Sawtooth PVD (Physical Vapor Deposition) treatment method

Abstract

The invention relates to the technical field of surface treatment, and discloses a PVD (Physical Vapor Deposition) treatment method for sawteeth. Comprising the following steps: carrying out alkaline electrolytic polishing treatment to obtain a flat surface, carrying out phosphating treatment after pickling neutralization to form a chemical conversion film, depositing a hard functional layer through PVD plating, carrying out surface cleaning and pretreatment to obtain a clean substrate, coating a heat-resistant base coat with a polymer to form a heat-resistant hard bottom layer, coating a wear-resistant surface coat with a polymer to form a wear-resistant protective layer, and curing to form a film to form an integrated structure. Through the synergistic effect of the five-layer composite protection structure, the sawtooth groove protection blind area is eliminated, the coating quality consistency is remarkably improved, the corrosion resistance time exceeds 2000 hours, the high-temperature softening limit is broken through, 100-180 DEG C stable work is achieved, the wear resistance is improved by one order of magnitude, meanwhile, functionality and durability are considered, and the service life is prolonged. And an effective technical solution is provided for long-term reliable application of the sawtooth workpiece under harsh working conditions.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a serrated PVD treatment method. Background Technology

[0002] Serrated workpieces have a complex surface morphology with sharp tooth tips, inclined tooth surfaces and deep concave tooth grooves, and are widely used in high-temperature friction and wear conditions such as automotive gearbox gears, high-temperature pump bushings, and textile machinery guide rails.

[0003] Existing surface protection technologies have significant limitations: a single PVD coating is insufficiently covered in the deep grooves of the serrated surface, creating a protective blind spot that leads to preferential corrosion; the uneven surface roughness (Ra 1-3μm) of the serrated substrate causes defects such as droplets and pinholes in the PVD coating, resulting in uneven thickness distribution; the columnar grain boundaries and microcracks of hard PVD ceramic coatings become channels for corrosive media penetration, lacking chemical passivation and self-healing capabilities; conventional polymer sealing layers soften and fail in medium- and high-temperature environments (100-180℃), have low glass transition temperatures (60-120℃), and their hardness drops from 2H to below B; single polymers wear rapidly under friction and wear conditions, with a wear rate of approximately 10%. -4 mm³ / N·m, it will be worn through after hundreds to thousands of friction cycles. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a serrated PVD processing method, comprising the following steps: Step 1: Alkaline electrolytic polishing treatment: The serrated workpiece is placed as the anode in a 15-25% sodium hydroxide aqueous solution, with 0.5-2% polyethylene glycol added as an organic additive, and an anodic current density of 5-15 A / dm³ is applied. 2 The electrolysis voltage is 8-20V, and the processing time is 5-15 minutes. Through electrochemical dissolution, the surface roughness of the saw teeth is reduced from Ra 1-3μm to Ra 0.2-0.5μm, resulting in a smooth surface. Step 2: Phosphating treatment: After pickling and neutralization, the saw teeth are immersed in a phosphating solution for chemical phosphating treatment. The phosphating solution uses a zinc-based or manganese-based phosphating system, the treatment temperature is 65-95℃, and the time is 10-25 minutes, forming a uniform phosphating film of 5-15μm thickness on the saw teeth surface. Step 3: PVD Coating: Titanium nitride, chromium nitride, or titanium aluminum nitride hard coatings are deposited on phosphating substrates using magnetron sputtering physical vapor deposition technology, with a coating thickness of 2-5 μm. Step 4: Surface pretreatment: The PVD coating surface is cleaned and slightly roughened to increase the surface roughness from 0.1-0.3 μm to 0.3-0.8 μm; Step 5: Apply heat-resistant primer: Apply a heat-resistant polymer base coat with a glass transition temperature of 150-180℃ and a thickness of 5-10μm; Step 6: Applying the wear-resistant surface coating: A flexible and wear-resistant polymer topcoat with a thickness of 10-20 μm is applied to the surface of the base coating. Step 7: Curing into a film: Curing at 80-120℃ for 30-60 minutes forms a five-layer composite protective structure.

[0005] Preferably, in the alkaline electrolytic polishing process, the oxygen bubbles generated on the anode surface during electrolysis mechanically stir and clean the serrated grooves, removing contaminants and oxide layers deep within the grooves.

[0006] Preferably, in the phosphating treatment, the zinc-based phosphating system contains 15-25 g / L zinc dihydrogen phosphate, 15-25 g / L phosphoric acid, and 5-15 g / L zinc nitrate, and the treatment temperature is 65-85℃; the manganese-based phosphating system contains 20-30 g / L manganese dihydrogen phosphate, 20-30 g / L phosphoric acid, and 10-20 g / L manganese nitrate, and the treatment temperature is 85-95℃.

[0007] Preferably, the PVD coating process parameters are: vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, argon partial pressure 0.2-0.5 Pa, nitrogen partial pressure 0.1-0.3 Pa, substrate temperature 350-450℃, sputtering power density 3-8 W / cm², deposition rate 0.5-2.0 μm / h.

[0008] Preferably, the surface pretreatment involves cleaning with an alkaline degreasing cleaner at 5-10% by mass at 60-80°C for 3-5 minutes, followed by light polishing with alumina polishing paste with a particle size of 1-5μm or 600-1000 grit sandpaper.

[0009] Preferably, the heat-resistant primer coating is made of bisphenol A type epoxy resin combined with an aliphatic amine curing agent, with a mixing ratio of epoxy resin:curing agent = 100: 25-35, or a polyimide precursor solution with a solid content of 20-35%.

[0010] Preferably, the wear-resistant surface coating uses aliphatic polyurethane combined with a polyol curing agent, with a mixing ratio of polyurethane prepolymer: curing agent = 100: 15-25, or uses fluorine-modified acrylic resin with a fluorine content of 8-15wt%.

[0011] Preferably, the heat-resistant base coating and the wear-resistant top coating form interfacial bonds at the interface through molecular chain segment interpenetration and functional group chemical reaction, thus avoiding interlayer delamination.

[0012] Preferably, the five-layer composite protective structure consists of an electrolytic polishing leveling layer, a phosphating conversion film, a PVD hard layer, a heat-resistant base coating, and a wear-resistant top coating, with each layer tightly bonded together through chemical bonding, mechanical interlocking, and physical filling.

[0013] Preferably, the composite protective structure has a total thickness of 15-30μm, a light transmittance of ≥85%, an adhesion level of 1, shows virtually no corrosion after 1200 hours of neutral salt spray testing, and exhibits no cracking or peeling during high and low temperature cycling tests from -40℃ to +180℃.

[0014] The beneficial effects of this invention are as follows: Uniform protection across the entire surface: Phosphating pretreatment forms a uniform chemical conversion film in the deep grooves of the serrated surface. Combined with the bubble cleaning effect of electropolishing and the flow coverage of the double-layer polymer, it ensures that all areas, including the bottom of the groove, receive multi-layer protection, completely eliminating the protection blind spots of traditional PVD coatings in the grooves.

[0015] Significantly improved coating quality: Electrolytic polishing reduces surface roughness by 80-90%, providing a smooth and uniform substrate for PVD coating. The occurrence rate of defects such as droplets and pinholes is reduced by more than 50%, and the uniformity of coating thickness distribution and quality consistency in various parts of the serrations are significantly improved.

[0016] Multi-layer synergistic protection: The five-layer composite structure forms multiple barriers from chemical stability and physical isolation to final sealing. The comprehensive protection effect produced by the synergistic effect of each layer far exceeds that of a single layer or simple superposition, achieving all-round performance improvement from the substrate to the surface.

[0017] Overcoming the limitations of high-temperature softening: The dual-layer polymer system achieves synergistic optimization of heat resistance and wear resistance through functional stratification. The heat-resistant base coating remains stable at high temperatures of 150-180℃, enabling sawtooth workpieces to work stably for a long time under conditions of 100-180℃ and frequent friction.

[0018] Synergistic effect of polymer sealing and hard coating: The dual-layer polymer sealing system completely seals the defect channels of the PVD hard coating, while the transparent polymer layer provides protection while maintaining the metallic luster of the underlying coating, achieving an organic combination of protection and display.

[0019] Mature and reliable technology: The technologies used are all mature commercial processes with strong process controllability and good repeatability, making them suitable for mass industrial applications and providing an effective technical solution for the long-term reliable application of sawtooth workpieces under harsh working conditions. Attached Figure Description

[0020] Figure 1These are the corrosion resistance curves of different protection systems of this invention; Figure 2 This invention compares the friction coefficients under high-temperature conditions. Figure 3 This is a three-dimensional visualization diagram of the thickness distribution of the protective layer on the sawtooth surface of the present invention; Figure 4 This is a microscopic characterization image of a portion of the serrations in this invention. Detailed Implementation

[0021] The subject matter described herein will now be discussed with reference to exemplary embodiments. It should be understood that these embodiments are discussed only to enable those skilled in the art to better understand and implement the subject matter described herein, and changes may be made to the function and arrangement of the elements discussed without departing from the scope of this specification. Various processes or components may be omitted, substituted, or added as needed in the examples. Furthermore, some features described in the examples may be combined in other examples.

[0022] Example 1: This example proposes a serrated PVD processing method, including the following steps: Step 1: Alkaline electrolytic polishing treatment: The serrated workpiece was placed as the anode in a 20% sodium hydroxide aqueous solution, and 1.25% polyethylene glycol was added as an organic additive. An anodic current density of 10 A / dm³ was applied. 2 The electrolysis voltage is 14V and the processing time is 10 minutes. Through electrochemical dissolution, the surface roughness of the saw teeth is reduced from Ra 2μm to Ra 0.3μm, resulting in a smooth surface. In alkaline electrolytic polishing, oxygen bubbles generated on the anode surface during electrolysis mechanically agitate and clean the serrated grooves, removing contaminants and oxide layers deep within the grooves.

[0023] Step 2: Phosphating treatment: After pickling and neutralization, the saw teeth are immersed in a phosphating solution for chemical phosphating treatment. The phosphating solution uses a zinc-based phosphating system, the treatment temperature is 80℃, and the time is 17.5 minutes, forming a uniform phosphating film with a thickness of 10μm on the saw teeth surface. In the phosphating process, the zinc-based phosphating system contains 20 g / L zinc dihydrogen phosphate, 20 g / L phosphoric acid, and 10 g / L zinc nitrate, and the treatment temperature is 75℃.

[0024] Step 3: PVD Coating: Titanium nitride hard coating with a thickness of 3 μm was deposited on a phosphating substrate using magnetron sputtering physical vapor deposition technology. Step 4: Surface pretreatment: The PVD coating surface was cleaned and slightly roughened to increase the surface roughness from 0.2 μm to 0.5 μm; The process parameters for PVD coating are: vacuum degree ≤ 5 × 10⁻⁶ -3 Pa, argon partial pressure 0.35 Pa, nitrogen partial pressure 0.2 Pa, substrate temperature 400℃, sputtering power density 5 W / cm², deposition rate 1.25 μm / h; The surface pretreatment involved cleaning with an 8% (w / w) alkaline degreasing cleaner at 70°C for 4 minutes, followed by light polishing with an alumina polishing paste with a particle size of 3μm.

[0025] Step 5: Apply heat-resistant primer: A heat-resistant polymer base coating with a glass transition temperature of 165℃ and a thickness of 8μm is applied. The heat-resistant primer layer uses bisphenol A type epoxy resin combined with an aliphatic amine curing agent, with a mixing ratio of epoxy resin: curing agent = 100:30.

[0026] Step 6: Applying the wear-resistant surface coating: A flexible and wear-resistant polymer topcoat with a thickness of 15 μm is applied to the surface of the base coating. The wear-resistant surface coating uses aliphatic polyurethane combined with a polyol curing agent, with a mixing ratio of polyurethane prepolymer: curing agent = 100:20; The heat-resistant base coating and the wear-resistant top coating form interfacial bonds at the interface through molecular chain segment interpenetration and functional group chemical reactions, thus avoiding interlayer delamination.

[0027] Step 7: Curing into a film: Curing at 100℃ for 45 minutes forms a five-layer composite protective structure; The five-layer composite protective structure consists of an electrolytic polishing and smoothing layer, a phosphating conversion film, a PVD hard layer, a heat-resistant base layer, and a wear-resistant top coating. Each layer is tightly bonded together through chemical bonding, mechanical interlocking, and physical filling. The composite protective structure has a total thickness of 22μm, a light transmittance of ≥85%, an adhesion level of 1, and shows virtually no corrosion after 1200 hours of neutral salt spray testing. It also shows no cracking or peeling after a high and low temperature cycling test at 20℃.

[0028] Example 2 differs from Example 1 in that: Step 1: Place the serrated workpiece as the anode in a 15% sodium hydroxide aqueous solution, add 0.5% polyethylene glycol as an organic additive, and apply an anodic current density of 5 A / dm³. 2 The electrolysis voltage is 8V and the processing time is 5 minutes. Through electrochemical dissolution, the surface roughness of the saw teeth is reduced from Ra 1μm to Ra 0.2μm, resulting in a smooth surface.

[0029] Step 2: The phosphating solution uses a zinc-based phosphating system, with a treatment temperature of 65℃ and a time of 10 minutes, forming a uniform phosphating film with a thickness of 5μm on the serrated surface; In the phosphating process, the zinc-based phosphating system contains 25 g / L zinc dihydrogen phosphate, 25 g / L phosphoric acid, and 15 g / L zinc nitrate, and the treatment temperature is 85℃.

[0030] Step 3: Deposit a chromium nitride hard coating on a phosphating substrate using magnetron sputtering physical vapor deposition technology, with a coating thickness of 2 μm; Step 4: Clean and slightly roughen the PVD coating surface, increasing the surface roughness from 0.1 μm to 0.3 μm; The process parameters for PVD coating are: vacuum degree ≤ 5 × 10⁻⁶ -3 Pa, argon partial pressure 0.2 Pa, nitrogen partial pressure 0.1 Pa, substrate temperature 350℃, sputtering power density 3 W / cm², deposition rate 0.5 μm / h; The surface pretreatment involved cleaning with a 5% (w / w) alkaline degreasing cleaner at 60°C for 3 minutes, followed by light polishing with alumina polishing paste with a particle size of 1 μm.

[0031] Step 5: Apply a heat-resistant polymer primer with a glass transition temperature of 150℃, with a thickness of 5μm; The mixing ratio is epoxy resin: curing agent = 100: 25.

[0032] Step 6: Apply a flexible and wear-resistant polymer topcoat to the base coating surface, with a thickness of 10 μm; The wear-resistant surface coating uses aliphatic polyurethane combined with a polyol curing agent, with a mixing ratio of polyurethane prepolymer: curing agent = 100:15.

[0033] Step 7: Curing at 800℃ for 30 minutes to form a five-layer composite protective structure; The composite protective structure has a total thickness of 15μm, a light transmittance of ≥85%, an adhesion level of 1, and shows virtually no corrosion after 1200 hours of neutral salt spray testing. However, it cracks and peels off at -40℃ during high and low temperature cycling tests.

[0034] Example 3 differs from Example 1 in that: Step 1: Place the serrated workpiece as the anode in a 25% sodium hydroxide aqueous solution, add 2% polyethylene glycol as an organic additive, and apply an anodic current density of 15 A / dm. 2 The electrolysis voltage is 20V and the processing time is 15 minutes. Through electrochemical dissolution, the surface roughness of the saw teeth is reduced from Ra 3μm to Ra 0.5μm, resulting in a smooth surface.

[0035] Step 2: The phosphating solution is zinc-based, the treatment temperature is 95℃, and the time is 25 minutes, forming a uniform phosphating film with a thickness of 15μm on the serrated surface; In the phosphating process, the zinc-based phosphating system contains 15 g / L zinc dihydrogen phosphate, 15 g / L phosphoric acid, and 5 g / L zinc nitrate, and the treatment temperature is 65℃.

[0036] Step 3: Deposit a titanium aluminum nitride hard coating on a phosphating substrate using magnetron sputtering physical vapor deposition technology, with a coating thickness of 5 μm; Step 4: Clean and slightly roughen the PVD coating surface to increase the surface roughness from 0.3 μm to 0.8 μm; The process parameters for PVD coating are: vacuum degree ≤ 5 × 10⁻⁶ -3 Pa, argon partial pressure 0.5 Pa, nitrogen partial pressure 0.3 Pa, substrate temperature 450℃, sputtering power density 8 W / cm², deposition rate 2.0 μm / h; The surface pretreatment involved cleaning with a 10% (w / w) alkaline degreasing cleaner at 80°C for 5 minutes, followed by light polishing with alumina polishing paste with a particle size of 5μm.

[0037] Step 5: Apply a heat-resistant polymer primer with a glass transition temperature of 180℃, 10μm thick; The mixing ratio is epoxy resin: curing agent = 100:35.

[0038] Step 6: Apply a flexible and wear-resistant polymer topcoat to the base coating surface, with a thickness of 20 μm; The wear-resistant surface coating uses aliphatic polyurethane combined with a polyol curing agent, with a mixing ratio of polyurethane prepolymer: curing agent = 100: 25.

[0039] Step 7: Curing at 120℃ for 60 minutes to form a five-layer composite protective structure; The composite protective structure has a total thickness of 30μm, a light transmittance of ≥85%, an adhesion level of 1, and shows virtually no corrosion after 1200 hours of neutral salt spray testing. It also shows no cracking or peeling after high and low temperature cycling testing at +180℃.

[0040] Example 4 differs from Example 1 in that: Step 2: The phosphating solution uses a zinc-based system; in the phosphating treatment, the zinc-based phosphating system contains 25 g / L zinc dihydrogen phosphate, 25 g / L phosphoric acid, and 15 g / L zinc nitrate, and the treatment temperature is 85℃.

[0041] The surface was pretreated by lightly sanding with 800-grit sandpaper.

[0042] The heat-resistant primer coating uses a polyimide precursor solution with a solid content of 28%.

[0043] The wear-resistant coating is made of fluorine-modified acrylic resin with a fluorine content of 12wt%.

[0044] Example 5 differs from Example 1 in that: Step 2: The phosphating solution uses a manganese-based phosphating system; the manganese-based phosphating system contains 20 g / L manganese dihydrogen phosphate, 20 g / L phosphoric acid, and 10 g / L manganese nitrate, and the treatment temperature is 85℃.

[0045] The surface was lightly sanded using 600-grit sandpaper for pretreatment.

[0046] The heat-resistant primer coating uses a polyimide precursor solution with a solid content of 20%.

[0047] The wear-resistant coating is made of fluorine-modified acrylic resin with a fluorine content of 8wt%.

[0048] Example 6 differs from Example 1 in that: Step 2: The phosphating solution uses a manganese-based phosphating system; the manganese-based phosphating system contains 30 g / L manganese dihydrogen phosphate, 30 g / L phosphoric acid, and 20 g / L manganese nitrate, and the treatment temperature is 95℃.

[0049] The surface was pretreated by lightly sanding with 1000-grit sandpaper.

[0050] The heat-resistant primer coating uses a polyimide precursor solution with a solid content of 35%.

[0051] The wear-resistant coating is made of fluorine-modified acrylic resin with a fluorine content of 15wt%.

[0052] Example 7: This example proposes a serrated PVD processing method, including the following steps: Step 1: Alkaline electrolytic polishing treatment The serrated workpiece is placed as the anode in an alkaline electrolyte prepared with a 15-25% (w / w) sodium hydroxide aqueous solution and 0.5-2% (w / w) of polyethylene glycol (PEG-400) added as an organic additive to improve surface smoothness. An anodic current density of 5-15 A / dm², an electrolysis voltage of 8-20V, and a treatment time of 5-15 minutes are applied to smooth the serrated surface through electrochemical dissolution.

[0053] During the electrochemical dissolution process, the raised portions of the serrated surface preferentially undergo oxidation and dissolution of metal atoms due to the higher current density, while the recessed portions dissolve more slowly due to the lower current density. This selective dissolution achieves surface smoothing. Oxygen bubbles generated on the anode surface during electrolysis mechanically agitate and clean the serrated grooves, removing contaminants and oxide layers deep within the grooves. The generation and detachment of oxygen bubbles continuously clean the inner walls of the grooves, achieving a cleaning effect that traditional mechanical or chemical polishing cannot achieve.

[0054] Results: The surface roughness Ra of the sawtooth workpiece was reduced to a smooth surface of 0.2-0.5μm, which is 80-90% lower than the initial surface roughness Ra of 1-3μm. The surface has a metallic luster and high chemical activity, providing a clean nucleation substrate for subsequent phosphating treatment.

[0055] Step 2: Pickling, neutralization, and phosphating After alkaline electropolishing, first rinse thoroughly with deionized water until the pH is close to neutral (pH 6-8). Then, clean with a 5-10% (w / w) dilute nitric acid solution for 30-60 seconds to remove residual alkaline substances and activate the surface. Safety Precautions: Ensure that all alkaline substances on the workpiece surface are completely rinsed off before contact with acidic solutions to avoid violent neutralization reactions and localized overheating caused by direct contact between strong acids and strong bases. After cleaning, rinse thoroughly with deionized water until the pH is neutral. Waste Liquid Treatment: Waste liquid containing sodium hydroxide and waste liquid containing nitric acid should be collected separately and neutralized to pH 6-9 before discharge. The serrated workpiece is immersed in a phosphating solution for chemical phosphating treatment. The phosphating solution uses a zinc-based phosphating system (containing 15-25 g / L zinc dihydrogen phosphate, 15-25 g / L phosphoric acid, and 5-15 g / L zinc nitrate) at a temperature of 65-85℃ for 10-20 minutes, or a manganese-based phosphating system (containing 20-30 g / L manganese dihydrogen phosphate, 20-30 g / L phosphoric acid, and 10-20 g / L manganese nitrate) at a temperature of 85-95℃ for 15-25 minutes.

[0056] The smooth, highly active surface obtained by alkaline electropolishing makes phosphating nucleation more uniform and dense. The smooth surface eliminates microscopic unevenness, allowing phosphating crystals to grow uniformly across the entire surface and avoiding uneven phosphating film thickness caused by rough surfaces.

[0057] Results: A uniform phosphating film of 5-15 μm thickness was formed on the serrated surface. The phosphating film has fine and dense grains and low porosity, achieving good coverage deep within the serrated grooves. It serves as a corrosion barrier for the chemical conversion layer and an adhesion substrate for the PVD coating. Post-treatment: After phosphating, the surface is rinsed with deionized water to remove the phosphating solution, and then dried at 100-120℃ for 10-15 minutes. Waste liquid recovery: After sedimentation and separation, the phosphating waste liquid can be recovered as a raw material for phosphate fertilizer. The treated wastewater is neutralized and discharged after meeting standards.

[0058] Step 3: PVD Coating After phosphating, the serrated workpiece is rinsed with deionized water and dried at 120℃ before entering the PVD coating equipment. A hard functional coating is deposited using magnetron sputtering physical vapor deposition technology. The coating material is titanium nitride (TiN), chromium nitride (CrN), or titanium aluminum nitride (TiAlN), and the process parameters are: vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, argon partial pressure 0.2-0.5 Pa, nitrogen partial pressure 0.1-0.3 Pa, substrate temperature 350-450℃, sputtering power density 3-8 W / cm², deposition rate 0.5-2.0 μm / h, coating thickness controlled at 2-5 μm.

[0059] Substrate optimization effect: PVD coating is performed on a high-quality substrate obtained by alkaline electrolytic polishing and phosphating. The smooth phosphating substrate improves the deposition quality of PVD coating and reduces defects such as droplets and pinholes.

[0060] Results: A hard PVD coating with a thickness of 2-5 μm and a hardness of HV 2000-3000 was obtained on the serrated surface (hardness was tested according to GB / T4956, and thickness was tested according to GB / T 13452.2). The coating thickness distribution was uniform, and the thickness difference between the serrated tip and the groove was reduced from 40-60% in the traditional process to 15-25%. The internal stress was reduced from 2-4 GPa in the traditional process to 0.5-1.5 GPa (measured by a thin film stress tester), providing excellent wear resistance and hard protection for the serrated workpiece.

[0061] Step 4: Surface Cleaning and Pretreatment After PVD coating, the serrated workpiece is cleaned to remove trace amounts of oil and particulate contaminants generated during the coating process. Then, a surface activation pretreatment is performed to provide a good adhesion substrate for the subsequent polymer coating.

[0062] Processing Procedure: Clean the PVD coating surface for 3-5 minutes at 60-80℃ with a 5-10% (w / w) alkaline degreasing cleaner (such as triethanolamine or sodium carbonate solution) to remove grease and organic contaminants. Then rinse thoroughly with deionized water until the pH is neutral. Next, perform a slight surface roughening treatment by lightly hand-polishing the PVD coating surface for 1-2 minutes with an alumina polishing paste or alumina slurry (water-based suspension with 20-30% Al2O3 content) with 1-5μm particle size, or by lightly polishing with 600-1000 grit sandpaper. Increase the surface roughness Ra from 0.1-0.3μm to 0.3-0.8μm to enhance the mechanical adhesion of the polymer coating. After treatment, rinse with deionized water and dry at 100℃ for 5-10 minutes.

[0063] Results: The PVD coating achieved a clean surface with moderate roughness, with oil content below 10 mg / m² (tested according to GB / T 13288), particulate contaminant density below 5 particles / cm² (microscopic counting method), and surface roughness Ra increasing from 0.1-0.3 μm before treatment to 0.3-0.8 μm (tested according to GB / T 1031). The contact angle decreased from 80-90° before treatment to 40-60°, indicating improved surface energy, providing excellent wettability and mechanical interlocking substrate for subsequent polymer coatings.

[0064] Step 5: Applying a heat-resistant primer polymer coating After cleaning and pretreatment, a first polymer primer layer is applied to the PVD coating surface using brushing, spraying, or dipping methods. The polymer selected is a heat-resistant material with a high glass transition temperature. Preferably, bisphenol A epoxy resin (epoxy value 0.48-0.54 eq / 100g, glass transition temperature Tg 150-180℃, viscosity 8000-12000 mPa·s at 25℃) is used in combination with an aliphatic amine curing agent (amine value 350-400 mgKOH / g) at a mixing ratio of epoxy resin:curing agent = 100:25-35 (mass ratio). Alternatively, a polyimide precursor solution (N-methylpyrrolidone solution with a solid content of 20-35%, viscosity 3000-8000 mPa·s) can be used. The coating thickness is controlled at 15-25 μm for wet film and 5-10 μm for dry film.

[0065] A heat-resistant polymer with a highly cross-linked rigid molecular structure is used, with a glass transition temperature of 150-180℃, far exceeding the 60-120℃ of conventional polymers, maintaining its glassy state without softening at high temperatures. After coating, a pre-curing treatment at 120-150℃ is performed, causing the polymer to form a partially cross-linked gel structure, ensuring the heat-resistant and rigid properties of the base coating, while also providing chemical bonding sites for the subsequent top coating.

[0066] Results: A 5-10 μm thick heat-resistant hard base coat (thickness tested according to GB / T13452.2) was formed on the cleaned and pretreated PVD coating surface. This layer has a pencil hardness of 4H-6H (tested according to GB / T 6739), a glass transition temperature of 150-180℃ (tested according to DSC), a thermal decomposition temperature greater than 300℃ (tested according to TGA), and a hardness retention rate of more than 90% after continuous exposure at 180℃ for 500 h. The adhesion reaches grade 1 (tested according to GB / T 9286). It serves as a heat-resistant barrier and a hard support substrate, providing an interface for the binding of active functional groups for the subsequent topcoat.

[0067] Step Six: Applying abrasion-resistant polymer coating A second polymer topcoat is applied to the heat-resistant base coating using brushing, spraying, or dipping methods. The polymer should be a flexible and wear-resistant material. Preferably, an aliphatic polyurethane (NCO content 15-20%, viscosity at 25℃ 2000-6000 mPa·s, Shore hardness A 85-95) is used in combination with a polyol curing agent, with a mixing ratio of polyurethane prepolymer:curing agent = 100:15-25 (mass ratio). Alternatively, fluorinated acrylic resin (fluorine content 8-15wt%, glass transition temperature Tg 40-60℃, molecular weight 30000-80000) can be used, with methyl ethyl ketone (MEK) or butyl acetate (solid content 40-60%) as the solvent. Safety Precautions: MEK and butyl acetate are flammable and volatile organic solvents. Operations should be carried out in a well-ventilated environment, away from fire sources and high temperatures, and equipped with explosion-proof electrical equipment. Environmental Requirements: Volatile organic solvents should be treated by activated carbon adsorption or combustion before being released. The coating thickness is controlled at 25-40μm for wet film and 10-20μm for dry film.

[0068] The topcoat polymer possesses long, flexible molecular chains and a moderately cross-linked molecular structure, exhibiting both toughness and hardness. During friction, it primarily undergoes elastic deformation rather than brittle cracking or tearing. The introduction of fluorine-modified components reduces the surface friction coefficient and provides hydrophobicity and chemical stability. Interfacial bonding between the topcoat and basecoat is formed through molecular chain interpenetration and functional group chemical reactions, preventing interlayer delamination.

[0069] Advantages of the dual-layer structure: The base layer provides heat resistance and hardness support, while the top layer provides wear resistance and toughness protection. The two layers complement each other to form a composite structure, solving the technical bottleneck that a single polymer cannot simultaneously meet the dual requirements of heat resistance and wear resistance.

[0070] Results: A 10-20 μm thick abrasion-resistant topcoat was formed on the surface of the heat-resistant primer layer. This layer had a pencil hardness of H-2H (tested according to GB / T 6739), an elastic modulus of 1.5-3.0 GPa (tested according to ISO 527), and abrasion resistance according to the friction test of GB / T 1768-2006. The wear rate was reduced by one order of magnitude to 10⁻ compared to the single polymer. 5 mm³ / (N·m), surface friction coefficient 0.15-0.25 (tested according to GB / T 10006), and contact angle greater than 90° exhibit good hydrophobicity (tested according to GB / T 30693).

[0071] Step 7: Curing into a film The bilayer polymer system is subjected to final curing at a low temperature of 80-120℃ (preferably 100℃) for 30-60 minutes, allowing the base coat and top coat to form an integrated structure at the interface through interpenetration or chemical bonding. The curing process should be carried out in a ventilated oven with relative humidity controlled at 45-65%.

[0072] A low-temperature curing process is employed to avoid thermal damage to the underlying PVD coating caused by high temperatures, while simultaneously promoting interpenetration of molecular chains and functional group reactions between the two polymer layers. During the curing process, the active groups retained in the base coating undergo a cross-linking reaction with the top coating, forming interfacial chemical bonds and ensuring the integrity of the bilayer structure.

[0073] Results: A double-layer polymer sealing system with a total thickness of 15-30 μm was formed on the surface of the serrated workpiece (thickness tested according to GB / T13452.2), presenting a transparent or semi-transparent protective layer (light transmittance ≥85%, tested according to GB / T 2410). The adhesion reached level 1 (tested according to GB / T 9286), sealing all microscopic defects in the lower layer, maintaining the metallic luster of the PVD coating, and achieving a composite protective structure. The final product passed the neutral salt spray test (according to GB / T 10125) for 2000 h without corrosion and the high and low temperature cycling test (-40℃ to +180℃, 50 cycles) without cracking or peeling.

[0074] Example 8: Surface treatment of automotive transmission gears The selected material is 40Cr steel automotive gearbox gear (module 2.5, number of teeth 35, tooth width 25 mm), with an initial surface roughness Ra 2.1 μm.

[0075] Step 1: Alkaline electrolytic polishing treatment. Prepare an electrolyte solution containing 20% ​​sodium hydroxide and 1% polyethylene glycol (PEG-400), with the workpiece as the anode, a current density of 10 A / dm², a voltage of 12 V, and a treatment time of 10 min. After treatment, the surface roughness Ra is reduced to 0.3 μm.

[0076] Step 2: Phosphating treatment. Wash with 8% dilute nitric acid solution for 45 seconds, then immerse in zinc-based phosphating solution (zinc dihydrogen phosphate 20 g / L, phosphoric acid 20 g / L, zinc nitrate 10 g / L), and treat at 75℃ for 15 min to form a 10 μm thick phosphating film.

[0077] Step 3: PVD coating. A TiN coating was deposited by magnetron sputtering with a vacuum of 3×10⁻³ Pa, an argon partial pressure of 0.3 Pa, a nitrogen partial pressure of 0.2 Pa, a substrate temperature of 400℃, and a sputtering power density of 5 W / cm². A 3 μm thick TiN coating with a hardness of HV2400 was deposited.

[0078] Step 4: Surface cleaning pretreatment. Clean with 8% sodium carbonate solution at 70℃ for 4 min, then lightly polish with alumina slurry with a particle size of 3 μm to increase the surface roughness to Ra 0.5 μm.

[0079] Step 5: Applying the base coat. Use bisphenol A type epoxy resin (epoxy value 0.51 eq / 100g) and amine curing agent in a ratio of 100:30. Apply a 20 μm thick wet film by brushing and pre-cur at 120℃ for 30 min to form a 7 μm base coat with a pencil hardness of 5H.

[0080] Step Six: Topcoat Application. Using aliphatic polyurethane (18% NCO content) and polyol curing agent at a ratio of 100:20, apply a 30 μm thick wet film by brushing to form a 15 μm topcoat.

[0081] Step 7: Curing the film. Curing at 100℃ for 45 min, total thickness 22 μm, light transmittance 88%, adhesion level 1.

[0082] Test results: After 1200 hours of neutral salt spray testing, there was virtually no corrosion (corrosion area <5%). During high and low temperature cycling tests (-40℃ to +180℃, 50 cycles), no cracking occurred, and the wear rate decreased to 8×10⁻⁶. -6 The surface friction coefficient is 0.18 mm³ / (N·m), which meets the requirements for use in automotive gearbox gears.

[0083] Comparative experimental data: Comparative Example 1 (PVD coating only): Corrosion occurred after 500 h of salt spray testing, with a wear rate of 2×10⁻⁶. -4 mm³ / (N·m), coefficient of friction 0.45; Comparative Example 2 (electropolishing + PVD coating): Corrosion occurred after 1200 h of salt spray testing, with a wear rate of 5×10⁻⁶. -5 mm³ / (N·m), coefficient of friction 0.35; Comparative Example 3 (PVD coating + monolayer polymer): softening failure at 180℃ for 24 h, wear rate 6×10-5 mm³ / (N·m), coefficient of friction 0.28; This invention exhibits virtually no corrosion after 1200 hours of salt spray testing, maintains stable performance at 180℃ for 500 hours, and has a wear rate of 8×10⁻⁶. -6 mm³ / (N·m), coefficient of friction 0.18.

[0084] The comprehensive performance index (corrosion resistance × wear resistance × heat resistance) of the five-layer composite structure of the present invention is 48 times that of Comparative Example 1, 8 times that of Comparative Example 2, and 12 times that of Comparative Example 3, demonstrating the significant synergistic effect of multi-layer synergy.

[0085] Experimental verification Experiment 1: Verification Experiment of Multi-Layer Synergistic Protection Effect 1. Experimental Objective The synergistic effect of the five-layer composite protective structure compared with the single-layer or simple stacked structure was verified. The corrosion resistance performance of different protective systems was quantitatively evaluated through accelerated corrosion tests, demonstrating the significant advantages of multi-layer synergistic protection.

[0086] 2. Preparation of experimental samples Four sets of control samples were prepared, with five parallel samples in each set: Sample A: PVD coating only (control group 1); Sample B: Electropolishing + Phosphating + PVD Coating (Control Group 2); Sample C: PVD coating + monolayer polymer sealing (control group 3); Sample D: Complete five-layer composite protective structure (this invention); All samples were prepared using the same 40Cr steel sawtooth matrix (module 2.5, number of teeth 35) according to the process parameters of Example 1.

[0087] 3. Experimental conditions Test standard: GB / T 10125-2012 "Artificial Atmosphere Corrosion Test - Salt Spray Test"; Salt spray concentration: 5% NaCl solution; Test temperature: 35±2℃; Relative humidity: ≥95%; Spray pressure: 80-120 kPa; Test duration: 0-3000 hours of continuous testing.

[0088] 4. Experimental Procedure (1) Sample pretreatment: Clean the sample surface with anhydrous ethanol, dry it, and record the initial mass; (2) Fix the samples on the test rack to ensure that the samples do not come into contact with each other; (3) Start the salt spray test chamber and adjust the temperature, humidity and salt spray concentration to the standard conditions; (4) Take out the sample every 200 hours, rinse it with deionized water and dry it, and observe the corrosion status; (5) Take photos to record the corrosion morphology and measure the corrosion area ratio; (6) Weigh the weight using an electronic balance and calculate the mass loss rate; (7) Repeat steps (4) to (6) until the experiment ends.

[0089] 5. Experimental Results Table 1 Comparison of corrosion resistance performance of different protection systems in salt spray test

[0090] Figure 1 These are corrosion resistance curves for different protection systems.

[0091] 6. Analysis and Summary Experimental results show that the five-layer composite protective structure (sample D) exhibits excellent corrosion resistance in salt spray tests. After 2000 hours, the corrosion area of ​​the five-layer composite structure is only 13.2%, far lower than the severe corrosion conditions of the other three protective schemes (corrosion area exceeding 75%).

[0092] At 3000 hours, when the other three protection schemes had completely failed, the corrosion area of ​​the five-layer composite structure was only 41.2%. The synergistic effect calculation showed that the corrosion resistance of the five-layer composite structure was 24 times that of a single PVD coating, 7.3 times that of an electropolishing + phosphating + PVD structure, and 7.8 times that of a PVD + single-layer polymer structure, which fully verified the significant synergistic effect of multi-layer protection.

[0093] Experiment 2: High-Temperature Wear Resistance Test 1. Experimental Objective The wear resistance of the double-layer polymer closed system under high temperature environment was verified, proving that the present invention has broken through the technical bottleneck of traditional polymer softening failure at high temperature and achieved synergistic optimization of heat resistance and wear resistance.

[0094] 2. Preparation of experimental samples Prepare 3 sets of control samples, with 3 parallel samples in each set: Sample E: Conventional single-layer polymer block (acrylic resin with a glass transition temperature of 80°C); Sample F: Single heat-resistant polymer block (epoxy resin with a glass transition temperature of 160°C). Sample G: A two-layer polymer-sealed system (this invention, heat-resistant primer + abrasion-resistant topcoat); All samples were prepared on the same electropolished + phosphating + PVD substrate. The PVD coating was 3 μm thick TiN, and the total thickness of the polymer layer was controlled between 15-20 μm.

[0095] 3. Experimental conditions Testing equipment: High-temperature friction and wear testing machine (ball-disc configuration); Grinding balls: Si3N4 ceramic balls with a diameter of 6mm; Load: 5N; Sliding speed: 0.1 m / s; Sliding distance: 500m each time; Test temperatures: 25℃, 80℃, 120℃, 160℃, 180℃; Environment: Dry friction conditions; Test standard: GB / T 12444-2006 "Metallic materials wear test method".

[0096] 4. Experimental Procedure (1) Sample pretreatment: Clean the sample surface with acetone and dry it in an oven at 100°C for 30 minutes; (2) Measure the initial surface profile of the sample using a coordinate measuring machine and record the reference data; (3) Install the sample on the heating table of the testing machine, heat it to the target temperature and stabilize it for 15 minutes; (4) Start the friction test and record the change in the friction coefficient in real time; (5) After the test, cool the sample to room temperature; (6) Clean the worn surface and measure the depth and width of the wear marks using a coordinate measuring machine; (7) Calculate the wear volume and wear rate; (8) Repeat the test for each temperature point and obtain the average value.

[0097] 5. Experimental Results Table 2 Comparison of high-temperature wear resistance of different polymer-encapsulated systems

[0098] Note: The polymer layer of sample E completely softened and failed at 160℃, so no valid data could be obtained.

[0099] Figure 2 This is a comparison of friction coefficients under high temperature conditions.

[0100] 6. Analysis and Summary Experimental results show that the bilayer polymer-sealed system (sample G) exhibits excellent wear resistance under high-temperature conditions. At 180℃, the wear rate of the bilayer system is only 25 × 10⁻⁶. -6The heat resistance is reduced by 86% compared to a single heat-resistant polymer, while the coefficient of friction remains at a low level of 0.26. Conventional single-layer polymers fail completely at 160℃, while the two-layer system can still function normally at 180℃, which fully demonstrates the synergistic optimization effect of the functionally layered heat-resistant base coating and wear-resistant top coating, successfully breaking through the technical bottleneck of high-temperature softening of traditional polymers.

[0101] Experiment 3: Test on the uniformity of serrated groove protection 1. Experimental Objective The uniform coverage effect of the five-layer composite protective structure on the complex serrated surface was verified, especially in the deep groove area that is difficult to cover effectively by traditional PVD process, proving the technical advantage of the present invention in completely eliminating the protection blind spot.

[0102] 2. Preparation of experimental samples Two sets of control samples were prepared, with five parallel samples in each set: Sample H: Traditional PVD coating (TiN directly deposited on a serrated substrate) Sample I: Five-layer composite protective structure (complete process flow) Standardized sawtooth specimens were used: made of 40Cr steel, with a module of 2.5, 35 teeth, a tooth surface inclination angle of 20°, a tooth groove depth of 5 mm, a tooth groove width of 2 mm, and an initial surface roughness Ra of 2.1 μm.

[0103] 3. Experimental conditions Testing equipment: Scanning electron microscope (SEM, resolution 1nm); Energy dispersive spectroscopy analysis: X-ray energy dispersive spectroscopy (EDS); Thickness measurement: X-ray fluorescence spectrometry (XRF); Surface morphology: Laser confocal microscopy Cross-sectional analysis: Sample preparation via focused ion beam cutting (FIB); Measurement point selection: tooth tip, middle of tooth surface, tooth root, bottom of groove, side wall of groove.

[0104] 4. Experimental Procedure (1) Sample pretreatment: Cut the sample into 20mm×15mm×5mm sizes for easy observation under a microscope; (2) Surface morphology observation: The surface morphology at each key location was observed using a laser confocal microscope; (3) SEM morphology analysis: Observe the coating coverage at different magnifications; (4) EDS composition analysis: Elemental composition analysis was performed at each measurement point to confirm the coating composition; (5) Thickness distribution measurement: The coating thickness distribution at each location was measured using XRF; (6) FIB section preparation: Select typical locations to prepare section samples; (7) Cross-sectional microscopic analysis: Observe the bonding state and thickness distribution of each layer; (8) Data statistical analysis: Calculate the uniformity of thickness distribution and coverage integrity.

[0105] 5. Experimental Results Table 3 Comparison of protective layer thickness distribution at different parts of the saw teeth (unit: μm)

[0106] Note: Coverage integrity is defined as the percentage of the total surface area where the effective protective layer thickness exceeds 1 μm.

[0107] Figure 3 It is a three-dimensional visualization of the thickness distribution of the protective layer on the sawtooth surface.

[0108] Figure 4 This is a microscopic representation of a portion of the serrations. Figure 4 The area within the red box is the hardness observation point.

[0109] 6. Analysis and Summary Experimental results clearly demonstrate the superior uniform coverage of the five-layer composite protective structure on surfaces with complex serrated morphology. Traditional PVD processes have a thickness of only 0.3 μm at the bottom of the groove, resulting in a severe protection blind zone, while the five-layer composite structure achieves a thickness of 16.4 μm at the same location, representing an improvement of over 5000%.

[0110] Overall coverage integrity improved from 65% to 98%, with a thickness distribution standard deviation of only 1.1 μm, significantly better than the 1.2 μm of traditional processes. The synergistic effect of the bubble cleaning effect of electropolishing, the penetration coverage of phosphating, and the flow filling of the double-layer polymer completely eliminated the protective blind spots of the serrated grooves, achieving true full-surface uniform protection.

[0111] The embodiments of the present invention have been described above. However, the embodiments are not limited to the specific implementation methods described above. The specific implementation methods described above are merely illustrative and not restrictive. Those skilled in the art can make more equivalent embodiments under the guidance of the present embodiments, and all of them are within the protection scope of the present embodiments.

Claims

1. A PVD treatment method for sawtooth patterns, characterized in that, Includes the following steps: Step 1: Alkaline electrolytic polishing treatment: The serrated workpiece is placed as the anode in a 15-25% sodium hydroxide aqueous solution, with 0.5-2% polyethylene glycol added as an organic additive, and an anodic current density of 5-15 A / dm³ is applied. 2 The electrolysis voltage is 8-20V, and the processing time is 5-15 minutes. Through electrochemical dissolution, the surface roughness of the saw teeth is reduced from Ra 1-3μm to Ra 0.2-0.5μm, resulting in a smooth surface. Step 2: Phosphating treatment: After pickling and neutralization, the saw teeth are immersed in a phosphating solution for chemical phosphating treatment. The phosphating solution uses a zinc-based or manganese-based phosphating system, the treatment temperature is 65-95℃, and the time is 10-25 minutes, forming a uniform phosphating film of 5-15μm thickness on the saw teeth surface. Step 3: PVD Coating: Titanium nitride, chromium nitride, or titanium aluminum nitride hard coatings are deposited on phosphating substrates using magnetron sputtering physical vapor deposition technology, with a coating thickness of 2-5 μm. Step 4: Surface pretreatment: The PVD coating surface is cleaned and slightly roughened to increase the surface roughness from 0.1-0.3 μm to 0.3-0.8 μm; Step 5: Apply heat-resistant primer: Apply a heat-resistant polymer base coat with a glass transition temperature of 150-180℃ and a thickness of 5-10μm; Step 6: Apply abrasion-resistant surface coating: A flexible and wear-resistant polymer topcoat with a thickness of 10-20 μm is applied to the surface of the base coating. Step 7: Curing into a film: Curing at 80-120℃ for 30-60 minutes forms a five-layer composite protective structure.

2. The serrated PVD treatment method according to claim 1, characterized in that, In the alkaline electrolytic polishing process, oxygen bubbles generated on the anode surface during electrolysis mechanically stir and clean the serrated grooves, removing contaminants and oxide layers deep within the grooves.

3. The serrated PVD treatment method according to claim 1, characterized in that, In the phosphating treatment, the zinc-based phosphating system contains 15-25 g / L zinc dihydrogen phosphate, 15-25 g / L phosphoric acid, and 5-15 g / L zinc nitrate, with a treatment temperature of 65-85℃; the manganese-based phosphating system contains 20-30 g / L manganese dihydrogen phosphate, 20-30 g / L phosphoric acid, and 10-20 g / L manganese nitrate, with a treatment temperature of 85-95℃.

4. The serrated PVD treatment method according to claim 1, characterized in that, The PVD coating process parameters are: vacuum degree ≤ 5 × 10⁻⁶. -3 Pa, argon partial pressure 0.2-0.5 Pa, nitrogen partial pressure 0.1-0.3 Pa, substrate temperature 350-450℃, sputtering power density 3-8 W / cm², deposition rate 0.5-2.0 μm / h.

5. The serrated PVD treatment method according to claim 1, characterized in that, The surface pretreatment involves cleaning with an alkaline degreasing cleaner at 5-10% by mass at 60-80°C for 3-5 minutes, followed by light polishing with alumina polishing paste with a particle size of 1-5μm or 600-1000 grit sandpaper.

6. The serrated PVD treatment method according to claim 1, characterized in that, The heat-resistant primer coating uses bisphenol A type epoxy resin combined with an aliphatic amine curing agent, with a mixing ratio of epoxy resin:curing agent = 100: 25-35, or uses a polyimide precursor solution with a solid content of 20-35%.

7. The serrated PVD treatment method according to claim 1, characterized in that, The wear-resistant surface coating uses aliphatic polyurethane combined with a polyol curing agent, with a mixing ratio of polyurethane prepolymer: curing agent = 100: 15-25, or uses fluorine-modified acrylic resin with a fluorine content of 8-15wt%.

8. The serrated PVD treatment method according to claim 1, characterized in that, The heat-resistant undercoat and wear-resistant topcoat form interfacial bonds at the interface through molecular chain segment interpenetration and functional group chemical reactions, thus avoiding interlayer delamination.

9. The serrated PVD treatment method according to claim 1, characterized in that, The five-layer composite protective structure consists of an electrolytic polishing leveling layer, a phosphating conversion film, a PVD hard layer, a heat-resistant base coating, and a wear-resistant top coating. Each layer is tightly bonded together through chemical bonding, mechanical interlocking, and physical filling.

10. The serrated PVD treatment method according to claim 1, characterized in that, The composite protective structure has a total thickness of 15-30μm, a light transmittance of ≥85%, an adhesion level of 1, and shows virtually no corrosion after 1200 hours of neutral salt spray testing. It also shows no cracking or peeling during high and low temperature cycling tests from -40℃ to +180℃.

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