Industrial chain wheel surface plasma nitriding treatment process
By employing a plasma nitriding process for industrial sprocket surfaces, including shot peening, plasma cleaning, gradient nitriding, and post-treatment, the wear problem of sprockets in harsh environments is solved, and the hardness and wear resistance are improved, ensuring the stability and long service life of sprockets under complex working conditions.
Patent Information
- Application Number
- CN202511191097.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-08-25
- Publication Date
- 2026-01-02
AI Technical Summary
Existing sprockets are prone to wear, tooth surface spalling, and fatigue cracks under high load, high frequency friction, and corrosive environments. Traditional processing methods result in poor wear resistance, frequent failures, and safety hazards.
The industrial sprocket surface plasma nitriding process is adopted, which includes shot peening, plasma cleaning, gradient nitriding and post-treatment. Pretreatment removes oil and impurities, laser roughening increases surface roughness, plasma cleaning activates the surface, gradient nitriding controls the gas ratio and temperature, and post-treatment eliminates the brittle layer and forms a CrN coating.
It significantly improves the surface hardness and wear resistance of sprockets, extends their service life, reduces the brittle layer and internal stress, and ensures stable operation under complex working conditions.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of industrial chain, in particular to a surface plasma nitriding treatment process of industrial chain wheel. BACKGROUND
[0002] Industrial chain, as a key component in mechanical transmission system, is widely used in many fields such as mining, metallurgy, logistics, manufacturing, etc. It realizes power transmission and material conveying through the meshing of chain links and chain wheels, and has the characteristics of high transmission efficiency, strong carrying capacity and adaptability to harsh environment. Chain wheel, as the core component of chain transmission, its performance directly affects the stability and service life of the whole transmission system. Its main function is to accurately mesh the tooth profile structure with the chain link to transmit power from the driving shaft to the driven shaft, or to realize the conversion of speed and torque.
[0003] However, the existing chain wheel is prone to surface wear, tooth surface peeling and fatigue cracks during long-term use due to high load, high frequency friction, impact and factors such as dust and corrosive medium in its working environment.
[0004] The traditional chain wheel surface treatment process (such as conventional nitriding and quenching) has defects such as uneven penetration depth, insufficient surface hardness and high brittleness, which leads to poor wear resistance of the chain wheel. In long-term heavy load transmission, the chain wheel is prone to failure due to excessive wear of the tooth surface, which not only requires frequent downtime for replacement, increasing maintenance costs and production downtime, but also may cause equipment failure due to sudden failure of the chain wheel, posing a safety hazard.
[0005] Therefore, there is a need for a surface treatment process that can significantly improve the wear resistance of the chain wheel surface and prolong its service life to obtain a chain wheel with better performance. SUMMARY
[0006] In view of the problems in the prior art, the present application provides a surface plasma nitriding treatment process for industrial chain wheel.
[0007] The technical scheme adopted by the present application to solve its technical problems is: a surface plasma nitriding treatment process for industrial chain wheel, comprising the following steps: (1) Pretreatment: shot peening strengthening treatment is performed on the chain wheel, the shot peening pressure is 135-180 MPa, the nozzle distance from the chain wheel surface is 9-12 mm, the mixed shot peening strengthening uses steel shot and ceramic shot with a mixing mass ratio of 3:1, and the shot peening coverage is 200%-250%; (2) Plasma cleaning: in a mixed gas with an argon-hydrogen volume ratio of 2:1-1.2, a stepwise increasing pressure bias is applied, starting from -300V, increasing by -100V every 5 minutes, until reaching -500V to -800V for surface activation, the total pressure of the mixed gas is maintained at 0.5-1.2 Pa, and the cleaning time is 25-30 minutes; (3) Gradient nitriding: nitrogen-containing gas and carbon-containing gas are introduced, and the pressure is controlled in stages; (4) Post-processing: pulse denitriding is performed using a pulse power source with a frequency of 14-20 Hz and a duty cycle of 30%-50% to eliminate the surface brittle layer, and the cooling rate is controlled at 20-30 ℃ / min.
[0008] As a further technical solution: the particle size of the steel shot is 0.3-0.6 mm; The particle size of the ceramic shot is 1.1-1.5 mm.
[0009] As a further technical solution: before the pretreatment step, the chain wheel is ultrasonically cleaned, the cleaning liquid is a mixture of ethanol and water with a volume ratio of 3:2, the cleaning time is 20-30 minutes, and the ultrasonic frequency is 40 kHz.
[0010] As a further technical solution: after the shot peening treatment, the surface of the chain wheel is subjected to laser texturing treatment, the laser power is 50-80 W, the scanning speed is 100-150 mm / s, and the laser spot diameter is 0.1-0.3 mm.
[0011] As a further technical solution: in the plasma cleaning step, 0.3%-0.8% helium is added to the mixed gas based on the total volume of the mixed gas to improve the stability of the plasma.
[0012] As a further technical solution: the gradient nitriding process includes: First stage: temperature 480-500℃, ammonia and nitrogen in the nitrogen-containing gas at a volume ratio of 1:1, pressure 0.8-1.0 Pa, treatment time 30-45 minutes, the flow rate of the carbon-containing gas is 5%-8% of the total flow rate of the nitrogen-containing gas; Second stage: temperature 500-520℃, ammonia and nitrogen in the nitrogen-containing gas at a volume ratio of 1:2, pressure 1.2-1.5 Pa, treatment time 60-70 minutes, the flow rate of the carbon-containing gas is 5%-8% of the total flow rate of the nitrogen-containing gas; The carbon-containing gas is methane.
[0013] As a further technical solution: between the two stages of gradient nitriding, a transition stage is arranged, the temperature of the transition stage is 500 DEG C, the volume ratio of ammonia to nitrogen is 1:1.5-1.8, the pressure is 1.0-1.2 Pa, and the treatment time is 15-20 minutes.
[0014] As a further technical solution: in the gradient nitriding step, a small amount of oxygen is introduced while the nitrogen-containing gas and the carbon-containing gas are introduced, the oxygen flow is 0.3%-0.5% of the total flow of the nitrogen-containing gas, and the oxygen is introduced in a pulse mode, and the pulse frequency is consistent with the plasma power frequency.
[0015] As a further technical solution: in the cooling process of the post-treatment, when the temperature drops to 200-250 DEG C, the heat preservation treatment is carried out, the heat preservation time is 30-40 minutes, and then the cooling to room temperature is continued.
[0016] As a further technical solution: in the post-treatment, after the pulse denitriding is finished, the surface of the sprocket is subjected to ion sputtering plating, the plating material is CrN, the plating thickness is 1-3 microns, and the sputtering current is 2-4 A.
[0017] The present application has the following beneficial effects: The industrial sprocket surface plasma nitriding treatment process provided by the application realizes the improvement of the sprocket surface performance through the synergistic effect of each step, and specifically as follows: The synergistic effect of pretreatment and plasma cleaning: in the pretreatment stage, ultrasonic cleaning can completely remove oil stains and impurities on the surface of the sprocket, providing a clean substrate for subsequent treatment; the shot peening adopts mixed shot of steel shot and ceramic shot, utilizes the impact effect of shot of different particle sizes to make the sprocket surface produce plastic deformation and form a uniform rough surface, and introduces residual compressive stress to improve the surface hardness; laser texturing further increases the surface micro-roughness and enhances the bonding force between the subsequent nitriding layer and the substrate. The plasma cleaning in the argon-hydrogen mixed gas with stepwise pressure increase and the ionization enhancement effect of a small amount of helium can effectively remove the surface oxide film and activate the surface atom activity, creating favorable conditions for the adsorption and diffusion of nitrogen atoms. The synergy of pretreatment and plasma cleaning provides a high-activity and high-bonding surface state for the subsequent nitriding process, ensuring the stability of the quality of the nitriding layer.
[0018] Core strengthening effect of gradient nitriding: Gradient nitriding realizes the gradient distribution of nitrogen concentration by controlling the temperature, pressure and gas ratio in stages. In the first stage, at a lower temperature, a specific ratio of ammonia and nitrogen is beneficial to the preliminary penetration of nitrogen atoms and the formation of a shallow high-hardness layer; in the transition stage, the gas ratio and pressure are adjusted smoothly to avoid stress concentration in the nitriding layer caused by parameter mutation; in the second stage, at a higher temperature, the ammonia ratio is reduced to promote the diffusion of nitrogen atoms to the deep layer, and methane is introduced to provide a carbon source to form a carbonitride strengthening phase, and the introduction of a small amount of pulsed oxygen can promote the generation of oxides or composite compounds, further improving the surface hardness and wear resistance. The mechanism of gradient nitriding is to realize the smooth transition of the hardness of the nitriding layer from the surface to the matrix by gradient changes of temperature and gas atmosphere, which not only ensures high surface hardness, but also avoids brittle cracking caused by sudden hardness changes, significantly optimizing the comprehensive mechanical properties of the nitriding layer.
[0019] Performance optimization effect of post-treatment: Pulse denitriding can eliminate the surface brittle layer and reduce the risk of crack generation through the action of a pulse power source with a specific frequency and duty cycle; the heat preservation treatment during the cooling process can effectively release internal stress and prevent sprocket deformation; ion sputtering CrN plating forms a dense protective film on the surface of the nitriding layer, which further reduces the friction coefficient and improves the surface wear resistance and corrosion resistance by using the high hardness and corrosion resistance of CrN. The post-treatment steps can optimize the final performance of the sprocket by eliminating defects, stabilizing the size and enhancing surface protection, ensuring its long-term stable operation under complex working conditions.
[0020] In summary, the present application forms a complete strengthening system through the synergistic cooperation of pretreatment, plasma cleaning, gradient nitriding and post-treatment, from surface state optimization, nitriding layer structure regulation to performance stability improvement, significantly improving the surface hardness, wear resistance and service life of the sprocket, while the process is controllable and suitable for industrial production, having important practical application value. DETAILED DESCRIPTION
[0021] The technical solutions in the embodiments of the present application will be described below in a clear and complete manner. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.
[0022] The present application provides an industrial sprocket surface plasma nitriding treatment process, comprising the following steps: (1) Pretreatment: shot peening strengthening treatment is performed on the sprocket, the shot peening pressure is 135-180 MPa, the nozzle distance from the sprocket surface is 9-12 mm, the mixed shot peening uses a mixture of steel shot and ceramic shot with a mixing mass ratio of 3:1, and the shot peening coverage is 200%-250%; (2) Plasma cleaning: in a mixed gas with an argon-hydrogen volume ratio of 2:1-1.2, a stepwise increasing voltage bias is applied, starting from-300V, increasing by-100V every 5 minutes, until-500V to-800V is reached for surface activation, the total pressure of the mixed gas is maintained at 0.5-1.2 Pa, and the cleaning time is 25-30 minutes; (3) Gradient nitriding: nitrogen-containing gas and carbon-containing gas are introduced, and the pressure is controlled in stages; (4) Post-processing: pulse denitriding is performed using a pulse power source with a frequency of 14-20 Hz and a duty cycle of 30%-50% to eliminate the surface brittle layer, and the cooling rate is controlled at 20-30℃ / min.
[0023] In the present application, before the pretreatment step, the sprocket is preferably ultrasonically cleaned, the cleaning liquid is a mixture of ethanol and water, the volume ratio of ethanol to water is 3:2, the cleaning time is 20-30 minutes, and the ultrasonic frequency is 40 kHz; ultrasonic cleaning can remove oil stains and impurities on the surface of the sprocket, avoiding affecting the subsequent processing effect.
[0024] In the present application, the particle size of the steel shot is preferably 0.3-0.6 mm, more preferably 0.4-0.5 mm; the particle size of the ceramic shot is preferably 1.1-1.5 mm, more preferably 1.2-1.4 mm; the mixed shot in this particle size range can ensure the shot peening effect while avoiding excessive damage to the surface of the sprocket.
[0025] In the present application, after the shot peening treatment, the surface of the sprocket is preferably subjected to laser texturing treatment, the laser power is 50-80 W, more preferably 60-70 W; the scanning speed is 100-150 mm / s, more preferably 120-140 mm / s; the laser spot diameter is 0.1-0.3 mm, more preferably 0.2-0.25 mm; laser texturing can increase the surface roughness of the sprocket and improve the adhesion of the subsequent nitriding layer.
[0026] In the present application, in the plasma cleaning step, 0.3%-0.8% of helium is preferably added based on the total volume of the mixed gas, more preferably 0.5%-0.6%; the addition of helium can improve the ionization rate of the gas and enhance the cleaning effect.
[0027] In the present application, the gradient nitriding process preferably includes: First stage: temperature 480-500℃, ammonia to nitrogen volume ratio of 1:1 in nitrogen-containing gas, pressure 0.8-1.0 Pa, treatment time 30-45 minutes, carbon-containing gas flow rate is 5%-8% of the total nitrogen-containing gas flow rate; The second stage: the temperature is 500-520℃, the ammonia and nitrogen volume ratio of the nitrogen-containing gas is 1:2, the pressure is 1.2-1.5 Pa, the treatment time is 60-70 minutes, and the flow rate of the carbon-containing gas is 5%-8% of the total flow rate of the nitrogen-containing gas; the carbon-containing gas is methane.
[0028] Further, a transition stage is preferably arranged between the two stages of gradient nitriding, the temperature of the transition stage is 500℃, the ammonia and nitrogen volume ratio is 1:1.5-1.8, the pressure is 1.0-1.2 Pa, and the treatment time is 15-20 minutes; the transition stage can reduce the influence of the temperature and pressure mutation on the uniformity of the nitriding layer.
[0029] In the present application, a small amount of oxygen is introduced while the nitrogen-containing gas and the carbon-containing gas are introduced in the gradient nitriding step, the flow rate of the oxygen is 0.3%-0.5% of the total flow rate of the nitrogen-containing gas, and the oxygen is introduced in a pulse mode, and the pulse frequency is consistent with the frequency of the plasma power source; the small amount of oxygen can promote the formation of compounds in the nitriding layer and improve the surface hardness.
[0030] In the present application, the cooling process of the post-treatment is preferably followed by a heat preservation treatment when the temperature drops to 200-250℃, the heat preservation time is 30-40 minutes, and then the cooling continues to room temperature; the heat preservation treatment can reduce the internal stress and avoid the deformation of the sprocket.
[0031] In the present application, the sprocket surface is preferably subjected to ion sputtering plating after the pulse denitriding in the post-treatment, the plating material is CrN, the plating thickness is 1-3 μm, and more preferably 2-2.5 μm; the sputtering current is 2-4 A, and more preferably 3-3.5 A; the CrN plating can further improve the wear resistance and corrosion resistance of the sprocket.
[0032] The industrial sprocket surface plasma nitriding treatment process provided by the present application can significantly improve the hardness, wear resistance and corrosion resistance of the sprocket surface through the synergistic effect of the pretreatment, plasma cleaning, gradient nitriding and post-treatment, while reducing the surface brittle layer and internal stress and improving the service life of the sprocket; in addition, the process steps are controllable and suitable for industrial production.
[0033] In order to further illustrate the present application, the following examples and comparative examples are described in detail below. The sprocket material used in the following examples and comparative examples of the present application is 40Cr, and the size is 100 mm in diameter and 20 mm in thickness; the argon, hydrogen, ammonia, nitrogen, methane, helium and oxygen are all industrial-grade pure. Example 1
[0034] (1) Before the pretreatment, the sprocket is subjected to ultrasonic cleaning: the cleaning liquid is a mixture of ethanol and water (volume ratio 3:2), the ultrasonic frequency is 40 kHz, and the cleaning time is 25 minutes; (2) Shot peening: shot peening pressure 150 MPa, nozzle distance from the sprocket surface 10 mm; mixed shot: steel shot with a particle size of 0.4 mm and ceramic shot with a particle size of 1.3 mm, mass ratio 3:1; shot peening coverage 220%; (3) Plasma cleaning: in a mixed gas of argon and hydrogen with a volume ratio of 2:1.1, 0.5% of helium is added based on the total volume of the mixed gas; a stepwise increasing voltage bias is applied, starting from -300 V, increasing by -100 V every 5 minutes, until reaching -600 V for surface activation; the total pressure of the mixed gas is maintained at 0.8 Pa, and the cleaning time is 28 minutes; (4) Gradient nitriding: First stage: temperature 490℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:1, pressure 0.9 Pa, treatment time 35 minutes; carbon-containing gas is methane, flow rate is 6% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.4% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulsed manner with a frequency consistent with that of the plasma power supply; Transition stage: temperature 500℃, ammonia and nitrogen with a volume ratio of 1:1.6, pressure 1.1 Pa, treatment time 18 minutes; Second stage: temperature 510℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:2, pressure 1.3 Pa, treatment time 65 minutes; carbon-containing gas is methane, flow rate is 6% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.4% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulsed manner with a frequency consistent with that of the plasma power supply; (5) Post-treatment: Pulse denitriding: a pulse power supply with a frequency of 17 Hz and a duty cycle of 40% is used to eliminate the surface brittle layer; Cooling: the cooling rate is controlled at 25℃ / min, when the temperature drops to 220℃, hold for 35 minutes, then continue to cool to room temperature; Ion sputtering plating: the plating material is CrN, the plating thickness is 2μm, and the sputtering current is 3A. Example 2
[0035] (1) Before pretreatment, the sprocket is ultrasonically cleaned: the cleaning solution is a mixture of ethanol and water (volume ratio 3:2), the ultrasonic frequency is 40 kHz, and the cleaning time is 20 minutes; (2) Shot peening: shot peening pressure 135 MPa, nozzle distance from the sprocket surface 9 mm; mixed shot: steel shot with a particle size of 0.3 mm and ceramic shot with a particle size of 1.1 mm, mass ratio 3:1; shot peening coverage 200%; (3) Laser texturing after shot peening: laser power 50 W, scanning speed 100 mm / s, laser spot diameter 0.1 mm; (4) Plasma cleaning: in a mixed gas of argon and hydrogen with a volume ratio of 2:1, 0.3% helium is added based on the total volume of the mixed gas; a stepwise increasing voltage is applied to the bias, starting from -300V, increasing by -100V every 5 minutes until reaching -500V for surface activation; the total pressure of the mixed gas is maintained at 0.5 Pa, and the cleaning time is 25 minutes; (5) Gradient nitriding: First stage: temperature 480℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:1, pressure 0.8 Pa, treatment time 30 minutes; the carbon-containing gas is methane, the flow rate is 5% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.3% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulse mode with a frequency consistent with that of the plasma power supply; Transition stage: temperature 500℃, ammonia and nitrogen with a volume ratio of 1:1.5, pressure 1.0 Pa, treatment time 15 minutes; Second stage: temperature 500℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:2, pressure 1.2 Pa, treatment time 60 minutes; the carbon-containing gas is methane, the flow rate is 5% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.3% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulse mode with a frequency consistent with that of the plasma power supply; (6) Post-processing: Pulse denitriding: a pulse power supply with a frequency of 14 Hz and a duty cycle of 30% is used to eliminate the surface brittle layer; Cooling: the cooling rate is controlled at 20℃ / min, when the temperature drops to 200℃, it is kept for 30 minutes, and then it is continuously cooled to room temperature; Ion sputtering plating: the plating material is CrN, the plating thickness is 1μm, and the sputtering current is 2A. Example 3
[0036] (1) Before pretreatment, the sprocket is ultrasonically cleaned: the cleaning solution is a mixture of ethanol and water (volume ratio 3:2), the ultrasonic frequency is 40 kHz, and the cleaning time is 30 minutes; (2) Shot peening treatment: shot peening pressure 180 MPa, nozzle distance from sprocket surface 12 mm; mixed shot is steel shot with a particle size of 0.6 mm and ceramic shot with a particle size of 1.5 mm, mass ratio 3:1; shot peening coverage 250%; (3) After shot peening, laser texturing treatment is performed: laser power 80W, scanning speed 150mm / s, laser spot diameter 0.3mm; (4) Plasma cleaning: in a mixed gas of argon and hydrogen with a volume ratio of 2:1.2, 0.8% of helium is added based on the total volume of the mixed gas; a stepwise increasing voltage is applied as the bias voltage, starting from -300V, increasing by -100V every 5 minutes until reaching -800V for surface activation; the total pressure of the mixed gas is maintained at 1.2 Pa, and the cleaning time is 30 minutes; (5) Gradient nitriding: First stage: temperature 500℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:1, pressure 1.0 Pa, treatment time 45 minutes; the carbon-containing gas is methane, the flow rate is 8% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.5% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulse mode with a frequency consistent with that of the plasma power supply; Transition stage: temperature 500℃, ammonia and nitrogen with a volume ratio of 1:1.8, pressure 1.2 Pa, treatment time 20 minutes; Second stage: temperature 520℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:2, pressure 1.5 Pa, treatment time 70 minutes; the carbon-containing gas is methane, the flow rate is 8% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.5% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulse mode with a frequency consistent with that of the plasma power supply; (6) Post-processing: Pulse denitriding: a pulse power supply with a frequency of 20Hz and a duty cycle of 50% is used to eliminate the surface brittle layer; Cooling: the cooling rate is controlled at 30℃ / min, when the temperature drops to 250℃, it is kept for 40 minutes, and then it is continuously cooled to room temperature; Ion sputtering plating: the plating material is CrN, the plating thickness is 3μm, and the sputtering current is 4A. Example 4
[0037] (1) Before pretreatment, the sprocket is ultrasonically cleaned: the cleaning solution is a mixture of ethanol and water (volume ratio 3:2), the ultrasonic frequency is 40kHz, and the cleaning time is 27 minutes; (2) Shot peening treatment: shot peening pressure 160MPa, nozzle distance from sprocket surface 11mm; mixed shot is steel shot with a particle size of 0.5mm and ceramic shot with a particle size of 1.4mm, mass ratio 3:1; shot peening coverage 230%; (3) After shot peening, laser texturing treatment is performed: laser power 70W, scanning speed 140mm / s, laser spot diameter 0.25mm; (4) Plasma cleaning: in a mixed gas of argon and hydrogen with a volume ratio of 2:1.1, 0.6% of helium is added based on the total volume of the mixed gas; a stepwise increasing voltage is applied as the bias voltage, starting from -300V, increasing by -100V every 5 minutes until reaching -700V for surface activation; the total pressure of the mixed gas is maintained at 1.0 Pa, and the cleaning time is 29 minutes; (5) Gradient nitriding: First stage: temperature 495℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:1, pressure 0.95 Pa, treatment time 40 minutes; the carbon-containing gas is methane, the flow rate is 7% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.45% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulsed manner with a frequency consistent with that of the plasma power supply; Transition stage: temperature 500℃, ammonia and nitrogen with a volume ratio of 1:1.7, pressure 1.15 Pa, treatment time 19 minutes; Second stage: temperature 515℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:2, pressure 1.4 Pa, treatment time 68 minutes; the carbon-containing gas is methane, the flow rate is 7% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, the flow rate is 0.45% of the total flow rate of the nitrogen-containing gas, and it is introduced in a pulsed manner with a frequency consistent with that of the plasma power supply; (6) Post-treatment: Pulse denitriding: a pulse power supply with a frequency of 18Hz and a duty cycle of 45% is used to eliminate the surface brittle layer; Cooling: the cooling rate is controlled at 28℃ / min, when the temperature drops to 230℃, it is kept for 38 minutes, and then it continues to cool to room temperature; Ion sputtering plating: the plating material is CrN, the plating thickness is 2.5μm, and the sputtering current is 3.5A. Example 5
[0038] (1) Before pretreatment, the sprocket is ultrasonically cleaned: the cleaning solution is a mixture of ethanol and water (volume ratio 3:2), the ultrasonic frequency is 40kHz, and the cleaning time is 23 minutes; (2) Shot peening treatment: shot peening pressure 140MPa, nozzle distance from sprocket surface 10mm; mixed shot is steel shot with a particle size of 0.45mm and ceramic shot with a particle size of 1.2mm, mass ratio 3:1; shot peening coverage 210%; (3) After shot peening, laser texturing treatment is carried out: laser power 60W, scanning speed 120mm / s, laser spot diameter 0.2mm; (4) Plasma cleaning: in a mixed gas of argon and hydrogen with a volume ratio of 2:1, 0.5% of helium is added based on the total volume of the mixed gas; a stepwise increasing voltage bias is applied, starting from -300V, increasing by -100V every 5 minutes, until reaching -650V for surface activation; the total pressure of the mixed gas is maintained at 0.7Pa, and the cleaning time is 26 minutes; (5) Gradient nitriding: First stage: temperature 485℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:1, pressure 0.85Pa, treatment time 38 minutes; the carbon-containing gas is methane, with a flow rate of 6.5% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, with a flow rate of 0.35% of the total flow rate of the nitrogen-containing gas, in a pulsed manner, with a frequency consistent with that of the plasma power supply; Transition stage: temperature 500℃, ammonia and nitrogen with a volume ratio of 1:1.65, pressure 1.05Pa, treatment time 17 minutes; Second stage: temperature 505℃, ammonia and nitrogen in the nitrogen-containing gas with a volume ratio of 1:2, pressure 1.35Pa, treatment time 63 minutes; the carbon-containing gas is methane, with a flow rate of 6.5% of the total flow rate of the nitrogen-containing gas; at the same time, a small amount of oxygen is introduced, with a flow rate of 0.35% of the total flow rate of the nitrogen-containing gas, in a pulsed manner, with a frequency consistent with that of the plasma power supply; (6) Post-treatment: Pulse denitriding: a pulse power supply with a frequency of 16Hz and a duty cycle of 35% is used to eliminate the surface brittle layer; Cooling: the cooling rate is controlled at 22℃ / min, and when the temperature drops to 240℃, it is kept for 32 minutes, and then continues to cool to room temperature; Ion sputtering coating: the coating material is CrN, the coating thickness is 2.2μm, and the sputtering current is 3.2A.
[0039] Comparative Example 1 The treatment process provided in Example 1 is used, except that after step (2) shot peening treatment, laser texturing treatment is not performed.
[0040] Comparative Example 2 The treatment process provided in Example 1 is used, except that in step (4) gradient nitriding, the transition stage is not set, and it is directly switched from the first stage to the second stage.
[0041] Test Surface hardness test Test method: refer to GB / T4340.1-2009 "Metallic Materials Vickers Hardness Test Part 1: Test Method", use a Vickers hardness tester to test the surface hardness of the treated sprocket, load 100g, pressure holding time 15s, test 5 points for each sample, take the average value, the results are as follows: Table 1
[0042] As can be seen from Table 1, the surface hardness of the examples is higher than that of the comparative examples, indicating that the process of the application can effectively improve the surface hardness of the sprocket. Comparative Example 1 has lower surface roughness because it is not subjected to laser texturing, and the bonding force between the nitriding layer and the substrate is weak, resulting in a decrease in hardness; Comparative Example 2 has poor uniformity of the nitriding layer due to the lack of a transition stage, and the sudden change in temperature and pressure, thereby affecting the surface hardness.
[0043] Nitriding layer depth test Experimental method: According to GB / T11354-2005 "Determination of Nitriding Layer Depth and Metallographic Examination of Steel Parts", the cross section of the sprocket was polished, polished and etched (etchant was 4% nitric acid alcohol solution) by metallographic method, and the nitriding layer depth was measured under a metallographic microscope, 3 positions of each sample were measured, and the average value was taken, the results were as follows: Table 2
[0044] As can be seen from Table 2, the nitriding layer depth of the examples is greater than that of the comparative examples, indicating that the process of the application can promote the effective penetration of nitrogen atoms. Comparative Example 1 has a lower surface activity due to the lack of laser texturing, and the diffusion resistance of nitrogen atoms is large, resulting in a shallow nitriding layer; Comparative Example 2 has a sudden change in gas atmosphere during the nitriding process due to the lack of a transition stage, resulting in uneven diffusion of nitrogen atoms and a decrease in nitriding layer depth.
[0045] Wear resistance test Experimental method: According to GB / T12444.2-2006 "Metal Wear Test Method Part 2: Wear and Sliding Wear Test Method", the wear resistance test was carried out by using a pin-on-disc friction and wear testing machine, the friction pair was GCr15 steel ball (diameter 5mm), the load was 50N, the sliding speed was 0.5m / s, the wear time was 30min, and the wear amount (mass difference before and after wear) was calculated by weighing method (precision 0.1mg), the results were as follows: Table 3
[0046] As can be seen from Table 3, the wear amount of the examples is significantly lower than that of the comparative examples, indicating that the process of the application can greatly improve the wear resistance of the sprocket. Comparative Example 1 has a low surface hardness and a shallow nitriding layer, and the surface layer is easily worn during the wear process, resulting in an increase in wear amount; Comparative Example 2 has poor uniformity of the nitriding layer, and the local area has weak wear resistance, resulting in an increase in overall wear amount.
[0047] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.
Claims
1. A plasma nitriding treatment process for the surface of industrial sprockets, characterized in that, Includes the following steps: (1) Pretreatment: The sprocket is shot peened with a shot peening pressure of 135-180MPa and a nozzle distance of 9-12mm from the sprocket surface. The shot peening uses a mixture of steel shot and ceramic shot with a mixing mass ratio of 3:1 and a shot peening coverage of 200%-250%. (2) Plasma cleaning: In a mixed gas with an argon to hydrogen volume ratio of 2:1-1.2, a bias voltage is applied in a stepwise manner, starting from -300V and increasing by -100V every 5 minutes until -500V to -800V is reached for surface activation. The total pressure of the mixed gas is maintained at 0.5-1.2Pa, and the cleaning time is 25-30 minutes. (3) Gradient nitriding: Nitrogen-containing gas and carbon-containing gas are introduced, and the pressure is controlled in stages; (4) Post-treatment: Pulse denitrification is performed using a pulse power supply with a frequency of 14-20Hz and a duty cycle of 30%-50% to eliminate the brittle surface layer. The cooling rate is controlled at 20-30℃ / min.
2. The process according to claim 1, characterized in that: The steel shot has a particle size of 0.3-0.6 mm; The ceramic pellet size is 1.1-1.5mm.
3. The process according to claim 1, characterized in that: Before the pretreatment step, the sprocket is ultrasonically cleaned with a mixture of ethanol and water in a volume ratio of 3:
2. The cleaning time is 20-30 minutes and the ultrasonic frequency is 40kHz.
4. The process according to claim 1, characterized in that: After shot peening, the sprocket surface is subjected to laser texturing treatment with a laser power of 50-80W, a scanning speed of 100-150mm / s, and a laser spot diameter of 0.1-0.3mm.
5. The process according to claim 1, characterized in that: In the plasma cleaning step, 0.3%-0.8% helium is added to the mixed gas based on the total volume of the mixed gas.
6. The process according to claim 1, characterized in that: The gradient nitriding process includes: First stage: Temperature 480-500℃, ammonia to nitrogen volume ratio of 1:1 in nitrogen-containing gas, pressure 0.8-1.0 Pa, treatment time 30-45 minutes, the flow rate of carbon-containing gas is 5%-8% of the total flow rate of nitrogen-containing gas; Second stage: Temperature 500-520℃, ammonia to nitrogen volume ratio of 1:2 in nitrogen-containing gas, pressure 1.2-1.5Pa, treatment time 60-70 minutes, the flow rate of carbon-containing gas is 5%-8% of the total flow rate of nitrogen-containing gas; The carbon-containing gas is methane.
7. The process according to claim 6, characterized in that: Between the two stages of gradient nitriding, a transition stage is set up with a temperature of 500℃, an ammonia to nitrogen volume ratio of 1:1.5-1.8, a pressure of 1.0-1.2 Pa, and a treatment time of 15-20 minutes.
8. The process according to claim 1, characterized in that: In the gradient nitriding step, a trace amount of oxygen is introduced simultaneously with the introduction of nitrogen-containing gas and carbon-containing gas. The oxygen flow rate is 0.3%-0.5% of the total nitrogen-containing gas flow rate, and the oxygen is introduced in a pulsed manner with the pulse frequency consistent with the plasma power supply frequency.
9. The process according to claim 1, characterized in that: During the post-processing cooling process, when the temperature drops to 200-250℃, a heat preservation treatment is performed for 30-40 minutes, and then cooling continues to room temperature.
10. The process according to claim 1, characterized in that: In the post-processing, after pulse denitrification, the sprocket surface is subjected to ion sputtering coating. The coating material is CrN, the coating thickness is 1-3 μm, and the sputtering current is 2-4 A.