate. Therefore, the bonding strength of the Ni-Ti3AlC2 composite coating increases with the increase of Ti3AlC2 content in the raw material powder, with the Ni-50%Ti3AlC2 coating exhibiting the highest bonding strength.

[0128] (12) The macroscopic fracture morphology of the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 with different mass ratios was tested, and the results are shown in FIG. 6, wherein (a-b) is the Ni-20% Ti3AlC2 coating, (c-d) is the Ni-40% Ti3AlC2 coating, and (e-f) is the Ni-50% Ti3AlC2 coating. Figure 15

[0129] From Figure 15 (a) and (b) can be observed that the surface of the Ni-20% Ti3AlC2 coating on the substrate side has no obvious coating residue, indicating that the failure mode between the coating and the substrate is interfacial adhesive fracture. Figure 15 (c) and (d) show the macroscopic fracture morphology of the Ni-40% Ti3AlC2 coating. With the increase of the Ti3AlC2 ceramic content deposited in the coating, the failure mode between the coating and the substrate changes. On the surface of the substrate side, a small amount of coating residue can be seen, and the peeling of the coating causes obvious pits on the coating side. The peeling of the coating is caused by the internal cohesive failure of the coating, so the failure mode of the Ni-40% Ti3AlC2 coating is a composite failure mode mainly of interfacial adhesive fracture and supplemented by internal cohesive fracture of the coating. Figure 15 (e) and (f) show the macroscopic fracture morphology of the Ni-50% Ti3AlC2 coating. It can be observed that there is a large area of coating residue on the surface of the substrate side, indicating that internal cohesive fracture of the coating occurs. Therefore, the failure mode of the Ni-50% Ti3AlC2 coating also belongs to a composite failure mode of adhesive fracture and cohesive fracture. By observing the fracture morphology and failure mode of the three coatings, it can be found that with the increase of the Ti3AlC2 content, the amount of coating residue on the surface of the substrate side gradually increases, and the fracture mode changes to a composite failure mode mainly of interfacial adhesive fracture and supplemented by internal cohesive fracture of the coating. This change in failure mode is consistent with the change in the interfacial bonding strength of the coating-substrate, further confirming the strengthening effect of the Ti3AlC2 ceramic particles on the interface bonding.

[0130] (13) The tensile fracture morphology of the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 with different mass ratios was tested, and the results are shown in FIG. 7, wherein (a-b) is the Ni-20% Ti3AlC2 coating, (c-d) is the Ni-40% Ti3AlC2 coating, and (e-f) is the Ni-50% Ti3AlC2 coating. Figure 16 By observing

[0131] Figure 16 ​​(a), (c), (e) In the low-magnification SEM images, the coating surfaces of the three different ceramic contents can be clearly observed to be relatively rough, which is attributed to the characteristics of cold spraying solid deposition. In the cold spraying process, solid spraying particles impact the substrate at high speed, undergo adiabatic shear instability, and are deposited to form a coating through plastic deformation. Therefore, mechanical bonding is the main bonding mode in the cold spraying process, which also explains the reason for the roughness of the coating surface. Figure 16 (b) is a high-magnification SEM image of the fracture surface of the Ni-20% Ti3AlC2 coating. It can be clearly seen that there are cracks between the Ni and Ti3AlC2 particles in the coating fracture surface, and there are obvious defects and shedding pits between the Ti3AlC2 particles. This is mainly because the content of the deposited Ti3AlC2 ceramic particles in the coating is low, and the ceramic particles do not play a full role in tamping the Ni particles during spraying, resulting in insufficient plastic deformation between the Ni particles, ineffective stacking between the Ni and Ti3AlC2 particles, and the generation of cracks and defects. Ceramic shedding pits are also found in the coating fracture surface, which is due to the high-speed impact of the subsequently sprayed ceramic particles on the already deposited ceramic particles, causing them to fall off and form ceramic shedding pits. Figure 16 (d) is a high-magnification SEM image of the fracture surface of the Ni-40% Ti3AlC2 coating. It can be clearly seen that there are cracks, defects and ceramic shedding pits between the Ni and Ti3AlC2 particles in the coating fracture surface, but they are significantly reduced compared to the Ni-20% Ti3AlC2 coating. This can be attributed to the increase in the content of Ti3AlC2 ceramic in the coating, which further enhances the hammering effect of the ceramic particles on the Ni particles, enhances the plastic deformation ability of the Ni particles, and improves the bonding interface between the composite particles. The organization of the coating is more compact, the bonding force between the particles is improved, and it also indicates that the bonding strength and hardness of the Ni-40% Ti3AlC2 coating are improved. As for the generation of ceramic shedding pits, on the one hand, the content of Ti3AlC2 ceramic particles in the coating is increased, the probability of mutual impact between the ceramic particles is increased, and the ceramic particles fail to be deposited in the coating, resulting in shedding. On the other hand, in the subsequent spraying process, the ceramic particles impact the already deposited ceramic particles, causing the already deposited ceramic particles to fall off and form ceramic shedding pits. Figure 16(f) SEM image of the fracture surface of Ni-50% Ti3AlC2 coating. A small amount of cracks and defects can be observed between the Ti3AlC2 particles. The most Ti3AlC2 particles were deposited in the Ni-50% Ti3AlC2 coating, which played a strong role in ramming and caused the Ni particles to be severely plastically deformed and mechanically interlocked between the particles and enhanced the bonding strength. In addition, the increase of ceramic content in the coating, on the one hand, led to the increase of the probability of collision between the ceramic particles, resulting in serious crushing phenomenon, and the refinement of the ceramic particles also played a dispersion strengthening effect on the coating and made the coating structure more dense. On the other hand, the smaller ceramic particles were tightly wrapped by the Ni particles with strong plastic deformation ability and uniformly distributed in the coating, which made the Ti3AlC2 particles firmly combined with the Ni-based coating. This explained the reason why the Ni-50% Ti3AlC2 coating had the highest bonding strength than the 20% and 40% coatings.

[0132] (14) Wear tests of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 were carried out under dry friction conditions, and the results are shown in FIG. 14, wherein (a) is the friction and wear curve, and (b) is the wear rate histogram. Figure 17

[0133] Figure 17 ​(a) shows the friction coefficient curve of the ADC12 aluminum alloy substrate and the Ni-Ti3AlC2 composite coating as a function of time. For the substrate, the friction coefficient rises rapidly to a maximum value (about 1.401) within the first 100 s, then experiences a short running-in period and tends to be stable, with the friction coefficient maintained at about 1.06. In the early running-in wear stage, the substrate is soft, and the ploughing effect of the ball on the substrate surface forms material accumulation and adhesion with the ball, resulting in a rapid rise in the friction coefficient. After 300 s in this wear environment, the substrate surface work hardens, and the micro-bumps and furrows are gradually flattened by the grinding ball, the friction coefficient decreases accordingly, and enters the stable wear stage. Compared with the substrate, the friction coefficient of the Ni-20% Ti3AlC2 coating changes more stably during the wear test period, and after a short running-in period at the beginning of the wear test, the friction coefficient quickly decreases, and then the degree of fluctuation of the friction coefficient becomes smaller and gradually enters the stable wear stage, with the friction coefficient finally stabilized at about 0.84. The friction coefficient curve of the Ni-40% Ti3AlC2 coating is similar to that of the Ni-20% Ti3AlC2 coating. After a short running-in period at the beginning of the wear test, the friction coefficient quickly decreases, and then the degree of fluctuation of the friction coefficient becomes smaller and gradually enters the stable wear stage. The friction coefficient is maintained at about 0.77. Compared with the Ni-20% Ti3AlC2 coating, the friction coefficient of the Ni-40% Ti3AlC2 coating is lower. This is because the ceramic content in the Ni-40% Ti3AlC2 coating is higher, and the ceramic particles play a ramming role, enhancing the deformation ability of metal particles and improving the density and hardness of the coating. Therefore, the Ni-40% Ti3AlC2 coating has better wear resistance. In contrast, the friction coefficient curve of the Ni-50% Ti3AlC2 coating appears relatively simple, with a long running-in stage (600 s), and then the friction coefficient is stable at a low level (about 0.64). In the early stage of friction, the GCr15 ball is easily pressed into the coating, and as the friction process proceeds, on the one hand, the contact area between the ball and the coating surface increases, and on the other hand, the ploughing effect of the multi-angle layered Ti3AlC2 ceramic particles on the friction surface causes the friction coefficient to rise sharply. After a period of running-in, the friction coefficient decreases slowly, but there is also a small fluctuation, because the grinding object of the GCr15 ball is constantly switched between Ni and Ti3AlC2 ceramic particles, resulting in unstable friction coefficient in the early wear stage. But in the subsequent wear process, the particles inside the coating are shed and cut off into smaller wear debris to fill the bottom of the wear pit, making the contact surface smooth. Moreover, the hardness of the Ni-50% Ti3AlC2 coating shows a trend of increasing gradient, and the microstructure is more dense, hindering the wear process, and the friction coefficient gradually enters the stable stage. Therefore, the friction coefficient of the Ni-50% Ti3AlC2 coating is the lowest.

[0134] Comparison of wear rates of aluminum alloy substrate and coating under dry friction test conditions is shown in Fig. Figure 17 (b). The wear rates of Ni-Ti3AlC2 composite coatings are all lower than that of the substrate, the wear rate of the aluminum alloy substrate is 89.6x10 -5 mm 3 / N·m, while the wear rate of the Ni-20%Ti3AlC2 coating is significantly reduced to 13.8x10 -5 mm 3 / N·m, in contrast, the wear rate of the Ni-40%Ti3AlC2 coating is 4.76x10 -5 mm 3 / N·m, with a larger decrease of about 64%. This is due to the increase of ceramic content in the coating, the densification of the structure and the increase of hardness, which improves the wear resistance of the coating. The wear rate of the Ni-50%Ti3AlC2 coating is 1.87x10 -5 mm 3 / N·m, which is the lowest, because the coating retains the most ceramic content, the ramming effect of the ceramic is enhanced, which improves the plastic deformation ability of the metal particles and improves the inter-particle bonding force. In addition, the Ni-50%Ti3AlC2 coating has the highest hardness, which enhances the wear resistance. Compared with the Ni-40%Ti3AlC2 coating, the wear rate of the Ni-50%Ti3AlC2 coating is reduced by 60.71%, indicating that the Ni-50%Ti3AlC2 coating can provide more effective wear protection for the aluminum alloy substrate.

[0135] (15) The three-dimensional morphology of the wear scar of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 was tested, and the results are shown in Fig. Figure 18 (a) is the substrate, (b) is the Ni-20%Ti3AlC2 coating, (c) is the Ni-40%Ti3AlC2 coating, and (d) is the Ni-50%Ti3AlC2 coating.

[0136] From Figure 18 (a) and (b), it can be seen that under the same dry friction test load, the maximum width of the wear scar of the substrate is 2.90mm, the maximum depth is 116μm, and the wear volume is 21.52x10 -2 mm 3 mm. According to Figure 18 (a), it can be observed that the wear scar of the substrate is wide and deep, and there are many furrows on the wear scar, the depth of the furrows at the bottom is obvious, the uniformity of the whole wear scar is poor and the surface is rough, which indicates that the friction coefficient is unstable and fluctuates greatly. From Figure 18As shown in (c) and (d), the maximum width of the wear track on the Ni-20% Ti3AlC2 coating is 1.92 mm, the maximum depth is 58.3 μm, and the wear volume is 3.317 × 10⁻⁶. -2 mm 3 , combined Figure 18 As shown in (b), the wear track morphology of the coating is similar to that of the substrate, but the wear volume is significantly reduced. The wear track contour becomes shallower and narrower, with parallel and uniform furrows at the edges, while the middle part is relatively smooth, and the furrows at the bottom are deeper. This is because the Ni-20%Ti3AlC2 coating has a low ceramic content. When the grinding ball contacts the coating, it only contacts the metallic nickel coating structure. Since the hardness of nickel is lower than that of ceramic, the wear track in the middle is relatively smooth during the wear process. As the contact area between the grinding ball and the coating increases, the coefficient of friction increases sharply. As the wear process progresses, the grinding ball comes into contact with the ceramic particles inside the coating, and the cutting action of the hard ceramic particles makes the bottom wear track deeper.

[0137] (16) The wear track morphology profile curves of the substrate and the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 during the dry friction test are shown in the figure. Figure 19 As shown, (a,b) is the substrate, (c,d) is the Ni-20% Ti3AlC2 coating, (e,f) is the Ni-40% Ti3AlC2 coating, and (g,h) is the Ni-50% Ti3AlC2 coating.

[0138] from Figure 19 As shown in (e) and (f), the maximum width of the wear track on the Ni-40% Ti3AlC2 coating is 1.73 mm, the maximum depth is 26.8 μm, and the wear volume is 1.144 × 10⁻⁶. -2 mm 3 Combining Figure 19 In the wear track morphology shown in (c), the width and depth of the wear track in the coated layer are significantly reduced compared to the Ni-20%Ti3AlC2 coating. The central wear track exhibits multiple parallel and uniform furrows, but the overall wear track morphology is narrow and shallow, with uneven and rough edges. This is mainly because the increased ceramic content in the coating leads to higher coating hardness. When the grinding ball initially contacts the coating, it cannot grind smoothly but slides on the coating surface, causing the coefficient of friction to increase. Finally, the dry friction test is successfully completed at a lower surface hardness point, leaving wear tracks. Therefore, the coefficient of friction in the later stages of the dry friction test of Ni-40%Ti3AlC2 is more stable than in the earlier stages. Figure 19 From (g) and (h), it can be seen that the maximum width of the wear track of the Ni-50% Ti3AlC2 coating is 0.74 mm, the maximum depth is 12.6 μm, and the wear volume is 0.4493 × 10⁻⁶. -2 mm 3 .according to Figure 19(d)It can be seen that the edge of the wear scar of the Ni-50% Ti3AlC2 coating is relatively smooth after the dry friction test, but there are several deep grooves at the bottom, which is due to the increase of the content of Ti3AlC2 hard ceramic particles in the coating. At the initial stage of the test, the friction between the ball and the Ti3AlC2 hard ceramic particles occurs, and the friction resistance of the ball increases. Therefore, the friction coefficient of the coating shows an upward trend at the initial stage. With the progress of the dry friction test, the Ti3AlC2 particles exposed in the coating are brittle fractured, forming fine particles and partially maintaining the shape of large particles. The high-hardness Ti3AlC2 ceramic particles leave several deep grooves on the surface of the coating.

[0139] (17) The SEM scanning morphology of the wear scar of the aluminum alloy substrate after the dry friction test is shown in Figure 20 , where (a) is 500x, and (b) is 1000x.

[0140] It can be observed from Figure 20 that the wear degree of the aluminum alloy substrate is relatively serious. There are dense and uniform parallel furrows, adhesion marks and accumulated wear debris on the wear scar. This is because the hardness of the aluminum alloy substrate is relatively low (about 110 HV 0.2 ). During the wear process, the GCr15 steel ball can easily press into the substrate, causing plowing action on the surface of the substrate, forming material accumulation. From Figure 20 (b), it can be seen that a large amount of wear debris is accumulated on the edge of the furrow. Combined with the energy spectrum analysis in Figure 20 (a), it can be seen that the oxygen content is as high as 35%, indicating that the substrate has undergone oxidative wear. With the progress of the wear process, the contact surface temperature rises, and a discontinuous oxide film is formed on the surface of the substrate. The plowing action of the oxide particle debris will cause the surface of the substrate to break and form grooves. The substrate undergoes abrasive wear process. When the wear debris is repeatedly pressed to the edge by the counter ball, a small amount of small abrasive particles will fall off in the furrow of the wear scar, aggravating the wear and material loss of the substrate. Due to the large loading load, the wear debris on the edge of the furrow is pressed into adhesion marks and defects, and the furrow on the overall wear surface is relatively smooth. Cracks and defects caused by plastic deformation of the substrate can also be observed. Therefore, the wear on the surface of the substrate mainly includes abrasive wear, oxidative wear and slight adhesive wear.

[0141] (18) The SEM scanning morphology of the wear scar of the cold sprayed Ni-20% Ti3AlC2 coating in Example 1 after the dry friction test is shown in Figure 21 , where (a) is 500x, and (b) is 1000x.

[0142] In Figure 21 (a), it can be seen that the Ni-20% Ti3AlC2 coating and the substrate wear surface show completely different characteristics. There is less wear debris in the coating. From the high-magnification wear scar morphologyFigure 21 (b) it can be clearly observed that there are furrows, cracks, delamination, oxide particles and large area spalling on the surface of the coating. The Ni-20% Ti3AlC2 coating has a high friction coefficient due to the severe wear between the coating and the counter ball in the initial stage of wear, but the wear debris reduces the wear area and the degree of wear. The hardness of the coating is reduced due to the low content of Ti3AlC2 ceramic in the coating and the weak compaction effect. The wear debris is plastically deformed under repeated rolling, forming a local oxide surface layer and smaller abrasive particles, and most of the wear debris is extruded to both sides to form spalling. The hard particles in the wear debris produce a cutting effect on the surface of the coating, forming furrows, indicating that abrasive wear occurs. The cracks, delamination and spalling of the coating are due to the low hardness of the coating and the weak inter-particle bonding force. Under the reciprocating normal load and tangential cutting, stress concentration occurs at the surface defects, leading to crack formation. As the cracks expand, the micro-cracks are connected to each other. In addition, strong shear forces are applied to the micro-convexities on the friction surface, causing plastic flow and resulting in cold welding and adhesion. When the shear force exceeds the bonding force of the welded joint, the fragments are spalled from the weaker side and adhere to the surface of the stronger material, resulting in adhesive wear, delamination and spalling. In combination with the above analysis, the wear mechanism of the Ni-20% Ti3AlC2 coating is mainly abrasive wear, oxidative wear and adhesive wear. Figure 21 (a) The results of the energy spectrum show that the oxygen content of the worn surface is very high, reaching 37.02%, which indicates that an oxidation reaction occurs on the surface of the coating. Therefore, the wear mechanism of the Ni-20% Ti3AlC2 coating is mainly abrasive wear, oxidative wear and adhesive wear.

[0143] (19) The SEM scanning morphology of the wear scar of the cold sprayed Ni-40% Ti3AlC2 coating in Example 2 after dry friction test is shown in FIG. 17, wherein (a) is 500x and (b) is 1000x. Figure 22

[0144] As can be seen from Figure 22 (a), the wear surface of the Ni-40% Ti3AlC2 coating is smooth. From the high-magnification wear morphology Figure 30 (b), it can be further found that the wear surface of the coating has less wear debris and cracks, but the spalling and tearing delamination phenomenon is serious, accompanied by shallow furrows. When the Ti3AlC2 content in the raw material powder is 40%, the retained Ti3AlC2 content in the coating is 17.4%, and the hardness of the coating is further improved, but it is still lower than that of the GCr15 counter ball. During the severe wear process, the deformation resistance of the coating decreases, leading to the shedding of protruding Ti3AlC2 particles, resulting in abrasive wear; the shed particles increase the roughness of the wear surface and enhance the mechanical deformation resistance. The shear force causes the coating to spall in large areas from the particle interface defects, forming tearing delamination and accompanied by crack formation, indicating that the coating undergoes fatigue wear. In addition, there are shallow grooves on the surface of the coating spalling, which is due to the fact that the wear debris remaining on the wear scar surface acts as abrasive particles, producing contact stress during the counter-attrition process, forming a scraping effect, causing shallow grooves. At the same time, according to the energy spectrum analysis of the wear debris, the oxygen content of the wear debris is 23.62%, which indicates that the wear debris is oxidized during the wear process. Figure 22 ​(a) Energy dispersive spectroscopy (EDS) results show that the oxygen content in the surface morphology of the coating wear tracks increases sharply to 39.59%, indicating that oxidative wear also occurs during dry friction, and the resulting oxidation products exist in the form of wear debris. Therefore, the wear mechanism of the Ni-40%Ti3AlC2 coating is mainly abrasive wear, oxidative wear, and fatigue wear.

[0145] (20) The SEM scan morphology of the wear marks of the cold-sprayed Ni-50%Ti3AlC2 coating in Example 3 after the dry friction test is shown in the figure. Figure 23 As shown, (a) 500×, (b) 1000×.

[0146] from Figure 23 As clearly seen in (a), the wear surface of the Ni-50%Ti3AlC2 coating is relatively rough, exhibiting delamination, cracks, wear debris accumulation, and shallow furrows, indicating a relatively mild overall wear. The Ni-50%Ti3AlC2 coating retains the highest ceramic content, resulting in a dense structure, high hardness, and excellent bonding strength. The Ti3AlC2 ceramic particles are tightly embedded and evenly distributed, making them difficult to detach. The exposed Ti3AlC2 ceramic particles on the wear surface are firmly anchored to the wear marks, causing the Ni particles in the coating to be compressed and undergo plastic flow, simultaneously forming grooves and increasing the severity of the furrows, but without significantly causing surface wear. As the wear process progresses, the repeated rolling and sliding of the grinding ball applies cyclic alternating stress, leading to fatigue cracks on the wear surface. With increasing cycles, the fatigue cracks further expand, eventually causing large pieces of debris to peel off from the coating surface, leaving pits and delamination, indicating fatigue wear of the coating. The presence of large-scale localized spalling and wear debris accumulation in the coating is due to the increased contact area of ​​the friction pair and enhanced wear shear force after fatigue wear. This makes the coating surface more prone to spalling and wear debris generation, which is then compressed into localized areas during the wear process, resulting in large-scale localized spalling and wear debris accumulation. In the bonding... Figure 23 The energy dispersive spectroscopy (EDS) results in (a) show a high oxygen content of 41.79%, indicating that the coating underwent an oxidative wear process. Therefore, the wear mechanism of the Ni-50%Ti3AlC2 coating is mainly abrasive wear, oxidative wear, and fatigue wear.

[0147] (21) Wear test results of the substrate and the cold-sprayed Ni-Ti3AlC2 coatings in Examples 1-3 under oil lubrication conditions are as follows: Figure 24 As shown, (a) is the friction and wear curve, and (b) is the wear rate histogram.

[0148] from Figure 24As can be seen from the friction curve of the substrate in (a), the friction curve of the substrate is stable, indicating that the stable wear stage is directly entered after a short running-in period, and the friction coefficient is stable at about 0.32. The friction curve of the Ni-20%Ti3AlC2 coating changes greatly, and in the first 200s, it first increases sharply, then decreases rapidly, and finally enters the stable friction stage until 600s, and the friction coefficient is stable at about 0.28, which is slightly lower than that of the substrate. In the initial 200s of the oil lubricated friction test, the GCr15 ball is only in point contact with the Ni-20%Ti3AlC2 coating, and the surface adsorption film cannot be formed between the friction pair, so the friction coefficient increases sharply. Secondly, the Ti3AlC2 ceramic content in the coating is less, the ramming effect of the hard phase is weak, the microstructure of the coating is poor, the hardness is low, and the porosity of the coating near the surface is high, so the ball is easily pressed into the coating in the early stage of wear. After 600s of friction, the contact area between the ball and the coating increases, and the friction coefficient also increases. After a period of running-in, the lubricating oil film is formed between the friction pair, which separates the two friction surfaces to avoid surface sticking, thereby reducing the friction coefficient. Therefore, the Ni-20%Ti3AlC2 coating enters the stable wear stage after 600s of running-in. The friction curve of the Ni-40%Ti3AlC2 coating is very similar to that of the substrate, and it first experiences a small increase, and then enters the stable wear stage after 200s, and the friction coefficient is stable at about 0.23. The friction coefficient of the coating increases slightly in the first 200s, which may be due to the increase of the ceramic content in the coating and the layered multiangular structure of the Ti3AlC2 ceramic particles. The lubricating oil cannot timely wrap the Ti3AlC2 ceramic, and the lubricating oil film is difficult to form on its surface, so the solid is directly in contact, resulting in an unstable friction coefficient for a short time and a slight increase. The friction curve of the Ni-50%Ti3AlC2 coating is always in the stable wear stage, and the friction coefficient is stable at about 0.17. Due to the increase of the Ti3AlC2 ceramic content in the coating, the ramming effect of the ceramic particles is enhanced, the plastic deformation ability of the Ni particles is improved, the microstructure of the coating is improved, the porosity of the coating is low, the hardness is high, and the wear resistance is good. Secondly, the surface of the coating is smooth after polishing, so the lubricating oil film can be completely formed on the surface of the coating. Therefore, during the friction process, the lubricating oil film plays a role in reducing friction, so that the friction coefficient of the Ni-50%Ti3AlC2 coating remains stable.

[0149] Compared to the coefficient of friction under dry friction conditions, the coefficient of friction under oil lubrication conditions is lower. This may be because under oil lubrication conditions, the lubricating oil forms an adsorption film on the surface of the friction pair. Due to the cohesive force between oil film molecules, the adsorption film has a certain load-bearing capacity. The friction system consists of paired friction pairs, oil film, and a coating on the surface of the friction pairs, which effectively prevents the paired friction pairs from directly contacting the coating. When the two solids slide relative to each other, they drive the lubricating film to slide together, reducing the coefficient of friction.

[0150] Wear rates of aluminum alloy substrate and coating under oil-lubricated friction test conditions, such as Figure 24 As shown in (b), the wear volume measured by a white light interferometer for three-dimensional topology is as follows: substrate 4.689 × 10⁻⁶. -3 mm 3 Ni-20% Ti3AlC2 coating 4.28×10 -3 mm 3 Ni-40% Ti3AlC2 coating 2.319×10 -3 mm 3 Ni-50% Ti3AlC2 coating 1.561×10 -3 mm 3 Substituting the wear volume of each sample and the test parameters in Table 2.3 into formula (2.2), the wear rate of the substrate is calculated to be 26.05 × 10⁻⁶. -6 mm 3 The wear rate of the Ni-20% Ti3AlC2 coating was 23.77 × 10⁻⁶ N·m. -6 mm 3 / N·m, compared with the substrate, the wear rate of the coating does not show a significant decreasing trend. It is well known that coatings with ceramic content generally have higher wear resistance than the substrate. However, the wear resistance difference between the Ni-20%Ti3AlC2 coating and the substrate is not significant. This anomaly is due to several factors. On the one hand, the low content of Ti3AlC2 ceramic particles in the coating results in weak compaction, weak plastic deformation ability of the nickel particles, and weak interparticle bonding, failing to form an effective coating stack. Numerous microcracks, pores, and defects exist between the particles, resulting in a poor microstructure. During friction and wear, if the radial force applied to the coating by the friction ball exceeds the interparticle bonding force, the Ti3AlC2 particles will detach, creating obvious furrows on the wear surface and exacerbating coating wear. On the other hand, the presence of numerous pores, cracks, and defects in the coating prevents the lubricating oil from filling the pores in the initial stage of friction, failing to form a complete lubricating oil film, leading to friction on the surface resembling dry friction. Figure 24The friction coefficient curve of the Ni-20% Ti3AlC2 coating in (a) also shows that the wear of the coating is aggravated during this process. Therefore, the wear rate of the Ni-20% Ti3AlC2 coating does not decrease obviously compared with the substrate. The wear rate of the Ni-40% Ti3AlC2 coating is 12.88 x 10 -6 mm 3 / N·m, which is much lower than the wear rate of the Ni-20% Ti3AlC2 coating, indicating that the more Ti3AlC2 ceramic particles remaining in the coating, the more effective wear-resistant protection the cold sprayed coating can provide for the aluminum alloy substrate. The wear rate of the Ni-50% Ti3AlC2 coating is 8.67 x 10 -6 mm 3 / N·m, which is 32.68% less than the wear rate of the Ni-40% Ti3AlC2 coating, indicating that the wear resistance of the Ni-50% Ti3AlC2 coating is more excellent than that of the Ni-40% Ti3AlC2 coating.

[0151] The three-dimensional morphology test results of the wear scars of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 under oil lubrication conditions are shown in (a), (b), (c) and (d) in FIG. 6, respectively. Figure 25

[0152] As can be seen from (a), the maximum width of the wear scar of the aluminum alloy substrate is 0.752 mm, and the maximum depth is 51.1 μm. It can be observed that the wear scar profile of the substrate under oil lubrication friction conditions is relatively rough, and obvious furrows can be seen. There is a lot of debris accumulated at both ends of the wear scar. Since the hardness of the substrate is relatively low, the substrate will be cut by the grinding ball during the wear process, and the furrows are more obvious. As the contact area increases, the wear volume of the substrate also increases, but the friction of the substrate is relatively stable. This also explains why the friction coefficient of the substrate is always stable. Figure 25 (b) and (b) can be seen, the wear scar profile of the Ni-20% Ti3AlC2 coating is obviously different from that of the substrate. The maximum width of the wear scar is 0.752 mm, and the maximum depth is 39.5 μm. The wear scar profile depth and furrow phenomenon of the coating are smaller than those of the substrate, and the wear volume is smaller than that of the aluminum alloy substrate. It can be seen from (b) that the wear rate of the Ni-20% Ti3AlC2 coating is less than that of the substrate, indicating that the wear resistance of the Ni-20% Ti3AlC2 coating is greater than that of the substrate. Figure 25 Figure 26 Figure 24

[0153] ​​​​(23) The three-dimensional morphology of the wear scar of the aluminum alloy substrate and the Ni-Ti3AlC2 composite coatings prepared in Examples 1-3 under oil lubrication is shown in Figure 7, wherein (a) is the aluminum alloy substrate, (b) is the Ni-20% Ti3AlC2 coating, (c) is the Ni-40% Ti3AlC2 coating, and (d) is the Ni-50% Ti3AlC2 coating. Figure 26

[0154] According to Figure 25 (c) and Figure 26 (c), the maximum wear width of the wear scar of the Ni-40% Ti3AlC2 coating is 0.516 mm, and the maximum wear depth is 13.8 μm. The width and depth of the wear scar of the coating are significantly reduced compared to the Ni-20% Ti3AlC2 coating, and uniform parallel furrows exist at the bottom of the wear scar, which is due to the increased content of Ti3AlC2 ceramic particles in the coating, and the hard Ti3AlC2 ceramic particles and wear debris that are prone to brittle fracture during friction play a plowing role in the composite coating. Figure 25 (d) and Figure 26 (d), the maximum wear width of the wear scar of the Ni-50% Ti3AlC2 coating is 0.639 mm, and the maximum wear depth is 6.96 μm. The wear scar profile is relatively rough and accompanied by furrows of varying widths, but the wear depth is the shallowest and the wear volume is the smallest. Due to the presence of Ti3AlC2 hard ceramic particles, the composite coating structure is more dense, and the bonding force between Ti3AlC2 ceramic particles and Ni particles is more uniform. At the same time, due to the high hardness and high wear resistance of the cold-sprayed Ni-50% Ti3AlC2 coating, the average wear depth of the coating is not high, so the wear volume is the smallest.

[0155] (24) The morphology of the wear scar of the aluminum alloy substrate after 30 min of friction and wear under oil lubrication is shown in Figure 8, wherein (a) is 500x, and (b) is 1000x. Figure 27

[0156] From the low-magnification morphology Figure 27 (a), it can be observed that the wear scar on the surface of the aluminum alloy substrate is about 578 μm wide, the substrate surface is smooth, and there are no obvious defects, accompanied by obvious furrows. From the high-magnification morphology Figure 27 ​​(b) can be clearly seen dense and parallel furrows and a large number of cracks, with less defects. The aluminum alloy substrate hardness is low, in the oil lubricated friction and wear process GCr15 steel ball can easily press into the substrate, the substrate surface plowing effect, due to the protective effect of lubricating oil, the substrate surface plowing shallow. The substrate surface produces a large number of cracks due to the fatigue wear process of the substrate in the process of friction and wear, fatigue refers to the special form of damage caused by repeated stress cycle, fatigue process includes three stages of fatigue crack initiation, crack metastable extension and unstable extension. After repeated rolling and sliding contact surface is subjected to cyclic alternating stress, making its surface form fatigue cracks, when more than a certain number of cycles fatigue crack is further extended, eventually leading to the material surface peeling off large pieces of debris and leave a large number of pits. The substrate in the process of friction by the normal shear force and load double effect, substrate surface layer has occurred compression deformation, leading to the contact area of the ball and substrate surface increased, bearing capacity while further accumulation of strain. Once the strain accumulation reaches the critical level, the wear surface gradually form cracks and extend, eventually in the contact surface fracture, material in the form of layered debris from the surface removal, fatigue wear. Secondly, under the action of alternating contact stress, the intermetallic sliding process may occur strong adhesion, resulting in wear track appeared local peeling phenomenon, defects. Therefore, the oil lubricated friction and wear test of aluminum alloy substrate surface wear mechanism is mainly for adhesive wear and fatigue wear, with abrasive wear.

[0157] (25) Oil lubricated friction condition Ni-20% Ti3AlC2 coating after 30 min friction and wear of the wear scar morphology as shown in Figure 28 , wherein, (a) 500 x, (b) 1000 x.

[0158] From Figure 28 (a) can be observed, the Ni-20% Ti3AlC2 coating surface wear scar width of about 770 μm, coating surface rough, there are deep furrow phenomenon. With the aluminum alloy substrate in oil lubricated friction conditions exist more obvious difference. From Figure 28(b) In the high-magnification morphology of the grinding mark, a large number of furrows, multiple peeling and delamination defects and a small amount of grinding dust can be clearly seen on the surface of the coating grinding mark, indicating that the degree of coating wear is relatively large. The multiple furrows of different widths on the coating surface are due to the small amount of Ti3AlC2 ceramic particles deposited in the coating, which has a small ramming effect on the Ni particles. During deposition, it does not fully undergo plastic deformation, resulting in poor coating structure, more pores and crack defects, low hardness, and lubricating oil seeping into the pores and cracks without forming an effective lubricating oil film to reduce friction. Under the repeated wear of the grinding ball, cutting occurs, the coating's resistance to deformation decreases, and therefore the furrows are deep, indicating that the coating is undergoing abrasive wear at this time. Secondly, the generation of multiple peeling and delamination defects and a small amount of grinding dust in the coating indicates that the coating is undergoing adhesive wear. On the one hand, as the friction and wear process progresses, the contact area of the friction pair is large, the shear force of wear is enhanced, and the lubricating oil film is difficult to form on the surface, making the solid directly contact, similar to a dry friction state, which easily causes the coating surface to peel and delaminate. On the other hand, the coating material on both sides of the furrow is in a raised state due to the extrusion of the abrasive. When the GCr15 counter-ball rubs against the furrow and the raised portions on both sides, the raised portions that support during friction are peeled and delaminated under repeated rolling. Therefore, the main wear mechanisms of the Ni-20% Ti3AlC2 coating surface in the oil lubrication friction and wear test are abrasive wear and adhesive wear.

[0159] (26) The grinding mark morphology of the Ni-40% Ti3AlC2 coating after 30 min of friction and wear under oil lubrication is shown in Figure 29 , where (a) is 500x, and (b) is 1000x.

[0160] From the Figure 29 (a) low-magnification grinding mark morphology, it can be clearly observed that the grinding mark on the surface of the Ni-40% Ti3AlC2 coating is about 508 μm wide, the coating grinding mark surface is rough, and there are furrows of different widths and depths. Similar to the grinding mark morphology of the Ni-20% Ti3AlC2 coating. However, from the Figure 29(b) In the high-magnification morphology of the wear scar, it can be seen that there is a significant difference from the wear scar morphology of the Ni-20% Ti3AlC2 coating. There are many wide and deep furrows, fish-scale-like cracks, and peeling defects on the wear scar surface of the Ni-40% Ti3AlC2 coating, accompanied by a small amount of wear debris. The wide and deep furrows on the coating surface can be clearly observed, mainly due to the increase in the content of Ti3AlC2 ceramic particles in the coating. During the wear process, the exposed Ti3AlC2 ceramic particles do not break due to low stress, but scratch the coating surface, causing wear and forming multiple furrows of different depths. Under oil lubrication conditions, the contact pressure between the friction pair will squeeze the lubricating oil into the micro-cracks at a very high speed, causing the crack wall to be impacted. The repeated friction process causes the micro-cracks to gradually deepen and widen, and when the root structure strength of the coating on both sides of the crack is not enough, pitting will occur. At the same time, fish-scale-like cracks are observed on the wear scar surface of the coating. This may be due to the presence of pores on the coating surface. The lubricating oil present in the pores is squeezed by the load to produce high pressure, causing plastic deformation of the coating surface under the action of repeated extrusion and friction shear force. On the other hand, under the action of cyclic load, the micro-cracks expand into fish-scale-like cracks under the action of normal load and shear force along the rolling direction, which are distributed on the wear scar surface. Some scholars call this "alligatoring", which is the result of crack propagation in different directions. Therefore, the wear mechanism of the Ni-40% Ti3AlC2 coating under oil lubrication friction and wear test is mainly abrasive wear and fatigue wear.

[0161] (27) The wear scar morphology of the Ni-50% Ti3AlC2 coating after 30 min of friction and wear under oil lubrication friction conditions is shown in Figure 30 , where (a) is 500x, and (b) is 1000x.

[0162] From Figure 30 (a) it can be seen that there are a large number of pitting left by wear debris falling off on the wear scar surface of the coating, as well as mechanical wear caused by the scratches on the coating surface by brittle Ti3AlC2 hard particles and Ni metal wear debris. However, from Figure 30(b) In the high-magnification morphology of the grinding track, it can be seen that there are many furrows with different widths, depths and lengths on the surface of the coating grinding track. Near the deeper furrows, there are pits, cracks and grinding debris layers, which show the characteristics of abrasive wear, adhesive wear and fatigue wear. This is because the adhesion band breaks to produce tiny grinding debris, and then the friction surface appears pits. At the same time, during the process of friction and wear, the Ni-50%Ti3AlC2 coating has the highest Ti3AlC2 ceramic content, the dense microstructure, low porosity, high hardness and the best bonding strength, which means that the wear resistance of the coating is the best. In the process of wear, the GCr15 ball will crush and bury the grinding debris in the grinding track, reducing the friction loss, so the maximum grinding track depth and wear volume of the Ni-50%Ti3AlC2 coating are much lower than those of the Ni-Ti3AlC2 composite coating. Secondly, the wear of the coating is reduced due to the presence of lubricating oil, the wrapping time of Ti3AlC2 ceramic particles is prolonged, and the supporting load of Ti3AlC2 hard particles is also prolonged, so the wear resistance of the composite coating is also improved. At the same time, it also helps to store a certain amount of lubricating oil, so as to form a continuous lubricating oil film to play a certain effect of lubrication and friction reduction. Therefore, the wear mechanism of the Ni-50%Ti3AlC2 coating in the oil lubrication friction and wear test is mainly abrasive wear, fatigue wear and adhesive wear.

[0163] The friction coefficients and wear rates of the substrate and the Ni-Ti3AlC2 composite coating under dry friction conditions and oil lubrication conditions are summarized in Table 4.

[0164] Table 4 Friction coefficients and wear rates of the coating under different lubrication conditions

[0165]

[0166] As can be seen from Table 4, under dry friction conditions and oil lubrication conditions, with the increase of Ti3AlC2 ceramic content in the coating, the friction coefficient of the Ni-Ti3AlC2 composite coating is slowly reduced, and the wear rate of the Ni-50%Ti3AlC2 coating is reduced by 86.4% and 63.5% respectively under dry friction conditions and oil lubrication conditions compared with the Ni-20%Ti3AlC2 coating. The reasons for the improvement of the wear resistance of the Ni-Ti3AlC2 composite coating are as follows:

[0167] 1) During the wear process, the pores and cracks in the coating can make the material easily separate from the coating and accelerate the loss of the material. The Ni-50%Ti3AlC2 coating has lower porosity, higher ceramic content, dense microstructure and the best mechanical properties compared with the Ni-20%Ti3AlC2 coating and the Ni-40%Ti3AlC2 coating, and the hard particles in the composite coating can effectively prevent the crack propagation, so the Ni-50%Ti3AlC2 coating has better wear resistance.

[0168] 2) Ni-50%Ti3AlC2 coating retained the highest ceramic content, the dispersion of Ti3AlC2 ceramic hard particles in the coating improved the load capacity of the coating, and in turn effectively improved the wear resistance of the Ni-50%Ti3AlC2 coating.

[0169] 3) In the oil friction test under oil lubrication conditions, the Ti3AlC2 hard particles due to brittle fracture in the Ni-Ti3AlC2 composite coating wear surface play a supporting role, which helps to store more lubricating oil, thereby forming a thicker continuous lubricating oil film, which has a lubricating and friction reducing effect on the composite coating.

[0170] Performance test method:

[0171] (1) The coating hardness test refers to GB4340.1-1999 "Metal Micro Vickers Hardness Test Method";

[0172] (2) The elastic modulus is measured by indentation method, the sample cross section is polished before testing, the nano indentation instrument of U9820A of American Agilent G200 type is used to measure the elastic modulus of the coating, the loading load is 100 mN, the loading time is 10 s, and the holding time is 10 s. The test method of elastic modulus of composite coating is to measure one point every 50 μm in the middle of the dense structure of the coating section, take 5 points to measure the elastic modulus and take the average value as the final test result;

[0173] (3) The fracture toughness of the composite coating is measured by indentation method (schematic diagram of indentation method as shown in Figure 31 ), using U9820A nano indentation instrument of American Agilent G200 type, load 100 mN, loading time 15 s. Then use scanning electron microscope to take pictures of the indentation, measure the indentation and crack length. Select three control samples during testing, and the test results are averaged. According to the indentation fracture theory, use formula (2.1) to calculate the fracture toughness of the coating:

[0174]

[0175] In the formula, HV is the microhardness of the coating, E is the elastic modulus (GPa), C is the crack length (mm), P is the loading load (Kg), and δ is the empirical constant, which is related to the shape of the indenter. For Vickers hardness tester indenter, δ takes 0.016;

[0176] (4) Coating adhesion strength was measured by GB / T 8642-2002 using a CMT5105 microcomputer-controlled electronic universal testing machine. The sample size was φ25 mm x 10 mm. E7 glue was used to bond the sample substrate surface and the test column and coating surface and the test column. According to the requirements of the epoxy glue, after the sample and the test column were completely centered, they were evenly knocked and compacted with a hammer, then fixed with heat-resistant tape to avoid displacement of the test column and the sample during the heating and curing process. Then, the sample was placed in an oven at room temperature and heated to 185°C for 3 hours, then naturally cooled with the oven temperature, then removed the tape and stored for 24 hours before testing. The loading speed was 10 mm / min. Three samples were tested for each group of coatings, and the average value was taken as the final test result. The coating adhesion strength test schematic is shown in Fig. 6. Figure 32

[0177] (5) Dry friction and wear test

[0178] The SRV-4 micro-tribological wear tester (Optimol Instruments, Germany) was used to test the dry friction performance of the Ni-Ti3AlC2 coating. The dry friction test parameters are listed in Table 5. One parallel sample was selected for testing in three different areas. The sample size was φ24 mm*8 mm, and the counter-ball material was GCr15 with a diameter of 10 mm. The point-plane contact reciprocating motion was used, Figure 33 The test principle is shown in the schematic diagram. Before testing, the coating surface was polished with 400, 800, 1000, 1200, 1500, and 2000 grit sandpaper, then polished to a surface roughness Ra value of not more than 0.2 μm, and then cleaned with alcohol to maintain the cleanliness of the test surface. After testing, the micro-morphology of the wear track was characterized using a scanning electron microscope, and the wear volume of the sample was obtained by scanning the wear track morphology using a Phase Shift MicroXAM-3D white light interferometric three-dimensional morphology instrument. The wear rate of the sample was calculated according to formula (2.2). In the formula, W is the wear rate (mm 3 / N·m), V is the wear volume (mm 3 ), P is the loading load (N), and S is the total travel of the wear track (m).

[0179]

[0180] Table 5 Test parameters for friction test

[0181]

[0182] (6) Oil lubricated friction and wear test

[0183] ​The oil-lubricated friction performance of the composite coating was tested using an SRV-4 fretting friction and wear testing machine (Optimol Instruments, Germany). The test parameters for the oil-lubricated friction test are shown in Table 5. Three parallel specimens were used for both types of cold-sprayed coatings. The specimen dimensions were φ24mm*7.88mm, and the friction ball was a 10mm diameter GCr15 steel ball (hardness 61HRC). The motion was a point-to-line contact reciprocating motion. J600 lubricating oil produced by Sinopec Lubricating Oil Co., Ltd. was used for the oil-lubricated friction test, with a kinematic viscosity of 15.16 mm. 2 / s, before each test, 0.15ml of lubricating oil is dripped into the contact area between the friction ball and the coating surface to be tested. Before the test, the coating surface is polished with 400 grit, 800 grit, 1000 grit, 1200 grit, 1500 grit and 2000 grit sandpaper in sequence, and then polished. The surface roughness Ra value is measured to be no more than 0.2μm. Afterwards, ultrasonic cleaning with alcohol is performed to keep the test surface clean. After the test, the wear morphology is scanned with a Phase Shift MicroXAM-3D white light interferometer to obtain the wear volume of the substrate and coating, and the wear rate of the sample is calculated using formula (2.2). The micromorphology of the wear tracks is characterized using a JSM-6510A scanning electron microscope from Japan Electronics.

[0184] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing a cold-sprayed nickel-based titanium-aluminum-carbon composite coating, characterized in that, Includes the following steps: A cold-sprayed nickel-based titanium-aluminum-carbon composite coating is obtained by cold spraying composite powder onto the surface of a pretreated substrate material. The composite powder includes Ni powder and Ti3AlC2 powder; The base material is an aluminum alloy; The method for preparing the composite powder is as follows: the Ni powder and Ti3AlC2 powder are mechanically mixed and dried sequentially; The mass ratio of Ni powder to Ti3AlC2 powder is (5~8):(2~5); The average particle size of the Ni powder is 10~50μm; the average particle size of the Ti3AlC2 powder is 10~50μm; The Ni powder includes spherical particles and irregularly shaped particles; the Ti3AlC2 powder has an irregular layered polygonal morphology; The parameters for cold spraying include: nitrogen as the powder feeding gas, 3-5 MPa as the spraying pressure, 500-700℃ as the spraying temperature, 10-20 mm as the spraying distance, 90° as the spraying angle, 8-12 reciprocating strokes of the spray gun, and 300-400 mm / s as the spray gun speed.

2. The preparation method according to claim 1, characterized in that, The pretreatment includes: sequentially subjecting the matrix material to a first ultrasonic cleaning, a first drying, a sandblasting roughening treatment, a second ultrasonic cleaning, and a second drying.

3. The preparation method according to claim 2, characterized in that, The particle size of the sand used in the sandblasting roughening treatment is 500~700μm; the sandblasting angle of the sandblasting roughening treatment is 70~80°, the sandblasting distance is 180~240mm, and the pressure is 0.7~0.8MPa; the surface roughness Sq of the substrate material after the sandblasting roughening treatment is 10~12.8μm, and the surface roughness Sa is 5~7.81μm.

4. The preparation method according to claim 2, characterized in that, The cleaning solution used for the first and second ultrasonic cleaning is anhydrous ethanol; the frequency of the first and second ultrasonic cleaning is independently 28~40kHz, and the time is independently 5~10min.

5. The cold-sprayed nickel-based titanium-aluminum-carbon composite coating prepared by the preparation method according to any one of claims 1 to 4, characterized in that, The chemical composition includes Ni and Ti3AlC2. The thickness of the cold-sprayed nickel-based titanium-aluminum-carbon composite coating is 500~800μm, the porosity is 0.3~0.6%, and the hardness is 242~310HV. 0.2 .

6. The application of the cold-sprayed nickel-based titanium-aluminum-carbon composite coating as described in claim 5 in the equipment of lightweight engines.

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