A high-insulation coating on the surface of a titanium alloy and a preparation method thereof

Abstract

The present invention belongs to the technical field of light alloy surface treatment, and particularly relates to a high-insulation coating on the surface of titanium alloy and a preparation method thereof. The coating is a composite coating of a plasma oxidation insulating ceramic layer - an organic lubricating film. The micro-plasma oxidation electrolyte for forming the plasma oxidation insulating ceramic layer comprises the following components: sodium silicate 5-18 g / L, sodium hydroxide 1-5 g / L, sodium citrate 2-5 g / L, high-insulation nanoparticles 5-10 g / L, anionic electrolyte 0.05-0.2 g / L, and the balance is water; the organic lubricating spraying liquid for forming the organic lubricating film comprises, by mass percentage, 60-80% of organic resin, 5-20% of lubricant, and 15-20% of spraying agent. The present invention can improve the comprehensive performance of insulation and wear resistance of titanium alloy, and meet the protection use requirements of titanium alloy products in harsh marine environments.

Description

Technical Field

[0001] The present invention belongs to the technical field of light alloy surface treatment, and particularly relates to a high-insulation coating on the surface of titanium alloy and a preparation method thereof. Background Art

[0002] Titanium and its alloys, as very important light metal materials, have the characteristics of low density, high specific strength, excellent corrosion resistance, good fatigue resistance, high heat resistance, etc., and are widely used in various fields. Compared with other light alloys, they have better corrosion resistance in harsh environments. Up to now, many countries in the world have realized the importance of titanium alloy materials and have successively carried out research and development on them. They have a wide range of applications in many fields such as aerospace, petrochemical industry, shipbuilding, weaponry, and medicine. However, when titanium alloys are in service in harsh environments such as the ocean, there are cases of dissimilar metal connections between titanium alloys and other metal materials of different materials. Due to the large potential difference between different metals, the phenomenon of galvanic corrosion is extremely likely to occur, accelerating the corrosion of the metal with a lower potential. Because the electrode potential of titanium alloy is relatively high, in the actual service process, it causes galvanic corrosion of other light alloys (such as steel, copper, aluminum, etc.) connected to it, thereby affecting the service performance and life of the equipment.

[0003] The existing main methods for solving the galvanic corrosion of titanium alloys are generally to prepare an insulating coating or an oxide film layer on the surface of titanium alloys, and isolate and protect the low-potential alloy through the insulating performance of the film layer to avoid galvanic corrosion. An organic coating is used to form an insulating paint film on the surface of titanium alloy by spraying, brushing, or rolling. However, due to the bonding strength between the organic coating and the metal and the wear resistance not meeting the service requirements in harsh environments, and some titanium alloy pipes often serve at high temperatures, traditional organic coatings are prone to problems such as blistering and aging. The micro-arc oxidation technology is a new type of green and environmentally friendly material protection technology, which can form a ceramic oxide film layer mainly composed of matrix oxides on the surface of titanium alloys. It has good wear resistance and insulation performance, thus greatly improving its application environment. However, since the main component of the oxide film formed by the traditional micro-arc oxidation technology is titanium dioxide, and titanium dioxide itself is a semiconductor, it is prone to failure in harsh marine environments, and the insulation performance cannot meet the requirements of its resistance to galvanic corrosion. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a high-insulation coating on the surface of titanium alloy and a preparation method thereof, which improve the comprehensive performance of insulation and wear resistance of titanium alloy and meet the protection and use requirements of titanium alloy products in harsh marine environments.

[0005] The present invention is implemented as follows: A high-insulation coating on the surface of a titanium alloy, which is a composite coating of a plasma oxidation insulating ceramic layer - an organic lubricating film. The micro-plasma oxidation electrolyte for forming the plasma oxidation insulating ceramic layer includes the following components: sodium silicate 5 - 18 g / L, sodium hydroxide 1 - 5 g / L, sodium citrate 2 - 5 g / L, high-insulation nanoparticles 5 - 10 g / L, anionic electrolyte 0.05 - 0.2 g / L, and the rest is water; The organic lubricating spraying liquid for forming the organic lubricating film, by mass percentage, includes 60 - 80% of organic resin, 5 - 20% of lubricant, and 15 - 20% of spraying agent.

[0006] Preferably, the high-insulation nanoparticles are one or more of alumina, magnesia, and zirconia.

[0007] Preferably, the anionic electrolyte is one or more of sodium polyacrylate, polyvinyl alcohol, sodium polystyrene sulfonate, polyacrylamide, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, and sodium fatty alcohol polyoxyethylene ether sulfate.

[0008] Preferably, the organic resin is epoxy resin or Teflon resin, the lubricant is one or more of molybdenum disulfide, white graphite, and talcum powder, and the spraying agent is xylene.

[0009] The present invention also provides a preparation method for the high-insulation coating on the surface of a titanium alloy. Based on the above-mentioned high-insulation coating on the surface of a titanium alloy, the preparation method includes the following steps:

[0010] Step 1: Pretreatment of the surface of the titanium alloy;

[0011] Step 2: Preparation of the micro-plasma oxidation electrolyte: Add high-insulation nanoparticles and anionic electrolyte to the basic electrolyte formed by sodium silicate, sodium hydroxide, sodium citrate, and water, and stir to make the anionic electrolyte adsorb on the surface of the high-insulation nanoparticles to form anionic groups;

[0012] Step 3: Place the titanium alloy into the micro-plasma oxidation electrolyte, and perform micro-plasma spark discharge oxidation on the titanium alloy in a high-voltage pulse mode to form a plasma oxidation insulating ceramic layer on the surface of the titanium alloy;

[0013] Step 4: Spray the organic lubricating spraying liquid on the surface of the plasma oxidation insulating ceramic layer, and dry it to form an organic lubricating film, and finally form a composite coating of a plasma oxidation insulating ceramic layer - an organic lubricating film on the surface of the titanium alloy.

[0014] Preferably, in the step 3, the temperature of the micro-plasma oxidation electrolyte is 15 - 50 °C, and the specific conditions of the high-voltage pulse are: pulse frequency 100 - 1000 Hz, pulse voltage 250 - 400 V, current density 1 - 4 A / dm2 The oxidation time is 10 to 60 minutes.

[0015] Preferably, the plasma oxidation insulating ceramic layer formed in step 3 is a porous insulating ceramic oxide film rich in nanoparticles, with a thickness of 5 to 30 μm, a porosity of 20 to 30%, and a pore diameter of 5 to 8 μm.

[0016] Preferably, in step 4, the specific spraying conditions are as follows: the particle size of the organic resin powder is 200 to 400 mesh, the spraying temperature is 20 to 35 °C, the spraying pressure is 1.2 to 2.8 MPa, the spraying distance is 10 to 40 mm, and the drying conditions after spraying are: the drying temperature is 60 to 120 °C, and the drying time is 30 minutes.

[0017] Preferably, in step 4, the total thickness of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating is 50 to 80 μm.

[0018] Preferably, in step 4, before spraying the organic lubricating spraying liquid on the surface of the plasma oxidation insulating ceramic layer, the plasma oxidation insulating ceramic layer is first etched. The specific etching conditions are as follows: in hydrofluoric acid with a mass concentration of 5 to 10%, the plasma oxidation insulating ceramic layer is etched at room temperature for 2 to 5 s, taken out and immediately washed with clear water for 2 to 5 min, and then washed with deionized water for 1 to 3 min.

[0019] Compared with the prior art, the advantages of the present invention are as follows:

[0020] The present invention realizes the insulation and wear resistance of the titanium alloy substrate by preparing a composite protective coating on the surface of the titanium alloy. First, high-insulation nanoparticles and anionic electrolytes are added to the electrolyte, and the anionic electrolyte is adsorbed onto the surface of the nanoparticles to form anionic groups by stirring. Then, plasma micro-arc oxidation is carried out on the surface of the titanium alloy substrate to form a micro-arc oxidation porous ceramic layer. Finally, the coating is subjected to a composite treatment with a spraying agent to form a composite coating with high insulation and high wear resistance. The micro-arc oxidation composite protective coating prepared on the surface of the titanium alloy by the method of the present invention has the advantages of high insulation and high wear resistance, and can meet the high-strength protection requirements of titanium alloy in harsh environments such as the ocean.

[0021] 2. The present invention is applicable to titanium alloys of the TC, TA, etc. series, such as TC4, TC11, TA0, TA1, etc. Specific Embodiments

[0022] The following combines specific implementation schemes to further explain and illustrate the present invention, but does not limit the protection scope of the present invention.

[0023] Example 1

[0024] 1. Material preparation: After the pretreatment of TC4 titanium alloy, namely cutting, grinding, and polishing, degreasing is carried out by ultrasonic cleaning in acetone solution.

[0025] 2. Preparation of plasma oxidation insulating ceramic layer:

[0026] (1) Composition of micro-plasma oxidation electrolyte: Sodium silicate 10 g / L, sodium hydroxide 5 g / L, sodium citrate 5 g / L, nano-aluminum oxide particles 5 g / L, polyvinyl alcohol 0.1 g / L, aqueous solution of sodium dodecylbenzenesulfonate 0.1 g / L, and the rest is water, which is dissolved by stirring.

[0027] (2) Preparation process: The titanium alloy specimen (as the anode) is placed in the micro-plasma oxidation electrolyte, and micro-plasma spark discharge oxidation is carried out on the specimen by using a high-voltage pulse method. The pulse frequency is 500 Hz, the pulse voltage is 300 V, and the current density is 1 A / dm 2 , the oxidation time is 60 min, and the thickness of the obtained plasma oxidation insulating ceramic layer is 12 - 15 μm. This plasma oxidation insulating ceramic layer is a porous insulating ceramic film rich in nano-particles, with a porosity of 20 - 30% and a pore diameter of 5 - 8 μm.

[0028] 3. Preparation of organic lubricating film:

[0029] First, the plasma oxidation insulating ceramic layer is etched. The specific etching conditions are: in 5% hydrofluoric acid by mass concentration, the plasma oxidation insulating ceramic layer is etched at room temperature for 2 s, taken out and immediately washed with clear water for 2 min, and then washed with deionized water for 1 min.

[0030] Then, an organic lubricating film is compounded on the surface of the plasma oxidation insulating ceramic layer. Composition of the spraying solution: Teflon resin 60%, lubricant molybdenum disulfide, mass fraction 20%, spraying agent xylene, mass fraction 20%; Specific spraying conditions: The particle size of the organic resin powder is 200 mesh, the spraying temperature is set at 25 °C, the pressure is 1.5 MPa, the spraying distance is 30 - 40 mm, the drying temperature is 120 °C, and the drying time is 30 min. The total thickness of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating is 50 μm.

[0031] The bonding strength of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating obtained from this example is ≥10 MPa, the maximum surface Vickers hardness can reach 400 HV, the neutral salt spray test resistance reaches more than 2000 h, wear resistance: wear coefficient (WI) <0.3, and the dry insulation point resistance can reach 100 MΩ and above under a DC voltage of 1000 V.

[0032] Example 2

[0033] 1. Material preparation: Pre-treat TC11 titanium alloy, that is, after cutting, grinding, and polishing, degrease it by ultrasonic cleaning in an alkaline cleaning solution.

[0034] 2. Preparation of plasma oxidation insulating ceramic layer:

[0035] (1) Composition of micro-plasma oxidation electrolyte: Sodium silicate 18 g / L, sodium hydroxide 1 g / L, sodium citrate 2 g / L, nano-zirconia particles 10 g / L, polyacrylamide 0.03 g / L, aqueous solution of sodium dodecyl sulfate 0.02 g / L. Dissolve by stirring, and the rest is water.

[0036] (2) Preparation process: Place the titanium alloy specimen (as the anode) in the electrolyte and conduct micro-plasma spark discharge oxidation on the specimen in a high-voltage pulse mode. The pulse frequency is 100 Hz, the pulse voltage is 350 V, and the current density is 2.5 A / dm 2 , the oxidation time is 30 min, and the thickness of the obtained plasma oxidation insulating ceramic layer is 20 - 30 μm. This plasma oxidation insulating ceramic layer is a porous insulating ceramic film rich in nano-particles, with a porosity of 25 - 30% and a pore diameter of 5 - 8 μm.

[0037] 3. Preparation of organic lubricating film:

[0038] First, etch the plasma oxidation insulating ceramic layer. The specific etching conditions are: Immerse the plasma oxidation insulating ceramic layer in 10% (mass concentration) hydrofluoric acid at room temperature for 5 s, take it out and immediately wash it with clean water for 5 min, and then wash it with deionized water for 3 min.

[0039] Then, composite an organic lubricating film on the surface of the plasma oxidation insulating ceramic layer. Composition of the spraying solution: Epoxy resin 80%, lubricant is white graphite with a mass fraction of 5%, and spraying agent is xylene with a mass fraction of 15%; Specific spraying conditions: The particle size of the organic resin powder is 300 mesh, the spraying temperature is set at 20 °C, the pressure is 1.2 MPa, the spraying distance is 10 - 20 mm, the drying temperature is 60 °C, and the drying time is 30 min. The total thickness of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating is 80 μm.

[0040] The bonding strength of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating obtained from this example is ≥10 MPa, the maximum surface Vickers hardness can reach 400 HV, the neutral salt spray test resistance reaches more than 2000 h, wear resistance: wear coefficient (WI) < 0.3, and the dry insulation point resistance can reach 100 MΩ and above under a DC voltage of 1000 V.

[0041] Example 3

[0042] 1. Material preparation: Pre-treat TA1 titanium alloy, i.e., after cutting, grinding, and polishing, degrease it by ultrasonic cleaning in acetone solution.

[0043] 2. Preparation of plasma oxidation insulating ceramic layer:

[0044] (1) Composition of micro-plasma oxidation electrolyte: Sodium silicate 5 g / L, sodium hydroxide 5 g / L, sodium citrate 2 g / L, nano-aluminum oxide particles 5 g / L, sodium polyacrylate 0.1 g / L, sodium dodecyl polyoxyethylene sulfate aqueous solution 0.1 g / L, dissolve by stirring, and the rest is water.

[0045] (2) Preparation process: Put the titanium alloy sample (as the anode) into the electrolyte and carry out micro-plasma spark discharge oxidation on the sample by high-voltage pulse method. The pulse frequency is 1000 Hz, the pulse voltage is 400 V, and the current density is 4 A / dm 2 , the oxidation time is 20 min, and the thickness of the obtained plasma oxidation insulating ceramic layer is 15 - 17 μm. This plasma oxidation insulating ceramic layer is a porous insulating ceramic film rich in nano-particles, with a porosity of 25 - 30% and a pore diameter of 5 - 8 μm.

[0046] 3. Preparation of organic lubricating film:

[0047] First, etch the plasma oxidation insulating ceramic layer. The specific etching conditions are: Immerse the plasma oxidation insulating ceramic layer in 8% (mass concentration) hydrofluoric acid at room temperature for 3 s, take it out and immediately wash it with clean water for 2 min, and then wash it with deionized water for 2 min.

[0048] Then, composite an organic lubricating film on the surface of the plasma oxidation insulating ceramic layer. Composition of the spraying solution: Epoxy resin 70%, lubricant is talcum powder, mass fraction 15%, spraying agent is xylene, mass fraction 15%; Specific spraying conditions: The particle size of the organic resin powder is 400 mesh, the spraying temperature is set at 35 °C, the pressure is 2.8 MPa, the spraying distance is 20 - 30 mm, the drying temperature is 80 °C, and the drying time is 30 min. The total thickness of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating is 80 μm.

[0049] The bonding strength of the plasma oxidation insulating ceramic layer - organic lubricating film composite coating obtained from this example is ≥10 MPa, the maximum surface Vickers hardness can reach 400 HV, the neutral salt spray test resistance reaches more than 2000 h, wear resistance: wear coefficient (WI) <0.3, and the dry insulation point resistance can reach 100 MΩ and above under a DC voltage of 1000 V.

Claims

1. A high insulation coating on the surface of a titanium alloy, characterized in that: It is a plasma oxidation insulating ceramic layer-organic lubricating film composite coating. The micro plasma oxidation electrolyte for forming the plasma oxidation insulating ceramic layer includes the following components: 5-18 g / L sodium silicate, 1-5 g / L sodium hydroxide, 2-5 g / L sodium citrate, 5-10 g / L high insulation nanoparticles, 0.05-0.2 g / L anion electrolyte, and the rest is water; the organic lubricating spray liquid for forming the organic lubricating film includes 60-80% organic resin, 5-20% lubricant, and 15-20% spray in terms of mass percentage; The highly insulating nanoparticles are one or more of aluminum oxide, magnesium oxide, and zirconium oxide; The organic resin is epoxy resin or Teflon resin, the lubricant is one or more of molybdenum disulfide, white graphite, and talcum powder, and the spray is xylene.

2. The high insulation coating on the titanium alloy surface according to claim 1, characterized in that: The anion electrolyte is one or more of sodium polyacrylate, polyvinyl alcohol, sodium polystyrene sulfonate, polyacrylamide, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium fatty alcohol polyoxyethylene ether sulfate.

3. A method for preparing a high insulation coating on a titanium alloy surface, characterized in that: Based on the high insulation coating on the titanium alloy surface according to any one of claims 1 to 2, the preparation method comprises the following steps: Step 1: Surface pretreatment of titanium alloy; Step 2: Preparation of microplasma oxidation electrolyte: adding highly insulating nanoparticles and anionic electrolyte to a basic electrolyte formed by sodium silicate, sodium hydroxide, sodium citrate and water, and adsorbing the anionic electrolyte on the surface of the highly insulating nanoparticles by stirring to form anionic groups; Step 3: placing the titanium alloy into a micro plasma oxidation electrolyte, and performing micro plasma spark discharge oxidation on the titanium alloy using a high voltage pulse method to form a plasma oxidation insulating ceramic layer on the surface of the titanium alloy; Step 4: spraying an organic lubricating spray liquid on the surface of the plasma oxidation insulating ceramic layer, drying, forming an organic lubricating film, and finally forming a plasma oxidation insulating ceramic layer-organic lubricating film composite coating on the surface of the titanium alloy; In step 4, before spraying the organic lubricating spray liquid onto the surface of the plasma oxidation insulating ceramic layer, the plasma oxidation insulating ceramic layer is first etched. The specific etching conditions are: in a hydrofluoric acid with a mass concentration of 5 to 10%, the plasma oxidation insulating ceramic layer is etched for 2 to 5 s at room temperature, taken out and immediately washed with clean water for 2 to 5 min, and then washed with deionized water for 1 to 3 min.

4. The method for preparing a high insulation coating on a titanium alloy surface according to claim 3, characterized in that: In step 3, the temperature of the microplasma oxidation electrolyte is 15-50°C, and the specific conditions of the high voltage pulse are: pulse frequency 100-1000 Hz, pulse voltage 250-400V, current density 1-4 A / dm 2 , oxidation time 10~60 min.

5. The method for preparing a high insulation coating on a titanium alloy surface according to claim 3, characterized in that: The plasma oxidation insulating ceramic layer formed in step 3 is a porous insulating ceramic oxide film rich in nanoparticles, with a thickness of 5 to 30 μm, a porosity of 20 to 30%, and a pore size of 5 to 8 μm.

6. The method for preparing a high insulation coating on a titanium alloy surface according to claim 3, characterized in that: In step 4, the specific conditions for spraying are: organic resin powder particle size 200-400 mesh, spraying temperature 20-35°C, spraying pressure 1.2-2.8 MPa, spraying distance 10-40 mm, and drying conditions after spraying: drying temperature 60-120°C, drying time 30 min.

7. The method for preparing a high insulation coating on a titanium alloy surface according to claim 3, characterized in that: In the step 4, the total thickness of the plasma oxidation insulating ceramic layer-organic lubricating film composite coating is 50-80 μm.