A solid lubricating film on titanium and titanium alloy surfaces

Abstract

The present invention relates to the technical field of titanium and titanium alloy surface treatment, and proposes a solid lubricating film on the surface of titanium and titanium alloy, including an oxide film obtained by plasma electrolytic oxidation, wherein the phase composition of the oxide film includes titanium dioxide and alkali metal titanate, and the relative content of titanium dioxide is ≥70%. Through the above technical scheme, the problems of poor anti-seizure and wear resistance and high friction coefficient of titanium and titanium alloy surface treatment films in the related art are solved.

Description

Technical Field

[0001] The invention relates to the technical field of titanium and titanium alloy surface treatment, and in particular to a solid lubricating film on the surface of titanium and titanium alloy. Background Art

[0002] Titanium and titanium alloys have the advantages of high specific strength, corrosion resistance, high temperature resistance and good biocompatibility. They are widely used in cutting-edge defense technologies and emerging fields such as aerospace, marine development, high-end equipment, energy and chemical industry, medical equipment, etc., such as aircraft engine blades, deep-sea probe casings, high-end CNC machine tools, heat exchangers and artificial joints.

[0003] Titanium and titanium alloys are often used in high-speed, heavy-load and frequently started and stopped environments, such as the area between the compressor blades and the casing of aircraft engines, which places stringent requirements on their anti-seizure and wear resistance. However, due to the poor anti-seizure and wear resistance of titanium and titanium alloys, their further application in complex working conditions is limited.

[0004] Surface treatment technology can improve the bite resistance and wear resistance of titanium and titanium alloys. At present, the surface treatment technologies of titanium and titanium alloys mainly include painting, electroplating, vapor deposition, chemical conversion, anodizing and plasma electrolytic oxidation. Among them, affected by the passivation film on the surface of titanium and titanium alloys, the coating adhesion of painting and electroplating is poor; vapor deposition is only suitable for small and simple parts with limited use; the thickness of chemical conversion film and acidic anodized film is generally less than 0.3μm, and the film is thin and soft, with poor wear resistance and the risk of hydrogen embrittlement; alkaline anodizing method generally prepares thinner colored film layers. When at a high temperature above 90°C, although a film layer of more than 1μm can be prepared, the bite resistance and wear resistance still cannot meet the actual use requirements and cannot meet the international AMS2488-2019 standard. In recent years, plasma electrolytic oxidation method has attracted much attention. The film layer prepared by it can reach more than 10μm and the hardness is also improved. However, the surface of the film is rough, the film is loose and porous and easy to fall off, and lacks the possibility of practical application.

[0005] Therefore, in order to make titanium and titanium alloys suitable for the application of complex shapes and large parts, it is of great significance to develop a solid lubricating film with a low friction coefficient and good anti-seizure and wear resistance. Summary of the invention

[0006] The invention provides a solid lubricating film on the surface of titanium and titanium alloys, which solves the problems of poor anti-seizure and wear resistance and high friction coefficient of the surface treatment film of titanium and titanium alloys in the related art.

[0007] The technical solution of the present invention is as follows:

[0008] The present invention provides a solid lubricating film on the surface of titanium and titanium alloys, comprising an oxide film obtained by plasma electrolytic oxidation, wherein the phase composition of the oxide film comprises titanium dioxide and alkali metal titanate, and the relative content of the titanium dioxide is ≥70%.

[0009] As a further technical solution, the thickness of the oxide film is 0.3~3μm.

[0010] As a further technical solution, the surface hardness of the oxide film is 510~580HV.

[0011] As a further technical solution, the friction coefficient of the oxide film is ≤0.2.

[0012] As a further technical solution, during the plasma electrolytic oxidation, the voltage is 30-450V, the time is 3-60min, and the temperature is 10-60°C.

[0013] As a further technical solution, during the plasma electrolytic oxidation, the electrolyte includes the following components: alkali metal hydroxide and layered titanate.

[0014] As a further technical solution, the layered titanate is a layered titanate modified by a cationic organic compound.

[0015] As a further technical solution, the electrolyte also includes layered titanium dioxide.

[0016] As a further technical solution, the layered titanium dioxide is layered titanium dioxide modified by a cationic organic compound.

[0017] As a further technical solution, it also includes a solid lubricating coating disposed on the surface of the oxide film;

[0018] The solid lubricating coating comprises one of a molybdenum disulfide coating and a polytetrafluoroethylene coating;

[0019] The thickness of the solid lubricating coating is 10-20 μm.

[0020] The working principle and beneficial effects of the present invention are:

[0021] In the present invention, an oxide film is obtained on the surface of titanium and titanium alloys by using a plasma electrolytic oxidation method, which not only has a faster film-forming speed and stronger adhesion performance, but also improves the anti-seizure and wear resistance of the solid lubricating film on the surface of titanium and titanium alloys, reduces the friction coefficient, and helps to expand the service range of titanium and titanium alloys. Among them:

[0022] (1) Titanium dioxide and alkali metal titanate in the oxide film have the characteristics of low friction coefficient and high hardness. When the relative content of titanium dioxide is ≥70%, the oxide film can be endowed with low friction coefficient, high bite resistance and wear resistance;

[0023] (2) Alkali metal titanate has a layered crystal structure composed of TiO6 octahedrons and is a typical cationic layered compound. Similar to solid lubricants such as graphite and molybdenum disulfide, it can slide between layers, thereby reducing the friction coefficient of the oxide film and improving the bite resistance and wear resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Figure 1 The friction and wear curves of Example 1 and Example 13;

[0026] In the figure: (a) is the friction and wear curve of TC4 (Ti6Al4V) matrix, (b) is the friction and wear curve of Example 1, and (c) is the friction and wear curve of Example 13. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] It should be understood that, unless the context clearly indicates otherwise, the terms "include", "comprises" or "having" used in this application refer to the presence of a certain element, but do not exclude the presence or addition of one or more other elements. In addition, "includes" and / or "comprising" used in this article indicate the presence of shapes, numbers, steps, operations, members, elements and / or their combinations, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements and / or their combinations.

[0029] The numerical range represented by "~" in this application refers to the numerical range including the numerical range specified as the lower limit and the upper limit respectively before or after the word. When multiple values ​​of the upper limit or lower limit of any numerical range are mentioned, the range disclosed herein can be understood as a range with any one of the multiple upper limits mentioned as its upper limit and any one of the multiple lower limits as its lower limit.

[0030] The solid lubricating film on the surface of titanium and titanium alloy according to an embodiment of the present invention will be described in detail below.

[0031] According to one aspect of the present invention, a solid lubricating film on the surface of titanium and titanium alloys is provided, comprising an oxide film obtained by plasma electrolytic oxidation, wherein the phase composition of the oxide film comprises titanium dioxide and alkali metal titanate, and the relative content of titanium dioxide is ≥70%.

[0032] In the present invention, plasma electrolytic oxidation is to immerse the titanium and titanium alloy substrate in an electrolyte as an anode and apply voltage thereto. The substrate metal reacts with the chemical substances in the electrolyte to form a thin insulating barrier layer on the surface of the metal substrate. As the voltage increases, the insulating shielding layer undergoes insulation breakdown, accompanied by an electron avalanche phenomenon, and then arc discharge begins. The heat of the arc discharge causes melting on the substrate surface, and an oxide film composed of titanium and electrolyte components continues to grow, forming an oxide film with a low friction coefficient.

[0033] In the present invention, the titanium and titanium alloy substrate is obtained after being polished, degreased and washed.

[0034] In the present invention, the general composition of alkali metal titanate can be represented by the chemical formula M2O·nTiO2, where M represents an alkali metal ion. When n≥2, alkali metal titanate is a typical cationic layered compound that can undergo reactions such as intercalation, exfoliation, and ion exchange, and thus has excellent physical and chemical properties. It can slide between layers, thereby reducing the friction coefficient of the oxide film and improving the bite resistance and wear resistance.

[0035] In the present invention, the phase composition of the oxide film can be characterized by X-ray diffractometer technology, and the relative content of titanium dioxide can be quantitatively obtained from the corresponding XRD spectrum. For example, the single line method, external standard method, internal standard method and full spectrum fitting method can be used for quantification, preferably the full spectrum fitting method.

[0036] In one embodiment of the present invention, titanium and titanium alloys may be pure titanium, TC4 titanium alloy, TA1 titanium alloy, TA2 titanium alloy, and the like.

[0037] In one embodiment of the present invention, the thickness of the oxide film is 0.3-3 μm, for example, 0.3-1.9 μm, 0.6-1.2 μm, 0.9-2.1 μm, 1.2-3.0 μm, etc.

[0038] In the present invention, when the thickness of the oxide film is less than 0.3 μm, the oxide film is too thin and cannot achieve the effects of anti-seizure and wear resistance; when the thickness of the oxide film is greater than 3 μm, the oxide film is loose and has poor adhesion to the substrate.

[0039] In one embodiment of the present invention, the surface hardness of the oxide film is 510-580 HV, for example, 510 HV, 520 HV, 538 HV, 540 HV, 550 HV, 560 HV, 570 HV, 580 HV, etc.

[0040] In the present invention, the surface hardness may be a value measured by a microhardness tester, for example, a value measured by a micro Vickers hardness tester (Mitutoyo HM-102) and the method specified in ASTM E384-2017.

[0041] In one embodiment of the present invention, the friction coefficient of the oxide film is ≤0.2, for example, it can be 0.2, 0.14, 0.13, 0.11, 0.10, 0.08, 0.03, 0.02, etc.

[0042] In the present invention, the friction coefficient may be a value measured by a friction and wear tester. For example, the friction coefficient may be a value measured by a ball-on-disc friction and wear tester and the method specified in ASTM G99-05 (2016).

[0043] In one embodiment of the present invention, the color of the oxide film is gray-black.

[0044] In one embodiment of the present invention, plasma electrolytic oxidation includes one of constant voltage pulse electrolysis, constant voltage direct current electrolysis, and constant current electrolysis, preferably constant voltage pulse electrolysis or constant voltage direct current electrolysis.

[0045] In the present invention, when constant voltage electrolysis or pulse electrolysis is used, it helps to further improve the uniformity of the oxide film.

[0046] In one embodiment of the present invention, during plasma electrolytic oxidation, the voltage is 30-450 V, preferably 50-300 V, for example, it can be 50 V, 60 V, 80 V, 100 V, 150 V, 200 V, 250 V, 300 V, etc.

[0047] In the present invention, when the voltage is 30-450V, it helps to improve the stability of plasma electrolytic oxidation.

[0048] In one embodiment of the present invention, the plasma electrolytic oxidation time is 3 to 60 minutes, for example, it can be 3 minutes, 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, 60 minutes, etc.

[0049] In the present invention, the time of plasma electrolytic oxidation can be adjusted according to the type of substrate alloy, film quality and energy efficiency.

[0050] In one embodiment of the present invention, during plasma electrolytic oxidation, the temperature is 10-60°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, etc.

[0051] In the present invention, when the temperature is lower than 10°C, the film forming speed of plasma electrolytic oxidation is too slow and is not suitable for actual production; when the temperature is higher than 60°C, the plasma electrolytic oxidation is too intense, the substrate is easily locally burned, and it is difficult to control.

[0052] In one embodiment of the present invention, during plasma electrolytic oxidation, the cathode material includes one of stainless steel, graphite, and titanium.

[0053] In one embodiment of the present invention, during plasma electrolytic oxidation, the electrolyte includes the following components: alkali metal hydroxide and layered titanate.

[0054] In one embodiment of the present invention, the alkali metal hydroxide may be any alkali metal hydroxide, preferably one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide. For example, it may be sodium hydroxide, potassium hydroxide, lithium hydroxide, a combination of sodium hydroxide and potassium hydroxide, a combination of sodium hydroxide and lithium hydroxide, a combination of potassium hydroxide and lithium hydroxide, or a combination of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0055] In one embodiment of the present invention, the layered titanate includes one of layered sodium titanate, layered potassium titanate, and layered lithium titanate, for example, layered sodium dititanate, layered sodium trititanate, layered potassium titanate, layered lithium titanate, and the like.

[0056] In one embodiment of the present invention, in the electrolyte, the concentration of alkali metal hydroxide is 10~50g / L, and the concentration of layered titanate is 8~10g / L. For example, the concentration of alkali metal hydroxide can be 10g / L, 20g / L, 30g / L, 40g / L, 50g / L, etc.; the concentration of layered titanate can be 8g / L, 9g / L, 10g / L, etc.

[0057] In one embodiment of the present invention, the solvent of the electrolyte is water.

[0058] In one embodiment of the present invention, the layered titanate in the electrolyte is a layered titanate modified with a cationic organic compound.

[0059] In the present invention, layered titanates are modified by cationic organic compounds to obtain layered titanates with cationic organic compounds inserted between layers. By inserting organic matter between the layers, the titanate layers become easier to slide, which can further reduce the friction coefficient and further improve the anti-seizure and wear resistance.

[0060] In one embodiment of the present invention, in the layered titanate modified by a cationic organic compound, the cationic organic compound includes one or more of ammonium salts, guanidinium salts, pyridinium salts, for example, it can be a primary ammonium salt, a secondary ammonium salt, a tertiary ammonium salt and a quaternary ammonium salt, such as ammonium acetate, ammonium propionate, ammonium butyrate and choline, more preferably a quaternary ammonium salt, such as choline.

[0061] In one embodiment of the present invention, the preparation method of cationic organic compound modified layered titanate includes the following steps: dissolving the cationic organic compound in water, adding layered titanate to disperse evenly, and modifying to obtain cationic organic compound modified layered titanate.

[0062] In one embodiment of the present invention, when preparing the cationic organic compound modified layered titanate, the modification temperature is 40-60° C. and the modification time is 2-4 hours.

[0063] In one embodiment of the present invention, in the cationic organic compound modified layered titanate, the weight ratio of the cationic organic compound to the layered titanate is 4 to 8:100, for example, 4:100, 5:100, 6:100, 7:100, 8:100, etc.

[0064] In one embodiment of the present invention, the electrolyte further comprises layered titanium dioxide.

[0065] In the present invention, adding layered titanium dioxide to the electrolyte can increase the relative content of titanium dioxide in the oxide film, further reduce the friction coefficient, and further improve the anti-seizure and wear resistance. Layered titanium dioxide can be prepared by conventional hydrothermal methods, molten salt methods, mechanical methods, and sol-gel methods. For example, it can be obtained by first exfoliating layered titanate using ethylenediamine and then hydrothermally treating it at 150°C for 25 hours.

[0066] In one embodiment of the present invention, the average thickness of the layered titanium dioxide is 30~80nm, and the average length is 3~17μm. For example, the average thickness can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, etc.; the average length can be 3μm, 5μm, 10μm, 15μm, 17μm, etc.

[0067] In one embodiment of the present invention, the concentration of layered titanium dioxide in the electrolyte is 0.5~50g / L, for example, it can be 0.5g / L, 1g / L, 10g / L, 20g / L, 30g / L, 40g / L, 50g / L, etc.

[0068] In one embodiment of the present invention, the layered titanium dioxide is layered titanium dioxide modified with a cationic organic compound.

[0069] In the present invention, cationic organic compounds are inserted between titanium dioxide layers to make the titanium dioxide layers more slidable, thereby further reducing the friction coefficient and further improving the anti-seizure property and wear resistance.

[0070] In one embodiment of the present invention, in the layered titanium dioxide modified with a cationic organic compound, the cationic organic compound includes one or more of an ammonium salt, a guanidinium salt, a pyridinium salt, for example, a primary ammonium salt, a secondary ammonium salt, a tertiary ammonium salt, a quaternary ammonium salt, etc., such as ammonium acetate, ammonium propionate, ammonium butyrate and choline, etc., more preferably a quaternary ammonium salt, such as choline, etc.

[0071] In one embodiment of the present invention, a method for preparing cationic organic compound modified layered titanium dioxide comprises the following steps: dissolving the cationic organic compound in water, adding the layered titanium dioxide to disperse uniformly, and modifying the layered titanium dioxide to obtain the cationic organic compound modified layered titanium dioxide.

[0072] In one embodiment of the present invention, when preparing cationic organic compound-modified layered titanium dioxide, the modification temperature is 30-50° C. and the modification time is 1-3 hours.

[0073] In one embodiment of the present invention, in the cationic organic compound-modified layered titanium dioxide, the weight ratio of the cationic organic compound to the layered titanium dioxide is 2 to 6:100, for example, 2:100, 3:100, 4:100, 5:100, 6:100, etc.

[0074] According to another aspect of the present invention, a solid lubricating film on the surface of titanium and titanium alloy also includes a solid lubricating coating arranged on the surface of the oxide film, the solid lubricating coating includes one of a molybdenum disulfide coating and a polytetrafluoroethylene coating, and the thickness of the solid lubricating coating is 10~20μm.

[0075] In the present invention, according to the application and performance requirements, a layer of solid lubricating coating can be further coated on the surface of the oxide film obtained by plasma electrolytic oxidation to further reduce the friction coefficient and further improve the anti-seizure and wear resistance to meet the working conditions of high pressure and long-term friction.

[0076] In one embodiment of the present invention, the raw materials of the solid lubricating coating include a solid lubricant, a binder resin and a solvent;

[0077] The solid lubricant includes one of molybdenum disulfide and polytetrafluoroethylene;

[0078] The binder resin includes one or more of polyamide resin, polyimide resin, epoxy resin, and polyurethane resin;

[0079] The solvent includes one or both of ethyl acetate and isopropanol.

[0080] In the present invention, the solid lubricating coating is prepared by coating, and the coating method can be dip coating, spray coating, brush coating, screen printing, etc. The coating method can be determined according to the shape and quantity of the coated object. After coating, the solid lubricating coating can be dried and solidified by room temperature drying, heating drying, reduced pressure drying, etc.

[0081] In one embodiment of the present invention, the weight ratio of the solid lubricant, the binder resin and the solvent is 10-14:18:70, preferably 12:18:70.

[0082] In this specification, unless otherwise specified, the thickness of the oxide film and the solid lubricating coating may be the thickness measured by scanning electron microscope (SEM) observation of a cross section of the film, or may be the thickness measured using a known thickness gauge.

[0083] The present invention will be described in detail below with reference to examples. The embodiments according to the present invention described below can be modified into various forms, so the scope of the present invention should not be interpreted as being limited to the embodiments described in detail below. Embodiments are provided to help those skilled in the art to more easily understand the present invention.

[0084] In the following examples and comparative examples, unless otherwise specified, the average thickness of the layered titanium dioxide is 50 nm and the average length is 10 μm.

[0085] Example 1

[0086] A method for preparing a solid lubricating film on the surface of titanium and titanium alloys comprises the following steps:

[0087] S1: Add an appropriate amount of water to a beaker, add 10g of sodium hydroxide and 10g of layered sodium trititanate, and add water to make the volume to 1L to obtain an electrolyte with a pH value of 13.2;

[0088] S2: A TC4 (Ti6Al4V) titanium alloy disc with a diameter of 30 mm and a thickness of 10 mm was subjected to a polishing treatment, degreasing, and water washing, and then subjected to plasma electrolytic oxidation to obtain a gray-black solid lubricating film;

[0089] During the plasma electrolytic oxidation, a constant voltage pulse electrolysis method was used, with a forward voltage of 85 V, a time of 10 min, a temperature of 25° C., a pulse width of 20 ms, and a pulse interval of 2 ms.

[0090] Example 2

[0091] A method for preparing a solid lubricating film on the surface of titanium and titanium alloys comprises the following steps:

[0092] S1: Add an appropriate amount of water to a beaker, add 50 g of sodium hydroxide and 8 g of layered sodium titanate, and add water to make the volume to 1 L to obtain an electrolyte with a pH value of 13.1;

[0093] S2: A TC4 (Ti6Al4V) titanium alloy disc with a diameter of 30 mm and a thickness of 10 mm was subjected to a polishing treatment, degreasing, and water washing, and then subjected to plasma electrolytic oxidation to obtain a gray-black solid lubricating film;

[0094] During the plasma electrolytic oxidation, a constant voltage pulse electrolysis method was used, with a forward voltage of 120 V, a time of 15 min, a temperature of 25° C., a pulse width of 20 ms, and a pulse interval of 5 ms.

[0095] Example 3

[0096] The only difference between this embodiment and embodiment 1 is that in this embodiment, the layered sodium trititanate is layered sodium trititanate modified with ammonium propionate, and the preparation method of the layered sodium trititanate modified with ammonium propionate is: dissolve 8g of ammonium propionate in water, add 100g of layered sodium trititanate and disperse evenly, stir at 60°C for 2h, and obtain the layered sodium trititanate modified with ammonium propionate.

[0097] Example 4

[0098] The only difference between this embodiment and embodiment 1 is that in this embodiment, the layered sodium trititanate is layered sodium trititanate modified with guanidine carbonate, and the preparation method of the layered sodium trititanate modified with guanidine carbonate is as follows: 8 g of guanidine carbonate is dissolved in water, 100 g of layered sodium trititanate is added and dispersed evenly, and the mixture is stirred at 60° C. for 2 h to obtain layered sodium trititanate modified with guanidine carbonate.

[0099] Example 5

[0100] The only difference between this embodiment and embodiment 1 is that in this embodiment, the layered sodium trititanate is a layered sodium trititanate modified by pyridine hydrochloride, and the preparation method of the layered sodium trititanate modified by pyridine hydrochloride is: dissolve 4g of pyridine hydrochloride in water, add 100g of layered sodium trititanate and disperse evenly, stir at 40°C for 4h, and obtain the layered sodium trititanate modified by pyridine hydrochloride.

[0101] Example 6

[0102] The only difference between this embodiment and embodiment 3 is that in this embodiment, the layered sodium trititanate is choline-modified layered sodium trititanate, and during preparation, ammonium propionate is replaced with an equal amount of choline.

[0103] Example 7

[0104] The only difference between this embodiment and embodiment 1 is that in this embodiment, step S1 is: add an appropriate amount of water to a beaker, add 20g of sodium hydroxide, 10g of layered sodium trititanate and 0.5g of layered titanium dioxide, add water to make the volume to 1L, and obtain an electrolyte with a pH value of 13.2.

[0105] Example 8

[0106] The only difference between this embodiment and embodiment 7 is that in this embodiment, 15 g of layered titanium dioxide is added.

[0107] Example 9

[0108] The only difference between this embodiment and embodiment 7 is that in this embodiment, 50 g of layered titanium dioxide is added.

[0109] Example 10

[0110] The only difference between this embodiment and embodiment 8 is that, in this embodiment, the layered titanium dioxide is layered titanium dioxide modified with an equal amount of ammonium acetate;

[0111] The preparation method of ammonium acetate modified layered titanium dioxide is as follows: 2 g of ammonium acetate is dissolved in water, 100 g of layered titanium dioxide is added and dispersed evenly, and the mixture is stirred at 30° C. for 3 h to obtain ammonium acetate modified layered titanium dioxide.

[0112] Embodiment 11

[0113] The only difference between this example and Example 8 is that in this example, the layered titanium dioxide is an equal amount of choline-modified layered titanium dioxide;

[0114] The preparation method of choline-modified layered titanium dioxide is as follows: 2 g of choline is dissolved in water, 100 g of layered titanium dioxide is added and dispersed evenly, and the mixture is stirred at 30° C. for 3 h to obtain choline-modified layered titanium dioxide.

[0115] Example 12

[0116] The only difference between this embodiment and embodiment 8 is that, in this embodiment, the layered titanium dioxide is layered titanium dioxide modified with an equal amount of guanidine carbonate;

[0117] The preparation method of guanidine carbonate-modified layered titanium dioxide is as follows: 6 g of guanidine carbonate is dissolved in water, 100 g of layered titanium dioxide is added and dispersed evenly, and the mixture is stirred at 50° C. for 1 hour to obtain guanidine carbonate-modified layered titanium dioxide.

[0118] Embodiment 13

[0119] The difference between this embodiment and embodiment 1 is that, in this embodiment, a layer of molybdenum disulfide coating with a thickness of 15 μm is spray-coated on the surface of the oxide film obtained by plasma electrolytic oxidation;

[0120] The preparation method of the molybdenum disulfide coating comprises: uniformly mixing molybdenum disulfide, polyamide resin and solvent, spraying and coating, and drying and curing to obtain the molybdenum disulfide coating;

[0121] Among them, the average particle size of molybdenum disulfide is 5 μm; the weight average molecular weight of polyamide resin is 3500; the solvent is a mixed solvent of ethyl acetate and isopropanol in a volume ratio of 1:1; the weight ratio of molybdenum disulfide, polyamide resin and solvent is 12:18:70, and the drying and curing treatment is divided into two steps, the first step is drying at 120°C for 30 minutes, and the second step is drying at 180°C for 60 minutes.

[0122] Embodiment 14

[0123] The only difference between this embodiment and embodiment 1 is that in this embodiment, a layer of polytetrafluoroethylene coating with a thickness of 15 μm is spray-coated on the surface of the oxide film obtained by plasma electrolytic oxidation;

[0124] The preparation method of the polytetrafluoroethylene coating comprises: uniformly mixing polytetrafluoroethylene, polyamide resin and solvent, spraying and coating, and drying and curing to obtain the polytetrafluoroethylene coating;

[0125] Among them, the weight average molecular weight of polytetrafluoroethylene is 3000; the weight average molecular weight of polyamide resin is 3500; the solvent is a mixed solvent of ethyl acetate and isopropanol in a volume ratio of 1:1; the weight ratio of polytetrafluoroethylene, polyamide resin and solvent is 12:18:70, and the drying and curing treatment is divided into two steps, the first step is drying at 120°C for 30 minutes, and the second step is drying at 180°C for 60 minutes.

[0126] Comparative Example 1

[0127] A method for preparing a solid lubricating film on the surface of titanium and titanium alloys comprises the following steps:

[0128] S1: Add an appropriate amount of water to a beaker, add 25g of sulfuric acid (mass fraction 98%), and add water to make the volume to 1L to obtain an electrolyte;

[0129] S2: A TC4 (Ti6Al4V) titanium alloy disc with a diameter of 30 mm and a thickness of 10 mm is polished, degreased, washed, and then anodized to obtain a colored solid lubricating film;

[0130] During anodization, a DC constant voltage method was used with a voltage of 60 V, a temperature of 25° C., and a time of 15 min.

[0131] Comparative Example 2

[0132] A method for preparing a solid lubricating film on the surface of titanium and titanium alloys comprises the following steps:

[0133] S1: Add an appropriate amount of water to a beaker, add 30g of sodium hydroxide, and add water to make the volume to 1L to obtain an electrolyte;

[0134] S2: A TC4 (Ti6Al4V) titanium alloy disc with a diameter of 30 mm and a thickness of 10 mm was polished, degreased, washed, and then anodized to obtain a gray solid lubricating film;

[0135] During anodization, a DC constant voltage method was used with a voltage of 16 V, a temperature of 93° C., and a time of 25 min.

[0136] The solid lubricating films prepared in Examples 1 to 14 and Comparative Examples 1 to 2 were tested as follows:

[0137] ① Phase composition of oxide film: The oxide film was analyzed using a thin film X-ray diffractometer (model XRD6100), and the relative content of titanium dioxide was quantified using the full spectrum fitting method;

[0138] ②Thickness of oxide film: The thickness of oxide film was measured by cross-section observation using a scanning electron microscope (model JCM-5000);

[0139] ③ Surface hardness of oxide film: The surface hardness of oxide film was measured by using a micro Vickers hardness tester (model Mitutoyo HM-102), where the bearing capacity was 25 gf;

[0140] ④ Friction and wear performance: A friction and wear test was conducted using a ball-on-disc friction and wear tester, wherein the ball was a 6.35 mm diameter untreated TC4 (Ti6Al4V) titanium alloy, and the disks were 30 mm diameter TC4 (Ti6Al4V) titanium alloys treated in Examples 1 to 14 and Comparative Examples 1 to 2. The friction and wear test was conducted in the atmosphere (25°C, 35%RH) without lubrication, with a load of 10N, a rotation speed of 250rpm, and a contact radius of 5mm, with a sliding distance of 12m. The friction coefficient and specific wear rate were tested and the wear resistance was evaluated. The evaluation criteria for wear resistance were:

[0141] ◎: Friction coefficient <0.10, specific wear rate (mm 3 / Nm)<0.50×10 －6 ;

[0142] ○: 0.10≤Friction coefficient<0.20, 0.50×10 -6 ≤Specific wear rate(mm 3 / Nm)<1.0×10 -6 ;

[0143] △: 0.20≤friction coefficient≤0.30, 1.0×10 -6 ≤Specific wear rate(mm3 / Nm)≤1.5×10 -6 ;

[0144] ×: Friction coefficient>0.30, specific wear rate (mm 3 / Nm)>1.5×10 -6 .

[0145] The test results are shown in Table 1, and the friction and wear curves of Example 1 and Example 13 are shown in Table 1. Figure 1 shown.

[0146] Table 1 Solid lubricating film performance test results

[0147]

[0148] Comparison between Example 1 and Comparative Examples 1-2 shows that by making the phase composition of the oxide film to be titanium dioxide and alkali metal titanate, the friction coefficient can be significantly reduced, and the anti-seizure property and wear resistance can be significantly improved.

[0149] Comparison between Example 1 and Examples 3 to 6 shows that the friction coefficient can be further reduced and the anti-seizure and wear resistance can be further improved by inserting cationic organic compounds between the layered titanate layers.

[0150] Comparison between Example 1 and Examples 7 to 12 shows that the addition of layered titanium dioxide in the electrolyte can further reduce the friction coefficient and further improve the anti-seizure property and wear resistance.

[0151] Comparison between Example 8 and Examples 10 to 12 shows that the friction coefficient can be further reduced and the anti-seizure and wear resistance can be further improved by inserting cationic organic compounds between the layered titanium dioxide layers.

[0152] Comparison between Example 1 and Examples 13-14 shows that further coating a layer of solid lubricating coating on the surface of the oxide film obtained by plasma electrolytic oxidation can further reduce the friction coefficient and further improve the anti-seizure and wear resistance.

[0153] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A solid lubricating film on the surface of titanium and titanium alloys, comprising an oxide film obtained by plasma electrolytic oxidation, characterized in that: The phase composition of the oxide film includes titanium dioxide and alkali metal titanate, and the relative content of titanium dioxide is ≥70%; During the plasma electrolytic oxidation, the electrolyte includes the following components: alkali metal hydroxide, layered titanate; The electrolyte also includes layered titanium dioxide; The layered titanium dioxide is layered titanium dioxide modified by a cationic organic compound.

2. The solid lubricating film on the surface of titanium and titanium alloy according to claim 1, characterized in that: The thickness of the oxide film is 0.3-3 μm.

3. The solid lubricating film on the surface of titanium and titanium alloy according to claim 1, characterized in that: The surface hardness of the oxide film is 510-580 HV.

4. The solid lubricating film on the surface of titanium and titanium alloy according to claim 1, characterized in that: The friction coefficient of the oxide film is ≤0.

2.

5. A solid lubricating film on the surface of titanium and titanium alloy according to any one of claims 1 to 4, characterized in that: During the plasma electrolytic oxidation, the voltage is 30-450V, the time is 3-60min, and the temperature is 10-60°C.

6. The solid lubricating film on the surface of titanium and titanium alloy according to claim 1, characterized in that: The layered titanate is a layered titanate modified by a cationic organic compound.

7. The solid lubricating film on the surface of titanium and titanium alloy according to claim 1, characterized in that: Also includes a solid lubricating coating disposed on the surface of the oxide film; The solid lubricating coating comprises one of a molybdenum disulfide coating and a polytetrafluoroethylene coating; The thickness of the solid lubricating coating is 10-20 μm.

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