Boron carbide ceramic-metal gradient connection structure and preparation method thereof

Abstract

The invention relates to the technical field of boron carbide ceramics, in particular to a boron carbide ceramic-metal gradient connection structure and a preparation method thereof.The boron carbide ceramic-metal gradient connection structure comprises a metal end, a ceramic end and a transition layer, and the transition layer is located between the metal end and the ceramic end; the transition layer comprises a metal phase and a ceramic phase, the metal phase and the ceramic phase are respectively a main component of a metal end material and a main component of a ceramic end material, and the mass proportion of the metal phase in the transition layer is gradually reduced from the metal end to the ceramic end; the mass proportion of the ceramic end in the transition layer is gradually reduced from the ceramic end to the metal end; the transition layer further comprises titanium, and the mass proportion of the titanium in the transition layer is increased and then reduced from the metal end to the ceramic end. Titanium reacting with boron carbide is used as a part of the transition layer, and the wettability of the transition layer and boron carbide and the interface bonding strength are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of boron carbide ceramics, and in particular to a boron carbide ceramic-metal gradient connection structure and a preparation method thereof. Background Art

[0002] Functionally graded cermets (FGMs) exhibit continuous microstructure variations along one or several specific directions, resulting in gradual changes in their mechanical and thermodynamic properties along these specific directions. First proposed in 1986 by scientists in Sendai, Japan, this high-performance material features continuous or step-wise changes in composition, structure, and physical properties. Because the cermet's microstructure continuously varies along one or several specific directions, its mechanical and thermodynamic properties gradually change along these specific directions.

[0003] Functionally graded metal ceramics have both the heat resistance and wear resistance of ceramics and the mechanical toughness of metals. The component distribution can be optimized according to specific conditions and selected according to the parts, structure and specific conditions of use. At the same time, the continuous change of components and structure can eliminate the macroscopic thermal stress interface between ceramics and metals, alleviate the internal thermal stress of the material, and also have some special uses.

[0004] Existing functionally gradient metal ceramics mainly adopt electric field activation, powder layered pressing or pressure-assisted sintering processes. They are composed of multi-layer composite structures of ceramic and metal materials with gradient chemical composition and physical properties. Because the powder itself cannot achieve a smooth transition of elements, there are usually problems such as poor element gradient control and low interface bonding strength. To solve this problem, the commonly adopted approach is to rely on high-melting-point brazing alloys and multi-layer gradient brazing processes, which leads to high cost and low efficiency.

[0005] Therefore, developing a boron carbide ceramic-metal gradient connection structure and its preparation method, improving the element gradient stability control to achieve better interface bonding strength, and efficiently producing low-cost functional gradient metal ceramics are technical problems that need to be solved by technicians in this field. Summary of the Invention

[0006] To solve the above technical problems, the present invention provides a boron carbide ceramic-metal gradient connection structure and a preparation method thereof. One of the purposes of the present invention is to make the element gradient of the powder material transition smoothly and ensure the interface bonding strength. Another purpose of the present invention is to reduce the weighing process in the preparation process and reduce the error.

[0007] The technical solution adopted in this application to solve this technical problem is:

[0008] A boron carbide ceramic-metal gradient connection structure, comprising:

[0009] Metal end, composed of metal alloy;

[0010] Ceramic end, composed of boron carbide sintered body;

[0011] a transition layer located between the metal end and the ceramic end, the transition layer comprising a metal phase and a ceramic phase, the metal phase and the ceramic phase being the main components of the metal end material and the ceramic end material, respectively, and the mass proportion of the metal phase in the transition layer gradually decreases from the metal end to the ceramic end, and the mass proportion of the ceramic end in the transition layer gradually decreases from the ceramic end to the metal end;

[0012] The transition layer also includes titanium, and the mass proportion of the titanium in the transition layer first increases and then decreases from the metal end to the ceramic end.

[0013] The present invention utilizes titanium that reacts with boron carbide as a part of the transition layer. The transition layer has excellent wettability and interface bonding strength with the boron carbide.

[0014] Furthermore, the main component of the alloy of the metal end is Al or Fe, among which aluminum alloy is the main application direction of the present invention.

[0015] Furthermore, the mass proportion of the metal phase in the transition layer decreases from 80% to 98% to 0% from the metal end to the ceramic end, and the mass proportion of the ceramic phase increases from 0% to 40% to 50% from the metal end to the ceramic end.

[0016] Furthermore, the transition layer also contains at least one of copper, silicon, nickel, zinc, silver, and tin elements to increase wettability and reduce the formation of intermetallic compounds.

[0017] A method for preparing a boron carbide ceramic-metal gradient connection structure comprises the following steps:

[0018] Step S1: cleaning the surfaces of the boron carbide sintered body and the metal alloy to obtain a ceramic end and a metal end;

[0019] Step S2: preparing a mixed powder of titanium metal powder and boron carbide metal powder, wherein the mixed powder also contains 2% to 5% copper powder, evenly spreading the mixed powder on the surface of the ceramic end, placing the mixed powder in a sintering device and sintering it under pressure at 1000-1100°C to obtain a ceramic end having a titanium-boron carbide bonding layer;

[0020] Step S3: Prepare solder, which is

[0021] Filling the titanium-boron carbide bonding layer obtained in step S2 with brazing filler metal on the surface of the metal end obtained in step S1, and brazing to form a brazing layer, wherein the titanium-boron carbide bonding layer and the brazing layer together constitute a transition layer, and the metal end, the transition layer and the ceramic end together constitute a boron carbide ceramic-metal gradient connection structure;

[0022] The present invention utilizes the reaction of transition metals with boron carbide, hot pressing, infiltration and sintering to form a metal gradient connection between titanium and boron carbide, and then uses brazing to achieve a gradient connection between titanium and the alloy. Only two steps are required to complete the preparation of the ceramic-metal gradient connection structure, with fewer steps, lower energy consumption costs and process costs, and is suitable for industrial applications.

[0023] Furthermore, in step S2, the mixed powder is vibrated at 50-100 Hz before sintering, with the vibration direction parallel to the plane where the transition layer is located, and the vibration duration is 5-15 seconds.

[0024] Vibration can separate different particles in the solder and different particles in the mixed powder to form a gradient state, which is more conducive to the formation of mechanical properties of the material and reduces defects in the processing process. Even if a gradient is generated among the components in the powder at 50-100Hz for 5-15s, the powder will not be completely stratified. During the sintering or welding process, the molten components are squeezed and penetrated into other components to form a dense structure.

[0025] This method can eliminate the process of weighing powder multiple times, so that the paving can be completed by weighing the powder with a good ratio once, and the powder can be laid more evenly.

[0026] Furthermore, in step S2, the average particle size ratio of the titanium metal powder to the boron carbide metal powder constituting the mixed powder is 2-10:1.

[0027] Preferably, the average particle size ratio of the titanium metal powder to the boron carbide metal powder constituting the mixed powder in step S2 is 3-5:1.

[0028] Furthermore, the solder includes metal phase powder and wettability powder, and the average particle size ratio of the metal phase powder to the wettability powder is 2-10:1.

[0029] Preferably, the average particle size ratio of the metal phase powder to the wettability powder is 3-5:1.

[0030] An excessively large particle size ratio will make it difficult to mix the mixed powder and the solder powder evenly, resulting in large differences in the quality of different batches of products. The scope of the present invention can ensure that the mixed powder and the solder powder are in a uniformly mixed state, is suitable for industrial use, and reduces process costs.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention utilizes titanium that reacts with boron carbide as part of the transition layer. The transition layer has excellent wettability and interface bonding strength with boron carbide.

[0033] 2. The present invention utilizes the reaction between transition metals and boron carbide, hot pressing, infiltration and sintering to form a metal gradient connection between titanium and boron carbide, and then uses brazing to achieve a gradient connection between titanium and the alloy. Only two steps are required to complete the preparation of the ceramic-metal gradient connection structure, with fewer steps, low cost, and suitable for industrial applications.

[0034] 3. In the preparation method of the present invention, vibration is used to separate the different particles in the solder and the different particles in the mixed powder to form a gradient state, which is more conducive to the formation of the mechanical properties of the material and reduces defects in the processing process. It not only ensures the standard proportion of the uniform weighing of the mixed powder, but also ensures the uniform transition of the gradient connection in the transition layer. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to specific embodiments.

[0036] The present invention is committed to realizing a boron carbide ceramic-metal gradient connection structure through a two-step method, achieving low-cost industrial production with fewer steps and a simple production process, so that the boron carbide ceramic-metal gradient connection structure has a stable element gradient change and strong interface bonding strength.

[0037] The present invention uses titanium as an intermediate transition to ensure interface bonding strength, and introduces a unified weighing and vibration distribution method to reduce the number of steps and weighing times, thereby ensuring a smooth transition of the element gradient of the powder. Therefore, the boron carbide ceramic-metal gradient connection structure prepared by the present invention has its own special composition, mainly including:

[0038] Metal end, composed of metal alloy;

[0039] Ceramic end, composed of boron carbide sintered body;

[0040] a transition layer located between the metal end and the ceramic end, the transition layer comprising a metal phase and a ceramic phase, the metal phase and the ceramic phase being the main components of the metal end material and the ceramic end material, respectively, and the mass proportion of the metal phase in the transition layer gradually decreases from the metal end to the ceramic end, and the mass proportion of the ceramic end in the transition layer gradually decreases from the ceramic end to the metal end;

[0041] The transition layer also includes titanium, and the mass proportion of the titanium in the transition layer first increases and then decreases from the metal end to the ceramic end.

[0042] The following is a detailed description taking the preparation of gradient metal ceramics of boron carbide and aluminum alloy as an example.

[0043] Example 1

[0044] A method for preparing a boron carbide ceramic-metal gradient connection structure comprises the following steps:

[0045] Step S1: cleaning the surfaces of the boron carbide sintered body and the aluminum alloy, removing the oxide layer by sandblasting, and ultrasonically cleaning with acetone for 20 minutes to obtain a ceramic end and a metal end, wherein the surfaces of the ceramic end and the metal end are both flat;

[0046] Step S2: titanium metal powder (average particle size of 50 microns) and boron carbide metal powder (average particle size of 20 microns) are prepared to form a mixed powder with a weight ratio of 3:1, and the mixed powder is evenly spread on the surface of the ceramic end. The mixed powder is then vibrated at a frequency of 60 Hz for 15 seconds, placed in a sintering device and evacuated, and then pressure-assisted sintering is performed at a holding temperature of 1000-1100°C, a holding time of 30 minutes, and a pressure of 20 MPa to obtain a ceramic end with a titanium-boron carbide bonding layer.

[0047] Step S3: Prepare a brazing filler metal, which uses Al-10Si-1Mg, and can additionally add nickel or tin to increase wettability and reduce the formation and growth of titanium-aluminum intermetallic compounds. The brazing filler metal is filled into the titanium-boron carbide bonding layer obtained in step S2 and the surface of the metal end obtained in step S1, and vacuum pressure-assisted brazing is performed by heating at 590-595°C for 5-10 minutes and a pressurization pressure of 0.5-2MPa. After the insulation is completed, the oil is immersed and quickly cooled, and the brazing filler metal forms a brazing layer; the titanium-boron carbide bonding layer and the brazing layer together constitute a transition layer, and the metal end, the transition layer and the ceramic end together constitute a boron carbide ceramic-metal gradient connection structure.

[0048] Example 2

[0049] A method for preparing a boron carbide ceramic-metal gradient connection structure comprises the following steps:

[0050] Step S1: cleaning the surfaces of the boron carbide sintered body and 304 stainless steel, removing the oxide layer by sandblasting, and ultrasonically cleaning with acetone for 20 minutes to obtain a ceramic end and a metal end, wherein the surfaces of the ceramic end and the metal end are both flat;

[0051] Step S2: titanium metal powder (average particle size of 45 μm) and boron carbide powder (average particle size of 10 μm) were mixed in a mass ratio of 4:1, and 3% nickel was added as a wetting agent. After mixing, the mixture was evenly spread on the surface of the ceramic end. The powdered ceramic end was vibrated at a frequency of 80 Hz for 12 seconds, and then pressure-assisted sintering was performed in a vacuum sintering furnace under argon protection. The temperature was raised to 1050°C and maintained for 40 minutes, and an axial pressure of 25 MPa was applied.

[0052] Step S3: Prepare Ag-28Cu-2Ti solder (particle size distribution 15-45 μm), evenly lay it between the titanium-boron carbide composite layer and the stainless steel surface, heat it to 850°C in a vacuum brazing furnace, keep it warm for 8 minutes, apply a pressure of 1.5 MPa, and after the insulation is completed, immerse it in oil and quickly cool it to form a brazing layer. The titanium-boron carbide bonding layer and the brazing layer together constitute a transition layer, and the metal end, the transition layer and the ceramic end together constitute a boron carbide ceramic-metal gradient connection structure.

[0053] Comparative Example

[0054] The preparation method of this comparative example is completely consistent with that of Example 1 except that the vibration treatment is omitted in step S2.

[0055] The boron carbide ceramic-metal gradient connection structures prepared in the above three embodiments were tested, and the test results are as follows:

[0056]

[0057] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

Claims

1. A boron carbide ceramic-metal gradient connection structure, characterized in that: include: Metal end, composed of metal alloy; Ceramic end, composed of boron carbide sintered body; a transition layer located between the metal end and the ceramic end, the transition layer comprising a metal phase and a ceramic phase, the metal phase and the ceramic phase being the main components of the metal end material and the ceramic end material, respectively, and the mass proportion of the metal phase in the transition layer gradually decreases from the metal end to the ceramic end, and the mass proportion of the ceramic end in the transition layer gradually decreases from the ceramic end to the metal end; The transition layer also includes titanium, and the mass proportion of titanium in the transition layer first increases and then decreases from the metal end to the ceramic end.

2. The boron carbide ceramic-metal gradient connection structure according to claim 1, characterized in that: The main component of the alloy of the metal end is Al or Fe.

3. The boron carbide ceramic-metal gradient connection structure according to claim 1, characterized in that: The mass proportion of the metal phase in the transition layer decreases from 80% to 98% to 0% from the metal end to the ceramic end, and the mass proportion of the ceramic phase increases from 0% to 40% to 50% from the metal end to the ceramic end.

4. The boron carbide ceramic-metal gradient connection structure according to claim 1, characterized in that: The transition layer also contains at least one of copper, silicon, nickel, zinc, silver and tin.

5. A method for preparing a boron carbide ceramic-metal gradient connection structure, characterized in that: The following steps are involved: Step S1: cleaning the surfaces of the boron carbide sintered body and the metal alloy to obtain a ceramic end and a metal end; Step S2: preparing titanium metal powder and boron carbide metal powder to make a mixed powder, evenly spreading it on the surface of the ceramic end, placing it in a sintering device and sintering it under pressure at 1000-1100° C. to obtain a ceramic end with a titanium-boron carbide bonding layer; Step S3: Prepare a brazing material and fill the titanium-boron carbide bonding layer obtained in step S2 with the brazing material on the surface of the metal end obtained in step S1, and braze to form a brazing layer. The titanium-boron carbide bonding layer and the brazing layer together constitute a transition layer, and the metal end, the transition layer and the ceramic end together constitute a boron carbide ceramic-metal gradient connection structure.

6. The method for preparing a boron carbide ceramic-metal gradient connection structure according to claim 5, characterized in that: In step S2, the mixed powder is vibrated at 50-100 Hz before sintering, with the vibration direction parallel to the plane where the transition layer is located, and the vibration duration is 5-15 seconds.

7. The method for preparing a boron carbide ceramic-metal gradient connection structure according to claim 6, characterized in that: The average particle size ratio of the titanium metal powder to the boron carbide metal powder constituting the mixed powder in step S2 is 2-10:

1.

8. The method for preparing a boron carbide ceramic-metal gradient connection structure according to claim 7, characterized in that: The average particle size ratio of the titanium metal powder to the boron carbide metal powder constituting the mixed powder in step S2 is 3-5:

1.

9. The method for preparing a boron carbide ceramic-metal gradient connection structure according to claim 6, characterized in that: The solder in step S3 includes metal phase powder and wettability powder, and the average particle size ratio of the metal phase powder to the wettability powder is 2-10:

1.

10. The method for preparing a boron carbide ceramic-metal gradient connection structure according to claim 9, characterized in that: The average particle size ratio of the metal phase powder to the wettability powder is 3-5:1.

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