A composite nitriding coating structure for a sprocket wear device

Abstract

The utility model provides a kind of composite nitriding coating structure of sprocket wear-resistant device belongs to sprocket wear-resistant device technical field, the composite nitriding coating structure of this sprocket wear-resistant device includes sprocket matrix, composite nitriding layer and wear-resistant coating, the sprocket matrix is discoid, the outer circumferential surface of sprocket matrix is evenly distributed with multiple tooth grooves along the circumference, tooth peak is formed between each tooth groove, the composite nitriding layer is tightly covered in the outer circumferential surface of sprocket matrix, composite nitriding layer includes inner nitriding layer and outer nitriding layer, inner nitriding layer directly contacts sprocket matrix surface, outer nitriding layer covers in the outer surface of inner nitriding layer, the wear-resistant coating is completely covered in the outer surface of composite nitriding layer, the thickness of wear-resistant coating along tooth peak top is greater than the thickness of wear-resistant coating along tooth groove bottom;It can solve the problem that sprocket in the prior art works under high-speed heavy load working condition, tooth peak position bears the repeated impact and friction effect of chain, leading to the rapid wear of tooth peak surface.

Description

Technical Field

[0001] This utility model belongs to the technical field of sprocket wear-resistant devices, and specifically relates to a composite nitriding coating structure for a sprocket wear-resistant device. Background Technology

[0002] As a core component of chain drive systems, sprockets are widely used in numerous industrial fields such as machinery manufacturing, mining, metallurgical forging, port loading and unloading, and construction engineering. During transmission, they withstand repeated impacts, friction, and alternating stresses from the chain. Current technologies for wear-resistant sprocket treatment mainly employ surface hardening, carburizing, nitriding, or single-coating spraying. However, these methods have several shortcomings in practical applications. While surface hardening can improve surface hardness, the hardened layer is thin and exhibits a significant abrupt hardness gradient with the substrate, making it prone to fatigue cracking under alternating stress. Carburizing is time-consuming and the depth is difficult to control precisely. Although the bond between the carburized layer and the substrate is relatively good, the surface hardness improvement is limited, and rapid wear still occurs under high-speed, heavy-load conditions. The nitrided layer formed by single-nitriding is brittle and prone to chipping under impact loads. While single-coating spraying can quickly form a wear-resistant layer, the coating relies mainly on physical adsorption or mechanical bonding with the substrate, resulting in low bonding strength. Repeated impacts from the chain can easily lead to coating peeling. In addition, existing technologies typically use a uniform thickness coating distribution, failing to make targeted designs based on the stress characteristics of different parts of the sprocket. This results in insufficient protection for the tooth peaks and excessively thick coatings for the tooth grooves, leading to material waste. Overall, the wear resistance is not ideal, the sprocket has a short service life, and it needs to be replaced frequently, increasing the company's maintenance costs and equipment downtime. Utility Model Content

[0003] In view of this, the present invention provides a composite nitriding coating structure for a sprocket wear-resistant device. This structure can solve the problems in the prior art where, under high-speed and heavy-load conditions, the tooth peaks of sprockets are subjected to repeated impacts and friction from the chain, leading to rapid wear on the tooth peak surface. Traditional single nitriding treatment or single-layer coating technology suffers from insufficient bonding strength between the coating and the substrate, making the coating prone to peeling under alternating stress. At the same time, unreasonable coating thickness distribution leads to mismatched wear resistance in different parts of the sprocket, resulting in short sprocket lifespan, frequent replacement, increased equipment maintenance costs and downtime, and seriously affecting production efficiency.

[0004] This utility model is implemented as follows:

[0005] This utility model provides a composite nitriding coating structure for a sprocket wear-resistant device, comprising a sprocket substrate, a composite nitriding layer, and a wear-resistant coating. The sprocket substrate is disc-shaped, and multiple tooth grooves are evenly distributed circumferentially on its outer circumferential surface, with tooth peaks formed between each tooth groove. The composite nitriding layer is tightly covered on the outer circumferential surface of the sprocket substrate, and includes an inner nitriding layer and an outer nitriding layer. The inner nitriding layer directly contacts the surface of the sprocket substrate, and the outer nitriding layer covers the outer surface of the inner nitriding layer. The wear-resistant coating completely covers the outer surface of the composite nitriding layer, and the thickness of the wear-resistant coating along the top of the tooth peak is greater than the thickness of the wear-resistant coating along the bottom of the tooth groove. A diffusion bonding interface is formed between the inner nitriding layer and the sprocket substrate, and a gradient transition region is formed between the outer nitriding layer and the inner nitriding layer.

[0006] The technical effects of the composite nitriding coating structure of the sprocket wear-resistant device provided by this utility model are as follows: By setting the composite nitriding layer as a double-layer structure of inner and outer nitriding layers, and making the thickness of the wear-resistant coating at the top of the tooth peak greater than the thickness at the bottom of the tooth groove, stronger wear-resistant protection is achieved at the tooth peak position where the sprocket is subjected to the greatest force. At the same time, the diffusion bonding interface formed between the inner nitriding layer and the sprocket substrate, as well as the gradient transition area formed between the outer nitriding layer and the inner nitriding layer, effectively improve the bonding strength between the coating and the substrate, prevent the coating from peeling off during use, and significantly extend the service life of the sprocket.

[0007] Based on the above technical solution, the composite nitriding coating structure of the sprocket wear-resistant device of this utility model can be further improved as follows:

[0008] The thickness of the composite nitriding layer along the radial direction of the sprocket base gradually increases from the bottom of the tooth groove to the top of the tooth peak.

[0009] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by gradually increasing the thickness of the composite nitriding layer from the bottom of the tooth groove to the top of the tooth peak along the radial direction of the sprocket base, the tooth peak position is protected by a thicker nitriding layer when the sprocket is subjected to the impact force of the chain, which effectively resists wear and fatigue damage. At the same time, the bottom of the tooth groove maintains a relatively thin nitriding layer thickness, avoiding stress concentration caused by excessive nitriding layer, thereby improving the overall impact resistance and fatigue life of the sprocket.

[0010] Furthermore, the diffusion interface between the internal nitriding layer and the sprocket substrate is wavy, with the wave crests located at the bottom of the tooth groove and the wave troughs located at the sides of the tooth crests.

[0011] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the diffusion bonding interface between the inner nitriding layer and the sprocket substrate wavy, with the wave crests located at the corresponding positions at the bottom of the tooth groove and the wave troughs located at the corresponding positions on the sides of the tooth crests, the contact area between the nitriding layer and the substrate is significantly increased, the mechanical interlocking force of the bonding interface is improved, and the interface slippage or delamination phenomenon of the nitriding layer under alternating stress is effectively prevented, thereby further enhancing the overall stability and reliability of the coating structure.

[0012] Furthermore, the gradient transition region formed between the outer surface of the outer nitriding layer and the outer surface of the inner nitriding layer has a sawtooth cross-section, with the tips of the sawtooth cross-section pointing towards the center of the sprocket base.

[0013] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the gradient transition region between the outer surface of the outer nitriding layer and the outer surface of the inner nitriding layer have a sawtooth cross-section, and making the tooth tips of the sawtooth cross-section point towards the center of the sprocket base, a connection form similar to an anchoring structure is formed, which generates a mechanical interlocking effect between the outer nitriding layer and the inner nitriding layer, effectively preventing relative sliding between the two layers, improving the bonding strength inside the composite nitriding layer, and making the entire nitriding layer bear external loads as a whole.

[0014] Furthermore, the wear-resistant coating forms an arc-shaped protrusion at the top of the tooth peak, and the radius of curvature of the arc-shaped protrusion is smaller than the radius of curvature of the original surface at the top of the tooth peak.

[0015] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the wear-resistant coating form an arc-shaped protrusion on the top of the tooth peak, and the radius of curvature of the arc-shaped protrusion is smaller than the radius of curvature of the original surface of the tooth peak, the contact area when the top of the tooth peak contacts the chain is appropriately reduced, thereby reducing the frictional resistance between the chain and the sprocket. At the same time, the arc-shaped protrusion can guide the chain to transition smoothly, reduce the impact vibration of the chain during meshing, extend the service life of the chain and sprocket, and reduce the noise of the transmission system.

[0016] Furthermore, the wear-resistant coating forms symmetrically distributed thickened areas on both sides of the tooth peaks of each tooth groove. The thickened areas have a trapezoidal cross-section along the tooth peak height direction, with the upper base of the trapezoidal cross-section located near the top of the tooth peak and the lower base located near the bottom of the tooth groove.

[0017] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the wear-resistant coating form a symmetrically distributed thickened area on both sides of the tooth peak side of each tooth groove, and making the thickened area have a trapezoidal cross section along the tooth peak height direction, when the chain makes lateral contact with the tooth peak side, the thickened area of ​​the trapezoidal cross section provides stronger resistance to lateral wear, effectively protecting the tooth peak side from being worn by the chain. At the same time, the trapezoidal cross section structure makes the stress distribution more uniform, avoiding local overload of the coating and causing cracks or peeling.

[0018] Furthermore, the interface between the composite nitriding layer and the wear-resistant coating is distributed in an inclined manner on the side of the tooth peak, and the inclination angle of the inclined distribution gradually changes along the height direction of the tooth peak.

[0019] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the bonding interface between the composite nitriding layer and the wear-resistant coating inclined on the side of the tooth peak, and the inclination angle gradually changing along the tooth peak height direction, a non-parallel interface structure is formed, which effectively eliminates the stress concentration phenomenon at the interface, makes the transmission of external load between the two layers smoother, reduces the risk of interface peeling, and improves the durability and reliability of the coating system under complex working conditions.

[0020] Furthermore, a mounting hole is provided at the center of the sprocket base, the axis of the mounting hole coincides with the geometric center axis of the sprocket base, and the composite nitriding layer extends to cover the inner wall surface of the mounting hole.

[0021] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by extending the composite nitriding layer to cover the inner wall surface of the mounting hole, the inner wall of the mounting hole also has good wear resistance when the sprocket is engaged with the shaft, preventing the mounting hole from being worn by the shaft during long-term use and causing loosening of the clearance fit, thus ensuring the transmission accuracy and stability between the sprocket and the shaft. At the same time, the nitriding layer on the inner wall of the mounting hole can also improve the surface hardness of the hole wall and enhance the wear resistance and fatigue resistance.

[0022] Furthermore, the sprocket base is made of alloy steel, the inner nitriding layer is composed of iron nitride phase, the outer nitriding layer is composed of nitrogen-carbon co-diffusion phase, and the wear-resistant coating is made of ceramic composite material.

[0023] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the sprocket base material of alloy steel, the inner nitriding layer of iron nitride phase, the outer nitriding layer of nitrogen-carbon co-diffusion phase, and the wear-resistant coating of ceramic composite material, a gradient material structure is formed from the base material to the surface, where the hardness gradually increases and the toughness gradually decreases. This ensures that the base material has good strength and toughness, while the surface has extremely high hardness and wear resistance, achieving an optimized match of material properties and significantly improving the overall performance of the sprocket.

[0024] Furthermore, the surface roughness of the wear-resistant coating gradually decreases from the top of the tooth peak to the bottom of the tooth groove, the surface of the top of the tooth peak has a micro-protruding texture structure, and the surface of the bottom of the tooth groove has a smooth mirror finish.

[0025] The beneficial effects of adopting the above-mentioned improvement scheme are as follows: by making the surface roughness of the wear-resistant coating gradually decrease from the top of the tooth peak to the bottom of the tooth groove, and making the top of the tooth peak have a micro-protruding texture structure and the bottom of the tooth groove have a smooth mirror surface, differentiated surface characteristics are achieved at different locations. The micro-protruding texture at the top of the tooth peak can store lubricating oil and form an oil film, reducing the probability of dry friction, while the smooth surface at the bottom of the tooth groove reduces the accumulation of dirt and wear debris, facilitates self-cleaning, and improves the overall working efficiency and reliability of the sprocket.

[0026] Compared with existing technologies, the beneficial effects of the composite nitriding coating structure of the sprocket wear-resistant device provided by this utility model are as follows: This utility model achieves a strong bond between the coating and the substrate by designing a double-layer structure for the composite nitriding layer, forming a diffusion bonding interface between the inner nitriding layer and the sprocket substrate, and a gradient transition region between the outer and inner nitriding layers, effectively solving the technical problem of coating peeling. By making the thickness of the wear-resistant coating at the top of the tooth peak greater than the thickness at the bottom of the tooth groove, and by designing the composite nitriding layer to gradually increase in thickness radially from the tooth groove to the tooth peak, the tooth peak area of ​​the sprocket, which experiences the greatest stress, receives the strongest wear-resistant protection, achieving an optimized distribution of coating thickness. By designing special shapes such as wavy and sawtooth at the bonding interface, the mechanical interlocking force and interlocking effect of the interface are increased, further improving the overall stability of the coating system. By forming an arc-shaped protrusion and a thickened area with a trapezoidal cross-section at the top of the tooth peak, the contact state between the chain and the sprocket is optimized, reducing frictional resistance and impact vibration. By employing a material combination of an alloy steel matrix, an inner layer of iron nitride phase, an outer layer of nitrocarbon co-diffusion phase, and a wear-resistant layer of ceramic composite material, a gradient material structure is formed, achieving an optimized match of strength, toughness, and hardness. This overall technical solution significantly improves the sprocket's wear resistance, impact resistance, and service life, reduces maintenance frequency and operating costs, and enhances the reliability and efficiency of the transmission system. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments of this utility model will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 A schematic diagram of a composite nitriding coating structure for a sprocket wear-resistant device;

[0029] Figure 2 This is a schematic diagram of the structure between the outer circumference of the sprocket base and the composite nitriding layer.

[0030] The attached diagram lists the components represented by each number as follows:

[0031] 10. Sprocket base; 20. Composite nitriding layer; 30. Wear-resistant coating. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0033] like Figure 1-2 The diagram shows a structural schematic of a composite nitriding coating structure for a sprocket wear-resistant device provided by this utility model. The diagram includes a sprocket substrate 10, a composite nitriding layer 20, and a wear-resistant coating 30. The sprocket substrate is disc-shaped, and multiple tooth grooves are evenly distributed along the circumferential direction on its outer circumferential surface. A tooth peak is formed between each tooth groove. The composite nitriding layer is tightly covered on the outer circumferential surface of the sprocket substrate. The composite nitriding layer includes an inner nitriding layer and an outer nitriding layer. The inner nitriding layer directly contacts the surface of the sprocket substrate, and the outer nitriding layer covers the outer surface of the inner nitriding layer. The wear-resistant coating completely covers the outer surface of the composite nitriding layer. The thickness of the wear-resistant coating along the top of the tooth peak is greater than the thickness along the bottom of the tooth groove. A diffusion bonding interface is formed between the inner nitriding layer and the sprocket substrate, and a gradient transition region is formed between the outer nitriding layer and the inner nitriding layer.

[0034] In the above technical solution, the thickness of the composite nitriding layer along the radial direction of the sprocket base gradually increases from the bottom of the tooth groove to the top of the tooth peak.

[0035] Furthermore, in the above technical solution, the diffusion bonding interface between the internal nitriding layer and the sprocket substrate is wavy, with the wave crests located at the corresponding positions at the bottom of the tooth groove and the wave troughs located at the corresponding positions on the sides of the tooth crests.

[0036] Furthermore, in the above technical solution, the gradient transition region formed between the outer surface of the outer nitriding layer and the outer surface of the inner nitriding layer has a sawtooth cross-section, and the tips of the sawtooth cross-section point towards the center of the sprocket base.

[0037] Furthermore, in the above technical solution, the wear-resistant coating forms an arc-shaped protrusion on the top of the tooth peak, and the radius of curvature of the arc-shaped protrusion is smaller than the radius of curvature of the original surface of the tooth peak.

[0038] Furthermore, in the above technical solution, the wear-resistant coating forms symmetrically distributed thickened areas on both sides of the tooth peaks of each tooth groove. The thickened areas have a trapezoidal cross-section along the tooth peak height direction, with the upper base of the trapezoidal cross-section located near the top of the tooth peak and the lower base located near the bottom of the tooth groove.

[0039] Furthermore, in the above technical solution, the bonding interface between the composite nitriding layer and the wear-resistant coating is distributed in an inclined manner on the side of the tooth peak, and the inclination angle of the inclined distribution gradually changes along the tooth peak height direction.

[0040] Furthermore, in the above technical solution, a mounting hole is provided at the center of the sprocket base, the axis of the mounting hole coincides with the geometric center axis of the sprocket base, and the composite nitriding layer extends to cover the inner wall surface of the mounting hole.

[0041] Furthermore, in the above technical solution, the sprocket base is made of alloy steel, the inner nitriding layer is composed of iron nitride phase, the outer nitriding layer is composed of nitrogen-carbon co-diffusion phase, and the wear-resistant coating is made of ceramic composite material.

[0042] Furthermore, in the above technical solution, the surface roughness of the wear-resistant coating gradually decreases from the top of the tooth peak to the bottom of the tooth groove, the surface of the top of the tooth peak has a micro-protruding texture structure, and the surface of the bottom of the tooth groove has a smooth mirror finish.

[0043] The following is a specific embodiment 1 of this utility model: In this embodiment, the sprocket base is made of 40Cr alloy steel, with an outer diameter of 280mm, 25 teeth, a tooth groove depth of 18mm, and a tooth peak width of 12mm. A 60mm diameter mounting hole is provided at the center of the sprocket base, with the axis of the mounting hole coinciding with the geometric center axis of the sprocket base. The thickness of the sprocket base is 35mm. After the sprocket base is machined, it undergoes surface pretreatment using alumina sandblasting at a pressure of 0.4MPa for 15 minutes to remove surface oxide scale and oil. Then, it is ultrasonically cleaned with acetone solution for 10 minutes to ensure surface cleanliness. After pretreatment, the sprocket substrate is placed in a vacuum nitriding furnace, the furnace temperature is raised to 520℃, a mixture of ammonia and nitrogen is introduced at a flow rate ratio of 3:1, and the holding time is 8 hours to carry out the first stage of nitriding treatment, forming an inner nitriding layer with a thickness of 0.15mm to 0.25mm. The inner nitriding layer is mainly composed of γ-ferric nitride phase and ε-ferric nitride phase, forming a diffusion bonding interface with the sprocket substrate. The diffusion bonding interface is wavy, with a wave wavelength of 2mm to 3mm and a wave height of 0.02mm to 0.04mm. After the first stage of nitriding is completed, without removing the sprocket base, the atmosphere composition is adjusted directly inside the furnace, increasing propane gas. The gas flow ratio is adjusted to ammonia, nitrogen, and propane in a 2:1:1 ratio. The furnace temperature is lowered to 480℃ and held for 6 hours. The second stage of nitriding is then performed, forming an external nitrided layer with a thickness of 0.08mm to 0.15mm. This external nitrided layer mainly consists of ε-carbonitride and ζ-carbonitride phases. A gradient transition region is formed between the external and internal nitrided layers, with a thickness of 0.03mm to 0.06mm and a serrated cross-section. The tooth pitch is 0.5mm to 0.8mm, and the tooth height is 0.015mm to 0.025mm, with the tooth tips pointing towards the center of the sprocket base. After nitriding, the gas supply is shut off, and the sprocket is cooled in the furnace to 150℃ before being removed and air-cooled to room temperature. Subsequently, a wear-resistant coating was prepared on the surface of the composite nitrided layer using plasma spraying. The wear-resistant coating material was a composite powder of alumina ceramic and zirconia ceramic in a mass ratio of 7:3. The spraying current was 600A, the spraying voltage was 70V, the spraying distance was 120mm, and the powder feed rate was 40g / min along the top of the tooth peak and 25g / min along the bottom of the tooth groove. This resulted in a wear-resistant coating thickness of 0.18mm to 0.25mm at the top of the tooth peak and 0.08mm to 0.12mm at the bottom of the tooth groove. A thickened area with a trapezoidal cross-section was formed on the side of the tooth peak, with an upper base width of 3mm, a lower base width of 8mm, and a height of 15mm. After spraying, the sprocket was placed in an annealing furnace at 400℃ for 2 hours for stress relief treatment, and then cooled to room temperature in the furnace.Finally, the sprocket surface is finished. The top of the tooth peak is lightly ground with a ceramic grinding wheel to form an arc-shaped protrusion with a radius of curvature of 8mm to 10mm. Then, the top of the tooth peak is polished with silicon carbide sandpaper with a grit of 1200 mesh to form a micro-protruding texture structure with a surface roughness Ra of 1.2μm to 1.8μm. The bottom of the tooth groove is polished with a polishing cloth wheel to form a smooth mirror-like surface with a surface roughness Ra of 0.3μm to 0.5μm.

[0044] The following is another specific embodiment 2 of this utility model: This embodiment 2 is based on embodiment 1, and the preparation process of the composite nitriding layer is optimized and improved. During the first stage of nitriding treatment, a magnetic field auxiliary device is added in the furnace. The magnetic field strength is 0.15T to 0.25T, and the magnetic field lines are perpendicular to the surface of the sprocket base. By using the directional effect of the magnetic field on nitrogen ions, the diffusion bonding interface between the inner nitriding layer and the sprocket base forms a more obvious wave-like distribution. The wavelength of the wave is reduced to 1.5mm to 2.2mm, and the wave height is increased to 0.03mm to 0.06mm, which increases the mechanical interlocking area of ​​the interface. In the second stage of nitriding and carbonization treatment, a pulsed atmosphere control method is adopted, and the gas flow ratio is switched every 30 minutes. This creates multiple tiny concentration gradient steps in the gradient transition area between the outer and inner nitrided layers, further improving the interlayer bonding strength. Simultaneously, during the wear-resistant coating spraying process, a robot controls the spray gun trajectory, moving the spray gun in a spiral manner along the tooth peak surface to achieve precise control of the coating thickness. This makes the thickened area of ​​the trapezoidal cross-section on the tooth peak side more uniformly distributed, with the upper bottom width controlled between 2.5mm and 3.5mm and the lower bottom width controlled between 7.5mm and 8.5mm, improving the lateral wear resistance of the tooth peak side.

[0045] The following is another specific embodiment 3 of this utility model: This embodiment 3 is based on embodiment 1. After the wear-resistant coating is prepared, a laser surface modification process is added. A continuous wave fiber laser is used to scan the wear-resistant coating on the top of the tooth peak. The laser power is 800W to 1200W, the scanning speed is 5m to 8m per minute, and the spot diameter is 3mm to 5mm. The laser scanning causes the surface of the wear-resistant coating to melt and solidify rapidly, forming a laser remelted layer with a thickness of 0.015mm to 0.025mm. The structure of the laser remelted layer is more compact, and the grain size is reduced to the nanoscale, which significantly improves the surface hardness and wear resistance of the tooth peak. At the same time, during the laser scanning process, a nitrogen protective atmosphere is introduced to form a nitride strengthening phase on the surface of the remelted layer, which further enhances the wear resistance. The surface hardness of the tooth peak after laser treatment reaches HV1800 to HV2200, which is 15% to 20% higher than the surface hardness of the wear-resistant coating without laser treatment, so that the sprocket can still maintain good wear resistance under extreme working conditions.

[0046] Specifically, the principle of this invention is as follows: This invention adopts a multi-layer structure design combining a composite nitriding layer and a wear-resistant coating. Through the diffusion bonding interface formed between the inner nitriding layer and the sprocket substrate, the diffusion of nitrogen atoms into the substrate during nitriding creates a metallurgical bond between the inner nitriding layer and the substrate, eliminating the obvious interface between the traditional coating and substrate, and fundamentally improving the bonding strength. The gradient transition region formed between the outer and inner nitriding layers, by controlling the nitriding process parameters to ensure a gradient distribution of nitrogen concentration, avoids abrupt changes in interlayer hardness, making stress transmission smoother and reducing the risk of interface delamination. The diffusion bonding interface between the inner nitriding layer and the sprocket substrate is designed with a wavy distribution, significantly increasing the contact area and improving the mechanical interlocking force, making the nitriding layer less prone to slippage under tangential stress. The gradient transition region between the outer and inner nitriding layers adopts a sawtooth cross-sectional shape, forming a mechanical interlocking structure similar to anchoring, further enhancing the interlayer bonding. The wear-resistant coating is thicker at the top of the tooth peak than at the bottom of the tooth groove, and the composite nitriding layer thickness gradually increases from the tooth groove to the tooth peak. This design matches the coating thickness distribution with the stress distribution of the sprocket, providing the strongest protection at the tooth peak where the maximum load is borne, thus optimizing material utilization. The arc-shaped protrusion at the top of the tooth peak improves the contact geometry between the chain and the sprocket, reduces the peak contact stress, and minimizes localized wear. The thickened area with a trapezoidal cross-section provides specialized protection against lateral wear on the tooth peak sides, significantly extending the service life of the tooth peak. By employing a multi-layered material combination of alloy steel matrix, iron nitride phase, nitrocarburized phase, and ceramic composite material, a gradient material structure with gradually increasing hardness from the inside to the outside is formed. This ensures both the strength and toughness of the matrix and the extremely high hardness and wear resistance of the surface, achieving optimized performance matching. This addresses the problems of rapid sprocket wear and coating peeling from both material and structural perspectives.

[0047] In use, the sprocket substrate is first pretreated by sandblasting or chemical cleaning to remove oil, scale, and impurities, ensuring surface cleanliness. Then, the pretreated sprocket substrate is placed in a nitriding furnace, and a nitrogen-containing atmosphere is introduced. The furnace temperature and time are controlled for the first stage of nitriding, forming an inner nitriding layer. This allows nitrogen atoms to diffuse into the substrate and react metallurgically with the substrate material, forming a diffusion interface. Next, the atmosphere composition of the nitriding furnace is adjusted, and carbon source gas is added for the second stage of nitrocarburizing, forming an outer nitriding layer. Process parameters are controlled to create a gradient transition region between the outer and inner nitriding layers. After nitriding, the sprocket substrate is removed and cooled to room temperature. A wear-resistant coating is prepared on the surface of the composite nitriding layer using plasma spraying or physical vapor deposition. By adjusting the spraying parameters or deposition rate, a thicker coating is formed at the top of the tooth peaks and a thinner coating at the bottom of the tooth grooves, achieving a gradient distribution of coating thickness. After the coating is prepared, the sprocket undergoes overall heat treatment to eliminate residual stress and improve the bonding strength between the coating and the substrate. Finally, the sprocket surface is finished and polished to create a micro-protruding textured structure at the top of the tooth peaks and a smooth mirror-like surface at the bottom of the tooth grooves. This completes the preparation of the composite nitriding coating structure for the entire sprocket wear-resistant device. The prepared sprocket is then installed by fitting it with the drive shaft through mounting holes and put into actual working conditions.

Claims

1. A composite nitriding coating structure for a sprocket wear-resistant device, characterized in that, The sprocket assembly comprises a sprocket base, a composite nitriding layer, and a wear-resistant coating. The sprocket base is disc-shaped, and multiple tooth grooves are evenly distributed circumferentially on its outer circumferential surface, with tooth peaks formed between each tooth groove. The composite nitriding layer is tightly coated on the outer circumferential surface of the sprocket base and includes an inner nitriding layer and an outer nitriding layer. The inner nitriding layer directly contacts the surface of the sprocket base, while the outer nitriding layer covers the outer surface of the inner nitriding layer. The wear-resistant coating completely covers the outer surface of the composite nitriding layer. The thickness of the wear-resistant coating along the top of the tooth peak is greater than the thickness along the bottom of the tooth groove. A diffusion bonding interface is formed between the inner nitriding layer and the sprocket base, and a gradient transition region is formed between the outer nitriding layer and the inner nitriding layer.

2. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 1, characterized in that, The thickness of the composite nitriding layer gradually increases from the bottom of the tooth groove to the top of the tooth peak along the radial direction of the sprocket base.

3. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 2, characterized in that, The diffusion interface between the internal nitriding layer and the sprocket substrate is wavy, with the wave crests located at the bottom of the tooth groove and the wave troughs located at the sides of the tooth crests.

4. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 3, characterized in that, The gradient transition region formed between the outer surface of the outer nitriding layer and the outer surface of the inner nitriding layer has a sawtooth cross-section, with the tips of the sawtooth cross-section pointing towards the center of the sprocket base.

5. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 4, characterized in that, The wear-resistant coating forms an arc-shaped protrusion at the top of the tooth peak, and the radius of curvature of the arc-shaped protrusion is smaller than the radius of curvature of the original surface at the top of the tooth peak.

6. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 5, characterized in that, The wear-resistant coating forms symmetrically distributed thickened areas on both sides of the tooth peaks of each tooth groove. The thickened areas have a trapezoidal cross-section along the tooth peak height direction, with the upper base of the trapezoidal cross-section located near the top of the tooth peak and the lower base located near the bottom of the tooth groove.

7. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 6, characterized in that, The interface between the composite nitriding layer and the wear-resistant coating is distributed in an inclined manner on the side of the tooth peak, and the inclination angle of the inclined distribution gradually changes along the height direction of the tooth peak.

8. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 7, characterized in that, The sprocket base has a mounting hole at its center, the axis of which coincides with the geometric center axis of the sprocket base, and the composite nitriding layer extends to cover the inner wall surface of the mounting hole.

9. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 8, characterized in that, The sprocket base is made of alloy steel, the inner nitriding layer is composed of iron nitride phase, the outer nitriding layer is composed of nitrogen-carbon co-diffusion phase, and the wear-resistant coating is made of ceramic composite material.

10. The composite nitriding coating structure of the sprocket wear-resistant device according to claim 9, characterized in that, The surface roughness of the wear-resistant coating gradually decreases from the top of the tooth peak to the bottom of the tooth groove. The surface of the top of the tooth peak has a micro-protruding texture structure, and the surface of the bottom of the tooth groove has a smooth mirror finish.

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