Shield tunneling machine hob cutter ring surface strengthening method

Abstract

The invention relates to the technical field of engineering machinery manufacturing, and particularly discloses a surface strengthening method for a hob cutter ring of a shield tunneling machine. Ni60 alloy powder, ceramic powder and auxiliaries are used for preparing mixed powder, and the mixed powder is used for preparing the strengthening layer. The wear resistance of the strengthening layer is remarkably improved under the cooperation of the Ni60 alloy, the ceramic powder and the lanthanum oxide, so that the cutter ring can fully bear the effects of high stress impact, severe friction and periodic load, is particularly suitable for construction operation in an area with higher rock stratum strength, and can effectively reduce the maintenance and replacement frequency of the cutter ring.

Description

Technical Field

[0001] The present application relates to the technical field of engineering machinery manufacturing, and more specifically, to a method for strengthening the surface of a shield machine cutter ring. Background Art

[0002] The shield machine is the core equipment of tunnel excavation projects. It has been widely used in my country's tunnel development due to its advantages such as fast excavation speed, high safety factor, high degree of automation, low construction labor intensity, little interference with the surrounding environment, and no influence from climatic conditions. The cutter of the shield machine is a key component directly involved in rock and soil crushing, and the cutter ring is the working surface where the cutter is in direct contact with the rock and soil. Its performance directly affects the excavation efficiency, tool life and project cost of the shield machine. In order to ensure the normal operation of the shield machine, it is generally necessary to improve the comprehensive performance of the cutter ring through surface strengthening technology when producing the cutter ring.

[0003] At present, the surface modification technology mainly used to strengthen the cutter ring of the shield machine includes cladding, laser cladding, carburizing treatment and other methods. The cladding technology mainly improves the hardness by cladding a wear-resistant alloy layer (such as high-chromium cast iron, cobalt-based alloy) on the surface of the cutter ring; laser cladding is to use a high-energy laser beam to clad ceramic-reinforced metal-based composite materials to form a dense reinforcement layer on the surface of the cutter ring; carburizing treatment is to increase the carbon content of the cutter ring surface through a high-temperature carburizing process, thereby increasing the hardness of the cutter ring.

[0004] Regarding the above-mentioned related technologies, the inventor believes that although the above-mentioned methods have improved the performance of the cutter ring to a certain extent, the improvement of wear resistance is still relatively limited. When the shield machine is working in an area with greater depth and higher rock strength, the cutter ring needs to withstand high stress impact, severe friction and periodic load for a long time. These factors easily cause the cutter ring to wear, resulting in the need for frequent maintenance and replacement of the cutter ring, which greatly delays the progress of tunnel construction. Summary of the invention

[0005] In the related art, although the surface strengthening technology improves the comprehensive performance of the cutter ring, when the shield machine is operating in an area with greater depth and higher rock strength, the cutter ring will still wear out, resulting in the need for frequent maintenance and replacement of the cutter ring, which greatly delays the progress of tunnel construction. In order to improve this defect, the present application provides a method for strengthening the surface of the cutter ring of a shield machine.

[0006] The present application provides a method for strengthening the surface of a shield machine cutter ring, which adopts the following technical solution: A method for strengthening the surface of a shield machine cutter ring comprises the following steps: (1) grinding and cleaning the surface of the cutter ring, and drying for later use; mixing ceramic powder and alloy powder in a weight ratio of (0.24-0.27):1 to obtain a base material, mixing the base material and the auxiliary agent, and then ball milling to obtain a mixed powder, which is dried for later use; the alloy powder includes Ni60 alloy powder, the auxiliary agent includes lanthanum oxide, and the ceramic powder includes titanium carbide powder and tungsten carbide powder; (2) The mixed powder is coated on the surface of the cutter ring and then preheated. The mixed powder is processed using a laser cladding device under argon protection to form a strengthening layer on the surface of the cutter ring, thereby completing the surface strengthening of the cutter ring of the shield machine.

[0007] By adopting the above technical scheme, the present application selects a ceramic powder composed of titanium carbide powder and tungsten carbide powder, obtains a base material by mixing the ceramic powder with the alloy powder, and then adds additives including lanthanum oxide to the base material to obtain a mixed powder. In the strengthening layer formed by the mixed powder, the Ni60 alloy is used as a bonding phase, which itself has multiple strengthening mechanisms such as austenite solid solution strengthening, precipitation strengthening, and grain boundary strengthening. The addition of titanium carbide powder increases the nucleation rate of uneven nucleation, effectively inhibits the growth of dendrites, and thus refines the organization; tungsten carbide powder can cooperate with titanium carbide powder to hinder the growth of Ni grains, so that Ni grains form ultrafine eutectic structure. Lanthanum oxide can promote microstructure refinement, increase the uniformity and density of the microstructure, and cooperate with ceramic powder to promote fine grain strengthening. At the same time, the ceramic powder also plays a role in dispersion strengthening as a hard phase, and a part of the titanium carbide powder will decompose into Ti and C during the cladding process and re-precipitate to form new titanium carbide powder in situ. These newly generated titanium carbide powders are dispersed in the strengthening layer, further enhancing the dispersion strengthening effect of the ceramic powder. With the synergistic combination of Ni60 alloy, ceramic powder and lanthanum oxide, the wear resistance of the strengthening layer has been significantly improved, so the cutter ring can fully withstand high stress impact, severe friction and periodic loads, which is particularly suitable for construction operations in areas with high rock strength, and can effectively reduce the maintenance and replacement frequency of the cutter ring.

[0008] Preferably, the amount of lanthanum oxide used is 1.3-1.5% by weight of the base material.

[0009] By adopting the above technical solution, the present application optimizes the dosage of lanthanum oxide. Within the above dosage range, lanthanum oxide and ceramic powder can fully promote fine grain strengthening, thereby enhancing the wear resistance of the strengthening layer and extending the service life of the knife ring.

[0010] Preferably, the auxiliary agent further comprises titanium dioxide nanotubes, and the titanium dioxide nanotubes are prepared according to the following method: Titanium dioxide powder and sodium hydroxide solution are mixed and sealed in an autoclave with a polytetrafluoroethylene liner. After heating, the mixture is kept warm at 115-165°C for reaction. After the heat preservation is completed, the autoclave is naturally cooled. The product is washed with hydrochloric acid, then ultrasonically treated in hydrochloric acid, and finally washed with distilled water. Titanium dioxide nanotubes are obtained after drying.

[0011] By adopting the above technical solution, the present application uses titanium dioxide powder as a titanium source and prepares titanium dioxide nanotubes by hydrothermal synthesis. The structure of titanium dioxide nanotubes is conducive to the transmission of stress, and can increase the content of tough phase in the composite coating, and can inhibit the excessive growth of hard phase, thereby obtaining a finer hard phase. These fine hard phases are dispersed in the tough phase, making the structure of the cladding layer more refined and uniform, which is conducive to improving the wear resistance of the strengthening layer.

[0012] Preferably, in the method for preparing the titanium dioxide nanotubes, the heat preservation reaction is carried out at 135-165°C.

[0013] By adopting the above technical solution, the present application optimizes the temperature range of the hydrothermal reaction, which helps to increase the length of the titanium dioxide nanotubes, improves the stress transfer effect in the strengthening layer, and is beneficial to improving the wear resistance of the strengthening layer.

[0014] Preferably, the auxiliary agent further comprises alumina powder, and the crystal form of the alumina powder is α-alumina.

[0015] By adopting the above technical solution, α-Al2O3 is a stable close-packed hexagonal structure, which can inhibit the formation of coarse brittle hard phases in the strengthening layer, promote grain refinement, and achieve fine grain strengthening. The Al2Cr4C2 fine particle reinforcement phase formed by the combination of α-Al2O3 and Ni60 alloy is evenly dispersed in the organization, not easy to fall off, and can play a role in dispersion strengthening. Under the synergistic effect of fine grain strengthening and dispersion strengthening, the addition of α-Al2O3 can effectively improve the wear resistance of the strengthening layer.

[0016] Preferably, the amount of the alumina powder is 0.42-0.48% by weight of the base material.

[0017] By adopting the above technical solution, the present application optimizes the dosage of alumina powder, which helps to improve the wear resistance of the strengthening layer.

[0018] Preferably, the weight ratio of the tungsten carbide powder to the titanium carbide powder is (2.28-2.33):1.

[0019] By adopting the above technical solution, the present application optimizes the weight ratio of tungsten carbide powder and titanium carbide powder, which is beneficial to improving the dispersion strengthening and fine grain strengthening effects of the ceramic powder and improving the wear resistance of the strengthening layer.

[0020] Preferably, the auxiliary agent also includes rare earth ferrosilicon.

[0021] By adopting the above technical solution, the rare earth elements in rare earth ferrosilicon can increase the toughness of the spray-melted layer matrix and improve the ability of the matrix to cover tungsten carbide particles. The addition of rare earth ferrosilicon also changes the tungsten carbide particles from the original sharp angle to the obtuse angle, so that the interface bonding with the matrix phase is more firm. When conducting abrasive wear tests, the ability of tungsten carbide to resist peeling is enhanced, which is conducive to improving the wear resistance of the strengthening layer.

[0022] Preferably, the auxiliary agent also includes a lubricant, and the lubricant includes molybdenum sulfide and calcium fluoride.

[0023] By adopting the above technical solution, the lubricant has a certain plasticity. Under the high temperature generated during friction, the lubricant will be squeezed out to form a transfer film and spread on the surface of the strengthening layer to form a mixed transfer film of FeMo2S4, CaMoO4, and CaF2, thereby avoiding direct contact between the strengthening layer and the wear part and improving the wear resistance of the strengthening layer.

[0024] Preferably, the amount of the lubricant is 6.5-6.8% of the total weight of the base material.

[0025] By adopting the above technical solution, the present application optimizes the amount of lubricant, which is beneficial to the smooth formation of the mixed transfer film and improves the wear resistance of the strengthening layer.

[0026] In summary, this application has the following beneficial effects: 1. This application uses Ni60 alloy powder, ceramic powder and additives to prepare a mixed powder, and uses the mixed powder to prepare a strengthening layer. With the synergistic combination of Ni60 alloy, ceramic powder and lanthanum oxide, the wear resistance of the strengthening layer is significantly improved, so the cutter ring can fully withstand high stress impact, severe friction and periodic loads, and is particularly suitable for construction operations in areas with high rock strength, and can effectively reduce the maintenance and replacement frequency of the cutter ring.

[0027] 2. The present application prepares titanium dioxide nanotubes and uses them as additives. The structure of titanium dioxide nanotubes is conducive to the transmission of stress, and can make the structure of the cladding layer more refined and uniform, which is conducive to improving the wear resistance of the strengthening layer. 3. The present application preferably uses lubricants as auxiliary agents. Lubricants have certain plasticity. Under the high temperature generated during friction, the lubricants will be squeezed out to form a transfer film and spread on the surface of the strengthening layer to form a mixed transfer film, thereby avoiding direct contact between the strengthening layer and the wear part and improving the wear resistance of the strengthening layer. DETAILED DESCRIPTION

[0028] The present application is further described in detail below in conjunction with embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0029] Preparation example of titanium dioxide nanotubes The following is an explanation using Preparation Example 1.

[0030] Preparation Example 1 In this preparation example, titanium dioxide nanotubes were prepared according to the following method: Titanium dioxide powder with an average particle size of 20 nm and a sodium hydroxide solution with a concentration of 10 mol / L were mixed in a ratio of 1 g:0.35 L, and then sealed in an autoclave with a polytetrafluoroethylene liner. After heating, the mixture was kept warm at 115°C for 24 hours. After the heat preservation, the autoclave was naturally cooled, and the product was washed with 1 mol / L hydrochloric acid, and then ultrasonically treated in 1 mol / L hydrochloric acid. After 2 hours, the product was washed with distilled water and dried to obtain titanium dioxide nanotubes.

[0031] As shown in Table 1, the difference between Preparation Examples 1-5 is that, in the method for preparing titanium dioxide nanotubes, the insulation reaction is carried out at different temperatures.

[0032] Table 1 Reaction temperature sample Reaction temperature / ℃ Preparation Example 1 115 Preparation Example 2 125 Preparation Example 3 135 Preparation Example 4 145 Preparation Example 5 155 Example

[0033] Examples 1-5 The following description is given by taking Example 1 as an example.

[0034] Example 1 In this embodiment, the alloy powder is Ni60 alloy powder, and the average particle size of the alloy powder is 75μm; the ceramic powder is a mixture of titanium carbide powder and tungsten carbide powder in a weight ratio of 2.2:1, and the average particle size of the ceramic powder is 3μm; the auxiliary agent is lanthanum oxide, and the amount of lanthanum oxide used is 1% of the weight of the base material.

[0035] This embodiment provides a preparation method for a shield machine cutter ring surface strengthening method, comprising the following steps: (1) Grinding the surface of the knife ring with sandpaper until the surface of the knife ring presents a metallic luster, then ultrasonically cleaning the knife ring in anhydrous ethanol for 10 minutes, and drying for later use; mixing ceramic powder and alloy powder in a weight ratio of 0.24:1 to obtain a base material, mixing the base material and the additive, and putting them into a planetary ball mill, ball milling for 6 hours at a ball-to-material ratio of 10:1 to obtain a mixed powder, and then drying at 100° C. for later use; (2) The mixed powder is coated on the surface of the cutter ring to form a pre-coating layer with a thickness of 1.5 mm, and then preheated at 200°C. Subsequently, the mixed powder is processed using a laser cladding device under argon protection to form a strengthening layer on the surface of the cutter ring, thereby completing the surface strengthening of the cutter ring of the shield machine. In this step, the laser cladding parameters are as follows: defocus 40 mm, scanning speed 6 mm / s, and laser output power 2 kW.

[0036] As shown in Table 2, the difference between Examples 1-5 mainly lies in the different weight ratios of the ceramic powder and the alloy powder.

[0037] Table 2 Weight ratio of ceramic powder and alloy powder sample Example 1 Example 2 Example 3 Example 4 Example 5 Ceramic powder: Alloy powder 0.24:1 0.25:1 0.255:1 0.26:1 0.27:1 Example 6 The difference between this embodiment and embodiment 5 is that the amount of lanthanum oxide used is 1.3% by weight of the base material. Example 7 The difference between this embodiment and embodiment 5 is that the amount of lanthanum oxide used is 1.4% by weight of the base material. Example 8 The difference between this embodiment and embodiment 5 is that the amount of lanthanum oxide used is 1.5% by weight of the base material. Example 9 The difference between this embodiment and embodiment 8 is that the auxiliary agent further comprises titanium dioxide nanotubes, and the titanium dioxide nanotubes are prepared according to the method of preparation example 1, and the amount of titanium dioxide nanotubes used is 0.4% of the weight of the base material.

[0038] Example 10 The difference between this embodiment and embodiment 9 is that the titanium dioxide nanotubes are prepared according to the method of preparation example 2.

[0039] Embodiment 11 The difference between this embodiment and embodiment 9 is that the titanium dioxide nanotubes are prepared according to the method of preparation example 3.

[0040] Example 12 The difference between this embodiment and embodiment 9 is that the titanium dioxide nanotubes are prepared according to the method of preparation example 4.

[0041] Embodiment 13 The difference between this embodiment and embodiment 9 is that the titanium dioxide nanotubes are prepared according to the method of preparation example 5.

[0042] Embodiment 14 The difference between this embodiment and embodiment 13 is that the auxiliary agent further includes alumina powder, the average particle size of the alumina powder is 25 μm, the crystal form of the alumina powder is α-alumina, and the amount of the alumina powder is 0.35% of the weight of the base material.

[0043] Embodiment 15 The difference between this embodiment and embodiment 14 is that the amount of alumina powder used is 0.42% of the weight of the base material.

[0044] Example 16 The difference between this embodiment and embodiment 14 is that the amount of alumina powder used is 0.45% of the weight of the base material.

[0045] Embodiment 17 The difference between this embodiment and embodiment 14 is that the amount of alumina powder used is 0.48% of the weight of the base material.

[0046] Embodiment 18 The difference between this embodiment and Embodiment 17 is that the weight ratio of tungsten carbide powder to titanium carbide powder is 2.28:1.

[0047] Embodiment 19 The difference between this embodiment and Embodiment 17 is that the weight ratio of tungsten carbide powder to titanium carbide powder is 2.3:1.

[0048] Embodiment 20 The difference between this embodiment and Embodiment 17 is that the weight ratio of tungsten carbide powder to titanium carbide powder is 2.33:1.

[0049] Embodiment 21 The difference between this embodiment and embodiment 20 is that the auxiliary agent further includes rare earth ferrosilicon, the average particle size of the rare earth ferrosilicon is 40 μm, and the amount of rare earth ferrosilicon used is 0.9% of the total weight of the base material.

[0050] Embodiment 22 The difference between this embodiment and Embodiment 21 is that the auxiliary agent also includes a lubricant, and the lubricant is a mixture of molybdenum sulfide and calcium fluoride in a weight ratio of 1:1, and the amount of the lubricant is 3.5% of the total weight of the base material.

[0051] Embodiment 23 The difference between this embodiment and embodiment 22 is that the amount of lubricant used is 6.5% of the total weight of the base material.

[0052] Embodiment 24 The difference between this embodiment and embodiment 22 is that the amount of lubricant used is 6.7% of the total weight of the base material.

[0053] Embodiment 25 The difference between this embodiment and embodiment 22 is that the amount of lubricant used is 6.8% of the total weight of the base material.

[0054] Comparative Example Comparative Example 1 The difference between this comparative example and Example 1 is that the components of the mixed powder do not include ceramic powder and additives.

[0055] Comparative Example 2 The difference between this comparative example and Example 1 is that the components of the mixed powder do not include ceramic powder.

[0056] Comparative Example 3 The difference between this comparative example and Example 1 is that the components of the mixed powder do not include an auxiliary agent.

[0057] Comparative Example 4 The difference between this comparative example and Example 1 is that the titanium carbide powder is replaced with the same weight of tungsten carbide powder.

[0058] Comparative Example 5 The difference between this comparative example and Example 1 is that the tungsten carbide powder is replaced with the same weight of titanium carbide powder.

[0059] Performance testing methods The reciprocating friction and wear test was carried out using an RTECMFT-50 friction and wear tester. The test parameters were as follows: test force 50N, reciprocating stroke 10mm, wear time 1800s, and the wear part was a silicon nitride ceramic ball. An analytical balance with an accuracy of 0.0001g was used to measure the mass of the sample before and after wear, and the wear weight loss was calculated. Three parallel tests were set up for each group, and the average wear weight loss measured by the three parallel tests was taken as the measured value of the wear weight loss. Taking the measured value of the wear weight loss of comparative example 1 as a benchmark, the ratio between the measured value of the wear weight loss of each embodiment and comparative example and the measured value of the wear weight loss of comparative example 1 was calculated, and the ratio was recorded as the relative weight loss rate. The results are shown in Table 3.

[0060] Table 3 Relative weight loss rate It can be seen from Examples 1-5 and Comparative Example 1 and Table 3 that the relative weight loss rates measured in Examples 1-5 are relatively low. This is because the ceramic powder and lanthanum oxide synergistically promote the refinement of the microstructure and achieve fine grain strengthening. At the same time, the ceramic powder also has a good dispersion strengthening effect. Coupled with the Ni60 alloy's own original austenite solid solution strengthening, precipitation strengthening, grain boundary strengthening and other strengthening mechanisms, the wear resistance of the strengthening layer is significantly improved. Therefore, the knife ring can fully withstand high stress impact, severe friction and periodic loads, and is particularly suitable for construction operations in areas with high rock strength, and can effectively reduce the maintenance and replacement frequency of the knife ring.

[0061] Combining Example 1 and Comparative Example 2 and Table 3, it can be seen that the relative weight loss rate measured in Example 1 is significantly lower. This is because Comparative Example 2 lacks ceramic powder and cannot effectively improve the wear resistance of the strengthening layer through fine grain strengthening and dispersion strengthening, resulting in more wear during the test.

[0062] Combining Example 1 and Comparative Example 3 and Table 3, it can be seen that the relative weight loss rate measured in Example 1 is lower. This is because Comparative Example 3 lacks lanthanum oxide, which affects the degree of refinement of the microstructure and cannot fully realize the fine grain strengthening effect, resulting in more wear during the test.

[0063] Combining Example 1 and Comparative Examples 4-5 and Table 3, it can be seen that the relative weight loss rate measured in Example 1 is lower. This is because Comparative Example 4 lacks titanium carbide powder, and Comparative Example 5 lacks tungsten carbide powder. The two ceramic powders cannot be coordinated, and the fine grain strengthening effect and dispersion strengthening effect cannot be fully realized, resulting in more wear during the test.

[0064] Combining Example 5 with Examples 6-8 and Table 3, it can be seen that the relative weight loss rates measured in Examples 6-8 are relatively low, indicating that when the amount of lanthanum oxide used is 1.3-1.5% of the weight of the base material, the wear resistance of the strengthening layer can be effectively improved.

[0065] Combining Example 8, Examples 9-13 and Table 3, it can be seen that the relative weight loss rate measured in Examples 9-13 is relatively low. This is because the structure of the titanium dioxide nanotubes is conducive to the transfer of stress, and can increase the content of the tough phase in the composite coating, and can inhibit the excessive growth of the hard phase, thereby obtaining a finer hard phase. These fine hard phases are dispersed in the tough phase, making the structure of the cladding layer more refined and uniform, which is beneficial to improving the wear resistance of the strengthening layer. Moreover, when the titanium dioxide nanotubes are prepared at 135-165°C, the growth of the titanium dioxide nanotubes is more thorough, thereby improving the stress transfer effect in the strengthening layer, which is beneficial to fully improve the wear resistance of the strengthening layer.

[0066] Combining Example 13, Examples 14-17 and Table 3, it can be seen that the relative weight loss rate measured in Examples 14-17 is relatively low. This is because α-Al2O3 is a stable close-packed hexagonal structure, which can inhibit the formation of coarse brittle hard phases in the strengthening layer, promote grain refinement, and achieve fine grain strengthening. The Al2Cr4C2 fine particle reinforcement phase formed after α-Al2O3 is combined with Ni60 alloy is evenly dispersed in the organization and is not easy to fall off, which can play a role in dispersion strengthening. Under the synergistic effect of fine grain strengthening and dispersion strengthening, the addition of α-Al2O3 can effectively improve the wear resistance of the strengthening layer. When the amount of alumina powder is 0.42-0.48% of the weight of the base material, it helps to fully improve the wear resistance of the strengthening layer.

[0067] It can be seen from Example 17, Examples 18-20 and Table 3 that when the weight ratio of tungsten carbide powder to titanium carbide powder is (2.28-2.33):1, the wear resistance of the strengthening layer is better.

[0068] Combining Example 20, Example 21 and Table 3, it can be seen that the relative weight loss rate measured in Example 21 is relatively low. This is because the rare earth elements in rare earth ferrosilicon can increase the toughness of the spray-melted layer matrix and improve the ability of the matrix to coat the tungsten carbide particles. The addition of rare earth ferrosilicon also changes the tungsten carbide from its original sharp angle to an obtuse angle, so that the interface bonding with the matrix phase is more firm. When performing wear tests, the ability of tungsten carbide to resist peeling is enhanced, which is beneficial to improving the wear resistance of the strengthening layer.

[0069] Combining Example 21, Example 22-25 and Table 3, it can be seen that the relative weight loss rate measured in Example 22-25 is relatively low. This is because the lubricant has a certain plasticity. Under the high temperature generated during friction, the lubricant will be squeezed out to form a transfer film and spread on the surface of the strengthening layer to form a FeMo2S4, CaMoO4, CaF2 mixed transfer film, thereby avoiding direct contact between the strengthening layer and the wear part, and improving the wear resistance of the strengthening layer. When the lubricant dosage is 6.5-6.8% of the total weight of the base material, the wear resistance of the strengthening layer is better.

[0070] The above embodiments are merely explanations of the present application and are not limitations of the present application. After reading this specification, those skilled in the art may make modifications to the embodiments of the present application without any creative contribution as needed. However, as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for strengthening the surface of a shield machine cutter ring, characterized in that: The following steps are involved: (1) grinding and cleaning the surface of the cutter ring, and drying for later use; mixing ceramic powder and alloy powder in a weight ratio of (0.24-0.27):1 to obtain a base material, mixing the base material and the auxiliary agent, and then ball milling to obtain a mixed powder, which is dried for later use; the alloy powder includes Ni60 alloy powder, the auxiliary agent includes lanthanum oxide, and the ceramic powder includes titanium carbide powder and tungsten carbide powder; (2) The mixed powder is coated on the surface of the cutter ring and then preheated. The mixed powder is processed using a laser cladding device under argon protection to form a strengthening layer on the surface of the cutter ring, thereby completing the surface strengthening of the cutter ring of the shield machine.

2. The method for strengthening the surface of a shield machine cutter ring according to claim 1, characterized in that: The amount of lanthanum oxide used is 1.3-1.5% of the weight of the base material.

3. The method for strengthening the surface of a shield machine cutter ring according to claim 2, characterized in that: The auxiliary agent also includes titanium dioxide nanotubes, and the titanium dioxide nanotubes are prepared according to the following method: Titanium dioxide powder and sodium hydroxide solution are mixed and sealed in an autoclave with a polytetrafluoroethylene liner. After heating, the mixture is kept warm at 115-165°C for reaction. After the heat preservation is completed, the autoclave is naturally cooled. The product is washed with hydrochloric acid, then ultrasonically treated in hydrochloric acid, and finally washed with distilled water. Titanium dioxide nanotubes are obtained after drying.

4. The method for strengthening the surface of a shield machine cutter ring according to claim 3, characterized in that: In the method for preparing the titanium dioxide nanotubes, the heat preservation reaction is carried out at 135-165°C.

5. The method for strengthening the surface of a shield machine cutter ring according to claim 1, characterized in that: The auxiliary agent also includes alumina powder, and the crystal form of the alumina powder is α-alumina.

6. The method for strengthening the surface of a shield machine cutter ring according to claim 5, characterized in that: The amount of the alumina powder used is 0.42-0.48% of the weight of the base material.

7. The method for strengthening the surface of a shield machine cutter ring according to claim 1, characterized in that: The weight ratio of the tungsten carbide powder to the titanium carbide powder is (2.28-2.33):

1.

8. The method for strengthening the surface of a shield machine cutter ring according to claim 7, characterized in that: The auxiliary agent also includes rare earth ferrosilicon.

9. The method for strengthening the surface of a shield machine cutter ring according to claim 1, characterized in that: The auxiliary agent also includes a lubricant, and the lubricant includes molybdenum sulfide and calcium fluoride.

10. The method for strengthening the surface of a shield machine cutter ring according to claim 9, characterized in that: The amount of the lubricant is 6.5-6.8% of the total weight of the base material.

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