A surface coating structure of a mud-water balance pipe jacking machine cutter head and its surface treatment method

Abstract

This application relates to the field of composite cutterhead slurry pipe jacking machines and provides a surface coating structure for a slurry pipe jacking machine cutter head and a surface treatment method thereof. The coating structure comprises, starting from the surface layer of the cutter head substrate, a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer, and a nanocrystalline composite alloy layer. This application utilizes a vacuum PVD coating process and a laser cladding process to form a wear-resistant, high-strength coating on the surface of the slurry pipe jacking machine cutter head, thereby increasing the cutter head's hardness and wear resistance, and extending its service life by 3 to 5 times, thereby reducing the frequency of cutter head replacement during slurry pipe jacking machine construction.

Description

Technical Field

[0001] The present application relates to the field of composite cutterhead slurry-water balanced pipe jacking machines, and in particular to a surface coating structure of a cutter head of a slurry-water balanced pipe jacking machine and a surface treatment method thereof. Background Art

[0002] A hard coating is a coating with a certain thickness and a microhardness of 20 GPa or higher. Due to its high hardness, low friction coefficient, and excellent high-temperature and corrosion resistance, hard coatings are playing an increasingly important role in machining, mold manufacturing, geological drilling, the textile industry, and aerospace.

[0003] With the development of social economy, the improvement of infrastructure, and especially the accelerated urbanization process, the number of pipeline projects for the transmission of liquid and gaseous media crossing roads, rivers, and buildings in and outside cities is increasing, and trenchless technology has been widely used. Slurry-balanced pipe jacking is a mechanical and automated pipe jacking construction method that cuts the soil through the entire cross-section, balances the soil pressure and groundwater pressure with slurry pressure, and uses slurry as the medium for conveying waste soil. Slurry-balanced pipe jacking machines have the advantages of adapting to a wide range of soil layers, having a stable excavation surface, and minimal ground settlement. They are highly adaptable in large and medium-sized pipelines crossing roads, rivers, and other pipeline projects, and therefore have been widely used. Slurry-balanced pipe jacking machines use water to convey waste soil media. During the excavation process, the cutters on the cutterhead fracture and scrape the rock and soil in front, making them key components for realizing the excavation function of the composite cutterhead slurry-balanced pipe jacking machine.

[0004] Slurry pipe jacking machines encounter a variety of complex strata during construction, especially in composite strata. The forces acting on the cutterhead during excavation are quite complex, which can easily cause wear on the cutter and cutterhead, seriously affecting excavation efficiency, construction quality, and project costs. Therefore, how to extend the service life of the cutterhead and reduce the frequency of work stoppages for cutter replacement are currently key challenges in slurry pipe jacking operations.

[0005] Numerous studies have been conducted both domestically and internationally to improve the wear and impact resistance of cutting heads and extend their service life. Currently, the most widely used method is to improve these properties through surface modification. For example, chemical heat treatment, electrochemical treatment, or thermal spraying can be used to coat the cutting head surface with a coating, thereby improving the wear resistance of the substrate surface. However, thermal spraying and chemical heat treatment processes have drawbacks such as high process requirements, thin coatings, a lack of metallurgical bonding between the substrate and the coating, and the coating being easily worn away.

[0006] The existing slurry balance pipe jacking machine cutter head has poor overall strength and wear resistance, which reduces its service life. To this end, we propose a slurry balance pipe jacking machine cutter head surface coating structure and a surface treatment method thereof. Summary of the Invention

[0007] In order to solve the problems of poor overall strength and wear resistance and short service life of the existing composite cutter head of a slurry-water balanced pipe jacking machine, the present application provides a surface coating structure of the cutter head of a slurry-water balanced pipe jacking machine and a surface treatment method thereof.

[0008] The surface coating structure of the cutter head of a slurry-water balanced pipe jacking machine provided in this application adopts the following technical solution:

[0009] A surface coating structure of a cutter head for a slurry-water balancing pipe jacking machine comprises, starting from the surface layer of a cutter head substrate, a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer; the thickness of the zirconium alloy layer is 0.5 to 2 microns, the thickness of the titanium alloy layer is 0.5 to 1 micron, the thickness of the titanium carbide alloy layer is 1 to 5 microns, the thickness of the nanocrystalline composite alloy layer is 10 to 50 microns, and the nanocrystalline composite alloy layer is a composite nanocrystalline powder laser cladding layer.

[0010] By adopting the above technical solution and innovative coating structure design, the combination of metal substrate, zirconium alloy layer, titanium alloy layer, titanium carbide alloy layer and nanocrystalline composite alloy layer can greatly improve the bonding strength between the coating and the substrate, while eliminating the residual stress between the coatings, improving the oxidation resistance and anti-adhesion ability of the slurry balance pipe jacking machine cutter head, and the coating is not easy to fall off during use.

[0011] Preferably, the composite nanocrystalline powder is composed of nano-Al powder, nano-Co powder, nano-Si powder, nano-Mo powder, nano-WC powder, and nano-Al2O3 powder in a molar ratio of 0.2-0.7: 0.3-1.2: 0.1-0.5: 0.1-0.3: 0.3-1: 0.05-0.1.

[0012] By adopting the above technical solution and selecting the composition and dosage relationship of the composite nanocrystalline powder, the matching problem between some components of the nanocrystalline composite alloy layer is solved, as well as the problems of obtaining ultra-high wear resistance and strength. First of all, tungsten carbide WC has the advantages of high melting point, high hardness, good chemical stability and good thermal stability. WC has good wettability with Co. Tungsten carbide WC dissolves in Co and forms a solid solution. Tungsten carbide WC has a tendency to grow unevenly during high-temperature deposition, forming fine grains, which play a role in wear-resistant core. WC particles are the main wear-resistant component and have a hardness comparable to that of diamond, while Co provides the toughness required for the nanocrystalline composite alloy layer. Nano Mo powder has high high-temperature strength and high-temperature hardness, good thermal conductivity, electrical conductivity, and good corrosion resistance, etc., and has the function of improving the fluidity of the nanocrystalline composite alloy layer. Nano alumina has many excellent properties of ordinary alumina, such as high hardness, high strength, corrosion resistance, wear resistance, high temperature resistance, high insulation, and high oxidation resistance. With strong volume effect, quantum size effect, surface effect and macroscopic quantum tunneling effect, it is beneficial to enhance the strong bonding force and density of the nanocrystalline composite alloy layer; nano aluminum powder has the function of reducing the sintering temperature of the nanocrystalline composite alloy layer and increasing the density and thermal conductivity of the sintered body; nano Si powder increases the melting point, heat resistance and high resistivity of the nanocrystalline composite alloy layer and has a high antioxidant effect.

[0013] Preferably, the powder diameter of the nano-Al powder is 50 to 100 nanometers, the powder diameter of the nano-Co powder is 50 to 100 nanometers, the powder diameter of the nano-Si powder is 30 to 80 nanometers, the powder diameter of the nano-Mo powder is 50 to 100 nanometers, the powder diameter of the nano-WC powder is 50 to 100 nanometers, and the powder diameter of the nano-Al2O3 powder is 40 to 90 nanometers.

[0014] By adopting the above technical solution, the powder particle size distribution of the composite nanocrystalline powder components is selected to solve the density of the nanocrystalline composite alloy layer. The powder particle size directly affects the powder transportation and heating conditions and the density of the coating. For materials with high melting point, high density and poor thermal conductivity, the use of finer powders, especially nanopowders, for the same heat source plays a key role in improving the density of the alloy layer. At the same time, it can greatly improve the strength and wear resistance of the nanocrystalline composite alloy layer.

[0015] A slurry-water balanced pipe jacking machine cutter head has a surface coated with a slurry-water balanced pipe jacking machine cutter head surface coating.

[0016] A surface treatment method for a slurry balance pipe jacking machine cutter head comprises the following steps:

[0017] S1. Remove the oxide layer and impurities from the substrate surface to reduce its roughness to less than 0.1μm;

[0018] S2, substrate surface cleaning and sandblasting;

[0019] S3, depositing a zirconium alloy coating on the surface of the substrate treated in step S2;

[0020] S4, depositing a titanium alloy coating on the surface of the substrate treated in step S3;

[0021] S5, depositing a titanium carbide alloy coating on the surface of the substrate treated in step S4;

[0022] S6, depositing a nanocrystalline composite alloy layer on the surface of the substrate treated in step S5, laying composite nanocrystalline powder on the titanium carbide alloy layer, and using a laser cladding process to obtain a nanocrystalline composite alloy layer;

[0023] Preferably, in step S2, the surface cleaning is to use acetone to clean off the oil stains on the surface of the cutter head, and the sandblasting is to use sandblasting, requiring the surface to reach Sa3 level.

[0024] Preferably, in step S3, the process conditions for depositing the zirconium alloy coating are: when the vacuum degree reaches 3×10 -3 ~9×10 -3 When Pa is applied, the heating temperature is 350-500°C, and a zirconium alloy layer is deposited by PVD. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 120-200A, a deposition time of 2-4H, a bias voltage of 200-500V, a duty cycle of 40%-80%, and an argon gas flow rate of 20-200SCCM. The zirconium alloy target is a 99.99% pure zirconium target.

[0025] Preferably, in step S4, the process conditions for depositing the titanium alloy coating are: when the vacuum degree reaches 3×10 -3 ~9×10 -3 Pa, the heating temperature is 350-500°C, and PVD deposition of a titanium alloy layer is carried out. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 80-120A, a deposition time of 1-3H, a bias voltage of 200-500V, a duty cycle of 40%-80%, and an argon gas flow rate of 100-200SCCM. The titanium alloy target is a 99.99% pure titanium target.

[0026] Preferably, in step S5, the process conditions for depositing the titanium carbide alloy coating are: when the vacuum degree reaches 3×10 -3 ~9×10 -3Pa, the heating temperature is 350-500°C, and PVD deposition of a titanium alloy layer is carried out. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 80-120A, a deposition time of 2-6H, a bias voltage of 200-500V, a duty cycle of 40%-80%, an argon flow rate of 100-200SCCM, and a nitrogen flow rate of 300-600SCCM. The titanium alloy target is a 99.99% pure titanium target.

[0027] Preferably, in step S6, the process conditions for depositing the nanocrystalline composite alloy layer are laser cladding using a CO2 laser with a power of 8Kw, a laser power of 2000-4000W, a scanning speed of 6-10mm / s, an overlap rate of 45%, and a laser cladding heat input of 120-150J / mm2.

[0028] In summary, this application includes at least one of the following beneficial technical effects:

[0029] (1) This application uses vacuum PVD coating process and laser cladding technology to form a wear-resistant and high-strength coating on the surface of the cutter head to improve the hardness and wear resistance of the cutter head. The obtained high-wear-resistant and high-strength coating has a hardness of 71-79HRC through testing, which is increased by 1.87-2.08 times.

[0030] (2) The high wear-resistant and high-strength coating obtained in this application uses nano-WC and Al2O3 as the dual cores of the nucleus to obtain a high wear-resistant and high-strength coating, which increases the service life of the cutter head by 3.13-4.94 times and reduces the frequency of shutdown and replacement of the cutter head during the construction of the slurry balance pipe jacking machine.

[0031] (3) This application adopts an innovative coating structure design, which greatly improves the bonding strength between the coating and the substrate, eliminates the residual stress between the coatings, improves the anti-oxidation and anti-adhesion capabilities of the mud-water balance pipe jacking machine cutter head, and the coating is not easy to fall off during use. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Schematic diagram of the surface coating structure of the slurry balance pipe jacking machine cutter head.

[0033] Reference numerals: 1. tool head substrate; 2. zirconium alloy layer; 3. titanium alloy layer; 4. titanium carbide alloy layer; 5. nanocrystalline composite alloy layer. DETAILED DESCRIPTION

[0034] The embodiments of the present application will be described in detail below in conjunction with the examples and preparation examples, but it will be understood by those skilled in the art that the following examples and preparation examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. In the examples and preparation examples, if specific conditions are not specified, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are conventional products that can be purchased commercially if the manufacturer is not specified.

[0035] Example 1

[0036] A surface coating structure of a cutter head of a slurry-water balancing pipe jacking machine comprises, starting from the surface layer of a cutter head substrate, a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer; the thickness of the zirconium alloy layer is 0.5 microns, the thickness of the titanium alloy layer is 1 micron, the thickness of the titanium carbide alloy layer is 5 microns, the thickness of the nanocrystalline composite alloy layer is 10 microns, and the nanocrystalline composite alloy layer is a composite nanocrystalline powder laser cladding layer.

[0037] The composite nanocrystalline powder consists of nano-Al powder, nano-Co powder, nano-Si powder, nano-Mo powder, nano-WC powder and nano-Al2O3 powder in a molar ratio of 0.2:0.3:0.1:0.1:0.3:0.05.

[0038] The powder diameter distribution of the nano-Al powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Co powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Si powder is 30 to 80 nanometers, the powder diameter distribution of the nano-Mo powder is 50 to 100 nanometers, the powder diameter distribution of the nano-WC powder is 50 to 100 nanometers, and the powder diameter distribution of the nano-Al2O3 powder is 40 to 90 nanometers.

[0039] Example 2

[0040] A surface coating structure of a cutter head of a slurry-water balancing pipe jacking machine comprises, starting from the surface layer of a cutter head substrate, a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer; the thickness of the zirconium alloy layer is 2 microns, the thickness of the titanium alloy layer is 0.5 microns, the thickness of the titanium carbide alloy layer is 1 micron, the thickness of the nanocrystalline composite alloy layer is 50 microns, and the nanocrystalline composite alloy layer is a composite nanocrystalline powder laser cladding layer.

[0041] The composite nanocrystalline powder consists of nano-Al powder, nano-Co powder, nano-Si powder, nano-Mo powder, nano-WC powder and nano-Al2O3 powder in a molar ratio of 0.7:1.2:0.5:0.3:1:0.1.

[0042] The powder diameter distribution of the nano-Al powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Co powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Si powder is 30 to 80 nanometers, the powder diameter distribution of the nano-Mo powder is 50 to 100 nanometers, the powder diameter distribution of the nano-WC powder is 50 to 100 nanometers, and the powder diameter distribution of the nano-Al2O3 powder is 40 to 90 nanometers.

[0043] Example 3

[0044] A surface coating structure of a cutter head of a slurry-water balancing pipe jacking machine comprises, starting from the surface layer of a cutter head substrate, a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer; the thickness of the zirconium alloy layer is 1 micron, the thickness of the titanium alloy layer is 0.8 micron, the thickness of the titanium carbide alloy layer is 3 microns, the thickness of the nanocrystalline composite alloy layer is 30 microns, and the nanocrystalline composite alloy layer is a composite nanocrystalline powder laser cladding layer.

[0045] The composite nanocrystalline powder consists of nano-Al powder, nano-Co powder, nano-Si powder, nano-Mo powder, nano-WC powder and nano-Al2O3 powder in a molar ratio of 0.5:0.8:0.3:0.2:0.7:0.0.

[0046] The powder diameter distribution of the nano-Al powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Co powder is 50 to 100 nanometers, the powder diameter distribution of the nano-Si powder is 30 to 80 nanometers, the powder diameter distribution of the nano-Mo powder is 50 to 100 nanometers, the powder diameter distribution of the nano-WC powder is 50 to 100 nanometers, and the powder diameter distribution of the nano-Al2O3 powder is 40 to 90 nanometers.

[0047] Preparation Example 1

[0048] A surface treatment method for a slurry balance pipe jacking machine cutter head comprises the following steps:

[0049] S1. Remove the oxide layer and impurities from the substrate surface to reduce its roughness to less than 0.1μm;

[0050] S2. Clean the surface of the substrate using acetone to remove the oil stains on the surface of the cutter head, and perform sandblasting on the surface to achieve Sa3 level.

[0051] S3, depositing a zirconium alloy coating on the surface of the substrate treated in step S2, the process conditions are: when the vacuum degree reaches 3×10 -3Pa, the heating temperature is 350°C, and PVD deposition of the zirconium alloy layer is carried out. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 120A, a deposition time of 2H, a bias voltage of 500V, a duty cycle of 40%, an argon gas flow rate of 20SCCM, and the zirconium alloy target is a 99.99% pure zirconium target.

[0052] S4, depositing a titanium alloy coating on the surface of the substrate treated in step S3, the process conditions are: when the vacuum degree reaches 3×10 -3 Pa, the heating temperature is 350 ° C, and a titanium alloy layer is deposited by PVD. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 80A, a deposition time of 1H, a bias voltage of 500V, a duty cycle of 40%, an argon gas flow rate of 100SCCM, and the titanium alloy target is a 99.99% pure titanium target;

[0053] S5, depositing a titanium carbide alloy coating on the surface of the substrate treated in step S4, the process conditions are: when the vacuum degree reaches 3×10 -3 Pa, the heating temperature is 350 ° C, and a PVD titanium alloy layer is deposited. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 80A, a deposition time of 2H, a bias voltage of 500V, a duty cycle of 40%, an argon flow rate of 100SCCM, and a nitrogen flow rate of 300SCCM. The titanium alloy target is a 99.99% pure titanium target;

[0054] S6, depositing a nanocrystalline composite alloy layer on the surface of the substrate treated in step S5, and spreading composite nanocrystalline powder on the titanium alloy layer coating, wherein the composite nanocrystalline powder is composed of 54g of nano-Al powder, 177g of nano-Co powder, 28g of nano-Si powder, 96g of nano-Mo powder, 588g of nano-WC powder and 56g of nano-Al2O3 powder mixed and stirred evenly, the average powder diameter of the nano-Al powder is 50-100 nanometers, the average powder diameter of the nano-Co powder is 50-100 nanometers, and the average powder diameter of the nano-Si powder is 50-100 nanometers. The average diameter of the powder is 30-80 nanometers, the average diameter of the nano Mo powder is 50-100 nanometers, the average diameter of the nano WC powder is 50-100 nanometers, and the average diameter of the nano Al2O3 powder is 40-90 nanometers. The laser cladding process is used to form the film. The process conditions are: using a CO2 laser with a power of 8Kw for laser cladding, a laser power of 2000W, a scanning speed of 6mm / s, an overlap rate of 45%, and a laser cladding heat input of 120J / mm 2 , obtaining a nanocrystalline composite alloy layer.

[0055] By the above method, the surface coating structure of the cutter head of the slurry balance pipe jacking machine is obtained, which is a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer starting from the surface layer of the cutter head surface substrate; the thickness of the zirconium alloy layer is 0.5 microns, the thickness of the titanium alloy layer is 0.5 microns, the thickness of the titanium carbide alloy layer is 1 micron, and the thickness of the nanocrystalline composite alloy layer is 10 microns.

[0056] Preparation Example 2

[0057] A surface treatment method for a slurry balance pipe jacking machine cutter head comprises the following steps:

[0058] S1. Remove the oxide layer and impurities from the substrate surface to reduce its roughness to less than 0.1μm;

[0059] S2. Clean the surface of the substrate using acetone to remove the oil stains on the surface of the cutter head, and perform sandblasting on the surface to achieve Sa3 level.

[0060] S3, depositing a zirconium alloy coating on the surface of the substrate treated in step S2, the process conditions are: when the vacuum degree reaches 9×10 -3 a, the heating temperature is 500°C, and the zirconium alloy layer is deposited by PVD. The process conditions for depositing the metal layer can be multi-arc ion plating, with a multi-arc power supply current of 200A, a deposition time of 4H, a bias voltage of 200V, a duty cycle of 80%, and an argon gas flow rate of 200SCCM. The zirconium alloy target is a 99.99% pure zirconium target.

[0061] S4, depositing a titanium alloy coating on the surface of the substrate treated in step S3, the process conditions are: when the vacuum degree reaches 9×10 -3 Pa, the heating temperature is 500 ° C, and a PVD titanium alloy layer is deposited. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 120A, a deposition time of 3H, a bias voltage of 200V, a duty cycle of 80%, an argon gas flow rate of 200SCCM, and the titanium alloy target is a 99.99% pure titanium target;

[0062] S5, depositing a titanium carbide alloy coating on the surface of the substrate treated in step S4, the process conditions are: when the vacuum degree reaches 9×10 -3 Pa, the heating temperature is 500 ° C, and a PVD titanium alloy layer is deposited. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 120A, a deposition time of 6H, a bias voltage of 200V, a duty cycle of 80%, an argon flow rate of 200SCCM, and a nitrogen flow rate of 600SCCM. The titanium alloy target is a 99.99% pure titanium target;

[0063] S6, depositing a nanocrystalline composite alloy layer on the surface of the substrate treated in step S5, and spreading composite nanocrystalline powder on the titanium alloy layer coating, wherein the composite nanocrystalline powder is composed of 189g of nano-Al powder, 708g of nano-Co powder, 140g of nano-Si powder, 288g of nano-Mo powder, 1960g of nano-WC powder and 112g of nano-Al2O3 powder mixed and stirred evenly, the average powder diameter of the nano-Al powder is 50-100 nanometers, the average powder diameter of the nano-Co powder is 50-100 nanometers, and the average powder diameter of the nano-Si powder is 112g. The average diameter of the nano-Mo powder is 30 to 80 nanometers, the average diameter of the nano-WC powder is 50 to 100 nanometers, and the average diameter of the nano-Al2O3 powder is 40 to 90 nanometers. The film is formed by laser cladding process, and the process conditions are laser cladding with a CO2 laser power of 8Kw, a laser power of 4000W, a scanning speed of 10mm / s, an overlap rate of 45%, and a laser cladding heat input of 150J / mm2 to obtain a nanocrystalline composite alloy layer.

[0064] By the above method, the surface coating structure of the cutter head of the composite mud-water balanced pipe jacking machine is obtained, which is a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer starting from the surface layer of the cutter head surface substrate; the thickness of the zirconium alloy layer is 2 microns, the thickness of the titanium alloy layer is 1 micron, the thickness of the titanium carbide alloy layer is 5 microns, and the thickness of the nanocrystalline composite alloy layer is 50 microns.

[0065] Preparation Example 3

[0066] A surface treatment method for a slurry balance pipe jacking machine cutter head comprises the following steps:

[0067] S1. Remove the oxide layer and impurities from the substrate surface to reduce its roughness to less than 0.1μm;

[0068] S2. Clean the surface of the substrate using acetone to remove the oil stains on the surface of the cutter head, and perform sandblasting on the surface to achieve Sa3 level.

[0069] S3, depositing a zirconium alloy coating on the surface of the substrate treated in step S2, the process conditions are: when the vacuum degree reaches 6×10 -3 Pa, the heating temperature is 400°C, and PVD deposition of the zirconium alloy layer is carried out. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 150A, a deposition time of 3H, a bias voltage of 400V, a duty cycle of 60%, an argon gas flow rate of 100SCCM, and the zirconium alloy target is a 99.99% pure zirconium target.

[0070] S4, depositing a titanium alloy coating on the surface of the substrate treated in step S3, the process conditions are: when the vacuum degree reaches 6×10 -3Pa, the heating temperature is 400 ° C, and a titanium alloy layer is deposited by PVD. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 100A, a deposition time of 2H, a bias voltage of 300V, a duty cycle of 60%, an argon gas flow rate of 150SCCM, and the titanium alloy target is a 99.99% pure titanium target;

[0071] S5, depositing a titanium carbide alloy coating on the surface of the substrate treated in step S4, the process conditions are: when the vacuum degree reaches 6×10 -3 Pa, the heating temperature is 400 ° C, and a PVD titanium alloy layer is deposited. The process conditions for depositing the metal layer may be multi-arc ion plating, a multi-arc power supply current of 100A, a deposition time of 4H, a bias voltage of 400V, a duty cycle of 50%, an argon flow rate of 180SCCM, and a nitrogen flow rate of 500SCCM. The titanium alloy target is a 99.99% pure titanium target.

[0072] S6. Depositing a nanocrystalline composite alloy layer on the surface of the substrate treated in step S5, and spreading composite nanocrystalline powder on the titanium alloy layer coating, wherein the composite nanocrystalline powder is composed of 130g of nano-Al powder, 650g of nano-Co powder, 100g of nano-Si powder, 200g of nano-Mo powder, 1200g of nano-WC powder and 80g of nano-Al2O3 powder mixed and stirred evenly, wherein the average powder diameter of the nano-Al powder is 50-100 nanometers, the average powder diameter of the nano-Co powder is 50-100 nanometers, and the average powder diameter of the nano-S powder is 80g. The average powder diameter of i powder is 30-80 nanometers, the average powder diameter of nano Mo powder is 50-100 nanometers, the average powder diameter of nano WC powder is 50-100 nanometers, and the average powder diameter of nano Al2O3 powder is 40-90 nanometers. The film is formed by laser cladding process. The process conditions are: laser cladding with a CO2 laser with a power of 8Kw, a laser power of 3000W, a scanning speed of 80mm / s, an overlap rate of 45%, and a laser cladding heat input of 135J / mm 2 , obtaining a nanocrystalline composite alloy layer.

[0073] By the above method, the surface coating structure of the cutter head of the slurry balance pipe jacking machine is obtained, which is a zirconium alloy layer, a titanium alloy layer, a titanium carbide alloy layer and a nanocrystalline composite alloy layer starting from the surface layer of the cutter head surface substrate; the thickness of the zirconium alloy layer is 1.3 microns, the thickness of the titanium alloy layer is 0.85 microns, the thickness of the titanium carbide alloy layer is 3.3 microns, and the thickness of the nanocrystalline composite alloy layer is 38 microns.

[0074] Comparative Example 1

[0075] The same as Preparation Example 3, except that the amount of nano WC powder added is 500g.

[0076] Comparative Example 2

[0077] The same as Preparation Example 3, except that the amount of nano WC powder added is 2300 g.

[0078] Comparative Example 3

[0079] The same as Preparation Example 3, except that the amount of nano-Al2O3 powder added is 40g.

[0080] Comparative Example 4

[0081] The same as Preparation Example 3, except that the amount of nano-Al2O3 powder added is 120g.

[0082] Performance Testing

[0083] The surface hardness and service life tests of the cutter heads of Preparation Examples 1-3 and Comparative Examples 1-4, as well as the control example, were not performed, and the data are shown in Table 1.

[0084] The hardness test was conducted as follows: the test sample was ground and polished, cleaned with anhydrous ethanol, and dried. The hardness was measured using a DHV1000Z digital micro-Vickers hardness tester. Ten points were selected on the test object, and three sets of indentation values ​​were measured using the hardness tester. The average hardness value was calculated. The results are shown in Table 1.

[0085] The service life is the actual time when the tool is severely worn and the outer surface of the tool body is seriously damaged, and the wear exceeds 10mm.

[0086] Table 1

[0087] Hardness / HRC Service life / hour Preparation Example 1 71 11450 Preparation Example 2 75 14633 Preparation Example 3 79 18050 Comparative Example 1 62 8524 Comparative Example 2 57 7208 Comparative Example 3 63 8350 Comparative Example 4 55 7309 Control Example 38 3656

[0088] As can be seen from Table 1, the obtained high wear-resistant and high-strength coating has a hardness of 71-79HRC through testing, which is improved by 1.87-2.08 times, and the service life is increased by 3.13-4.94 times.

[0089] By comparing Preparation Example 3 with Comparative Examples 1 and 2, it can be concluded that when the amount of nano WC powder added is 500g, its hardness decreases significantly from 79HRC to 62HRC, and its service life is greatly reduced. When the amount of nano WC powder added is 2300g, its hardness decreases significantly from 79HRC to 57HRC, and its service life is greatly reduced.

[0090] By comparing Preparation Example 3 with Comparative Examples 3 and 4, it can be concluded that when the amount of nano-Al2O3 powder added is 40g, its hardness drops significantly from 79HRC to 63HRC, and its service life is greatly reduced. When the amount of nano-Al2O3 powder added is 120g, its hardness drops significantly from 79HRC to 55HRC, and its service life is greatly reduced.

[0091] The above are all preferred embodiments and preparation examples of the present application, and are not intended to limit the scope of protection of the present application. The above are only preferred implementation methods of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A surface coating structure of a cutter head of a slurry-water balanced pipe jacking machine, characterized in that: Starting from the surface of the cutter head substrate, there are zirconium metal layer, titanium metal layer, titanium nitride layer and nanocrystalline composite alloy layer in order; the zirconium metal layer is an anti-oxidation layer with a thickness of 0.5 to 2 microns, the titanium metal layer is a bonding enhancement layer with a thickness of 0.5 to 1 micron, the titanium nitride layer is a wear-resistant transition layer with a thickness of 1 to 5 microns, the nanocrystalline composite alloy layer is a surface wear-resistant layer with a thickness of 10 to 50 microns, and the nanocrystalline composite alloy layer is a composite nanocrystalline powder laser cladding layer; The composite nanocrystalline powder is composed of nano-Al powder, nano-Co powder, nano-Si powder, nano-Mo powder, nano-WC powder, and nano-Al2O3 powder in a molar ratio of 0.2-0.7: 0.3-1.2: 0.1-0.5: 0.1-0.3: 0.3-1: 0.05-0.1; The method for preparing the surface coating structure of the cutter head of the slurry-water balanced pipe jacking machine comprises the following steps: S1: Clean the surface of the tool head substrate to remove the oxide layer and impurities, making its surface roughness Ra ≤ 0.1μm; S2: The cleaned substrate is sandblasted, and the surface cleanliness reaches Sa3 level after sandblasting; S3: Deposit a zirconium metal layer on the substrate surface. The deposition process is multi-arc ion plating. The purity of the zirconium target is 99.99%. When the vacuum degree reaches 3×10 -3 ~9×10 -3 When the pressure is 1000 Pa, the heating temperature is 350-500°C, and the zirconium metal layer is deposited. The process parameters are: multi-arc power supply current 120-200A, deposition time 2-4H, bias voltage 200-500V, duty cycle 40%-80%, and argon gas flow rate 20-200SCCM; S4: Deposit a titanium metal layer on the zirconium metal layer. The deposition process is multi-arc ion plating. The purity of the titanium target is 99.99%. When the vacuum degree reaches 3×10 -3 ~9×10 -3 When Pa, the heating temperature is 350-500 ° C, and the titanium metal layer is deposited. The process parameters are: multi-arc power supply current 80-120A, deposition time 1-3H, bias voltage 200-500V, duty cycle 40%-80%, and argon gas flow rate 100-200SCCM; S5: Titanium nitride layer is deposited on the titanium metal layer. The deposition process is multi-arc ion plating. The purity of the titanium alloy target is 99.99%. When the vacuum degree reaches 3×10 -3 ~9×10 -3 When Pa, the heating temperature is 350-500 ° C, and the titanium nitride layer is deposited. The process parameters are: multi-arc power supply current 80-120A, deposition time 2-6H, bias voltage 200-500V, duty cycle 40%-80%, argon flow rate 20-80SCCM, nitrogen flow rate 300-600SCCM; S6: Laser cladding of a nanocrystalline composite alloy layer on the titanium nitride layer. The laser cladding powder is a composite nanocrystalline powder. The laser cladding is performed using a CO2 laser with a power of 8kW, a laser power of 2000-4000W, a scanning speed of 6-10mm / s, an overlap rate of 45%, and a laser cladding heat input of 120-150J / mm 2 .

2. The surface coating structure of the cutter head of a slurry-water balanced pipe jacking machine according to claim 1 is characterized in that: The powder diameter of the nano-Al powder is 50 to 100 nanometers, the powder diameter of the nano-Co powder is 50 to 100 nanometers, the powder diameter of the nano-Si powder is 30 to 80 nanometers, the powder diameter of the nano-Mo powder is 50 to 100 nanometers, the powder diameter of the nano-WC powder is 50 to 100 nanometers, and the powder diameter of the nano-Al2O3 powder is 40 to 90 nanometers.

3. A slurry balance pipe jacking machine cutter head, characterized in that: The surface of the cutter head is coated with a surface coating structure of a cutter head of a slurry-water balanced pipe jacking machine as described in any one of claims 1-2.

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