Surface layer high-hardness gradient titanium-based composite material and preparation method thereof

Abstract

The surface layer high-hardness gradient titanium-based composite material comprises a surface layer, a middle layer and a base body layer which are sequentially arranged in the thickness direction of the surface layer, the surface layer and the middle layer are both prepared from mixed powder formed by adding reinforcing phase powder into TC4 titanium alloy powder, and the volume fraction of the reinforcing phase is gradually reduced from the outside to the inside; the preparation method of the composite material comprises the following steps: 1, carrying out ball milling treatment on TC4 titanium alloy powder and WC powder to respectively obtain mixed powder; and 2, the base body layer alloy powder and the mixed powder for preparing the middle layer and the surface layer are sequentially laid and then subjected to hot pressing sintering. According to the invention, the surface layer and the middle layer added with the reinforcing phase are arranged on the surface of the titanium-based matrix, and the volume fraction of the reinforcing phase is gradually reduced from outside to inside to form a high-hardness gradient layered structure, so that the strain localization of deformation is relieved, and the binding force of each layer is improved, so that the titanium-based composite material has high hardness and excellent strength and plasticity and toughness; the material is suitable for the fields of aerospace, biological implants and military wear-resistant parts.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite materials, and particularly relates to a titanium matrix composite material with a high surface hardness gradient and a preparation method thereof. Background Art

[0002] Titanium matrix composites have attracted much attention in the fields of aerospace, biomedicine, etc. due to their high strength, low density, and excellent corrosion resistance. However, the surface hardness of traditional titanium-based materials is insufficient, they are prone to wear, and their fatigue resistance is limited, which restricts their application in extreme working conditions (such as aeroengine blades, artificial joints). The existing technologies mainly improve the performance through surface coatings (such as ceramic coatings, titanium nitride coatings) or overall reinforcement (dispersion of silicon carbide particles, whiskers), but there are still the following bottlenecks: 1) Insufficient coating adhesion: Traditional physical / chemical coatings are prone to interface peeling due to the mismatch of thermal expansion coefficients, and the risk of failure is high after long-term service. 2) Process complexity: Technologies such as laser cladding and plasma spraying require multiple processes, with high costs and low efficiency. 3) Performance compromise: Although the overall reinforced materials improve the hardness, they sacrifice the toughness of the matrix, and microcracks are easily induced by residual stresses during the additive manufacturing process.

[0003] In recent years, the gradient structure design has become a technical breakthrough. By regulating the continuous gradient changes of composition, microstructure, and hardness from the surface layer to the interior, the synergistic performance of "hard outside and tough inside" can be achieved. However, existing patents on gradient titanium matrix composites (such as CN2022103456A, US2023045678B2) mostly focus on the gradient distribution of a single reinforcing phase (such as TiB, TiC), and there are problems such as segregation of the reinforcing phase and poor interfacial compatibility. Moreover, the preparation process relies on the combination of high-energy ball milling and hot isostatic pressing, with high energy consumption and difficulty in large-scale production. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a titanium matrix composite material with a high surface hardness gradient in view of the above-mentioned deficiencies of the prior art. By setting a surface layer and an intermediate layer with added reinforcing phases on the surface of the titanium matrix, and gradually reducing the volume fraction of the reinforcing phase from the surface to the interior to form a high-hardness gradient layered structure, the strain localization of deformation is alleviated, the bonding force of each layer is improved, so that the titanium matrix composite material has both high hardness and excellent strength, plasticity, and toughness, and solves the problems that the existing titanium matrix composites sacrifice toughness to improve hardness and have insufficient coating adhesion.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows: A surface high-hardness gradient titanium matrix composite material, characterized in that it includes a surface layer, an intermediate layer, and a matrix layer, and the surface layer, the intermediate layer, and the matrix layer are arranged in sequence from the surface to the inside along the thickness direction of the surface high-hardness gradient titanium matrix composite material. Among them, both the surface layer and the intermediate layer are made of a mixed powder obtained by adding reinforcing phase powder to titanium alloy powder, and the volume fraction of the reinforcing phase in the surface layer and the intermediate layer gradually decreases, and the matrix layer is made of titanium-based powder.

[0006] The above-mentioned surface high-hardness gradient titanium matrix composite material is characterized in that both the surface layer and the intermediate layer are made of TC4 titanium alloy powder and WC powder. Generally, the types of titanium alloy powder used in the surface layer and the intermediate layer are as similar as possible to the types or components of the titanium-based powder in the matrix layer to ensure the uniform transition of the composition and performance of the entire surface high-hardness gradient titanium matrix composite material.

[0007] The above-mentioned surface high-hardness gradient titanium matrix composite material is characterized in that the particle size of the TC4 titanium alloy powder is 80 μm to 120 μm, and the particle size of the WC powder is 1 μm to 5 μm.

[0008] The above-mentioned surface high-hardness gradient titanium matrix composite material is characterized in that the volume fraction of the WC reinforcing phase in the surface layer and the intermediate layer is 5% to 25%.

[0009] The above-mentioned surface high-hardness gradient titanium matrix composite material is characterized in that the intermediate layer includes a first sub-intermediate layer, a second sub-intermediate layer, a third sub-intermediate layer, and a fourth sub-intermediate layer adjacent to each other in sequence, and the first sub-intermediate layer is adjacent to the surface layer, and the thickness of the intermediate layer is the same as that of the surface layer. Among them, the volume fraction of the reinforcing phase in the surface layer is 20% to 25%, the volume fraction of the reinforcing phase in the first sub-intermediate layer is 15% to 20%, the volume fraction of the reinforcing phase in the second sub-intermediate layer is 10% to 15%, the volume fraction of the reinforcing phase in the third sub-intermediate layer is 5% to 10%, and the volume fraction of the reinforcing phase in the fourth sub-intermediate layer is 1% to 5%. The present invention realizes the gradient layered structure design of the gradient titanium matrix composite material by setting 4 sub-intermediate layers in the intermediate layer, making the gradient transition from the surface layer to the inside more refined, thereby more stably and uniformly alleviating the strain localization during the deformation process, and preparing a gradient titanium matrix composite material with high hardness on the surface, while having high strength and high toughness, overcoming the problem that traditional titanium matrix composites have uniform composition and density due to uniform compounding, and thus single performance.

[0010] Meanwhile, the present invention also discloses a method for preparing the above-mentioned surface high-hardness gradient titanium matrix composite material, characterized in that the method includes the following steps: Step 1: Perform ball milling on the titanium alloy powder and the reinforcing phase powder to obtain the mixed powder for preparing the surface layer and the intermediate layer respectively; Step 2: Sequentially lay the titanium-based powder for preparing the matrix layer, the mixed powder for preparing the intermediate layer obtained in Step 1, and the mixed powder for preparing the surface layer in a mold, and then perform hot pressing and sintering to obtain a surface layer high-hardness gradient titanium-based composite material including a surface layer, an intermediate layer, and a matrix layer.

[0011] In the above preparation method, the ball milling speed in Step 1 is 180 r / min to 220 r / min, the time is 5 h, and the ball-to-material ratio is 5:1. More preferably, the ball milling speed is 200 r / min.

[0012] In the above preparation method, the vacuum degree of the hot pressing and sintering in Step 2 is not higher than 1×10 - 3 Pa, the sintering temperature is 1050 °C, the pressure is 30 MPa, the heat preservation time is 1 h, and it is taken out for air cooling after the furnace is cooled to 100 °C.

[0013] The present invention has the following advantages compared with the prior art: 1. By setting a surface layer and an intermediate layer made of adding reinforcing phase powder to titanium alloy powder on the surface of the titanium-based matrix, and the volume fraction of the reinforcing phase gradually decreases from the surface to the inside, on the basis of ensuring the surface hardness by using the reinforcing phase, a high-hardness gradient layered structure is formed, effectively alleviating the strain localization during the deformation process, giving full play to its structural advantages, making the deformation more stable and uniform, improving the problem of the inversion of strength and plastic toughness of a single titanium-based composite material, and obtaining a titanium-based composite material with good comprehensive properties, especially high hardness, high strength, and high toughness.

[0014] 2. In the surface layer high-hardness gradient titanium-based composite material of the present invention, the titanium alloy powder in the surface layer and the intermediate layer still dominates, so the bonding force between the layers after sintering is still strong, and the gradient layered structure effectively connects the surface layer and the matrix layer, and there is no obvious interface transition layer between the layers, improving the bonding force between the layers. At the same time, its composition and structure can be optimized according to actual application requirements to change the local characteristics of the material, making it have multiple performance advantages and expanding the application range.

[0015] 3. The present invention first adopts a layered powder laying method to realize the gradient layered structure, and the gradient composition and layer thickness are controllable. Then, hot pressing and sintering are used to form a firm metallurgical bond between the interfaces of the layers, and the interfaces between the layers are flat and well-bonded, without an obvious interface transition layer, further improving the bonding stability between the layers and solving the problem of poor interfacial bonding force of the layered materials prepared by the existing methods.

[0016] 4. The preparation method of the present invention is simple, stable, and low in cost, and is suitable for preparing large-scale surface layer high-hardness gradient titanium-based composite materials.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0018] Figure 1 It is a physical diagram of the surface high-hardness gradient titanium matrix composite material prepared in Example 1 of the present invention.

[0019] Figure 2 It is a scanning electron microscope image of the surface high-hardness gradient titanium matrix composite material prepared in Example 1 of the present invention.

[0020] Figure 3 It is a hardness result diagram of the surface high-hardness gradient titanium matrix composite material prepared in Example 1 of the present invention. Detailed Embodiments

[0021] Example 1 The surface high-hardness gradient titanium matrix composite material of this example includes a surface layer, an intermediate layer and a matrix layer, and the surface layer, the intermediate layer and the matrix layer are arranged in sequence from the surface to the inside along the thickness direction of the surface high-hardness gradient titanium matrix composite material. Among them, both the surface layer and the intermediate layer are made of a mixed powder obtained by adding reinforcing phase WC powder to TC4 titanium alloy powder, and the volume fraction of WC powder in the surface layer and the intermediate layer gradually decreases. The particle size of the TC4 titanium alloy powder is 85μm, and the particle size of the WC powder is 2μm. The matrix layer is made of TC4 titanium alloy powder; The intermediate layer includes a first sub-intermediate layer, a second sub-intermediate layer, a third sub-intermediate layer, and a fourth sub-intermediate layer that are adjacent to each other in sequence. The first sub-intermediate layer is adjacent to the surface layer, and the thickness of the intermediate layer and the surface layer is the same, both being 1mm. Among them, the volume fraction of the WC reinforcing phase in the surface layer is 25%, the volume fraction of the WC reinforcing phase in the first sub-intermediate layer is 20%, the volume fraction of the WC reinforcing phase in the second sub-intermediate layer is 15%, the volume fraction of the WC reinforcing phase in the third sub-intermediate layer is 10%, and the volume fraction of the WC reinforcing phase in the fourth sub-intermediate layer is 5%.

[0022] The preparation method of the surface high-hardness gradient titanium matrix composite material of this example includes the following steps: Step 1: Ball-mill the TC4 titanium alloy powder and the reinforcing phase WC powder to obtain the mixed powders for preparing the surface layer and the intermediate layer respectively; the ball-milling speed of the ball-milling treatment is 200r / min, the time is 5h, and the ball-to-material ratio is 5:1; Step 2: Lay the TC4 alloy powder for preparing the matrix layer, the mixed powder for preparing the intermediate layer obtained in Step 1, and the mixed powder for preparing the surface layer in the mold in sequence, and then perform hot-press sintering to obtain a surface high-hardness gradient titanium matrix composite material including a surface layer, an intermediate layer and a matrix layer, as Figure 1 shown; the vacuum degree of the hot-press sintering is not higher than 1×10 -3Pa, the sintering temperature was 1050 °C, the pressure was 30 MPa, the heat preservation time was 1 h, and it was taken out for air cooling after the furnace was cooled to 100 °C.

[0023] Figure 2 This is the scanning electron microscope image of the surface layer high-hardness gradient titanium matrix composite prepared in this example. From Figure 2 it can be seen that the volume fraction of WC in the microstructure of the titanium matrix composite from the surface to the inside is different, forming a gradient structure of WC distribution. The volume fraction content of WC in the surface layer is 25%, and its high-hardness characteristic improves the wear resistance of the composite material.

[0024] Figure 3 This is the hardness result graph of the surface layer high-hardness gradient titanium matrix composite prepared in this example. From Figure 3 it can be seen that the hardness of the titanium matrix composite with WC gradient distribution gradually decreases from the surface to the inside, which is consistent with the gradient distribution law of WC.

[0025] Example 2 The difference between this example and Example 1 is that the particle size of TC4 titanium alloy powder is 100 μm, and the particle size of WC powder is 3 μm; the volume fraction of WC reinforcing phase in the surface layer is 23%, the volume fraction of WC reinforcing phase in the first sub-intermediate layer is 18%, the volume fraction of WC reinforcing phase in the second sub-intermediate layer is 13%, the volume fraction of WC reinforcing phase in the third sub-intermediate layer is 8%, and the volume fraction of WC reinforcing phase in the fourth sub-intermediate layer is 3%.

[0026] Example 3 The difference between this example and Example 1 is that the particle size of TC4 titanium alloy powder is 150 μm, and the particle size of WC powder is 5 μm; the volume fraction of WC reinforcing phase in the surface layer is 21%, the volume fraction of WC reinforcing phase in the first sub-intermediate layer is 16%, the volume fraction of WC reinforcing phase in the second sub-intermediate layer is 11%, the volume fraction of WC reinforcing phase in the third sub-intermediate layer is 6%, and the volume fraction of WC reinforcing phase in the fourth sub-intermediate layer is 1%.

[0027] Example 4 The difference between this example and Example 1 is that the volume fraction of WC reinforcing phase in the surface layer is 20%, the volume fraction of WC reinforcing phase in the first sub-intermediate layer is 15%, the volume fraction of WC reinforcing phase in the second sub-intermediate layer is 10%, the volume fraction of WC reinforcing phase in the third sub-intermediate layer is 5%, and the volume fraction of WC reinforcing phase in the fourth sub-intermediate layer is 1%.

[0028] Example 5 The difference between this example and Example 1 is that the particle size of TC4 titanium alloy powder is 120 μm.

[0029] The above is only a preferred embodiment of the present invention and does not impose any limitations on the present invention. Any simple modifications, changes, and equivalent variations made to the above embodiments based on the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A titanium-based composite material with a high surface hardness gradient, characterized in that, It includes a surface layer, an intermediate layer and a matrix layer, and the surface layer, the intermediate layer and the matrix layer are arranged in sequence from the surface to the inside along the thickness direction of the surface high-hardness gradient titanium matrix composite material. Among them, both the surface layer and the intermediate layer are made of a mixed powder obtained by adding reinforcing phase powder to titanium alloy powder, and the volume fraction of the reinforcing phase in the surface layer and the intermediate layer gradually decreases, and the matrix layer is made of titanium-based powder.

2. The surface high-hardness gradient titanium matrix composite material according to claim 1, wherein, Both the surface layer and the intermediate layer are made of TC4 titanium alloy powder and WC powder.

3. The surface high-hardness gradient titanium matrix composite material according to claim 2, characterized in that, The particle size of the TC4 titanium alloy powder is 80μm - 120μm, and the particle size of the WC powder is 1μm - 5μm.

4. A surface high-hardness gradient titanium-based composite material according to claim 2, characterized in that, The volume fraction of the WC reinforcing phase in the surface layer and the intermediate layer is 5% - 25%.

5. A surface high-hardness gradient titanium-based composite material according to claim 1, characterized in that, The intermediate layer includes a first sub-intermediate layer, a second sub-intermediate layer, a third sub-intermediate layer, and a fourth sub-intermediate layer that are adjacent to each other in sequence. The first sub-intermediate layer is adjacent to the surface layer, and the thickness of the intermediate layer is the same as that of the surface layer. Among them, the volume fraction of the reinforcing phase in the surface layer is 20% - 25%, the volume fraction of the reinforcing phase in the first sub-intermediate layer is 15% - 20%, the volume fraction of the reinforcing phase in the second sub-intermediate layer is 10% - 15%, the volume fraction of the reinforcing phase in the third sub-intermediate layer is 5% - 10%, and the volume fraction of the reinforcing phase in the fourth sub-intermediate layer is 1% - 5%.

6. A method for preparing the surface high hardness gradient titanium-based composite material according to any one of claims 1 to 5, characterized in that: This method includes the following steps: Step 1: Carry out ball milling treatment on the titanium alloy powder and the reinforcing phase powder to respectively obtain the mixed powders for preparing the surface layer and the intermediate layer; Step 2: Lay the titanium-based powder for preparing the matrix layer, the mixed powder for preparing the intermediate layer obtained in Step 1, and the mixed powder for preparing the surface layer in sequence in a mold, and then carry out hot pressing sintering to obtain a surface high-hardness gradient titanium matrix composite material including a surface layer, an intermediate layer and a matrix layer.

7. The preparation method according to claim 6, wherein The ball milling speed in Step 1 is 180r / min - 220r / min, the time is 5h, and the ball-to-material ratio is 5:

1.

8. The preparation method according to claim 6 or 7, characterized in that, In Step 2, the vacuum degree of hot pressing sintering is not higher than 1×10 -3 Pa, the sintering temperature is 1050 °C, the pressure is 30 MPa, the heat preservation time is 1 h, and it is taken out for air cooling after the furnace is cooled to 100 °C.

Images