Preparation method of white ceramic coating on titanium alloy surface and white ceramic coating

Abstract

The present disclosure provides a method for preparing a white ceramic coating on a titanium alloy surface and a white ceramic coating, and relates to the technical field of titanium alloy surfaces, and comprises the following steps: mechanically polishing a titanium alloy sample to obtain a polished titanium alloy sample; performing ion nitriding treatment on the polished titanium alloy sample to prepare an ion nitriding layer; the ion nitriding layer only comprises a diffusion layer; and performing micro-arc oxidation treatment on the titanium alloy sample comprising the ion nitriding layer to prepare a white ceramic coating. The present disclosure can prepare a white ceramic coating with high reflectivity.

Description

Technical Field

[0001] This disclosure relates to the field of titanium alloy surface technology, and more specifically, to a method for preparing a white ceramic coating on a titanium alloy surface and the white ceramic coating itself. Background Technology

[0002] Titanium alloys are widely used in the manufacture of housings for aerospace and electronic products due to their high specific strength, good corrosion resistance, and good heat resistance. The external components of these products require coatings with specific thermophysical properties to control and regulate heat exchange between the product and the outside world, and to prevent heat accumulation during long-term service. The most common type of coating is a white ceramic coating with low absorption and high reflectivity.

[0003] In related technologies, methods for preparing white ceramic coatings include coating methods and micro-arc oxidation methods. White ceramic coatings prepared by coating methods are prone to aging and failure under prolonged sunlight exposure, extreme temperatures, and atomic oxygen environments. Films prepared on titanium alloy surfaces using micro-arc oxidation methods are typically gray and have low surface reflectivity. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing a white ceramic coating on a titanium alloy surface and the white ceramic coating itself, thereby overcoming, to some extent, the problems of easy failure of the white ceramic coating and low surface reflectivity caused by the limitations and defects of related technologies.

[0005] According to one aspect of this disclosure, a method for preparing a white ceramic coating on a titanium alloy surface is provided, comprising: mechanically grinding a titanium alloy sample to obtain a ground titanium alloy sample; subjecting the ground titanium alloy sample to ion nitriding treatment to prepare an ion nitriding layer; the ion nitriding layer comprising only a diffusion layer; and subjecting the titanium alloy sample comprising the ion nitriding layer to micro-arc oxidation treatment to prepare a white ceramic coating.

[0006] In one exemplary embodiment of this disclosure, the holding temperature for ion nitriding treatment is 600~700℃, and the holding time is 4~8 h.

[0007] In one exemplary embodiment of this disclosure, the voltage of the ion nitriding treatment is 600~800V, the nitrogen gas integral is 30%~60%, the argon gas integral is 40%~70%, and the furnace pressure is 200~300 Pa.

[0008] In one exemplary embodiment of this disclosure, the ion nitriding layer contains only a diffusion layer and no compound layer, and the thickness of the ion nitriding layer is 30~70 μm.

[0009] In one exemplary embodiment of this disclosure, the electrolyte for micro-arc oxidation treatment comprises the following components: 20-30 g / L sodium silicate, 20-30 g / L sodium hydroxide, 24-37 g / L zinc hydroxide, and 5-10 g / L diethylenetriaminepentaacetic acid.

[0010] In one exemplary embodiment of this disclosure, the concentration ratio of sodium hydroxide to zinc hydroxide is not less than 2:1.

[0011] In one exemplary embodiment of this disclosure, the current density of the micro-arc oxidation treatment is 4~6 A / dm³. 2 The frequency is 500~2000 Hz and the duty cycle is 10~30%.

[0012] In one exemplary embodiment of this disclosure, the processing time for micro-arc oxidation is 10 to 30 minutes.

[0013] In one exemplary embodiment of this disclosure, the white ceramic coating comprises rutile TiO2 and ZnO, and the coating thickness is 5 to 20 μm.

[0014] According to one aspect of this disclosure, a white ceramic coating is provided, which is prepared by the method described above for preparing a white ceramic coating on a titanium alloy surface.

[0015] In the technical solution provided in this embodiment, by performing ion nitriding treatment on the polished titanium alloy sample, an ion nitriding layer consisting only of a nitrogen-containing solid solution and excluding a compound layer is prepared. During the micro-arc oxidation process, the nitrogen-containing solid solution on the surface of the titanium alloy can form a white ceramic film without the generation of other titanium oxide impurity phases, thereby generating a white ceramic coating with high reflectivity, improving surface reflectivity, avoiding the problem of easy aging and failure, and improving the anti-aging performance and oxidation resistance of the white ceramic coating on the surface of the titanium alloy. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure. It is obvious that the drawings described below are merely some embodiments of this disclosure, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0017] Figure 1 The flowchart illustrates a method for preparing a white ceramic coating on a titanium alloy surface according to an embodiment of the present disclosure.

[0018] Figure 2 The cross-sectional morphology is shown in Example 1 for the titanium alloy ion-nitrided layer.

[0019] Figure 3 The image shows the surface macromorphology of the white micro-arc oxide layer of titanium alloy obtained according to Example 1.

[0020] Figure 4 The surface microstructure of the white micro-arc oxide layer of titanium alloy obtained according to Example 1 is shown.

[0021] Figure 5 The cross-sectional microstructure of the white micro-arc oxide layer of titanium alloy obtained according to Example 1 is shown.

[0022] Figure 6 The XRD pattern of the white micro-arc oxide layer of titanium alloy obtained in Example 1.

[0023] Figure 7 The cross-sectional morphology is shown in Comparative Example 1 for the titanium alloy ion-nitrided layer.

[0024] Figure 8 The macroscopic surface morphology of the titanium alloy micro-arc oxide layer prepared in Comparative Example 1 is shown.

[0025] Figure 9 The surface microstructure of the titanium alloy micro-arc oxide layer prepared in Comparative Example 1 is shown.

[0026] Figure 10 The cross-sectional microstructure of the titanium alloy micro-arc oxide layer prepared in Comparative Example 1 is shown.

[0027] Figure 11 XRD pattern of the titanium alloy micro-arc oxidation layer prepared in Comparative Example 1.

[0028] Figure 12 This is a comparison diagram of the reflectance of the micro-arc oxidation layers prepared in Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0029] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided to make this disclosure more comprehensive and complete, and to fully convey the concept of the example embodiments to those skilled in the art. The described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a full understanding of embodiments of this disclosure. However, those skilled in the art will recognize that the technical solutions of this disclosure can be practiced with one or more of the specific details omitted, or other methods, components, apparatus, steps, etc., can be employed. In other instances, well-known technical solutions are not shown or described in detail to avoid obscuring various aspects of this disclosure.

[0030] The terms “a,” “an,” “the,” and “the” are used in this specification to indicate the presence of one or more elements / components, etc.; the terms “including” and “having” are used to indicate an open-ended inclusion and to mean that there may be other elements / components, etc., in addition to those listed; the terms “first” and “second” are used only as markings and are not a limitation on the number of objects.

[0031] In related technologies, white ceramic coatings prepared by coating methods are prone to aging and failure under prolonged sunlight radiation, extreme temperatures, and atomic oxygen environments. Meanwhile, films prepared on titanium alloy surfaces using micro-arc oxidation are typically gray with low surface reflectivity. Therefore, preparing high-reflectivity white ceramic coatings on titanium alloy surfaces to reduce heat absorption is of great significance for broadening the applications of titanium alloy products.

[0032] Based on this, this disclosure provides a method for preparing a white ceramic coating on a titanium alloy surface, solving the technical problems of easy failure of white ceramic coatings prepared by coating methods and low surface reflectivity of films prepared by micro-arc oxidation methods. (Reference) Figure 1 As shown, the method for preparing the white ceramic coating on the surface of the titanium alloy mainly includes the following steps:

[0033] In step S110, the titanium alloy sample is mechanically polished to obtain the polished titanium alloy sample.

[0034] In step S120, the polished titanium alloy sample is subjected to ion nitriding treatment to prepare an ion nitriding layer; the ion nitriding layer only contains a diffusion layer.

[0035] In step S130, the titanium alloy sample containing the ion nitriding layer is subjected to micro-arc oxidation treatment to prepare a white ceramic coating.

[0036] Next, the preparation method of the white ceramic coating on the titanium alloy surface in the embodiments of this disclosure will be described in detail.

[0037] In step S110, the titanium alloy sample is mechanically polished to obtain the polished titanium alloy sample.

[0038] In this embodiment, the titanium alloy sample can be any type of titanium alloy, such as a TC4 titanium alloy sample or a TA2 titanium alloy sample. Mechanical polishing can be performed using sandpaper or other polishing methods to remove the oxide film on the surface of the titanium alloy sample. The polished titanium alloy sample is obtained by mechanically polishing the sample.

[0039] In step S120, the polished titanium alloy sample is subjected to ion nitriding treatment to prepare an ion nitriding layer; the ion nitriding layer only contains a diffusion layer.

[0040] In this embodiment of the disclosure, the ion nitriding treatment may involve introducing nitrogen and argon gas into an ion nitriding furnace to generate a titanium alloy ion nitrided layer on the surface of the titanium alloy sample.

[0041] Ion nitriding treatment includes the following steps: 1. Clean the surface of the titanium alloy workpiece; 2. Load the cleaned titanium alloy sample into the ion nitriding furnace, set the process parameters such as voltage, furnace pressure, holding temperature, holding time, nitrogen gas integral, and argon gas integral, and start the ion nitriding furnace; 3. Hold the sample at the holding temperature until the holding time is reached, and then let it cool to room temperature before opening the furnace and taking it out.

[0042] The holding temperature for ion nitriding is 600~700℃, and the holding time is 4~8 h. The voltage for ion nitriding is 600~800V, the nitrogen gas fraction is 30%~60%, the argon gas fraction is 40%~70%, and the furnace pressure is 200~300 Pa. Nitrogen and argon are introduced simultaneously according to the above volume fractions.

[0043] Ion nitriding treatment of polished titanium alloy samples can produce an ion-nitrided layer containing only a diffusion layer and no compound layer. The diffusion layer can be a nitrogen-containing solid solution. The thickness of the prepared ion-nitrided layer is 30–70 μm.

[0044] An ion-nitrided layer containing only a diffusion layer is prepared by ion nitriding treatment. This ion-nitrided layer affects the color of the micro-arc oxidation layer to white during the micro-arc oxidation process.

[0045] In this embodiment, a holding temperature lower than that used for ion nitriding of titanium alloys and a nitrogen concentration expressed as a nitrogen gas integral number are selected for ion nitriding treatment. This controls the concentration of nitrogen atoms in the titanium alloy matrix to always be below the solid solution limit of α-Ti, avoiding the nucleation and growth of nitride phases such as TiN and Ti2N. Nitrogen atoms diffuse more easily into the interior of the titanium alloy matrix as interstitial atoms, thus forming only a diffusion layer containing nitrogen solid solution and avoiding the formation of a compound layer. Since only a diffusion layer containing nitrogen solid solution is formed, the nitrogen solid solution on the surface of the titanium alloy can form a white ceramic film layer composed of a single rutile TiO2 during the micro-arc oxidation process, without the generation of other titanium oxide impurity phases. Therefore, conditions are created for the formation of the white ceramic coating represented by the white micro-arc oxidation layer.

[0046] In step S130, the titanium alloy sample containing the ion nitriding layer is subjected to micro-arc oxidation treatment to prepare a white ceramic coating.

[0047] In this embodiment, the titanium alloy sample containing the ion-nitrided layer refers to the titanium alloy sample after ion nitriding. Micro-arc oxidation treatment involves applying a high-voltage electric field in the electrolyte to induce micro-arc discharge on the surface of the titanium alloy sample. Utilizing the high-temperature and high-pressure environment generated by the discharge, the titanium alloy sample undergoes physicochemical reactions such as oxidation, melting, and sintering with the electrolyte components, ultimately forming a micro-arc oxidation layer. This micro-arc oxidation layer is a white ceramic coating. The electrolyte for micro-arc oxidation treatment includes the following components: 20-30 g / L sodium silicate, 20-30 g / L sodium hydroxide, 24-37 g / L zinc hydroxide, and 5-10 g / L diethylenetriaminepentaacetic acid (DTPA). Sodium silicate is the film-forming agent for micro-arc oxidation treatment; sodium hydroxide is the pH adjuster; zinc hydroxide forms zinc oxide during micro-arc oxidation treatment to improve surface reflectivity; and diethylenetriaminepentaacetic acid (DTPA) is a chelating agent to prevent the formation of zinc hydroxide precipitate during the reaction.

[0048] The concentration ratio of sodium hydroxide to zinc hydroxide in the electrolyte needs to be greater than or equal to 2:1. Zinc hydroxide is an amphoteric hydroxide that can only dissolve under strongly alkaline conditions. If the concentration ratio of sodium hydroxide to zinc hydroxide is less than 2:1, zinc hydroxide may not dissolve in the electrolyte, and zinc oxide will not be formed during the micro-arc oxidation process. The resulting micro-arc oxidation layer may not contain ZnO, resulting in a lower surface reflectivity.

[0049] Micro-arc oxidation can be performed using a pulsed DC power supply, with a current density of 4~6 A / dm³. 2 The frequency is 500~2000 Hz, and the duty cycle is 10~30%. The processing time for micro-arc oxidation is 10~30 min. The micro-arc oxidation process yields a micro-arc oxide layer, which refers to a white ceramic coating.

[0050] In this embodiment, the principle that the amphoteric hydroxide Zn(OH)2 can dissolve in a strongly alkaline solution to form a soluble zincate is utilized, combined with the fact that the anion of the chelating agent represented by diethylenetriaminepentaacetic acid (DTPA) can react with Zn 2+ The formation of stable soluble complex salts inhibits the formation of Zn(OH)2 precipitate during micro-arc oxidation. The high-temperature sintering effect generated by micro-arc oxidation micropore discharge promotes the conversion of soluble zincates and zinc-containing complex salts into ZnO. This avoids the problems of particle precipitation, poor dispersibility, and low ZnO incorporation in the micro-arc oxidation layer preparation method, which is often encountered when adding ZnO particles. Furthermore, the introduction of the high-reflectivity ZnO phase into the micro-arc oxidation layer helps to improve its surface reflectivity. The reaction principle is as follows:

[0051] Zn(OH)₂ + 2NaOH = Na₂ZnO₂ + 2H₂O

[0052] Na₂ZnO₂=ZnO+2Na₂O

[0053] In this embodiment, an ion-nitrided layer containing only a diffusion layer is prepared by ion-nitriding a polished titanium alloy sample. After micro-arc oxidation, a white ceramic coating can be obtained. Since the white ceramic coating has a higher reflectivity than other colored ceramic coatings, and ZnO is formed in the micro-arc oxidation layer obtained by micro-arc oxidation, a high-reflectivity white ceramic coating can be prepared on the titanium alloy surface, avoiding the problem of aging failure and improving reliability.

[0054] The preparation method described in this disclosure is applicable to various types of titanium alloys. The main components of the prepared white ceramic coating are crystalline rutile TiO2 and ZnO. The prepared white ceramic coating exhibits a surface reflectance of over 85% in the visible light region (400-760 nm), providing a new pathway for the integrated modification of the appearance and function of titanium alloy surfaces. This method is particularly suitable for applications in aerospace and electronic devices where a white appearance, high reflectivity, and excellent thermal control performance are required.

[0055] Next, the preparation method of the white ceramic coating on the surface of titanium alloy provided in this disclosure will be described in detail with reference to the embodiments.

[0056] Example 1

[0057] Step 1: Polish the surface of the TC4 titanium alloy sample with sandpaper to obtain the polished TC4 titanium alloy sample. Rinse it with tap water and blow it dry.

[0058] Step 2: The polished TC4 titanium alloy sample is subjected to ion nitriding treatment. The holding temperature for ion nitriding is 700℃, the holding time is 8 h, the voltage is 800 V, the nitrogen gas component is 60%, the argon gas component is 40%, and the furnace pressure is 300 Pa. After the holding process is completed, the polished TC4 titanium alloy sample is cooled to room temperature and then removed to obtain the ion-nitrided layer. The ion-nitrided layer contains only the diffusion layer and does not contain the compound layer.

[0059] Figure 2 The cross-sectional morphology of the ion-nitrided layer on the surface of the titanium alloy sample obtained in Example 1 shows that the titanium alloy nitrided layer structure did not undergo obvious phase transformation, and there was no compound layer (i.e., white bright layer) on the surface. Since the heat preservation temperature was 700℃, it did not reach the temperature for forming the TiN compound layer. Nitrogen atoms mainly existed in the titanium alloy matrix in a solid solution state. The thickness of the ion-nitrided layer prepared in Example 1 was determined to be 70 μm by hardness method.

[0060] Step 3: The TC4 titanium alloy sample containing the ion-nitrided layer was subjected to micro-arc oxidation treatment to obtain a white micro-arc oxide layer as a white ceramic coating. The electrolyte for micro-arc oxidation treatment consisted of 30 g / L sodium silicate, 20 g / L sodium hydroxide, 24 g / L zinc hydroxide, and 5 g / L diethylenetriaminepentaacetic acid (DTPA). The current density for micro-arc oxidation treatment was 6 A / dm³. 2 The frequency was 2000 Hz, the duty cycle was 30%, and the micro-arc oxidation treatment time was 30 min.

[0061] The principle behind obtaining a white micro-arc oxide layer by doping a certain amount of nitrogen onto the surface of a titanium alloy and then performing micro-arc oxidation is that nitrogen reduces the absorption of incident light through phase regulation and defect suppression, while simultaneously introducing the highly reflective ZnO phase, thereby further improving reflectivity in the visible light range. Phase regulation allows for the formation of a single rutile TiO2, inhibiting the formation of other titanium oxides. Defect suppression results in a smoother and denser white micro-arc oxide layer.

[0062] Figure 3 The surface macromorphology of the white ceramic coating, represented by the white micro-arc oxide layer of titanium alloy, is as follows: Figure 3 The surface appears white.

[0063] Figure 4 The surface microstructure of the white micro-arc oxide layer on titanium alloy is shown. Figure 4 It can be seen that the surface is relatively smooth, and there are nanoscale particles around the pores.

[0064] Figure 5 The cross-sectional microstructure of the white micro-arc oxide layer on titanium alloy is shown. Figure 5 It can be seen that the film is relatively dense, with a thickness of 20 μm.

[0065] Figure 6 The XRD pattern of the white micro-arc oxide layer on titanium alloy is shown. Figure 6 It can be seen that the white ceramic coating is mainly composed of rutile TiO2 and ZnO, and the nano-sized particles around the pores should be ZnO. According to the test, the surface reflectance of the white ceramic coating represented by the white micro-arc oxide film is 91% in the visible light region with a wavelength of 400~760 nm.

[0066] Example 2

[0067] Step 1: Polish the surface of the TC4 titanium alloy sample with sandpaper to obtain the polished TC4 titanium alloy sample. Rinse it with tap water and blow it dry.

[0068] Step 2: The polished TC4 titanium alloy sample is subjected to ion nitriding treatment. The holding temperature is 600℃, the holding time is 4 h, the voltage is 600 V, the nitrogen gas integral is 30%, the argon gas integral is 70%, the furnace pressure is 200 Pa. After the holding process is completed, the polished TC4 titanium alloy sample is cooled to room temperature and then taken out to obtain an ion nitrided layer with a thickness of 30 μm and no compound layer.

[0069] Step 3: The TC4 titanium alloy sample containing the ion-nitrided layer after ion nitriding was subjected to micro-arc oxidation treatment. The electrolyte for micro-arc oxidation consisted of 20 g / L sodium silicate, 30 g / L sodium hydroxide, 37 g / L zinc hydroxide, and 10 g / L diethylenetriaminepentaacetic acid (DTPA). The current density for micro-arc oxidation treatment was 4 A / dm³. 2 The frequency was set at 1000 Hz, the duty cycle at 10%, and the micro-arc oxidation treatment time was 10 min. Based on this, a white micro-arc oxidation layer with a thickness of 5 μm and a surface reflectivity of 86% was obtained. This white micro-arc oxidation layer is a white ceramic coating.

[0070] Example 3

[0071] Step 1: Polish the surface of the TA2 titanium alloy sample with sandpaper to obtain the polished TA2 titanium alloy sample. Rinse it with tap water and blow it dry.

[0072] Step 2: The polished TA2 titanium alloy sample was subjected to ion nitriding treatment. The holding temperature for ion nitriding was 650℃, the holding time was 6 h, the voltage was 700 V, the nitrogen gas fraction was 50%, the argon gas fraction was 50%, and the furnace pressure was 250 Pa. After the holding process was completed, the polished TA2 titanium alloy sample was cooled to room temperature and then removed, yielding an ion-nitrided layer with a thickness of 50 μm and no compound layer. The ion-nitrided layer only contained a diffusion layer.

[0073] Step 3: The TA2 titanium alloy sample containing the ion-nitrided layer was subjected to micro-arc oxidation treatment to obtain a white micro-arc oxide layer as a white ceramic coating. The electrolyte for micro-arc oxidation treatment consisted of 25 g / L sodium silicate, 25 g / L sodium hydroxide, 30 g / L zinc hydroxide, and 8 g / L diethylenetriaminepentaacetic acid (DTPA). The current density for micro-arc oxidation treatment was 5 A / dm³. 2 The frequency was 1500 Hz, the duty cycle was 20%, and the micro-arc oxidation treatment time was 20 min. After micro-arc oxidation treatment, a white micro-arc oxidation layer with a thickness of 13 μm and a surface reflectivity of 88% was obtained. This white micro-arc oxidation layer is the white ceramic coating.

[0074] Comparative Example 1

[0075] Compared to Example 1, the specific parameters for ion nitriding treatment in Comparative Example 1 differed from those in Example 1. In Comparative Example 1, the holding temperature for ion nitriding treatment was 850°C, the nitrogen gas integral was 100%, argon gas was not introduced, and other operating steps were the same as in Example 1. Specifically, it included the following steps:

[0076] Step 1: Polish the surface of the TC4 titanium alloy sample with sandpaper to obtain the polished TC4 titanium alloy sample. Rinse it with tap water and blow it dry.

[0077] Step 2: Perform ion nitriding treatment on the polished TC4 titanium alloy sample. The holding temperature is 850℃, the holding time is 8 h, the voltage is 800 V, the nitrogen gas integral is 100%, no argon gas is introduced, the furnace pressure is 300 Pa, after the holding process is completed, wait for the polished TC4 titanium alloy sample to cool to room temperature and take it out to obtain the ion nitrided layer.

[0078] Step 3: The TC4 titanium alloy sample containing the ion-nitrided layer was subjected to micro-arc oxidation treatment to obtain a white micro-arc oxide layer as a white ceramic coating. The electrolyte for micro-arc oxidation treatment consisted of 30 g / L sodium silicate, 20 g / L sodium hydroxide, 24 g / L zinc hydroxide, and 5 g / L diethylenetriaminepentaacetic acid (DTPA). The current density for micro-arc oxidation treatment was 6 A / dm³. 2 The frequency is 2000 Hz, the duty cycle is 30%, and the processing time is 30 min.

[0079] Figure 7 The cross-sectional morphology of the titanium alloy ion-nitrided layer prepared in Comparative Example 1 is shown, where the thickness of the ion-nitrided layer is approximately 80.93 μm. Figure 7 It can be seen that there is a white bright layer with a thickness of about 10 μm on the top of the ion nitriding layer. This white bright layer is the compound layer. The main component of the titanium alloy white bright layer is TiN. At this time, nitrogen atoms not only exist in the matrix in a solid solution state, but also combine with titanium atoms on the surface to form TiN.

[0080] Figure 8 The image shows the macroscopic morphology of the micro-arc oxidation layer on titanium alloy. The surface is yellow, and a white micro-arc oxidation layer cannot be obtained. This is because TiN on the surface of titanium alloy still remains in the surface film after micro-arc oxidation treatment.

[0081] Figure 9 The microstructure of the titanium alloy micro-arc oxidation layer shows that the surface is relatively rough, and there are nano-sized particles around the pores, with a greater number of particles. This is because some TiN is oxidized to TiO2 during the micro-arc oxidation process.

[0082] Figure 10The cross-sectional microstructure of the titanium alloy micro-arc oxide layer is shown. Compared with Example 1, the thickness of the two is the same, which is 20 μm. However, the density of the titanium alloy micro-arc oxide layer prepared in Comparative Example 1 is lower than that of the micro-arc oxide layer provided in Example 1.

[0083] Figure 11 The XRD pattern of the titanium alloy micro-arc oxidation layer prepared in Comparative Example 1 is shown below. Figure 11 It can be seen that the TiO2 in the coating has two structures: rutile and anatase. In addition, diffraction peaks of ZnO and TiN are also present. Due to the greater number of voids and lower atomic packing density in the anatase titanium oxide lattice, its refraction and reflection of light are weaker than those of the rutile type. Tests showed that in the visible light region of 400–760 nm, the surface reflectance of this yellow micro-arc oxide film was only 75%. This surface reflectance is lower than that of the white micro-arc oxide layer prepared in Example 1.

[0084] Comparative Example 2

[0085] Compared to Example 1, Comparative Example 2 differs from Example 1 in that the titanium alloy sample in Comparative Example 2 is not subjected to ion nitriding treatment. The micro-arc oxide layer obtained in Comparative Example 2 is gray, and a white micro-arc oxide layer cannot be obtained. Specifically, the following steps are included:

[0086] Step 1: Polish the surface of the TC4 titanium alloy sample with sandpaper to obtain the polished TC4 titanium alloy sample. Rinse it with tap water and blow it dry.

[0087] Step 2: The polished TC4 titanium alloy sample was subjected to micro-arc oxidation treatment to obtain a gray micro-arc oxide layer. The electrolyte for micro-arc oxidation treatment consisted of 30 g / L sodium silicate, 20 g / L sodium hydroxide, 24 g / L zinc hydroxide, and 5 g / L diethylenetriaminepentaacetic acid (DTPA). The current density for micro-arc oxidation treatment was 6 A / dm³. 2 The frequency was 2000 Hz, the duty cycle was 30%, and the micro-arc oxidation treatment time was 30 min.

[0088] The surface reflectance of the prepared gray micro-arc oxide layer is 76%.

[0089] Comparative Example 3

[0090] Compared to Example 1, Comparative Example 3 differs from Example 1 in that the electrolyte in step three, the micro-arc oxidation treatment, does not contain zinc hydroxide and diethylenetriaminepentaacetic acid (DTPA), resulting in a white micro-arc oxidation layer. The main steps include:

[0091] Step 1: Polish the surface of the TC4 titanium alloy sample with sandpaper to obtain the polished TC4 titanium alloy sample. Rinse it with tap water and blow it dry.

[0092] Step 2: The polished TC4 titanium alloy sample is subjected to ion nitriding treatment. The holding temperature is 700℃, the holding time is 8 h, the voltage is 800 V, the nitrogen gas component is 60%, the argon gas component is 40%, and the furnace pressure is 300 Pa. After the holding process is completed, the polished TC4 titanium alloy sample is cooled to room temperature and then removed to obtain the ion nitrided layer. The ion nitrided layer only contains the diffusion layer and does not contain the compound layer.

[0093] Step 3: The TC4 titanium alloy sample containing the ion-nitrided layer was subjected to micro-arc oxidation treatment to obtain a white micro-arc oxide layer as a white ceramic coating. The electrolyte for micro-arc oxidation treatment consisted of 30 g / L sodium silicate and 20 g / L sodium hydroxide. The current density for micro-arc oxidation treatment was 6 A / dm³. 2 The frequency was 2000 Hz, the duty cycle was 30%, and the micro-arc oxidation treatment time was 30 min.

[0094] The surface reflectance of the white micro-arc oxide layer prepared in Comparative Example 3 was 84%. This comparison shows that the surface reflectance of the white micro-arc oxide layer prepared in Comparative Example 3 is lower than that of the white micro-arc oxide layer prepared in Example 1.

[0095] refer to Figure 12 As shown, the surface reflectance of the micro-arc oxidation layers prepared in Comparative Examples 1-3 is less than that of the white micro-arc oxidation layers prepared in Examples 1-3.

[0096] In this embodiment, during the ion nitriding treatment of the polished titanium alloy sample, a lower holding temperature and nitrogen concentration than those used in traditional titanium alloy ion nitriding are selected. This ensures that the concentration of nitrogen atoms in the titanium alloy matrix remains below the solid solution limit of α-Ti, preventing the nucleation and growth of nitride phases such as TiN and Ti2N. Nitrogen atoms diffuse more easily into the matrix as interstitial atoms, thus forming only a diffusion layer of nitrogen-containing solid solution and avoiding the formation of a compound layer. Furthermore, traditional micro-arc oxidation films of titanium alloys are often gray because they are not composed of a single TiO2 but rather a mixture of various titanium oxides. In some embodiments, the nitrogen-containing solid solution on the titanium alloy surface can form a white ceramic film layer composed of a single rutile TiO2 during micro-arc oxidation, without the generation of other titanium oxide impurity phases, thereby generating a white ceramic coating.

[0097] This method utilizes the principle that the amphoteric hydroxide Zn(OH)₂ dissolves in a strongly alkaline solution to form soluble zincates, and combines this with the ability of the chelating agent DTPA's anion to react with Zn. 2+ The formation of stable soluble complex salts inhibits the formation of Zn(OH)2 precipitation during micro-arc oxidation. The high-temperature sintering effect generated by micro-arc oxidation micropore discharge promotes the conversion of soluble zincates and zinc-containing complex salts into ZnO, avoiding the problems of particle precipitation, poor dispersibility, and low ZnO incorporation in traditional micro-arc oxidation layer preparation methods. The introduction of high-reflectivity ZnO into the micro-arc oxidation layer further enhances reflectivity. After micro-arc oxidation, the addition of nitrogen to the titanium alloy surface allows for the formation of a single rutile TiO2 through phase regulation, inhibiting the formation of other titanium oxides. This defect suppression results in a smoother and denser micro-arc oxidation layer, reducing the absorption of incident light. Simultaneously, the introduction of high-reflectivity ZnO further improves the surface reflectivity of the micro-arc oxidation layer in the visible light range. This avoids the aging and failure problems common in related technologies, increases the lifespan of the white ceramic coating on the titanium alloy surface, and improves the surface reflectivity of the white ceramic coating.

[0098] In this embodiment of the disclosure, a white ceramic coating is also provided. The coating thickness of the prepared white ceramic coating is 5~20 μm. The main components of the white ceramic coating are crystalline rutile TiO2 and ZnO. In the visible light region with a wavelength of 400~760 nm, the surface reflectivity of the white ceramic coating can reach more than 85%. This provides a new path for the integrated modification of the appearance and function of titanium alloy surfaces, and is especially suitable for aerospace, electronic devices and other fields that require white appearance, reflectivity and thermal control performance.

[0099] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of this disclosure and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0100] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the appended claims.

[0101] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A method for preparing a white ceramic coating on a titanium alloy surface, characterized in that, include: The titanium alloy sample was mechanically polished to obtain the polished titanium alloy sample. The polished titanium alloy sample was subjected to ion nitriding treatment to prepare an ion nitrided layer; the ion nitrided layer only contained a diffusion layer; the holding temperature of the ion nitriding treatment was 600~700℃, and the holding time was 4~8 h; the voltage of the ion nitriding treatment was 600~800V, the nitrogen gas fraction was 30%~60%, the argon gas fraction was 40%~70%, and the furnace pressure was 200~300 Pa; A white ceramic coating is prepared by micro-arc oxidation treatment of a titanium alloy sample containing an ion-nitrided layer; the electrolyte for the micro-arc oxidation treatment includes the following components: 20-30 g / L sodium silicate, 20-30 g / L sodium hydroxide, 24-37 g / L zinc hydroxide, and 5-10 g / L diethylenetriaminepentaacetic acid; the concentration ratio of sodium hydroxide to zinc hydroxide is not less than 2:

1.

2. The method for preparing a white ceramic coating on a titanium alloy surface according to claim 1, characterized in that, The ion nitriding layer contains only a diffusion layer and no compound layer, and the thickness of the ion nitriding layer is 30~70 μm.

3. The method for preparing a white ceramic coating on a titanium alloy surface according to claim 1, characterized in that, The current density of the micro-arc oxidation treatment is 4~6 A / dm. 2 The frequency is 500~2000 Hz and the duty cycle is 10~30%.

4. The method for preparing a white ceramic coating on a titanium alloy surface according to claim 1, characterized in that, The processing time for the micro-arc oxidation treatment is 10 to 30 minutes.

5. The method for preparing a white ceramic coating on a titanium alloy surface according to claim 1, characterized in that, The white ceramic coating comprises rutile TiO2 and ZnO, and the coating thickness is 5 ~ 20 μm.

6. A white ceramic coating, characterized in that, The white ceramic coating is prepared by the method for preparing a white ceramic coating on a titanium alloy surface as described in any one of claims 1-5.

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