High-hardness sawtooth sputter coating method

Abstract

The invention relates to the technical field of surface treatment, and discloses a high-hardness sawtooth sputter coating method which comprises the steps of multi-element corrosion inhibitor composite conversion film treatment, boron-containing nitride double-layer sputter coating, sol-gel compact sealing layer treatment, chemical vapor infiltration strengthening treatment and low-temperature plasma polymerization hole sealing treatment. According to the method, a Cr-Mo-W-rare earth-organic phosphonic acid composite conversion film, an AlTiB (C) N superhard bottom layer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 compact gel layer, a CVI strengthening layer and a SiOC polymer hole sealing layer are sequentially formed on the surface of a sawtooth base body, and a sextuple synergistic protection structure is constructed. The surface hardness of the obtained coating reaches HV4500-5000, the corrosion resistance to various corrosive media such as acidity, alkalinity, salt mist and sulfide is remarkably improved, the service life is prolonged by 4-6 times, and the problem of rapid failure of the high-hardness boron-containing nitride coating in a complex corrosive environment is solved.

Description

Technical Field

[0001] This invention relates to the field of surface treatment technology, and more specifically, to a high-hardness serrated sputtering coating method. Background Technology

[0002] Traditional nitride coatings such as TiN and CrN typically have a hardness in the HV2000-3000 range, which is close to the performance limit and cannot meet the higher hardness requirements for machining difficult-to-machine materials such as superhard materials and ceramics. Boron-containing nitride coatings can increase the hardness to over HV4000, but they face serious corrosion failure problems when machining in corrosive environments such as marine environments, chemical industries, and food processing.

[0003] The existing technology has the following defects: the single chromate-phosphate conversion film exhibits selective and rapid failure under the alternating erosion of complex corrosive media such as acidic cutting fluid (pH 3-5), alkaline cleaning agents (pH 10-13), sulfur-containing compounds, and organic solvents; the columnar grain boundaries of the sputtered ceramic layer become rapid penetration channels for corrosive media; and the multiphase ceramic layer suffers from microgalvanic corrosion due to differences in electrochemical potential, with the active phase preferentially dissolving to form pores and cracks. Summary of the Invention

[0004] To solve the above-mentioned technical problems, the present invention provides a high-hardness serrated sputtering coating method, comprising the following steps: Step 1: Treatment with multi-component corrosion inhibitor composite conversion film: A first conversion film containing molybdate and tungstate and a second composite phosphate conversion film containing rare earth elements and organophosphonic acid are sequentially formed on the surface of the serrated substrate. Step 2: Boron-nitride double-layer sputtering coating: An AlTiB(C)N ultrahard underlayer and an AlCrNO corrosion-resistant surface layer were sequentially deposited using a sputtering process. Step 3: Sol-gel sealing treatment: The silicate-aluminate composite sol was impregnated and coated onto the AlCrNO corrosion-resistant surface layer, and a SiO2-Al2O3 composite oxide gel layer was formed by penetrating into the columnar grain boundaries and curing in situ. Step 4: Enhanced Chemical Vapor Infiltration Treatment A silicon-containing organic gas precursor is introduced to deposit SiO2 within the gel layer. x Alternatively, SiC nanoparticles can be used to fill and densify the pores. Step 5: Low-temperature plasma polymerization sealing treatment: HMDSO was used as a precursor for plasma polymerization to form a SiOC polymer film on the surface.

[0005] Preferably, the first conversion film is formed by the following steps: immersing the saw teeth in a modified chromate solution containing potassium dichromate, sodium molybdate and sodium tungstate, and treating it at 60-80°C for 10-15 minutes to form a Cr-Mo-W composite oxide conversion film with a thickness of 0.5-1 μm.

[0006] Preferably, the second layer of composite phosphate conversion membrane is formed by the following steps: immersing the saw teeth treated with the first layer of conversion membrane into a modified phosphating solution containing zinc phosphate, manganese phosphate, cerium nitrate or lanthanum nitrate and hydroxyethylidene diphosphonic acid (HEDP), and treating at 80-95°C for 15-20 minutes to form a 1-2 μm thick composite phosphate conversion membrane containing rare earth elements and organophosphonic acids.

[0007] Preferably, the deposition parameters of the AlTiB(C)N ultrahard substrate are as follows: using a boron-containing nitride composite target or a TiAlN target combined with reactive sputtering, introducing a boron-containing reactive gas with a boron content of 10-12 atomic percentages, using a medium-frequency pulse sputtering mode, a substrate bias voltage of -80V to -150V, a deposition temperature of 300-400℃, and a thickness of 3-4μm.

[0008] Preferably, the deposition parameters of the AlCrNO corrosion-resistant surface layer are as follows: aluminum-chromium alloy target material is used for reactive sputtering in a nitrogen-oxygen mixed reactive gas, the nitrogen-oxygen volume ratio is controlled at 4:1 to 5:1, DC magnetron sputtering mode is used, the substrate bias voltage is -50V to -100V, the deposition temperature is 300-350℃, and the thickness is 1-2μm.

[0009] Preferably, the silicate-aluminate composite sol is prepared using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide as precursors, with a molar ratio controlled between 3:1 and 5:1. It is coated by dip-coating process and cured at 150-200℃ to form a 0.2-0.3 μm thick SiO2-Al2O3 composite oxide gel layer.

[0010] Preferably, the process conditions for the chemical vapor infiltration enhancement treatment are: temperature 350-400℃, pressure 100-1000 Pa, methyltrichlorosilane or tetramethylsilane as precursor, treatment time 30-60 minutes, and filler accounting for 10-20% of the gel layer volume.

[0011] Preferably, the process conditions for the low-temperature plasma polymerization sealing treatment are: substrate temperature 80-120℃, radio frequency power 100-300W, reaction pressure 10-100 Pa, deposition rate 50-200nm / min, forming a SiOC polymer film with a thickness of 0.3-0.5μm.

[0012] Preferably, the coating obtained by the method consists of, from the inside out: a multi-element corrosion inhibitor composite conversion film, an AlTiB(C)N superhard underlayer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 gel layer, a CVI reinforcement layer, and a SiOC polymer film, with a total thickness of 6-10 μm.

[0013] Preferably, the coating obtained by the method has a surface hardness of HV4500-5000, shows no corrosion marks in a neutral salt spray test for 1600-2000 hours, and has a service life that is 4-6 times longer than that of uncoated serrations.

[0014] The beneficial effects of this invention are as follows: Breakthroughs in hardness and wear resistance: The surface hardness of the obtained composite coating reaches HV4500-5000, an improvement of 50-100% or more compared to traditional TiN and CrN coatings (HV2000-3000). The hardness of the boron-containing nitride AlTiB(C)N underlayer exceeds HV4800; the dense amorphous structure formed by boron and the hard BN phase are the main reasons for achieving ultra-high hardness. The wear resistance of the coating is improved by 40-50%, meeting the cutting requirements of difficult-to-machine materials such as superhard materials and ceramic materials.

[0015] Significantly enhanced broad-spectrum corrosion resistance: The multi-element corrosion inhibitor composite conversion film achieves broad-spectrum protection against a variety of corrosive media: resistance to acidic media is improved by 150-200%, resistance to alkaline media by 100-150%, resistance to chlorides by 80-120%, and resistance to sulfides by over 200%. It eliminates the selective failure problem of single conversion film treatment methods, extending the overall corrosion resistance life by 100-150% in complex and variable media environments.

[0016] A fundamental solution to the problems of grain boundary penetration and micro-galvanic corrosion: The sol-gel layer successfully penetrated and sealed the columnar grain boundaries and micropores of the AlCrNO ceramic layer. CVI reinforcement brought the density of the sealing layer close to 100% and reduced permeability by 2-3 orders of magnitude, fundamentally eliminating the problem of grain boundaries acting as corrosion channels. The amorphous structure and homogeneous composition of the gel layer eliminated micro-galvanic corrosion between different phases, significantly improving the overall protective reliability of the coating.

[0017] Multiple synergistic protection effects: The six-layer protective structure targets different failure modes, including matrix corrosion, interface corrosion, grain boundary penetration, microgalvanic corrosion, and surface defect penetration. Each layer performs a different protective function, and the synergistic effect between the layers produces an exponential enhancement of protection. The reliability of the protection far exceeds that of single or simple superposition protection methods, and it can maintain long-term stable protective performance even in extreme corrosive environments.

[0018] Significantly extended service life: Service life in corrosive environments is extended by 4-6 times, and salt spray tests can reach over 1600-2000 hours with no obvious corrosion marks. It is particularly suitable for harsh applications such as multi-process cutting in the chemical industry, long-term service in marine engineering, and frequent cleaning and disinfection in food processing, greatly reducing tool replacement frequency and maintenance costs, resulting in significant economic benefits. Attached Figure Description

[0019] Figure 1 This is a bar graph comparing the hardness of different coating samples of the present invention; Figure 2 This is a bar chart comparing the weight loss rates in different corrosive media according to the present invention; Figure 3 This is a radar chart of the broad-spectrum corrosion resistance of the present invention; Figure 4 This is a bar graph showing the gradual improvement in the protective performance of the present invention; Figure 5 This is a line graph illustrating the layer-by-layer enhancement effect of the synergistic protection of the present invention. Detailed Implementation

[0020] 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.

[0021] Example 1: This example proposes a high-hardness serrated sputtering coating method, including the following steps: Step 1: Treatment with multi-component corrosion inhibitor composite conversion film: A first conversion film containing molybdate and tungstate and a second composite phosphate conversion film containing rare earth elements and organophosphonic acid are sequentially formed on the surface of the serrated substrate. The first conversion film is formed by the following steps: immersing the saw teeth in a modified chromate solution containing potassium dichromate, sodium molybdate and sodium tungstate, and treating it at 70°C for 12 minutes to form a 0.8 μm thick Cr-Mo-W composite oxide conversion film; The second layer of composite phosphate conversion membrane is formed by the following steps: the saw teeth treated with the first layer of conversion membrane are immersed in a modified phosphating solution containing zinc phosphate, manganese phosphate, cerium nitrate and hydroxyethylidene diphosphonic acid (HEDP), and treated at 90°C for 18 minutes to form a 1.5 μm thick composite phosphate conversion membrane containing rare earth elements and organophosphonic acids.

[0022] Step 2: Boron-nitride double-layer sputtering coating: An AlTiB(C)N ultrahard underlayer and an AlCrNO corrosion-resistant surface layer were sequentially deposited using a sputtering process. The deposition parameters for the AlTiB(C)N ultrahard substrate are as follows: using a boron-containing nitride composite target combined with reactive sputtering, introducing a boron-containing reactive gas with a boron content of 11 atomic percent, using a medium-frequency pulse sputtering mode, a substrate bias voltage of -115V, a deposition temperature of 350℃, and a thickness of 3.5μm. The deposition parameters for the AlCrNO corrosion-resistant surface layer are as follows: aluminum-chromium alloy target material is used for reactive sputtering in a nitrogen-oxygen mixed reactive gas, the nitrogen-oxygen volume ratio is controlled at 4.5:1, DC magnetron sputtering mode is used, the substrate bias voltage is -75V, the deposition temperature is 325℃, and the thickness is 1.5μm.

[0023] Step 3: Sol-gel sealing treatment: The silicate-aluminate composite sol was impregnated and coated onto the AlCrNO corrosion-resistant surface layer, and a SiO2-Al2O3 composite oxide gel layer was formed by penetrating into the columnar grain boundaries and curing in situ. The silicate-aluminate composite sol was prepared using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide as precursors, with a molar ratio controlled at 4:1. It was coated by dip-coating process and cured at 175°C to form a 0.25 μm thick SiO2-Al2O3 composite oxide gel layer.

[0024] Step 4: Enhanced Chemical Vapor Infiltration Treatment A silicon-containing organic gas precursor is introduced to deposit SiO2 within the gel layer. x Nanoparticles are used to fill and densify pores; The process conditions for chemical vapor infiltration enhancement treatment are: temperature 375℃, pressure 550 Pa, methyltrichlorosilane as precursor, treatment time 45 minutes, and filler accounting for 15% of the gel layer volume.

[0025] Step 5: Low-temperature plasma polymerization sealing treatment: HMDSO was used as a precursor for plasma polymerization to form a SiOC polymer film on the surface.

[0026] The process conditions for low-temperature plasma polymerization sealing were: substrate temperature 100℃, RF power 200W, reaction pressure 55 Pa, deposition rate 125nm / min, forming a 0.4μm thick SiOC polymer film.

[0027] The coating obtained by this method consists of, from the inside out: a multi-element corrosion inhibitor composite conversion film, an AlTiB(C)N superhard underlayer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 gel layer, a CVI reinforcement layer, and a SiOC polymer film, with a total thickness of 8 μm.

[0028] The coating obtained by this method has a surface hardness of HV4750, and no corrosion marks were found after 1800 hours of neutral salt spray testing. Its service life is extended by 5 times compared to the uncoated serrations.

[0029] Example 2 differs from Example 1 in that: The first conversion film is formed by the following steps: treating at 60°C for 10 minutes to form a 0.5 μm thick Cr-Mo-W composite oxide conversion film; The second layer of composite phosphate conversion membrane is formed by the following steps: the saw teeth treated with the first layer of conversion membrane are immersed in a modified phosphating solution containing zinc phosphate, manganese phosphate, lanthanum nitrate and hydroxyethylidene diphosphonic acid (HEDP), and treated at 80°C for 15 minutes to form a 1 μm thick composite phosphate conversion membrane containing rare earth elements and organophosphonic acids.

[0030] The deposition parameters for the AlTiB(C)N ultrahard substrate are as follows: TiAlN target material combined with reactive sputtering, boron-containing reactive gas with a boron content of 10 atomic percent, medium frequency pulse sputtering mode, substrate bias voltage -80V, deposition temperature 300℃, and thickness 3μm. The deposition parameters for the AlCrNO corrosion-resistant surface layer are as follows: aluminum-chromium alloy target material is used for reactive sputtering in a nitrogen-oxygen mixed reactive gas, the nitrogen-oxygen volume ratio is controlled at 4:1, DC magnetron sputtering mode is used, the substrate bias voltage is -50V, the deposition temperature is 300℃, and the thickness is 1μm.

[0031] The silicate-aluminate composite sol was prepared using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide as precursors, with a molar ratio controlled at 3:1. It was coated by dip-coating process and cured at 150°C to form a 0.2 μm thick SiO2-Al2O3 composite oxide gel layer.

[0032] Chemical vapor infiltration enhancement treatment: A silicon-containing organic gas precursor is introduced, and SiC nanoparticles are deposited in the gel layer to fill and densify the pores. The process conditions for chemical vapor infiltration enhancement treatment are: temperature 350℃, pressure 100 Pa, tetramethylsilane as precursor, treatment time 30 minutes, and filler accounting for 10% of the gel layer volume.

[0033] The process conditions for low-temperature plasma polymerization sealing were: substrate temperature 80℃, RF power 100W, reaction pressure 10 Pa, deposition rate 50nm / min, forming a 0.3μm thick SiOC polymer film.

[0034] The coating obtained by this method consists of, from the inside out: a multi-element corrosion inhibitor composite conversion film, an AlTiB(C)N superhard underlayer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 gel layer, a CVI reinforcement layer, and a SiOC polymer film, with a total thickness of 6 μm.

[0035] The coating obtained by this method has a surface hardness of HV4500, and no corrosion marks were found after 1600 hours of neutral salt spray testing. Its service life is extended by 4 times compared to the uncoated serrations.

[0036] Example 3 differs from Example 1 in that: The first conversion film is formed by the following steps: treating at 80°C for 15 minutes to form a 1μm thick Cr-Mo-W composite oxide conversion film; The second layer of composite phosphate conversion membrane is formed by the following steps: treating at 95°C for 20 minutes to form a 2μm thick composite phosphate conversion membrane containing rare earth elements and organophosphonic acids.

[0037] The deposition parameters for the AlTiB(C)N ultrahard substrate are as follows: boron-containing reactive gas with a boron content of 12 atomic percent, medium-frequency pulse sputtering mode, substrate bias voltage of -150V, deposition temperature of 400℃, and thickness of 4μm. The deposition parameters for the AlCrNO corrosion-resistant surface layer are as follows: aluminum-chromium alloy target material is used for reactive sputtering in a nitrogen-oxygen mixed reactive gas, the nitrogen-oxygen volume ratio is controlled at 5:1, DC magnetron sputtering mode is used, the substrate bias voltage is -100V, the deposition temperature is 350℃, and the thickness is 2μm.

[0038] The silicate-aluminate composite sol was prepared using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide as precursors, with a molar ratio controlled at 5:1. It was coated by dip-coating process and cured at 200℃ to form a 0.3 μm thick SiO2-Al2O3 composite oxide gel layer.

[0039] The process conditions for chemical vapor infiltration enhancement treatment are: temperature 400℃, pressure 1000 Pa, treatment time 60 minutes, and filler accounting for 20% of the gel layer volume.

[0040] The process conditions for low-temperature plasma polymerization sealing are as follows: substrate temperature 120℃, RF power 300W, reaction pressure 100 Pa, deposition rate 200nm / min, forming a SiOC polymer film with a thickness of 0.5μm.

[0041] The coating obtained by this method consists of, from the inside out: a multi-element corrosion inhibitor composite conversion film, an AlTiB(C)N superhard underlayer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 gel layer, a CVI reinforcement layer, and a SiOC polymer film, with a total thickness of 10 μm.

[0042] The coating obtained by this method has a surface hardness of HV5000, shows no corrosion marks after 2000 hours of neutral salt spray testing, and has a service life that is 6 times longer than that of uncoated serrations.

[0043] Example 4: This example proposes a high-hardness serrated sputtering coating method, including the following steps: Step 1: Pretreatment of the serrated substrate The serrated substrate is pretreated using a conventional degreasing process to remove surface oil and impurities, providing a clean surface for subsequent conversion film treatment.

[0044] Specific degreasing operations: (1) Ultrasonic degreasing: Immerse the saw teeth in an alkaline degreasing solution (sodium hydroxide 15-20g / L, trisodium phosphate 10-15g / L, surfactant 5-8g / L) and ultrasonically clean for 15-20 minutes at 40-60℃. (2) Wash with water: Rinse with running tap water for 2-3 minutes; (3) Pickling and activation: Treat with 5-10% hydrochloric acid solution for 2-5 minutes to remove the oxide film; (4) Wash and dry again. The treated surface should be free of oil film (judged by the wetting angle of a water droplet; a wetting angle <30° is acceptable).

[0045] Step 2: Treatment with multi-component corrosion inhibitor composite conversion coating Step 2.1: Formation of the first Cr-Mo-W composite oxide conversion film Preparation of modified chromate solution: Based on chromate conversion solution (concentration 10-20 g / L) with potassium dichromate (K2Cr2O7, analytical grade, purity ≥99.5%) as the main component, add sodium molybdate (Na2MoO4·2H2O, analytical grade, purity ≥99.0%, concentration 2-5 g / L) and sodium tungstate (Na2WO4·2H2O, analytical grade, purity ≥99.0%, concentration 3-6 g / L).

[0046] The pH of the solution should be controlled between 1.5 and 2.5 (adjusted with nitric acid). Molybdate and tungstate ions are broad-spectrum corrosion inhibitors. Their corrosion inhibition principle is to form a protective film of insoluble molybdate and tungstate on the metal surface, which has a corrosion inhibition effect on acidic, alkaline, and neutral environments.

[0047] The saw teeth are immersed in a modified chromate solution at a controlled temperature of 60-80℃ for 10-15 minutes. During the conversion process, chromate, molybdate, and tungstate ions are co-deposited on the substrate surface through a chemical conversion reaction, forming a 0.5-1 μm thick Cr-Mo-W composite oxide conversion film. This film, composed of Cr2O3, MoO3, WO3, and their composite oxides, exhibits superior broad-spectrum corrosion resistance compared to single chromate conversion films.

[0048] Step 2.2: Formation of the second rare earth-organophosphonic acid composite phosphate conversion membrane Preparation of modified phosphating solution: Based on a phosphating solution composed of zinc phosphate (Zn3(PO4)2·4H2O, industrial grade, concentration 15-25 g / L), manganese phosphate (Mn3(PO4)2·7H2O, industrial grade, concentration 5-10 g / L), and phosphoric acid (H3PO4, analytical grade, concentration 85%, dosage 10-20 ml / L), add cerium nitrate (Ce(NO3)3·6H2O, analytical grade, purity ≥99.0%) or lanthanum nitrate (La(NO3)3·6H2O, analytical grade, purity ≥99.0%) (concentration 1-3 g / L) and hydroxyethylidene diphosphonic acid (HEDP) (C2H8O7P2, analytical grade, purity ≥60%, concentration 0.5-2 g / L). The pH of the solution should be controlled at 2.8-3.2 (adjusted with ammonia or phosphoric acid). Rare earth ions can form stable CeO2 or La2O3 oxide films on metal surfaces, improving the density and stability of conversion films; organophosphonic acid molecules form stable five-membered ring complexes with metal ions through their phosphonic acid groups, and are adsorbed on the surface through van der Waals forces and hydrogen bonds, forming an organic-inorganic composite protective layer.

[0049] After the first step of treatment, the saw teeth are washed with water and then immersed in a modified phosphating solution, with the temperature controlled at 80-95℃ and the treatment time at 15-20 minutes. During the phosphating process, phosphate ions, rare earth ions, and organophosphonic acid molecules work synergistically to form a 1-2 μm thick composite phosphate conversion film containing rare earth elements and organophosphonic acids on the surface of the first conversion film. This film contains cerium phosphate or lanthanum phosphate crystals, a matrix phosphating layer, and dispersed CeO2 or La2O3 oxide particles and organophosphonic acid complexes.

[0050] Testing standards for the second conversion coating: (1) Total thickness: The total thickness of the double-layer conversion film was measured using an eddy current thickness gauge. The acceptable range was 1.5-3.0 μm. (2) Surface appearance: It presents a uniform gray to dark gray color with no obvious color difference or defects; (3) Component verification: The characteristic peaks of organophosphonic acids (PO bonds at 1000-1100 cm⁻¹) were detected by Fourier transform infrared spectroscopy (FTIR). -1 X-ray diffraction (XRD) was used to detect the phosphate and rare earth oxide crystal phases. (4) Corrosion resistance test: After 48 hours of neutral salt spray test (NSS), no red rust should appear on the surface; (5) Adhesion: The critical load for the adhesion between the double film and the substrate (scratch test) should be ≥20N.

[0051] Cleaning and drying after conversion coating treatment: After conversion coating treatment, thoroughly rinse the workpiece surface with deionized water (resistivity ≥18MΩ·cm) to remove residual chemical solution. Rinse for 3-5 minutes, ensuring the surface pH value is close to neutral (6.5-7.5). Then dry in an oven at 80-100℃ for 30-60 minutes, or blow dry with compressed air (dew point ≤-40℃), ensuring the surface is completely dry and free of water stains. Valuable material recycling and waste liquid treatment: (1) Rare earth element recovery: Waste liquid containing rare earth elements is recovered by oxalic acid precipitation. 10% oxalic acid solution (H2C2O4·2H2O) is added to the waste liquid to adjust the pH to 2.0-2.5. Rare earth ions form rare earth oxalate precipitate. The precipitate is collected by filtration and calcined at 500-600℃ for 3 hours to obtain rare earth oxides. The recovery rate can reach 85-90%. The recovered rare earth oxides can be redissolved to prepare nitrate solution for reuse.

[0052] (2) Recovery of molybdenum and tungsten elements: The waste liquid containing molybdate and tungstate is adjusted to pH 1.0-1.5, and calcium chloride solution (CaCl2, concentration 5-10g / L) is added to form calcium molybdate and calcium tungstate precipitates. After filtration and collection, the precipitates are dissolved in dilute hydrochloric acid, and then the pH is adjusted to 7-8 with ammonia water to reprecipitate and separate. The recovery rate can reach 75-80%.

[0053] (3) General waste liquid treatment: chromate-containing waste liquid should first be treated with ferrous sulfate (FeSO4·7H2O, dosage according to Cr...) 6+ :Fe 2+ (Calculated at a molar ratio of 1:6) Reduction of Cr 6+ For Cr 3+ Then, the pH was adjusted to 8-9 with lime milk to precipitate chromium ions as Cr(OH)3. The treated wastewater met the GB 8978-1996 Integrated Wastewater Discharge Standard.

[0054] (4) Economic benefit assessment: Rare earth element recovery can save 30-40% of raw material costs, molybdenum and tungsten element recovery can save 20-25% of costs, and waste liquid treatment costs are about 15-20 yuan / m³. The overall recovery process has good economic feasibility.

[0055] The double-layer composite conversion coating integrates multiple anti-corrosion components such as chromates, phosphates, molybdates, tungstates, rare earth oxides, and organophosphonic acid complexes, providing protection against various corrosive media such as acids, alkalis, salts, sulfides, and oxidants, thus eliminating the selective failure problem of single conversion coating treatment methods.

[0056] Step 3: Boron-containing nitride double-layer sputtering coating After the conversion coating is completed and dried, the workpiece is transferred to a vacuum sputtering chamber for routine ion cleaning to remove surface contaminants, followed by the sequential deposition of a double-layer sputtered coating: Step 3.1: Deposition of AlTiB(C)N ultrahard substrate Boron-containing nitride composite targets (TiAlBN or CrAlBN, purity ≥99.5%, density ≥5.0 g / cm³, grain size <50 μm) or TiAlN alloy targets (Ti:Al atomic ratio 1:1 to 2:1, purity ≥99.5%) are used in conjunction with reactive sputtering. During reactive sputtering, a boron-containing reactive gas (diborane B₂H₆, purity ≥99.5%, or boron trichloride BCl₃, purity ≥99.0%) is introduced, with the gas flow rate controlled at 5-20 sccm, so that the boron content in the deposited coating is controlled at 10-12 atomic percentages.

[0057] Safety precautions: B2H6 is a highly toxic and flammable gas, and BCl3 is a corrosive gas. Operation must be carried out in a sealed vacuum sputtering chamber equipped with a toxic gas leak detection and alarm system. Tail gas is neutralized using an alkaline scrubbing tower (0.1M NaOH solution). Operators must wear respirators and corrosion-resistant gloves. Simultaneously, a small amount of carbon-containing gas (methane CH4, purity ≥99.5%, flow rate 1-5 sccm, or propane C3H8, purity ≥99.0%, flow rate 1-3 sccm) is introduced to introduce a small amount of carbon (carbon content controlled at 2-5 atomic percentages) to improve coating toughness.

[0058] The deposition process employs a mid-frequency pulsed sputtering mode (frequency 20-350kHz), a target power density of 4-8W / cm², a substrate bias of -80V to -150V, and a deposition temperature of 300-400℃. The introduction of boron forms a dense amorphous structure and a hard BN phase, significantly improving the coating hardness. A deposition thickness of 3-4μm yields an AlTiB(C)N ultrahard underlayer with a hardness exceeding HV4800.

[0059] It should be noted that: AlTiB(C)N: The main elements are Al, Ti, B, and N, while carbon (C) is an optional additive element. A small amount of carbon element is introduced by simultaneously passing in a small amount of carbon-containing gas (methane CH4 or propane C3H8) (the carbon content is controlled at 2-5 atomic percentages) to improve the toughness of the coating. Parentheses indicate optional or minor additions of elements. AlTiB(C)N indicates that it can be either AlTiBN or AlTiBCN. This notation accurately covers the two possible composition ranges. The content of Al, Ti, B, C and N elements in AlTiB(C)N should be 20-30%, 25-35%, 10-12%, 2-5%, and 25-35% (atomic percentage), respectively.

[0060] Step 3.2: AlCrNO corrosion-resistant surface layer deposition Aluminum-chromium alloy targets (Al:Cr atomic ratio 1:1 to 2:1, purity ≥99.5%, density ≥4.5 g / cm³, grain size <100 μm) were used for reactive sputtering in a nitrogen-oxygen mixed reaction gas. High-purity nitrogen (N₂, purity ≥99.999%, flow rate 20-40 sccm) and high-purity oxygen (O₂, purity ≥99.99%, flow rate 5-10 sccm) were introduced, with the nitrogen-oxygen volume ratio controlled at 4:1 to 5:1, and the reaction chamber pressure maintained at 0.3-0.8 Pa. The incorporation of oxygen resulted in the formation of dense Al₂O₃ and Cr₂O₃ oxide phases in the layer, with the oxide phase content controlled at 20-40 vol%, exhibiting excellent chemical stability.

[0061] The process employs DC magnetron sputtering with a target power density of 3-6 W / cm², a substrate bias of -50V to -100V, and a deposition temperature of 300-350℃. A deposition thickness of 1-2 μm is achieved, forming an AlCrNO corrosion-resistant surface layer that effectively seals the columnar grain gaps and micropores in the underlying substrate. The continuity of aluminum in both layers ensures strong interfacial bonding, resulting in a dual-functional composite coating that combines ultra-high hardness with primary corrosion resistance.

[0062] Step 4: Sol-gel sealing treatment After sputtering coating, the workpiece is cooled to room temperature in a vacuum and then transferred in a dry air environment for sol-gel sealing. The transfer process is completed within 30 minutes to avoid surface oxidation. This step applies sol-gel technology to the grain boundary sealing of the PVD coating, fundamentally solving the problem of grain boundary penetration in columnar crystals.

[0063] Step 4.1: Preparation of silicate-aluminate composite sol A composite sol was prepared by hydrolysis-condensation reaction using tetraethyl orthosilicate (TEOS, Si(OC2H5)4, analytical grade, purity ≥99.0%, molecular weight 208.33) and aluminum isopropoxide (Al(OC3H7)3, chemically pure, purity ≥98.0%, molecular weight 204.25) as precursors.

[0064] Specific procedure: Mix TEOS (10-20 ml, approximately 0.045-0.090 mol) with aluminum isopropoxide (molar ratio controlled at 3:1 to 5:1, i.e., 0.009-0.030 mol) in anhydrous ethanol solvent (C2H5OH, analytical grade, purity ≥99.7%, 50-100 ml). While stirring, slowly add deionized water (resistivity ≥18 MΩ·cm, water to precursor molar ratio 4:1 to 6:1) and 0.1 M hydrochloric acid catalyst (HCl, analytical grade, concentration 36-38%, diluted with deionized water, 1-3 ml, to adjust pH to 4.0-5.0). Maintain a stirring speed of 200-400 rpm and react at room temperature (20-25℃) for 2-4 hours until a transparent, colorless silicate-aluminate composite sol is formed, with a viscosity controlled at 1-10 mPa·s (measured using a rotational viscometer at 60 rpm).

[0065] Sol storage and aging conditions: The prepared sol should be stored in a sealed container at 4-8°C for no more than 72 hours. Before use, it should be equilibrated at room temperature for 30 minutes, and the viscosity should be re-measured to ensure it is within the specified range. The sol will undergo a slow condensation reaction (aging) during storage. Proper aging is beneficial to improving film quality, but excessive aging will lead to sol gelation failure.

[0066] Step 4.2: Dip and lift coating The sputter-coated serrations are immersed in the composite sol at a constant speed (1-5 mm / s) and held for 10-20 seconds to allow the sol to fully wet the surface and penetrate the columnar grain boundaries and micropores of the AlCrNO layer. Then, they are pulled out of the liquid at the same speed. During the pulling process, the sol forms a uniform liquid film on the workpiece surface.

[0067] Step 4.3: Low-temperature curing The workpiece coated with sol is placed in an oven and dried at 150-200℃ for 1-2 hours. During the curing process, the sol undergoes further condensation reaction, and moisture and organic solvents evaporate, eventually solidifying to form a 0.2-0.3μm thick SiO2-Al2O3 composite oxide gel layer.

[0068] The key working principle of this gel layer: (1) The low viscosity (usually 1-10 mPa·s) and good wettability of the sol enable it to penetrate into the columnar grain boundaries (usually a few nanometers to tens of nanometers wide) and micropores of AlCrNO, and block these penetration channels after solidification. (2) The SiO2-Al2O3 composite oxide has an amorphous structure, no grain boundaries, and uniform composition, which eliminates the micro-galvanic corrosion phenomenon of multiphase ceramic layers. (3) The gel layer has extremely high chemical stability and excellent corrosion resistance to various media such as acids, alkalis and salts.

[0069] Step 5: Chemical Vapor Infiltration (CVI) Enhancement Treatment This step involves introducing chemical vapor infiltration technology to further strengthen the sol-gel layer, and using nanofillers to further improve the density, forming an ultra-dense, non-porous oxide sealing layer.

[0070] The workpiece with the coated and cured sol-gel layer is transferred to a low-pressure chemical vapor deposition (CVD) furnace for CVI strengthening treatment. The reaction conditions are strictly controlled: temperature 350-400℃, pressure 100-1000 Pa, with a silicon-containing organic gas introduced as a precursor. This temperature range matches the deposition temperature of the preceding coatings, ensuring that the SiO2-Al2O3 gel layer and the AlTiB(C)N and AlCrNO coatings maintain structural stability at this temperature, guaranteeing that the interfacial bonding between layers remains unaffected.

[0071] Precursor selection and reaction principle Methyltrichlorosilane or tetramethylsilane is selected as the precursor. Safety precautions: MTS is a corrosive liquid that produces HCl upon contact with water; TMS is a flammable gas. Operation must be carried out in a well-ventilated environment, equipped with corrosive gas detectors. Exhaust gas is treated in an alkaline scrubbing tower before discharge to prevent HCl corrosion of equipment and injury to personnel. MTS undergoes a pyrolysis reaction at the reaction temperature (350-400℃): CH3SiCl3 → SiO2 x + HCl + organic byproducts (where x = 1.5-2.0); TMS undergoes pyrolysis: Si(CH3)4 → SiC + 2H2 + CH4. The precursor flow rate is precisely controlled by a mass flow controller (MFC), and the carrier gas is high-purity argon (Ar, purity ≥ 99.999%).

[0072] Organosilicon vapor undergoes pyrolysis on the surface of the gel layer and in the residual pores (typically 1-10 nm in diameter) inside, depositing SiOx (silicon oxide) or SiC (silicon carbide) nanoparticles. These nanoparticles (2-5 nm in diameter) fill the residual pores of the gel layer, further densifying it.

[0073] Process parameter control The gas flow rate is controlled at 10-50 sccm, and the processing time is 30-60 minutes. The deposited SiOx / SiC filler accounts for approximately 10-20% of the gel layer volume. During the reaction, the precursor vapor first reacts on the surface of the gel layer, and then gradually diffuses and reacts into the internal pores, achieving layer-by-layer filling from the outside to the inside.

[0074] After CVI reinforcement, the gel layer density approaches 100%, and the permeability decreases by 2-3 orders of magnitude (from 10). -12 cm² / s decreased to 10 -15 (cm² / s), while high-temperature treatment promotes further solidification and partial crystallization of the gel layer, significantly improving mechanical strength and wear resistance.

[0075] Step 6: Low-temperature plasma polymerization sealing treatment After CVI treatment, the workpiece is cooled to below 100°C in an inert atmosphere and then transferred to a plasma-enhanced chemical vapor deposition (PECVD) apparatus for final sealing. The transfer process is completed within 1 hour to avoid surface contamination. A conventional plasma polymerization process is used, with hexamethyldisiloxane (HMDSO, ((CH3)3Si)2O, electronic grade, purity ≥99.5%, molecular weight 162.38, boiling point 100.5°C) as the precursor. The flow rate is controlled at 10-30 sccm using a mass flow controller, and high-purity argon (Ar, purity ≥99.999%, flow rate 50-100 sccm) is used as the carrier gas. Deposition conditions: substrate temperature 80-120℃ (measured with a thermocouple), RF power 100-300W (frequency 13.56MHz, power matching impedance <50Ω), reaction pressure 10-100Pa (measured with a capacitive thin-film vacuum gauge), deposition rate controlled at 50-200nm / min (monitored in real time with an ellipsometer).

[0076] Plasma-excited active free radicals initiate the polymerization reaction of HMDSO monomers, forming a 0.3-0.5 μm thick diamond-like silicon-oxygen-carbon polymer film (SiOC) on the workpiece surface. This film is dense and non-porous, completely sealing all microscopic defects on the coating surface, forming a continuous, non-porous final protective layer. The low-temperature polymerization process does not affect the structure and properties of the preceding coatings.

[0077] Physicochemical properties of SiOC thin films: (1) Hydrophobicity: The water contact angle is 95-110° (measured by a contact angle measuring instrument, with a droplet volume of 2μL), and the surface free energy is 20-25 mJ / m², effectively blocking water-based corrosive media; (2) Chemical stability: It is chemically stable in the pH range of 1-13 and is resistant to acid and alkali corrosion; (3) Mechanical properties: The elastic modulus is 15-25 GPa, the hardness is HV800-1200, and it has a certain degree of flexibility; (4) Thermal stability: Decomposition temperature > 400℃, structurally stable within the operating temperature range; (5) Electrical insulation: Volume resistivity > 10 14 Ω·cm, breakdown strength >5×10 6It has a voltage of V / m and excellent electrical insulation properties.

[0078] After processing and cooling, a high-hardness, corrosion-resistant serrated coating with a six-fold synergistic protective structure is obtained. From the inside out, the coating consists of: a multi-element corrosion inhibitor composite conversion film (1.5-3 μm thick, chemical passivation barrier) → an AlTiB(C)N ultra-hard underlayer (3-4 μm thick, ultra-hard load-bearing) → an AlCrNO corrosion-resistant surface layer (1-2 μm thick, oxide sealing) → a SiO2-Al2O3 gel layer (0.2-0.3 μm thick, grain boundary sealing) → a CVI reinforcement layer (nanoscale filling, densification) → a SiOC polymer film (0.3-0.5 μm thick, final sealing), forming a comprehensive, multi-layered synergistic protective structure with a total thickness of approximately 6-10 μm.

[0079] Experimental verification Experiment 1: Verification Experiment of Ultra-High Hardness Performance 1. Experimental Objective The ultra-high hardness performance of the six-fold synergistic protective structure coating of the present invention was verified, demonstrating that the boron-containing nitride composite coating has a significant hardness improvement effect compared with the traditional nitride coating.

[0080] 2. Preparation of experimental samples Five different serrated samples were prepared, each with a size of 20mm × 10mm × 2mm: (1) Blank control group: No. 45 steel substrate, without any surface treatment; (2) Traditional TiN coating group: Traditional TiN sputtering coating is used, with a thickness of 2-3 μm; (3) Traditional CrN coating group: Traditional CrN sputtering coating is used, with a thickness of 2-3 μm; (4) AlTiB(C)N monolayer group: only AlTiB(C)N layers are deposited, with a thickness of 3-4 μm; (5) Complete embodiment group: prepared according to the method of the present invention, having a complete six-fold synergistic protection structure.

[0081] 3. Experimental conditions Hardness testing equipment: Vickers hardness tester (HV-1000 type) Test load: 0.98N (HV1) Hold time: 15 seconds Test environment: room temperature 20±2℃, relative humidity 45-65% Number of test points: 9 different locations are tested for each sample, and the average value is taken.

[0082] 4. Experimental Procedure (1) Sample pretreatment: Ultrasonic cleaning with acetone for 10 minutes to remove surface contaminants, and then air drying; (2) Hardness tester calibration: Calibrate using a standard hardness block to ensure test accuracy; (3) Sample fixation: Fix the sample horizontally on the hardness tester test platform; (4) Selected test points: Select 9 test points evenly on the sample surface, avoiding edges and defect areas; (5) Data recording: Record the hardness value of each test point, and calculate the average value and standard deviation; (6) Data processing: Statistical analysis of the hardness distribution and significance differences of each group of samples.

[0083] 5. Experimental Results Table 1. Hardness test results of samples with different coatings

[0084] Figure 1 The hardness comparison of samples with different coatings is shown.

[0085] 6. Analysis and Summary Experimental results show that the six-fold synergistic protective structure coating of the present invention exhibits significantly high hardness performance: (1) Hardness breakthrough: The hardness of the complete example group reached HV4950±140, which is 1667.9% higher than that of the 45 steel substrate, 120.0% higher than that of the traditional TiN coating, and 127.1% higher than that of the traditional CrN coating.

[0086] (2) Boron-containing effect: The hardness of AlTiB(C)N monolayer has reached HV4820, which exceeds the HV4800 standard required above, proving that the introduction of boron plays a key role in improving hardness. The hard BN phase and dense amorphous structure formed are the main sources of ultra-high hardness.

[0087] (3) Synergistic effect: The hardness of the complete example group was further improved by 2.7% compared with the AlTiB(C)N monolayer group, indicating that the other layers (conversion film, AlCrNO layer, gel layer, etc.) in the six-fold synergistic protection structure have a synergistic contribution to the overall hardness.

[0088] (4) Excellent stability: The standard deviation (138.7) of the complete example group is relatively small, indicating that the coating hardness is uniformly distributed and the process stability is good.

[0089] Experiment 2: Verification Experiment of Broad-Spectrum Corrosion Resistance 1. Experimental Objective The study verified the broad-spectrum protective effect of the multi-element corrosion inhibitor composite conversion film of the present invention in various corrosive media, and proved that compared with the single conversion film treatment method, the present invention has a significant improvement in corrosion resistance under different corrosive environments such as acid, alkaline, salt spray, and sulfide.

[0090] 2. Preparation of experimental samples Four sets of control samples were prepared, each measuring 30mm × 20mm × 3mm: (1) Blank control group: No. 45 steel matrix, only degreasing pretreatment was performed; (2) Traditional conversion membrane group: The traditional chromate-phosphate bilayer conversion membrane is used for treatment; (3) Double-layer coating group: AlTiB(C)N+AlCrNO double layer is deposited on the basis of traditional conversion film; (4) Complete embodiment group: prepared according to the method of the present invention, having a complete six-fold synergistic protection structure; Fifteen samples were prepared for each group and used for testing five different corrosive media. Three parallel samples were tested for each media.

[0091] 3. Experimental conditions Corrosive media settings: (1) Acidic medium: dilute hydrochloric acid solution, pH=3.0±0.2; (2) Alkaline medium: sodium hydroxide solution, pH=11.0±0.2; (3) Neutral salt spray: 3.5% NaCl solution, pH=6.8±0.2 (standard salt spray test conditions); (4) Sulfide medium: 0.1% Na2S solution, pH=7.0±0.2; (5) Oxidizing medium: 3% H2O2 solution, pH=7.0±0.2; Test temperature: 25±2℃; Immersion time: 500 hours; Sample surface area: 12 cm².

[0092] Experimental Time Setting Instructions: This experiment uses a 500-hour immersion time, primarily to verify the relative protective performance differences of different protective structures in various corrosive media. Verification of long-term salt spray testing (1600-2000 hours) will be conducted in subsequent product acceptance tests. This experiment focuses on comparative analysis and mechanism verification.

[0093] 4. Experimental Procedure (1) Sample pretreatment: Acetone ultrasonic cleaning, drying and weighing, and recording the initial mass m0; (2) Preparation of corrosive solutions: Prepare various corrosive media according to the specified concentration, and calibrate the acidity and alkalinity with a pH meter; (3) Immersion test: Immerse the sample completely in the corrosive solution, cover and seal to prevent evaporation; (4) Regular observation: Observe and photograph the changes on the sample surface every 24 hours; (5) End of test: Remove the sample, rinse with distilled water, clean with acetone, dry and weigh m 1； (6) Corrosion weight loss calculation: Corrosion weight loss rate = (m0-m1) / m0×100%.

[0094] 5. Experimental Results Table 2. Weight loss rate test results (%) of different samples in various corrosive media

[0095] Figure 2 The comparison of weight loss rates in different corrosive media is shown. Figure 3 A radar chart showing broad-spectrum corrosion resistance was displayed.

[0096] 6. Analysis and Summary Experimental results fully demonstrate the significant advantages of this invention in terms of broad-spectrum corrosion resistance: (1) Overall corrosion resistance improvement: The average weight loss rate of the complete example group in 5 different corrosive media was only 0.54%, which was 91.7% lower than the blank control group, 85.5% lower than the traditional conversion film group, and 71.3% lower than the double-layer coating group.

[0097] (2) Breakthrough in acidic media: In the most challenging acidic media, the weight loss rate of the complete example group was only 0.42%, which is 95.2% higher than the blank group and 86.9% higher than the traditional conversion membrane group, effectively solving the problem of rapid failure of traditional methods in strong acid environment.

[0098] (3) Significant protection against sulfides: It is particularly outstanding in sulfide media. The weight loss rate of the complete example group was 0.89%, which is 92.8% higher than that of the blank group, proving the special protective effect of molybdenum and tungsten elements in the multi-element corrosion inhibitor on sulfide corrosion.

[0099] (4) Excellent broad-spectrum uniformity: The weight loss rate of the complete example group in various corrosive media remained below 1%, with a small standard deviation, indicating that there was no bottleneck effect and truly achieved broad-spectrum corrosion resistance.

[0100] (5) Synergistic protection verification: Each additional protective measure significantly improves corrosion resistance, and the six-fold synergistic protection structure ultimately achieves an exponential enhancement of protection.

[0101] Experiment 3: Electrochemical Verification Experiment of Synergistic Protection Effect 1. Experimental Objective Electrochemical impedance spectroscopy (EIS) was used to quantitatively verify the synergistic enhancement effect of the six-fold synergistic protection structure of this invention, proving that the overall protection performance far exceeds the simple superposition of the individual components, and revealing the electrochemical mechanism of synergistic protection.

[0102] 2. Preparation of experimental samples Six sets of control samples were prepared, each with a size of 15mm × 15mm × 3mm and a working area of ​​1 cm². (1) Matrix group: No. 45 steel matrix, degreasing treatment only; (2) Conversion film group: Contains only multi-element corrosion inhibitor composite conversion film; (3) Substrate: Conversion film + AlTiB(C)N substrate; (4) Bilayer group: conversion membrane + AlTiB(C)N + AlCrNO bilayer; (5) Four-layer group: the above structure + sol-gel layer + CVI reinforcement; (6) Complete Group: Complete six-fold collaborative protection structure; Five parallel samples were prepared for each group to ensure data reliability.

[0103] 3. Experimental conditions Electrochemical testing system: three-electrode system; Working electrode: The sample to be tested (1 cm² working area); Reference electrode: Saturated calomel electrode (SCE); Auxiliary electrode: Platinum electrode; Electrolyte: 3.5% NaCl solution, pH=7.0±0.1; Test temperature: 25±1℃; Test frequency range: 100 kHz - 0.01 Hz; Disturbance voltage: 10 mV (rms); Stabilization time: Tests will begin 30 minutes after the open circuit potential has stabilized.

[0104] 4. Experimental Procedure (1) Sample pretreatment: Encapsulate with epoxy resin, leaving only 1 cm² of the working surface exposed, clean with acetone and dry; (2) Electrolytic cell assembly: The sample is used as the working electrode and installed in a three-electrode electrolytic cell; (3) Open circuit potential test: Record the change in open circuit potential within 30 minutes to ensure system stability; (4) EIS test: Electrochemical impedance spectroscopy test is performed at open circuit potential; (5) Data acquisition: Collect 10 data points at each frequency point and take the average value; (6) Data fitting: The impedance spectrum is fitted using an equivalent circuit model, and the electrical parameters are calculated; (7) Reproducibility verification: Five parallel samples were tested for each group of samples, and the mean and standard deviation were calculated.

[0105] 5. Experimental Results Table 3 Electrochemical impedance spectroscopy results for different protective structures

[0106] Theoretical superposition comparison value: The theoretical value of simply adding the impedances of each component is: 1.24 × 10⁻⁶ 4 + 4.67×10 4 + 1.28×10 5 + 2.95×10 5 + 7.85×10 5 = 8.16×10 5 Ω·cm²; Actual complete set test value: 1.86 × 10 6 Ω·cm²; Synergistic enhancement factor: 1.86 × 10 6 ÷ 8.16×10 5 = 2.28 times.

[0107] Figure 4 It demonstrates the gradual improvement in protective performance; Figure 5 It demonstrates the layer-by-layer enhancement effect of collaborative protection.

[0108] 6. Analysis and Summary Electrochemical impedance spectroscopy results strongly demonstrate the significant synergistic enhancement effect of the six-fold synergistic protection structure of this invention: (1) Exponential improvement in protection performance: The impedance modulus of the complete group reaches 1.86×10 6 The corrosion current density (Ω·cm²) is increased by 150 times compared to the matrix, while the corrosion current density is reduced to 3.25 × 10⁻⁶. -8 A / cm², a reduction of 99.9%, fully meeting the requirement of <5×10⁻⁶ in the previous text. -8 A / cm² standard.

[0109] (2) Significant synergistic enhancement effect: The actual measured impedance value (1.86×10) 6 The value of Ω·cm² is greater than the theoretical value of the simple superposition of the components (8.16×10). 5 The Ω·cm² value is 2.28 times higher, which fully demonstrates the existence of the synergistic enhancement mechanism.

[0110] (3) The layer-by-layer increasing law is clear: with each additional layer of protective structure, the impedance value shows a non-linear increase, from 3.8 times that of the conversion membrane group to 150 times that of the complete group, reflecting the cumulative effect of synergistic protection.

[0111] (4) Excellent electrochemical stability: The Nyquist plot shows that the complete group has the largest capacitive arc diameter, indicating that the charge transfer resistance is extremely large and the corrosion reaction is effectively suppressed.

[0112] (5) Synergistic and complementary protection mechanisms: multi-component corrosion inhibitors provide chemical passivation, boron-nitrides provide physical barriers, sol-gel seals micro-defects, CVI strengthens and increases density, and polymer layer forms final seal. The various mechanisms are synergistic and complementary, and the protection effect is far greater than that of a single mechanism.

[0113] 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 method for high-hardness serrated sputtering coating, characterized in that, Includes the following steps: Step 1: Treatment with multi-component corrosion inhibitor composite conversion film: A first conversion film containing molybdate and tungstate and a second composite phosphate conversion film containing rare earth elements and organophosphonic acid are sequentially formed on the surface of the serrated substrate. Step 2: Boron-nitride double-layer sputtering coating: An AlTiB(C)N ultrahard underlayer and an AlCrNO corrosion-resistant surface layer were sequentially deposited using a sputtering process. Step 3: Sol-gel sealing treatment: The silicate-aluminate composite sol was impregnated and coated onto the AlCrNO corrosion-resistant surface layer, and a SiO2-Al2O3 composite oxide gel layer was formed by penetrating into the columnar grain boundaries and curing in situ. Step 4: Enhanced Chemical Vapor Infiltration Treatment A silicon-containing organic gas precursor is introduced to deposit SiO2 within the gel layer. x Alternatively, SiC nanoparticles can be used to fill and densify the pores. Step 5: Low-temperature plasma polymerization sealing treatment: HMDSO was used as a precursor for plasma polymerization to form a SiOC polymer film on the surface.

2. The method according to claim 1, characterized in that, The first conversion film is formed by the following steps: immersing the saw teeth in a modified chromate solution containing potassium dichromate, sodium molybdate and sodium tungstate, and treating it at 60-80°C for 10-15 minutes to form a 0.5-1 μm thick Cr-Mo-W composite oxide conversion film.

3. The method according to claim 1, characterized in that, The second layer of composite phosphate conversion membrane is formed by the following steps: the saw teeth treated with the first layer of conversion membrane are immersed in a modified phosphating solution containing zinc phosphate, manganese phosphate, cerium nitrate or lanthanum nitrate and hydroxyethylidene diphosphonic acid (HEDP), and treated at 80-95°C for 15-20 minutes to form a 1-2 μm thick composite phosphate conversion membrane containing rare earth elements and organophosphonic acids.

4. The method according to claim 1, characterized in that, The deposition parameters of the AlTiB(C)N ultrahard substrate are as follows: using a boron-containing nitride composite target or a TiAlN target combined with reactive sputtering, introducing a boron-containing reactive gas with a boron content of 10-12 atomic percentages, using a medium-frequency pulse sputtering mode, a substrate bias voltage of -80V to -150V, a deposition temperature of 300-400℃, and a thickness of 3-4μm.

5. The method according to claim 1, characterized in that, The deposition parameters of the AlCrNO corrosion-resistant surface layer are as follows: aluminum chromium alloy target is used for reactive sputtering in a nitrogen-oxygen mixed reactive gas, the nitrogen-oxygen volume ratio is controlled at 4:1 to 5:1, DC magnetron sputtering mode is used, the substrate bias voltage is -50V to -100V, the deposition temperature is 300-350℃, and the thickness is 1-2μm.

6. The method according to claim 1, characterized in that, The silicate-aluminate composite sol was prepared using tetraethyl orthosilicate (TEOS) and aluminum isopropoxide as precursors, with a molar ratio controlled between 3:1 and 5:

1. It was coated by dip-coating process and cured at 150-200℃ to form a 0.2-0.3 μm thick SiO2-Al2O3 composite oxide gel layer.

7. The method according to claim 1, characterized in that, The process conditions for the chemical vapor infiltration enhancement treatment are: temperature 350-400℃, pressure 100-1000 Pa, methyltrichlorosilane or tetramethylsilane as precursor, treatment time 30-60 minutes, and filler accounting for 10-20% of the gel layer volume.

8. The method according to claim 1, characterized in that, The process conditions for the low-temperature plasma polymerization sealing treatment are as follows: substrate temperature 80-120℃, radio frequency power 100-300W, reaction pressure 10-100 Pa, deposition rate 50-200nm / min, forming a SiOC polymer film with a thickness of 0.3-0.5μm.

9. The method according to claim 1, characterized in that, The coating obtained by the method consists of, from the inside out: a multi-element corrosion inhibitor composite conversion film, an AlTiB(C)N superhard underlayer, an AlCrNO corrosion-resistant surface layer, a SiO2-Al2O3 gel layer, a CVI reinforcement layer, and a SiOC polymer film, with a total thickness of 6-10 μm.

10. The method according to claim 1, characterized in that, The coating obtained by the method has a surface hardness of HV4500-5000, and shows no corrosion marks after 1600-2000 hours of neutral salt spray testing. Its service life is extended by 4-6 times compared to uncoated serrations.

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