Cold spraying method for agglomerated silicon carbide particle reinforced aluminum-based composite coating

Abstract

The invention belongs to the technical field of spraying, and provides a cold spraying method of an agglomerated silicon carbide particle reinforced aluminum-based composite coating, which comprises the following steps: step 1, based on a pre-ceramic pyrolysis technology, obtaining agglomerated silicon carbide particles with the average size of 50 microns; 2, performing low-energy ball milling on the agglomerated silicon carbide particles and the aluminum powder by using a ball mill, so that the agglomerated silicon carbide particles and the aluminum powder are uniformly mixed to obtain mixed powder of silicon carbide and the aluminum powder; thirdly, the mixed powder obtained in the second step is sprayed to a base material in a cold spraying mode; according to the method, agglomerated silicon carbide particles are prepared through a pre-ceramic pyrolysis technology, the stability of ceramic particles in the cold spraying process is effectively improved, uniform distribution of the ceramic particles in an aluminum matrix is promoted, and through introduction of the agglomerated silicon carbide particles, the hardness and wear resistance of the composite coating are remarkably improved; meanwhile, due to the fact that the ceramic particles are evenly distributed in the aluminum matrix, stress concentration is reduced, and the overall mechanical property of the coating is improved.

Description

Technical Field

[0001] This invention belongs to the field of spraying technology, specifically a cold spraying method for an agglomerated silicon carbide particle-reinforced aluminum-based composite coating. Background Technology

[0002] ZE41 magnesium alloys are widely used in the automotive, aerospace, electronics, and biomedical fields due to their high-temperature strength, good creep resistance, excellent castability, and biocompatibility. However, in outdoor environments where they may be exposed to air and saline conditions, such as acid rain and salt in humid air, ZE41 magnesium alloys are susceptible to corrosion, affecting their lifespan and performance. Therefore, improving the surface properties of ZE41 magnesium alloys, especially their wear resistance and corrosion resistance, is crucial for manufacturing structural components for engineering applications.

[0003] Currently, traditional surface treatment technologies, such as thermal spraying, anodizing, plasma electrolytic oxidation, physical vapor deposition, and laser surface modification, can improve the surface properties of magnesium alloys to some extent, but they suffer from drawbacks such as heterogeneity with the matrix particles, porosity, material oxidation, and high cost. In particular, when preparing high-volume-fraction ceramic particle-reinforced metal matrix composites (MMCs), traditional methods often struggle to address issues such as uneven ceramic particle distribution, fragility, and rebound, leading to a decline in coating performance. Cold spraying (CS) technology, as a relatively new coating process, accelerates micron-sized ductile particles to supersonic speeds using compressed gas to impact the substrate, forming a coating.

[0004] However, this technology relies on the high-speed impact of particles to generate plastic deformation to achieve deposition, avoiding problems such as phase transformation, oxidative degradation and thermal decomposition caused by high temperature. It has become a more efficient and promising preparation method for the repair and protection of magnesium alloy surfaces. However, in the preparation of aluminum-based composite coatings reinforced with high volume fraction ceramic particles, there are still challenges such as the ceramic particles being easily broken and unevenly distributed.

[0005] To address these issues, those skilled in the art have proposed a cold spraying method for agglomerated silicon carbide particle-reinforced aluminum-based composite coatings. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a cold spraying method for agglomerated silicon carbide particle-reinforced aluminum-based composite coatings. This method overcomes the limitations of existing technologies that rely on high-speed impact of particles to induce plastic deformation for deposition, thus avoiding problems such as phase transformation, oxidative degradation, and thermal decomposition caused by high temperatures. This method represents a more efficient and promising preparation method for the repair and protection of magnesium alloy surfaces. Furthermore, the preparation of aluminum-based composite coatings reinforced with high volume fraction ceramic particles still faces challenges such as the fragility and uneven distribution of ceramic particles.

[0007] This invention provides a cold spraying method for agglomerated silicon carbide particle-reinforced aluminum-based composite coating, comprising the following steps:

[0008] Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained;

[0009] The pre-ceramic pyrolysis process includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30 to 60:40. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0010] The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 200-300 r / min, the ball milling is carried out for 2-4 hours, the ball milling jar rotates in one direction, and stops for 5-10 minutes every 0.5-1 hours of ball milling to obtain mixed powder.

[0011] Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder.

[0012] The mass ratio of the aluminum powder to the agglomerated silicon carbide particles coated with nickel is 3:1-2.

[0013] The low-energy ball milling process is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 150-200 r / min, the ball milling time is 2-4 h, the ball milling jar rotates in one direction, and stops for 5-10 min every 0.5-1 h of ball milling to obtain mixed powder;

[0014] Step 3: Apply the mixed powder obtained in Step 2 onto the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

[0015] The cold spraying process is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 5-30 minutes, dried, and then sandblasted. After the sandblasting is completed, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in step two is poured into the powder feeder. After fixing the substrate, cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped, the spacing between spraying trajectory lines is 2-3 mm, the spraying beam is at 90° to the surface to be sprayed, the gun speed is 150-200 mm / s, the vertical distance between the gun nozzle and the surface to be sprayed is 30-35 mm, the chamber air pressure is 3.5-4.5 MPa, the chamber gas temperature is 500-600℃, and the coating is applied several times according to the required coating thickness.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. The agglomerated silicon carbide particles prepared by the pre-ceramic pyrolysis technology of this invention effectively improve the stability of ceramic particles during cold spraying, reduce defects caused by breakage, rebound and detachment, and promote the uniform distribution of ceramic particles in the aluminum matrix.

[0018] 2. This invention significantly improves the hardness and wear resistance of the composite coating by introducing agglomerated silicon carbide particles. Simultaneously, the uniform distribution of ceramic particles within the aluminum matrix reduces stress concentration and improves the overall mechanical properties of the coating.

[0019] 3. This invention effectively avoids the problems of phase transformation, oxidative degradation, and thermal decomposition associated with traditional high-temperature deposition techniques by utilizing the low-temperature characteristics of cold spraying technology, making the coating preparation process more stable and controllable. Simultaneously, by optimizing the cold spraying process parameters, the efficient preparation of high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coatings is achieved.

[0020] 4. This invention not only provides a new strategy for preparing ceramic particle-reinforced metal matrix composite coatings by cold spraying, but also opens up new prospects for various ceramic particles to fully exert their reinforcing properties. It is particularly suitable for engineering applications with high requirements for wear resistance, corrosion resistance and oxidation resistance. Attached Figure Description

[0021] Figure 1 This is a SEM image of the agglomerated silicon carbide particles obtained in step one of Example 1.

[0022] Figure 2 The image shows the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 1.

[0023] Figure 3 This is a SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating obtained by cold spraying in step three of Example 1.

[0024] Figure 4 This is a SEM image of the agglomerated silicon carbide particles obtained in step one of Example 2;

[0025] Figure 5 The image shows the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 2.

[0026] Figure 6 This is a SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating obtained by cold spraying in step three of Example 2.

[0027] Figure 7 This is a SEM image of the agglomerated silicon carbide particles obtained in step one of Example 3;

[0028] Figure 8 The particle size distribution of the agglomerated silicon carbide particles obtained in step one of Example 3 is shown below.

[0029] Figure 9 XPS image of the agglomerated silicon carbide particles obtained in step one of Example 3;

[0030] Figure 10 The image shows the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3.

[0031] Figure 11 This is a SEM image of the distribution of silicon carbide particles inside the cross-section of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3.

[0032] Figure 12 The image shows the SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3. Detailed Implementation

[0033] The embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and should not be construed as limiting the scope of the invention.

[0034] Specific Implementation Method 1: The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating in this implementation method is carried out according to the following steps:

[0035] Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained;

[0036] The pre-ceramic pyrolysis process includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30 to 60:40. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0037] The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 200-300 r / min, the ball milling is carried out for 2-4 hours, the ball milling jar rotates in one direction, and stops for 5-10 minutes every 0.5-1 hours of ball milling to obtain mixed powder.

[0038] Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder.

[0039] The mass ratio of the aluminum powder to the agglomerated silicon carbide particles coated with nickel is 3:1-2.

[0040] The low-energy ball milling process is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 150-200 r / min, the ball milling time is 2-4 h, the ball milling jar rotates in one direction, and stops for 5-10 min every 0.5-1 h of ball milling to obtain mixed powder;

[0041] Step 3: Apply the mixed powder obtained in Step 2 onto the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

[0042] The cold spraying process is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 5-30 minutes, dried, and then sandblasted. After the sandblasting is completed, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in step two is poured into the powder feeder. After fixing the substrate, cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped, the spacing between spraying trajectory lines is 2-3 mm, the spraying beam is at 90° to the surface to be sprayed, the gun speed is 150-200 mm / s, the vertical distance between the gun nozzle and the surface to be sprayed is 30-35 mm, the chamber air pressure is 3.5-4.5 MPa, the chamber gas temperature is 500-600℃, and the coating is applied several times according to the required coating thickness.

[0043] This embodiment has the following beneficial effects:

[0044] 1. We propose a silicon carbide agglomeration strategy based on pre-ceramic pyrolysis technology. 20μm silicon carbide particles are used as precursors to prepare 50μm silicon carbide particles by pyrolysis of silicone resin powder with good cohesiveness. This improves the stability of silicon carbide particles in high-content SiCp / Al composite coatings prepared by cold spraying, reduces defects caused by silicon carbide particle breakage, rebound, and detachment, increases the deposition threshold of the ceramic phase, promotes uniform distribution of silicon carbide particles in the aluminum matrix, reduces stress concentration, and improves the mechanical properties of the composite coating.

[0045] 2. This invention employs cold spraying technology, enabling coating deposition at relatively low temperatures (typically several hundred degrees Celsius) and high deposition rates (often achieving millimeter-thickness coatings per minute). The adhesion / cohesion of the deposited particles is achieved through localized metallurgical bonding or mechanical anchoring. Since formation relies primarily on pre-impact kinetic energy rather than thermal energy, the raw materials used for cold spraying remain solid throughout the deposition process. Deposition is achieved through localized metallurgical bonding and mechanical interlocking caused by localized plastic deformation at the particle-particle and particle-substrate interfaces. This avoids the limitations associated with high temperatures, such as phase transformation, tensile residual stress, and significant torsion, making cold spraying a competitive deposition technology for various materials. The resulting coatings exhibit excellent microstructure and mechanical properties, with thicknesses ranging from tens of micrometers to tens of millimeters, and high bonding strength between the coating and the substrate, resulting in aluminum-based composite coatings with superior oxidation resistance, corrosion resistance, and wear resistance.

[0046] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the pre-ceramic pyrolysis technology treatment described in step one includes the following steps: First, 20μm silicon carbide particles and high-cohesion silicone resin powder (particle size <10μm) are dry-milled and mixed at a volume ratio of 70:30. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; pyrolysis and degassing at 400-800℃, causing the organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1300℃; and holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles, followed by furnace cooling. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0047] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that: during the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology described in step 1, when degassing at 400-800℃, the heating rate is kept less than 2℃ / min to slowly release the pyrolysis gas and avoid porosity.

[0048] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: during the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology described in Step One, after densification at 1200-1400℃, the holding time at 1300℃~1400℃ is 1~1.5h.

[0049] Specific Implementation Method 5: This implementation method differs from one of the specific implementation methods one to four in that the purity of the silicon carbide particles mentioned in step one is 99.9%, the particles are irregular in shape, and the average particle size is 20μm.

[0050] Specific Implementation Method Six: This implementation method differs from Specific Implementation Method Five in that the aluminum powder mentioned in step two has a purity of 99.9%, the particles are spherical, and the particle size is 15-50μm.

[0051] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that the ball mill mentioned in steps One and Two is a planetary ball mill.

[0052] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the dry ball milling process described in step one is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated, and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 4:1, the ball milling speed is 300r / min, the ball milling is carried out for 2 hours, the ball milling jar rotates in one direction, and stops for 5 minutes every 0.5 hours of ball milling to obtain mixed powder.

[0053] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the low-energy ball milling process described in step two is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated, and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3:1, the ball milling speed is 200 r / min, the ball milling is carried out for 2 hours, the ball milling jar rotates in one direction, and stops for 10 minutes every 0.5 hours of ball milling to obtain mixed powder.

[0054] Specific Implementation Method Ten: This implementation method differs from Specific Implementation Methods One to Nine in that: the cold spraying process described in step three is as follows: the substrate to be sprayed is ultrasonically cleaned with anhydrous ethanol for 30 minutes, dried after removal, and then sandblasted. After the treatment is completed, the surface to be sprayed is cleaned with an air gun; the mixed powder obtained in step two is poured into the powder feeder, the substrate is fixed and then cold sprayed, nitrogen is used as the powder feeder, the cold spray trajectory is S-shaped, the spacing between spray trajectory lines is 3mm, the spray beam is at 90° to the surface to be sprayed, the gun speed is 200mm / s, the vertical distance between the gun nozzle and the surface to be sprayed is 30mm, the chamber air pressure is 4MPa, the chamber gas temperature is 600℃, and the number of spraying times is 3.

[0055] Example 1:

[0056] The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating in this embodiment is carried out according to the following steps:

[0057] Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained;

[0058] The pre-ceramic pyrolysis technology includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0059] The silicon carbide particles have a purity of 99.9%, are irregularly shaped, and have an average particle size of 20 μm.

[0060] The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling with a ball-to-material ratio of 4:1, a ball milling speed of 300 r / min, and a milling time of 2 hours. The ball milling jar rotates in one direction and stops for 5 minutes every 0.5 hours of milling to obtain mixed powder.

[0061] The ball mill is a planetary ball mill;

[0062] During the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology, when the pyrolysis and degassing occurs at 400-800℃, the heating rate is kept less than 2℃ / min to slowly release the pyrolysis gas and avoid porosity.

[0063] During the segmented temperature-controlled pyrolysis process treated by the pre-ceramic pyrolysis technology, after densification at 1200-1400℃, the temperature is held at 1400℃ for 1.5 hours.

[0064] Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder.

[0065] The mass ratio of the aluminum powder to the agglomerated silicon carbide particles coated with nickel is 3:2.

[0066] The aluminum powder has a purity of 99.9%, and the particles are spherical with a particle size of 15-50 μm.

[0067] The low-energy ball milling process is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling with a ball-to-material ratio of 3:1, a ball milling speed of 200 r / min, and a milling time of 2 hours. The ball milling jar rotates in one direction and stops for 10 minutes every 0.5 hours of milling to obtain mixed powder.

[0068] The ball mill is a planetary ball mill;

[0069] Step 3: Apply the mixed powder obtained in Step 2 onto the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

[0070] The cold spraying process is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 30 minutes, dried, and then sandblasted. After the sandblasting is completed, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in step two is poured into the powder feeder. After fixing the substrate, cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped with a line spacing of 3 mm. The spray beam is at a 90° angle to the surface to be sprayed. The gun speed is 200 mm / s. The vertical distance between the gun nozzle and the surface to be sprayed is 30 mm. The chamber pressure is 4 MPa and the chamber temperature is 500°. The required coating thickness is achieved by spraying three times.

[0071] The agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained in this embodiment is thick and dense, with good adhesion to the substrate. No obvious microstructural defects, such as cracks or voids, were detected in this area. Due to their low ductility, the high-hardness silicon carbide particles are randomly embedded in the metal matrix without exhibiting any obvious deformation, providing a good compaction and anchoring effect for the composite coating. In this way, the silicon carbide particles support the metal matrix and provide a more uniform distribution of hard ceramic particles, resulting in higher hardness, wear resistance, corrosion resistance, and oxidation resistance of the composite coating. Figure 1 The image shows an SEM image of the agglomerated silicon carbide particles obtained in step one of Example 1. This illustrates that the silicon carbide particles subjected to the pre-ceramic pyrolysis technology have irregular surface shapes, high roughness, smooth edges, and fewer sharp corners. Figure 2 The image shows the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating obtained by cold spraying in step three of Example 1; this demonstrates that the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating was successfully prepared by cold spraying technology. Figure 3 The image shows the SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating obtained by cold spraying in step three of Example 1. This illustrates that the degree of fragmentation of the agglomerated silicon carbide in the coating is reduced, and the fragmentation causes fewer cracks in the surrounding area.

[0072] Example 2:

[0073] The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating in this embodiment is carried out according to the following steps:

[0074] Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained;

[0075] The pre-ceramic pyrolysis technology includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0076] The silicon carbide particles have a purity of 99.9%, are irregularly shaped, and have an average particle size of 20 μm.

[0077] The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3:1, the ball milling speed is 300r / min, the ball milling is carried out for 2 hours, the ball milling jar rotates in one direction, and stops for 10 minutes every 0.5 hours of ball milling to obtain mixed powder.

[0078] The ball mill is a planetary ball mill;

[0079] During the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology, when the pyrolysis and degassing occurs at 400-800℃, the heating rate is kept less than 2℃ / min to slowly release the pyrolysis gas and avoid porosity.

[0080] During the segmented temperature-controlled pyrolysis process treated by the pre-ceramic pyrolysis technology, after densification at 1200-1400℃, the temperature is held at 1300℃ for 1.5 hours.

[0081] Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder.

[0082] The mass ratio of the aluminum powder to the agglomerated silicon carbide particles coated with nickel is 3:2.

[0083] The aluminum powder has a purity of 99.9%, and the particles are spherical with a particle size of 15-50 μm.

[0084] The low-energy ball milling process is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling with a ball-to-material ratio of 3:1, a ball milling speed of 200 r / min, and a milling time of 2 hours. The ball milling jar rotates in one direction and stops for 10 minutes every 0.5 hours of milling to obtain mixed powder.

[0085] The ball mill is a planetary ball mill;

[0086] Step 3: Apply the mixed powder obtained in Step 2 onto the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

[0087] The cold spraying process is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 30 minutes, dried, and then sandblasted. After the sandblasting is completed, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in step two is poured into the powder feeder. After fixing the substrate, cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped with a line spacing of 3 mm. The spray beam is at a 90° angle to the surface to be sprayed. The gun speed is 200 mm / s. The vertical distance between the gun nozzle and the surface to be sprayed is 30 mm. The chamber pressure is 4 MPa and the chamber gas temperature is 600°. The required coating thickness is achieved by spraying three times.

[0088] The agglomerated silicon carbide particles obtained in this embodiment retain the original irregular shape and structure of SiCp, with a significantly increased surface roughness. The thickness and deposition amount of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating are increased. A considerable number of SiCp particles fractured upon impact, and even secondary fracture particles were observed. This fracture behavior did not lead to the formation of pores or radial microcracks within the coating. The coating exhibits good interfacial bonding with the substrate, increasing the surface hardness, wear resistance, corrosion resistance, and oxidation resistance of the magnesium alloy while preventing separation of the coating and substrate due to external environmental influences. Furthermore, the improved interfacial bonding extends the service life of the protective coating on the magnesium alloy surface. Figure 4 The image shows an SEM image of the agglomerated silicon carbide particles obtained in step one of Example 2; irregular silicon carbide morphology and small silicon carbide particles of different sizes attached to the surface are observed. Figure 5 This is a SEM image of the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating obtained by cold spraying in step three of Example 2; it shows that the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating was successfully prepared by cold spraying technology. Figure 6 The image shows the SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 2. It can be observed that the silicon carbide particles did not produce cracks or pores after the violent collision, and the fragmented silicon carbide particles at the edges were encapsulated by aluminum and distributed in the coating.

[0089] Example 3:

[0090] The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating in this embodiment is carried out according to the following steps:

[0091] Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained;

[0092] The pre-ceramic pyrolysis technology includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing organic groups (-CH3, etc.) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, resulting in chemical sintering, shrinkage, and agglomeration between particles; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of approximately 50μm are sieved out.

[0093] The silicon carbide particles have a purity of 99.9%, are irregularly shaped, and have an average particle size of 20 μm.

[0094] The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling with a ball-to-material ratio of 4:1, a ball milling speed of 300 r / min, and a milling time of 2 hours. The ball milling jar rotates in one direction and stops for 5 minutes every 0.5 hours of milling to obtain mixed powder.

[0095] The ball mill is a planetary ball mill;

[0096] During the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology, when the pyrolysis and degassing occurs at 400-800℃, the heating rate is kept less than 2℃ / min to slowly release the pyrolysis gas and avoid porosity.

[0097] During the segmented temperature-controlled pyrolysis process treated by the pre-ceramic pyrolysis technology, after densification at 1200-1400℃, the temperature is held at 1300℃ for 1 hour.

[0098] Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder.

[0099] The mass ratio of the aluminum powder to the agglomerated silicon carbide particles coated with nickel is 3:2.

[0100] The aluminum powder has a purity of 99.9%, and the particles are spherical with a particle size of 15-50 μm.

[0101] The low-energy ball milling process is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling with a ball-to-material ratio of 3:1, a ball milling speed of 200 r / min, and a milling time of 2 hours. The ball milling jar rotates in one direction and stops for 10 minutes every 0.5 hours of milling to obtain mixed powder.

[0102] The ball mill is a planetary ball mill;

[0103] Step 3: Apply the mixed powder obtained in Step 2 onto the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

[0104] The cold spraying process is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 30 minutes, dried, and then sandblasted. After the sandblasting is completed, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in step two is poured into the powder feeder. After fixing the substrate, cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped, the spacing between spraying trajectory lines is 3 mm, the spraying beam is at 90° to the surface to be sprayed, the gun speed is 200 mm / s, the vertical distance between the gun nozzle and the surface to be sprayed is 30 mm, the chamber pressure is 4.5 MPa, the chamber gas temperature is 600℃, and the required coating thickness is achieved by spraying three times.

[0105] The silicon carbide particles obtained in this embodiment are ideally agglomerated powders. This agglomerated, coarse microstructure enhances the mechanical interlocking with the aluminum substrate during subsequent cold spraying to prepare high-content composite coatings. Furthermore, the coarse microstructure also limits the impact velocity of SiCp to some extent, reducing the high contact stress during silicon carbide particle collisions. The resulting agglomerated silicon carbide particle-reinforced aluminum-based composite coating is the thickest, approaching 2 mm, with a significant improvement in deposition efficiency. The coating is dense, exceeding the upper limit of silicon carbide content and showing improved uniformity. This indicates that increasing the ceramic particle content is a direct and effective strategy for optimizing its distribution uniformity, essentially stemming from the geometric constraint effect caused by reduced particle spacing. Simultaneously, after severe impact and deformation, the silicon carbide is tightly encapsulated and embedded in the matrix by aluminum, exhibiting a continuous transition at the interface, demonstrating good adhesion, and showing no delamination or crack initiation. This improves the stability of silicon carbide particles in the composite coating, enhances the mechanical interlocking with aluminum, exhibits good structural integrity, and maintains a stable mechanical interlocking structure at the interface. Furthermore, this synergistic retention effect of cross-particle structure plays a crucial role in increasing the silicon carbide content in the coating, enhancing the hard phase strengthening effect and crack deflection efficiency, and improving the overall performance of the composite coating. Applying a high content of reinforcing particles to the surface of ZE41 magnesium alloy can significantly improve its wear resistance, thermal shock resistance, and oxidation resistance. Figure 7 This is a SEM image of the agglomerated silicon carbide particles obtained in step one of Example 3; the surface morphology of small-sized particles agglomerated into large-sized particles can be clearly observed; Figure 8 The particle size distribution is shown in step one of Example 3, where the agglomerated silicon carbide particles are obtained. The final screened powder has a D50 of approximately 54.91. Figure 9 XPS image of agglomerated silicon carbide particles obtained in step one of Example 3; the agglomerated silicon carbide obtained by the pre-ceramic pyrolysis technology has higher purity and fewer impurities;

[0106] Figure 10 The image shows the cross-sectional morphology of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3; the thickness of the composite coating is 1.77 mm. Figure 11 The image shows the SEM image of the distribution of silicon carbide particles inside the cross section of the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3. It can be observed that the composite coating exhibits a multi-scale SiCp coexistence phenomenon in the coating cross section region. Submicron-sized fragments (<5μm) in the high-speed impact zone and intact particles (15-30μm) in the medium-low speed zone are randomly distributed and there are no cracks. Figure 12The image shows the SEM image of the fragmented silicon carbide morphology inside the agglomerated silicon carbide particle-reinforced aluminum-based composite coating obtained by cold spraying in step three of Example 3. It can be seen that the coating is dense, and no cracks are generated after the silicon carbide is fragmented. Silicon carbide of various sizes is embedded in the coating.

[0107] The embodiments of the present invention are given for the purposes of illustration and description. Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Any changes, modifications, substitutions and variations made by those skilled in the art to the above embodiments within the scope of the present invention should be included within the protection scope of the present invention.

Claims

1. A cold spraying method for an agglomerated silicon carbide particle-reinforced aluminum-based composite coating, characterized in that: The cold spraying method for agglomerated silicon carbide particle-reinforced aluminum-based composite coatings is carried out according to the following steps: Step 1: Based on pre-ceramic pyrolysis technology, agglomerated silicon carbide particles with an average size of 50 μm are obtained; Step 2: Use a ball mill to perform low-energy ball milling on agglomerated silicon carbide particles and aluminum powder to uniformly mix the agglomerated silicon carbide particles and aluminum powder, and obtain a mixed powder of silicon carbide and aluminum powder. Step 3: Apply the mixed powder obtained in Step 2 to the substrate using cold spraying to obtain a high-content agglomerated silicon carbide particle-reinforced aluminum-based composite coating.

2. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 1, characterized in that: Step 1, the pre-ceramic pyrolysis process, includes the following steps: First, 20μm silicon carbide particles are dry-milled and mixed with high-cohesion polysiloxane silicone resin powder (particle size <10μm) at a volume ratio of 70:30 to 60:

40. Second, in an inert atmosphere (Ar), segmented temperature-controlled pyrolysis is performed: low-temperature crosslinking at 200-400℃ to crosslink and solidify the silicone resin, enhancing cohesion; degassing at 400-800℃, causing the organic groups (-CH3) in the resin to decompose into CH4 / H2, forming active amorphous Si-OC; interfacial bonding at 800-1200℃, where the amorphous Si-OC reacts with the SiCp surface, forming SiC nanocrystal bridges between the silicon carbide particles; densification at 1200-1400℃; holding at the final temperature, where chemical sintering occurs between the particles, causing shrinkage and agglomeration; and cooling in the furnace. Finally, acid washing and purification are performed, and agglomerated silicon carbide particles with a particle size of about 50μm are sieved out.

3. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 2, characterized in that: In the segmented temperature-controlled pyrolysis process of the pre-ceramic pyrolysis technology described in step one, during the pyrolysis and degassing at 400-800℃, the heating rate is kept less than 2℃ / min to slowly release the pyrolysis gas and avoid porosity; after densification at 1200-1400℃, the temperature is kept at 1300℃~1400℃ for 1~1.5h.

4. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 3, characterized in that: The dry ball milling process is as follows: 20μm silicon carbide particles and high cohesive silicone resin powder are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 200-300 r / min, the ball milling is carried out for 2-4 hours, the ball milling jar rotates in one direction, and stops for 5-10 minutes every 0.5-1 hours of ball milling to obtain mixed powder.

5. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 2, characterized in that: The silicon carbide particles mentioned in step one have a purity of 99.9%, are irregularly shaped, and have an average particle size of 20 μm.

6. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 1, characterized in that: The aluminum powder mentioned in step two has a purity of 99.9%, and the particles are spherical with a particle size of 15-50 μm.

7. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 1, characterized in that: The ball mills mentioned in steps one and two are both planetary ball mills.

8. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 1, characterized in that: The low-energy ball milling process described in step two is as follows: aluminum powder and agglomerated silicon carbide particles are mixed and then loaded into a ball milling jar; the ball milling jar is evacuated and then argon gas is introduced. The ball milling process is dry milling, the ball-to-material ratio is 3-4:1, the ball milling speed is 150-200 r / min, the ball milling is carried out for 2-4 hours, the ball milling jar rotates in one direction, and stops for 5-10 minutes every 0.5-1 hours of ball milling to obtain mixed powder.

9. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum-based composite coating according to claim 1, characterized in that: The mass ratio of aluminum powder to nickel-coated silicon carbide particles in step two is 3:1-2.

10. The cold spraying method for the agglomerated silicon carbide particle-reinforced aluminum matrix composite coating according to claim 1, characterized in that: Step 3, the cold spraying process, is as follows: the substrate is ultrasonically cleaned with anhydrous ethanol for 5-30 minutes, dried, and then sandblasted. After sandblasting, the surface to be sprayed is cleaned with an air gun. The mixed powder obtained in Step 2 is poured into the powder feeder, the substrate is fixed, and cold spraying is performed. Nitrogen is used as the powder feeder. The cold spraying trajectory is S-shaped, the spacing between spraying trajectory lines is 2-3 mm, the spray beam is at 90° to the surface to be sprayed, the gun speed is 150-200 mm / s, the vertical distance between the gun nozzle and the surface to be sprayed is 30-35 mm, the chamber pressure is 3.5-4.5 MPa, the chamber gas temperature is 500-600℃, and the coating is applied several times according to the required coating thickness.

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