Preparation method of a porous TiC coating

Abstract

The present invention relates to ceramic coating technology, and particularly to a preparation method of a porous TiC coating, which solves the deficiencies existing in the prior art, such as poor bonding strength of the coatings prepared by the sintering method and the thermal spraying method, difficulty in coating small inner cavity structures, complex processes, and limited thickness and porosity of the oxide coatings formed by the micro-arc oxidation method. In the preparation method of the porous TiC coating of the present invention, the metal matrix and the pore-forming agent undergo an in-situ reaction in an Ar atmosphere or a mixed atmosphere of Ar and O<subgt;2< / subgt; to obtain a porous coating covering the surface of the metal matrix; wherein, the metal matrix includes Ti, and the pore-forming agent includes silicon carbide, and the resulting coating has good bonding strength with the matrix, and at the same time, coating preparation can be realized on the inner cavity surface of the matrix.

Description

Technical Field

[0001] The present invention relates to ceramic coating technology, and particularly to a preparation method of a porous TiC coating. Background Art

[0002] Porous titanium carbide (TiC) ceramic materials simultaneously possess the characteristics of TiC ceramics and porous materials. They not only have excellent physical and chemical properties of TiC ceramics, such as high melting point, high strength, high hardness, good thermal conductivity, good electrical conductivity, good biocompatibility, and excellent physical and chemical stability, but also have a series of characteristics of porous materials, such as ultra-low density, high specific surface area, high specific strength, and excellent fluid permeability. These excellent characteristics make porous TiC ceramics have broad application prospects as surface coating materials in fields such as electrode materials, filtration devices, catalyst carriers, heat exchange materials, and biomedical applications.

[0003] However, existing research mainly focuses on porous ceramic materials (such as the technologies disclosed in patents with publication numbers CN108440014B and CN106830980A) and porous metal coating materials (such as the published literature: Cui Fulong, Hong Fangjun, Lin Tao, et al., Sintered Porous Surface Distributed Array Jet Boiling [J]. Chinese Science Bulletin, 2020, 65(17): 1760–1769.), while there is little research on the preparation method of porous TiC coatings. The main preparation methods of porous ceramic coatings include sintering method, thermal spraying method, micro-arc oxidation method, etc. However, these methods have many problems. The coatings prepared by the sintering method and thermal spraying method have poor bonding strength, and it is difficult to coat small inner cavity structures, and the process is complex; the micro-arc oxidation method can only form oxide coatings, and the coating thickness and porosity are limited. Summary of the Invention

[0004] The object of the present invention is to solve the deficiencies in the prior art that the coatings prepared by the sintering method and thermal spraying method have poor bonding strength, it is difficult to coat small inner cavity structures, the process is complex, and the thickness and porosity of the oxide coatings formed by the micro-arc oxidation method are limited, and to provide a preparation method of a porous TiC coating.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] A preparation method of a porous TiC coating, characterized in that it includes the following steps:

[0007] S1.1. Add the powders of the metal substrate and the pore-forming agent into a reaction container, and the pore-forming agent powder completely covers the metal substrate;

[0008] S1.2. Place the reaction vessel in a heating furnace for in-situ reaction; the in-situ reaction is carried out in an Ar atmosphere or a mixed atmosphere of Ar and O2, the reaction temperature is 900 - 1400 °C, the heating rate is 5 - 10 °C / min, and the reaction time is 0.5 - 20 h; the metal substrate is pure titanium or a titanium alloy; the pore former includes silicon carbide;

[0009] S2. After the in-situ reaction in step S1 ends, keep the Ar atmosphere or the state of the mixed atmosphere of Ar and O2 in the heating furnace and cool it to room temperature, and finally obtain a porous TiC coating covering the surface of the metal substrate.

[0010] Further, in step S1.2, the volume fraction of O2 in the mixed atmosphere is less than or equal to 5%.

[0011] Further, in step S1.2, the reaction temperature is 1000 - 1300 °C.

[0012] Further, in step S1.2, the reaction time is 1 - 5 h.

[0013] Further, in step S1.1, the metal substrate is pretreated, and the pretreatment sequentially includes polishing, ultrasonic cleaning, and drying.

[0014] Further, in step S1.1, the pore former is composed of silicon carbide and silicon dioxide, wherein the mass percentage of silicon carbide is 95% - 99%, and the mass percentage of silicon dioxide is 1% - 5%.

[0015] Further, the purities of silicon carbide and silicon dioxide in the pore former are both 99.9%, the particle size of the silicon carbide powder is 0.05 - 50 microns, and the particle size of the silicon dioxide powder is 0.03 - 0.5 microns.

[0016] Further, in step S1.1, the mass percentage of silicon carbide in the pore former is 95%, the particle size is 2 microns, the mass percentage of silicon dioxide is 5%, and the particle size is 0.1 micron;

[0017] In step S1.2, the in-situ reaction is carried out in an Ar atmosphere, the reaction temperature is 1200 °C, the heating rate is 5 °C / min, and the reaction time is 5 h.

[0018] Further, the titanium alloy is TC4 or TA15.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The preparation method of a porous TiC coating in the present invention forms the coating through in-situ reaction, and the generated coating has good bonding force with the substrate. By using in-situ reaction, the coating can be prepared not only on the outer surface of the substrate, but also on the inner cavity surface of the substrate.

[0021] 2. The pores of the porous coating prepared in the present invention are uniform, and the synchronism, consistency, and controllability of the pore positions during the application process are good, which play a very important role in experimental and engineering applications.

[0022] 3. The physical and chemical properties of the TiC coating in the present invention are stable and remain stable under environments such as high temperature and strong corrosion, and it can be widely applied in sewage filtration devices, heat exchange materials, biomedical applications, etc.

[0023] 4. The porous TiC coating is prepared by the embedding method in the present invention, and the method is simple and reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 FIG. is a scanning electron microscope image of a porous coating prepared by the prior art; among them, a is the scanning electron microscope image of the porous surface prepared by Cui Fulong et al. (Chinese Science Bulletin, 2020, 65(17): 1160), and b is the scanning electron microscope image of the porous surface prepared by Huang Chuanhui et al. (Rare Metal Materials and Engineering, 2012, 41(7): 1161);

[0025] Figure 2 FIG. is a schematic structural diagram of the TiC coating obtained in Example 1 of the present invention; among them, a is the TC4 substrate, and b is the porous TiC coating;

[0026] Figure 3 FIG. is a scanning electron microscope image of the surface and cross-section of the TiC coating obtained in Example 1 of the present invention; among them, a is the schematic structural diagram of the surface of the TiC coating, and b is the cross-sectional view of the TiC coating and the TC4 substrate;

[0027] Figure 4 FIG. is the XRD spectrum of the TiC coating in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The following further describes the content of the present invention in detail with reference to the drawings and specific embodiments:

[0029] Example 1

[0030] The preparation method of the porous TiC coating of the present invention is based on the reaction of a pore-forming agent and an atmosphere with a metal matrix to form a low-boiling-point substance. Through the volatilization of the low-boiling-point substance, a porous titanium structure is formed on the surface of the metal matrix. The porous titanium structure reacts with SiC and the like to form a porous titanium carbide structure at the same time. Titanium or a titanium alloy reacts with a pore-forming agent and an atmosphere to form a TiC coating on the surface of the metal matrix. The main reactions involved include Ti + SiC + SiO2 = TiC + 2SiO(g), 2Ti + 2SiC + O2(g) = 2TiC + SiO(g); at the same time, the following reactions are included: Ti + SiO2 = TiO(g) + SiO(g), Ti + SiC + 1.5O2(g) = TiO(g) + SiO(g) + CO(g). When the generated TiO(g) and SiO(g) volatilize, initial pores are formed on the surface of the metal matrix and the TiC coating; the titanium at the pores further reacts with SiO, resulting in an increase in pore diameter and pore depth. In addition to the above reactions, SiO also comes from the reactions SiC + 2SiO2 = 3SiO(g) + CO(g), SiC + O2(g) = SiO(g) + CO(g).

[0031] In the present invention, a porous titanium carbide structure is formed by in-situ reaction. The probability of initial chemical reactions in each tiny area on the surface of the sample is quite the same. Therefore, the prepared pore distribution is uniform and the voids are relatively large; while the sintering method and the thermal spraying method are prepared by adhering target powders on the matrix surface, but agglomeration phenomena inevitably occur in the powders, as Figure 1 shown in a below. The uniformity of the prepared porous structure is poor, and due to the fact that the coating is obtained by adhesion, the coating bonding force is poor, and it is difficult to coat small inner cavity structures; the micro-arc oxidation method and anodic oxidation are based on the pores left by the conductive effect during the oxidation of the matrix, as Figure 1 shown in b below. Most of the pores are small holes with a size of less than 2 microns, the porosity is low, and due to the limitation of the preparation method, the coating thickness is limited.

[0032] In this embodiment, the preparation method of the porous TiC coating includes the following steps:

[0033] S1. Pretreat the titanium alloy (TC4) matrix: After polishing the TC4 matrix, ultrasonically clean it in a cleaning agent and then dry it;

[0034] S2. Add both the pretreated TC4 matrix and the pore-forming agent powder into a reaction vessel, and the pore-forming agent powder completely covers the TC4 matrix; the mass percentage of silicon carbide in the pore-forming agent powder is 95%, the particle size is 2 microns, the mass percentage of silicon dioxide is 5%, and the particle size is 0.1 micron; the reaction vessel is a graphite crucible; the purities of both silicon carbide and silicon dioxide are 99.9%;

[0035] S3. Place the graphite crucible in S2 into a heating furnace and carry out the reaction under an Ar atmosphere. The reaction temperature is 1200 °C, the heating rate is 5 °C / min, and the reaction time is 5 h. That is, after the temperature rises to 1200 °C, keep it at this temperature for 5 h.

[0036] S4. After the reaction is completed, let the temperature of the Ar atmosphere in the heating furnace drop to room temperature, take out the TC4 substrate, and remove the silicon carbide and silicon dioxide powders adhering to its surface to obtain a TC4 substrate covered with a porous TiC coating. The thickness of the porous TiC coating is 150 microns.

[0037] In this embodiment, the structure of the prepared TiC coating is as Figure 2 shown, where a is the TC4 substrate and b is the porous TiC coating; Figure 3 are the scanning electron microscope images of the surface and cross-section of the porous TiC coating obtained in this embodiment. As can be seen from a in Figure 3 , the surface of the TiC coating is distributed with a uniform pore structure, Figure 3 and as can be seen from b in Figure 4 , the thickness of the porous coating is 150 microns;

[0038] Example Two

[0039] A method for preparing a porous TiC coating of the present invention includes the following steps:

[0040] S1. Pretreat the pure titanium (TA2) substrate: After polishing the TA2 substrate, ultrasonically clean it in a cleaning agent and then dry it;

[0041] S2. Add the pretreated TA2 substrate and the pore-forming agent powder into a graphite crucible, and the pore-forming agent powder completely covers the TA2 substrate; the mass percentage of silicon carbide in the pore-forming agent powder is 99%, the particle size is 0.05 microns, and the mass percentage of silicon dioxide is 1%, and the particle size is 0.5 microns;

[0042] S3. Place the graphite crucible in S2 into a heating furnace and carry out the reaction under an Ar atmosphere. The reaction temperature is 900 °C, the heating rate is 5 °C / min, and the reaction time is 0.5 h;

[0043] S4. After the reaction is completed, let the temperature of the Ar atmosphere in the heating furnace drop to room temperature, take out the TA2 substrate, and remove the silicon carbide powder adhering to its surface to obtain a TA2 substrate covered with a porous TiC coating. The thickness of the porous TiC coating is 1 micron.

[0044] Example Three

[0045] A method for preparing a porous TiC coating of the present invention includes the following steps:

[0046] S1. Pretreat the titanium alloy (TA15) substrate: After polishing the TA15 substrate, ultrasonically clean it in a cleaning agent and then dry it.

[0047] S2. Add both the pretreated TA15 substrate and the pore-forming agent powder into a graphite crucible, and the pore-forming agent powder completely covers the TA15 substrate; the mass percentage of silicon carbide in the pore-forming agent powder is 97%, the particle size is 50 microns, the mass percentage of silicon dioxide is 3%, and the particle size is 0.03 microns.

[0048] S3. Place the graphite crucible in S2 in a heating furnace and react in a mixed atmosphere of Ar and O2. The reaction temperature is 1000 °C, the heating rate is 10 °C / min, and the reaction time is 1 h; the volume fraction of O2 is 0.1%.

[0049] S4. After the reaction is completed, cool the temperature of the mixed atmosphere in the heating furnace to room temperature, take out the TA15 substrate, remove the silicon carbide powder attached to its surface, and obtain the TA15 substrate covered with a porous TiC coating. The thickness of the porous TiC coating is 50 microns.

[0050] Example Four

[0051] A method for preparing a porous TiC coating of the present invention includes the following steps:

[0052] S1. Pretreat the titanium alloy (TA15) substrate: After polishing the TA15 substrate, ultrasonically clean it in a cleaning agent and then dry it.

[0053] S2. Add both the pretreated TA15 substrate and the pore-forming agent powder into a graphite crucible, and the pore-forming agent powder completely covers the TA15 substrate; the mass percentage of silicon carbide in the pore-forming agent powder is 98%, the particle size is 1 micron, the mass percentage of silicon dioxide is 2%, and the particle size is 0.2 microns.

[0054] S3. Place the graphite crucible in S2 in a heating furnace and react in an atmosphere of Ar and O2. The reaction temperature is 1400 °C, the heating rate is 7 °C / min, and the reaction time is 10 h; the volume fraction of O2 is 5%.

[0055] S4. After the reaction is completed, cool the temperature of the mixed atmosphere in the heating furnace to room temperature, take out the TA15 substrate, remove the silicon carbide powder attached to its surface, and obtain the TA15 substrate covered with a porous TiC coating. The thickness of the porous TiC coating is 350 microns.

[0056] Example Five

[0057] A method for preparing a porous TiC coating of the present invention includes the following steps:

[0058] S1. Pretreat the titanium alloy (TC4) substrate: After polishing the TC4 substrate, ultrasonically clean it in a cleaning agent and then dry it;

[0059] S2. Add the pretreated TC4 substrate and the pore-forming agent powder into a graphite crucible, and the pore-forming agent powder completely covers the TC4 substrate; the mass percentage of silicon carbide in the pore-forming agent powder is 96%, the particle size is 5 microns, the mass percentage of silicon dioxide is 4%, and the particle size is 0.03 microns;

[0060] S3. Place the graphite crucible in S2 in a heating furnace and react under an Ar atmosphere. The reaction temperature is 1300 °C, the heating rate is 5 °C / min, and the reaction time is 20 h;

[0061] S4. After the reaction is completed, the temperature of the Ar atmosphere in the heating furnace is cooled to room temperature, take out the TC4 substrate, remove the silicon carbide powder attached to its surface, and obtain a TC4 substrate covered with a porous TiC coating. The thickness of the porous TiC coating is 300 microns.

[0062] The present invention is applicable to pure titanium and different titanium alloys, and porous coatings with different parameters such as different thicknesses can be obtained by adjusting parameters. The pore-forming agent includes silicon carbide, or it can be a mixture of silicon carbide and silicon dioxide, or a mixture of silicon carbide and other oxides.

Claims

1. A preparation method of a porous TiC coating, characterized in that, The following steps are involved: S1. In-situ reaction between metal matrix and pore-forming agent S1.

1. The metal substrate and the pore-forming agent powder are added to the reaction vessel, and the pore-forming agent powder completely covers the metal substrate; the pore-forming agent is composed of silicon carbide and silicon dioxide; S1.

2. The reaction vessel is placed in a heating furnace for an in-situ reaction; the in-situ reaction is carried out in an Ar atmosphere or a mixed atmosphere of Ar and O2, the reaction temperature is 900 to 1400 ° C, the heating rate is 5 to 10 ° C / min, and the reaction time is 0.5 to 20h; the metal substrate is pure titanium or a titanium alloy; S2. After the in-situ reaction of step S1 is completed, the Ar atmosphere or the mixed atmosphere of Ar and O2 is maintained in the heating furnace and cooled to room temperature, thereby finally obtaining a porous TiC coating covering the surface of the metal substrate.

2. The method for preparing a porous TiC coating according to claim 1, wherein: In step S1.2, the volume fraction of O2 in the mixed atmosphere is less than or equal to 5%.

3. The method for preparing a porous TiC coating according to claim 2, wherein: In step S1.2, the reaction temperature is 1000-1300°C.

4. The method for preparing a porous TiC coating according to claim 3, wherein: In step S1.2, the reaction time is 1 to 5 hours.

5. The method for preparing a porous TiC coating according to claim 4, characterized in that: In step S1.1, the metal substrate is pretreated, and the pretreatment includes polishing, ultrasonic cleaning and drying in sequence.

6. The method for preparing a porous TiC coating according to any one of claims 1 to 5, characterized in that: In step S1.1, in the pore-forming agent, the mass percentage of silicon carbide is 95% to 99%, and the mass percentage of silicon dioxide is 1% to 5%.

7. The method for preparing a porous TiC coating according to claim 6, wherein: The purity of silicon carbide and silicon dioxide in the pore-forming agent is both 99.9%, the particle size of silicon carbide powder is 0.05-50 microns, and the particle size of silicon dioxide powder is 0.03-0.5 microns.

8. The method for preparing a porous TiC coating according to claim 7, wherein: In S1.1, the mass percentage of silicon carbide in the pore-forming agent is 95% and the particle size is 2 μm, and the mass percentage of silicon dioxide is 5% and the particle size is 0.1 μm; In S1.2, the in-situ reaction is carried out in an Ar atmosphere, the reaction temperature is 1200° C., the heating rate is 5° C. / min, and the reaction time is 5 h.

9. The method for preparing a porous TiC coating according to claim 8, characterized in that: The titanium alloy is TC4 or TA15.

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