Surface treatment method for mud pump intermediate tie rod

Abstract

The application discloses a mud pump middle pull rod surface treatment method and relates to the field of coating technology, and comprises the following steps: S1, pretreatment of the pull rod; S2, electroplating of the pretreated pull rod in a modified liquid; and S3, post-treatment of the electroplated pull rod. In the application, the modified liquid electroplating can deposit a uniform and dense nickel-tungsten-nano-alumina composite coating on the surface of the mud pump middle pull rod, and the comprehensive performance of the pull rod is significantly improved; the coating has high hardness, high wear resistance and sufficient toughness through the synergistic effect of the components, can effectively resist the erosion and wear of abrasive particles in the mud, and prolongs the service life of the pull rod; the coating has high density and low porosity, can block the penetration of corrosive media, avoids the occurrence of pitting corrosion and intergranular corrosion of the pull rod matrix, and is suitable for complex corrosion working conditions.

Description

Technical Field

[0001] This invention relates to the field of coating technology, and in particular to a method for surface treatment of the intermediate tie rod of a mud pump. Background Technology

[0002] The surface treatment methods for the intermediate tie rod of a mud pump mainly involve applying a wear-resistant and corrosion-resistant reinforcing coating or surface modification. The most common method is hard chrome plating, which provides a high-hardness, wear-resistant, and corrosion-resistant coating at a relatively low cost.

[0003] Traditional surface treatment coatings for intermediate tie rods in mud pumps suffer from drawbacks such as low bonding strength with the substrate, susceptibility to peeling and cracking, high coating porosity, and poor protective effect. Some coatings also lack toughness and exhibit high internal stress, making them prone to cracking under reciprocating fatigue conditions. Furthermore, traditional processes can easily cause hydrogen embrittlement and high-temperature performance degradation in the substrate, and the low precision in coating thickness control can lead to excessive clearance in the mating section, causing movement jamming. Overall, these methods fail to meet the harsh operating requirements of mud pump tie rods. Therefore, this invention provides a surface treatment method for intermediate tie rods in mud pumps. Summary of the Invention

[0004] The main objective of this invention is to provide a surface treatment method for a mud pump intermediate tie rod with high bonding strength and high microhardness of the coating, which is applied to a surface treatment method for a mud pump intermediate tie rod.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] This invention provides a surface treatment method for the intermediate tie rod of a mud pump, the surface treatment of the intermediate tie rod of the mud pump includes the following steps:

[0007] S1. Pre-process the tie rod.

[0008] S2. Place the pretreated tie rod into the modified solution for electroplating.

[0009] S3. Post-processing of the electroplated tie rod.

[0010] The pretreatment of the tie rod in S1 includes, in sequence, mechanical grinding of the tie rod surface, immersion in modified degreasing solution for degreasing, water washing, weak acid activation pickling, rinsing activation, sandblasting roughening, and high-pressure water washing.

[0011] Furthermore, the surface of the tie rod is mechanically ground, using an 800# white corundum grinding wheel to grind away the fatigue layer on the surface of the tie rod.

[0012] The process involves immersing the ground tie rod in a modified degreasing solution. The temperature of the degreasing solution is set to 60-70℃, and the rod is immersed for 20 minutes.

[0013] The water washing process involves first washing the degreased tie rod with water at 50-60℃ for 2-3 minutes, and then rinsing it with deionized water for 2-3 minutes until the pH of the aqueous phase is 6-7.

[0014] The weak acid activation pickling involves immersing the water-washed pull rod in a weak acid solution for 2-3 minutes.

[0015] The weak acid is composed of deionized water, hexamethylenetetramine, 37% hydrochloric acid, and 98% sulfuric acid in a solid-liquid ratio of 920mL:0.75g:65mL:25mL.

[0016] The rinsing and activation process involves rinsing the acid-washed pull rod with deionized water for 3-5 minutes, using the pull rod as the anode and 304 stainless steel as the cathode, at a rate of 5-8 A / dm. 2 Activate with current for 1-2 minutes.

[0017] The roughening process involves dry blasting the activated tie rod with 80-100 mesh white corundum, controlling the pressure at 0.4-0.6 MPa, the blasting distance at 150-200 mm, and the angle at 45-60 degrees. ° The surface is uniformly silvery-gray with a roughness of Ra 1.6-3.2μm.

[0018] The high-pressure water washing involves using 0.2-0.3 MPa high-pressure deionized water to clean the roughened surface of the tie rod.

[0019] Furthermore, the preparation of the modified degreasing solution includes the following steps:

[0020] A1. Dissolve lanthanum chloride in deionized water at 50°C to obtain a lanthanum chloride solution.

[0021] A2. Dissolve disodium ethylenediaminetetraacetate in deionized water at 50°C to obtain a disodium ethylenediaminetetraacetate solution.

[0022] A3. Dissolve benzotriazole in deionized water at 50°C to obtain a benzotriazole solution.

[0023] A4. Heat and stir deionized water at a temperature of 60-70℃ and a speed of 100-150 rpm. Add sodium hydroxide and anhydrous sodium carbonate in sequence and stir for 5-8 minutes. Add sodium tripolyphosphate and sodium citrate and stir for 3-5 minutes. Add lanthanum chloride solution, disodium ethylenediaminetetraacetate solution and benzotriazole solution and stir for 5 minutes. Add didodecyl dimethyl hexammonium chloride and stir for 5-10 minutes to obtain the modified degreasing solution.

[0024] Furthermore, the mass ratio of lanthanum chloride to deionized water in A1 is 1:5.

[0025] Furthermore, the mass ratio of disodium ethylenediaminetetraacetate and deionized water in A2 is 1:5.

[0026] Furthermore, the mass ratio of benzotriazole to deionized water in A3 is 1:5.

[0027] Furthermore, the mass ratio of deionized water, sodium hydroxide, anhydrous sodium carbonate, sodium tripolyphosphate, sodium citrate, lanthanum chloride solution, disodium ethylenediaminetetraacetate solution, benzotriazole solution, and didodecyl dimethylhexammonium chloride in A4 is 100:2.75:2.75:0.9:1.1:0.6:0.75:0.09:0.175.

[0028] Sodium tripolyphosphate is a complexing detergent and dispersant that can efficiently complex hard water ions such as calcium and magnesium in water, thoroughly softening the water, preventing scale formation and avoiding scale adhesion to the substrate. It can disperse oil clumps and impurities generated during the degreasing process, preventing them from re-adhering to the substrate surface and causing secondary pollution. It can also penetrate between the oil and the substrate interface, reducing the adhesion of oil and making it easier to remove oil, thus significantly improving the overall degreasing and cleaning effect.

[0029] Sodium citrate, as an auxiliary complexing agent and detergent builder, works synergistically with sodium tripolyphosphate to complex trace metal ions in the degreasing solution, eliminating the influence of impurity ions on the activity of the degreasing components. It can enhance the emulsification and dispersion ability of the degreasing solution on oil stains, improve the removal effect on stubborn oil stains, and at the same time improve the overall stability of the degreasing solution, prevent the precipitation of various components in a high-temperature and strongly alkaline environment, ensure the uniformity of the degreasing solution for long-term use, and avoid the degreasing effect being affected by component precipitation.

[0030] Lanthanum chloride, as a rare earth cleaning aid, can be dissolved in warm water in advance to ensure its solubility and dispersibility in the degreasing solution. This can improve the wettability and penetration of the degreasing solution on oil stains, accelerate the peeling and dissolution of oil stains from the stainless steel substrate surface, and improve the overall degreasing efficiency. At the same time, it can form an extremely thin rare earth passivation film on the stainless steel substrate surface, effectively preventing the rapid formation of floating rust in the air after degreasing, protecting the smoothness of the substrate surface, and preserving an intact substrate surface for subsequent electroplating processes.

[0031] Disodium EDTA is a highly efficient complexing agent that can complex various metal ions in degreasing solutions, including hard water ions and trace metal ions dissolved from the matrix surface. It completely eliminates the interference of impurity ions on the degreasing and corrosion inhibition effects, while also enhancing the system stability of the degreasing solution, preventing the components from reacting and failing due to the influence of metal ions, and ensuring that all additives can play their full role.

[0032] Benzotriazole is a special corrosion inhibitor for stainless steel. Dissolving it in warm water beforehand can prevent it from precipitating in strongly alkaline degreasing solutions. In a strongly alkaline environment, it can selectively adsorb onto the surface of the stainless steel substrate, forming a dense adsorption film that isolates the strong alkaline solution from excessive contact with the substrate. This effectively prevents the substrate from over-corrosion, pitting, or intergranular corrosion, protects the surface smoothness and structural integrity of the stainless steel substrate, and avoids surface defects caused by strong alkaline corrosion, laying a good foundation for the tight adhesion of subsequent electroplating coatings.

[0033] Didodecyl dimethyl hexammonium chloride is a low-foaming, high-efficiency degreasing surfactant that significantly reduces the surface tension of the degreasing solution and greatly improves its wettability on stainless steel substrates. This allows the degreasing solution to fully cover every area of ​​the substrate surface, including tiny crevices, achieving all-around degreasing. Its low-foaming properties prevent foam buildup during the degreasing process from affecting agitation and degreasing efficiency, eliminating the need for additional defoamers. At the same time, it can further emulsify and disperse oil stains, preventing secondary adhesion and significantly improving overall degreasing cleanliness and production efficiency.

[0034] Further, step S2, which involves immersing the pretreated pull rod in the modified solution for electroplating, comprises: suspending the high-pressure washed pull rod in a PTFE fixture, placing the fixture into the electroplating tank, immersing the pull rod in the modified solution, heating the modified solution to 80-90°C, turning on air agitation, and setting the electroplating power supply to DC power, initially applying 50A / dm. 2 Electroplating with impact current for 1-2 minutes, with the current density adjusted to 30-40 A / dm³. 2 Set the temperature to 80-90℃ and electroplat for 2-4 hours. Turn off the power, remove the tooling, and clean the pull rod with deionized water until the pH of the aqueous phase is 6-7.

[0035] Furthermore, the preparation of the modified liquid includes the following steps:

[0036] B1. Mix nano-alumina and anhydrous ethanol at 400 rpm for 5 minutes, add γ-aminopropyltriethoxysilane and stir at 400 rpm for 2 minutes, add hydrochloric acid and stir, set the temperature to 30℃, stir at 400 rpm for 3 hours to obtain a mixture; vacuum dry the mixture at 80℃ and a vacuum degree of -0.09 MPa for 6 hours to obtain modified nano-alumina.

[0037] B2. Mix and ultrasonically disperse the modified nano-alumina and deionized water at a power of 400W and a frequency of 30kHz for 40 minutes to obtain a modified nano-alumina suspension.

[0038] B3. Mix sodium tungstate and deionized water and stir at 400 rpm for 8 minutes. Add cerium nitrate and stir at 400 rpm and 45°C for 30 minutes. Allow the mixture to cool naturally to 25°C. Add sodium hydroxide and stir at 300 rpm for 2 minutes. Add γ-glycidyl oxypropyltrimethoxysilane solution and stir at 400 rpm for 20 minutes to obtain a modified sodium tungstate solution.

[0039] B4. Add deionized water to the electrolytic cell and heat to 50-60℃. Add citric acid, potassium sodium tartrate, and sodium acetate sequentially and stir at 400 rpm for 5 minutes. Add nickel sulfate and modified sodium tungstate solution and stir at 400 rpm for 8 minutes. Allow the temperature to cool naturally to 25℃. Add sodium hypophosphite and sodium dodecyl sulfate and stir at 400 rpm for 5 minutes. Add modified nano-alumina suspension and stir at 400 rpm for 15 minutes. Add dilute sulfuric acid solution and stir at 300 rpm for 2 minutes. Heat to 85℃ and stir at 400 rpm for 30 minutes. Filter through a 200-mesh filter to remove impurities and obtain the modified solution.

[0040] Further, the solid-liquid ratio of nano-alumina and anhydrous ethanol in B1 is 1g:20mL; the mass ratio of nano-alumina and γ-aminopropyltriethoxysilane is 1:0.02-0.03; hydrochloric acid is added to adjust the pH to 4-5; the hydrochloric acid is a 10% aqueous solution.

[0041] Furthermore, the solid-liquid ratio of modified nano-alumina and deionized water in B2 is 1g:1L.

[0042] Further, in B3, the mass ratio of sodium tungstate to deionized water is 1:5; the mass ratio of sodium tungstate to cerium nitrate is 1:0.0075; the mass ratio of sodium tungstate to γ-glycidoxypropyltrimethoxysilane solution is 1:0.018; the γ-glycidoxypropyltrimethoxysilane solution is a mixture of γ-glycidoxypropyltrimethoxysilane and anhydrous ethanol at a mass ratio of 1:5; sodium hydroxide is added to adjust the pH to 8-9; the sodium hydroxide is a 6% aqueous solution.

[0043] Cerium nitrate, as a rare earth modifier, can form stable complexes with tungstate ions, optimizing the stability of concentrated sodium tungstate solutions. Simultaneously, this complexation regulates the reaction morphology of tungstate ions, enhancing the synergistic binding of tungstate ions with other metal ions during subsequent electroplating. This allows tungsten to be more uniformly integrated into the composite coating and also strengthens the structural stability of tungstate ions, preventing their dissociation in subsequent processes and ensuring a stable supply of tungsten to the coating from sodium tungstate.

[0044] γ-glycidyl etheroxypropyltrimethoxysilane solution is a core material for modifying sodium tungstate. It can form stable covalent bonds with tungstate ions to achieve graft modification of sodium tungstate, optimize the interfacial properties of concentrated sodium tungstate solution, and significantly improve the compatibility of sodium tungstate with subsequent electroplating composite solutions. This avoids stratification, precipitation, or local enrichment of sodium tungstate after it is added to the electroplating solution. At the same time, this graft modification can enhance the bonding force between tungstate ions and fillers such as the coating matrix and nano-alumina, allowing tungsten to be more firmly integrated into the composite coating and fully exert the core role of tungsten in improving the hardness and wear resistance of the coating.

[0045] Further, the solid-liquid ratio of the deionized water, citric acid, potassium sodium tartrate, sodium acetate, nickel sulfate, modified sodium tungstate solution, sodium hypophosphite, sodium dodecyl sulfate, and modified nano-alumina suspension in B4 is 100L:3.5kg:2.5kg:1.2kg:9kg:12.5L:1.2kg:0.08kg:10L; the dilute sulfuric acid aqueous solution has a mass concentration of 10%; and the pH is adjusted to 4-4.5 by adding the dilute sulfuric acid aqueous solution.

[0046] Further, the post-treatment method for the electroplated tie rod in S3 is as follows: the electroplated tie rod is placed in an aging furnace, nitrogen gas is introduced, the temperature is raised to 400℃ at a heating rate of 5-10℃ / min, and held at a constant temperature for 1 hour. The temperature is then lowered to 25℃ at a cooling rate of ≤10℃ / min. The treated tie rod is then placed in a dehydrogenation furnace for annealing, the temperature is raised to 180-200℃ at a heating rate of 10-15℃ / min, and held at a constant temperature for 2-4 hours. Heating is then stopped, and the temperature inside the dehydrogenation furnace is allowed to cool naturally to 25℃. The annealed tie rod is then rough polished with 1200# diamond polishing paste, with a polishing amount of 0.01-0.02mm. Then, it is finely polished with 2000# diamond polishing paste until the roughness Ra of the filler mating section is 0.4-0.8μm and the non-matting section is 0.8-1.6μm. The final coating thickness is maintained at 0.1-0.2mm. After polishing, the polishing paste is removed by wiping with anhydrous ethanol.

[0047] The polishing paste is a white, fine polishing paste.

[0048] The present invention has the following beneficial effects:

[0049] 1. In this invention, the modified degreasing solution provides a highly efficient and gentle pretreatment cleaning effect for the intermediate tie rod of the mud pump through the synergistic effect of multiple components. It thoroughly saponifies and emulsifies the grease and dirt hidden in the crevices of the stainless steel substrate of the tie rod using strong alkaline components, disperses oil stains and prevents secondary adhesion of impurities through complexing agents, and avoids over-corrosion and pitting of the substrate in a strongly alkaline environment by relying on benzotriazole and lanthanum chloride. It also forms a slight passivation film to prevent surface rust after degreasing, protecting the smoothness of the substrate surface throughout the process. This thorough and safe degreasing effect provides a clean and intact substrate surface for subsequent electroplating processes, significantly improving the bonding strength between the plating layer and the tie rod substrate. It prevents problems such as plating peeling and cracking caused by surface impurities from the source, ensuring the overall stability of the tie rod surface treatment and laying a solid foundation for resisting erosion under mud conditions.

[0050] 2. In this invention, a uniform and dense nickel-tungsten-nano alumina composite coating can be deposited on the surface of the intermediate tie rod of the mud pump through modified liquid electroplating, significantly improving the overall performance of the tie rod. Through the synergistic effect of its components, the coating possesses high hardness, high wear resistance, and sufficient toughness, effectively resisting the erosion and wear of abrasive particles in the mud and extending the service life of the tie rod. The coating has high density and low porosity, which can block the penetration of corrosive media and prevent pitting and intergranular corrosion of the tie rod substrate, making it suitable for complex corrosive conditions. At the same time, the modified liquid can ensure that the coating is uniformly deposited in all parts of the tie rod. Combined with subsequent polishing, the surface accuracy of the filling mating section and non-matting section can be precisely controlled to meet the sealing mating requirements, reduce friction and wear with the filling and the risk of leakage, and adapt to the fatigue conditions of the tie rod's reciprocating motion. This gives the tie rod excellent wear resistance, corrosion resistance, and fatigue resistance, making it fully suitable for the harsh working environment of the mud pump.

[0051] 3. In this invention, 1200# diamond coarse polishing and 2000# diamond fine polishing are used, resulting in high hardness and uniform grinding particle size. 1200# can efficiently remove minor defects such as pits and protrusions on the coating surface, and can precisely control the polishing amount to avoid excessive grinding that could lead to excessive coating thickness. 2000# can finely finish the coating surface, precisely controlling the roughness of the filler mating section and the non-matting section within the process requirements, improving surface smoothness, meeting the mating requirements of the filler seal, and ensuring that the coating surface is free of scratches and abrasions after polishing, thus guaranteeing sealing performance and friction performance. Detailed Implementation

[0052] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0053] It should be noted that all raw materials used in the following experiments are commercially available.

[0054] The preparation methods of the modified degreasing solution and modified liquid in the following embodiments and comparative examples of the present invention are as follows:

[0055] I. Preparation of Modified Degreasing Solution

[0056] A1. Dissolve 1g of lanthanum chloride in 5g of deionized water at 50℃ to obtain a lanthanum chloride solution.

[0057] A2. Dissolve 1g of disodium ethylenediaminetetraacetate in 5g of deionized water at 50℃ to obtain a disodium ethylenediaminetetraacetate solution.

[0058] A3. Dissolve 1g of benzotriazole in 5g of deionized water at 50℃ to obtain a benzotriazole solution.

[0059] A4. Heat and stir 100g of deionized water at 65℃ and 130rpm. Add 2.75g of sodium hydroxide and 2.75g of anhydrous sodium carbonate in sequence and stir for 7 minutes. Add 0.9g of sodium tripolyphosphate and 1.1g of sodium citrate and stir for 4 minutes. Add 0.6g of lanthanum chloride solution, 0.75g of disodium ethylenediaminetetraacetate solution and 0.09g of benzotriazole solution and stir for 5 minutes. Add 0.175g of didodecyl dimethyl hexammonium chloride and stir for 8 minutes to obtain the modified degreasing solution.

[0060] II. Preparation of Modified Liquid

[0061] B1. Mix 1g of nano-alumina and 20mL of anhydrous ethanol and stir at 400rpm for 5 minutes. Add 0.02g of γ-aminopropyltriethoxysilane and stir at 400rpm for 2 minutes. Add 10% hydrochloric acid to adjust the pH to 4.5 and stir. Set the temperature to 30℃ and the stirring speed to 400rpm and keep stirring at this temperature for 3 hours to obtain a mixture. Vacuum dry the mixture at 80℃ and a vacuum degree of -0.09MPa for 6 hours to obtain modified nano-alumina.

[0062] B2. Mix 1g of modified nano-alumina and 1L of deionized water and ultrasonically disperse them. Set the power to 400W and the frequency to 30kHz and disperse for 40 minutes to obtain a modified nano-alumina suspension.

[0063] B3. Mix 200g sodium tungstate and 1L deionized water and stir at 400rpm for 8 minutes. Add 1.5g cerium nitrate and stir at 400rpm and 45℃ for 30 minutes. Allow the mixture to cool naturally to 25℃. Add 6% sodium hydroxide to adjust the pH to 8.5 and stir at 300rpm for 2 minutes. Add 3.6g γ-glycidyl oxypropyltrimethoxysilane solution and stir at 400rpm for 20 minutes to obtain a modified sodium tungstate solution.

[0064] B4. Add 100L of deionized water to the electrolytic cell and heat to 55℃. Add 3.5kg of citric acid, 2.5kg of potassium sodium tartrate, and 1.2kg of sodium acetate sequentially, stirring at 400rpm for 5 minutes. Add 9kg of nickel sulfate and 12.5L of modified sodium tungstate solution, stirring at 400rpm for 8 minutes. Allow the temperature to cool naturally to 25℃. Add 1.2kg of sodium hypophosphite and 80g of sodium dodecyl sulfate, stirring at 400rpm for 5 minutes. Add 10L of modified nano-alumina suspension, stirring at 400rpm for 15 minutes. Add 10% dilute sulfuric acid solution to adjust the pH to 4.5, stirring at 300rpm for 2 minutes. Heat to 85℃, stirring at 400rpm for 30 minutes. Filter through a 200-mesh filter to remove impurities, obtaining the modified solution.

[0065] Example 1: A surface treatment method for the intermediate tie rod of a mud pump, comprising the following steps:

[0066] S1. The pretreatment of the tie rod includes mechanical grinding of the tie rod surface, immersion in modified degreasing solution for degreasing, water washing, weak acid activation pickling, rinsing activation, sandblasting roughening and high-pressure water washing.

[0067] The rod surface is mechanically ground, using an 800# white corundum grinding wheel to grind away the fatigue layer on the rod surface.

[0068] The ground tie rod is immersed in a modified degreasing solution to remove oil. The temperature of the degreasing solution is set to 60℃, and the rod is immersed for 20 minutes.

[0069] Wash with water. After degreasing, the tie rod is first washed with 50°C water for 2 minutes, and then rinsed with deionized water for 2 minutes until the pH of the aqueous phase is 6.

[0070] For weak acid activation pickling, immerse the water-washed pull rod in weak acid for 2 minutes.

[0071] The weak acid is prepared by mixing deionized water, hexamethylenetetramine, 37% hydrochloric acid, and 98% sulfuric acid in a solid-liquid ratio of 920mL:0.75g:65mL:25mL.

[0072] Rinse and activate: Rinse the pickled drawbar with deionized water for 3 minutes, using the drawbar as the anode and 304 stainless steel as the cathode, at 5A / dm. 2 Activate with current for 1 minute.

[0073] For roughening, the activated tie rod was dry-blasted with 80-mesh white corundum, with the pressure controlled at 0.4 MPa, the blasting distance at 150 mm, and the angle at 45 degrees. ° The surface is uniformly silvery-gray with a roughness of Ra 1.6 μm.

[0074] High-pressure water washing: Use 0.2% high-pressure deionized water to clean the roughened tie rod surface.

[0075] S2. After high-pressure water washing, suspend the pull rod in a PTFE fixture, place the fixture into the electroplating tank, immersing the pull rod in the modification solution. Heat the modification solution to 80℃, turn on the air agitator, and set the electroplating power supply to DC power, initially supplying 50A / dm. 2 Electroplating with impact current for 1 minute, with the current density adjusted to 30A / dm³. 2 Set the temperature to 80℃ and electroplat for 2 hours. Turn off the power, remove the fixture, and clean the pull rod with deionized water until the pH of the aqueous phase is 6.

[0076] S3. Place the electroplated tie rod in an aging furnace, purge with nitrogen, raise the temperature to 400℃ at a rate of 5℃ / min, hold at that temperature for 1 hour, and lower the temperature to 25℃ at a rate of ≤10℃ / min. Place the treated tie rod in a dehydrogenation furnace for annealing, raise the temperature to 180℃ at a rate of 10℃ / min, hold at that temperature for 2 hours, stop heating, and allow the temperature inside the dehydrogenation furnace to cool naturally to 25℃. Roughly polish the annealed tie rod with 1200# diamond polishing paste, with a polishing amount of 0.01mm, and then finely polish with 2000# diamond polishing paste until the roughness Ra of the filler mating section is 0.4μm and the non-matting section is 0.8μm. The final coating thickness is maintained at 0.1mm. After polishing, wipe off the polishing paste with anhydrous ethanol.

[0077] Example 2: A method for surface treatment of the intermediate tie rod of a mud pump, comprising the following steps:

[0078] S1. The pretreatment of the tie rod includes mechanical grinding of the tie rod surface, immersion in modified degreasing solution for degreasing, water washing, weak acid activation pickling, rinsing activation, sandblasting roughening and high-pressure water washing.

[0079] The rod surface is mechanically ground, using an 800# white corundum grinding wheel to grind away the fatigue layer on the rod surface.

[0080] The ground tie rod is immersed in a modified degreasing solution to remove oil. The temperature of the degreasing solution is set to 65℃ and the rod is immersed for 20 minutes.

[0081] Wash with water. After degreasing, the tie rod is first washed with 55°C water for 2.5 minutes, and then rinsed with deionized water for 2.5 minutes until the pH of the aqueous phase is 6.5.

[0082] For weak acid activation pickling, immerse the washed rod in weak acid for 2.5 minutes.

[0083] The weak acid is prepared by mixing deionized water, hexamethylenetetramine, 37% hydrochloric acid, and 98% sulfuric acid in a solid-liquid ratio of 920mL:0.75g:65mL:25mL.

[0084] After rinsing and activation, the pickled rod is rinsed with deionized water for 4 minutes. The rod is then activated with a current of 6.5 A / dm² for 1.5 minutes, using the rod as the anode and 304 stainless steel as the cathode.

[0085] For roughening, the activated tie rod was dry-blasted with 90-mesh white corundum, with the pressure controlled at 0.5 MPa, the blasting distance at 175 mm, and the angle at 53 degrees. ° The surface is uniformly silvery-gray with a roughness of Ra2.4μm.

[0086] High-pressure water washing: Use 0.25MPa high-pressure deionized water to clean the roughened tie rod surface.

[0087] S2. After high-pressure water washing, suspend the pull rod in a PTFE fixture, place the fixture into the electroplating tank, immersing the pull rod in the modification solution. Heat the modification solution to 85°C, turn on the air agitator, and set the electroplating power supply to DC power, initially supplying 50A / dm. 2 Electroplating with an impact current for 1.5 minutes, with the current density adjusted to 35 A / dm². 2 The temperature was 85℃, and the electroplating was carried out at a constant temperature for 3 hours. The power was turned off, the tooling was removed, and the pull rod was cleaned with deionized water until the pH of the aqueous phase was 6.5.

[0088] S3. Place the electroplated tie rod in an aging furnace, purge with nitrogen, raise the temperature to 400℃ at a rate of 7.5℃ / min, hold at that temperature for 1 hour, and lower the temperature to 25℃ at a rate of ≤10℃ / min. Place the treated tie rod in a dehydrogenation furnace for annealing, raise the temperature to 190℃ at a rate of 12.5℃ / min, hold at that temperature for 3 hours, stop heating, and allow the temperature inside the dehydrogenation furnace to cool naturally to 25℃. Roughly polish the annealed tie rod with 1200# diamond polishing paste, with a polishing amount of 0.015mm, and then finely polish with 2000# diamond polishing paste until the roughness Ra of the filler mating section is 0.6μm and the non-matting section is Ra1.2μm. The final coating thickness is maintained at 0.15mm. After polishing, wipe off the polishing paste with anhydrous ethanol.

[0089] Example 3: A method for surface treatment of the intermediate tie rod of a mud pump, comprising the following steps:

[0090] S1. The pretreatment of the tie rod includes mechanical grinding of the tie rod surface, immersion in modified degreasing solution for degreasing, water washing, weak acid activation pickling, rinsing activation, sandblasting roughening and high-pressure water washing.

[0091] The rod surface is mechanically ground, using an 800# white corundum grinding wheel to grind away the fatigue layer on the rod surface.

[0092] The ground tie rod is immersed in a modified degreasing solution to remove oil. The temperature of the degreasing solution is set to 70℃, and the rod is immersed for 20 minutes.

[0093] Wash with water. After degreasing, the tie rod is first washed with 60°C water for 3 minutes, and then rinsed with deionized water for 3 minutes until the pH of the aqueous phase is 7.

[0094] For weak acid activation pickling, immerse the washed rod in weak acid for 3 minutes.

[0095] The weak acid is prepared by mixing deionized water, hexamethylenetetramine, 37% hydrochloric acid, and 98% sulfuric acid in a solid-liquid ratio of 920mL:0.75g:65mL:25mL.

[0096] After rinsing and activation, the pickled rod is rinsed with deionized water for 5 minutes, and activated with an 8A / dm² current for 2 minutes using the rod as the anode and 304 stainless steel as the cathode.

[0097] For roughening, the activated tie rod was dry-blasted with 100-mesh white corundum, with the pressure controlled at 0.6 MPa, the blasting distance at 200 mm, and the angle at 60 degrees. ° The surface is uniformly silvery-gray with a roughness of Ra 3.2 μm.

[0098] High-pressure water washing: Use 0.3MPa high-pressure deionized water to clean the roughened tie rod surface.

[0099] S2. After high-pressure water washing, suspend the pull rod in a PTFE fixture. Place the fixture into the electroplating tank, immersing the pull rod in the modification solution. Heat the modification solution to 90°C, turn on the air agitator, and set the electroplating power supply to DC, initially applying 50A / dm. 2 Electroplating with impact current for 2 minutes, with the current density adjusted to 40A / dm³. 2 At a temperature of 90℃, electroplating was performed for 4 hours. The power was then turned off, the fixture was removed, and the pull rod was cleaned with deionized water until the pH of the aqueous phase reached 7.

[0100] S3. Place the electroplated tie rod in an aging furnace, purge with nitrogen, raise the temperature to 400℃ at a rate of 10℃ / min, hold at that temperature for 1 hour, and lower the temperature to 25℃ at a rate of ≤10℃ / min. Place the treated tie rod in a dehydrogenation furnace for annealing, raise the temperature to 200℃ at a rate of 15℃ / min, hold at that temperature for 4 hours, stop heating, and allow the temperature inside the dehydrogenation furnace to cool naturally to 25℃. Roughly polish the annealed tie rod with 1200# diamond polishing paste, with a polishing amount of 0.02mm, and then finely polish with 2000# diamond polishing paste until the roughness Ra of the filler mating section is 0.8μm and the non-matting section is Ra1.6μm. The final coating thickness is maintained at 0.2mm. After polishing, wipe off the polishing paste with anhydrous ethanol.

[0101] Comparative Example 1: The difference between this comparative example and Example 1 is that:

[0102] No modified degreasing solution was used for immersion in this comparative example.

[0103] Comparative Example 2: The difference between this comparative example and Example 1 is that:

[0104] Unmodified sodium tungstate was used in the modified solution of this comparative example.

[0105] Comparative Example 3 differs from Example 1 in that:

[0106] Unmodified nano-alumina was used in the modified solution of this comparative example.

[0107] Performance testing: The surface treatment methods for the intermediate tie rods of mud pumps in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 were tested.

[0108] Performance testing: The relevant performance of the mud pump intermediate tie rod samples treated in Examples 1-3 and Comparative Examples 1-3 were tested respectively, and the test data are recorded in Table 1 below:

[0109] Table 1 - Performance Test of Intermediate Tie Rod for Treated Mud Pumps

[0110] Based on the above data, the following conclusions can be drawn:

[0111] The bonding strength of the intermediate tie rods of the mud pumps treated in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested using the test methods in GB / T5270-2005.

[0112] The microhardness (HV) of the coating on the intermediate tie rod of the mud pump treated in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested using the test methods in GB / T4340.1-2009.

[0113] The macroscopic appearance of the intermediate tie rods of the mud pumps treated in Examples 1, 2, 3, Comparative Examples 1, 2, and 3 was tested using the test methods in GB / T43659-2024.

[0114] In the modified degreasing solution, sodium hydroxide and anhydrous sodium carbonate act as strong alkalis to remove surface oil stains. Sodium tripolyphosphate, sodium citrate, and disodium EDTA act as complexing agents to complex impurities and prevent secondary adhesion. Didodecyl dimethyl hexammonium chloride enhances wettability for thorough degreasing, lanthanum chloride inhibits floating rust, and benzotriazole prevents over-corrosion of the substrate. The synergistic effect of these materials results in a clean, smooth, and defect-free substrate surface, providing a good foundation for strong coating adhesion and effectively improving bonding strength. Citric acid, potassium sodium tartrate, and sodium acetate in the modified solution refine the coating grains through complexation, improving the microhardness of the coating and preventing clumping and sedimentation marks. Nickel sulfate forms the coating matrix, and modified sodium tungstate significantly improves the coating hardness. Modified nano-alumina greatly enhances microhardness through dispersion strengthening. Sodium hypophosphite optimizes the coating deposition state, and sodium dodecyl sulfate eliminates appearance defects such as pinholes and pitting.

[0115] For the intermediate tie rod of the mud pump, higher bonding strength and HV microhardness values ​​of the coating are better. Higher bonding strength ensures a stronger bond between the coating and the tie rod substrate, reducing the likelihood of peeling or cracking. Higher microhardness enhances the coating's resistance to abrasive wear from mud slurry, resulting in a longer service life. Lower macroscopic appearance ratings are also preferable, as they indicate a smoother, brighter coating surface free of pits, agglomerations, and color variations, leading to superior overall appearance quality and better meeting subsequent usage requirements.

[0116] Based on the above demonstrations, the present invention is significantly superior to the comparative group in terms of bonding strength, coating microhardness (HV), and macroscopic appearance.

[0117] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0118] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for surface treatment of the intermediate tie rod of a mud pump, characterized in that, The surface treatment of the intermediate tie rod of the mud pump includes the following steps: S1. Pre-process the tie rod; S2. Place the pretreated tie rod into the modified solution for electroplating; S3. Post-processing of the electroplated tie rod; The pretreatment of the tie rod in S1 includes, in sequence, mechanical grinding of the tie rod surface, immersion in modified degreasing solution for degreasing, water washing, weak acid activation pickling, rinsing activation, sandblasting roughening, and high-pressure water washing.

2. The surface treatment method for the intermediate tie rod of a mud pump according to claim 1, characterized in that, The surface of the tie rod is mechanically ground by using a white corundum grinding wheel to grind away the surface of the tie rod. The process involves immersing the ground tie rod in a modified degreasing solution to remove oil. The water washing process involves first washing the degreased pull rod with water, and then rinsing it with deionized water. The weak acid activation pickling involves immersing the water-washed tie rod in a weak acid solution. The weak acid is composed of deionized water, hexamethylenetetramine, 37% hydrochloric acid, and 98% sulfuric acid in a solid-liquid ratio of 920mL:0.75g:65mL:25mL. The rinsing and activation process involves rinsing the acid-washed pull rod with deionized water, and then applying an electric current to activate the rod, which is used as the anode and the stainless steel as the cathode. The roughening process involves dry sandblasting the activated tie rod with white fused alumina. The high-pressure water washing uses high-pressure deionized water to clean the roughened surface of the tie rod.

3. The surface treatment method for the intermediate tie rod of a mud pump according to claim 2, characterized in that, The preparation of the modified degreasing solution includes the following steps: A1. Dissolve lanthanum chloride in deionized water to obtain a lanthanum chloride solution; A2. Dissolve disodium ethylenediaminetetraacetate in deionized water to obtain a disodium ethylenediaminetetraacetate solution; A3. Dissolve benzotriazole in deionized water to obtain a benzotriazole solution; A4. Heat and stir deionized water, then add sodium hydroxide and anhydrous sodium carbonate in sequence, followed by stirring. Add sodium tripolyphosphate and sodium citrate, and stir. Add lanthanum chloride solution, disodium ethylenediaminetetraacetate solution, and benzotriazole solution, and stir. Add dodecyl dimethyl hexammonium chloride, and stir to obtain a modified degreasing solution.

4. The surface treatment method for the intermediate tie rod of the mud pump according to claim 3, characterized in that, The mass ratio of lanthanum chloride to deionized water in A1 is 1:5; The mass ratio of disodium ethylenediaminetetraacetate and deionized water in A2 is 1:5; The mass ratio of benzotriazole to deionized water in A3 is 1:5; The mass ratio of deionized water, sodium hydroxide, anhydrous sodium carbonate, sodium tripolyphosphate, sodium citrate, lanthanum chloride solution, disodium ethylenediaminetetraacetate solution, benzotriazole solution, and didodecyl dimethylhexammonium chloride in A4 is 100:2.75:2.75:0.9:1.1:0.6:0.75:0.09:0.

175.

5. The surface treatment method for the intermediate tie rod of a mud pump according to claim 1, characterized in that, The step of placing the pretreated pull rod into the modified solution for electroplating in S2 is as follows: suspend the pull rod after high-pressure water washing on a polytetrafluoroethylene fixture, place the fixture into the electroplating tank, immerse the pull rod in the modified solution, turn on the air agitator, set the electroplating power supply to DC power, perform constant temperature electroplating, turn off the power, remove the fixture, and clean it with deionized water.

6. The surface treatment method for the intermediate tie rod of a mud pump according to claim 1, characterized in that, The preparation of the modified liquid includes the following steps: B1. Mix nano-alumina and anhydrous ethanol, add γ-aminopropyltriethoxysilane and stir, add hydrochloric acid and stir to obtain a mixture; vacuum dry the mixture to obtain modified nano-alumina; B2. The modified nano-alumina and deionized water are mixed and ultrasonically dispersed to obtain a modified nano-alumina suspension; B3. Mix sodium tungstate and deionized water and stir, add cerium nitrate and stir, add sodium hydroxide and stir, add γ-glycidyl etheroxypropyltrimethoxysilane solution and stir to obtain modified sodium tungstate solution; B4. Add deionized water to the electrolytic cell, then add citric acid, potassium sodium tartrate and sodium acetate in sequence and stir. Add nickel sulfate and modified sodium tungstate solution and stir. Add sodium hypophosphite and sodium dodecyl sulfate and stir. Add modified nano alumina suspension and stir. Add dilute sulfuric acid aqueous solution and stir. Filter with a filter screen to remove impurities and obtain the modified solution.

7. The surface treatment method for the intermediate tie rod of a mud pump according to claim 6, characterized in that: The solid-liquid ratio of nano-alumina and anhydrous ethanol in B1 is 1 g: 20 mL; the mass ratio of nano-alumina and γ-aminopropyltriethoxysilane is 1: 0.02-0.

03. The solid-liquid ratio of modified nano-alumina and deionized water in B2 is 1g:1L.

8. The surface treatment method for the intermediate tie rod of a mud pump according to claim 6, characterized in that, The mass ratio of sodium tungstate to deionized water in B3 is 1:5; The mass ratio of sodium tungstate to cerium nitrate is 1:0.005-0.01; The mass ratio of the sodium tungstate and γ-glycidyl etheroxypropyltrimethoxysilane solution is 1:0.018; The γ-glycidoxypropyltrimethoxysilane solution is a mixture of γ-glycidoxypropyltrimethoxysilane and anhydrous ethanol at a mass ratio of 1:

5.

9. The surface treatment method for the intermediate tie rod of a mud pump according to claim 6, characterized in that, The solid-liquid ratio of the deionized water, citric acid, potassium sodium tartrate, sodium acetate, nickel sulfate, modified sodium tungstate solution, sodium hypophosphite, sodium dodecyl sulfate, and modified nano-alumina suspension in B4 is 100L:3.5kg:2.5kg:1.2kg:9kg:12.5L:1.2kg:0.08kg:10L.

10. The surface treatment method for the intermediate tie rod of a mud pump according to claim 1, characterized in that, The method for post-processing the electroplated tie rod in S3 is as follows: the electroplated tie rod is placed in an aging furnace for treatment, the treated tie rod is placed in a dehydrogenation furnace for annealing, the annealed tie rod is rough polished with diamond polishing paste, then fine polished with diamond polishing paste, and the polishing paste is removed by wiping with anhydrous ethanol after polishing.

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