Cold spraying preparation method of corrosion-resistant tough dual-scale titanium nitride reinforced aluminum-based composite coating on surface of magnesium alloy

Abstract

The invention discloses a cold spraying preparation method of a corrosion-resistant tough dual-scale titanium nitride reinforced aluminum-based composite coating on the surface of a magnesium alloy, and relates to a cold spraying preparation method of an aluminum-based composite coating on the surface of the magnesium alloy. In order to solve the problems that an existing pure aluminum coating is poor in cold spraying wear resistance, compactness and hardness, nano-particles serve as a reinforcing phase to be attached to micron-sized core particles through a ball milling method, the nanometer characteristic is brought into the coating by means of the good deposition performance of micron particles, then a micron-sized reinforcing phase is mixed, and the coating is prepared. And the critical speed of spraying is increased, so that the coating is more compact. According to the method, through an optimized powder pretreatment process, the defects that nanoparticles are low in cold spraying deposition efficiency, prone to agglomeration and the like are overcome, and the problem that a micron particle reinforced phase is prone to generating pores in a coating is solved. The composite coating which is compact in bonding structure and remarkably improved in hardness, wear resistance and corrosion resistance is successfully prepared on the magnesium alloy.

Description

Technical Field

[0001] This invention relates to a cold spraying method for preparing an aluminum-based composite coating on a magnesium alloy surface. Background Technology

[0002] Magnesium alloys, such as AZ31B, have broad application prospects in aerospace, automotive, and 3C product fields due to their extremely low density, high specific strength, and specific stiffness. However, the inherent disadvantages of magnesium alloys, such as poor corrosion resistance and poor wear resistance, severely limit their application in moving parts or harsh environments.

[0003] Surface coating technology is an effective means to improve the surface properties and extend the service life of magnesium alloy components. Pure aluminum coatings, with their similar electrochemical potential to magnesium alloys, thus reducing galvanic corrosion, and possessing good plasticity and corrosion resistance, are considered one of the ideal protective coating materials for magnesium alloys. However, pure aluminum coatings themselves have low hardness and cannot provide effective wear protection. Introducing titanium nitride (TiN) ceramic phases is a common method to improve the hardness and wear resistance of aluminum coatings. Among numerous magnesium alloy surface coating preparation technologies, cold spraying technology, with its low-temperature solid-state deposition characteristics, perfectly avoids the drawbacks of traditional thermal spraying technology, such as oxidation and ablation of the magnesium substrate and thermal stress in the coating caused by high temperatures, making it an ideal choice for preparing high-performance protective coatings on magnesium alloy surfaces.

[0004] While cold-sprayed pure aluminum coatings can effectively improve the corrosion resistance of the substrate, their low hardness and limited improvement in wear resistance make them unsuitable for more demanding working conditions. To enhance the wear resistance of aluminum coatings, hard ceramic particles, titanium nitride (TiN), are introduced for composite reinforcement. However, in the past, cold-sprayed coatings using titanium nitride as a reinforcing phase mostly only added micron-sized TiN to improve the coating's strength and abrasion resistance. The addition of micron-sized TiN easily introduces porosity into the coating, affecting its density and resulting in a decrease in corrosion resistance compared to pure aluminum coatings. Adding only nano-sized titanium nitride, however, leads to insufficient kinetic energy during cold spraying due to the small mass of the nanoparticles. The nanoparticles mostly undergo elastic rebound rather than plastic deposition. Furthermore, due to the high specific surface area of ​​nano-sized titanium nitride, agglomeration is likely to occur. Therefore, using nanoparticles as a reinforcement alone fails to leverage the high hardness advantage of nanoparticles. Summary of the Invention

[0005] To address the issues of poor wear resistance, density, and hardness in existing cold-sprayed pure aluminum coatings on magnesium alloy surfaces, this invention proposes a cold-spraying method for preparing a corrosion-resistant and tough dual-scale titanium nitride-reinforced aluminum-based composite coating on magnesium alloy surfaces. This innovative method uses ball milling to mix dual-scale titanium nitride and pure aluminum powders, attaching nanoparticles as a reinforcing phase onto micron-sized core particles. Utilizing the excellent deposition properties of micron-sized particles, the nanoscale characteristics are simultaneously introduced into the coating. The addition of a micron-sized reinforcing phase further increases the critical velocity during spraying, resulting in a denser coating. This method, through optimized powder pretreatment, overcomes the shortcomings of low deposition efficiency and easy agglomeration of nanoparticles in cold spraying, and also solves the problem of porosity in the coating caused by micron-sized reinforcing phases. This invention successfully prepares a composite coating on magnesium alloys with a dense structure and significantly improved hardness, wear resistance, and corrosion resistance by leveraging the low-temperature, high-speed characteristics of cold spraying technology.

[0006] The cold spraying method for preparing a corrosion-resistant and tough dual-scale titanium nitride reinforced aluminum-based composite coating on magnesium alloy surfaces according to the present invention is carried out according to the following steps:

[0007] Step 1: Preparation of dual-scale composite powder:

[0008] First, nano-titanium nitride powder and micron-sized spherical aluminum powder are mixed and ball-milled at high energy to embed the nano-titanium nitride on the surface of the plastic micron-sized spherical aluminum powder, thereby achieving uniform dispersion of the nano-titanium nitride powder and obtaining nano-TiN-micron Al composite powder; then, nano-TiN-micron Al composite powder and micron-sized titanium nitride powder are mixed and ball-milled at low energy to obtain a dual-scale composite powder for cold spraying.

[0009] The total mass ratio of the nano-titanium nitride powder and the micron-sized titanium nitride powder to the micron-sized spherical aluminum powder is 1:(8-12); the mass ratio of the nano-titanium nitride powder to the micron-sized titanium nitride powder is 1:(1-5).

[0010] The high-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is (6-10):1. The ball mill speed is 200-300 r / min, the ball milling time is 1-3 h, and the ball mill stops rotating for 3 min after every 10-15 min of ball milling.

[0011] The low-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is (2-4):1. The ball mill speed is 100-200 r / min, the ball milling time is 0.5-1 h, and the ball mill stops rotating for 3 min after every 10-15 min of ball milling.

[0012] Step 2, Matrix Pretreatment:

[0013] The surface of the magnesium alloy substrate is cleaned, roughened, and dried.

[0014] Step 3: Cold spraying to deposit the coating:

[0015] The dual-scale composite powder prepared in step one is loaded into the powder feeder of the cold spraying equipment and cold sprayed onto the surface of the magnesium alloy substrate.

[0016] The cold spraying process is as follows: nitrogen is used as the spraying gas, the temperature of the spraying gas is 450-650℃, the pressure of the spraying gas is 3.5-4.5MPa, the moving speed of the spray gun is 100-200mm / s, the spraying trajectory is "S" shaped, the line spacing of the spraying trajectory is 1-2mm, the spraying distance is 30mm, the powder feeder speed is 0.5-3r / min, and the number of spraying layers is 2-3.

[0017] The principle and beneficial effects of this invention are as follows:

[0018] 1. This invention fundamentally solves the problem of thermal damage in the surface strengthening treatment of magnesium alloys. The invention employs a pure cold spraying technology, with the process temperature consistently far below the melting points of aluminum, magnesium, and their alloys. This low-temperature characteristic completely avoids the risks of grain coarsening, phase transformation softening, severe oxidation, and even combustion caused by high-temperature molten droplets on the magnesium alloy matrix in traditional thermal spraying techniques. Simultaneously, the cold spraying process involves no significant heat input, preventing workpiece deformation and maintaining the dimensional integrity and mechanical properties of precision magnesium alloy components. This provides a safe and reliable technical path for the surface strengthening of magnesium alloys and other reactive metals.

[0019] 2. This invention creatively employs a stepwise composite powder design strategy. First, the mechanical force of high-energy ball milling firmly anchors the easily agglomerated nano-TiN particles onto the surface of micron-sized aluminum powder with excellent plasticity, constructing a nanocomposite unit with aluminum as the carrier. This elevates the dispersion problem of nanomaterials from the difficult-to-control powder mixing level to the easily achievable micron-sized unit construction level, thereby fundamentally ensuring a highly uniform distribution of the nano-reinforcing phase in subsequent processes and the final coating.

[0020] 3. This invention achieves cross-scale synergistic strengthening of titanium nitride ceramic reinforcing phases at both the micron and nanoscales. In the coating, micron-sized TiN and nano-sized TiN play different roles and exert a synergistic effect. Micron-sized TiN, as the macroscopic framework, mainly bears the load and resists wear, forming the basis for the coating's high wear resistance. Simultaneously, due to its larger size and mass, it can provide a higher critical velocity for the spraying gas during cold spray deposition. Nano-sized TiN is uniformly dispersed in the aluminum matrix, hindering dislocation movement and grain boundary slip through a strong pinning effect, resulting in significant dispersion strengthening and grain refinement strengthening effects, greatly improving the strength and hardness of the matrix itself. This cross-scale synergistic mechanism of "micron bearing the load, nano-strengthening" allows the coating to maintain good toughness and bonding strength while improving hardness and wear resistance, and simultaneously enhancing the coating's corrosion resistance. Attached Figure Description

[0021] Figure 1 SEM (200x) and EDS images of the surface of nano-TiN-micron Al composite powder in step one of Example 1;

[0022] Figure 2 SEM (2000x) and EDS images of the surface of nano-TiN-micron Al composite powder in step one of Example 1;

[0023] Figure 3 The images show SEM and EDS images of the surface of the dual-scale composite powder obtained in step one of Example 1.

[0024] Figure 4 SEM image (200x magnification) of the coating obtained on the surface of the magnesium alloy substrate in step three of Example 1.

[0025] Figure 5 The image shows the SEM (1000x) and EDS images of the coating obtained on the surface of the magnesium alloy substrate in step three of Example 1.

[0026] Figure 6 The image shows the SEM image (20,000x magnification) and EDS image of the coating obtained on the surface of the magnesium alloy substrate in step three of Example 1.

[0027] Figure 7 Tafel polarization curves of AZ31B Mg substrate, pure aluminum coating, and dual-scale TiN-reinforced pure aluminum coating (Al-micro / nano TiN coating) in the electrochemical corrosion test of Example 1 are shown.

[0028] Figure 8 The image shows a Vickers hardness histogram of the AZ31B Mg matrix, pure aluminum coating, and dual-scale TiN-reinforced pure aluminum coating in Example 1. Detailed Implementation

[0029] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any reasonable combination of the specific embodiments.

[0030] Specific Implementation Method 1: The cold spraying method for preparing a corrosion-resistant and tough dual-scale titanium nitride reinforced aluminum-based composite coating on magnesium alloy surfaces in this implementation method is carried out according to the following steps:

[0031] Step 1: Preparation of dual-scale composite powder:

[0032] First, nano-titanium nitride powder and micron-sized spherical aluminum powder are mixed and ball-milled at high energy to embed the nano-titanium nitride on the surface of the plastic micron-sized spherical aluminum powder, thereby achieving uniform dispersion of the nano-titanium nitride powder and obtaining nano-TiN-micron Al composite powder; then, nano-TiN-micron Al composite powder and micron-sized titanium nitride powder are mixed and ball-milled at low energy to obtain a dual-scale composite powder for cold spraying.

[0033] The total mass ratio of the nano-titanium nitride powder and the micron-sized titanium nitride powder to the micron-sized spherical aluminum powder is 1:(8-12); the mass ratio of the nano-titanium nitride powder to the micron-sized titanium nitride powder is 1:(1-5).

[0034] The high-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is (6-10):1. The ball mill speed is 200-300 r / min, the ball milling time is 1-3 h, and the ball mill stops rotating for 3 min after every 10-15 min of ball milling.

[0035] The low-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is (2-4):1. The ball mill speed is 100-200 r / min, the ball milling time is 0.5-1 h, and the ball mill stops rotating for 3 min after every 10-15 min of ball milling.

[0036] Step 2, Matrix Pretreatment:

[0037] The surface of the magnesium alloy substrate is cleaned, roughened, and dried.

[0038] Step 3: Cold spraying to deposit the coating:

[0039] The dual-scale composite powder prepared in step one is loaded into the powder feeder of the cold spraying equipment and cold sprayed onto the surface of the magnesium alloy substrate.

[0040] The cold spraying process is as follows: nitrogen is used as the spraying gas, the temperature of the spraying gas is 450-650℃, the pressure of the spraying gas is 3.5-4.5MPa, the moving speed of the spray gun is 100-200mm / s, the spraying trajectory is "S" shaped, the line spacing of the spraying trajectory is 1-2mm, the spraying distance is 30mm, the powder feeder speed is 0.5-3r / min, and the number of spraying layers is 2-3.

[0041] 1. This embodiment fundamentally solves the problem of thermal damage in the surface strengthening treatment of magnesium alloys. This embodiment employs pure cold spraying technology, with the process temperature consistently far below the melting points of aluminum, magnesium, and their alloys. This low-temperature characteristic completely avoids the risks of grain coarsening, phase transformation softening, severe oxidation, and even combustion caused by high-temperature molten droplets on the magnesium alloy matrix in traditional thermal spraying technology. Simultaneously, the cold spraying process involves no significant heat input, preventing workpiece deformation and maintaining the dimensional integrity and mechanical properties of precision magnesium alloy components. This provides a safe and reliable technical path for the surface strengthening of active metals such as magnesium alloys.

[0042] 2. This implementation method creatively adopts a stepwise composite powder design strategy. First, the mechanical force of high-energy ball milling firmly anchors the easily agglomerated nano-TiN particles onto the surface of micron-sized aluminum powder with excellent plasticity, constructing a nanocomposite unit with aluminum as the carrier. This improves the dispersion problem of nanomaterials from the difficult-to-control powder mixing level to the easily achievable micron-sized unit construction level, thereby ensuring the highly uniform distribution of the nano-reinforcing phase in subsequent processes and the final coating from the root.

[0043] 3. This embodiment achieves cross-scale synergistic strengthening of the titanium nitride ceramic reinforcing phase at both the micron and nanoscales. In the coating, micron-sized TiN and nano-sized TiN play different roles and exert a synergistic effect. Micron-sized TiN, as the macroscopic framework, mainly bears the load and resists wear, which is the basis for the high wear resistance of the coating. At the same time, due to its large size and mass, it can withstand a high critical velocity of the spraying gas during cold spray deposition. Nano-sized TiN is uniformly dispersed in the aluminum matrix, hindering dislocation movement and grain boundary slip through a strong pinning effect, resulting in significant dispersion strengthening and grain refinement strengthening effects, which greatly improves the strength and hardness of the matrix itself. This cross-scale synergistic mechanism of "micron bearing the load and nano-strengthening" enables the coating to improve hardness and wear resistance while maintaining good toughness and bonding strength, and at the same time improves the corrosion resistance of the coating.

[0044] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the purity of the micron-sized spherical aluminum powder mentioned in step one is 99.9%, and the average particle size is 30-45μm.

[0045] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the purity of the nano-titanium nitride powder mentioned in step 1 is 99.9%, and the average particle size is 400-600nm.

[0046] Specific Implementation Method Four: This implementation method differs from one of the specific implementation methods one to three in that the purity of the micron-sized titanium nitride powder mentioned in step one is 99.9%, and the average particle size is 35-55μm.

[0047] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the grinding balls used in the high-energy ball milling in step 1 are made of zirconium oxide, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, and the mass ratio of the grinding balls with a diameter of 8 mm to the grinding balls with a diameter of 4 mm is 1:(7-10).

[0048] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that the grinding balls used in the low-energy ball milling in step one are made of zirconium oxide, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, and the mass ratio of the grinding balls with a diameter of 8 mm to the grinding balls with a diameter of 4 mm is 1:(3-5).

[0049] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the cleaning process described in step two uses anhydrous ethanol for ultrasonic treatment to remove oil stains; the ultrasonic treatment time is 10 minutes, and the ultrasonic frequency is 20-80KHz.

[0050] Specific Implementation Method Eight: This implementation method differs from one of Specific Implementation Methods One to Seven in that: the roughening treatment described in step two uses 24-mesh alumina for sandblasting to activate the surface and improve its roughness, followed by ultrasonic treatment with anhydrous ethanol.

[0051] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that the magnesium alloy matrix described in step two is AZ31B Mg.

[0052] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that: the cold spraying process described in step 3 uses nitrogen as the spraying gas, the temperature of the spraying gas is 550℃, the pressure of the spraying gas is 4.5MPa, the moving speed of the spray gun is 160mm / s, the spraying trajectory is "S" shaped, the line spacing of the spraying trajectory is 2mm, the spraying distance is 30mm, the powder feeder speed is 1r / min, and the number of spraying layers is 2.

[0053] Example 1

[0054] The cold spraying method for preparing a corrosion-resistant and tough dual-scale titanium nitride reinforced aluminum-based composite coating on magnesium alloy surfaces in this embodiment is carried out according to the following steps:

[0055] Step 1: Preparation of dual-scale composite powder:

[0056] First, nano-titanium nitride powder and micron-sized spherical aluminum powder are mixed and ball-milled at high energy to embed the nano-titanium nitride on the surface of the plastic micron-sized spherical aluminum powder, thereby achieving uniform dispersion of the nano-titanium nitride powder and obtaining nano-TiN-micron Al composite powder; then, nano-TiN-micron Al composite powder and micron-sized titanium nitride powder are mixed and ball-milled at low energy to obtain a dual-scale composite powder for cold spraying.

[0057] The total mass ratio of the nano-titanium nitride powder and the micron-sized titanium nitride powder to the micron-sized spherical aluminum powder is 1:9; the mass ratio of the nano-titanium nitride powder to the micron-sized titanium nitride powder is 1:3.

[0058] The purity of the micron-sized spherical aluminum powder is 99.9%, and the average particle size is 40 μm.

[0059] The purity of the nano-titanium nitride powder is 99.9%, and the average particle size is 500 nm.

[0060] The purity of the micron-sized titanium nitride powder is 99.9%, and the average particle size is 45 μm.

[0061] The high-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is 8:1, the ball mill speed is 200 r / min, the ball milling time is 1.5 h, and the ball mill stops rotating for 3 min after every 15 min of ball milling.

[0062] The low-energy ball milling process is as follows: a planetary ball mill is used, the ball milling jar is evacuated, and then an inert gas, namely argon, is introduced. The ball-to-material mass ratio is 3:1, the ball mill speed is 200 r / min, the ball milling time is 1 h, and the ball mill stops rotating for 3 min after every 15 min of ball milling.

[0063] The high-energy ball mill uses zirconium oxide grinding balls, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, with a mass ratio of 1:9 between the grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm.

[0064] The low-energy ball mill uses zirconium oxide grinding balls, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, with a mass ratio of 1:4 between the grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm.

[0065] Step 2, Matrix Pretreatment:

[0066] The surface of the magnesium alloy substrate is cleaned, roughened, and dried.

[0067] The cleaning process uses anhydrous ethanol for ultrasonic treatment to remove oil stains; the ultrasonic treatment time is 10 minutes and the ultrasonic frequency is 60KHz.

[0068] The roughening treatment involves sandblasting with 24-mesh alumina to activate the surface and improve its roughness, followed by ultrasonic treatment with anhydrous ethanol.

[0069] The magnesium alloy matrix is ​​AZ31B Mg;

[0070] Step 3: Cold spraying to deposit the coating:

[0071] The dual-scale composite powder prepared in step one is loaded into the powder feeder of the cold spraying equipment and cold sprayed onto the surface of the magnesium alloy substrate.

[0072] The cold spraying process is as follows: nitrogen is used as the spraying gas, the temperature of the spraying gas is 550℃, the pressure of the spraying gas is 4.5MPa, the moving speed of the spray gun is 160 mm / s, the spraying trajectory is "S" shaped, the line spacing of the spraying trajectory is 2mm, the spraying distance is 30mm, the powder feeder speed is 1r / min, and the number of spraying layers is 2.

[0073] Comparative Example 1

[0074] Step 1: Select pure aluminum powder with an average particle size of 40 μm and a spherical microstructure, and place it into the powder feeder;

[0075] Step 2: The AZ31B Mg magnesium alloy substrate is ultrasonically cleaned in ethanol at a frequency of 60Hz. Then, alumina is used to sandblast the surface to remove surface oil, increase surface roughness, and activate the surface.

[0076] Step 3: Deposition is performed on the magnesium alloy substrate using a cold spray system. Nitrogen gas is used as the spraying gas, with a temperature of 550℃ and a pressure of 4.5MPa. The spray gun moving speed is 160 mm / s, the spray trajectory is "S" shaped, the line spacing of the spray trajectory is 2mm, the spraying distance is 30mm, the powder feeder speed is 1r / min, and the number of sprayed layers is 2.

[0077] Figure 1 SEM (200x) and EDS images of the surface of nano-TiN-micron Al composite powder in step one of Example 1; Figure 2 SEM (2000x) and EDS images of the surface of nano-TiN-micron Al composite powder in step one of Example 1; Figure 3 The images show the SEM and EDS images of the surface of the dual-scale composite powder obtained in step one of Example 1; as shown. Figure 1As shown, through high-energy ball milling, nano-sized TiN is fully dispersed in Al powder. Nano-sized TiN particles can be seen embedded on the surface of micron-sized pure aluminum particles. By adjusting the ball milling speed and time, the microstructure of the pure aluminum powder is maintained in a spherical state with optimal flowability. A single particle of the composite powder is selected for imaging. Figure 2 The EDS image shows that nano-TiN particles are uniformly embedded on the surface of pure aluminum particles. Figure 3 It can be seen that after the "nano-TiN-micron Al" composite powder and micron TiN powder are mixed, most of the pure aluminum particles remain spherical, and the micron-sized TiN is uniformly mixed into the composite powder. Some nano TiN particles fall off from the Al particles, but most of them still remain embedded on the surface of the pure aluminum particles. Figure 4-6 SEM and EDS images of cross-sections at different magnifications show that the cross-section of the dual-scale TiN-reinforced pure aluminum coating mainly consists of plastically deformed pure aluminum particles, micron-sized TiN, and nano-sized TiN. Nano-sized TiN coats the pure aluminum particles, resulting in clear boundaries between the composite coating particles. Importantly, the nano-sized TiN particles retain their irregular original morphology. During spraying, the Al particles deform, and the surface-coated nano-sized TiN embeds into the edges of the Al particles, creating a mechanical bond and a pinning effect, thus promoting a denser coating. Meanwhile, micron-sized TiN, due to its larger size and mass, generates a higher critical velocity of the spraying gas during deposition, resulting in a tight bond between the substrate and the coating interface.

[0078] Figure 7 Tafel polarization curves of AZ31B Mg substrate, pure aluminum coating, and dual-scale TiN-reinforced pure aluminum coating (Al-micro / nano TiN coating) in the electrochemical corrosion test of Example 1 are shown. Figure 8 This is a Vickers hardness histogram of the AZ31B Mg matrix, pure aluminum coating, and dual-scale TiN-reinforced pure aluminum coating in Example 1. Comparative Example 1 shows a pure aluminum coating thickness of approximately 600 μm and an average hardness of 26.76 HV. 0.5 Compared to the substrate, the self-corrosion potential shifts positively by 570 mV; the thickness of the dual-scale TiN-reinforced pure aluminum coating (Al-micro / nano TiN coating) obtained in Example 1 is 400 μm, and the average hardness is 47.82 HV. 0.5 Compared to the substrate, the self-corrosion potential shifts positively by 788mV.

Claims

1. A cold spraying method for preparing a corrosion-resistant and tough dual-scale titanium nitride reinforced aluminum-based composite coating on a magnesium alloy surface, characterized in that: The cold spraying method for preparing the corrosion-resistant and strong dual-scale titanium nitride reinforced aluminum-based composite coating on the surface of magnesium alloy is performed according to the following steps: Step one, preparation of dual-scale composite powder: First, the nano titanium nitride powder is mixed with the micron spherical aluminum powder for high-energy ball milling, so that the nano titanium nitride is embedded on the surface of the plastic micron spherical aluminum powder, the nano titanium nitride powder is uniformly dispersed, and a nano TiN-micron Al composite powder is obtained; then the nano TiN-micron Al composite powder is mixed with the micron titanium nitride powder for low-energy ball milling, and a dual-scale composite powder for cold spraying is obtained; The mass ratio of the total mass of the nano titanium nitride powder and the micron titanium nitride powder to the mass of the micron spherical aluminum powder is 1:(8-12); the mass ratio of the nano titanium nitride powder to the micron titanium nitride powder is 1:(1-5); The high-energy ball milling process is as follows: a planetary ball mill is used, the ball mill tank is subjected to vacuum treatment, then inert gas is introduced, the inert gas is argon, the ball-to-material mass ratio is (6-10):1, the rotation speed of the ball mill is 200-300 r / min, and the ball milling time is 1-3 h, during which the ball mill is stopped rotating for 3 min every 10-15 min of ball milling; The low-energy ball milling process is as follows: a planetary ball mill is used, the ball mill tank is subjected to vacuum treatment, then inert gas is introduced, the inert gas is argon, the ball-to-material mass ratio is (2-4):1, the rotation speed of the ball mill is 100-200 r / min, and the ball milling time is 0.5-1 h, during which the ball mill is stopped rotating for 3 min every 10-15 min of ball milling; Step two, substrate pretreatment: The magnesium alloy substrate surface is subjected to cleaning treatment, roughening treatment, and drying; Step three, cold spraying deposition of the coating: The dual-scale composite powder prepared in step one is loaded into the powder feeder of the cold spraying equipment, and cold spraying is performed on the magnesium alloy substrate surface; The cold spraying process is as follows: nitrogen is used as the spraying gas, the temperature of the spraying gas is 450-650℃, the pressure of the spraying gas is 3.5-4.5 MPa, the moving speed of the spraying gun is 100-200 mm / s, the spraying trajectory is "S" shape, the row spacing of the spraying trajectory is 1-2 mm, the spraying distance is 30 mm, the rotation speed of the powder feeder is 0.5-3 r / min, and the number of spraying layers is 2-3.

2. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced aluminum matrix composite coating on the surface of magnesium alloy according to claim 1, characterized in that: The purity of the micron spherical aluminum powder in step one is 99.9%, and the average particle size is 30-45 μm.

3. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The purity of the nano titanium nitride powder in step one is 99.9%, and the average particle size is 400-600 nm.

4. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The purity of the micron titanium nitride powder in step one is 99.9%, and the average particle size is 35-55 μm.

5. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The high-energy ball milling in step one uses zirconium oxide as the grinding ball material, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, and the mass ratio of the grinding balls with a diameter of 8 mm to the grinding balls with a diameter of 4 mm is 1:(7-10).

6. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The low-energy ball milling in step one uses zirconium oxide as the grinding ball material, including grinding balls with a diameter of 8 mm and grinding balls with a diameter of 4 mm, and the mass ratio of the grinding balls with a diameter of 8 mm to the grinding balls with a diameter of 4 mm is 1:(3-5).

7. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The cleaning treatment in step two is ultrasonic treatment with anhydrous ethanol to remove oil stains; the ultrasonic treatment time is 10 min, and the ultrasonic frequency is 20-80 KHz.

8. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The roughening treatment in step two is sand blasting treatment with 24-mesh alumina to activate the surface and increase the surface roughness, and then ultrasonic treatment with anhydrous ethanol.

9. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The magnesium alloy substrate in step two is AZ31B Mg.

10. The cold spraying method for preparing the corrosion resistant and strong-tough dual-scale TiN reinforced Al-matrix composite coating on the surface of the Mg alloy according to claim 1, characterized in that: The process of the cold spraying in step three is as follows: nitrogen is used as the spraying gas, the temperature of the spraying gas is 550 DEG C, the pressure of the spraying gas is 4.5 MPa, the moving speed of the spraying gun is 160 mm / s, the spraying track is "S" shape, the line spacing of the spraying track is 2 mm, the spraying distance is 30 mm, the rotation speed of the powder feeder is 1 r / min, and the spraying layer number is 2.

Images