Method for improving corrosion resistance and wear resistance of metal surface and application

Abstract

The invention belongs to the technical field of corrosion resistance and wear resistance of metal materials, and particularly relates to a method for improving corrosion resistance and wear resistance of a metal surface and application. The method comprises the following steps: preparing a catalytic oxidant, wherein the required materials comprise nano ferroferric oxide powder, inorganic materials such as copper, manganese and molybdenum, polyvinyl alcohol, cane sugar and the like in percentage by mass; and conditions are easy to realize, the cost is low, and the catalyst is environment-friendly and green. Synergistic permeation of nitrogen and oxygen elements is initiated and promoted through the prepared catalytic oxidizing agent, so that a composite permeation layer structure of an inner nitriding layer and an outer oxidation layer is formed on the metal surface, a spinel type ferroferric oxide oxidation film is compact and continuous, corrosive media such as chloride ions and water can be effectively blocked, and the corrosion resistance is remarkably improved. When the composite material is applied to the hydraulic piston rod, the corrosion resistance and the wear resistance of the piston rod are enhanced, so that the piston rod can better bear mechanical loads in a severe marine environment and is not easily eroded by seawater, and the corrosion resistance, the wear resistance and the like of the piston rod are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of corrosion and wear resistance of metal materials, and particularly relates to a method for improving the corrosion and wear resistance of a metal surface and application thereof. BACKGROUND

[0002] As the core executive component of the ship hydraulic system, the reliability of the hydraulic cylinder directly affects the safety of ship control and operation. As the core component of the hydraulic cylinder, the piston rod bears the key task of energy conversion and power transmission in ship engineering, and is the core component of the steering control system, deck machinery, anchoring system and life-saving equipment, and is also one of the important guarantees for the safety and reliability of the ship.

[0003] Corrosion and wear will seriously affect the normal use of the piston rod, and even endanger the normal operation of the equipment. If the piston rod fails, it may cause the gate to fail to open or close normally, thereby affecting the normal operation of the ship passing or water level regulation. In severe cases, it may also cause leakage of hydraulic oil, damage the structure of the hydraulic cylinder, and further cause the gate to fail, threatening the safety and reliability of the ship lock, and even causing a major accident. In addition, due to the special nature of the ship lock facility, it is difficult to repair and replace the hydraulic piston rod, which requires a lot of time and labor and material costs, and also has a great impact on the normal operation of the ship lock system. Due to the special area of the piston rod of the coastal ship lock, which is applied in the sea spray area, the failure mode of the piston rod is different from that in other environments. In the marine environment, corrosion failure and wear failure are the main failure modes of the piston rod of the coastal ship lock hoist. Due to the high salt content of seawater and the high humidity in the coastal air, a water film rich in chloride ions is easily formed on the surface of the piston rod. The water film will accelerate the corrosion process of the metal, thereby making the corrosion failure of the piston rod more serious. At the same time, the piston rod of the coastal ship lock bears a large load, and after the water film dries, salt particles are formed on the surface of the piston rod, and the particles in the seawater such as sand will impact the surface of the piston rod to form abrasive wear. Therefore, the corrosion and wear resistance of the piston rod for marine use has higher performance requirements.

[0004] Although the existing piston rod surface treatment technology can provide certain corrosion and wear resistance, the hexavalent chromium produced by electroplating is harmful to the human body, the coating prepared by thermal spraying is mainly mechanically bonded, and the coating preparation process is more, the cost is higher, the laser cladding preparation efficiency is low, the economic benefit is poor, and other problems. In addition, the corrosion factors such as chloride ions and salt spray in the marine environment, and the salt particles formed after the water film dries, seriously affect the corrosion and wear resistance of the piston rod. Therefore, the preparation of a dense ceramic film is the key to solving corrosion and wear resistance.

[0005] While existing technologies can enhance hardness and wear resistance to some extent, their protective effect remains limited for piston rods exposed to harsh marine environments for extended periods. Existing nitrogen-oxygen co-diffusion processes, such as those using water vapor, ammonia, and oxygen, can improve the corrosion resistance of the surface oxide layer, but fail to form a dense oxide layer, and the surface layer's mechanical properties remain poor, failing to meet the requirements for long-term use. Patent CN118910617A discloses a surface treatment method for improving metal properties, as well as wear-resistant and corrosion-resistant metal materials, workpieces, and applications, employing technologies such as ultrasonic rolling and arc nitriding. This process is complex, increases production costs, and is prone to producing uneven thickness or brittle phases in the surface compound layer. Patent CN119243050A discloses a salt spray-resistant steel, its preparation method, and its applications, using nitrogen-oxygen co-diffusion technology to form a 3μm-5μm oxide layer. However, it fails to form a dense, uniform oxide layer on the surface, resulting in limited improvement in corrosion resistance and poor mechanical properties. Summary of the Invention

[0006] The problem to be solved by the present invention is to provide a method and application for improving the corrosion and wear resistance of metal surfaces. By using a specific catalyst to initiate and promote the synergistic penetration of nitrogen and oxygen elements, a composite penetration layer structure of "inner nitrided layer + outer oxide layer" is formed on the metal surface. The oxide layer is composed of a single spinel-type Fe3O4 phase, which significantly improves the resistance to marine corrosion and wear resistance.

[0007] The technical solution adopted is as follows:

[0008] A method for improving the corrosion and wear resistance of metal surfaces specifically includes the following steps:

[0009] (1) Preparation of the catalytic oxidant, including the following steps:

[0010] a. Prepare a mixed solution of deionized water and anhydrous ethanol, and disperse it ultrasonically or stir it to form a homogeneous mixture;

[0011] b. Add polyvinyl alcohol and sucrose to the mixture, turn on the stirring mode, and heat and stir in a water bath until completely dissolved; while continuing to stir, slowly add nano-iron oxide powder one by one, and continue to stir until uniform.

[0012] c. Add copper nitrate trihydrate and manganese acetate in sequence, and continue stirring; then add ammonium molybdate tetrahydrate, and continue stirring to ensure complete and uniform dispersion; add silica sol while stirring continuously, and continue stirring to make the silica sol uniformly dispersed in ethanol to form a stable dispersion system;

[0013] Continue stirring until there is no sediment or separation, to obtain a catalyst slurry;

[0014] d. After sealing the catalyst slurry, allow it to stand and mature to ensure the system is uniform and stable;

[0015] (2) The catalytic nitrogen-oxygen co-diffusion method has the following steps:

[0016] a. A pit-type nitriding furnace (with an effective diameter of 0.8 meters wide and 1.5 meters high) is used. After degreasing, the metal parts are vertically suspended in the center of the furnace, so that they are in a uniform thermal field and airflow area with the air duct circulation.

[0017] b. The prepared catalytic oxidant is dripped into the furnace in liquid form through a drip pipe installed on the top of the furnace cover to ensure that the liquid is fully atomized in a high-temperature environment. The catalytic oxidant contains iron oxide as a high specific surface area carrier. The catalyst particles formed by atomization are uniformly contacted and attached to the metal surface under the carrying of hot air flow. Relying on physical adsorption and preliminary drying effect, a catalyst catalytic layer is gradually deposited on the surface.

[0018] After the dripping is completed, continue to maintain the circulating air so that the catalyst layer is pre-dried under the action of hot air and the adhesion strength is enhanced;

[0019] c. Introduce ammonia gas into the pit-type nitriding furnace to maintain positive pressure and remove air from the furnace;

[0020] d. When the temperature reaches the expected temperature of 460℃~600℃, adjust the flow rate of ammonia and oxygen, start timing for nitrogen-oxygen co-osmosis, set the pressure and maintain the temperature;

[0021] e. After nitrogen-oxygen co-infiltration is completed, close the oxygen valve and begin cooling. During the cooling process, keep the airflow open to maintain positive pressure, then close the ammonia valve, and then introduce nitrogen to maintain positive pressure and purge. After cooling, remove the metal parts.

[0022] Preferably, in step (1), the required materials, by mass percentage, include 3.0-15.0% nano-ferric oxide powder, 8.0%-12.0% copper nitrate trihydrate, 0.5%-3.0% manganese acetate, 0.5%-2.0% ammonium molybdate tetrahydrate, 2.0-4.0% polyvinyl alcohol, 2.0%-3.0% sucrose, 3.0%-10.0% silica sol, 40.0%-60.0% deionized water, and 20.0%-40.0% anhydrous ethanol.

[0023] Preferably, in step (1), the volume ratio of deionized water to anhydrous ethanol is 5:2 to 3.

[0024] Preferably, in step (1), the water bath heating temperature is 60-70°C, and the water bath is heated and stirred for 20-40 minutes.

[0025] Preferably, in step (1), the mixture is left to stand at room temperature for 8 to 12 hours to mature.

[0026] Preferably, in step (2), the dripping rate of the catalytic oxidant varies depending on the furnace charge, such as when the furnace charge density is 20–100 kg / m³. 3 The flow rate is 0.5–0.8 mL / min; when the furnace charge density is 100–200 kg / m³. 3 The flow rate is 0.8–1.2 ml / min; when the furnace charge is >200 kg / m³ 3 The flow rate is 1.2 to 1.5 mL / min; the furnace temperature is maintained between 60 and 120°C, and the circulating fan inside the furnace operates at 800 to 1200 rpm.

[0027] Preferably, in step (2), the catalytic oxidant dripping rate is controlled at 0.5 to 1.5 mL / min according to the furnace loading amount; the furnace temperature is maintained between 60 and 120°C; and the furnace circulating fan operates at 800 to 1500 rpm.

[0028] Preferably, in step (2), the atomization deposition process lasts for 20 to 40 minutes, and after the dripping is completed, the circulating air continues for 10 to 15 minutes.

[0029] Preferably, in step (2), the ammonia flow rate is adjusted to 40 to 66 times the furnace volume per hour, and the oxygen flow rate is 27 to 53 times the furnace volume per hour.

[0030] Preferably, in step (2), during nitrogen-oxygen co-percolation, the percolation atmosphere pressure is set to 1-2 kPa, and the temperature is maintained for 2-5 hours.

[0031] Preferably, in step (2), after the nitrogen-oxygen co-percolation is completed, the oxygen valve is closed and the temperature is lowered; during the cooling process, the airflow is kept open to maintain positive pressure, the temperature is lowered to 350°C and the ammonia valve is closed, then nitrogen is introduced to maintain positive pressure and purging is performed, the temperature is lowered to 150°C, the furnace cover is opened and the metal parts are taken out.

[0032] This invention discloses a method for improving the corrosion and wear resistance of metal surfaces. Its application in metal parts, especially in hydraulic piston rods, is applicable not only to marine vessels but also to the automotive and aerospace industries, enhancing the corrosion resistance and wear resistance of piston rods.

[0033] This invention employs a specific catalyst formulation (composed of nano-ferric oxide powder, copper nitrate, potassium permanganate or manganese dioxide, ammonium molybdate, polyvinyl alcohol, sucrose, silica sol, anhydrous ethanol, etc.) to promote a nitrogen-oxygen co-diffusion reaction at high temperature, effectively improving the quality of the surface infiltration layer. Compared with traditional atmosphere nitriding or oxidation, this catalyst-assisted infiltration process results in a conventional oxide layer, typically a mixed phase oxide layer of ferric oxide and ferric oxide, which is prone to electrochemical corrosion in marine environments and has limited corrosion resistance. In contrast, this catalytic nitrogen-oxygen co-diffusion process achieves higher infiltration efficiency, a more stable oxide film structure, and forms a multi-layer composite coating. Furthermore, the oxide layer forms a uniform, single-phase ferric oxide ceramic oxide layer, which is insensitive to chloride ions and does not undergo chemical corrosion, significantly improving the coating's corrosion resistance.

[0034] This invention utilizes a catalytic nitrogen-oxygen co-diffusion process to form a composite coating, comprising an outer layer of magnetite oxide and an inner layer of nitride. This results in a single-phase, structurally stable spinel-type magnetite oxide film. This dense and continuous layer effectively blocks corrosive media such as chloride ions and moisture, significantly improving corrosion resistance. This unique composite coating structure effectively combines the advantages of nitriding and oxidation, effectively blocking corrosive media while possessing high hardness and wear resistance, thus optimizing the functionality and stability of the piston rod surface.

[0035] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0036] 1) Traditional nitriding followed by oxidation processes results in an oxide layer that is a mixture of ferric oxide and magnetite. The multiphase interface easily forms electrochemical corrosion microcells, accelerating chloride ion penetration. Furthermore, the oxide layer has low density (porosity > 5%), limiting its protective effect in marine environments. This invention utilizes an integrated catalytic nitrogen-oxygen co-diffusion process to generate a single spinel-type magnetite phase modified layer on the metal surface. This oxide layer is dense, structurally stable, and the single phase avoids the formation of electrochemical corrosion microcells, exhibiting excellent chemical inertness (stable against marine chloride ions). This significantly reduces the rate of metal corrosion, extends service life, and substantially improves the corrosion resistance of the workpiece surface.

[0037] 2) The neutral salt spray test life of piston rods in traditional nitriding and post-nitriding oxidation processes is generally ≤500 hours, while the multi-layer diffusion structure formed by the nitrogen-oxygen co-diffusion process not only improves the surface hardness (780 HV) 0.05 Furthermore, it enhances the metal's corrosion resistance (no rust after more than 2000 hours of neutral salt spray testing), enabling the piston rod to effectively prevent chloride ion corrosion in harsh marine environments, thus improving its reliability and safety.

[0038] 3) Simplified Process and Cost Advantages: Compared with existing multi-step complex processes (such as oxidation after nitriding, multiple temperature increases and decreases, with a total time ≥10 hours), the catalytic nitrogen-oxygen co-infiltration process of this invention does not require multiple steps or high-energy-consuming equipment. The temperature of this process is controlled within the range of 460℃~600℃. Through the catalyst promoting the synergistic infiltration of nitrogen and oxygen elements, it not only improves production efficiency (≤5 hours) but also reduces production costs, resulting in high economic benefits. Furthermore, the catalyst and reaction atmosphere do not contain any toxic metals or volatile pollutants, making it more environmentally friendly. Attached Figure Description

[0039] Figure 1 Metallographic structure (a) and microhardness diagram (b) of the piston rod cross-section processed by the method of the present invention in Example 1.

[0040] Figure 2 The images show SEM (a) images of the piston rod surface and SEM (b) images of the cross section processed by the method of the present invention in Example 1.

[0041] Figure 3 The images show the EDS diagram and O and N element diagrams of the piston rod cross-section processed by the method of the present invention in Example 1.

[0042] Figure 4 XRD pattern (a) and Raman pattern (b) of the piston rod phase detected by the method of the present invention in Example 1.

[0043] Figure 5 The image shows a photograph of the piston rod treated according to the method of the present invention in Example 1 after its corrosion resistance was evaluated in a neutral salt spray test.

[0044] Figure 6 This is an evaluation diagram of the electrochemical corrosion resistance of a piston rod treated using the method of the present invention in Example 1. Detailed Implementation

[0045] The accompanying drawings are for illustrative purposes only; to make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of this application can be combined with each other. Many specific details are set forth in the following description to provide a thorough understanding of the present invention; however, the present invention may also be implemented in other ways different from those described herein, and therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0046] Example 1: A method for improving the corrosion and wear resistance of metal surfaces, specifically including the following steps:

[0047] (1) Preparation of catalytic oxidant: The required materials by mass percentage include: nano-iron oxide powder: 6.0%, copper nitrate trihydrate: 8.0%, manganese acetate reagent: 1.5%, ammonium molybdate tetrahydrate: 1.0%, polyvinyl alcohol: 2.0%, sucrose: 2.5%, silica sol (silica solid content 30%): 4.0%, deionized water: 45.0%, and anhydrous ethanol: 30.0%.

[0048] The preparation method using catalytic oxidants includes the following steps:

[0049] a. Prepare a mixed solution of deionized water and anhydrous ethanol at a volume ratio of 3:2; stir for 5 minutes to form a homogeneous mixture.

[0050] b. Add polyvinyl alcohol and sucrose to the mixture, start stirring, and heat and stir in a water bath at 60-70°C for 30-50 minutes until completely dissolved; while continuing to stir, slowly add the pre-weighed iron oxide powder and continue stirring until uniform.

[0051] c. Add copper nitrate trihydrate and manganese acetate reagent in sequence, and continue stirring; then add ammonium molybdate tetrahydrate, and continue stirring for 10 minutes to ensure complete and uniform dispersion;

[0052] Slowly add the predetermined mass of silica sol while stirring continuously, and continue stirring for 20 minutes to ensure that the silica sol is uniformly dispersed in ethanol to form a stable dispersion system.

[0053] If the viscosity of the system is too high, add an appropriate amount of deionized water and anhydrous ethanol to adjust the viscosity; continue stirring for 10 minutes to make the solution fully homogeneous; take a small amount of solution and let it stand, and observe whether there is any precipitation or layering, which means it is qualified; if precipitation occurs, continue stirring or ultrasonic dispersion until homogeneous to obtain catalyst slurry.

[0054] d. After sealing the catalyst slurry, allow it to stand at room temperature for 10 hours to mature, so as to ensure that the system is uniform and stable.

[0055] (2) The catalytic nitrogen-oxygen co-percolation method is as follows.

[0056] a. A pit-type nitriding furnace is used (with an effective internal diameter of 0.8 meters wide and 1.5 meters high). The furnace body has a top cover and is equipped with high-temperature electric heating elements, a vertical lifting and hoisting mechanism, a workpiece support, and a heat-resistant circulating fan inside the furnace. After degreasing, the piston rod is vertically suspended in the center of the furnace, ensuring that it is in a relatively uniform thermal and airflow area with the air duct circulation.

[0057] b. The prepared catalytic oxidant is slowly dripped into the furnace chamber in liquid form through a precision high-temperature resistant dripping tube installed on the upper part of the furnace cover. The dripping tube is connected to a controllable drip rate delivery system, and the catalyst dripping rate is controlled at 1.5 ml / min to ensure that the liquid is fully atomized in the high-temperature environment. The furnace temperature is maintained between 60 and 120°C, and the circulating fan inside the furnace operates at 1200 rpm to form a uniform hot air flow field, which helps the dripped catalyst liquid to be rapidly atomized in the space. Since the catalyst contains iron(III) oxide as a high specific surface area carrier, the atomized catalyst particles are uniformly contacted and attached to the metal surface of the piston rod under the carrying of the hot air flow. Relying on physical adsorption and preliminary drying effect, a catalytic layer is gradually deposited on the surface to form a catalytic layer.

[0058] The entire adhesion process lasts 30 minutes. After the dripping is completed, the circulating air continues for 15 minutes to pre-dry the catalyst layer under the action of hot air and enhance the adhesion strength.

[0059] c. Introduce ammonia gas into the pit-type nitriding furnace to maintain positive pressure and remove air from the furnace.

[0060] d. After turning on the incineration heater and circulating fan, start heating. At 500℃, adjust the gas flow rate to maintain positive pressure. When the temperature reaches the expected temperature of 580℃, adjust the ammonia flow rate to 53 times the furnace volume / hour and the oxygen flow rate to 40 times the furnace volume / hour. Start timing for nitrogen-oxygen co-infiltration. Set the infiltration atmosphere pressure to 2KPa and keep it at that temperature for 5 hours.

[0061] e. After nitrogen-oxygen co-infiltration is completed, close the oxygen valve and begin cooling. During the cooling process, keep the airflow open and maintain positive pressure. When the temperature drops to 350°C, close the ammonia valve, then introduce nitrogen to maintain positive pressure and purge. When the temperature drops to 150°C, open the furnace cover and remove the piston rod sample.

[0062] like Figure 1 As shown, catalytic nitrogen-oxygen co-diffusion was performed by heating to 580℃ and holding for 5 hours. Figure 1 (a) is a cross-sectional metallographic diagram. Figure 1 (b) shows the microhardness diagram. It can be seen that the oxide layer is dense, with a thickness of 9.66 μm, and the nitride layer is 29.8 μm thick. The hardness gradient is relatively gentle, with a surface hardness of 780 HV. 0.05 The infiltration depth is 700μm.

[0063] like Figure 2 As shown, catalytic nitrogen-oxygen co-diffusion was performed by heating to 580℃ and holding for 5 hours. Figure 2 (a) is a surface SEM image. Figure 2 (b) is a cross-sectional SEM image. It can be seen that a dense spinel structure is formed on the surface of the oxide layer, with no obvious pores. The oxide layer and the nitride layer are tightly bonded in the cross-section.

[0064] like Figure 3As shown, catalytic nitrogen-oxygen co-diffusion was performed by heating to 580℃ and holding for 5 hours. From top to bottom, the images are the EDS plot, O, and N elemental plots obtained from the linear scanning cross-section analysis.

[0065] like Figure 4 As shown, catalytic nitrogen-oxygen co-diffusion was performed by heating to 580℃ and holding for 5 hours. Figure 4 (a) is the X-ray diffraction pattern. Figure 4 (b) Raman spectroscopy analysis. The structure can be seen from X-ray diffraction and Raman spectroscopy analysis, and the oxide layer is composed of a single Fe3O4 phase.

[0066] like Figure 5 The image shows a catalytic nitrogen-oxygen co-diffusion test at 580℃ for 5 hours, conducted under neutral salt spray conditions. No significant corrosion was observed after more than 3600 hours of testing in a neutral salt spray chamber with 5% NaCl solution.

[0067] Comparative Example 1: Nitriding results in a loose compound layer composed of multiple phases, which undergoes electrochemical corrosion and exhibits poor corrosion resistance.

[0068] Comparative Example 2: After nitriding and oxidation, the multiple processes resulted in a loose oxide layer with weak interfacial bonding. Furthermore, the oxide layer consisted of two phases, Fe3O4 and Fe2O3, which had poor corrosion resistance.

[0069] like Figure 6 As shown, the electrochemical corrosion resistance was evaluated after catalytic nitrogen-oxygen co-diffusion at 580℃ for 5 hours. In a 1.5% NaCl solution, the corrosion voltage was measured to be 0.111V. SCE The corrosion current density is 9.49 × 10⁻⁶. -10 A / cm 2 .

[0070] The corrosion voltage and corrosion current density of the piston rods obtained by the catalytic nitrogen-oxygen co-diffusion process in Example 1 of the present invention and the processes of Comparative Examples 1 and 2 were tested in the electrochemical corrosion resistance test, as shown in Table 1.

[0071] Table 1 compares the corrosion voltage and corrosion current density of piston rods treated using the methods of Example 1 and Comparative Examples 1-2.

[0072] Example Catalytic nitrocarburizing Nitriding Post-nitriding oxidation E corr (V SCE )]]> 0.111 -0.794 -0.413 I corr (A / cm 2 )]]> 9.49 x 10 -10 ]] 9.9 x 10 -7 ]] 1.43 x 10 -5 ]]>

[0073] As shown in Table 1, the catalytic nitrogen-oxygen symbiotic corrosion current density is much lower than that of nitriding and post-nitriding oxidation processes, resulting in a slower corrosion rate. The corrosion voltage is higher than that of nitriding and post-oxidation processes, leading to better surface stability.

[0074] Example 2, a method for improving the corrosion and wear resistance of metal surfaces, specifically includes the following steps:

[0075] The materials required for preparing the catalytic oxidant, by mass percentage, include: nano Fe3O4 powder: 3.0%, copper nitrate reagent: 8.0%, manganese acetate reagent: 0.5%, ammonium molybdate reagent: 1.5%, polyvinyl alcohol reagent: 2.0%, sucrose reagent: 2.0%, silica sol reagent (silica solid content 30%): 3.0%, deionized water: 50%, and anhydrous ethanol reagent: 30%.

[0076] A pit-type nitriding furnace (with an effective internal diameter of 0.8 meters wide and 1.5 meters high) was used, with the catalyst dripping rate controlled at 0.5 mL / min to ensure complete atomization of the liquid in a high-temperature environment. The furnace temperature was maintained between 60 and 120°C, and the circulating fan inside the furnace operated at 600 rpm to create a uniform hot air flow field, which facilitated rapid atomization of the dripped catalyst liquid in the space. Because the catalyst contains iron(III) oxide as a high specific surface area carrier, the atomized catalyst particles were uniformly contacted and adhered to the metal surface of the piston rod under the carrying effect of the hot air flow. Relying on physical adsorption and preliminary drying effects, a catalyst layer was gradually deposited on the surface to form a catalyst layer.

[0077] The entire adhesion process lasts for 20 minutes. After the dripping is completed, continue to maintain the circulating air for 10 minutes to pre-dry the catalyst layer under the action of hot air and enhance the adhesion strength.

[0078] After turning on the incineration heating and circulating fan, the temperature is raised. At 500℃, the gas flow rate is adjusted to maintain positive pressure. When the temperature reaches the expected temperature of 550℃, the ammonia flow rate is adjusted to 40 times the furnace volume per hour and the oxygen flow rate is adjusted to 27 times the furnace volume per hour. Timing is started for nitrogen-oxygen co-infiltration. The infiltrated gas atmosphere pressure is set to 2 kPa, and the temperature is maintained for 2 hours.

[0079] Other areas not mentioned are the same as in Example 1.

[0080] Example 3: A method for improving the corrosion and wear resistance of metal surfaces, specifically including the following steps:

[0081] The materials required for preparing the catalytic oxidant, by mass percentage, include: 12.0% nano-iron oxide powder, 9.0% copper nitrate reagent, 3.0% manganese acetate reagent, 2.0% ammonium molybdate reagent, 4.0% polyvinyl alcohol reagent, 3.0% sucrose reagent, 7.0% silica sol reagent (SiO2 solid content 30%), 40.0% deionized water, and 20.0% anhydrous ethanol reagent. If the viscosity of the system is too high after thorough stirring, add deionized water and anhydrous ethanol to adjust the viscosity.

[0082] A pit-type nitriding furnace (with an effective internal diameter of 0.8 meters wide and 1.5 meters high) was used, with the catalyst dripping rate controlled at 0.8 mL / min to ensure complete atomization of the liquid in a high-temperature environment. The furnace temperature was maintained between 60 and 120°C, and the circulating fan inside the furnace operated at 800 rpm to create a uniform hot air flow field, which facilitated rapid atomization of the dripped catalyst liquid in the space. Because the catalyst contains iron(III) oxide as a high specific surface area carrier, the atomized catalyst particles were uniformly contacted and adhered to the metal surface of the piston rod under the carrying effect of the hot air flow. Relying on physical adsorption and preliminary drying effects, a catalyst layer was gradually deposited on the surface to form a catalyst layer.

[0083] The entire adhesion process lasts 30 minutes. After the dripping is completed, the circulating air continues for 15 minutes to pre-dry the catalyst layer under the action of hot air and enhance the adhesion strength.

[0084] After turning on the incineration heating and circulating fan, the temperature is raised. At 500℃, the gas flow rate is adjusted to maintain positive pressure. When the temperature reaches the expected temperature of 600℃, the ammonia flow rate is adjusted to 66 times the furnace volume per hour and the oxygen flow rate is adjusted to 53 times the furnace volume per hour. Timing is started for nitrogen-oxygen co-infiltration. The infiltrated gas atmosphere pressure is set to 2 kPa, and the temperature is maintained for 3 hours.

[0085] Other areas not mentioned are the same as in Example 1.

[0086] Example 4: A method for improving the corrosion and wear resistance of metal surfaces, specifically including the following steps:

[0087] The materials required for preparing the catalytic oxidant, by mass percentage, include: 8.0% nano-iron oxide powder, 8.0% copper nitrate, 2.5% manganese acetate reagent, 1.5% ammonium molybdate, 3% polyvinyl alcohol, 3.0% sucrose reagent, 4.0% silica sol (30% silica solid content), 45.0% deionized water, and 25.0% anhydrous ethanol. If the viscosity of the system is too high after thorough stirring, add deionized water and anhydrous ethanol to adjust the viscosity.

[0088] A pit-type nitriding furnace (with an effective internal diameter of 0.8 meters wide and 1.5 meters high) was used, with the catalyst dripping rate controlled at 1.2 mL / min to ensure complete atomization of the liquid in a high-temperature environment. The furnace temperature was maintained between 60 and 120°C, and the circulating fan inside the furnace operated at 1000 rpm to create a uniform hot air flow field, which facilitated rapid atomization of the dripped catalyst liquid in the space. Because the catalyst contains iron(III) oxide as a high specific surface area carrier, the atomized catalyst particles were uniformly contacted and adhered to the metal surface of the piston rod under the carrying effect of the hot air flow. Relying on physical adsorption and preliminary drying effects, a catalyst layer was gradually deposited on the surface to form a catalyst layer.

[0089] The entire adhesion process lasts for 40 minutes. After the dripping is completed, the circulating air continues for 15 minutes to pre-dry the catalyst layer under the action of hot air and enhance the adhesion strength.

[0090] After turning on the incineration heating and circulating fan, the temperature is raised. At 500℃, the gas flow rate is adjusted to maintain positive pressure. When the temperature reaches the expected temperature of 580℃, the ammonia flow rate is adjusted to 40 times the furnace volume per hour and the oxygen flow rate is adjusted to 46 times the furnace volume per hour. Timing is started for nitrogen-oxygen co-infiltration. The infiltrated gas atmosphere pressure is set to 2 kPa, and the temperature is maintained for 5 hours.

[0091] Other areas not mentioned are the same as in Example 1.

[0092] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for improving the corrosion and wear resistance of metal surfaces, characterized in that, Specifically, the steps include the following: (1) Preparation of the catalytic oxidant, including the following steps: a. Prepare a mixed solution of deionized water and anhydrous ethanol, and disperse it ultrasonically or stir it to form a homogeneous mixture; b. Add polyvinyl alcohol and sucrose to the mixture and heat and stir in a water bath until completely dissolved; add nano Fe3O4 powder while continuing to stir and stir until homogeneous. c. Add copper nitrate trihydrate, manganese acetate, and ammonium molybdate tetrahydrate in sequence, and continue stirring to ensure complete and uniform dispersion; add silica sol while stirring continuously to form a stable dispersion system until there is no precipitation or stratification, and obtain the catalyst slurry; d. After sealing the catalyst slurry, allow it to stand and mature. (2) The catalytic nitrogen-oxygen co-diffusion method includes the following steps: a. A pit-type nitriding furnace is used. After degreasing, the metal parts are vertically suspended in the center of the furnace so that they are in a uniform thermal field and airflow area with the air duct circulation. b. The prepared catalytic oxidant is dripped into the furnace in liquid form through a drip pipe installed on the top of the furnace cover to ensure that the liquid is fully atomized in a high-temperature environment. The atomized catalyst particles are uniformly contacted and attached to the metal surface under the carrying of hot air flow, and gradually deposited on the surface to form a catalyst catalytic layer. After the dripping is completed, continue to maintain the circulating air so that the catalyst layer is pre-dried under the action of hot air and the adhesion is enhanced; c. Introduce ammonia gas into the pit-type nitriding furnace to maintain positive pressure and remove air from the furnace; d. When the temperature reaches the expected temperature of 460-600℃, adjust the flow rates of ammonia and oxygen, start timing for nitrogen-oxygen co-osmosis, set the pressure and maintain the temperature; e. After nitrogen-oxygen co-infiltration is completed, close the oxygen valve and begin cooling. During the cooling process, keep the airflow open to maintain positive pressure, then close the ammonia valve, and then introduce nitrogen to maintain positive pressure and purge. After cooling, remove the metal parts.

2. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (1), the required materials, by mass percentage, include 3.0-15.0% nano-ferric oxide powder, 8.0%-12.0% copper nitrate trihydrate, 0.5%-3.0% manganese acetate, 0.5%-2.0% ammonium molybdate tetrahydrate, 2.0-4.0% polyvinyl alcohol, 2.0%-3.0% sucrose, 3.0%-10.0% silica sol, 40.0%-60.0% deionized water, and 20.0%-40.0% anhydrous ethanol.

3. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (1), the volume ratio of deionized water to anhydrous ethanol is 5:2 to 3.

4. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (1), the water bath heating temperature is 60-70℃, and the water bath is heated and stirred for 20-40 minutes.

5. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (1), the mixture is left to stand at room temperature for 8 to 12 hours to mature.

6. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (2), the dripping rate of the catalytic oxidant varies depending on the furnace loading rate, such as when the loading density is 20–100 kg / m³. 3 The flow rate is 0.5–0.8 mL / min; when the furnace charge density is 100–200 kg / m³. 3 The flow rate is 0.8–1.2 ml / min; when the furnace charge is >200 kg / m³ 3 The flow rate is 1.2 to 1.5 mL / min; the furnace temperature is maintained between 60 and 120°C, and the circulating fan inside the furnace operates at 800 to 1200 rpm.

7. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (2), the atomization deposition process lasts for 20 to 40 minutes, and after the dripping is completed, the circulating air continues for 10 to 15 minutes.

8. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (2), the ammonia flow rate is adjusted to 40 to 66 times the furnace volume per hour, and the oxygen flow rate is 27 to 53 times the furnace volume per hour.

9. The method for improving the corrosion and wear resistance of metal surfaces according to claim 1, characterized in that, In step (2), during nitrogen-oxygen co-percolation, the percolation atmosphere pressure is set to 1-2 kPa, and the temperature is maintained for 2-5 hours. After nitrogen-oxygen co-percolation, the oxygen valve is closed and the temperature is lowered. During the cooling process, the airflow is kept open to maintain positive pressure. When the temperature drops to 350°C, the ammonia valve is closed, and then nitrogen is introduced to maintain positive pressure and purge. When the temperature drops to 150°C, the furnace cover is opened, and the metal parts can be removed after cooling.

10. The application of the method for improving the corrosion and wear resistance of metal surfaces as described in any one of claims 1-9 in metal parts.

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