Aluminum alloy surface crystallization nanometer composite film layer and preparation method

Abstract

The invention discloses an aluminum alloy surface crystallization nanometer composite film layer and a preparation method, and the preparation method comprises the following steps: preparing a Cr plating layer on the surface of a substrate, and then preparing a CrAlN plating layer on the Cr plating layer to obtain a substrate plated with a CrAlN film layer; and preparing a TiO2 plating layer on the surface of the base body plated with the CrAlN film layer, and forming a nano composite film layer on the surface of the aluminum alloy. Wherein the CrAlN plating layer provides structural support and oxidation resistance, and the crystalline TiO2 plating layer enhances the anti-coking capability and the self-cleaning characteristic of the surface. The multilayer design can significantly improve the overall anti-coking effect and delay the coke deposition rate.

Description

Technical Field

[0001] The invention belongs to the technical field of surface engineering, and specifically relates to a crystalline nano-composite film layer on the surface of an aluminum alloy and a preparation method thereof. Background Art

[0002] Coking mainly occurs when carbon generated by the thermal decomposition of hydrocarbons under high temperature conditions is deposited on the surface of the equipment, gradually forming a hard coking layer. As coking increases, heat conduction is hindered and the heat transfer efficiency of the equipment gradually decreases. In addition, the formation of a coke layer will intensify corrosion, thereby threatening the integrity of the equipment. The basic principle of anti-coking coatings is to prevent carbon deposition by forming a smooth, high temperature and corrosion resistant coating on the surface of the equipment. Generally, anti-coking coatings have low surface energy, high hardness and excellent chemical inertness to reduce the adsorption of hydrocarbons on the surface and prevent their further decomposition and accumulation.

[0003] CrAlN / TiO2 composite coating has significant advantages in the field of anti-coking, mainly in terms of oxidation resistance, high temperature resistance, anti-coking and corrosion resistance. CrAlN material has very good thermal stability, can remain stable at high temperatures exceeding 800°C, and is not easy to decompose. The combination of Cr and Al gives the coating a higher melting point, which is particularly critical for high temperature environments in anti-coking applications. At the same time, the chromium element in CrAlN can form a dense Cr2O3 oxide layer at high temperatures. This oxide film has a good barrier effect, preventing further oxidation, improving the oxidation resistance of the coating, and delaying coke deposition. TiO2 has a low surface energy and can significantly reduce the adsorption of hydrocarbon molecules on the surface, thereby inhibiting the formation of carbon deposition. This low surface energy property helps to reduce the occurrence of coking. The composite structure of CrAlN and TiO2 can be achieved by controlling the thickness and microstructure of the coating. In general, CrAlN provides structural support and oxidation resistance, while TiO2 enhances the surface's anti-coking ability and self-cleaning properties. This multi-layer design can significantly improve the overall anti-coking effect and slow down the coke deposition rate. With the above advantages, CrAlN / TiO2 composite coatings are widely used in petrochemical, cracking units and other high-temperature environments to meet anti-coking needs. Practical applications have shown that this composite coating can not only significantly extend the cleaning cycle of equipment, but also reduce maintenance costs and improve production efficiency. At the same time, its self-cleaning and anti-corrosion properties further reduce equipment downtime and maintenance workload, thereby achieving higher economic benefits.

[0004] At present, this composite coating structure has been put into practice on carbon steel and stainless steel with strong adsorption capacity (such as engine combustion chamber pipes, nozzles, and the inner and outer walls of high-temperature equipment such as industrial furnaces). However, since the adsorption capacity of the aluminum alloy surface is weaker than that of carbon steel and stainless steel, and the formation of the passivation layer on the aluminum alloy surface makes it difficult to form a functional layer with excellent bonding and dense internal structure, it will bring difficulties to the preparation of the coating, so the application on aluminum alloy parts is still blank. However, aluminum alloy parts such as pistons are also very easy to coke during operation, thus affecting the high efficiency of the combustion chamber. Summary of the invention

[0005] In order to overcome the problems in the prior art that aluminum alloys are easily deformed at higher deposition temperatures and the film quality is poor due to the presence of an oxide layer, the purpose of the present invention is to provide a crystalline nano-composite film layer on the surface of an aluminum alloy and a preparation method. The method realizes the preparation of a CrAlN / TiO2 composite coating with an anti-coking function on the surface of an aluminum alloy part. The composite coating is not easy to deform, thereby extending the cleaning cycle of the equipment, reducing maintenance costs, and improving production efficiency, thereby achieving higher economic benefits.

[0006] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0008] A Cr coating is prepared on the surface of the substrate, and then a CrAlN coating is prepared on the Cr coating to obtain a substrate coated with a CrAlN film layer;

[0009] A TiO2 coating is prepared on the surface of a substrate coated with a CrAlN film layer, and a nano-composite film layer is formed on the surface of the aluminum alloy.

[0010] Further, the substrate is an aluminum alloy substrate;

[0011] Before preparing the Cr coating on the substrate surface, the substrate is roughened.

[0012] Furthermore, the Cr coating is prepared by a multi-arc ion plating method.

[0013] Furthermore, the preparation process parameters of the Cr coating include: Cr target arc current of 80-120A, bias voltage of 80-120V, deposition temperature of room temperature to 100°C, and Cr coating thickness of 0.1-0.5μm.

[0014] Furthermore, the preparation process parameters of the CrAlN coating include: CrAl alloy target arc current of 80-120A, bias voltage of 80-120V, nitrogen flow rate of 300-600sccm, and deposition temperature of room temperature to 100°C.

[0015] Furthermore, the atomic percentage of Al in the CrAl alloy target is 25 to 50%.

[0016] Furthermore, the TiO2 coating is prepared by atomic layer deposition.

[0017] Furthermore, the preparation process parameters of the TiO2 coating include: nitrogen is used as the purge gas in a single cycle during the atomic layer deposition process, and the passage time of the titanium source precursor, nitrogen, oxygen source, and nitrogen are 1-2s, 25-35s, 0.2-0.4s, and 75-85s respectively; the total number of cycles is 1500-2500 times, and the thickness of the TiO2 coating is 0.1-0.3μm.

[0018] A nanocomposite film layer prepared according to any one of claims 1 to 8, comprising a Cr coating, a CrAlN coating and a TiO2 coating arranged on a substrate from bottom to top.

[0019] Furthermore, the nanocomposite coating was subjected to an anti-coking test at 600-800° C., and the coking adhesion area was 8.707%.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] 1) The present invention realizes the preparation of composite coatings at relatively low temperatures. By appropriately increasing the bias voltage from 40-70V to 100V and the target arc current from 60-90A to 100A, the deposition temperature is reduced from 350-400°C to 100°C without affecting the coating preparation speed, which is conducive to improving the uniformity of the surface coating, thereby optimizing the surface quality of the coating, reducing residual stress, and improving the anti-coking performance of the coating. At the same time, excessively high temperature will cause deformation of the aluminum alloy substrate, which may weaken the bonding force between the composite coating and the substrate or even cause peeling, which can fill the gap in the anti-coking film layer of aluminum alloy parts in the engine combustion chamber.

[0022] 2) The present invention realizes the preparation of anatase crystalline TiO2 coating. The benefit of film crystallization is that the crystalline film structure is denser and can better achieve the purpose of anti-coking.

[0023] 3) CrAlN / TiO2 composite coating has significant advantages in the hot end parts of the engine combustion chamber, mainly in terms of anti-coking. CrAlN provides structural support and oxidation resistance, while TiO2 enhances the surface's anti-coking ability and self-cleaning properties. This multi-layer design can significantly improve the overall anti-coking effect and slow down the coke deposition rate. This composite coating can not only significantly extend the cleaning cycle of the equipment, but also reduce maintenance costs and improve production efficiency. At the same time, its self-cleaning and anti-corrosion properties further reduce equipment downtime and maintenance workload, thereby achieving higher economic benefits.

[0024] Furthermore, through roughening, the passivation layer is broken and the surface area of ​​the film layer is increased, so that the film layer can adhere better and the interlayer bonding force between the coating and the substrate is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0026] Figure 1 It is a schematic diagram of piston components;

[0027] Figure 2 is a schematic diagram of the composite coating structure;

[0028] Figure 3 is the SEM photo of the composite coating;

[0029] Figure 4 XRD results of TiO2 coating;

[0030] Figure 5 These are the test results of anti-coking performance, where (a) is the original state of the metal substrate surface; (b) is the coked state of the metal substrate surface; (c) is the original state of the composite coating surface; and (d) is the coked state of the composite coating surface. DETAILED DESCRIPTION

[0031] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly and comprehensively understood.

[0032] The aluminum alloy substrate in the present invention is a cast aluminum piston component, and the cast aluminum piston component and an aluminum sheet are taken as examples for description.

[0033] The method for preparing the crystalline nanocomposite film layer on the surface of an aluminum alloy of the present invention comprises the following steps:

[0034] A Cr coating is prepared on the surface of an aluminum alloy substrate by a multi-arc ion plating method as a base layer, and then a CrAlN coating is prepared to obtain a substrate coated with a CrAlN film layer.

[0035] The obtained substrate coated with the CrAlN film layer was ultrasonically cleaned and blown clean with N2, and finally placed in an oven for drying;

[0036] An atomic layer deposition method is used to prepare a TiO2 coating with anti-coking function on the surface of a dried CrAlN film-coated substrate, and a nano-composite film layer is formed on the surface of the aluminum alloy.

[0037] The specific steps are as follows: (1) grinding, polishing, cleaning and drying the surface of the cast aluminum piston component, grinding and polishing the cast aluminum piston component, ultrasonically cleaning the cast aluminum piston component with alcohol after the grinding and polishing process, and then drying it in an oven at 80°C to obtain a clean and dry cast aluminum piston component. Then, a multi-arc ion plating process is used to sequentially plate a Cr coating and a CrAlN coating on the piston surface to obtain a cast aluminum piston component plated with a CrAlN composite layer. Among them, the preparation process parameters of the Cr coating include: the Cr target arc current is 80-120A, the bias voltage is 80-120V, the deposition temperature is from room temperature to 100°C, and the Cr coating thickness is 0.1-0.5μm. The preparation process parameters of the CrAlN coating include: the CrAl alloy target arc current is 80-120A, the bias voltage is 80-120V, the nitrogen flow rate is 300-600sccm, and the deposition temperature is from room temperature to 100°C. The atomic percentage of Al in the CrAl alloy target is 25-50%.

[0038] (2) The cast aluminum piston component coated with the CrAlN composite layer is ultrasonically cleaned with alcohol, and then placed in an oven at 80° C. for drying to obtain a clean and dry cast aluminum piston component coated with the CrAlN composite layer.

[0039] (3) A TiO2 coating is prepared on the surface of the cast aluminum piston component coated with the CrAlN composite layer obtained in step (2) using an atomic layer deposition process, thereby obtaining a cast aluminum piston component with a CrAlN / TiO2 composite coating.

[0040] Among them, the preparation process parameters of the TiO2 coating include: nitrogen is used as the purge gas in a single cycle during the atomic layer deposition process, and the passage time of the titanium source precursor, nitrogen, oxygen source, and nitrogen is 1-2s, 25-35s, 0.2-0.4s, and 75-85s respectively; the total number of cycles is 1500-2500 times, and the thickness of the TiO2 coating is 0.1-0.3μm.

[0041] The nanocomposite film layer prepared by the above method includes a Cr coating, a CrAlN coating and a TiO2 coating.

[0042] The nanocomposite coating was subjected to an anti-coking test at 600-800°C, and it was found that the coking adhesion area was reduced from 48.4% of the uncoated layer to 8.707%.

[0043] Example 1

[0044] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0045] (1) Roughening of cast aluminum piston parts: Roughening of cast aluminum piston parts (such as Figure 1As shown, the structure of the cast aluminum piston component includes: a top portion 1, a ring groove portion 2 and a skirt portion 3 which are connected in sequence) are polished with 80 mesh, 200 mesh, 600 mesh, 1000 mesh and 2000 mesh sandpaper in sequence, and then polished with a handheld polisher, and then the polished parts are ultrasonically cleaned with anhydrous ethanol for 20 minutes, and then blown dry with N2, and finally placed in an oven at 80°C for drying for 30 minutes.

[0046] (2) Place the cast aluminum piston component roughened in step (1) into the vacuum chamber of the multi-arc ion plating equipment and evacuate the vacuum chamber to a vacuum degree of less than 8×10 -3 Pa, heated to 100 ° C and kept warm for 30 minutes. Open the inlet valve, fill with 180 sccm of Ar, adjust the bias voltage to 600 V, turn on the ion source for cleaning for 20 minutes, then adjust the bias voltage to 300 V and 100 V, and clean for 10 minutes respectively to clean the surface of the cast aluminum piston component.

[0047] (3) The current of the Cr target was adjusted to 100 A, the bias voltage was adjusted to 100 V, the deposition temperature was adjusted to 100 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 32 min to obtain a Cr coating with a thickness of 0.2 μm.

[0048] (4) The CrAl alloy target arc current was adjusted to 100 A, the bias voltage was adjusted to 100 V, the nitrogen flow rate was adjusted to 300 sccm, the deposition temperature was adjusted to 100 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 80 min to obtain a CrAlN coating with a thickness of 1.2 μm.

[0049] (5) The CrAlN-plated parts were ultrasonically cleaned with anhydrous ethanol for 20 min, then dried with N2, and finally dried in an oven at 80 °C for 30 min.

[0050] (6) The CrAIN-coated parts were transferred to the coating chamber of the atomic layer deposition equipment, evacuated to a chamber pressure of 40 mtorr, and the temperature was raised to 200 °C and kept at this temperature for 30 min. Then, titanium isopropoxide is used as a titanium source precursor (temperature is 60°C), hydrogen peroxide (30% H2O2 aqueous solution by mass) is used as an oxygen source, and high-purity nitrogen (99.999% N2 in purity) is used as a purge gas. The flow rate of high-purity nitrogen is adjusted by a needle valve. The working pressure during high-purity nitrogen purge is 400mtor. In a single cycle of the atomic layer deposition process, the introduction time of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen is 1.5s, 30s, 0.3s, and 80s, respectively, and the total number of cycles is 2500 times, thereby preparing a TiO2 coating with a thickness of 250nm on the surface of the CrA1N-plated component, and forming a final nano-composite film layer on the surface of the above-mentioned cast aluminum piston component.

[0051] The structure of the composite film layer can be found in Figure 2The cast aluminum piston component is coated with Cr, the Cr coating is coated with CrAlN, and the CrAlN coating is coated with TiO2.

[0052] Example 2

[0053] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0054] (1) Roughening of the aluminum sheet: The aluminum sheet (diameter of the aluminum sheet is 25.4 mm, thickness is 1 mm) is polished with 80, 200, 600, 1000, and 2000 grit sandpaper in sequence, and then polished with a handheld polisher. The polished parts are then ultrasonically cleaned with anhydrous ethanol for 20 min, blown dry with N2, and finally dried in an oven at 80°C for 30 min.

[0055] (2) Place the aluminum sheet roughened in step (1) into the vacuum chamber of the multi-arc ion plating equipment and evacuate the vacuum chamber to a vacuum degree of less than 8×10 -3 Pa, heated to 100 °C and kept warm for 30 min. Open the gas inlet valve, fill with 180 sccm of Ar, adjust the bias voltage to 600 V, start the ion source for cleaning for 20 min, then adjust the bias voltage to 300 V and 100 V, respectively for 10 min to clean the surface of the aluminum sheet.

[0056] (3) The current of the Cr target was adjusted to 100 A, the bias voltage was adjusted to 100 V, the deposition temperature was adjusted to 100 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 32 min. The thickness of the Cr coating was adjusted to 0.2 μm.

[0057] (4) The CrAl alloy target arc current was adjusted to 100 A, the bias voltage was 100 V, the nitrogen flow rate was 300 sccm, the deposition temperature was 100 °C, the chamber pressure was 0.7 Pa, the deposition time was 80 min, and the CrAlN coating thickness was 1.2 μm.

[0058] (5) The aluminum sheet coated with CrAlN was ultrasonically cleaned with anhydrous ethanol for 20 min, then dried with N2, and finally dried in an oven at 80°C for 30 min.

[0059] (6) The aluminum sheet coated with CrAlN is transferred to the coating chamber of the atomic layer deposition equipment, and the chamber pressure is evacuated to 40 mtorr, and the temperature is raised to 200°C and kept for 30 minutes. Then, titanium isopropoxide is used as the titanium source precursor (temperature is 60°C), hydrogen peroxide (30% H2O2 aqueous solution by mass fraction) is used as the oxygen source, and high-purity nitrogen (99.999% purity N2) is used as the purge gas. The flow rate of high-purity nitrogen is adjusted by a needle valve. The working pressure during the high-purity nitrogen purge is 400 mtorr. In a single cycle of the atomic layer deposition process, the introduction time of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen is 1.5s, 30s, 0.3s, and 80s respectively, and the total number of cycles is 2500 times, so that a TiO2 coating layer with a thickness of 250nm is prepared on the surface of the substrate coated with CrAlN, and the final nanocomposite film layer is formed on the surface of the above aluminum sheet.

[0060] The structure of the composite film layer can be found in Figure 2 The aluminum sheet substrate is coated with Cr, the Cr coating is coated with CrAlN, and the CrAlN coating is coated with TiO2.

[0061] The SEM photos of the composite film are shown in Figure 3 As shown, it can be seen that the coating is divided into three layers, from top to bottom, TiO2 coating, CrAlN coating and Cr coating, among which the thickness of TiO2 coating and Cr coating is about 0.2μm, the thickness of CrAlN coating is about 1.2μm, the total thickness of coating is about 1.6μm, the coating is uniform and continuous, the interlayer bonding is good, and the internal structure is dense.

[0062] XRD analysis was performed on the phase composition of the film layer, such as Figure 4 As shown, it was found to be anatase phase with a preferred orientation along the 101 crystal plane.

[0063] (7) Anti-coking test: The original aluminum sheet and the aluminum sheet with the nanocomposite film layer in Example 2 were fixed in front of a diesel flame spray gun, the flame spray gun was ignited, and the surface temperature of the sample was controlled to 800°C by adjusting the oxygen intake, and the test was conducted for 30 minutes. After the test, a macroscopic photo of the sample was taken and imported into the image software for binarization processing to obtain the coking adhesion area.

[0064] Figure 5 (a) is the original state of the metal substrate surface; (b) is the coking state of the metal substrate surface; (c) is the original state of the composite coating surface; (d) is the coking state of the composite coating surface. It can be seen that the coking adhesion area of ​​the sample prepared with the composite coating on the surface is reduced from 48.4% to 8.707% compared with the original Al sample, which shows that the present invention plays an important role in the anti-coking function of the aluminum alloy.

[0065] Example 3

[0066] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0067] (1) Roughening of cast aluminum piston parts: The cast aluminum piston parts were polished with 80 mesh, 200 mesh, 600 mesh, 1000 mesh, and 2000 mesh sandpaper in turn, and then polished with a handheld polisher. The polished parts were then ultrasonically cleaned with anhydrous ethanol for 20 minutes, then blown dry with N2, and finally dried in an oven at 80°C for 30 minutes.

[0068] (2) Place the cast aluminum piston component roughened in step (1) into the vacuum chamber of the multi-arc ion plating equipment and evacuate the vacuum chamber to a vacuum degree of less than 8×10 -3 Pa, heated to 100 ° C and kept warm for 30 minutes. Open the inlet valve, fill with 180 sccm of Ar, adjust the bias voltage to 600 V, turn on the ion source for cleaning for 20 minutes, then adjust the bias voltage to 300 V and 100 V, and clean for 10 minutes respectively to clean the surface of the cast aluminum piston component.

[0069] (3) The current of the Cr target was adjusted to 80 A, the bias voltage was adjusted to 120 V, the deposition temperature was adjusted to 100 ° C, and the pressure in the chamber was adjusted to 0.7 Pa. Deposition was carried out for 40 min to obtain a Cr coating with a thickness of 0.3 μm.

[0070] (4) The CrAl alloy target arc current was adjusted to 80 A, the bias voltage was adjusted to 120 V, the nitrogen flow rate was adjusted to 400 sccm, the deposition temperature was adjusted to room temperature, and the pressure in the chamber was adjusted to 0.7 Pa. Deposition was performed for 120 min to obtain a CrAlN coating with a thickness of 1.5 μm.

[0071] (5) The CrAlN-plated parts were ultrasonically cleaned with anhydrous ethanol for 20 min, then dried with N2, and finally dried in an oven at 80 °C for 30 min.

[0072] (6) The CrAlN-plated component is transferred to the coating chamber of the atomic layer deposition equipment, and the chamber pressure is evacuated to 40 mtorr, and the temperature is raised to 200°C and kept for 30 minutes. Then, titanium isopropoxide is used as the titanium source precursor (temperature is 60°C), hydrogen peroxide (30% H2O2 aqueous solution by mass fraction) is used as the oxygen source, and high-purity nitrogen (99.999% purity N2) is used as the purge gas. The flow rate of high-purity nitrogen is adjusted by a needle valve. The working pressure during the high-purity nitrogen purge is 400 mtorr. In a single cycle of the atomic layer deposition process, the introduction time of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen is 1s, 25s, 0.4s, and 85s respectively, and the total number of cycles is 2500 times, so that a TiO2 coating layer with a thickness of 250nm is prepared on the surface of the CrAlN-plated component, and a final nano-composite film layer is formed on the surface of the above-mentioned cast aluminum piston component.

[0073] Example 4

[0074] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0075] (1) Roughening of cast aluminum piston parts: Roughening of cast aluminum piston parts (such as Figure 1 As shown in the figure, the structure of the cast aluminum piston component includes: the top, the ring groove and the skirt) are polished with 80 mesh, 200 mesh, 600 mesh, 1000 mesh and 2000 mesh sandpaper in sequence, and then polished with a handheld polisher, and then the polished parts are ultrasonically cleaned with anhydrous ethanol for 20 minutes, and then blown dry with N2, and finally placed in an oven at 80°C for 30 minutes.

[0076] (2) Place the cast aluminum piston component roughened in step (1) into the vacuum chamber of the multi-arc ion plating equipment and evacuate the vacuum chamber to a vacuum degree of less than 8×10 -3 Pa, heated to 100 ° C and kept warm for 30 minutes. Open the inlet valve, fill with 180 sccm of Ar, adjust the bias voltage to 600 V, turn on the ion source for cleaning for 20 minutes, then adjust the bias voltage to 300 V and 100 V, and clean for 10 minutes respectively to clean the surface of the cast aluminum piston component.

[0077] (3) The current of the Cr target was adjusted to 120 A, the bias voltage was adjusted to 100 V, the deposition temperature was adjusted to 100 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 60 min to obtain a Cr coating with a thickness of 0.5 μm.

[0078] (4) The CrAl alloy target arc current was adjusted to 120 A, the bias voltage was adjusted to 100 V, the nitrogen flow rate was adjusted to 500 sccm, the deposition temperature was adjusted to 50 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 80 min to obtain a CrAlN coating with a thickness of 1.2 μm.

[0079] (5) The CrAlN-plated parts were ultrasonically cleaned with anhydrous ethanol for 20 min, then dried with N2, and finally dried in an oven at 80 °C for 30 min.

[0080] (6) The CrAlN-plated component is transferred to the coating chamber of the atomic layer deposition equipment, and the chamber pressure is evacuated to 40 mtorr, and the temperature is raised to 200°C and kept for 30 minutes. Then, titanium isopropoxide is used as the titanium source precursor (temperature is 60°C), hydrogen peroxide (30% H2O2 aqueous solution by mass fraction) is used as the oxygen source, and high-purity nitrogen (99.999% purity N2) is used as the purge gas. The flow rate of high-purity nitrogen is adjusted by a needle valve. The working pressure during the high-purity nitrogen purge is 400 mtorr. In a single cycle of the atomic layer deposition process, the introduction time of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen is 2s, 35s, 0.2s, and 75s respectively, and the total number of cycles is 1500 times, so that a TiO2 coating layer with a thickness of 200nm is prepared on the surface of the CrAlN-plated component, and the final nano-composite film layer is formed on the surface of the above-mentioned cast aluminum piston component.

[0081] Example 5

[0082] A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy comprises the following steps:

[0083] (1) Roughening of cast aluminum piston parts: Roughening of cast aluminum piston parts (such as Figure 1 As shown in the figure, the structure of the cast aluminum piston component includes: the top, the ring groove and the skirt) are polished with 80 mesh, 200 mesh, 600 mesh, 1000 mesh and 2000 mesh sandpaper in sequence, and then polished with a handheld polisher, and then the polished parts are ultrasonically cleaned with anhydrous ethanol for 20 minutes, and then blown dry with N2, and finally placed in an oven at 80°C for 30 minutes.

[0084] (2) Place the cast aluminum piston component roughened in step (1) into the vacuum chamber of the multi-arc ion plating equipment and evacuate the vacuum chamber to a vacuum degree of less than 8×10 -3 Pa, heated to 100 ° C and kept warm for 30 minutes. Open the inlet valve, fill with 180 sccm of Ar, adjust the bias voltage to 600 V, turn on the ion source for cleaning for 20 minutes, then adjust the bias voltage to 300 V and 100 V, and clean for 10 minutes respectively to clean the surface of the cast aluminum piston component.

[0085] (3) The current of the Cr target was adjusted to 110 A, the bias voltage was adjusted to 80 V, the deposition temperature was adjusted to 100 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 16 min to obtain a Cr coating with a thickness of 0.1 μm.

[0086] (4) The CrAl alloy target arc current was adjusted to 90 A, the bias voltage was adjusted to 80 V, the nitrogen flow rate was adjusted to 600 sccm, the deposition temperature was adjusted to 70 °C, the pressure in the chamber was adjusted to 0.7 Pa, and the deposition time was adjusted to 80 min to obtain a CrAlN coating with a thickness of 1.2 μm.

[0087] (5) The CrAlN-plated parts were ultrasonically cleaned with anhydrous ethanol for 20 min, then dried with N2, and finally dried in an oven at 80 °C for 30 min.

[0088] (6) The CrAIN-coated parts were transferred to the coating chamber of the atomic layer deposition equipment, evacuated to a chamber pressure of 40 mtorr, and the temperature was raised to 200 °C and kept at this temperature for 30 min. Then, titanium isopropoxide is used as a titanium source precursor (temperature is 60°C), hydrogen peroxide (30% H2O2 aqueous solution by mass) is used as an oxygen source, and high-purity nitrogen (99.999% purity N2) is used as a purge gas. The flow rate of high-purity nitrogen is adjusted by a needle valve. The working pressure during high-purity nitrogen purge is 400mtor. In a single cycle of the atomic layer deposition process, the introduction time of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen is 1.5s, 30s, 0.3s, and 80s, respectively, and the total number of cycles is 3000 times, thereby preparing a TiO2 coating with a thickness of 300nm on the surface of the CrA1N-plated component, and forming a final nano-composite film layer on the surface of the above-mentioned cast aluminum piston component.

[0089] Compared with the patent: CN113584440B (high temperature resistant and anti-coking chromium aluminum nitrogen, titanium dioxide composite coating and its preparation method), the composite coating is prepared at a lower temperature. By appropriately increasing the bias voltage from 40-70V to 100V and the target arc current from 60-90A to 100A, the deposition temperature is reduced from 350-400℃ to 100℃ without affecting the coating preparation speed, which is conducive to improving the uniformity of the surface coating, thereby optimizing the surface quality of the coating, reducing residual stress, and improving the anti-coking performance of the coating. At the same time, too high a temperature will cause the aluminum alloy substrate to deform, which may weaken the bonding force between the composite coating and the substrate or even cause peeling.

[0090] Compared with patent: CN113584440B (high temperature resistant and anti-coking chromium aluminum nitrogen, titanium dioxide composite coating and preparation method thereof), the preparation of anatase crystalline TiO2 coating is achieved. The benefit of film crystallization is that the crystalline film structure is denser, which can better achieve the purpose of anti-coking.

[0091] The above description is only for the best embodiment of the present invention, but it should not be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. However, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

[0092] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more related listed items.

Claims

1. A method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy, characterized in that: The steps include: A Cr coating is prepared on the surface of the substrate, and then a CrAlN coating is prepared on the Cr coating to obtain a substrate coated with a CrAlN film layer; A TiO2 coating is prepared on the surface of a substrate coated with a CrAlN film layer, and a nano-composite film layer is formed on the surface of the aluminum alloy.

2. The method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The substrate is an aluminum alloy substrate; Before preparing the Cr coating on the substrate surface, the substrate is roughened.

3. The method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The Cr coating was prepared by multi-arc ion plating.

4. The method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The preparation process parameters of the Cr coating include: Cr target arc current of 80-120A, bias voltage of 80-120V, deposition temperature of room temperature to 100°C, and Cr coating thickness of 0.1-0.5μm.

5. The method for preparing a crystalline nano-composite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The preparation process parameters of the CrAlN coating include: CrAl alloy target arc current of 80-120A, bias voltage of 80-120V, nitrogen flow rate of 300-600sccm, and deposition temperature of room temperature to 100°C.

6. The method for preparing a crystalline nanocomposite film layer on the surface of an aluminum alloy according to claim 4, characterized in that: The atomic percentage of Al in the CrAl alloy target is 25 to 50%.

7. The method for preparing a crystalline nano-composite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The TiO2 coating was prepared by atomic layer deposition.

8. The method for preparing a crystalline nano-composite film layer on the surface of an aluminum alloy according to claim 1, characterized in that: The preparation process parameters of the TiO2 coating include: nitrogen is used as the purge gas in a single cycle during the atomic layer deposition process, and the passage time of the titanium source precursor, nitrogen, oxygen source, and nitrogen are 1-2s, 25-35s, 0.2-0.4s, and 75-85s respectively; the total number of cycles is 1500-2500 times, and the thickness of the TiO2 coating is 0.1-0.3μm.

9. A nanocomposite film layer prepared according to any one of claims 1 to 8, characterized in that: It includes a Cr coating, a CrAlN coating and a TiO2 coating on the substrate from bottom to top.

10. The nanocomposite film layer according to claim 9, characterized in that: The nano composite coating is subjected to an anti-coking test at 600-800° C., and the coking adhesion area is 8.707%.

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