Curved surface type inner surface heterogeneous hierarchical coating and preparation method thereof

Abstract

The invention discloses a curved surface type inner surface heterogeneous hierarchical coating and a preparation method thereof, and the preparation method comprises the following steps: preparing a first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating and a second Cr coating on the surface of a matrix layer by layer to obtain a CrAlN composite transition layer; and preparing a TiO2 coating on the surface of the substrate plated with the Cr / Al / N composite transition layer. The CrAlN composite transition layer is introduced between the substrate and the surface coating, so that the residual stress is reduced, the composite transition layer has excellent high-temperature impact stripping resistance and coking resistance, the performance of the cylinder sleeve under extreme working conditions is effectively improved, and the service life of the cylinder sleeve under extreme working conditions is effectively prolonged.

Description

Technical Field

[0001] This invention belongs to the fields of materials science and engineering technology, and specifically relates to a heterogeneous layered coating for curved inner surfaces and its preparation method. Background Technology

[0002] Engines are widely used in modern automobiles and heavy machinery, favored for their high efficiency and durability. However, with the continuous increase in engine power and operating temperature, the material properties of cylinder liners face new challenges. Traditional cast iron or aluminum alloy cylinder liners are prone to problems such as coking, sintering, wear, and surface oxidation under high-temperature environments, leading to decreased engine efficiency and shortened lifespan.

[0003] To address the issue of coking in engines and improve the high-temperature resistance of engine cylinder liners, surface coatings can effectively enhance wear resistance, corrosion resistance, and high-temperature performance. Among these, chromium aluminum nitrogen (CrAlN) coatings have become a research hotspot due to their excellent high-temperature oxidation resistance and wear resistance. Titanium dioxide coatings, on the other hand, are renowned for their high hardness and excellent chemical resistance.

[0004] Existing coating technologies for curved cylinder liners mainly focus on the application of single materials, lacking systematic research on composite materials. Composite transition layers of Cr / Al / N with titanium dioxide have potential advantages in high-temperature resistance and anti-sintering ability, but have not yet been effectively applied to engine cylinder liners. Therefore, developing a composite transition layer with excellent high-temperature resistance and anti-sintering properties is of great significance for improving the overall performance of cylinder liners.

[0005] Currently, coating technologies for cylinder liner inner surfaces mainly focus on single-layer modification and simple multi-layer composite transition layers, such as: Publication No. CN 101698363 B, TiN / (TiN+CrN) / CrAlN nanocomposite transition layer and its preparation method; Application No. 202310607253.4, a Cr2AlC / MCrAlY composite transition layer for Ti alloys and TiAl alloys and its preparation method. These technologies have simple physical structures, and their functional characteristics mainly include lubrication (wear resistance), high thermal expansion coefficient to enhance performance under high-temperature cycling (anti-stripping), and basic single-layer anti-sintering coating. However, they are prone to coating peeling under cyclic high-temperature conditions, failing to effectively showcase the advantages of each coating layer and unable to simultaneously ensure high-temperature thermal cycling resistance while preventing coating surface sintering and coking. Summary of the Invention

[0006] The purpose of this invention is to overcome the problem that existing engine coatings cannot simultaneously withstand high-temperature thermal cycling and prevent coating surface sintering and coking, and to provide a curved inner surface heterogeneous layered coating and its preparation method.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A curved inner surface heterogeneous layered coating includes a first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating, a second Cr coating, and a TiO2 coating sequentially disposed on a substrate.

[0009] Furthermore, the thickness of the first Cr coating is 100–300 nm, the thickness of the first CrN coating is 100–500 nm, the thickness of the CrAlN coating is 200–500 nm, the thickness of the second CrN coating is 100–400 nm, the thickness of the second Cr coating is 100–300 nm, and the thickness of the TiO2 coating is 100–300 nm.

[0010] A method for preparing a heterogeneous layered coating on a curved inner surface includes the following steps:

[0011] A first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating, and a second Cr coating were prepared layer by layer on the surface of the substrate to obtain a CrAlN composite transition layer.

[0012] A TiO2 coating was prepared on the surface of a substrate coated with a Cr / Al / N composite transition layer.

[0013] Furthermore, the CrAlN composite transition layer was prepared using a multi-arc ion plating method.

[0014] Furthermore, the TiO2 coating was prepared using an atomic layer deposition method.

[0015] Furthermore, the thickness of the first Cr coating is 100–300 nm, the thickness of the first CrN coating is 100–500 nm, the thickness of the CrAlN coating is 200–500 nm, the thickness of the second CrN coating is 100–400 nm, the thickness of the second Cr coating is 100–300 nm, and the thickness of the TiO2 coating is 100–300 nm.

[0016] Furthermore, the preparation conditions for the first Cr coating and the second Cr coating are as follows: the target material is a Cr target, the arc current is 80-100A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-2Pa, the nitrogen flow rate is 400-800sccm, and the deposition temperature is 200-400℃.

[0017] Furthermore, the preparation conditions for the first CrN coating and the second CrN coating are as follows: the target material is a Cr target, the arc current is 80-100A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-10Pa, the nitrogen flow rate is 1000-2000sccm, and the deposition temperature is 200-400℃.

[0018] Furthermore, the preparation conditions for the CrAlN coating are as follows: the target material is a CrAl target, the arc current is 80-120A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-10Pa, the nitrogen flow rate is 100-400sccm, and the deposition temperature is 200-400℃.

[0019] Furthermore, the preparation conditions for the TiO2 coating are as follows: titanium isopropoxide or titanium tetrachloride is used as the titanium source precursor, hydrogen peroxide with a mass fraction of 24%–35% is used as the oxygen source, and the introduction times of the titanium source precursor, nitrogen, oxygen source, and nitrogen are 1–2 s, 20–40 s, 0.1–0.3 s, and 20–35 s, respectively; the total number of cycles in the atomic layer deposition process is 1000–3000.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The method for preparing a heterogeneous multilayer coating on a curved inner surface according to the present invention first prepares a Cr / Al / N composite transition layer as the core. The Cr / Al / N composite transition layer has a reasonable structural design, combining the good ductility of Cr, the oxidation barrier effect of Al, and the hard nitride structure formed by N to effectively buffer the thermal expansion mismatch stress and provide a good adhesion effect for the TiO2 coating. The gradient multilayer structure design (Cr / CrAl / CrAlN / CrAl / Cr→TiO2) is a non-single-layer interface transition mode, similar to a "flexible connection". The progressively improving material properties, such as thermal expansion coefficient, hardness, and adhesion, can effectively reduce the concentration of interfacial thermal stress and avoid coating cracking or peeling caused by thermal cycling. The Cr / Al / N composite transition layer mainly reduces residual stress and bridges the titanium dioxide coating and cast iron substrate through excellent interfacial bonding, ensuring high adhesion (film adhesion >723mN) and high-temperature anti-coking performance of the composite transition layer on the curved cylinder liner substrate. Compared with traditional materials, this invention effectively reduces the risk of deformation, peeling, and failure caused by high temperatures, thereby extending the service life of the cylinder liner. Furthermore, the structural design of this heterogeneous layered coating gives the cylinder liner better thermal stability during high-temperature operation, ensuring the engine maintains higher operating efficiency under extreme conditions, reducing energy loss, and enhancing the engine's efficiency and economy in practical use. In this invention, the Cr / Al / N composite transition layer and the TiO2 coating form a composite film, which reduces the contact between the carbon source and the cast iron substrate during high-temperature coking experiments through physical barrier. Simultaneously, the Cr / Al / N composite transition layer and the TiO2 coating form a multi-layered synergistic structure. The high stability of the CrAlN composite transition layer and the catalytic activity of the Cr layer, combined with the anti-coking properties of the TiO2 coating, jointly prevent carbon source adsorption and reaction, significantly improving the excellent high-temperature anti-coking properties of the composite transition layer. Compared to traditional materials / coatings, this invention significantly reduces the risk of high-temperature deformation, peeling, and failure, extending cylinder liner life. Its heterogeneous hierarchical structure gives the cylinder liner better thermal stability, ensuring high engine efficiency and low energy loss under extreme operating conditions, and improving the engine's actual efficiency and economy.

[0022] Furthermore, the performance of heterogeneous layered coatings on curved inner surfaces is mainly affected by film thickness, deposition temperature, substrate pretreatment, atmosphere, and reaction pressure. For the Cr / Al / N composite transition layer, a certain thickness is required to provide excellent bonding, but excessive thickness can lead to stress concentration or cracking. For the TiO2 functional layer, too thin a layer will not provide effective physical barrier and anti-coking effect, while too thick a layer will result in high stress, weak bonding, and easy peeling. Deposition temperature control affects the coating grain morphology and stress state. If the temperature is too high, it will cause stress concentration and even induce interfacial reactions. Substrate preheating can improve interlayer bonding strength and avoid insufficient adhesion caused by cold plating. The ratio of gases such as N2 / O2 / Ar affects the formation of CrN coating, CrAlN composite transition layer, and TiO2 coating. Bias voltage adjustment affects deposition rate, grain size distribution, and internal stress. For TiO2 coatings prepared by ALD, excessively low carrier gas flow rates reduce the removal efficiency of byproducts, which may lead to impurities being incorporated into the coating and affecting the chemical purity of the TiO2 coating. When other process parameters (deposition temperature, pulse pressure, etc.) remain constant, deposition efficiency significantly increases with decreasing deposition chamber pressure. However, excessively low pressure can lead to insufficient precursor molecule concentration, affecting the complete coverage of the coating and consequently the uniformity of the coating thickness. Generally, low-pressure conditions (0.1–3 Pa) can improve coating density and enhance the film's resistance to coking. With increasing introduction time of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen, the coating quality becomes denser and the bonding strength increases. Attached Figure Description

[0023] Figure 1 This is a structural schematic diagram of a curved cylinder liner. In the diagram, 1 represents a curved cylinder liner.

[0024] Figure 2 Here are schematic diagrams of heterogeneous layered coatings, where (a) is a schematic diagram of the coating on a curved surface and (b) is an enlarged view of the heterogeneous layered coating.

[0025] Figure 3 The images show a cylinder liner anti-coking testing device and an infrared thermal imaging photograph, where (a) is a high-temperature combustion testing device and (b) is an infrared thermal imaging photograph.

[0026] Figure 4 The images show a comparison of cylinder liner anti-coating, where (a) is uncoated and (b) is coated.

[0027] Figure 5 The images show a comparison of the surface morphology of the cylinder liner coating before and after combustion, where (a) is the initial state and (b) is the state after combustion.

[0028] Figure 6The coating of Example 1 was subjected to scratch morphology at the critical load LC3 at three different locations according to GB / T 30707-2014, where (a) is the first location, (b) is the second location, and (c) is the third location.

[0029] Figure 7 The scratch morphology of the coating of Comparative Example 1 at the critical load LC3 of the scratch test at three different locations according to GB / T 30707-2014 is shown in (a) for the first location, (b) for the second location, and (c) for the third location. Detailed Implementation

[0030] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0031] This invention relates to a heterogeneous layered coating for curved inner surfaces and its preparation method, which relates to surface engineering and coating technology. It is applicable to the research and development and preparation of heterogeneous layered coatings for curved inner surfaces, aiming to improve the performance and durability of the inner surface of curved components under high temperature and high pressure working conditions, and is suitable for applications in automobile manufacturing, heavy machinery and related fields.

[0032] This invention addresses the issue of coking and sintering in engine cylinder liners under high-temperature conditions. It employs a combination of multi-arc ion plating and atomic layer deposition (ALD) to prepare a Cr / Al / N composite transition layer on the surface of a cast iron cylinder liner, followed by a TiO2 layer, thus forming the composite transition layer. The Cr / Al / N composite transition layer prepared using the multi-arc ion plating method offers advantages such as dense coating, low residual stress, good bonding, and fast deposition rate.

[0033] The curved inner surface heterogeneous layered coating of the present invention includes a Cr / Al / N composite transition layer (including a first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating and a second Cr coating deposited sequentially on the substrate), and a TiO2 coating is deposited on the CrAlN composite transition layer.

[0034] Matrix: Cast iron cylinder liner is selected as the cylinder liner matrix.

[0035] A method for preparing a heterogeneous layered coating on a curved inner surface includes the following steps:

[0036] Surface treatment: The cylinder liner substrate is cleaned and treated. Solvent is used to clean the surface of the cylinder liner substrate to remove grease and dirt. Ultrasonic cleaning is used to remove oxides and impurities from the surface. Then, it is wiped dry with microfiber cloth (or dried with N2).

[0037] 1. After cleaning the substrate with anhydrous ethanol or acetone, a CrAlN coating is deposited on the surface of the cast iron cylinder liner using a multi-arc ion plating method under vacuum.

[0038] II. A TiO2 coating was prepared on the CrAlN coating surface of the cylinder liner using the ALD (atomic layer deposition) method.

[0039] The specific steps are as follows:

[0040] 1) A Cr coating (i.e., Cr substrate layer) with a thickness of 100-300 nm was prepared on the surface of the cast iron cylinder liner substrate using a pure Cr target: arc current 80-100 A, bias voltage 50-150 V, grating 70 degrees, cavity gas pressure 1-2 Pa, nitrogen flow rate 400-800 sccm, and deposition temperature 200-400 °C.

[0041] 2) Using a pure Cr target, a CrN coating with a thickness of 100–500 nm (located between the Cr substrate layer and the CrAlN layer) was prepared on the surface of the Cr coating: the arc current was 80–100 A, the bias voltage was 50–150 V, the grating was 70 degrees, the cavity pressure was 1–10 Pa, the nitrogen flow rate was 1000–2000 sccm, and the deposition temperature was 200–400 °C.

[0042] 3) Using a CrAl target, a CrAlN coating with a thickness of 200–500 nm is prepared on the surface of the CrN coating: arc current 80–120 A, bias voltage 50–150 V, grating degree 70 degrees, cavity pressure 1–10 Pa, nitrogen (as reactant) flow rate 100–400 sccm, and deposition temperature 200–400 °C. The CrAl target is an alloy target with a Cr atomic percentage of 50%–75%.

[0043] 4) Using pure Cr target material, a CrN coating with a thickness of 100-400 nm (located between the CrAlN layer and the surface Cr layer) is prepared on the surface of the CrAlN coating: arc current is 80-100 A, bias voltage is 50-150 V, grating is 70 degrees, cavity gas pressure is 1-10 Pa, nitrogen flow rate is 1000-2000 sccm, and deposition temperature is 200-400 °C.

[0044] 5) Using a pure Cr target, prepare a Cr coating (i.e., Cr surface layer) with a thickness of 100-300 nm on the surface of the CrN coating prepared in step 4): arc current 80-100 A, bias voltage 50-150 V, grating 70 degrees, cavity gas pressure 1-2 Pa, nitrogen flow rate 400-800 sccm, and deposition temperature 200-400 °C.

[0045] 6) Clean the pipeline with N2 5-10 times before using the ALD (Atomic Layer Deposition) equipment.

[0046] Titanium isopropoxide (or titanium tetrachloride) was used as the titanium source precursor, and hydrogen peroxide (24%–35% H2O2 aqueous solution by mass) was used as the oxygen source. A TiO2 coating with a thickness of 100–300 nm was prepared on the surface of the Cr coating prepared in step 5). Nitrogen was used as the purging gas in a single cycle in the ALD equipment. The introduction times of the titanium source precursor, nitrogen, oxygen source, and nitrogen were 1–2 s, 20–40 s, 0.1–0.3 s, and 20–35 s, respectively. The total number of cycles for the atomic layer deposition process was 1000–3000.

[0047] The temperature of the titanium source precursor is 20–90℃, the temperature inside the ALD equipment cavity is 300–400℃, the background vacuum is not less than 40 mtorr, and the working pressure of nitrogen purging is 100–200 mtorr.

[0048] Cylinder liners with a heterogeneous layered coating on a curved inner surface were subjected to prolonged flame thermal shock, with the sample surface temperature controlled at 600–800℃ for 10 hours. During the experiment, an infrared thermal imager was used to monitor the surface temperature of both the uncoated and coated cylinder liners in real time. After a period of continuous combustion, the peeling of the coating and the surface coking morphology were observed.

[0049] The adhesion of heterogeneous multilayer coatings on curved inner surfaces was tested using an Anton Paar MST micron scratch tester with a Rockwell tip of 100 μm radius of curvature. Each sample was tested at three different locations according to GB / T30707-2014. The loading method was linear loading, with a maximum normal loading force of 1 N, a loading rate of 1 N / min, and a scratch length of 300 μm. The critical load at the point of large-area detachment of the heterogeneous multilayer coating on the curved inner surface was determined.

[0050] The following are specific examples.

[0051] Example 1

[0052] (I) Preparation of Cr / Al / N Composite Transition Layer

[0053] The specific process for preparing a Cr / Al / N composite transition layer on a cast iron cylinder liner substrate is as follows:

[0054] (1) The structure of the curved cylinder liner 1 is as follows: Figure 1 As shown. The curved cylinder liner is a cast iron cylinder liner 1, which has a hollow cylindrical structure. The outer surface is a fixed mounting surface, and the inner surface is a working inner wall that directly contacts the piston and undergoes sliding friction. The inner wall surface has a continuous axial curved surface profile. This curved surface is a cylindrical or approximately hyperboloidal structure, designed to adapt to the thermal expansion and dynamic eccentricity changes caused by piston movement under high load and high temperature conditions.

[0055] The cast iron cylinder liner was successively polished with 400-grit, 600-grit, 1000-grit, and 2000-grit sandpaper, followed by polishing with an automatic polishing machine. It was then soaked in acetone or alcohol or cleaned with an ultrasonic cleaner for 15 minutes to ensure the removal of surface oil and impurities. Afterward, it was dried with high-purity nitrogen (99.99% purity N2 gas) or wiped dry with a microfiber cloth. Finally, it was sandblasted with 80-120 mesh alumina particles at a pressure of 0.4-0.6 MPa for 5-10 minutes to ensure a surface roughness of 1.5-3.0 μm.

[0056] (2) Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment, evacuate to below 3 Pa, heat the cast iron cylinder liner to 200℃ and hold for 30 minutes to remove residual moisture and improve coating adhesion, and continue evacuating to 8.0 × 10⁻⁶ Pa. -3 Pa. Then open the intake valve and inject 180 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 300V and 100V in sequence to bombard and clean for 20min, 10min and 10min respectively, so that the target material and cast iron cylinder liner surface are clean.

[0057] (3) Preparation of Cr underlayer (between cylinder liner substrate and CrN layer underlayer): Nitrogen gas with a purity of 99.99% is introduced, the nitrogen flow rate is 800 sccm, the arc current of Cr target is 100A, the gas pressure in the cavity is 1.2Pa, the bias voltage is set to 150V, 120V and 100V respectively, and the corresponding deposition time is 15min, 10min and 5min respectively, to obtain the metal Cr underlayer, the deposition thickness of the Cr underlayer is 200nm.

[0058] (4) Preparation of CrN substrate (between Cr substrate and CrAlN): Nitrogen gas with a purity of 99.99% is introduced at a flow rate of 2000 sccm. The arc current of the Cr target is 100 A, the gas pressure inside the cavity is 3.0 Pa, the bias voltage is set to 100 V, and the deposition time is 20 min to obtain a metallic CrN substrate with a deposition thickness of 400 nm.

[0059] (5) Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 200 sccm and argon gas flow rate of 60 sccm. The arc current of the CrAl target (atomic percentage of 70% Cr and 30% Al) was 100 A, the bias voltage was 100 V, the gas pressure inside the cavity was 1.2 Pa, and the process time was 22 min. The CrAlN coating was obtained with a deposition thickness of 300 nm.

[0060] (6) Preparation of CrN transition layer (between CrAlN layer and Cr top layer): Nitrogen gas with a purity of 99.99% is introduced, the nitrogen flow rate is 2000 sccm, the arc current of Cr target is 100A, the gas pressure in the cavity is 3.0Pa, the bias voltage is 100V, the deposition time is 15min, and the CrN transition layer is obtained with a deposition thickness of 300nm.

[0061] (7) Preparation of Cr top layer: Nitrogen gas with a purity of 99.99% is introduced, the nitrogen gas flow rate is 800 sccm, the arc current of the Cr target is 100A, the gas pressure in the cavity is 1.2Pa, and the bias voltage is set to 150V, 120V and 100V respectively, corresponding to deposition times of 7.5min, 5min and 2.5min, to obtain the Cr top layer. The deposition thickness of the Cr top layer is 100nm, thus forming a Cr / Al / N composite transition layer.

[0062] After the process is completed, the equipment is turned off and allowed to cool to room temperature before the sample is taken out. The cast iron cylinder liner coated with the Cr / Al / N composite transition layer is ultrasonically cleaned with anhydrous ethanol for 15 minutes, and then wiped dry with microfiber cloth or blown dry with nitrogen gas of 99.99% purity.

[0063] (ii) Using ALD equipment to prepare TiO2 coating on cast iron cylinder liners coated with Cr / Al / N composite transition layer.

[0064] (1) Break the vacuum in the ALD equipment, open the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol, transfer the cast iron cylinder liner coated with CrAlN composite transition layer into the ALD equipment chamber, evacuate to the chamber pressure equal to 40 mtorr, use high-purity nitrogen (purity of 99.999%) to impact the entire pipeline, then close the gas valve, continue evacuating to the chamber pressure equal to 40 mtorr, repeat this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front gas valve MV1 and the precursor rear gas valve MV0, open the precursor front gas valve MV1, wait for the pressure value at the precursor front gas valve MV1 to stabilize, close the precursor front gas valve MV1, open the precursor rear gas valve MV0 for about 3 seconds, close the precursor rear gas valve MV0, open the precursor front gas valve MV1 until the chamber pressure equals 40 mtorr, repeat this cycle 5 times to complete the precursor pipeline cleaning operation.

[0065] (2) Set the process parameters: the system vacuum detection time is 5 min, and the vacuum detection pressure is 40.0 mtorr. The program heats up to 300℃ and holds at that temperature. Then, titanium isopropoxide or titanium tetrachloride is used as the titanium source precursor (temperature is 20℃). Hydrogen peroxide (30% H2O2 aqueous solution by mass) is used as the oxygen source, and high-purity nitrogen (99.999% N2 gas purity) is used as the purging gas. The flow rate of high-purity nitrogen is adjusted by the needle valve. The working pressure of high-purity nitrogen purging is 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen are 1.5s, 30s, 0.2s, and 30s, respectively. The total number of cycles is 1700, thereby preparing a TiO2 coating with a thickness of 200 nm on the surface of the cast iron cylinder liner coated with CrAlN composite transition layer.

[0066] Reference Figure 2 Figures 2(a) and 2(b) are schematic diagrams of the heterogeneous layered coatings prepared on the surface of a cast iron substrate.

[0067] Reference Figure 3 In (a), the high-temperature stability of a cast iron cylinder liner with a composite transition layer of Cr / Al / N and TiO2 on its surface was evaluated under flame combustion at a heating rate of 10 °C / min. (Refer to...) Figure 3 In (b), infrared thermal imaging monitoring of its combustion process revealed that the surface combustion temperature was 775℃.

[0068] Reference Figure 4 In image (a), it can be seen that after high-temperature combustion (601℃, 10h), some coking areas were found on the surface of the uncoated cylinder liner; (Refer to image (a)). Figure 4 In Figure (b), it was found that neither the TiO2 coating nor the CrAlN coating on the surface was damaged or peeled off, proving that the TiO2 / CrAlN composite transition layer has good high-temperature anti-peeling performance, and no black coking area was found.

[0069] Reference Figure 5 In (a), before the combustion test, the surface of the composite transition layer exhibits a large number of spherical particles of varying sizes, which are evenly distributed and have a relatively regular structure. This indicates that before the coking test, the heterogeneous layer transition layer and TiO2 are evenly distributed in the form of spherical particles, forming a stable film microstructure.

[0070] Reference Figure 5 In (b), after the coking test, the surface particle density increased, some particles agglomerated into spherical structures, and the particle surface became rougher, but no carbon source enrichment was observed. This indicates that Cr / CrAl / CrAlN / CrAl / Cr and TiO2 form a multilayer synergistic structure. The high stability of CrAlN and the catalytic activity of Cr, combined with the anti-coking properties of TiO2, jointly prevent the adsorption and reaction of carbon sources.

[0071] Reference Figure 6 In Figures (a), (b), and (c), the film adhesion was tested using an Anton Paar MST micron scratch tester. The critical load L for scratch testing at three different locations selected in Example 1 according to GB / T 30707-2014 standard was used. C3 The shape of the scratch is as follows Figure 6 As shown, the sample has high adhesion, with an average adhesion of 729 mN for the heterogeneous layer coating on the curved inner surface.

[0072] Example 2

[0073] Step 1: Grind the cast iron cylinder liner sequentially with 400 grit, 600 grit, 1000 grit, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.5 to 0.7 MPa to ensure that the surface roughness reaches 2.0 to 3.5 μm.

[0074] Step Two: Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment and evacuate to 8.0 × 10⁻⁶. -3 Below Pa, heat the cast iron cylinder liner to 300℃ and hold for 30 minutes to remove residual moisture and improve coating adhesion. Then open the intake valve and inject 400 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 400V, and 200V respectively for 20 minutes, 10 minutes, and 10 minutes to bombard and clean the target material and cast iron cylinder liner surface.

[0075] Preparation of Cr substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 600 sccm. The arc current of the Cr target was 80 A, the gas pressure inside the cavity was 1.5 Pa, the bias voltage was 100 V, and the deposition time was 15 min to obtain a metallic Cr substrate with a deposition thickness of 100 nm.

[0076] Preparation of CrN substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1500 sccm. The arc current of the Cr target was 80 A, the gas pressure inside the cavity was 2 Pa, the bias voltage was 100 V, and the deposition time was 15 min to obtain the CrN substrate with a deposition thickness of 300 nm.

[0077] Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 300 sccm, argon gas flow rate was 60 sccm, arc current of CrAl target (atomic percentage of 70% Cr, 30% Al) was 100 A, bias voltage was 150 V, internal pressure was 1.5 Pa, and process time was 30 min, resulting in CrAlN coating with a deposition thickness of 350 nm.

[0078] Preparation of CrN transition layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1500 sccm, the arc current of the Cr target was 80 A, the gas pressure inside the cavity was 2 Pa, the bias voltage was set to 100 V, and the deposition time was 15 min to obtain the CrN transition layer with a deposition thickness of 300 nm.

[0079] Preparation of the Cr top layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 800 sccm. The arc current of the Cr target was 100 A, the gas pressure inside the cavity was 1.5 Pa, and the bias voltage was set to 150 V, 100 V, and 50 V in sequence, corresponding to deposition times of 7.5 min, 5 min, and 2.5 min, respectively, to obtain the Cr top layer. The deposition thickness of the Cr top layer was 100 nm, thus forming a Cr / Al / N composite transition layer.

[0080] Step 3: After the process is completed, turn off the equipment and allow it to cool to room temperature before taking out the sample. Use anhydrous ethanol to ultrasonically clean the cast iron cylinder liner coated with the Cr / Al / N composite transition layer for 15 minutes, and then wipe it dry with a microfiber cloth or blow it dry with nitrogen gas of 99.99% purity.

[0081] Step 4: Prepare a TiO2 coating on the cast iron cylinder liner coated with a Cr / Al / N composite transition layer using an ALD device.

[0082] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the CrAlN-plated cast iron cylinder liner into the ALD equipment chamber, evacuate to a chamber pressure of 40 mtorr, and then use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline before closing the valve. Continue evacuating to a chamber pressure of 40 mtorr, repeating this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front valve MV1 and the precursor rear valve MV0, and open the precursor front valve MV1. After the pressure at the precursor front valve MV1 stabilizes, close the precursor front valve MV1, open the precursor rear valve MV0 for about 3 seconds, close the precursor rear valve MV0, and open the precursor front valve MV1 until the chamber pressure reaches 40 mtorr. Repeat this process 5 times to complete the precursor pipeline cleaning operation.

[0083] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 1.5s, 20s, 0.2s, and 20s, respectively, with a total of 1300 cycles, thereby preparing a 100nm thick TiO2 coating on the surface of a CrAlN-coated cast iron cylinder liner.

[0084] After testing, the samples prepared in Example 2 and the uncoated samples were evaluated for high-temperature stability under flame combustion (680℃, 10h). Coking areas were found on the surface of the uncoated cylinder liner. The TiO2 coating and Cr / Al / N composite transition layer on the coated surface did not break or peel off. The average adhesion of the heterogeneous layer coating on the curved inner surface was 723mN.

[0085] Example 3

[0086] Step 1: Grind the cast iron cylinder liner sequentially with 400 grit, 600 grit, 1000 grit, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.4 to 0.6 MPa to ensure that the surface roughness reaches 1.5 to 3.0 μm.

[0087] Step Two: Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment and evacuate to 8.0 × 10⁻⁶. -3 Below Pa, heat the cast iron cylinder liner to 300℃ and hold for 30 minutes to remove residual moisture and improve coating adhesion. Then open the intake valve and inject 300 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 400V, and 200V respectively for 20 minutes, 10 minutes, and 10 minutes to bombard and clean the target material and cast iron cylinder liner surface.

[0088] Preparation of Cr substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 400 sccm. The arc current of the Cr target was 80 A, the gas pressure inside the cavity was 1 Pa, and the bias voltage was set to 150 V, 120 V, and 100 V in sequence, corresponding to deposition times of 20 min, 15 min, and 10 min, respectively, to obtain a metallic Cr substrate with a deposition thickness of 300 nm.

[0089] Preparation of CrN substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 2000 sccm. The arc current of the Cr target was 80 A, the gas pressure inside the cavity was 3.5 Pa, the bias voltage was set to 100 V, and the deposition time was 30 min to obtain the CrN substrate with a deposition thickness of 400 nm.

[0090] Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 300 sccm, argon gas flow rate was 60 sccm, arc current of CrAl target (atomic percentage of 65% Cr, 35% Al) was 120 A, bias voltage was 150 V, internal pressure was 1.7 Pa, process time was 27 min, and the deposition thickness of CrAlN coating was 350 nm.

[0091] Preparation of CrN transition layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1500 sccm, the arc current of the Cr target was 90 A, the gas pressure inside the cavity was 3 Pa, the bias voltage was set to 100 V, and the deposition time was 25 min to obtain the CrN transition layer with a deposition thickness of 400 nm.

[0092] Preparation of the Cr top layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 600 sccm. The arc current of the Cr target was 100 A, the gas pressure inside the cavity was 1.5 Pa, the bias voltage was set to 100 V, and the corresponding deposition time was 20 min, resulting in a CrN top layer with a deposition thickness of 150 nm, thus forming a Cr / Al / N composite transition layer.

[0093] Step 3: After the process is completed, turn off the equipment and allow it to cool to room temperature before taking out the sample. Use anhydrous ethanol to ultrasonically clean the cast iron cylinder liner coated with the Cr / Al / N composite transition layer for 15 minutes, and then wipe it dry with a microfiber cloth or blow it dry with nitrogen gas of 99.99% purity.

[0094] Step 4: Prepare a TiO2 coating on the cast iron cylinder liner coated with a Cr / Al / N composite transition layer using an ALD device.

[0095] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the CrAlN-plated cast iron cylinder liner into the ALD equipment chamber, evacuate to a chamber pressure of 40 mtorr, and then use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline before closing the valve. Continue evacuating to a chamber pressure of 40 mtorr, repeating this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front valve MV1 and the precursor rear valve MV0, and open the precursor front valve MV1. After the pressure at the precursor front valve MV1 stabilizes, close the precursor front valve MV1, open the precursor rear valve MV0 for about 3 seconds, close the precursor rear valve MV0, and open the precursor front valve MV1 until the chamber pressure reaches 40 mtorr. Repeat this process 5 times to complete the precursor pipeline cleaning operation.

[0096] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2 purity) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 2s, 20s, 0.3s, and 20s, respectively, with a total of 1000 cycles, thereby preparing a 120nm thick TiO2 coating on the surface of a CrAlN-coated cast iron cylinder liner.

[0097] After testing, the samples prepared in Example 3 and the uncoated samples were evaluated for high-temperature stability under flame combustion (800℃, 10h). Coking areas were found on the surface of the uncoated cylinder liner. The TiO2 coating and Cr / Al / N composite transition layer on the coated surface did not break or peel off. The average adhesion of the heterogeneous layer coating on the curved inner surface was 739mN.

[0098] Example 4

[0099] Step 1: Grind the cast iron cylinder liner sequentially with 400 grit, 600 grit, 1000 grit, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.5 to 0.7 MPa to ensure that the surface roughness reaches 2.0 to 3.5 μm.

[0100] Step Two: Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment and evacuate to 8.0 × 10⁻⁶. -3 Below Pa, heat the cast iron cylinder liner to 220℃ and hold for 40 minutes to remove residual moisture and improve coating adhesion. Then open the intake valve and inject 400 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 400V, and 200V respectively to bombard and clean for 20 minutes, 10 minutes, and 10 minutes respectively, so as to clean the target material and the surface of the cast iron cylinder liner.

[0101] Preparation of Cr substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 800 sccm. The arc current of the Cr target was 95 A, the gas pressure inside the cavity was 2 Pa, and the bias voltage was set to 130 V, 90 V, and 50 V in sequence, corresponding to deposition times of 18 min, 12 min, and 6 min, to obtain a metallic Cr substrate with a deposition thickness of 300 nm.

[0102] Preparation of CrN substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 2000 sccm. The arc current of the Cr target was 100 A, the gas pressure inside the cavity was 3.2 Pa, the bias voltage was set to 110 V, and the deposition time was 32 min to obtain the CrN substrate with a deposition thickness of 500 nm.

[0103] Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 180 sccm, argon gas flow rate was 70 sccm, arc current of CrAl target (atomic percentage of 65% Cr, 35% Al) was 115 A, bias voltage was 100 V, gas pressure inside the cavity was 1 Pa, and process time was 90 s.

[0104] Preparation of CrN transition layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1000 sccm, the arc current of the Cr target was 100 A, the gas pressure inside the cavity was 1.3 Pa, the bias voltage was 100 V, and the deposition time was 60 s to obtain the CrN transition layer.

[0105] The CrAlN layer and CrN transition layer were prepared in 20 cycles, with a total deposition thickness of 800 nm.

[0106] Preparation of the Cr top layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 800 sccm. The arc current of the Cr target was 100 A, the gas pressure inside the cavity was 1.5 Pa, and the bias voltage was set to 100 V, 80 V, and 50 V in sequence, corresponding to deposition times of 7.5 min, 5 min, and 2.5 min, respectively, to obtain the CrN top layer. The deposition thickness of the Cr top layer was 100 nm, thus forming a Cr / Al / N composite transition layer.

[0107] Step 3: After the process is completed, turn off the equipment and allow it to cool to room temperature before taking out the sample. Use anhydrous ethanol to ultrasonically clean the cast iron cylinder liner coated with the Cr / Al / N composite transition layer for 15 minutes, and then wipe it dry with a microfiber cloth or blow it dry with nitrogen gas of 99.99% purity.

[0108] Step 4: Prepare a TiO2 coating on the cast iron cylinder liner coated with a Cr / Al / N composite transition layer using an ALD device.

[0109] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the CrAlN-plated cast iron cylinder liner into the ALD equipment chamber, evacuate to a chamber pressure of 40 mtorr, and then use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline before closing the valve. Continue evacuating to a chamber pressure of 40 mtorr, repeating this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front valve MV1 and the precursor rear valve MV0, open the precursor front valve MV1, and wait for the pressure at the precursor front valve MV1 to stabilize. Then close the precursor front valve MV1, open the precursor rear valve MV0 for about 3 seconds, close the precursor rear valve MV0, and open the precursor front valve MV1 until the chamber pressure reaches 40 mtorr. Repeat this process 5 times to complete the precursor pipeline cleaning operation.

[0110] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 350℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 1.8s, 25s, 0.3s, and 35s, respectively, with a total of 2000 cycles, thereby preparing a TiO2 coating with a thickness of 220 nm on the surface of a CrAlN-coated cast iron cylinder liner.

[0111] After testing, the samples prepared in Example 4 and the uncoated samples were evaluated for high-temperature stability under flame combustion (760℃, 10h). Coking areas were found on the surface of the uncoated cylinder liner. The TiO2 coating and Cr / Al / N composite transition layer on the coated surface did not break or peel off. The average adhesion of the heterogeneous layer coating on the curved inner surface was 738mN.

[0112] Example 5

[0113] Step 1: Grind the cast iron cylinder liner sequentially with 400 grit, 600 grit, 1000 grit, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.4 to 0.6 MPa to ensure that the surface roughness reaches 1.5 to 3.0 μm.

[0114] Step Two: Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment and evacuate to 8.0 × 10⁻⁶. -3 Below Pa, heat the cast iron cylinder liner to 300℃ and hold for 30 minutes to remove residual moisture and improve coating adhesion. Then open the intake valve and inject 300 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 400V, and 200V respectively for 20 minutes, 10 minutes, and 10 minutes to bombard and clean the target material and cast iron cylinder liner surface.

[0115] Preparation of Cr substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 500 sccm. The arc current of the Cr target was 85 A, the gas pressure inside the cavity was 1 Pa, and the bias voltage was set to 150 V, 120 V, and 100 V in sequence, corresponding to deposition times of 15 min, 10 min, and 5 min, respectively, to obtain a metallic Cr substrate with a deposition thickness of 220 nm.

[0116] Preparation of CrN substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1000 sccm. The arc current of the Cr target was 90 A, the gas pressure inside the cavity was 10 Pa, the bias voltage was set to 120 V, and the deposition time was 10 min to obtain the CrN substrate with a deposition thickness of 100 nm.

[0117] Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 100 sccm, argon gas flow rate was 60 sccm, arc current of CrAl target (atomic percentage of 50% Cr, 50% Al) was 80 A, bias voltage was 80 V, internal pressure was 10 Pa, process time was 20 min, and the deposition thickness of CrAlN coating was 200 nm.

[0118] Preparation of CrN transition layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1000 sccm, the arc current of the Cr target was 80 A, the gas pressure inside the cavity was 1 Pa, the bias voltage was set to 80 V, and the deposition time was 10 min to obtain the CrN transition layer with a deposition thickness of 100 nm.

[0119] Preparation of the Cr top layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 400 sccm. The arc current of the Cr target was 80 A, the gas pressure inside the cavity was 1 Pa, and the bias voltage was set to 100 V, 80 V, and 60 V in sequence, corresponding to deposition times of 20 min, 15 min, and 5 min, respectively, to obtain the CrN top layer. The deposition thickness of the Cr top layer was 300 nm, thus forming a Cr / Al / N composite transition layer.

[0120] Step 3: After the process is completed, turn off the equipment and allow it to cool to room temperature before taking out the sample. Use anhydrous ethanol to ultrasonically clean the cast iron cylinder liner coated with the Cr / Al / N composite transition layer for 15 minutes, and then wipe it dry with a microfiber cloth or blow it dry with nitrogen gas of 99.99% purity.

[0121] Step 4: Prepare a TiO2 coating on the cast iron cylinder liner coated with a Cr / Al / N composite transition layer using an ALD device.

[0122] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the CrAlN-plated cast iron cylinder liner into the ALD equipment chamber, evacuate to a chamber pressure of 40 mtorr, and then use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline before closing the valve. Continue evacuating to a chamber pressure of 40 mtorr, repeating this cycle 4 times to complete the pipeline cleaning operation. Then close the precursor front valve MV1 and the precursor rear valve MV0, and open the precursor front valve MV1. After the pressure at the precursor front valve MV1 stabilizes, close the precursor front valve MV1, open the precursor rear valve MV0 for about 3 seconds, close the precursor rear valve MV0, and open the precursor front valve MV1 until the chamber pressure reaches 40 mtorr. Repeat this process 5 times to complete the precursor pipeline cleaning operation.

[0123] The process parameters were set as follows: system vacuum detection time was 1 min, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of the titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 1s, 20s, 0.1s, and 20s, respectively, with a total of 1200 cycles, thereby preparing a 100nm thick TiO2 coating on the surface of a CrAlN-coated cast iron cylinder liner.

[0124] Example 6

[0125] Step 1: Grind the cast iron cylinder liner sequentially with 400 grit, 600 grit, 1000 grit, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.4 to 0.6 MPa to ensure that the surface roughness reaches 1.5 to 3.0 μm.

[0126] Step Two: Remove dust from the cavity of the multi-arc ion plating equipment using a vacuum cleaner, and wipe the inner wall of the cavity with anhydrous ethanol. After fixing the cast iron cylinder liner to the rotating frame, place it into the multi-arc ion plating equipment and evacuate to 8.0 × 10⁻⁶. -3 Below Pa, heat the cast iron cylinder liner to 300℃ and hold for 30 minutes to remove residual moisture and improve coating adhesion. Then open the intake valve and inject 300 sccm of argon gas. Set the target bias voltage to 600V and the grating to 70 degrees. Adjust the bias voltage to 600V, 400V, and 200V respectively for 20 minutes, 10 minutes, and 10 minutes to bombard and clean the target material and cast iron cylinder liner surface.

[0127] Preparation of Cr substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 600 sccm. The arc current of the Cr target was 90 A, the gas pressure inside the cavity was 2 Pa, and the bias voltage was set to 120 V, 100 V, and 80 V in sequence, corresponding to deposition times of 15 min, 10 min, and 5 min, respectively, to obtain a metallic Cr substrate with a deposition thickness of 200 nm.

[0128] Preparation of CrN substrate: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 1500 sccm. The arc current of the Cr target was 100 A, the gas pressure inside the cavity was 1 Pa, the bias voltage was set to 120 V, and the deposition time was 10 min to obtain the CrN substrate with a deposition thickness of 300 nm.

[0129] Preparation of CrAlN layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 400 sccm, argon gas flow rate was 70 sccm, arc current of CrAl target (atomic percentage of 75% Cr, 25% Al) was 90 A, bias voltage was 110 V, internal pressure was 5 Pa, process time was 30 min, and the deposition thickness of CrAlN coating was 500 nm.

[0130] Preparation of CrN transition layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 2000 sccm, the arc current of the Cr target was 90 A, the gas pressure inside the cavity was 10 Pa, the bias voltage was set to 60 V, and the deposition time was 10 min to obtain the CrN transition layer with a deposition thickness of 200 nm.

[0131] Preparation of the Cr top layer: Nitrogen gas with a purity of 99.99% was introduced at a flow rate of 500 sccm. The arc current of the Cr target was 90 A, the gas pressure inside the cavity was 2 Pa, and the bias voltage was set to 100 V, 80 V, and 60 V in sequence, corresponding to deposition times of 7.5 min, 5 min, and 2.5 min, respectively, to obtain the CrN top layer. The deposition thickness of the Cr top layer was 200 nm, thus forming a Cr / Al / N composite transition layer.

[0132] Step 3: After the process is completed, turn off the equipment and allow it to cool to room temperature before taking out the sample. Use anhydrous ethanol to ultrasonically clean the cast iron cylinder liner coated with the Cr / Al / N composite transition layer for 15 minutes, and then wipe it dry with a microfiber cloth or blow it dry with nitrogen gas of 99.99% purity.

[0133] Step 4: Prepare a TiO2 coating on the cast iron cylinder liner coated with a Cr / Al / N composite transition layer using an ALD device.

[0134] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the CrAlN-plated cast iron cylinder liner into the ALD equipment chamber, evacuate to a chamber pressure of 40 mtorr, and then use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline before closing the valve. Continue evacuating to a chamber pressure of 40 mtorr, repeating this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front valve MV1 and the precursor rear valve MV0, and open the precursor front valve MV1. After the pressure at the precursor front valve MV1 stabilizes, close the precursor front valve MV1, open the precursor rear valve MV0 for about 3 seconds, close the precursor rear valve MV0, and open the precursor front valve MV1 until the chamber pressure reaches 40 mtorr. Repeat this process 5 times to complete the precursor pipeline cleaning operation.

[0135] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2 purity) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 2s, 30s, 0.2s, and 30s, respectively, with a total of 3000 cycles, thereby preparing a 300nm thick TiO2 coating on the surface of a CrAlN-coated cast iron cylinder liner.

[0136] The adhesion test results of the coatings prepared in Examples 1-4 are shown in Table 1.

[0137] Table 1. Adhesion test results of heterogeneous layered coatings on curved inner surfaces.

[0138]

[0139]

[0140] Comparative Example 1

[0141] Step 1: Grind the cast iron cylinder liner sequentially with 400, 600, 1000, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.4 to 0.6 MPa to ensure that the surface roughness reaches 1.5 to 3.0 μm.

[0142] Step 2: Prepare a TiO2 coating on the cast iron cylinder liner using an ALD device.

[0143] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the cast iron cylinder liner into the ALD equipment chamber and evacuate until the chamber pressure equals 40 mtorr. Use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline, then close the gas valve. Continue evacuating until the chamber pressure equals 40 mtorr. Repeat this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front gas valve MV1 and the precursor rear gas valve MV0, and open the precursor front gas valve MV1. After the pressure at the precursor front gas valve MV1 stabilizes, close the precursor front gas valve MV1, open the precursor rear gas valve MV0 for about 3 seconds, then close the precursor rear gas valve MV0 and open the precursor front gas valve MV1 until the chamber pressure equals 40 mtorr. Repeat this cycle 5 times to complete the precursor pipeline cleaning operation.

[0144] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2 purity) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 1.5s, 30s, 0.2s, and 30s, respectively, with a total of 1700 cycles, thereby preparing a 200nm thick TiO2 coating on the surface of the cast iron cylinder liner.

[0145] Reference Figure 7 In Figures (a), (b), and (c), the film adhesion was tested using an Anton Paar MST micron scratch tester. The critical load L for scratch testing at three different locations selected according to GB / T 30707-2014 standard was compared in Comparative Example 1. C3 The shape of the scratch is as follows Figure 7 As shown, the sample has low adhesion, with an average adhesion of 293 mN for the TiO2 coating. The film peels off significantly during the scratching process, indicating that the bonding force between the single-layer TiO2 coating and the cast iron substrate is insufficient.

[0146] Comparative Example 2

[0147] Step 1: Grind the cast iron cylinder liner sequentially with 400, 600, 1000, and 2000 grit sandpaper, then polish it with an automatic polishing machine. Soak it in acetone or alcohol or use ultrasonic cleaning for 15 minutes to ensure that surface oil and impurities are removed. After that, blow it dry with high-purity nitrogen (99.99% purity nitrogen) and sandblast it for 5 to 10 minutes at a pressure of 0.4 to 0.6 MPa to ensure that the surface roughness reaches 1.5 to 3.0 μm.

[0148] Step 2: Prepare a TiO2 coating on the cast iron cylinder liner using an ALD device.

[0149] After breaking the vacuum in the ALD equipment and opening the chamber door, wipe the inner wall and tray of the chamber with anhydrous ethanol. Transfer the cast iron cylinder liner into the ALD equipment chamber and evacuate until the chamber pressure equals 40 mtorr. Use high-purity nitrogen (99.999% purity) to impinge on the entire pipeline, then close the gas valve. Continue evacuating until the chamber pressure equals 40 mtorr. Repeat this cycle 4-5 times to complete the pipeline cleaning operation. Then close the precursor front gas valve MV1 and the precursor rear gas valve MV0, and open the precursor front gas valve MV1. After the pressure at the precursor front gas valve MV1 stabilizes, close the precursor front gas valve MV1, open the precursor rear gas valve MV0 for about 3 seconds, then close the precursor rear gas valve MV0 and open the precursor front gas valve MV1 until the chamber pressure equals 40 mtorr. Repeat this cycle 5 times to complete the precursor pipeline cleaning operation.

[0150] The process parameters were set as follows: system vacuum detection time was 5 minutes, and vacuum detection pressure was 40.0 mtorr. The temperature was programmed to rise to 300℃ and held, then titanium isopropoxide or titanium tetrachloride was used as the titanium source precursor (temperature 20℃). Hydrogen peroxide (30% H2O2 aqueous solution) was used as the oxygen source, and high-purity nitrogen (99.999% N2 purity) was used as the purging gas. The flow rate of high-purity nitrogen was adjusted by a needle valve, and the working pressure during high-purity nitrogen purging was 150 mtorr. In a single cycle of ALD, the introduction times of titanium source precursor, high-purity nitrogen, hydrogen peroxide, and high-purity nitrogen were 1.5s, 20s, 0.2s, and 20s, respectively, with a total of 1300 cycles, thereby preparing a 100nm thick TiO2 coating on the surface of the cast iron cylinder liner.

[0151] The adhesion of the film to the substrate was tested using an Anton Paar MST micron scratch tester. In Comparative Example 2, the critical load for scratch testing at three different locations selected according to the GB / T30707-2014 standard was 252mN. The film layer peeled off significantly during the scratching process, indicating that the bonding force between the single-layer TiO2 coating and the cast iron substrate was insufficient.

[0152] The adhesion test results of the TiO2 coatings prepared in Comparative Example 2 and Comparative Example 3 are shown in Table 2.

[0153] Table 2. Adhesion test results of TiO2 coating

[0154]

[0155]

[0156] In this embodiment of the invention, a Cr / Al / N composite transition layer was introduced on the substrate surface before a TiO2 coating was deposited. The resulting curved inner surface heterogeneous layered coating achieved an average LC3 adhesion value of 729 mN under the same test conditions, which was significantly higher than the 293 mN and 252 mN of the comparative examples. This indicates that the composite heterogeneous layered structure can significantly improve the bonding strength of the TiO2 film under complex thermomechanical loads.

[0157] This invention is primarily applied to the surface modification of curved inner surfaces. By preparing a chromium / aluminum / nitrogen (Cr / Al / N) composite transition layer on a cast iron cylinder liner substrate, and further depositing a titanium dioxide (TiO2) coating on its surface using atomic layer deposition (ALD), the performance of the cylinder liner under high temperature and high load conditions is significantly improved, and the residual stress of the TiO2 substrate is effectively reduced. This composite transition layer effectively prevents spalling and deformation caused by high temperatures, extending the service life of the cylinder liner and improving overall working efficiency. Furthermore, the excellent properties of the TiO2 coating further enhance the structural stability and anti-coking ability of the coating.

[0158] The above description is only of the preferred embodiment of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. All variations made within the scope of the independent claims of the present invention are also within the scope of protection of the present invention.

[0159] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

Claims

1. A heterogeneous layered coating for a curved inner surface, characterized in that, It includes a first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating, a second Cr coating, and a TiO2 coating sequentially disposed on a substrate.

2. The curved inner surface heterogeneous layered coating according to claim 1, characterized in that, The thickness of the first Cr coating is 100–300 nm, the thickness of the first CrN coating is 100–500 nm, the thickness of the CrAlN coating is 200–500 nm, the thickness of the second CrN coating is 100–400 nm, the thickness of the second Cr coating is 100–300 nm, and the thickness of the TiO2 coating is 100–300 nm.

3. A method for preparing a heterogeneous layered coating on a curved inner surface, characterized in that, Includes the following steps: A first Cr coating, a first CrN coating, a CrAlN coating, a second CrN coating, and a second Cr coating were prepared layer by layer on the surface of the substrate to obtain a CrAlN composite transition layer. A TiO2 coating was prepared on the surface of a substrate coated with a Cr / Al / N composite transition layer.

4. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The CrAlN composite transition layer was prepared using a multi-arc ion plating method.

5. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The TiO2 coating was prepared using atomic layer deposition.

6. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The thickness of the first Cr coating is 100–300 nm, the thickness of the first CrN coating is 100–500 nm, the thickness of the CrAlN coating is 200–500 nm, the thickness of the second CrN coating is 100–400 nm, the thickness of the second Cr coating is 100–300 nm, and the thickness of the TiO2 coating is 100–300 nm.

7. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The preparation conditions for the first and second Cr coatings are as follows: the target material is a Cr target, the arc current is 80-100A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-2Pa, the nitrogen flow rate is 400-800sccm, and the deposition temperature is 200-400℃.

8. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The preparation conditions for the first and second CrN coatings are as follows: the target material is a Cr target, the arc current is 80-100A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-10Pa, the nitrogen flow rate is 1000-2000sccm, and the deposition temperature is 200-400℃.

9. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The preparation conditions for the CrAlN coating are as follows: the target material is CrAl target, the arc current is 80-120A, the bias voltage is 50-150V, the grating is 70 degrees, the cavity gas pressure is 1-10Pa, the nitrogen flow rate is 100-400sccm, and the deposition temperature is 200-400℃.

10. The method for preparing a heterogeneous layered coating on a curved inner surface according to claim 3, characterized in that, The preparation conditions for the TiO2 coating are as follows: titanium isopropoxide or titanium tetrachloride is used as the titanium source precursor, hydrogen peroxide with a mass fraction of 24% to 35% is used as the oxygen source, and the introduction times of the titanium source precursor, nitrogen, oxygen source and nitrogen are 1 to 2 s, 20 to 40 s, 0.1 to 0.3 s and 20 to 35 s respectively; the total number of cycles of the atomic layer deposition process is 1000 to 3000.

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