In-situ preparation method for generating red ceramic film layer on titanium metal surface through phase change induction

Abstract

The invention relates to the technical field of titanium metal surface treatment, in particular to an in-situ preparation method for generating a red ceramic film layer on a titanium metal surface through phase change induction. According to the method, an electrolyte system containing Fe salt is utilized, a black ceramic film layer is generated under the specific micro-arc oxidation condition, then conversion of the color of the film layer is achieved through heat treatment, and finally the red ceramic film layer which is uniform in color and luster and high in color saturation is obtained. Compared with the prior art, the method has the following remarkable characteristics that controllable conversion from black to red on the surface of the titanium metal is realized by optimizing micro-arc oxidation power supply parameters and heat treatment conditions, and a new solution is provided for application of the micro-arc oxidation technology in the field of functional coatings. The obtained red ceramic film layer is uniform in color and bright in color, the corrosion resistance of the film layer after heat treatment is remarkably improved, and the double requirements of a high-performance material for surface protection and attractiveness are met.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of titanium metal surface treatment, in particular to an in-situ preparation method for generating a red ceramic film layer on the surface of titanium metal through phase transition induction. BACKGROUND

[0002] Titanium and its alloys have been widely used in biomedical, aerospace, and decorative items due to their excellent biocompatibility, corrosion resistance, and high strength. To further enhance their performance and meet diverse application needs, functionalizing the surface of titanium metal is particularly important.

[0003] Micro-arc oxidation (MAO) is an important technology for surface modification of light alloys such as aluminum, magnesium, and titanium. This technology involves applying high voltage in an electrolyte, and as the voltage increases, plasma discharge occurs, forming a thick and dense ceramic film layer on the metal surface. This film layer not only significantly improves the corrosion resistance and wear resistance of the substrate, but also enhances its mechanical properties. However, the film layer prepared by traditional micro-arc oxidation is mostly light gray, with a single color, making it difficult to meet the special needs of color diversification on the surface of titanium metal in practical applications.

[0004] In response to this technical bottleneck, researchers have explored the method of introducing a heat treatment process after micro-arc oxidation in recent years. By adjusting the heat treatment conditions (such as temperature, time, and atmosphere), phase transition and the formation of red ceramic film layers can be induced. This heat treatment process can promote the phase transition and crystal structure reorganization of the film layer, thereby imparting specific colors to the film layer. This method not only retains the excellent physical and chemical properties of the micro-arc oxidation ceramic film, but also broadens its potential in decorative and functional applications by introducing color characteristics.

[0005] Studies have shown that the formation mechanism of red ceramic film layers is closely related to the doping of metal ions in the film layer and their oxidation states. This discovery provides an important theoretical basis for optimizing the process of combining micro-arc oxidation with heat treatment, and lays a research foundation for developing new surface coloration technologies. However, current research on heat treatment processes after micro-arc oxidation on the surface of titanium metal still has certain limitations, especially in the combination of color control and film layer performance stability, which has not yet reached the ideal effect.

[0006] Therefore, a technical solution is needed that can efficiently prepare red ceramic film layers with excellent physical and chemical properties and specific colors, to break through the bottleneck of traditional surface treatment technologies and meet the market demand for high-performance, multifunctional titanium alloy materials. SUMMARY

[0007] The application aims to provide an in-situ preparation method for generating a red ceramic film layer on a titanium metal surface through phase transition induction, a technology for obtaining a red ceramic film layer by heat treatment after micro-arc oxidation in an electrolyte containing Fe salt as a coloring salt, and high-efficiency preparation of a red ceramic film layer on a titanium metal surface by combining micro-arc oxidation and heat treatment, which solves the problems of single color and insufficient performance of traditional technologies.

[0008] The technical scheme of the application is:

[0009] An in-situ preparation method for generating a red ceramic film layer on a titanium metal surface through phase transition induction, comprising the following steps:

[0010] S1, titanium metal surface pretreatment: ultrasonic cleaning of titanium metal in anhydrous ethanol for 4-6 min to remove surface oil stains and residual substances, washing with deionized water and drying in an oven;

[0011] S2, preparation of micro-arc oxidation electrolyte, the electrolyte is composed of the following components: sodium silicate 0.5 g / L-50 g / L; sodium hexametaphosphate 0.5 g / L-50 g / L; sodium hydroxide 1 g / L-100 g / L; colorant 1 is ferric citrate 1 g / L-100 g / L; colorant 2 is potassium ferricyanide 1 g / L-100 g / L; the rest is deionized water;

[0012] S3, micro-arc oxidation: using the surface pretreated titanium metal as the anode of the micro-arc oxidation power supply, high-purity graphite sheet as the cathode, and performing micro-arc oxidation in the electrolyte to prepare a black ceramic film layer, the micro-arc oxidation parameters are as follows: micro-arc oxidation time 5 min-100 min; current density of single-pole output full-reverse direct current pulse power supply 1 A / dm 2 ~ 50 A / dm 2 ; electrolyte temperature 5-50 DEG C; frequency 50 Hz-2000 Hz; duty cycle 1%-50%;

[0013] S4, drying treatment: ultrasonic cleaning of the micro-arc oxidized titanium metal for 2 min-50 min and natural air drying;

[0014] S5, heat treatment: annealing of the micro-arc oxidized titanium metal in a tubular heat treatment furnace, air cooling to room temperature, and obtaining a red ceramic film layer.

[0015] The in-situ preparation method for generating a red ceramic film layer on a titanium metal surface through phase transition induction, in step S5, the heat treatment is performed in an air atmosphere, the holding temperature is 400-1000 DEG C, and the holding time is 1-1000 h.

[0016] The heat treatment holding temperature in step S5 is preferably 500-700 DEG C, and the holding time is 5-50 hours.

[0017] The red ceramic film layer obtained by the in-situ preparation method of the titanium metal surface through phase transition induction has the following performance indexes: the thickness of the red ceramic film layer is 1-50 microns; the phase composition of the red ceramic film layer includes TiO2 and Fe2O3, and the Fe2O3 is distributed in the TiO2 carrier, and the Fe2O3 is the color phase of the red ceramic film layer.

[0018] The atomic content of Fe in the red ceramic film layer is 1-30%.

[0019] The chroma value of the red ceramic film layer is: a*: 0-20, and a* represents the red color: green (-128) to red (+128).

[0020] The chroma value of the red ceramic film layer is preferably: a*: 5-15.

[0021] The corrosion resistance performance indexes of the red ceramic film layer are as follows: corrosion potential E corr : -0.25-0.25 V; corrosion current density: 8*10 -6 -5*10 -5 A*cm -2 ; hardness: 400-600 HV.

[0022] The design idea of the present application is:

[0023] The application in-situ prepares a black micro-arc oxidation ceramic film layer on the surface of titanium metal through a micro-arc oxidation process in an electrolyte containing iron citrate and potassium ferricyanide as colorants, and then performs heat treatment at high temperature, which promotes phase transition and crystal structure recombination of the color-developing phase in the film layer, and the color-developing phase in the film layer is changed from Fe3O4 to Fe2O3, and the color of the film layer is changed from black to red, so that a red ceramic film layer is in-situ prepared on the surface of titanium metal through micro-arc oxidation and heat treatment, the prepared red ceramic film layer is uniform in color, with the increase of the concentration of the colorants, the content of Fe in the film layer is correspondingly increased, and the color saturation is also correspondingly increased, the relative atomic content of Fe in the red ceramic film layer is 1% to 30%, and the color value of the ceramic film layer is a*: 5 to 15 (a* represents red color: green (-128) to red (+128)).

[0024] The application has deep research on the oxidation behavior of Fe-based compounds, the relationship between heat treatment conditions and color-developing phase, and finds that the synergistic effect of specific colorants and heat treatment is as follows: iron citrate and potassium ferricyanide provide Fe source in micro-arc oxidation to form a black Fe3O4 film layer, and subsequent heat treatment promotes Fe 4+ / Fe 3+ Valence state transition and crystal structure recombination (Fe3O4→Fe2O3). In addition, the concentration ranges of sodium silicate, sodium hexametaphosphate and sodium hydroxide in the electrolyte, and the parameters such as current density, frequency and duty cycle of micro-arc oxidation, and the temperature and time of heat treatment form a synergy to ensure the uniformity and performance stability of the red film layer. Therefore, the application combines the micro-arc oxidation with iron citrate and potassium ferricyanide as colorants and the heat treatment under specific conditions into a two-step method to realize in-situ preparation of a red ceramic film layer on the surface of titanium metal, and realizes the preparation of a red ceramic film layer on the surface of titanium metal through the synergistic process of specific Fe-based colorant combination, micro-arc oxidation and heat treatment phase transition, and solves the problem that the color is single and the performance and color regulation are difficult to be considered in the prior art.

[0025] Compared with the prior art, the application has the following advantages and beneficial effects:

[0026] 1. The application is a new method for obtaining a red ceramic film layer on the surface of titanium metal after micro-arc oxidation and heat treatment. The method uses an electrolyte system containing Fe salt to generate a black ceramic film layer under specific micro-arc oxidation conditions, and then realizes the color change of the film layer through heat treatment, finally obtaining a red ceramic film layer with uniform color and high color saturation. The corrosion resistance of the red ceramic film layer is significantly improved compared to the black ceramic film layer after micro-arc oxidation, leading to the innovative development of traditional surface treatment technology.

[0027] 2. The application combines micro-arc oxidation technology and heat treatment process and has no restrictions on the geometric shape and size of the sample. Irregularly shaped samples can be processed, which not only expands the application range of micro-arc oxidation technology, but also provides a new technical path for the surface modification of titanium materials, which is particularly important for complex-shaped high-requirement components in many aerospace, medical equipment and other industries.

[0028] 3. The preparation process of the application is simple and easy to operate, does not require complex equipment, and the raw materials used are environmentally friendly, non-toxic, and pollution-free to the environment, with low production cost and good industrial application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 Figure 1 is a macroscopic morphology diagram of the black ceramic film on titanium metal after micro-arc oxidation of Examples 1-4. Among them, (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0030] Figure 2 Figure 2 is a macroscopic morphology diagram of the red ceramic film on titanium metal after heat treatment of Examples 1-4. Among them, (a) is Example 1, (b) is Example 2, (c) is Example 3, and (d) is Example 4.

[0031] Figure 3 Figure 3 is a 1000 times microscopic morphology diagram of the ceramic film after micro-arc oxidation and heat treatment of Example 4. Among them, (a) is the ceramic film after micro-arc oxidation, and (b) is the ceramic film after heat treatment.

[0032] Figure 4 Figure 4 is an EDS element content analysis of the ceramic film after micro-arc oxidation and heat treatment of Example 4.

[0033] Figure 5 Figure 5 is an XRD phase analysis diagram of the ceramic film after micro-arc oxidation and heat treatment of Example 4. In the figure, the horizontal axis 2θ is the diffraction angle (degree), and the vertical axis Intensity is the relative intensity (a.u.).

[0034] Figure 6 Figure 6 is the ultraviolet-visible light absorption curve of the ceramic film after micro-arc oxidation and heat treatment of Example 4.

[0035] Figure 7Potentiodynamic polarization curves of the ceramic film after micro-arc oxidation and heat treatment in Example 4 were obtained after the ceramic film was immersed in a 3.5wt% NaCl aqueous solution for 30 minutes. In the figure, the abscissa E is the electrode potential (V) relative to a saturated calomel electrode, and the ordinate Log i is the logarithm of the current density (A x cm VS.SCE ). -2

[0036] Figure 8 Figures showing the macroscopic morphology of the irregularly shaped sample before and after heat treatment under the experimental conditions of Example 4. Figure (a) shows the sample before heat treatment, and figure (b) shows the sample after heat treatment. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the present application will be described clearly and completely below in conjunction with the embodiments of the present application, with the purpose of showing the feasibility and effectiveness of the method described in the present application.

[0038] Example 1

[0039] In this embodiment, the titanium metal is of TA1 grade, and the in-situ preparation method for generating a red ceramic film layer through phase transition is as follows:

[0040] S1, titanium metal surface pretreatment: the sample is ultrasonically cleaned in anhydrous ethanol for 5 minutes to remove surface oil and residual substances, washed with deionized water and then dried in an oven.

[0041] S2, preparation of micro-arc oxidation electrolyte: the electrolyte is composed of the following components:

[0042] Sodium silicate: 12 g / L;

[0043] Sodium hexametaphosphate: 6 g / L;

[0044] Sodium hydroxide: 1 g / L;

[0045] Ferric citrate: 4 g / L;

[0046] Potassium ferricyanide: 2 g / L;

[0047] The rest is deionized water.

[0048] S3, micro-arc oxidation experiment: the pretreated sample is used as the anode of the micro-arc oxidation power supply, and high-purity graphite sheet (purity 99.9wt%) is used as the cathode to prepare a black ceramic film layer. The micro-arc oxidation parameters are as follows:

[0049] Micro-arc oxidation time: 10 minutes;

[0050] Current density of monopole output full-reverse direct current pulse power supply: 5 A / dm 2 ;​

[0051] Electrolyte temperature: 20℃;

[0052] Frequency: 800Hz;

[0053] Duty cycle: 8%.

[0054] S4, drying treatment, the sample after micro-arc oxidation was cleaned by ultrasonic wave for 10 min, and was naturally air-dried.

[0055] S5, heat treatment experiment, the titanium metal plate with black ceramic film layer after micro-arc oxidation was put into a tubular heat treatment furnace, the furnace temperature was adjusted to 600℃ and the temperature was kept for 8h. During the whole heat treatment process, air atmosphere was kept, and the titanium metal plate was heated by heat convection. After the heat treatment was completed, the furnace temperature was gradually reduced to room temperature, and then the titanium metal plate was taken out, and a red ceramic film layer was obtained.

[0056] Example 2

[0057] In this embodiment, the titanium metal brand is TA1, and the in-situ preparation method of phase transition induced red ceramic film layer is as follows:

[0058] S1, titanium metal surface pretreatment, the sample was ultrasonically cleaned in anhydrous ethanol for 5 min to remove surface oil stains and residual substances, washed with deionized water and dried in an oven.

[0059] S2, preparation of micro-arc oxidation electrolyte, the electrolyte is composed of the following components:

[0060] Sodium silicate: 12g / L;

[0061] Sodium hexametaphosphate: 6g / L;

[0062] Sodium hydroxide: 1g / L;

[0063] Ferric citrate: 6g / L;

[0064] Potassium ferricyanide: 4g / L;

[0065] The rest is deionized water.

[0066] S3, micro-arc oxidation experiment, the pretreated sample was used as the anode of the micro-arc oxidation power supply, high-purity graphite sheet (purity 99.9wt%) was used as the cathode to prepare black ceramic film layer, and the micro-arc oxidation parameters were as follows:

[0067] Micro-arc oxidation time: 10min;

[0068] Current density of monopole output full reverse direct current pulse power supply: 5A / dm 2 ;

[0069] Electrolyte temperature: 20℃;

[0070] Frequency: 800Hz;

[0071] Duty cycle: 8%.

[0072] S4, drying treatment, the sample after micro-arc oxidation was cleaned by ultrasonic wave for 10 min, and naturally air-dried.

[0073] S5, heat treatment experiment, the black ceramic film layer titanium metal plate after micro-arc oxidation was put into a tubular heat treatment furnace, the furnace temperature was adjusted to 600℃ and kept at this temperature for 8 hours. During the whole heat treatment process, the air atmosphere was kept, and the titanium metal plate was heated by heat convection. After heat treatment, the furnace temperature was gradually reduced to room temperature, and then the titanium metal plate was taken out, and a red ceramic film layer was obtained.

[0074] Example 3

[0075] In this embodiment, the titanium metal brand is TA1, and the in-situ preparation method of the red ceramic film layer generated by phase transition induction is as follows:

[0076] S1, titanium metal surface pretreatment, the sample was ultrasonically cleaned in anhydrous ethanol for 5 min to remove surface oil stains and residual substances, washed with deionized water and dried in an oven.

[0077] S2, preparation of micro-arc oxidation electrolyte, the electrolyte is composed of the following components:

[0078] Sodium silicate: 12g / L;

[0079] Sodium hexametaphosphate: 6g / L;

[0080] Sodium hydroxide: 1g / L;

[0081] Iron citrate: 8g / L;

[0082] Potassium ferricyanide: 6g / L;

[0083] The rest is deionized water.

[0084] S3, micro-arc oxidation experiment, the pretreated sample was used as the anode of the micro-arc oxidation power supply, high-purity graphite sheet (purity 99.9wt%) was used as the cathode to prepare a black ceramic film layer, and the micro-arc oxidation parameters were as follows:

[0085] Micro-arc oxidation time: 10min;

[0086] Current density of monopole output full reverse direct current pulse power supply: 5A / dm 2 ;

[0087] Electrolyte temperature: 20℃;

[0088] Frequency: 800 Hz;

[0089] Duty cycle: 8%.

[0090] S4, drying treatment, the sample after micro-arc oxidation was cleaned by ultrasonic wave for 10 min, and naturally air dried.

[0091] S5, heat treatment experiment, the black ceramic film layer of the titanium metal plate after micro-arc oxidation was placed in a tubular heat treatment furnace, the furnace temperature was adjusted to 600℃ and kept at this temperature for 8 hours. During the whole heat treatment process, the air atmosphere was kept, and the titanium metal plate was heated by heat convection. After the heat treatment was completed, the furnace temperature was gradually reduced to room temperature, and then the titanium metal plate was taken out, and a red ceramic film layer was obtained.

[0092] Example 4

[0093] In this embodiment, the titanium metal brand is TA1, and the in-situ preparation method of the red ceramic film layer generated by phase transition induction is as follows:

[0094] S1, titanium metal surface pretreatment, the sample was ultrasonically cleaned in anhydrous ethanol for 5 min to remove surface oil stains and residual substances, washed with deionized water and dried in an oven.

[0095] S2, preparation of micro-arc oxidation electrolyte, the electrolyte is composed of the following components:

[0096] Sodium silicate: 12 g / L;

[0097] Sodium hexametaphosphate: 6 g / L;

[0098] Sodium hydroxide: 1 g / L;

[0099] Ferric citrate: 10 g / L;

[0100] Potassium ferricyanide: 8 g / L;

[0101] The rest is deionized water.

[0102] S3, micro-arc oxidation experiment, the pretreated sample was used as the anode of the micro-arc oxidation power supply, high-purity graphite sheet (purity 99.9 wt%) was used as the cathode to prepare a black ceramic film layer, and the micro-arc oxidation parameters were as follows:

[0103] Micro-arc oxidation time: 10 min;

[0104] Current density of monopole output full reverse direct current pulse power supply: 5 A / dm 2 ;

[0105] Electrolyte temperature: 20℃;

[0106] Frequency: 800 Hz;

[0107] Duty cycle: 8%.

[0108] S4. Drying treatment: The sample after micro-arc oxidation is ultrasonically cleaned for 10 minutes and then air-dried naturally.

[0109] S5. Heat treatment experiment: The titanium metal plate with the black ceramic film layer after micro-arc oxidation was placed in a tubular heat treatment furnace, and the furnace temperature was adjusted to 600℃ and maintained at this temperature for 8 hours. Throughout the heat treatment process, an air atmosphere was maintained, and the titanium metal plate was heated by thermal convection. After the heat treatment was completed, the furnace temperature was gradually reduced to room temperature, and then the titanium metal plate was removed, yielding a red ceramic film layer.

[0110] The steps, materials, and parameters shown in this embodiment are merely examples and can be adjusted appropriately according to requirements in actual applications.

[0111] The performance analysis of each embodiment is as follows:

[0112] like Figure 1 As shown in the macroscopic morphology images of the titanium black ceramic film after micro-arc oxidation in Examples 1-4, a uniform black ceramic film layer was successfully formed on the surface of titanium metal after micro-arc oxidation.

[0113] like Figure 2 As shown in the macroscopic morphology images of the titanium red ceramic film after heat treatment in Examples 1-4, it can be seen that under the heat treatment condition of 600℃, the black ceramic film layer after micro-arc oxidation underwent a significant color change, transforming into a uniform and glossy red ceramic film layer, which has a good aesthetic effect.

[0114] like Figure 3 As shown in the 1000x magnification micrograph of the ceramic film after micro-arc oxidation and heat treatment in Example 4, the surface morphology of the red ceramic film prepared by the present invention is relatively dense with fewer pores, which improves the corrosion resistance of the film.

[0115] like Figure 4 As shown in the figure, the EDS elemental content analysis of the ceramic film after micro-arc oxidation and heat treatment in Example 4 shows that silicon mainly comes from sodium silicate, which is the main component of film formation; P mainly comes from sodium hexametaphosphate, which plays an auxiliary role in film formation; Fe mainly comes from colorants ferric citrate and potassium ferricyanide; Ti mainly comes from the TiO2 film layer generated during micro-arc oxidation. The high content of Fe and Ti indicates that the film layer is mainly a TiO2 film layer containing Fe oxides. The Fe-containing phase is the main color phase, and its content affects the color value of the film layer and the color saturation of the red ceramic film layer.

[0116] like Figure 5As shown in the XRD phase analysis diagrams of the ceramic films after micro-arc oxidation and heat treatment in Example 4, the black ceramic layer after titanium micro-arc oxidation is mainly composed of TiO2 (anatase and rutile) and Fe3O4. Fe3O4 is the main color phase of the black film. After heat treatment, some Fe3O4 is converted into Fe2O3, becoming the main color phase of the red ceramic film. This indicates that under appropriate heat treatment temperature and time conditions, the film layer underwent significant phase transformation and crystal structure reorganization, thus achieving a successful color change from black to red.

[0117] like Figure 6 As shown in the UV-Vis absorption curves of the ceramic films after micro-arc oxidation and heat treatment in Example 4, the black ceramic layer after micro-arc oxidation exhibits strong absorption characteristics in the UV-Vis light range of 225 nm to 800 nm; the red ceramic film after heat treatment shows significant absorption in the visible light range of 200 nm to 622 nm, while a significant absorption trough appears in the red band of 622 nm to 760 nm. This result indicates that the heat treatment process optimizes the absorption characteristics of the film for visible light, achieving the transformation of the film from black to red.

[0118] like Figure 7 As shown, the potentiodynamic polarization curves obtained by immersing the ceramic film after micro-arc oxidation and heat treatment in a 3.5 wt% NaCl aqueous solution for 30 min in Example 4 show that the red ceramic film after heat treatment exhibits superior corrosion resistance compared to the black ceramic film after micro-arc oxidation. That is, the corrosion rate of the red ceramic film is significantly lower than that of the black ceramic film without heat treatment.

[0119] The properties of the titanium red ceramic films prepared in each embodiment are shown in Table 1 below:

[0120] Table 1. Thickness, hardness, relative atomic content of Fe, and corresponding colorimetric values ​​of titanium-ceramic films.

[0121]

[0122] As can be seen from Table 1, the chroma value (a*) of the red ceramic film layer prepared in all examples is in the range of 5-15, and the red saturation of the film layer gradually increases with the increase of the concentration of the colorant. This indicates that the method of the present application can realize uniform coloring of the red ceramic film layer, and the color is uniform and consistent. By adjusting the concentration of ferric citrate and potassium ferricyanide in the electrolyte, the depth of the red ceramic film layer can be controlled. For example, in Example 1, the concentration of ferric citrate and potassium ferricyanide is low, the chroma value is 5, and the color is light; while in Example 4, the concentration is high, the chroma value is 15, and the color is deep. Table 1 shows that the thickness of the red ceramic film layer prepared in different examples is between 10-13 μm, and the thickness of the film layer slightly increases with the increase of the concentration of the colorant in the electrolyte. This indicates that by adjusting the electrolyte composition and process parameters, the thickness of the film layer can be effectively controlled to meet the requirements of different application scenarios for the thickness of the film layer. The hardness of the red ceramic film layer prepared in each example is between 501-534 HV, showing a high hardness level. High hardness means that the film layer has good wear resistance and scratch resistance, which can effectively protect the titanium metal substrate and prolong its service life. The relative atomic content of Fe in Table 1 shows that the atomic content of Fe in the red ceramic film layer is between 10%-25%, which is closely related to the corrosion resistance of the film layer. By comparing the black ceramic film layer after micro-arc oxidation (high corrosion rate), the corrosion rate of the red ceramic film layer in 3.5wt% NaCl solution is significantly reduced, indicating that its corrosion resistance is significantly improved. This corrosion resistance improvement not only enhances the protection performance of titanium metal, but also widens its application range in harsh environments. In addition, the L* value reflects the brightness difference of the black ceramic film layer in different examples, and the lower the value, the darker the color of the black ceramic film layer, the closer to pure black.

[0123] As Figure 8 shown, the macroscopic morphology of the sample before and after micro-arc oxidation and heat treatment under the experimental conditions of Example 4 can be seen that the present application combines micro-arc oxidation and heat treatment process and has no limitation on the geometric shape and size of the sample. Irregularly shaped samples can be processed. This is particularly important for many aerospace, medical devices and other industries with complex shapes and high requirements for components.

[0124] The technical advantages of the present application are summarized as follows:

[0125] The present application successfully prepares a new type of red ceramic film layer on the surface of titanium metal by combining micro-arc oxidation and heat treatment process. The experimental results show that:

[0126] (1) Color performance: uniform and lustrous color change from black to red is achieved, significantly improving the appearance and decorative effect of the product;

[0127] (2) Microstructure: The film layer has high compactness and few pores, effectively improving the mechanical strength and corrosion resistance;

[0128] (3) Composition and phase state: By the action of Fe salt colorant and in combination with the heat treatment process, the red ceramic film layer with Fe2O3 as the main color-developing phase is successfully realized, and the optical absorption characteristics are optimized;

[0129] (4) Corrosion resistance: After the immersion test in the 3.5wt% NaCl aqueous solution, the red ceramic film layer exhibits significantly better corrosion resistance than the black ceramic film layer. The corrosion resistance indexes of the red ceramic film layer are as follows: corrosion potential E corr : -0.25~0.25V; corrosion current density: 8x10 -6 ~5x10 -5 A·cm -2 ; hardness: 400~600HV.

[0130] The above experimental results fully prove the effectiveness and superiority of the preparation process of the present application, and provide a new technical path for the application of titanium metal in the decoration and functional fields.

[0131] The above is only a specific implementation in the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered in the inclusive scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An in-situ preparation method for a red ceramic film layer induced by phase transformation on a titanium metal surface, characterized in that, Includes the following steps: S1. Titanium metal surface pretreatment: Ultrasonic cleaning of titanium metal in anhydrous ethanol for 4-6 minutes to remove surface oil and residues, followed by washing with deionized water and drying in an oven. S2. Prepare the micro-arc oxidation electrolyte, which consists of the following components: sodium silicate 0.5 g / L to 50 g / L; sodium hexametaphosphate 0.5 g / L to 50 g / L; sodium hydroxide 1 g / L to 100 g / L; colorant 1 is ferric citrate 1 g / L to 100 g / L; colorant 2 is potassium ferricyanide 1 g / L to 100 g / L; the remainder is deionized water. S3. Micro-arc oxidation: Pretreated titanium metal is used as the anode of the micro-arc oxidation power supply, and high-purity graphite sheet is used as the cathode. Micro-arc oxidation is carried out in an electrolyte to prepare a black ceramic film. The micro-arc oxidation parameters are as follows: micro-arc oxidation time 5 min to 100 min; current density of the monopole output fully reverse DC pulse power supply 1 A / dm³. 2 ~50A / dm 2 Electrolyte temperature: 5–50℃; Frequency: 50Hz–2000Hz; Duty cycle: 1%–50%; S4. Drying treatment: Ultrasonic cleaning of the micro-arc oxidized titanium metal for 2 min to 50 min, and then air drying. S5. Heat treatment: The micro-arc oxidized titanium metal is placed in a tube heat treatment furnace for annealing and then air-cooled to room temperature to obtain a red ceramic film.

2. The in-situ preparation method for generating a red ceramic film on a titanium metal surface by phase transformation induction according to claim 1, characterized in that, In step S5, the heat treatment is carried out in an air atmosphere, with a holding temperature of 400-1000℃ and a holding time of 1-1000h.

3. The in-situ preparation method for generating a red ceramic film on a titanium metal surface via phase transformation induction according to claim 2, characterized in that, In step S5, preferably, the heat treatment holding temperature is 500-700℃ and the holding time is 5-50h.

4. The in-situ preparation method for generating a red ceramic film on a titanium metal surface by phase transformation induction according to claim 1, characterized in that, The obtained red ceramic film has the following performance indicators: the thickness of the red ceramic film is 1-50 μm; the phase composition of the red ceramic film includes TiO2 and Fe2O3, with Fe2O3 distributed in the TiO2 support, and Fe2O3 being the color phase of the red ceramic film.

5. The in-situ preparation method for generating a red ceramic film on a titanium metal surface via phase transformation induction according to claim 4, characterized in that, In the red ceramic film, the atomic content of Fe is 1% to 30%.

6. The in-situ preparation method for generating a red ceramic film on a titanium metal surface by phase transformation induction according to claim 4, characterized in that, The chromaticity value of the red ceramic film layer: a*: 0~20, a* represents the red chromaticity: green (-128)~red (+128).

7. The in-situ preparation method for generating a red ceramic film on a titanium metal surface via phase transformation induced according to claim 6, characterized in that, Preferably, the chromaticity value of the red ceramic film layer is a*: 5~15.

8. The in-situ preparation method for generating a red ceramic film on a titanium metal surface by phase transformation induction according to claim 1, characterized in that, The corrosion resistance properties of the red ceramic film are as follows: corrosion potential E corr -0.25~0.25V; Corrosion current density: 8×10 -6 ~5×10 -5 A·cm -2 ; Hardness: 400~600HV.

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