Composite coating surface treatment production line and electroplating process

Abstract

According to the composite coating surface treatment production line and the electroplating technology, efficient and uniform preparation of a ceramic coating on the inner wall of a cylinder hole of an engine cylinder body is achieved through full-process cooperation of electrolyte circulating supply, cylinder body precise positioning, electric field driving ceramic deposition and post-treatment strengthening. The method has the core advantages that the uniformity of a plating layer is guaranteed through mechanical limiting of the positioning clamp and coaxial flowing of the electrolyte, the utilization rate of ceramic particles is improved through an electrophoretic deposition mechanism, the coating performance is enhanced through a post-treatment process, and finally the wear resistance of the cylinder hole is improved by more than 50% compared with a traditional chromium plating layer.

Description

Technical Field

[0001] The present invention belongs to the technical field of surface treatment of engine parts, and specifically relates to a ceramic coating composite coating surface treatment production line for engine cylinder bores, and an electroplating process based on the production line. Background Art

[0002] As a core component of power systems such as automobiles and construction machinery, engines are prone to wear and tear on the inner walls of their cylinder bores due to the frequent friction caused by the reciprocating piston motion. This damage seriously affects the engine's sealing, power, and service life. To improve the wear resistance of cylinder bores, surface coating technologies (such as hard chrome electroplating and ceramic spray coatings) are commonly used. However, traditional electroplating processes suffer from insufficient adhesion between the coating and the substrate, uneven coating thickness, and low electrolyte circulation efficiency. While ceramic coatings offer the advantages of high hardness and wear resistance, their complex preparation process makes uniform deposition difficult on the complex inner surface of the cylinder bore.

[0003] Therefore, it is urgent to develop a cylinder bore ceramic coating surface treatment production line and supporting process with reasonable structural design, good coating uniformity and strong bonding force to solve the shortcomings of the existing technology. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a composite coating surface treatment production line and electroplating process. By optimizing the structural design of the production line, the precise circulation of the electrolyte and the uniform electroplating of the inner surface of the cylinder hole can be achieved. At the same time, combined with specific process parameters, the bonding strength and wear resistance of the ceramic coating and the cylinder hole matrix can be improved.

[0005] To achieve the above objectives, the present invention provides the following technical solutions: 1. Composite coating surface treatment production line The production line of the present invention is used for ceramic coating of cylinder bores of engine cylinder blocks, and comprises an electrolyte circulation system, a box body and an engine cylinder block positioning fixture; the positioning fixtures are arranged in a matrix and installed at the bottom of the box body, and the engine cylinder block is placed on the positioning fixture; the bottom of the box body is fixed on a base; the electrolyte circulation system comprises a water tank, a water pump, a water outlet pipe and a water collecting tank at the bottom of the box body; the water collecting tank is connected to the bottom of the box body and is connected to the water tank through a pipe; the water tank is connected to the water pump through a water pipe, the water pump is connected to the water outlet pipe through a water pipe, and the water outlet pipe is connected to the positioning fixture in a one-to-one correspondence; the The positioning fixture includes a base, which is provided with a water outlet groove corresponding to the cylinder hole of the cylinder body, and the anode rod is inserted into the water outlet groove; the lower end face of the engine cylinder body is tightly fitted with the upper end face of the base, an annular limiting step extends from the end face of the cylinder hole of the cylinder body, and an annular positioning ring is provided at the groove of the water outlet groove, and the limiting step is inserted in the positioning ring to realize the positioning of the cylinder body; the anode rod is located at the center axis position of the cylinder hole, and the water outlet groove is connected with the water outlet pipe through a water pipe. The electrolyte enters the water outlet groove through the water outlet pipe and overflows into the cylinder hole until the cylinder hole is filled. After the anode rod and the cylinder body are energized by the electrolyte, the inner wall of the cylinder hole is electroplated.

[0006] Furthermore, the base of the positioning fixture is arranged in a rectangular or circular matrix, each base corresponds to a cylinder hole, and the number of water outlet grooves is consistent with the number of cylinder holes in the cylinder body; the length of the anode rod is slightly larger than the depth of the cylinder hole or is level, ensuring that the anode rod is fully inserted into the cylinder hole during electroplating.

[0007] Furthermore, a filtering device is provided in the water collecting tank for filtering impurities in the electrolyte to prevent the impurities from entering the cylinder hole during circulation and affecting the quality of the plating; a heating device and a temperature sensor are provided in the water tank for controlling the temperature of the electrolyte.

[0008] 2. Electroplating process The electroplating process of the present invention is used for the cylinder bore of an engine cylinder block, and comprises the following steps: 1. Ceramic powder preparation: Alumina, silicon carbide or silicon nitride and other ceramic powders are selected and prepared through ball milling and classification processes to produce ceramic powders with uniform particle size (1-5μm) and purity ≥99%; 2. Metal substrate surface treatment: Sandblast the inner wall of the engine cylinder bore to remove scale and oil stains and perform plasma activation treatment (surface energy increased to ≥50mN / m) to improve the bonding strength between the ceramic coating and the substrate; 3. Preparation of electrolyte: Use deionized water as solvent, add ceramic powder (concentration 5-15g / L), complexing agent (sodium citrate, concentration 10-20g / L), conductive salt (sodium sulfate, concentration 50-60g / L) and pH regulator (sodium hydroxide, adjust pH to 8-10), stir evenly and filter to remove impurities; 4. Determination of electroplating process parameters: Determine the current density (2-5A / dm²), electrolysis time (30-60min), temperature (40-60℃) and the distance between the anode rod and the cylinder (5-10mm) through orthogonal experiments; 5. Electroplating ceramic coating: Fix the surface-treated cylinder body on the positioning fixture, insert the anode rod into the center axis of the cylinder hole, start the electrolyte circulation system to fill the cylinder hole with electrolyte; turn on the power supply, connect the anode rod to the positive pole of the power supply, and connect the cylinder body to the negative pole of the power supply. Electroplating is carried out according to the set parameters. Ceramic powder is deposited on the inner wall of the cylinder hole under the action of the electric field to form a coating; 6. Post-treatment of coating: After electroplating is completed, remove the cylinder body and clean the residual electrolyte on the surface with deionized water. Then dry (80-100℃, 30min) and sinter (800-1000℃, 2h) to improve the density and hardness of the coating. Beneficial effects

[0009] The production line of this invention achieves batch processing of cylinder blocks through a matrix of positioning fixtures. The coordination of positioning rings and stop steps ensures accurate positioning of the cylinder blocks. The coaxial design of the water outlet trough and anode rod ensures uniform electrolyte delivery to the cylinder bore, avoiding blind spots during electroplating. The electrolyte circulation system, through filtration and temperature control in the sump, ensures stable electrolyte composition and enhances plating uniformity. Combined with an optimized electroplating process, the ceramic coating bonded to the cylinder bore substrate enhances strength, significantly increases hardness, and significantly reduces wear rate compared to traditional chrome plating, significantly improving the wear resistance and service life of the engine cylinder block.

[0010] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 A perspective view of a specific embodiment of the present invention; Figure 2 A cross-sectional view of a specific embodiment of the present invention; Figure 3 A three-dimensional diagram of the coordination between the positioning fixture and the cylinder body in a specific embodiment of the present invention; Figure 4 for Figure 3 sectional view of Figure 5 for Figure 4 Enlarged view of A in the middle;.

[0012] Description of reference numerals: 1-water tank; 2-water pump; 3-water outlet pipe; 4-tank; 5-water collecting trough; 6-base; 7-positioning fixture; 71-base; 72-water outlet trough; 73-anode rod; 75-positioning ring; 8-engine cylinder block; 81-cylinder hole; 82-limiting step. DETAILED DESCRIPTION

[0013] The present invention is specifically described below through examples, which are only used to further illustrate the present invention and should not be understood as limiting the scope of protection of the present invention.

[0014] like Figure 1-5 As shown, the production line consists of a box 4, the bottom of which is fixed to a base 6. A water collection tank 5 is located at the bottom of the box 4. This water collection tank 5 is connected to a water tank 1 via a pipe, which is equipped with a filter device (such as a filter screen). A heating device and a temperature sensor are installed in the water tank 1. An external water pump 2 is connected to the water pump 2 via an outlet pipe 3, which is connected to a matrix-arranged positioning fixture 7.

[0015] The base 71 of the positioning fixture 7 is a rectangular array (21 per row, for a total of 2 rows), with two water outlet troughs 72 (corresponding to the two cylinder holes of the cylinder body) provided on each base 71. The water outlet trough 72 is a stepped trough, with an anode rod 73 (made of a titanium-based coated anode) mounted on the central protrusion at the bottom of the trough. An annular positioning ring 75 (with an inner diameter that is 0.1-0.2mm clear of the outer diameter of the limiting step 82 of the cylinder body 8) is provided at the notch of the water outlet trough 72. When the lower end face of the cylinder body 8 is in contact with the upper end face of the base 71, the limiting step 82 is inserted into the positioning ring 75 to achieve radial positioning. The water outlet trough 72 is connected to the water outlet pipe 3 via a water pipe. The electrolyte flows from the water outlet pipe 3 into the water outlet trough 72 and then overflows into the cylinder hole 81 until it is full.

[0016] Electroplating process example Taking a certain model of automobile engine cylinder block (made of cast iron) as an example, the specific process steps are as follows: 1. Preparation of ceramic powder: α-alumina powder (purity 99.5%) was selected and ball-milled for 12 h (rotation speed 1500 rpm), and then graded to obtain a powder with a particle size of 2-4 μm; 2. Cylinder surface treatment: The inner wall of the cylinder hole 81 is cleaned by sandblasting (pressure 0.4MPa, 80-mesh corundum sand), and then activated by plasma equipment (power 5kW, argon flow rate 20L / min). The surface energy is detected to be 55mN / m. 3. Preparation of electrolyte: Weigh 10g of alumina powder, 15g of sodium citrate, and 75g of sodium sulfate and dissolve them in 1L of deionized water. Stir for 30min (500rpm), filter (100-mesh filter) to a pH of 9. 4. Parameter determination: Through orthogonal experiments, the current density is determined to be 3A / dm² (calculated by the projected area of ​​the cylinder hole), the electrolysis time is 45 minutes, the temperature is 50°C, and the distance between the anode rod and the cylinder body is 8mm; 5. Electroplating process: Fix the cylinder body 8 to the positioning fixture 7, insert the anode rod 73 into the center axis of the cylinder hole 81 (deviation ≤ 0.5mm), start the electrolyte circulation system (flow rate 1.5m³ / h), after power is turned on, connect the anode rod 73 to the positive pole of the power supply (voltage 12V), and connect the cylinder body 8 to the negative pole. The electrolyte overflows from the water outlet trough 72 to the cylinder hole 81. After 30 minutes, the cylinder hole is filled, and electroplating continues for 15 minutes; 6. Post-treatment: After electroplating, rinse the cylinder hole with deionized water (pressure 0.2MPa, 5min), dry at 80℃ for 30min, and then put it into the sintering furnace (heating rate 10℃ / min, 800℃ insulation for 2h). After cooling in the furnace, test the coating performance.

[0017] Performance test: coating thickness 0.8-1.2mm, bonding strength 35MPa, hardness HV1800 (Vickers hardness tester), friction and wear test (load 500N, speed 500rpm) wear rate 0.02mg / h (traditional chrome plating layer is 0.04mg / h), meeting the wear resistance requirements of engine cylinder bores.

[0018] Working principle of engine cylinder block cylinder bore ceramic coating production line The production line of this invention achieves efficient and uniform ceramic coating on the inner wall of the engine cylinder bore through the coordinated operation of three core mechanisms: precise electrolyte circulation, precise cylinder positioning, and electric field-driven ceramic deposition. The following details its working principle from the perspective of the coordinated operation of each module: 1. Driving mechanism of electrolyte circulation system The electrolyte circulation system is the "blood" of the entire production line. Its core function is to provide a continuous and stable electrolyte containing ceramic powder for the electroplating process and maintain the uniformity of the electrolyte composition and temperature. The specific process is as follows: Electrolyte supply: The prepared electrolyte (containing ceramic powder, complexing agent, conductive salt, etc.) in the water tank 1 is pressurized by the water pump 2 and transported to the matrix-arranged positioning fixtures 7 through the outlet pipe 3.

[0019] Electrolyte distribution: The water outlet pipe 3 is connected to the water outlet groove 72 of each positioning fixture 7 in a one-to-one correspondence. The electrolyte overflows through the notch of the water outlet groove 72 and flows into the cylinder bore 81 of the engine cylinder block 8. Because the water outlet groove 72 is aligned with the center axis of the cylinder bore 81 (the anode rod 73 is located on the center axis), the electrolyte spreads evenly along the inner wall of the cylinder bore until it fills the entire cylinder bore.

[0020] Recycling and purification: The electroplated electrolyte flows out of the sump 5 at the bottom of the housing 4 and returns to the water tank 1 through a pipe. A filter (such as a filter) in the sump 5 intercepts impurities such as metal debris and undeposited ceramic particles in the electrolyte, preventing them from re-entering the cylinder bore and affecting the quality of the coating.

[0021] Temperature control: The heating device and temperature sensor in the water tank 1 adjust the electrolyte temperature (40-60°C) in real time to ensure that the electrolyte viscosity and ion activity are in the optimal state, thereby improving the migration efficiency of ceramic particles driven by the electric field.

[0022] 2. Precision guiding mechanism of cylinder positioning fixture The positioning fixture 7 is the core component for achieving precise positioning of the cylinder body 8. Its design ensures that the cylinder hole 81 is coaxially aligned with the anode rod 73, thereby ensuring uniform coating. The specific principles are as follows: Mechanical limit: The lower end surface of the engine cylinder block 8 is tightly fitted with the upper end surface of the base 71 of the positioning fixture 7, and the annular limit step 82 on the end surface of the cylinder hole 81 is inserted into the annular positioning ring 75 of the notch of the water outlet groove 72 (the gap is only 0.1-0.2mm), thereby realizing the radial positioning of the cylinder block (to prevent deviation).

[0023] Axial alignment: The anode rod 73 is inserted into the bottom of the water outlet trough 72, and its length is slightly greater than the depth of the cylinder hole 81 (to ensure full insertion). The center axis of the anode rod 73 coincides with the center axis of the water outlet trough 72, and the water outlet trough 72 is aligned with the center axis of the cylinder hole 81, so the anode rod 73 and the cylinder hole 81 form a "coaxial sleeve" structure.

[0024] Electrolyte guidance: After the electrolyte overflows from the water outlet trough 72, it flows evenly into the bottom of the cylinder hole along the annular gap between the inner wall of the cylinder hole 81 and the outer wall of the anode rod 73, avoiding uneven coating thickness caused by local excessive flow rate.

[0025] 3. Electric field drive and ceramic deposition mechanism of electroplating process The electroplating stage is the core step in the formation of the ceramic coating. Its principle is based on electrophoretic deposition technology, which uses electric field force to drive the directional migration and deposition of ceramic particles on the inner wall of the cylinder bore. The specific process is as follows: Electrode setup: Anode rod 73 is connected to the positive power supply (anode), and engine block 8 is connected to the negative power supply (cathode). Anode rod 73 is typically made of a titanium-based coating (such as ruthenium-titanium coating), which has good corrosion resistance and catalytic activity. Cylinder block 8 acts as the cathode, with a negative surface charge.

[0026] Electrophoretic migration of ceramic particles: Ceramic powder (such as aluminum oxide) dispersed in the electrolyte becomes positively charged due to adsorption of ions (such as citrate) in the electrolyte, and migrates toward the cathode (cylinder 8) under the action of the electric field force.

[0027] Deposition and film formation: After reaching the inner wall of cylinder bore 81 (the cathode surface), the positively charged ceramic particles lose their charge and combine with activated sites on the cylinder surface (which, after plasma treatment, have polar groups such as hydroxyl and carboxyl groups), gradually depositing to form a ceramic coating. As the electroplating time increases (30-60 minutes), the coating thickness gradually increases (ultimately 0.8-1.2 mm).

[0028] Electric field uniformity is ensured: the distance (5-10 mm) between the anode rod 73 and the inner wall of the cylinder bore of the cylinder body 8 is strictly controlled by the rigid structure of the positioning fixture 7 to ensure that the electric field strength at each point on the inner wall of the cylinder bore is consistent, avoiding local plating being too thick or too thin.

[0029] 4. Performance Enhancement Mechanism of Post-Processing Process After electroplating, the coating needs to be cleaned, dried and sintered to improve its density, hardness and bonding strength: Cleaning: Rinse the cylinder bore with deionized water to remove residual electrolyte (including undeposited ceramic particles and electrolyte) on the surface to prevent residual substances from corroding the coating or affecting subsequent sintering.

[0030] Drying: Dry at 80-100℃ for 30 minutes to remove moisture from the coating and prevent pores from forming due to moisture evaporation during sintering.

[0031] Sintering: Sintering at a high temperature of 800-1000℃ for 2h. The ceramic particles form a metallurgical bond with the cylinder surface through diffusion reaction (such as alumina partially reacts with Fe and C elements in cast iron to form compounds such as iron-aluminum spinel). At the same time, the internal stress of the coating is eliminated, and the hardness (HV1500-2000) and wear resistance are improved.

[0032] Utilizing this technical solution, the production line achieves batch processing of cylinder blocks through a matrix-arranged positioning fixture. The coordination of positioning rings and stop steps ensures precise positioning of the cylinder blocks. The coaxial design of the water outlet trough and anode rod ensures uniform electrolyte delivery to the cylinder bore, avoiding blind spots during electroplating. The electrolyte circulation system, through sump filtration and temperature control, ensures stable electrolyte composition and enhances plating uniformity. Combined with an optimized electroplating process, the ceramic coating achieves a bond strength of ≥30MPa to the cylinder bore substrate and a hardness of HV1500-2000. This reduces wear by over 50% compared to traditional chrome plating, significantly improving the wear resistance and service life of the engine cylinder block.

Claims

1. A composite coating surface treatment production line, characterized in that: The invention comprises an electrolyte circulation system, a box (4) and a positioning fixture (7) for positioning an engine cylinder; the positioning fixture (7) is arranged in a matrix and installed at the bottom of the box (4), and the engine cylinder (8) is placed on the positioning fixture (7); the bottom of the box (4) is fixed on a base (6); the electrolyte circulation system comprises a water tank (1), a water pump (2), a water outlet pipe (3) and a water collecting tank (5) at the bottom of the box (4); the water collecting tank (5) is communicated with the bottom of the box (4) and is connected to the water tank (1) through a pipe; the water tank (1) is connected to the water pump (2) through a water pipe, the water pump (2) is connected to the water outlet pipe (3) through a water pipe, and the water outlet pipe (3) is connected to the positioning fixture (7) in a one-to-one correspondence; the positioning fixture (7) comprises a base (71), and a base (71) is provided with a There is a water outlet groove (72) corresponding to the cylinder hole (81) of the engine body, and the anode rod (73) is inserted into the water outlet groove (72); the lower end surface of the engine cylinder body (8) is tightly fitted with the upper end surface of the base (71), and an annular limiting step (82) extends from the end surface of the cylinder hole (81) of the engine body. An annular positioning ring (75) is provided on the notch of the water outlet groove (72), and the limiting step (82) is inserted into the positioning ring (75) to realize the positioning of the cylinder body (8); the anode rod (73) is located at the center axis position of the cylinder hole (81), and the water outlet groove (72) is connected to the water outlet pipe (3) through a water pipe. The electrolyte enters the water outlet groove (72) through the water outlet pipe (3) and overflows into the cylinder hole (81) until the cylinder hole (81) is filled. After the anode rod (73) and the cylinder body (8) are energized by the electrolyte, the inner wall of the cylinder hole (81) is electroplated.

2. The composite coating surface treatment production line according to claim 1, characterized in that: The base (71) of the positioning fixture (7) is rectangular, and the number of the water outlet grooves (72) is consistent with the number of the cylinder holes (81) of the cylinder body; the length of the anode rod is slightly greater than the depth of the cylinder hole (81) or is the same.

3. The composite coating surface treatment production line according to claim 1, characterized in that: A filtering device is provided in the water collecting tank (5) for filtering impurities in the electrolyte; a heating device and a temperature sensor are provided in the water tank (1).

4. An electroplating process based on the composite coating surface treatment production line according to any one of claims 1 to 3, characterized in that: The following steps are involved:

1. Ceramic powder preparation: Alumina, silicon carbide or silicon nitride ceramic powder is selected and prepared through ball milling and classification process to obtain ceramic powder with a particle size of 1μm-5μm and a purity of ≥99%; 2. Surface treatment of the metal substrate: sandblasting and plasma activation treatment are performed on the inner wall of the cylinder bore (81) of the engine cylinder block to increase the surface energy to ≥50 mN / m; 3. Preparation of electrolyte: Using deionized water as solvent, add 5-15g / L of ceramic powder, 10-20g / L of complexing agent, 50-60g / L of conductive salt and pH regulator to adjust the pH to 8-10, stir and filter to obtain the electrolyte; 4. Determination of electroplating process parameters: Through experiments, the current density is determined to be 2 A / dm²-5A / dm², the electrolysis time is determined to be 30 min-60 min, the temperature is determined to be 40°C-60°C, and the distance between the anode rod (73) and the cylinder (8) is determined to be 5 mm-8 mm; 5. Electroplating ceramic coating: Fix the surface treated cylinder body (8) to the positioning fixture (7), insert the anode rod (73) into the center axis position of the cylinder hole (81), circulate the electrolyte to fill the cylinder hole (81) and then turn on the power, connect the anode rod (73) to the positive pole of the power supply, and connect the cylinder body (8) to the negative pole, and perform electroplating according to the set parameters; 6. Post-treatment of coating: After electroplating, clean, dry at 80-100℃ for 30 minutes and sinter at 800℃-1000℃ for 2 hours to improve the density and hardness of the coating.

5. The electroplating process of the production line according to claim 4, characterized in that: The pressure of the sandblasting cleaning in step (2) is 0.3 MPa-0.5 MPa, the power of the plasma activation treatment is 3 kW-6 kW, and the argon flow rate is 15 L / min-25 L / min.

6. The electroplating process of the production line according to claim 4, characterized in that: In step (3), the complexing agent is sodium citrate, and the conductive salt is sodium sulfate.

7. The electroplating process of the production line according to claim 4, characterized in that: In step (5), the current density is 3 A / dm², the electrolysis time is 45 min, the temperature is 50° C., and the distance between the anode rod (73) and the cylinder (8) is 8 mm.

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