High-wear-resistance air compressor crankshaft and machining method thereof

Abstract

The machining method is characterized by comprising the following operation steps of pretreatment of the surface layer of a front end shaft, pretreatment of the surface layer of a crank arm, pretreatment of the surface layer of a rear end shaft and overall assembly of the crankshaft. The step of surface layer pretreatment of the front end shaft, the step of surface layer pretreatment of the crank arm and the step of surface layer pretreatment of the rear end shaft respectively comprise an oxynitriding method; a salt bath is adopted in the oxynitriding method, and the formula of the salt bath comprises, by weight, 30%-50% of urea, 20%-40% of potassium nitrate, 10%-30% of sodium carbonate and 5%-15% of lanthanum trifluoride. The surface layers of all parts of the crankshaft are treated, so that the abrasion resistance of the air compressor crankshaft during operation under high strength is improved, and the service life of the air compressor crankshaft during working is prolonged.

Description

Technical Field

[0001] This invention relates to the field of air compressor crankshaft machining technology, specifically a high wear-resistant air compressor crankshaft and its machining method. Background Technology

[0002] The crankshaft of an air compressor, located at the connecting rod, rotates, driving the connecting rod to cause the piston to reciprocate, converting rotation into linear motion. During operation, it withstands complex, cyclical alternating loads. Therefore, the machining process of the air compressor crankshaft is crucial to its quality and production efficiency.

[0003] Currently, air compressor crankshafts need to withstand cyclic alternating loads. Commonly used materials include 45 steel and 40Cr steel, requiring high fatigue strength and wear resistance. They are widely used in industrial fields such as drilling and extraction equipment, natural gas compression, and marine compressors. Choosing the right material is crucial for the crankshaft's performance and lifespan. Secondly, the crankshaft's structural design is necessary, including parameters such as shaft length, diameter, and shoulder width, to ensure its strength and stability. Finally, the crankshaft's machining process, procedures, and equipment selection must be determined to ensure safe and efficient machining.

[0004] Specifically, the crankshaft includes a crankshaft body, which comprises a front shaft, a crank arm, and a rear shaft connected in sequence. The front shaft is typically a solid or stepped shaft structure with keyways or threads on its surface, requiring a certain level of wear resistance. The crank arm connects the main journal and the connecting rod journal, is curved or branched, and has internal oil passages for lubrication, requiring high fatigue strength. The rear shaft ends in a flanged disc, rigidly connected to the flywheel by bolts, transmitting power to the transmission system. As a key component for power output and axial positioning, it possesses strong engagement force.

[0005] Currently, the steel used in this material possesses excellent hardenability, hot strength, wear resistance, thermal fatigue resistance, impact toughness, and thermal shock resistance. By performing surface treatment on the steel of each crankshaft component, not only can the service life of the surface be improved, but the core structure with excellent comprehensive performance can also be preserved. Summary of the Invention

[0006] This application provides a high wear-resistant air compressor crankshaft and its processing method. The purpose of this application is to treat the surface of each part of the crankshaft to improve the wear resistance of the air compressor crankshaft under high intensity operation and increase the service life of the air compressor crankshaft.

[0007] This application provides a processing method for a high wear-resistant air compressor crankshaft, characterized by the following steps: pretreatment of the front shaft surface, pretreatment of the crank arm surface, pretreatment of the rear shaft surface, and overall assembly of the crankshaft; the pretreatment of the front shaft surface, the pretreatment of the crank arm surface, and the pretreatment of the rear shaft surface all include an oxygen-nitrogen co-infiltration method; the oxygen-nitrogen co-infiltration method includes a salt bath, and the salt bath formula, by weight percentage, includes 30%-50% urea, 20%-40% potassium nitrate, 10%-30% sodium carbonate, and 5%-15% lanthanum trifluoride.

[0008] By adopting the above technical solution, this application uses the same salt bath formula for oxygen-nitrogen co-infiltration of the front shaft, crank arm, and rear shaft. Through structural adaptive design, this application's process, based on a unified salt bath, utilizes geometric differences to guide local chemical reaction paths, combined with customized post-treatment, to achieve precise control of "one agent, multiple effects." Depending on the different structures of the front shaft, crank arm, and rear shaft, and the different post-treatment methods, a front shaft with high wear resistance and corrosion resistance; a crank arm with high fatigue resistance; and a rear shaft with high sealing performance and anti-galling properties are formed. This ensures the wear resistance of the air compressor crankshaft during high-strength operation, increasing the service life of the air compressor crankshaft.

[0009] Preferably, the pretreatment of the front shaft surface includes the following steps: S1, ultrasonically cleaning the front shaft blank, followed by sandblasting and vacuum annealing to obtain a surface-cleaned front shaft blank; S2, subjecting the surface-cleaned front shaft blank to a salt bath, and performing low-temperature nitriding and high-temperature oxygen diffusion operations to form Fe3O4 and ε-Fe on the surface of the front shaft blank. 2-3 The N composite layer; in the low-temperature nitriding operation, the enclosed space is protected by argon gas; in the high-temperature oxygen diffusion operation, the enclosed space is composed of NH3 and CO2, with a gas volume ratio of NH3 to CO2 of 3:1; S3, containing Fe3O4 and ε-Fe 2-3 The front-end shaft blank of the N-composite layer is subjected to high-frequency quenching, low-temperature tempering, mechanical polishing and micro-arc oxidation to obtain a front-end shaft with surface pretreatment.

[0010] By adopting the above technical solution, since the front-end shaft is usually a solid or stepped shaft with a gentle surface curvature, the salt bath exhibits good fluidity and high oxygen diffusion efficiency during the oxygen-nitrogen co-denitrification process. In the low-temperature nitriding process, urea decomposes to generate active nitrogen [N], and LaF3 catalyzes the formation of nanoscale ε-Fe. 2-3The primary N phase; during the high-temperature oxygen diffusion process, an oxygen-rich atmosphere is introduced, and the active oxygen atoms [O] from the decomposition of potassium nitrate (KNO3) more readily react with Fe to form Fe3O4; in the low-temperature section, nitride frameworks are preferentially constructed, while in the high-temperature section, oxide / nitride composites are achieved through oxygen permeation. Then, low-temperature tempering and quenching are used to fix ε-Fe. 2-3 N, while micro-arc oxidation generates an α-Al2O3 sealing layer, increasing the Fe3O4 content. In this application, the Fe3O4 on the front-end shaft provides lubrication, reducing the coefficient of friction, and ε-Fe 2-3 N ensures high hardness, thereby reducing journal wear and improving crankshaft wear resistance.

[0011] Preferably, in the pretreatment process of the front-end shaft surface layer: the high-frequency quenching parameters are: heating surface heating rate 80-120℃ / s, target temperature 860℃±30℃; 0.1% polyvinyl alcohol aqueous solution spray cooling, pressure 0.3-0.5MPa, cooling rate ≥200℃ / s; the low-temperature tempering parameters are: vacuum tempering at 180℃±20℃, time 1-3h, heating rate ≤50℃ / h; the micro-arc oxidation parameters are: electrolyte formula (including Na2SiO3, KOH); voltage 450V, time 0.5-1.5h.

[0012] Preferably, the crank arm surface pretreatment includes the following steps: S1, ultrasonically cleaning the crank arm blank, followed by sandblasting and vacuum annealing to obtain a surface-cleaned crank arm blank; S2, subjecting the surface-cleaned crank arm blank to a salt bath and performing low-temperature nitriding and high-temperature diffusion operations to form a composite layer of Fe4N and LaN on the surface of the crank arm blank; in the low-temperature nitriding operation, the enclosed space is protected by argon gas; in the high-temperature diffusion operation, the enclosed space is NH3 and CO2, and the gas volume ratio of NH3 to CO2 is 3:1; S3, laser scanning the crank arm blank with the Fe4N and LaN composite layer, followed by gradient rolling, low-temperature tempering, and polishing to obtain a surface-treated crank arm blank.

[0013] By adopting the above technical solution, the crank arm has a curved branch structure, and salt bath retention is easily formed at the oil holes and rounded corners, which hinders oxygen diffusion; at the same time, the internal oil passages lead to rapid local heat dissipation, prolonging the residence time of nitrogen atoms, and rare earth LaF3 preferentially accumulates in the stress concentration area of ​​the crank arm, catalyzing the formation of Fe4N phase and inhibiting the formation of Fe3O4.

[0014] Furthermore, a pre-fabricated microgroove array is created using laser scanning as a stress buffer, guiding the subsequent rolling pressure to distribute evenly and preventing the nitride layer from cracking due to stress concentration. Gradient rolling then embeds Al2O3 particles into the surface to form an in-situ ceramic layer, enhancing wear resistance. Simultaneously, high pressure induces dislocation proliferation, forming a nanotwin structure that promotes the precipitation of the LaN dispersed phase and inhibits oxide formation. In this application, the LaN dispersed phase hinders dislocation slip, and the nanotwin structure inhibits crack propagation, thereby improving fatigue strength.

[0015] Preferably, in the crank arm surface pretreatment process, the laser scanning parameters are: fiber laser wavelength 1064nm, power 450-550W, scanning speed 1.5-2.5m / s, spacing 150-250μm, and depth 3-8μm; the gradient rolling parameters are: rolling force 2600-3000N; the roller type is a hard alloy roller with an Al2O3 coating; the pressing depth is 0.3mm; and the feed rate is 0.08mm / r.

[0016] Preferably, the pretreatment of the rear shaft surface includes the following steps: S1, ultrasonically cleaning the rear shaft blank, followed by sandblasting and vacuum annealing to obtain a surface-cleaned rear shaft blank; S2, subjecting the surface-cleaned rear shaft blank to a salt bath and performing low-temperature nitriding and high-temperature diffusion operations to form a composite layer with γ'-Fe4N and Cr2O3 on the surface of the rear shaft blank; in the low-temperature nitriding operation, the enclosed space is protected by argon gas; in the high-temperature diffusion operation, the enclosed space is NH3 and CO2, and the gas volume ratio of NH3 to CO2 is 1:1; S3, rolling the rear shaft blank with the composite layer of γ'-Fe4N and Cr2O3, followed by micro-arc oxidation sealing and low-temperature tempering to obtain a surface-treated rear shaft blank.

[0017] By adopting the above technical solution, the rear shaft has a flat cylindrical structure, which makes the salt bath flow uniform and the oxygen diffusion efficiency high. During the low-temperature nitriding process, urea decomposes to generate active nitrogen [N], and the Cr-rich area of ​​the matrix is ​​pre-oxidized to form Cr2O3 crystal nuclei. In addition, during the high-temperature diffusion process, the gas volume ratio of NH3 to CO2 in the closed space is 1:1. The CO2 atmosphere in the high-temperature section promotes the selective oxidation of Cr. The active oxygen [O] from the decomposition of potassium nitrate preferentially reacts with the Cr in the matrix to generate Cr2O3, which inhibits chromium depletion at the grain boundaries, that is, inhibits the precipitation of CrN. Then, γ'-Fe4N grows directionally under the nitrogen potential gradient to form a composite layer with γ'-Fe4N and Cr2O3. Cr2O3 and γ'-Fe4N form a "hard-tough synergistic" structure, which reduces the friction coefficient and enhances wear resistance and anti-galling ability.

[0018] Preferably, in the pretreatment process of the rear shaft surface: the roller rolling parameters are: roller type with Al2O3 coating; rolling force is 1000±200N; pressing depth is 0.1-0.2mm; feed rate is 0.05mm / r; cooling method is liquid nitrogen injection; the micro-arc oxidation parameters are: voltage is 450V±20V; frequency is 1000Hz; duty cycle is 30%; time is 0.5-1.5h; electrolyte formulation (including Na2SiO3, KOH, CrO3).

[0019] By employing the above technical solution, this application performs roller rolling on a rear shaft blank with a composite layer of γ'-Fe4N and Cr2O3, followed by micro-arc oxidation sealing and low-temperature tempering. The roller with an Al2O3 coating embeds Al2O3 into the metal surface during shallow rolling, reducing the coefficient of friction. Liquid nitrogen cooling then suppresses springback and stabilizes residual compressive stress. During the micro-arc oxidation sealing process, high-voltage discharge generates an α-Al2O3 ceramic layer within the surface micropores. The incorporation of CrO3 enhances density, thereby reducing adhesive wear on the rear shaft surface under high-intensity conditions and improving the engagement capability of the rear shaft.

[0020] Preferably, the overall assembly of the crankshaft includes the following steps: S1, the internal spline holes at both ends of the crank arm correspond to the crankshaft body, the crank arm is heated to 180-200℃, and quickly pressed onto the crankshaft body, forming a tight fit after cooling; S2, the front end shaft is connected to the crank arm through a tapered journal, and the keyway of the front end shaft is aligned and fixed with the timing mark of the crankshaft body; S3, a support bearing is installed between the rear end shaft and the crank arm, the inner ring of the bearing is pre-coated with high-temperature grease, and a through groove is opened in the crank arm to facilitate the connecting rod bearing to slide into the root of the journal, and is locked axially to obtain the air compressor crankshaft; S4, the air compressor crankshaft is tested on a balancing machine to calculate the residual imbalance. If it exceeds the standard, the weight is reduced by grinding the non-load-bearing surface of the crank arm.

[0021] By adopting the above technical solution, interference fit is achieved by locally heating the crank arm, avoiding overall heat treatment deformation and further increasing the service life of the air compressor crankshaft.

[0022] On the other hand, this application discloses a high wear-resistant air compressor crankshaft, which is prepared by a processing method for high wear-resistant air compressor crankshafts; the high wear-resistant air compressor crankshaft includes a crankshaft body, on which a front end shaft, a crank arm, and a rear end shaft are sequentially connected; the front end shaft, the crank arm, and the rear end shaft are all surface treated; the front end shaft is pretreated to form a first composite layer on its surface, the main components of which include Fe3O4 and ε-Fe. 2-3The crank arm is pretreated to form a second composite layer on its surface, the main components of which include Fe4N, LaN, Fe3O4 and Al2O3; the rear shaft is pretreated to form a third composite layer on its surface, the main components of which include γ'-Fe4N, Cr2O3, Fe3O4 and α-Al2O3.

[0023] By adopting the above technical solution, the main components of the first composite layer are Fe3O4 and ε-Fe. 2-3 The first composite layer, consisting of N and α-Al2O3, improves the surface hardness, wear resistance, and corrosion resistance of the crankshaft. The second composite layer, mainly composed of Fe4N, LaN, Al2O3, and Fe3O4, increases fatigue life and reduces crack propagation rate. The third composite layer, mainly composed of γ'-Fe4N, Cr2O3, Fe3O4, and α-Al2O3, reduces the friction coefficient of the crankshaft at the rear end and increases its hardness. Surface treatment is then applied to each part to improve the crankshaft's service life.

[0024] Preferably, in the first composite layer, by weight percentage: Fe3O4 is 30%-40%; ε-Fe 2-3 The second composite layer comprises, by weight percentage: N 50%-70%; α-Al₂O₃ 2%-8%; Fe₄N 0%-2%; γ'-Fe₄N 0%-2%; Al₂O₃ 0%-2%; Cr₂O₃ 0%-2%; LaN 0%-2% and the remaining unavoidable impurities; γ'-Fe₄N 65%-85%; LaN 2%-10%; Fe₃O₄ 10%-15%; Al₂O₃ 2%-8%; ε-Fe 2-3 N is 0%-2%; γ'-Fe4N is 0%-2%; α-Al2O3 is 0%-2%; Cr2O3 is 0%-2% and the remaining unavoidable impurities; in the third composite layer, by weight percentage: γ'-Fe4N is 40%-60%; Cr2O3 is 10%-30%; α-Al2O3 is 2-8%; Fe3O4 is 10%-15%; Fe4N is 0%-2%; ε-Fe 2-3 N is 0%-2%; Al2O3 is 0%-2%; LaN is 0%-2% and the remaining unavoidable impurities.

[0025] One or more technical solutions provided in this application have at least the following technical effects or advantages:

[0026] 1. This application uses the same salt bath formulation for oxygen-nitrogen co-diffusion operation on the front shaft, crank arm, and rear shaft. Through structural adaptive design, this application's process, based on a unified salt bath, utilizes geometric differences to guide local chemical reaction pathways, combined with customized post-treatment, to achieve precise control of "one agent, multiple effects."

[0027] 2. Based on the characteristic that the front-end shaft is solid or stepped, due to its gentle surface curvature, this application achieves good salt bath fluidity and high oxygen diffusion efficiency during the oxygen-nitrogen co-infiltration process. In the low-temperature section, nitride frameworks are preferentially constructed, while in the high-temperature section, oxide / nitride composites are achieved through oxygen infiltration, thereby generating Fe3O4 and ε-Fe. 2-3 N; provides lubrication through Fe3O4, reducing the coefficient of friction, ε-Fe 2-3 N ensures high hardness, thereby reducing journal wear and improving crankshaft wear resistance.

[0028] 3. Due to the curved branch structure of the crank arm, salt bath retention easily forms at oil holes and rounded corners, hindering oxygen diffusion. Simultaneously, the internal oil channels lead to rapid local heat dissipation, prolonging the residence time of nitrogen atoms. Consequently, rare earth element LaF3 preferentially accumulates in the stress concentration area of ​​the crank arm, catalyzing the formation of the Fe4N phase and inhibiting the formation of Fe3O4. Furthermore, high pressure induces dislocation proliferation, forming a nanotwin structure that promotes the precipitation of the LaN dispersed phase, thereby inhibiting crack propagation and improving fatigue strength.

[0029] 4. In this application, the rear shaft, like the front shaft, has a straight cylindrical structure, ensuring uniform salt bath flow and high oxygen diffusion efficiency. However, during the high-temperature diffusion process, the gas volume ratio of NH3 to CO2 in the enclosed space is 1:1. The CO2 atmosphere in the high-temperature section promotes the selective oxidation of Cr. The active oxygen [O] from the decomposition of potassium nitrate preferentially reacts with the matrix Cr to generate Cr2O3, inhibiting the precipitation of CrN. Then, γ'-Fe4N grows directionally under the nitrogen potential gradient, forming a composite layer with γ'-Fe4N and Cr2O3, reducing the friction coefficient and enhancing wear resistance and anti-galling ability. Detailed Implementation

[0030] This application provides a high wear-resistant air compressor crankshaft and its processing method. The purpose of this application is to treat the surface of each part of the crankshaft to improve the wear resistance of the air compressor crankshaft under high intensity operation and increase the service life of the air compressor crankshaft.

[0031] The technical solutions of this application will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] It should be noted that the terms "first," "second," etc., in the specification and claims of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or server that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or modules not explicitly listed or inherent to such processes, methods, products, or devices.

[0033] raw material:

[0034] Steel: This application mainly uses 45 steel and 40Cr steel, which are common in the prior art. The crankshaft body, front shaft blank, crank arm blank, and rear shaft blank used in this application are all forged from 45 steel.

[0035] Salt bath formulation: This application is prepared using the following materials.

[0036] Urea CAS No.: 57-13-6 Molecular weight: 60.06 Appearance: White crystals or granules Purity ≥99%;

[0037] Potassium nitrate CAS No.: 7757-79-1 Molecular weight: 101.10 Appearance: Colorless transparent crystals or white powder Purity ≥99%;

[0038] Sodium carbonate CAS No.: 497-19-8 Molecular weight: 105.99 Appearance: White powder Purity ≥99%;

[0039] LaF3 CAS No.: 13709-38-1 Molecular Weight: 195.90 Appearance: White crystalline powder Purity: 99.5%

[0040] Example

[0041] Example 1

[0042] 1. Front shaft surface pretreatment:

[0043] S1. The front-end shaft blank is ultrasonically cleaned using a 60℃ alkaline aqueous solution (containing 5% NaOH + 3% Na2CO3, pH = 11) for 20 minutes; then it is sandblasted using 120-mesh corundum abrasive at a pressure of 0.3 MPa for 3 minutes; then it is vacuum annealed at 400℃ for one hour under argon protection to obtain the surface-cleaned front-end shaft blank.

[0044] S2. The surface-cleaned front-end shaft blank is subjected to a salt bath. The salt bath formulation provided in this application consists of 40% urea, 30% potassium nitrate, 20% sodium carbonate, and 10% LaF3 by weight. First, a low-temperature nitriding operation is performed, reacting at 480°C for 2 hours in a closed space under argon protection. Urea decomposes to generate active nitrogen, and LaF3 catalyzes the formation of nano-sized ε-Fe. 2-3 The primary N phase is then subjected to a high-temperature oxygenation process, reacting at 520°C for 1 hour in a confined space containing NH3 and CO2 at a volume ratio of 3:1. Potassium nitrate decomposes to provide oxygen, reacting with Fe to form Fe3O4. This results in the formation of Fe3O4 and ε-Fe on the surface of the front-end shaft blank. 2-3 N composite layer.

[0045] S3, containing Fe3O4 and ε-Fe 2-3 The front end shaft blank of the N composite layer is subjected to high-frequency quenching. First, it is heated with a surface heating rate of 100℃ / s and a target temperature of 860℃. Then, it is sprayed with a 0.1% polyvinyl alcohol aqueous solution at a pressure of 0.4MPa and a cooling rate of ≥200℃ / s.

[0046] A low-temperature tempering process was then employed: vacuum tempering at 180℃ for 2 hours, with a heating rate ≤50℃ / h. Following this, chemical mechanical polishing was performed using diamond polishing paste to remove the 0.5μm surface oxide film. Finally, micro-arc oxidation was performed at 450V for 30 minutes to generate an α-Al₂O₃ sealing layer. The electrolyte used in the micro-arc oxidation process included Na₂SiO₃ and KOH. This resulted in a pre-treated front-end shaft.

[0047] 2. Crankarm surface pretreatment:

[0048] S1. The crank arm blank is ultrasonically cleaned using a 60℃ alkaline aqueous solution (containing 5% NaOH + 3% Na2CO3, pH = 11) for 20 minutes; then it is sandblasted using 120-mesh corundum abrasive at a pressure of 0.3 MPa for 3 minutes; then it is vacuum annealed under argon protection at 400℃ for one hour, thus obtaining a surface-cleaned crank arm blank.

[0049] S2. The crank arm blank material after surface purification is subjected to a salt bath. The salt bath formula provided in this application is 40% urea, 30% potassium nitrate, 20% sodium carbonate, and 10% LaF3 by weight. First, a low-temperature nitriding operation is performed, reacting at 480°C for 2 hours in a closed space under argon protection. Urea decomposes to generate active nitrogen, and LaF3 catalyzes the formation of nanoscale Fe4N primary phase. Then, a high-temperature oxygen diffusion operation is performed, reacting at 520°C for 1 hour in a closed space containing NH3 and CO2, with a gas volume ratio of NH3 to CO2 of 3:1. LaF3 promotes the dispersion and precipitation of LaN, forming a coherent reinforcing structure with Fe4N. A composite layer with Fe4N and LaN is formed on the surface of the crank arm blank material.

[0050] S3. The crank arm blank with the composite layer of Fe4N and LaN is laser scanned. The fiber laser wavelength is 1064nm, the power is 500W, the scanning speed is 2m / s, the spacing is 200μm, and the depth is 5μm. The prefabricated microgroove array serves as a stress buffer to guide the uniform distribution of subsequent rolling pressure and avoid the nitriding layer from cracking due to stress concentration.

[0051] Then, gradient rolling was used with a rolling force of 2800 N; the roller type was a cemented carbide roller with an Al2O3 coating; the pressing depth was 0.3 mm; and the feed rate was 0.08 mm / r. Finally, a low-temperature tempering operation was performed at 200℃ for 2 hours, and a 0.5 μm brittle phase on the surface was removed by chemical mechanical polishing to obtain the surface-treated crank arm blank.

[0052] 3. Rear shaft surface pretreatment:

[0053] S1. The rear crank arm blank is ultrasonically cleaned using a 60℃ alkaline aqueous solution (containing 5% NaOH + 3% Na2CO3, pH = 11) for 20 minutes. Then, it undergoes sandblasting, using 120-mesh corundum abrasive at a pressure of 0.3 MPa for 3 minutes. Finally, it is vacuum annealed under argon protection at 400℃ for one hour to obtain the surface-cleaned crank arm blank.

[0054] S2. The rear shaft blank material after surface purification is subjected to a salt bath. The salt bath formula provided in this application is 40% urea, 30% potassium nitrate, 20% sodium carbonate, and 10% LaF3 by weight. First, a low-temperature nitriding operation is performed, reacting at 480°C for 2 hours in a closed space under argon protection. Urea decomposes to generate active nitrogen, and the Cr-rich area of ​​the matrix is ​​pre-oxidized to form Cr2O3 crystal nuclei. Then, a high-temperature oxygen diffusion operation is performed, reacting at 520°C for 1 hour in a closed space containing NH3 and CO2, with a gas volume ratio of NH3 to CO2 of 1:1. Potassium nitrate provides oxygen at high temperature and reacts with Cr to generate Cr2O3. At the same time, CO2 inhibits the precipitation of CrN, and a composite layer with γ'-Fe4N and Cr2O3 is formed on the surface of the crank arm blank material.

[0055] S3. The rear shaft blank material with the composite layer of γ'-Fe4N and Cr2O3 is rolled with rollers. The roller type is a roller with Al2O3 coating. The rolling force is 1000N. The pressing depth is 0.1mm. The feed rate is 0.05mm / r. The cooling method is liquid nitrogen (-196℃) spray.

[0056] Then, micro-arc oxidation sealing is performed with a voltage of 450V±20V, a frequency of 1000Hz, a duty cycle of 30%, and a time of 0.5-1.5h. The electrolyte formulation includes Na2SiO3, KOH, and CrO3.

[0057] Next, low-temperature tempering is carried out, holding at 200℃ for 1 hour, and then holding at 150℃ for 2 hours to eliminate rolling and interfacial stress, promote the precipitation of the γ'-Fe4N phase as a strengthening phase, and finally obtain the surface-treated rear shaft blank.

[0058] 4. Overall assembly of the crankshaft:

[0059] S1. The air compressor crankshaft in this application includes a crankshaft body, on which a front end shaft, a crank arm, and a rear end shaft are connected in sequence; and the front end shaft, the crank arm, and the rear end shaft are all surface treated.

[0060] The crank arm has internal spline holes at both ends that correspond to the crankshaft body. By heating the crank arm to 180°C, it is quickly pressed onto the crankshaft body and then cooled to form a tight fit.

[0061] S2. The front shaft is connected to the crank arm through a tapered journal, and molybdenum disulfide lubricant is applied to the tapered surface to reduce assembly stress. Then, the keyway of the front shaft is aligned with the timing mark on the crankshaft body and fixed.

[0062] S3. A support bearing is installed between the rear shaft and the crank arm. The inner ring of the bearing is pre-coated with high-temperature grease, and a through groove is opened in the crank arm to facilitate the sliding of the connecting rod bearing into the root of the journal. It is then locked axially to obtain the air compressor crankshaft.

[0063] S4. Test the rotational speed of the air compressor crankshaft on a balancing machine, calculate the residual imbalance, and if it exceeds the standard, reduce the weight by grinding the non-load-bearing surface of the crank arm to finally obtain the air compressor crankshaft.

[0064] Examples 2-4

[0065] The difference between Examples 2-4 and Example 1 is that the salt bath formulations are different in the oxygen-nitrogen co-osmosis process during the pretreatment of the front shaft surface, the crank arm surface, and the rear shaft surface. The salt bath formulations, by weight percentage, are summarized in Table 1 below.

[0066] Table 1. Salt Bath Formulation Table for Examples 1-4

[0067] Urea / % Potassium nitrate / % Sodium carbonate / % Lanthanum trifluoride / % Example 1 40 30 20 10 Example 2 30 30 30 10 Example 3 50 20 25 5 Example 4 45 25 15 15

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 1 is that no pretreatment operation was performed on the surface of the front shaft, the surface of the crank arm, and the surface of the rear shaft. Instead, the front shaft blank, the crank arm blank, and the rear shaft blank were simply surface-polished before being assembled into a finished air compressor crankshaft.

[0070] The difference between Comparative Example 2 and Example 1 is that, during the pretreatment of the front shaft surface, the front shaft surface was subjected to low-temperature nitriding and high-temperature oxygen diffusion, but the front shaft blank was not subjected to high-frequency quenching, low-temperature tempering and micro-arc oxidation afterwards.

[0071] The difference between Comparative Example 3 and Example 1 is that, during the pretreatment of the crank arm surface, the crank arm surface was subjected to low-temperature nitriding and high-temperature diffusion, but the crank arm blank was not subjected to laser scanning, gradient rolling, low-temperature tempering and polishing.

[0072] The difference between Comparative Example 4 and Example 1 is that, during the pretreatment of the rear shaft surface layer, the rear shaft surface layer is subjected to low-temperature nitriding and high-temperature diffusion, but the rear shaft blank is not rolled, then subjected to micro-arc oxidation sealing and low-temperature tempering.

[0073] Performance testing experiment

[0074] To further investigate the performance parameters of the air compressor crankshaft, this application further conducts the following verification embodiments.

[0075] 1. Front shaft wear resistance test

[0076] The front shafts from Examples 1-4 and Comparative Examples 1-4 were used as samples. According to GB / T19055 "Technical Conditions for Forged Steel Crankshafts of Passenger Cars", the front shaft samples were subjected to bench tests. The front shafts were fixed on the sample crankshaft body and installed to simulate the full working conditions of the engine. The change in the journal diameter of the front shaft was measured periodically (micrometer accuracy 0.001mm). The cumulative running time was ≥2000 hours, and the wear amount (unit mm) was recorded.

[0077] 2. Crankarm fatigue testing

[0078] The crank arms from Examples 1-4 and Comparative Examples 1-4 were used as samples. These crank arm samples were placed in an electromagnetic resonant fatigue testing machine for testing. The frequency range was 20–200 Hz; the load error was ≤±3%, and the dynamic fluctuation was ≤±0.5%. The machine was stopped when the system resonant frequency decreased by 1%; or when the number of cycles exceeded 5 × 10⁻⁶. 4 Afterwards, stop the machine and observe for any cracks.

[0079] 3. Rear end shaft anti-seize performance test

[0080] The rear end shafts from Examples 1-4 and Comparative Examples 1-4 were used as samples. Under the condition of crankshaft installation, high temperature (150°C) and high pressure conditions were simulated. After running for 100 hours, the shafts were disassembled and inspected to detect the wear of the sealing lip on the rear end (in mm). At the same time, it was observed whether there was any adhesion or metal transfer.

[0081] 4. Crankshaft overall service life testing

[0082] The compressor crankshafts prepared by the methods in Examples 1-4 and Comparative Examples 1-4 were assembled into test samples. According to the testing standard QC / T 637-2000, they were tested using a high-frequency resonant fatigue testing machine and cycled for 10 days. 7 If the specimen does not fail after this, it can be defined as having an infinite fatigue life under this load. Then observe whether cracks appear (cracks appearing at any position of the front shaft, crank arm, rear shaft, crankshaft body, and the connection of each part indicate that the fatigue life limit has been reached).

[0083] The above tests are summarized in Table 2 below.

[0084] Table 2, Performance Test Tables of Examples 1-4 and Comparative Examples 1-4

[0085]

[0086]

[0087] Conclusion Analysis

[0088] Based on the analysis of Example 1 and Comparative Example 1, the difference between Comparative Example 1 and Example 1 is that no pretreatment was performed on the surface layers of the front shaft, crank arm, and rear shaft. Only the surface of the front shaft blank, crank arm blank, and rear shaft blank was polished before assembly into a finished air compressor crankshaft. The results in the aforementioned front shaft wear resistance test, crank arm fatigue test, and rear shaft anti-galling performance test were all unsatisfactory. Specifically, in the front shaft wear resistance test, a wear amount ≤0.025mm was considered acceptable, while in Comparative Example 1, the wear amount reached 0.028mm. Furthermore, in the crank arm fatigue test, using an electromagnetic resonant fatigue testing machine, the crank arm in Comparative Example 1 reached a fatigue resistance of 4×10⁻⁶ cycles. 4 At this point, the system's resonant frequency decreased, indicating that the fatigue limit had been reached. Although no obvious cracks were observed, it was determined that internal stress in the metal caused fracture. In addition, during the anti-galling performance test of the rear shaft, the rear shaft was mounted on a machine to simulate high temperatures.

[0089] Under high-pressure conditions, after 100 hours of operation, the shaft was disassembled and inspected to check the wear of the sealing lip on the rear end. The wear of a qualified rear end shaft was ≤0.02mm. In Comparative Example 1, the wear reached 0.025mm, and adhesion and metal transfer were observed. This would lead to a decrease in the engagement force of the rear end shaft during operation, which, through the bolted rigid connection to the flywheel, transmits power to the transmission system. Additionally, Comparative Example 1 also tested the overall service life of the crankshaft using a high-frequency resonant fatigue testing machine. It was found that after 9.5 × 10⁻⁶ cycles… 5 At this point, the crankshaft had reached the limit of its service life, and cracks appeared in the crankshaft components.

[0090] An analysis was conducted between Example 1 and Comparative Example 2. The difference between Comparative Example 2 and Example 1 is that, during the pretreatment of the front shaft surface, low-temperature nitriding and high-temperature oxygen diffusion were performed, but the front shaft blank was not subsequently subjected to high-frequency quenching, low-temperature tempering, and micro-arc oxidation. Furthermore, Comparative Example 2 did not separately test the physical properties of the crank arm and rear shaft; their properties remained consistent with those of the crank arm and rear shaft in Example 1 during individual testing.

[0091] During the wear resistance test of the front shaft, the front shaft blank was not subjected to high-frequency quenching, low-temperature tempering, and micro-arc oxidation. During the bench test, the diameter of the front shaft journal changed, and the wear amount was 0.025 mm. Although the wear amount was within the standard range, its performance was slightly lower than in Example 1. This is because low-temperature tempering can fix ε-Fe through quenching and rapid cooling. 2-3N, while micro-arc oxidation generates an α-Al2O3 sealing layer, increasing the Fe3O4 content. In this application, the Fe3O4 on the front-end shaft provides lubrication, reducing the coefficient of friction, and ε-Fe 2-3 N ensures high hardness, thereby reducing journal wear and improving crankshaft wear resistance.

[0092] Regarding Comparative Example 2, the crankshaft's overall service life was tested using a high-frequency resonant fatigue testing machine. It was found that after 7 × 10 cycles... 6 At this point, the crankshaft had reached the limit of its service life, and cracks appeared on the front end of the crankshaft.

[0093] In addition, an analysis was conducted between Example 1 and Comparative Example 3. The difference between Comparative Example 3 and Example 1 lies in that, during the pretreatment of the crank arm surface, the surface underwent low-temperature nitriding and high-temperature diffusion, but the crank arm blank was not subsequently subjected to laser scanning, gradient rolling, low-temperature tempering, and polishing. Furthermore, Comparative Example 3 did not separately test the physical properties of the front and rear shafts; however, their properties remained consistent with those of the front and rear shafts in Example 1 during individual testing.

[0094] In Comparative Example 3, when the crank arm was tested using an electromagnetic resonant fatigue testing machine, the number of cycles reached 4.5 × 10⁻⁶. 4 When the system resonance frequency decreased by 1%, the crank arm was determined to have reached its fatigue limit. No obvious cracks were found after removal, indicating that internal stress caused fracture. This was because Comparative Example 3 did not perform laser scanning on the crank arm blank, nor did it employ gradient rolling, low-temperature tempering, and polishing. Laser scanning pre-fabricated microgroove arrays act as stress buffers, guiding the subsequent rolling pressure to distribute evenly and preventing stress concentration cracking of the nitride layer. This application uses gradient rolling to embed Al2O3 particles into the surface to form an in-situ ceramic layer, enhancing wear resistance. Simultaneously, high pressure induces dislocation proliferation, forming a nanotwin structure that promotes LaN dispersed phase precipitation, inhibiting oxide formation. Furthermore, the LaN dispersed phase hinders dislocation slip, and the nanotwin structure inhibits crack propagation, thereby improving fatigue strength. Additionally, Comparative Example 3 tested the crankshaft's overall service life using a high-frequency resonant fatigue testing machine, finding that after 7.5 × 10⁻⁶ cycles… 6 At this point, the crankshaft had reached the limit of its service life, and cracks appeared on the crank arm in the crankshaft assembly.

[0095] An analysis was conducted between Example 1 and Comparative Example 4. The difference between Comparative Example 4 and Example 1 lies in the fact that, during the pretreatment of the rear shaft surface, low-temperature nitriding and high-temperature diffusion were performed on the rear shaft surface. However, the rear shaft blank was not subsequently subjected to roller rolling, followed by micro-arc oxidation sealing and low-temperature tempering. Furthermore, Comparative Example 4 did not separately test the physical properties of the front shaft and crank arm; their properties remained consistent with those of the front and rear shafts in Example 1 during individual testing.

[0096] In Comparative Example 4, the anti-seize performance of the rear end shaft was tested separately. Specifically, the rear end shaft was used as a sample, and under simulated high temperature and high pressure conditions in the crankshaft mounting state, it was disassembled and inspected after 100 hours of operation. The wear of the sealing lip around the rear end was tested, as well as adhesion or metal transfer phenomena. In Comparative Example 4, the wear reached 0.020 mm, which is within the standard range of 0.02 mm. However, adhesion and transfer phenomena occurred at the metal seize area. It can be concluded that although the wear of the crank arm after nitrogen-oxygen permeation alone met the requirements, the seize degree was insufficient. During high-intensity operation, adhesion or metal transfer phenomena will occur at the connection point. Then, compared with Example 1, the reason was analyzed to be that Al2O3 was embedded in the metal surface during shallow rolling to reduce the coefficient of friction, and then liquid nitrogen cooling suppressed springback and stabilized residual compressive stress. Then, during the micro-arc oxidation sealing process, the high-voltage discharge causes the formation of an α-Al2O3 ceramic layer in the surface micropores. The incorporation of CrO3 improves the density, thereby reducing the adhesive wear phenomenon on the rear shaft surface under high-intensity working conditions, which in turn helps to improve the engagement ability of the rear shaft.

[0097] Analysis was conducted between Examples 1-4. Under the oxygen-nitrogen co-osmosis method, during the pretreatment of the front shaft surface, crank arm surface, and rear shaft surface, the physical properties of the front shaft, crank arm, and rear shaft were observed by adjusting different salt bath formulations. It was found that the salt bath formulation, by weight, consisting of 40% urea, 30% potassium nitrate, 20% sodium carbonate, and 10% LaF3, resulted in stronger overall physical properties of the front shaft, crank arm, and rear shaft. Therefore, Example 1 is the optimal example.

[0098] This application measures the composition of the front shaft surface layer, crank arm surface layer, and rear shaft surface layer in Example 1. Specifically, it mainly includes Fe3O4 and ε-Fe. 2-3 The determination of N, Al2O3, Fe4N, LaN and Cr2O3 was performed, and quantitative analysis was achieved by XRD.

[0099] According to the characterization requirements, it should be noted that Fe3O4 was linearly related to its content by using the XRD standard curve method, relying on the intensity of characteristic peaks (2θ = 35.5°, 62.6°).

[0100] Among them, ε-Fe 2-3 N and γ'-Fe4N were analyzed by XRD phase composition; specifically, ε-Fe 2-3 The characteristic peaks of N are 44.3° and 51.8°; the characteristic peaks of γ'-Fe4N are 2θ = 41.2° and 48.0°.

[0101] Furthermore, regarding γ'-Fe4N and Fe4N, the main difference lies in the second composite layer on the crank arm and the third composite layer on the rear shaft. According to the XRD lattice parameter method formula a(y)=3.573×10-3y+0.3573 (y is the N content), it can be determined that the third composite layer on the rear shaft is almost always a γ-Fe lattice.

[0102] LaN was quantified using inert atmosphere XRD, with characteristic peaks (2θ = 30.5°, 52.1°).

[0103] Regarding Cr2O3, the internal standard method was used by adding fluorite (CaF2) as an internal standard and quantifying the intensity ratio of Cr2O3 characteristic peaks. This method is mainly used to quantify the components on the third composite layer on the rear end shaft.

[0104] And regarding Al2O3, we calculated α-Al2O3 and the Al2O3 content by fitting the entire diffraction pattern (43.3° characteristic peak).

[0105] The composition and content of each component in the crankshaft surface of the air compressor in Example 1 are summarized in the following table, where the units are expressed as weight percentages (%).

[0106] Table 3. Composition content of each part of the crankshaft surface layer of the air compressor in Example 1

[0107] <![CDATA[Fe3O4]]> <![CDATA[ε-Fe 2-3 N]]> <![CDATA[Fe4N]]> <![CDATA[γ'-Fe4N]]> <![CDATA[α-Al2O3]]> <![CDATA[Al2O3]]> <![CDATA[Cr2O3]]> LaN impurities First composite layer 35.5％ 55.2％ 1.2％ 0.8％ 3.2％ 0.8％ 1.3％ 1.0％ 1.0％ Second composite layer 12.1％ 1.3％ 71.2％ 1.4％ 1.6％ 3.5％ 1.2％ 6.5％ 1.2％ Third composite layer 14.2％ 1.5％ 1.8％ 48.2％ 3.4％ 1.8％ 22.3％ 1.6％ 5.3％

[0108] Furthermore, this application involves multiple experiments conducted during the manufacturing process to determine the process parameters for the pretreatment of the front shaft surface, the crank arm surface, and the rear shaft surface. These experiments were repeated based on existing technology and experience. Specifically, the parameters included high-frequency quenching, low-temperature tempering, mechanical polishing, and micro-arc oxidation in the front shaft surface pretreatment; laser scanning and gradient rolling parameters in the crank arm surface pretreatment; and roller rolling and micro-arc oxidation parameters in the rear shaft surface pretreatment.

[0109] In summary, the experimental parameters of Example 1 have the best overall physical properties, that is, Example 1 is the optimal example.

[0110] It should be noted that the order of the embodiments described above is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. Furthermore, specific embodiments have been described above. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps described in the claims can be performed in a different order than those shown in the embodiments and still achieve the desired results. In some implementations, multitasking and parallel processing are also possible or may be advantageous.

[0111] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

[0112] This specification is merely an illustrative description of this application and is intended to cover any and all modifications, variations, combinations, or equivalents within the scope of this application. Clearly, those skilled in the art can make various alterations and modifications to this application without departing from its scope. Therefore, if such modifications and modifications fall within the scope of this application and its equivalents, this application intends to include such modifications and modifications.

Claims

1. A method for machining a high wear-resistant air compressor crankshaft, characterized in that, The process includes the following steps: pre-treatment of the front shaft surface, pre-treatment of the crank arm surface, pre-treatment of the rear shaft surface, and overall assembly of the crankshaft. The pretreatment of the front shaft surface, the pretreatment of the crank arm surface, and the pretreatment of the rear shaft surface all include the oxygen-nitrogen co-percolation method. The oxygen-nitrogen co-osmosis method includes a salt bath, the salt bath formulation comprising, by weight percentage, 30%-50% urea, 20%-40% potassium nitrate, 10%-30% sodium carbonate, and 5%-15% lanthanum trifluoride.

2. The high wear-resistant air compressor crankshaft as described in claim 1, characterized in that, The preprocessing of the front-end shaft surface includes the following steps: S1. The front-end shaft blank is ultrasonically cleaned, then sandblasted and vacuum annealed to obtain a surface-cleaned front-end shaft blank. S2. The surface-cleaned front-end shaft blank is subjected to a salt bath, followed by low-temperature nitriding and high-temperature oxygenation to form Fe3O4 and ε-Fe on the surface of the front-end shaft blank. 2-3 The N composite layer; in the low-temperature nitriding operation, the enclosed space is protected by argon gas; in the high-temperature oxygen diffusion operation, the enclosed space is composed of NH3 and CO2, and the gas volume ratio of NH3 to CO2 is 3:1; S3, containing Fe3O4 and ε-Fe 2-3 The front-end shaft blank of the N-composite layer is subjected to high-frequency quenching, low-temperature tempering, mechanical polishing and micro-arc oxidation to obtain a front-end shaft with surface pretreatment.

3. The high wear-resistant air compressor crankshaft as described in claim 2, characterized in that, In the process of pre-processing the surface layer of the front shaft: The high-frequency quenching parameters are as follows: heating surface heating rate 80-120℃ / s, target temperature 860℃±30℃; 0.1% polyvinyl alcohol aqueous solution spray cooling, pressure 0.3-0.5MPa, cooling rate ≥200℃ / s; The low-temperature tempering parameters are: vacuum tempering at 180℃±20℃ for 1-3 hours, with a heating rate ≤50℃ / h. The mechanical polishing step involves grinding with diamond polishing paste. The micro-arc oxidation parameters are as follows: electrolyte formulation (including Na2SiO3 and KOH); voltage 450V; time 0.5-1.5h.

4. The high wear-resistant air compressor crankshaft as described in claim 1, characterized in that, The pretreatment of the crank arm surface includes the following steps: S1. The crank arm blank is ultrasonically cleaned, then sandblasted and vacuum annealed to obtain a surface-cleaned crank arm blank: S2. The surface-cleaned crank arm blank is subjected to a salt bath and subjected to low-temperature nitriding and high-temperature diffusion operations to form a composite layer of Fe4N and LaN on the surface of the crank arm blank. In the low-temperature nitriding operation, the enclosed space is protected by argon gas. In the high-temperature diffusion operation, the enclosed space is NH3 and CO2, and the gas volume ratio of NH3 to CO2 is 3:

1. S3. The crank arm blank with the composite layer of Fe4N and LaN is laser scanned, and then subjected to gradient rolling, low temperature tempering and polishing to obtain a surface-treated crank arm blank.

5. The high wear-resistant air compressor crankshaft as described in claim 4, characterized in that, In the process of pre-treating the surface of the crank arm; The laser scanning parameters are as follows: fiber laser wavelength 1064nm, power 450-550W, scanning speed 1.5-2.5m / s, spacing 150-250μm, and depth 3-8μm. The gradient rolling parameters are as follows: rolling force 2600-3000N; roller type is a cemented carbide roller with Al2O3 coating on the surface; pressing depth 0.3mm; feed rate 0.08mm / r.

6. The high wear-resistant air compressor crankshaft as described in claim 1, characterized in that, The preprocessing of the rear shaft surface includes the following steps: S1. The rear shaft blank is ultrasonically cleaned, then sandblasted and vacuum annealed to obtain a surface-cleaned rear shaft blank. S2. The surface-cleaned rear shaft blank is subjected to a salt bath and subjected to low-temperature nitriding and high-temperature diffusion operations to form a composite layer with γ'-Fe4N and Cr2O3 on the surface of the rear shaft blank; in the low-temperature nitriding operation, the enclosed space is protected by argon gas; in the high-temperature diffusion operation, the enclosed space is NH3 and CO2, and the gas volume ratio of NH3 to CO2 is 1:

1. S3. The rear shaft blank material with the composite layer of γ'-Fe4N and Cr2O3 is rolled, then micro-arc oxidation sealing and low-temperature tempering are performed to obtain the surface-treated rear shaft blank material.

7. A high wear-resistant air compressor crankshaft as described in claim 6, characterized in that, In the process of pre-treating the surface layer of the rear shaft: The roller rolling parameters are as follows: roller type is a roller with an Al2O3 coating; rolling force is 1000±200N; rolling depth is 0.1-0.2mm; feed rate is 0.05mm / r; cooling method is liquid nitrogen injection. The micro-arc oxidation parameters are as follows: voltage 450V±20V; frequency 1000Hz; duty cycle 30%; time 0.5-1.5h; electrolyte formulation (including Na2SiO3, KOH, CrO3).

8. The high wear-resistant air compressor crankshaft as described in claim 1, characterized in that, The overall assembly of the crankshaft includes the following steps: S1. The internal spline holes at both ends of the crank arm correspond to the crankshaft body. The crank arm is heated to 180-200°C and quickly pressed into the crankshaft body. After cooling, a tight fit is formed. S2. The front end shaft is connected to the crank arm via a tapered journal, and the keyway of the front end shaft is aligned and fixed with the timing mark on the crankshaft body. S3. A support bearing is installed between the rear end shaft and the crank arm. The inner ring of the bearing is pre-coated with high-temperature grease, and a through groove is opened in the crank arm to facilitate the connecting rod bearing to slide into the root of the journal. The bearing is then locked axially to obtain the air compressor crankshaft. S4. Test the rotational speed of the air compressor crankshaft on a balancing machine, calculate the residual imbalance, and if it exceeds the standard, reduce the weight by grinding the non-load-bearing surface of the crank arm.

9. A high wear-resistant air compressor crankshaft, characterized in that, It is prepared by the machining method of the high wear-resistant air compressor crankshaft as described in any one of claims 1-8; The high wear-resistant air compressor crankshaft includes a crankshaft body, on which a front end shaft, a crank arm, and a rear end shaft are connected in sequence; the front end shaft, the crank arm, and the rear end shaft are all surface treated; The front end shaft undergoes a pretreatment process to form a first composite layer on its surface. The main components of the first composite layer include Fe3O4 and ε-Fe. 2-3 N and α-Al2O3; The crank arm is pretreated to form a second composite layer on its surface. The main components of the second composite layer include Fe4N, LaN, Fe3O4 and Al2O3. The rear end shaft is pretreated to form a third composite layer on its surface. The main components of the third composite layer include γ'-Fe4N, Cr2O3, Fe3O4 and α-Al2O3.

10. A high wear-resistant air compressor crankshaft as described in claim 9, characterized in that, In the first composite layer, by weight percentage: Fe3O4 is 30%-40%; ε-Fe 2-3 N is 50%-70%; α-Al₂O₃ is 2%-8%; Fe₄N is 0%-2%; γ'-Fe₄N is 0%-2%; Al₂O₃ is 0%-2%; Cr₂O₃ is 0%-2%; LaN is 0%-2% and the remaining unavoidable impurities; In the second composite layer, by weight percentage: Fe4N is 65%-85%; LaN is 2%-10%; Fe3O4 is 10%-15%; Al2O3 is 2-8%; ε-Fe 2-3 N is 0%-2%; γ'-Fe4N is 0%-2%; α-Al2O3 is 0%-2%; Cr2O3 is 0%-2% and the remaining unavoidable impurities; In the third composite layer, by weight percentage: γ'-Fe4N is 40%-60%; Cr2O3 is 10%-30%; α-Al2O3 is 2-8%; Fe3O4 is 10%-15%; Fe4N is 0%-2%; ε-Fe 2-3 N is 0%-2%; Al2O3 is 0%-2%; LaN is 0%-2% and the remaining unavoidable impurities.

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