42CrMo coal machine hydraulic prop surface defect repairing method based on laser cladding

Abstract

The invention relates to a 42CrMo coal machine hydraulic prop surface defect repairing method based on laser cladding, which adopts iron-based self-fluxing laser cladding alloy powder with specific components as repairing alloy powder, and forms a repairing layer on a defect part through laser scanning cladding. The alloy powder comprises, by mass, 15%-20% of Cr, 0.3%-0.6% of Mn, 2%-4% of Ni, 0.5%-1% of Si, 0.4%-1% of B, 2.5%-5% of Mo and the balance Fe and inevitable impurities. Through collaborative optimization of alloy powder component design and a laser process, high-strength metallurgical bonding of a repairing layer and a matrix is achieved, the repairing layer is compact in structure and free of defects, the abrasion resistance and corrosion resistance of the coal machine hydraulic prop are remarkably improved, and the service life of the coal machine hydraulic prop is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of metal surface repair and remanufacturing technology, specifically relating to a laser cladding repair method for surface wear, corrosion, cracks and other defects on 42CrMo steel hydraulic supports for coal mining machinery. In particular, it is a process method that achieves high-performance repair by optimizing the surface defect repair alloy powder system and laser process parameters. Background Technology

[0002] Hydraulic props for coal mining are core support equipment in fully mechanized coal mining faces, and their performance directly affects the safety and production efficiency of underground mining. 42CrMo steel, a medium-carbon alloy structural steel, possesses excellent strength, toughness, and hardenability, enabling it to withstand complex underground loads, making it a key material for manufacturing these hydraulic props.

[0003] However, in the extremely harsh working conditions of underground coal mines, the surface of hydraulic supports is subjected to high pressure, strong impact, severe abrasive wear, and synergistic erosion by acidic corrosive media (such as mine water containing sulfur and chloride ions) for extended periods, making it highly susceptible to defects such as localized wear, corrosion pits, and fatigue cracks. If these surface damages are not repaired in a timely and effective manner, they will drastically accelerate the failure process of the supports, posing serious safety hazards. Therefore, developing a highly reliable surface repair technology that can adapt to the harsh underground conditions and restore or even improve the performance of supports is of great significance for ensuring safe production in coal mines and reducing the total life-cycle cost of equipment.

[0004] Currently, the main engineering repair methods for surface defects of such key load-bearing components include traditional welding, surface coating and thermal spraying. However, these methods all have fundamental defects that are difficult to overcome and cannot meet the requirements of high strength, high bonding and long-term durability of the repair layer for the hydraulic support of 42CrMo coal mining machinery.

[0005] 1. Traditional weld overlay repair technology: This typically involves cladding wear-resistant alloy onto the defective area using methods such as arc welding or gas shielded welding. This process involves high heat input, resulting in a wide heat-affected zone and high residual stress, which easily leads to structural deformation and performance degradation. More importantly, the weld overlay and the 42CrMo matrix often exhibit a high degree of dilution in their fusion bonding, resulting in coarse microstructure near the interface and a tendency to produce defects such as porosity and slag inclusions, leading to insufficient bond strength. Under complex alternating loads in the well, the repaired component faces an extremely high risk of cracking and peeling of the repair layer, making it difficult to guarantee long-term reliability.

[0006] 2. Surface coating repair technology: Although surface coating technologies such as electroplating hard chrome and electroless nickel plating can form a functional thin layer with a certain degree of hardness and corrosion resistance on the workpiece surface, the bonding between the coating and the substrate is mainly mechanical interlocking or physical adsorption, resulting in low bonding strength. For hydraulic supports that are subjected to high-intensity impact and bending stress, this weak interface bonding is fatal. The coating is very prone to local peeling during service, leading to more serious concentrated corrosion and wear.

[0007] 3. Thermal spraying repair technology: This technology mainly includes flame spraying and plasma spraying. The resulting coating usually contains high porosity and oxide inclusions, resulting in poor coating density and a bond to the substrate that is mainly mechanical, with limited bonding strength. To seal the pores and improve performance, subsequent remelting or infiltration sealing treatments are often required, making the process complex and increasing overall costs. Furthermore, the overall mechanical properties and impact resistance of the repaired layer still fail to meet the requirements of load-bearing structural components.

[0008] In recent years, laser cladding technology, as an advanced additive remanufacturing method, has shown great potential in the field of high-end equipment repair due to its outstanding advantages such as high energy density, precise and controllable heat input, rapid cooling rate, and metallurgical bonding between the coating and the substrate. However, directly applying laser cladding technology to the surface defect repair of 42CrMo coal mining machinery hydraulic supports still faces a series of technical bottlenecks that urgently need to be addressed.

[0009] Firstly, there is a lack of specialized repair alloy materials. Currently available commercially available nickel-based, cobalt-based, or general-purpose iron-based alloy laser cladding powders are not designed for the chemical composition and physical properties of 42CrMo steel. The two are mismatched in terms of thermal expansion coefficient and phase transformation behavior, which easily generates huge thermal stress and structural stress at the cladding interface. This is one of the fundamental reasons for the cracking and peeling of the cladding layer.

[0010] Secondly, the cladding process has poor compatibility with the material structure. There is a lack of a laser cladding process system that is optimized in a coordinated manner for the 42CrMo matrix, special alloy powder and hydraulic support structure characteristics. Improper process parameters not only fail to relieve stress, but also induce defects such as porosity and lack of fusion, which seriously affect the repair quality.

[0011] Therefore, there is an urgent need to develop a laser cladding surface defect repair method specifically for hydraulic supports of 42CrMo coal mining machines, in order to obtain a high-performance, defect-free repair layer and ensure the stability of the process. Summary of the Invention

[0012] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for repairing surface defects of 42CrMo coal mining machinery hydraulic supports based on laser cladding. By using a special alloy material system to synergistically optimize the laser process, a repair layer without cracks, pores, or other defects is formed on the surface defect area of ​​the 42CrMo coal mining machinery hydraulic support. This layer has good bonding with the substrate and its mechanical properties and corrosion resistance are stronger than those of the substrate.

[0013] To achieve the above-mentioned objectives, the present invention provides a method for repairing surface defects of 42CrMo coal mining machinery hydraulic supports based on laser cladding. This method uses iron-based self-fluxing laser cladding alloy powder with specific composition as the surface defect repair alloy powder, and employs laser scanning cladding to repair the surface defects of the 42CrMo coal mining machinery hydraulic supports, thereby forming a laser cladding repair layer at the surface defect site of the 42CrMo coal mining machinery hydraulic supports.

[0014] The iron-based self-fluxing laser cladding alloy powder, by mass percentage, comprises Cr 15-20%, Mn 0.3-0.6%, Ni 2-4%, Si 0.5-1%, B 0.4-1%, Mo 2.5-5%, with the balance being Fe and unavoidable impurities. The composition of the alloy powder is a necessary condition for forming a crack-free, wear-resistant, and corrosion-resistant repair layer on the 42CrMo coal mining machine hydraulic support.

[0015] The laser scanning cladding process parameters are: laser power 1100-1300W, scanning speed 5-6mm / s, spot diameter 3-5mm, and overlap rate 40-60%. These process parameters are used to control the heat input and cooling rate, which are synergistic conditions for achieving good metallurgical bonding between the repair layer and the substrate without crack defects.

[0016] Furthermore, the more detailed method for repairing surface defects of the 42CrMo coal mining machine hydraulic support of the present invention includes: The iron-based self-fluxing laser cladding alloy powder is vacuum dried at 100-150°C for 1-2 hours to remove moisture and adsorbed gas, thereby improving the powder's fluidity and cladding consistency, and obtaining a surface defect repair alloy powder. The surface defect repair alloy powder is delivered to the surface defect area of ​​the 42CrMo coal mining machine hydraulic support, and a semiconductor laser is used to perform laser scanning cladding under the conditions of laser power of 1100-1300W, scanning speed of 5-6mm / s, spot diameter of 3-5mm, and overlap rate of 40-60% to form a laser cladding repair layer.

[0017] More specifically, in the repair method of the present invention, the particle size of the iron-based self-fluxing laser cladding alloy powder is preferably 15-50 μm.

[0018] Furthermore, the present invention preferably involves applying the surface defect repair alloy powder to the surface defect area of ​​the 42CrMo coal mining machine hydraulic support using a coaxial powder feeding method for laser scanning cladding repair.

[0019] To prevent excessive heat input and residual stress from causing cracks in the cladding repair layer, a lower laser power should generally be used. More preferably, the semiconductor laser used in the repair method of the present invention has a laser power of 1200W, a scanning speed of 5-6 mm / s, a spot diameter of 4 mm, and an overlap rate of 50%.

[0020] Furthermore, the present invention preferably sets the powder feeding rate of the coaxial powder feeding method to 10-15 g / min and the carrier gas flow rate to 6-9 L / min.

[0021] When repairing surface defects of 42CrMo coal mining machinery hydraulic support with laser cladding, the present invention requires pretreatment of the defective parts of the coal mining machinery hydraulic support. Specifically, the surface defects of the 42CrMo coal mining machinery hydraulic support are ground flat, and impurities such as oxide scale, rust and oil stains are removed. A bevel is then formed at the surface defective parts.

[0022] Furthermore, in order to prevent poor fusion after the defect area is repaired, the present invention preferably limits the bevel angle of the ground defect area to less than 45° and the bevel depth to 1.2 to 1.5 times the defect depth, so as to increase the fusion area, alleviate stress concentration and enhance the interface bonding.

[0023] The repair method of the present invention also includes post-processing of the formed laser cladding repair layer. Specifically, after the laser cladding repair layer has cooled naturally to room temperature, excess cladding material on the surface is removed, and polishing or sandblasting is performed if necessary to improve the surface roughness.

[0024] By performing penetrant testing on the formed laser cladding repair layer, it was confirmed that there were no cracks in the laser cladding repair layer formed by repairing the hydraulic support using the surface defect repair method of the present invention.

[0025] The surface defect repair method of the present invention uses a special alloy powder with specific composition to perform laser cladding repair on the surface defects of 42CrMo coal mining machinery hydraulic support. Based on the good self-fluxing and wettability imparted by B and Si elements in the alloy powder, as well as the synergistically optimized laser cladding process, a defect-free laser cladding repair layer can be successfully obtained without the need for overall preheating of the large hydraulic support. Metallographic observation and penetrant testing show that the repair layer and the 42CrMo matrix are densely bonded at the interface, exhibiting good metallurgical bonding characteristics, and the repair layer is free of defects such as cracks and pores.

[0026] In particular, the addition of 2.5-5% Mo element in the special alloy powder of this invention strengthens the repair layer through solid solution and promotes the formation of fine carbides. In synergy with other elements such as Cr and Ni in the alloy, it effectively refines the microstructure of the repair layer. Thus, without excessively increasing brittleness, it significantly improves the wear resistance and corrosion resistance of the repair layer. In particular, the corrosion resistance is significantly better than that of the substrate, and it is less likely to generate galvanic cells during subsequent use, causing corrosion defects again. Attached Figure Description

[0027] Figure 1 This is a cross-sectional metallographic diagram of the interface between the laser cladding repair layer and the hydraulic support after repair in Example 1.

[0028] Figure 2 This is the result of penetrant testing of the laser cladding repair layer in Example 1.

[0029] Figure 3 This is a cross-sectional metallographic diagram of the interface between the laser cladding repair layer and the hydraulic support after repair in Example 2.

[0030] Figure 4 This is a comparison chart of the friction coefficients of the examples, comparative examples, and 42CrMo matrix over time.

[0031] Figure 5 These are comparison diagrams of the wear depth of the embodiments, comparative examples, and 42CrMo substrate.

[0032] Figure 6 These are polarization curves of the embodiments, comparative examples, and 42CrMo matrix. Implementation

[0033] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings and specific examples. It should be noted that the embodiments are merely illustrative and are intended to provide a thorough understanding of the technical solutions of the present invention and to provide guidance for those skilled in the art to implement and apply the present invention. It should be understood that these descriptions do not constitute any limitation on the scope of protection of the present invention.

[0034] Unless otherwise expressly stated, the production processes, experiments, tests or analysis methods involved in the embodiments of the present invention are all considered to be conventional methods known to those skilled in the art, and only need to be implemented in accordance with conventional conditions or relevant product instructions. The steps and names involved are also generally clear and unambiguous in the art.

[0035] The instruments, equipment, raw materials, reagents, or samples used in the embodiments are not subject to any special restrictions on their source. They are all conventional products that can be purchased through regular commercial channels or prepared by known methods, and their source does not have a substantial impact on the implementation results of the present invention.

[0036] Unless otherwise expressly defined, the scientific and technical terms used in this invention have the meanings commonly understood by one of ordinary skill in the art. In case of any conflict, the definitions in this specification shall prevail.

[0037] The terms “comprising,” “including,” “having,” etc., used in this invention should be understood as open-ended, meaning “including but not limited to.” The term “and / or” includes any and all combinations of one or more of the associated listed items. Quantitative terms such as “a,” “one,” etc., do not exclude multiples; “multiple” or “a variety” refers to quantities greater than or equal to two.

[0038] The terms "preferred", "better", and "exemplary" used in this invention are only used to describe specific solutions or effects and are not intended to limit the necessary scope of the solution or the scope of protection.

[0039] This invention relates to the description of numerical parameters (such as quantity, concentration, temperature, time, etc.), and it should be understood that reasonable deviations naturally exist due to measuring instruments, operational errors, statistical fluctuations, etc. The range of such deviations should be within limits acceptable to those skilled in the art based on common sense.

[0040] The following are several embodiments of the present invention’s method for repairing surface defects of 42CrMo coal mining machine hydraulic support based on laser cladding. The core of the method is to use iron-based self-fluxing laser cladding alloy powder with specific composition as the surface defect repair alloy powder, and to perform laser cladding repair by matching and optimizing the laser cladding process parameters to ensure the effect of defect repair.

[0041] The chemical composition of the iron-based self-fluxing laser cladding alloy powder, by mass percentage, is: Cr 15-20%, Mn 0.3-0.6%, Ni 2-4%, Si 0.5-1%, B 0.4-1%, Mo 2.5-5%, with the balance being Fe and unavoidable impurities. These unavoidable impurities include conventional elements such as P, S, O, and N, with each impurity content ≤0.03% and the total content ≤0.1%. This specific composition design is the material basis and necessary condition for ensuring that the repair layer possesses high hardness, good toughness, and excellent wear and corrosion resistance, while achieving compatibility with the 42CrMo matrix and avoiding interfacial cracking.

[0042] The particle size of the alloy powder described in this invention is preferably 15-50 μm. The alloy powder that meets the requirements can be prepared by conventional vacuum melting and gas atomization processes based on the chemical composition determined above.

[0043] To achieve a crack-free repair layer with high bonding strength, this invention synergistically optimizes the core process parameters of laser cladding. These parameters are matched with the aforementioned alloy powder of specific composition to precisely control heat input, molten pool behavior, and cooling rate. The optimal process parameter range determined through experiments is: laser power 1100–1300 W, scanning speed 5–6 mm / s, spot diameter 3–5 mm, and overlap rate 40–60%. Within this parameter range, it ensures sufficient melting of the alloy powder and metallurgical bonding with the substrate while effectively suppressing defects such as cracks and porosity caused by excessive thermal stress. This is a key process guarantee and synergistic condition for obtaining a high-performance repair layer.

[0044] The method for repairing surface defects of 42CrMo coal mining machinery hydraulic supports based on laser cladding specifically includes the following steps:

[0045] 1) Alloy powder pretreatment: The alloy powder is vacuum dried at 100-150℃ for 1-2 hours and then naturally cooled for later use;

[0046] 2) Pre-treatment of defective areas: Grind the surface defects of the hydraulic support to make it smooth, remove rust and oil stains, and process a bevel with an angle of less than 45° and a depth of 1.2 to 1.5 times the depth of the defect;

[0047] 3) Laser cladding repair: Using a coaxial powder feeding method, dry alloy powder is delivered to the defective area at a powder feeding rate of 10-15 g / min and a carrier gas flow rate of 6-9 L / min, and laser scanning cladding is performed under the optimized process parameters.

[0048] 4) Post-processing and inspection: After the cladding layer has cooled naturally, the excess surface height is removed, and non-destructive testing methods such as penetrant testing are used to confirm the quality of the repair layer.

[0049] Through the synergistic design of the above materials, processes and structures, the present invention can form a high-quality repair layer with superior performance to the substrate on the surface of the 42CrMo coal mining machine hydraulic support, achieving safe, efficient and green remanufacturing. Example

[0050] Example 1

[0051] This embodiment demonstrates the use of the method of the present invention to repair a surface wear defect of approximately 1.0 mm deep on a 42CrMo coal mining machine hydraulic support.

[0052] 1. Alloy powder preparation

[0053] The iron-based self-fluxing laser cladding alloy powder, specially designed for this invention, has the following chemical composition by mass percentage: Fe-18.2Cr-0.5Mn-2.85Ni-0.75Si-0.65B-2.5Mo. It is prepared through vacuum melting and gas atomization processes, and then sieved to obtain powder with a particle size range of 15–50 μm. Before use, the powder is placed in a vacuum drying oven and dried at 120°C for 2 hours, followed by natural cooling to obtain the surface defect repair alloy powder for laser cladding.

[0054] 2. Defect pretreatment

[0055] For the wear defect of approximately 1.0 mm deep on the surface of the 42CrMo coal mining machine hydraulic support, mechanical grinding was performed to thoroughly remove oxide scale, rust, and oil stains. A V-shaped bevel with an angle of 30° and a depth of 1.2 mm was then machined at the defect to increase the fusion area. The bevel and its surrounding area were ultrasonically cleaned with anhydrous ethanol and dried without overall preheating.

[0056] 3. Laser cladding repair

[0057] Repair is carried out using a coaxial powder feeding laser cladding system. This system uses a Raycus RFL-C6000XC semiconductor laser as the light source and works with a FANUC robot to achieve fully automatic walking and path control.

[0058] Observe the surface morphology of the defects after polishing, and use a robot teach pendant to plan a continuous overlapping laser scanning path.

[0059] The process parameters for laser cladding repair are set as follows: laser power 1200W, spot diameter 4mm, scanning speed 5mm / s, and overlap rate 50%.

[0060] The powder feeding system parameters are set as follows: powder feeding rate 12g / min, powder carrier gas (argon) flow rate 9L / min, and protective gas (argon) flow rate 15L / min.

[0061] The laser cladding system is activated, and the laser head moves along a predetermined trajectory. The coaxial powder feeding device evenly delivers dry alloy powder into the area affected by the laser spot. The laser beam causes the powder and the substrate surface to melt instantly, forming a molten pool, which then rapidly solidifies. Through multiple overlapping scans, a complete laser cladding repair layer is formed at the defective area.

[0062] 4. Post-processing and testing

[0063] After the laser cladding repair layer has cooled to room temperature naturally, a precision machine tool is used to remove excess cladding material from the surface, making the repaired area flush with the original surface of the hydraulic support.

[0064] Metallographic specimens of the repair layer cross-section were prepared and observed under a metallographic microscope. The results are as follows: Figure 1 As shown. Figure 1 The upper and middle parts are laser cladding repair layers, and the lower part is the substrate. It can be seen that the repair layer has a uniform and fine structure, and the interface between it and the 42CrMo substrate is dense and continuous. No cracks were found in the metallographic image, showing typical metallurgical bonding characteristics.

[0065] After thoroughly cleaning and drying the surface of the laser cladding repair layer with a cleaning agent, apply YP-T penetrant and leave for 10-15 minutes. Then, wipe off any excess penetrant with a cloth sprayed with cleaning agent. Spray YD-T developer evenly onto the repair layer surface from a distance of 20-30 cm and observe the color development. If defects exist on the repair layer surface, the defective areas will appear as bright red against the white developer background. The color development results are as follows. Figure 2 As shown in the figure, there are no bright red marks on the surface of the repair layer, indicating that the laser cladding repair layer has no defects such as cracks or pores.

[0066] Example 2

[0067] This embodiment demonstrates the use of the method of the present invention to repair a localized depression defect on the surface of a 42CrMo coal mining machine hydraulic support caused by corrosion.

[0068] 1. Alloy powder preparation

[0069] The iron-based self-fluxing laser cladding alloy powder, specially designed for this invention, has the following chemical composition by mass percentage: Fe-18.2Cr-0.5Mn-2.85Ni-0.75Si-0.65B-5.0Mo. It is prepared through vacuum melting and gas atomization processes, and the powder is sieved to obtain a particle size range of 15–50 μm. Before use, the powder is placed in a vacuum drying oven and dried at 120°C for 2 hours, followed by natural cooling to obtain the surface defect repair alloy powder for laser cladding.

[0070] 2. Defect pretreatment

[0071] The corrosion pits with a depth of about 1.2mm on the surface of the 42CrMo coal mining machine hydraulic support to be repaired were mechanically ground to completely remove corrosion products, oxide scale and oil stains. A V-shaped bevel with an angle of 25° and a depth of 1.5mm was ground and machined at the defect. The bevel and its surrounding area were ultrasonically cleaned with anhydrous ethanol and blown dry. No overall preheating was performed.

[0072] 3. Laser cladding repair

[0073] Using the same coaxial powder-feeding laser cladding system as in Example 1, a denser filling laser scanning path is planned based on the irregular shape of the corrosion pit.

[0074] The process parameters for laser cladding repair are set as follows: laser power 1280W, spot diameter 4.5mm, scanning speed 5.8mm / s, and overlap rate 55%.

[0075] The powder feeding system parameters are set as follows: powder feeding rate 14g / min, powder carrier gas (argon) flow rate 7L / min, and protective gas (argon) flow rate 15L / min.

[0076] The laser cladding system is activated, and the laser head moves along a predetermined trajectory. The coaxial powder feeding device evenly delivers dry alloy powder into the area affected by the laser spot. The laser beam causes the powder and the substrate surface to melt instantly, forming a molten pool, which then rapidly solidifies. Through multiple overlapping scans, a complete laser cladding repair layer is formed at the defective area.

[0077] 4. Post-processing and testing

[0078] After the laser cladding repair layer has cooled to room temperature naturally, a precision machine tool is used to remove excess cladding material from the surface, making the repaired area flush with the original surface of the hydraulic support.

[0079] Figure 3 Metallographic images of the cross-section of the above-mentioned repair layer are given. The upper half of the image is the laser cladding repair layer, and the lower half is the substrate. The two have a good bonding effect, and no cracks were found in the image.

[0080] The same penetrant testing method as in Example 1 was used for testing, and no defects such as cracks or pores were found on the surface of the laser cladding repair layer.

[0081] Comparative Example 1

[0082] Except that the composition of the iron-based self-fluxing laser cladding alloy powder is Fe-18.2Cr-0.5Mn-2.85Ni-0.75Si-0.65B, i.e., the Mo content is 0%, the same laser cladding repair method as in Example 1 was used to repair the surface wear defects of the 42CrMo coal mining machinery hydraulic support in Example 1.

[0083] Comparative Example 2

[0084] Except that the composition of the iron-based self-fluxing laser cladding alloy powder is Fe-18.2Cr-0.5Mn-2.85Ni-0.75Si-0.65B-7.5Mo, the same laser cladding repair method as in Example 1 was used to repair the surface wear defects of the 42CrMo coal mining machinery hydraulic support in Example 1.

[0085] Comparative Example 3

[0086] Except that the composition of the iron-based self-fluxing laser cladding alloy powder is Fe-18.2Cr-0.5Mn-2.85Ni-0.75Si-0.65B-10Mo, the same laser cladding repair method as in Example 1 was used to repair the surface wear defects of the 42CrMo coal mining machinery hydraulic support in Example 1.

[0087] To verify the performance of the laser cladding repair layer formed by the surface defect repair method of the present invention, the wear resistance and corrosion resistance of the repair layers obtained in Examples 1, 2, and 1-3 were tested using a 42CrMo coal mining machinery hydraulic support substrate as a control.

[0088] The wear resistance of reciprocating friction wear was tested using an SHR-2M high-speed reciprocating friction testing machine. The specific test parameters were: test load 30N, reciprocating length 5mm, wear time 30min, friction speed 300r / min, friction pair using Si3N4 ceramic balls, and test temperature at room temperature.

[0089] The specific abrasion resistance test curve is as follows: Figure 4 , 5 As shown, where Figure 4 This is a curve showing the change of the friction coefficient over time. Figure 5 This is a curve showing the comparison of wear mark depth.

[0090] from Figure 4 It can be seen that the friction coefficients of Examples 1 and 2 and Comparative Examples 1, 2 and 3 all reached a stable state relatively quickly over time, and the friction coefficients after stabilization were all lower than those of the 42CrMo matrix.

[0091] Figure 5 In the examples, the wear depth of Examples 1 and 2 is significantly smaller than that of the 42CrMo matrix. In contrast, the wear depth of Comparative Example 3 is larger than that of the 42CrMo matrix. The wear depths of Comparative Examples 1 and 2 are also larger than those of Examples 1 and 2.

[0092] The above wear resistance test results demonstrate that the repair layers obtained using the method of this invention in Examples 1 and 2 exhibit significantly stronger wear resistance than the 42CrMo matrix, and are also superior to all comparative examples. In particular, the wear resistance of Comparative Example 3 is even lower than that of the matrix, which conversely proves the detrimental effect of excessive Mo content on performance.

[0093] Corrosion resistance tests were conducted on a CHI660E electrochemical workstation at room temperature using a 3.5% NaCl solution as the corrosive medium. The specific electrochemical corrosion performance test polarization curves are shown below. Figure 6 As shown.

[0094] Before entering the corrosive state, it is usually at its self-corrosion potential. E corrThis value characterizes the thermodynamic tendency of a material to corrode; the higher the value (the more positive), the lower the tendency to corrode. From... Figure 6 The polarization curves show that Example 2 has the highest corrosion potential (-0.3955V), followed by Example 1 (-0.4905V), and both are higher than the 42CrMo matrix (-0.9454V) and Comparative Examples 1 to 3 (-0.5595V, -0.6669V and -0.4342V respectively), indicating that the repair layer of the present invention is more thermodynamically stable.

[0095] However, once the material enters the corrosion state, the main indicator for evaluating its corrosion performance becomes the corrosion current density. I corr , I corr The smaller the value, the slower the corrosion rate of the material, and the stronger its corrosion resistance. This is achieved through... Figure 6 By performing Tafel extrapolation analysis on the polarization curves, the corrosion current densities of each can be obtained, as detailed in Table 1.

[0096]

[0097] As can be seen from Table 1, the corrosion current density of Examples 1 and 2 is much lower than that of the 42CrMo matrix, and also significantly lower than that of all comparative examples.

[0098] Therefore, the electrochemical test results show that the repair layer obtained by the method of the present invention has a lower corrosion tendency and a slower corrosion rate, and its corrosion resistance is superior to that of the 42CrMo matrix and all comparative examples, which confirms the key role of the specific alloy composition of the present invention in improving corrosion resistance.

[0099] The above embodiments of the present invention do not describe all details exhaustively, nor do they limit the present invention to the embodiments described above. Various changes, modifications, substitutions, and variations made by those skilled in the art to these embodiments without departing from the principles and spirit of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for repairing surface defects of 42CrMo coal mining machinery hydraulic supports based on laser cladding, which uses iron-based self-fluxing laser cladding alloy powder with specific composition as the surface defect repair alloy powder, and uses laser scanning cladding to repair the surface defects of the 42CrMo coal mining machinery hydraulic supports, so as to form a laser cladding repair layer at the surface defect site of the 42CrMo coal mining machinery hydraulic supports: The iron-based self-fluxing laser cladding alloy powder, by mass percentage, comprises Cr 15-20%, Mn 0.3-0.6%, Ni 2-4%, Si 0.5-1%, B 0.4-1%, Mo 2.5-5%, with the balance being Fe and unavoidable impurities. The composition of the alloy powder is a necessary condition for achieving the formation of a crack-free, wear-resistant, and corrosion-resistant repair layer on the 42CrMo coal mining machinery hydraulic support. The laser scanning cladding process parameters are: laser power 1100-1300W, scanning speed 5-6mm / s, spot diameter 3-5mm, and overlap rate 40-60%. These process parameters are used to control the heat input and cooling rate, which are synergistic conditions for achieving good metallurgical bonding between the repair layer and the substrate without crack defects.

2. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 1, comprising: The iron-based self-fluxing laser cladding alloy powder was vacuum dried at 100-150°C for 1-2 hours to obtain a surface defect repair alloy powder. The surface defect repair alloy powder is delivered to the surface defect area of ​​the 42CrMo coal mining machine hydraulic support, and a semiconductor laser is used to perform laser scanning cladding under the conditions of laser power of 1100-1300W, scanning speed of 5-6mm / s, spot diameter of 3-5mm, and overlap rate of 40-60% to form a laser cladding repair layer.

3. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 1 or 2, characterized in that: The particle size of the iron-based self-fluxing laser cladding alloy powder is 15–50 μm.

4. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 1 or 2, characterized in that: The surface defect repair alloy powder was applied to the surface defect area of ​​the 42CrMo coal mining machine hydraulic support using a coaxial powder feeding method, and then laser scanning cladding repair was performed.

5. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 2, characterized in that: The laser power of the laser scanning cladding is 1200W, the scanning speed is 5-6mm / s, the spot diameter is 4mm, and the overlap rate is 50%.

6. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 4, characterized in that: The coaxial powder feeding method has a powder feeding rate of 10-15 g / min and a carrier gas flow rate of 6-9 L / min.

7. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 1 or 2, characterized in that: This also includes pre-treating the surface defects of the 42CrMo coal mining machine hydraulic support, grinding the surface defects of the 42CrMo coal mining machine hydraulic support to smooth them out, removing surface rust and oil stains, and grinding and processing bevels at the surface defect locations.

8. The method for repairing surface defects of 42CrMo coal mining machinery hydraulic support according to claim 7, characterized in that: The bevel angle is less than 45°, and the bevel depth is 1.2 to 1.5 times the defect depth.

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