Gradient hardness composite ceramic swinging hammer and preparation method thereof

Abstract

The invention belongs to the technical field of ceramic-metal composite materials, and particularly relates to a gradient hardness composite ceramic swinging hammer and a preparation method thereof.The preparation method comprises the following steps that S1, ceramic particles are pretreated; s2, fully mixing the three ceramic particles with a reaction type metal binder, a pore forming agent and an inorganic binder according to a specific ratio, filling a mold with taper holes in a layered manner according to a fine-medium-coarse sequence, carrying out compression molding, drying, and carrying out two-stage sintering to obtain a ceramic preform; s3, preheating a prefabricated body; s4, the smelted high-toughness alloy steel liquid is poured into a casting mold, and pressure-assisted casting infiltration is carried out; s5, after the casting is cooled, shakeout and cleaning are conducted, and heat treatment is conducted; and S6, necessary machining is carried out. A gradient composite layer with continuously decreasing hardness is formed on the end face of the hammer head of the prepared swinging hammer from outside to inside, interface stress concentration is effectively relieved, impact resistance and wear resistance are improved, and metallurgical bonding of ceramic and metal is achieved.

Description

Technical Field

[0001] This invention belongs to the field of ceramic-metal composite materials technology, specifically relating to a gradient hardness composite ceramic hammer and its preparation method. Background Technology

[0002] As a core and vulnerable component of hammer crushers, the swing hammer is widely used in material crushing operations in industries such as mining, metallurgy, building materials, and cement. During its high-speed rotation, it repeatedly impacts and grinds high-hardness materials such as ores and concrete in an extremely harsh working environment, placing extremely high demands on the wear resistance, toughness, and impact resistance of the materials. Traditional swing hammers are mostly made of single-metal materials such as high-manganese steel and high-chromium cast iron. Although they possess certain advantages in toughness or hardness, under long-term high-impact and high-wear conditions, they still suffer from problems such as short service life, frequent replacement, and high maintenance costs.

[0003] To improve the wear resistance of hammers, researchers have gradually incorporated ceramic materials into the structural design, forming a technical route for metal-ceramic composite hammers. Patent CN112846192A discloses a manufacturing method for a metal-ceramic composite hammer, which involves preparing a honeycomb-shaped ceramic-metal composite preform and bonding it to a metal matrix using casting and welding. This method improves the problem of ceramic particle detachment; however, the composite layer has uniform hardness, and under strong impact, the abrupt change in performance between the hard and brittle ceramic layer and the tough matrix easily becomes a crack initiation point. Patent CN116251941B uses microwave-cured preforms and extrusion casting infiltration processes to form a reactive interface, optimizing the interfacial bonding between the ceramic preform and high-chromium cast iron. However, this method is complex, and the preform hardness remains uniform, failing to solve the stress buffering problem. Patent CN118357441B uses ceramic particles of different sizes to form a composite preform, but its design aims to improve the bonding force between the inner and outer layers and does not consciously construct a continuous hardness gradient; a clear performance interface still exists between its wear-resistant layer and the matrix. Patent CN120551365B employs liquid-liquid composite casting technology, using unconventional basalt ceramics and W-Ni-Fe high-density alloys. This technology is relatively expensive, and its core lies in the liquid-liquid composite of the two melts. The process window is narrow, making it difficult to control, and the overall toughness may depend on the expensive alloy matrix.

[0004] Although the above technologies have improved the wear resistance and service life of the hammer to some extent, the following problems still exist: (1) Insufficient interfacial bonding strength: Due to the large difference in thermal expansion coefficients between ceramics and metals, microcracks are easily generated during casting and heat treatment, leading to the shedding of ceramic particles and affecting service life; (2) Simple structural design: Most composite hammers use a single hardness ceramic layer, which makes it difficult to achieve the optimal balance between impact and wear, and is prone to brittle fracture or excessive wear; (3) Complex process and cost control: The preparation process of some high-performance hammers is complex, such as vacuum sintering, high-pressure infiltration, multi-step casting, etc., which leads to high manufacturing costs and makes it difficult to achieve large-scale application; (4) Lack of material gradient design: Existing technologies mostly focus on material composites, but lack gradient hardness design from the surface to the high-toughness matrix, and cannot achieve the ideal performance matching of "hard outside and tough inside". Therefore, it is urgent to develop a new composite hammer structure and its preparation method, which can ensure high wear resistance, excellent impact resistance and interfacial bonding strength, and take into account process feasibility and economy. Summary of the Invention

[0005] This invention overcomes the shortcomings of existing technologies by proposing a gradient hardness composite ceramic hammer and its preparation method. By constructing a continuous gradient structure from an ultra-high hardness ceramic surface layer to an internal high-toughness metal matrix, it effectively alleviates interfacial stress concentration and improves impact resistance and wear resistance. Simultaneously, by employing optimized preform design and casting processes, it achieves a metallurgical bond between ceramic and metal, simplifying the manufacturing process and reducing production costs. This technology is not only applicable to high-impact, high-wear mining and metallurgical conditions but also provides a new technological path for the industrialization of ceramic-metal composite hammers, possessing significant engineering application value and market prospects.

[0006] This invention proposes a method for preparing a gradient hardness composite ceramic hammer, the method comprising the following steps: S1. Ceramic particle pretreatment: Prepare three types of ceramic particles with different particle sizes and hardness: coarse, medium and fine, and pretreat the ceramic particles respectively. Preferably, the coarse and medium particles in step S1 are either Al2O3 or zirconium corundum, with the coarse particles having a particle size of 8-16 mesh and the medium particles having a particle size of 20-40 mesh. The fine particles are either ZrO2-toughened Al2O3 (ZTA) or pure ZrO2, with the fine particles having a particle size of 100-200 mesh. Preferably, the pretreatment in step S1 involves first soaking and cleaning with a 5-10% oxalic acid solution to remove surface impurities, then rinsing with deionized water until neutral, and finally drying at 150-200℃ for 2-4 hours.

[0007] The pretreatment of ceramic particles aims to activate the surface of the ceramic particles and improve their reactivity with subsequent metal binders.

[0008] S2. Preparation of ceramic preforms with gradient pore structure: Three types of ceramic particles are thoroughly mixed with a specific ratio of reactive metal binder, pore-forming agent and inorganic binder, and then filled into a mold with conical holes in the order of fine, medium and coarse. After pressing and molding under a pressure of 20-50MPa, the preforms are dried and sintered in two stages to obtain a three-dimensional gradient ceramic preform with compositional and structural gradients. Preferably, in step S2, the specific proportions of the addition of the reactive metal binder, pore-forming agent, and inorganic binder in the fine particles are 5-10.wt%, 5-8.wt%, and 5-8.wt% of the mass of the fine particles, respectively; the addition of the reactive metal binder, pore-forming agent, and inorganic binder in the medium particles are 10-15.wt%, 7-10.wt%, and 6-9.wt% of the mass of the medium particles, respectively; and the addition of the reactive metal binder, pore-forming agent, and inorganic binder in the coarse particles are 15-25.wt%, 5-8.wt%, and 7-10.wt% of the mass of the coarse particles, respectively. Preferably, in step S2, the reactive metal binder is one of Fe-Cr-B-Si or Ni-Cr-B-Si alloy powder with a particle size of 5-15 μm, the pore-forming agent is one of starch, polyvinyl alcohol microspheres or ammonium bicarbonate, and the inorganic binder is sodium silicate solution.

[0009] Based on the characteristics of each layer of ceramic particles, specific amounts of reactive metal binder and pore-forming agent are added. The melting point of the reactive metal binder powder is lower than the temperature of the casting molten metal. It can melt during pouring and react with the ceramic particles and casting metal. The content of reactive metal binder is higher in the inner layer and lower in the outer layer, which can strengthen the internal bonding. In subsequent processes, the pore-forming agent decomposes when heated to form interconnected pore channels. The content of pore-forming agent is higher in the middle layer to form through channels, and slightly lower in the inner and outer layers to ensure the hardness of the outer layer and the conductivity of the inner layer, respectively.

[0010] Preferably, the two-stage sintering in step S2 is to first perform low-temperature sintering at 300-500℃ for 1-2 hours, followed by medium-temperature sintering at 800-1000℃ for 30-60 minutes. The first stage of low-temperature calcination is to remove pore-forming agents and moisture, forming a three-dimensional interconnected pore network. The second stage of medium-temperature sintering allows the metal binder particles to be initially sintered, giving the preform sufficient handling strength while maintaining 30%-50% open porosity. S3. Shaping and preheating: Preheat the sintered gradient ceramic preform to 800-1000℃, and then fix it in the mold cavity of the hammer head end face of the casting mold to ensure that the fine particle layer is the impact working surface. S4. Casting and reactive infiltration: The molten high-toughness alloy steel is poured into the mold at a temperature of 1600-1650℃, and 0.5-2MPa pressure is applied during the casting process to assist in infiltration. Preferably, the high-toughness alloy steel in step S4 is one of 42CrMo, 40CrNiMo, 35CrMo, 35CrMnSi or 30CrMnTi. High-temperature molten metal penetrates into the pores of the preform and melts the reactive metal binder therein. Together with the metal binder, it reacts with the surface of the ceramic particles to form a metallurgical bonding interface.

[0011] S5. Cooling, cleaning and heat treatment: After the casting is cooled to room temperature in the mold, it is removed from the sand and cleaned to obtain the hammer blank, and then the hammer blank is heat treated. Preferably, the heat treatment in step S5 is to first heat the hammer blank to 850-880℃, hold it at that temperature for 2-3 hours to austenitize it, then perform oil quenching, then temper it at 420-480℃ for 2-3 hours, and finally air cool it to room temperature. Compared to water quenching, oil quenching after austenitization is a gentler cooling process, which can effectively prevent the composite interface from cracking due to stress concentration. The subsequent tempering process enables the metal matrix to obtain tempered sorbite structure, achieving a combination of high strength and toughness.

[0012] S6. Machining: Perform necessary machining on the heat-treated hammer, including grinding, drilling, and shaping, to meet the final dimensional and geometric tolerance requirements and obtain the finished gradient hardness composite ceramic hammer.

[0013] This invention also proposes a gradient hardness composite ceramic hammer prepared by the above method. The hammerhead end face forms a gradient composite layer with continuously decreasing hardness from the surface to the interior. The total thickness of the gradient composite layer is 20-35 mm, wherein the thickness of the fine-particle high-hardness layer is 5-9 mm, the thickness of the medium-particle transition layer is 6-12 mm, and the thickness of the coarse-particle strong bonding layer is 8-14 mm. There is an interface transition zone between the composite layer and the metal substrate, which is composed of borides and silicides generated by the reaction. The thickness of the transition zone is 10-100 μm. The entire gradient composite layer achieves a strong metallurgical bond with the substrate.

[0014] Compared with the prior art, the beneficial effects of the present invention are: (1) A three-dimensional gradient of hardness was achieved: By designing three layers of ceramic preforms with different particle sizes and metal contents, a hardness transition from ultra-high hardness surface layer to high toughness matrix was successfully constructed, which effectively avoided abrupt performance changes and suppressed the initiation and propagation of cracks.

[0015] (2) Excellent impact resistance: The gradient structure can act like a "shock absorber" to gradually consume and disperse the impact stress on the working surface, which significantly improves the service life and safety of the hammer under strong impact conditions.

[0016] (3) Strong interface bonding: The gradient design of the metal binder content from the inside to the outside, and the matching design of the pore-forming agent content, make the bonding strength between the inside of the preform and the casting molten metal higher than that between the outside, forming an ideal structure of "strong inside and hard outside", which solves the problem of easy detachment of ceramic particles.

[0017] (4) Strong process feasibility: The powder layer pressing, conventional sintering and ordinary casting infiltration processes adopted are all mature technologies with low equipment requirements and controllable production costs, making them very suitable for large-scale industrial production. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the preparation method of the present invention.

[0020] Figure 2 This is a schematic diagram of the structure of the hammer of the present invention. Detailed Implementation

[0021] The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the invention. Any modifications or substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the invention. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0022] Example 1 (1) Pretreatment of ceramic particles: Prepare coarse Al2O3 particles with a particle size of 10 mesh, medium Al2O3 particles with a particle size of 20 mesh, and fine Al2O3 particles toughened by ZrO2 with a particle size of 100 mesh; first soak and clean the three types of particles in 8% oxalic acid solution to remove surface impurities, then rinse with deionized water until neutral, and finally dry at 150℃ for 4h. (2) Preparation of ceramic preforms with gradient pore structure: Fe-Cr-B-Si alloy powder with a particle size of 5 μm was selected as the reactive metal binder, starch was selected as the pore-forming agent, and sodium silicate solution was selected as the inorganic binder; the three ceramic particles were thoroughly mixed with the reactive metal binder, pore-forming agent and inorganic binder respectively, and the specific addition ratios were as follows: Fine particle layer: 1kg ZrO2 toughened Al2O3 fine particles + 50g Fe-Cr-B-Si alloy powder (5wt.%) + 50g starch (5wt.%) + 50g sodium silicate solution; Medium-particle layer: 1kg Al2O3 medium particles + 100g Fe-Cr-B-Si alloy powder (10wt.%) + 70g starch (7wt.%) + 60g sodium silicate solution (6wt.%); Coarse particle layer: 1kg Al2O3 coarse particles + 150g Fe-Cr-B-Si alloy powder (15wt.%) + 50g starch (5wt.%) + 70g sodium silicate solution (7wt.%); The material is layered into a mold with conical holes in the order of fine, medium and coarse. After being pressed and shaped under 20MPa pressure, it is dried, first held at 300℃ for 2 hours for low-temperature calcination, and then held at 800℃ for 60 minutes for medium-temperature sintering to obtain a three-dimensional gradient ceramic preform with compositional and structural gradients and a porosity of 50%. (3) Shaping and preheating: The sintered gradient ceramic preform is preheated to 800°C and then fixed in the mold cavity of the hammer head end face to ensure that the fine particle layer is the impact working surface. (4) Casting and reactive infiltration: The molten 42CrMo high-toughness alloy steel is poured into the casting mold at a temperature of 1600℃, and 0.5MPa pressure is applied during the casting process to assist in infiltration. (5) Cooling, cleaning and heat treatment: After the casting is cooled to room temperature in the mold, it is sand removed and cleaned to obtain the hammer blank. The hammer blank is first heated to 850℃ and held for 3 hours to austenitize. Then it is oil quenched and tempered at 420℃ for 3 hours. Finally, it is air cooled to room temperature. (6) Machining: Perform necessary machining on the heat-treated hammer, including grinding, drilling and shaping, to meet the final size and form and position tolerance requirements, and obtain the finished gradient hardness composite ceramic hammer.

[0023] The total thickness of the gradient composite layer of the prepared composite ceramic hammer is 20 mm, of which the thickness of the fine particle layer is 5 mm, the thickness of the medium particle layer is 6 mm, the thickness of the coarse particle layer is 9 mm, and the thickness of the interface transition zone between the composite layer and the metal substrate is 30 μm.

[0024] Example 2 (1) Pretreatment of ceramic particles: Prepare coarse Al2O3 particles with a particle size of 12 mesh, medium Al2O3 particles with a particle size of 30 mesh, and fine Al2O3 particles toughened by ZrO2 with a particle size of 150 mesh; first soak and clean the three types of particles in 8% oxalic acid solution to remove surface impurities, then rinse with deionized water until neutral, and finally dry at 175℃ for 3h. (2) Preparation of ceramic preforms with gradient pore structure: Fe-Cr-B-Si alloy powder with a particle size of 10 μm was selected as the reactive metal binder, polyvinyl alcohol microspheres were selected as the pore-forming agent, and sodium silicate solution was selected as the inorganic binder; the three ceramic particles were thoroughly mixed with the reactive metal binder, pore-forming agent and inorganic binder respectively, and the specific addition ratios were as follows: Fine particle layer: 1kg ZrO2 toughened Al2O3 fine particles + 80g Fe-Cr-B-Si alloy powder (8wt.%) + 65g polyvinyl alcohol microspheres (6.5wt.%) + 65g sodium silicate solution (6.5wt%). Medium particle layer: 1kg Al2O3 medium particles + 130g Fe-Cr-B-Si alloy powder (13wt.%) + 85g polyvinyl alcohol microspheres (8.5wt.%) + 75g sodium silicate solution (7.5wt.%); Coarse particle layer: 1kg Al2O3 coarse particles + 200g Fe-Cr-B-Si alloy powder (20wt.%) + 65g polyvinyl alcohol microspheres (6.5wt%) + 85g sodium silicate solution (8.5wt.%); The material is layered into a mold with conical holes in the order of fine, medium and coarse. After being pressed and shaped under 35MPa pressure, it is dried, first held at 400℃ for 1.5h for low-temperature calcination, and then held at 900℃ for 45min for medium-temperature sintering to obtain a three-dimensional gradient ceramic preform with compositional and structural gradients and a porosity of 40%. (3) Shaping and preheating: The sintered gradient ceramic preform is preheated to 900°C and then fixed in the mold cavity of the hammer head end face to ensure that the fine particle layer is the impact working surface. (4) Casting and reactive infiltration: The molten 40CrNiMo high-toughness alloy steel is poured into the mold at a temperature of 1625℃, and a pressure of 1.2MPa is applied during the casting process to assist in infiltration. (5) Cooling, cleaning and heat treatment: After the casting is cooled to room temperature in the mold, it is sand removed and cleaned to obtain the hammer blank. The hammer blank is first heated to 865℃ and held for 2.5h to austenitize it. Then it is oil quenched and tempered at 450℃ for 2.5h. Finally, it is air cooled to room temperature. (6) Machining: Perform necessary machining on the heat-treated hammer, including grinding, drilling and shaping, to meet the final size and form and position tolerance requirements, and obtain the finished gradient hardness composite ceramic hammer.

[0025] The total thickness of the gradient composite layer of the prepared composite ceramic hammer is 27 mm, of which the thickness of the fine particle layer is 7 mm, the thickness of the medium particle layer is 9 mm, the thickness of the coarse particle layer is 11 mm, and the thickness of the interface transition zone between the composite layer and the metal substrate is 60 μm.

[0026] Example 3 (1) Pretreatment of ceramic particles: Prepare coarse zirconium corundum particles with a particle size of 16 mesh, medium zirconium corundum particles with a particle size of 40 mesh, and fine pure ZrO2 particles with a particle size of 200 mesh; first soak and clean the three types of particles in 8% oxalic acid solution to remove surface impurities, then rinse with deionized water until neutral, and finally dry at 200℃ for 2h. (2) Preparation of ceramic preforms with gradient pore structure: Ni-Cr-B-Si alloy powder with a particle size of 15 μm was selected as the reactive metal binder, ammonium bicarbonate was selected as the pore-forming agent, and sodium silicate solution was selected as the inorganic binder; the three ceramic particles were thoroughly mixed with the reactive metal binder, pore-forming agent and inorganic binder respectively, and the specific addition ratios were as follows: Fine particle layer: 1kg pure ZrO2 fine particles + 100g Ni-Cr-B-Si alloy powder (10.wt%) + 80g ammonium bicarbonate (8wt.%) + 80g sodium silicate solution (8wt.%); Medium-particle layer: 1kg zirconium corundum medium particles + 150g Ni-Cr-B-Si alloy powder (15wt.%) + 100g ammonium bicarbonate (10wt%) + 90g sodium silicate solution (9wt.%); Coarse-grained layer: 1kg zirconium corundum coarse particles + 250g Ni-Cr-B-Si alloy powder (25.wt%) + 80g ammonium bicarbonate (8.wt%) + 100g sodium silicate solution (10wt.%); The material is layered into a mold with conical holes in the order of fine, medium and coarse. After being pressed and shaped under 50MPa pressure, it is dried, first held at 500℃ for 1 hour for low-temperature calcination, and then held at 1000℃ for 30 minutes for medium-temperature sintering to obtain a three-dimensional gradient ceramic preform with compositional and structural gradients and a porosity of 30%. (3) Shaping and preheating: The sintered gradient ceramic preform is preheated to 1000℃ and then fixed in the mold cavity of the hammer head end face to ensure that the fine particle layer is the impact working surface. (4) Casting and reactive infiltration: The molten 35CrMo high-toughness alloy steel is poured into the casting mold at a temperature of 1650℃, and 2MPa pressure is applied during the casting process to assist in infiltration. (5) Cooling, cleaning and heat treatment: After the casting is cooled to room temperature in the mold, it is sand removed and cleaned to obtain the hammer blank. The hammer blank is first heated to 880℃ and held for 2 hours for austenitization. Then it is oil quenched and tempered at 480℃ for 2 hours. Finally, it is air cooled to room temperature. (6) Machining: Perform necessary machining on the heat-treated hammer, including grinding, drilling and shaping, to meet the final size and form and position tolerance requirements, and obtain the finished gradient hardness composite ceramic hammer.

[0027] The total thickness of the gradient composite layer of the prepared composite ceramic hammer is 35 mm, of which the thickness of the fine particle layer is 9 mm, the thickness of the medium particle layer is 12 mm, the thickness of the coarse particle layer is 14 mm, and the thickness of the interface transition zone between the composite layer and the metal substrate is 100 μm.

[0028] Comparative Example 1 This comparative example uses single ceramic particles and has no gradient structure. The difference compared to Example 2 is that: (1) Pretreatment of ceramic particles: Al2O3 particles with a single particle size of 40 mesh were selected; (2) Preparation of ceramic preforms: The addition ratio of ceramic particles to reactive metal binder, pore-forming agent and inorganic binder is: 1 kg Al2O3 particles + 130 g Fe-Cr-B-Si alloy powder (13 wt.%) + 85 g polyvinyl alcohol microspheres (8.5 wt.%) + 75 g sodium silicate solution (7.5 wt.%) The prepared composite ceramic hammer has a single hardness structure with a total thickness of about 27 mm and no gradient transition. The thickness of the interfacial transition zone between the composite particles and the metal matrix is ​​50 μm.

[0029] Comparative Example 2 This comparative example does not add reactive metal binders to the preform, and differs from Example 2 in that: (2) Preparation of ceramic preforms with gradient pore structure: After thoroughly mixing the three types of ceramic particles with the pore-forming agent and inorganic binder, the specific addition ratios are as follows: Fine particle layer: 1kg ZrO2 toughened Al2O3 fine particles + 65g (6.5wt.%) polyvinyl alcohol microspheres + 65g (6.5wt%) sodium silicate solution; Medium particle layer: 1 kg Al2O3 medium particles + 85 g (8.5 wt.%) polyvinyl alcohol microspheres + 75 g (7.5 wt.%) sodium silicate solution; Coarse particle layer: 1kg Al2O3 coarse particles + 65g (6.5wt%) polyvinyl alcohol microspheres + 85g (8.5wt.%) sodium silicate solution; The total thickness of the gradient composite layer of the prepared composite ceramic hammer is 26 mm, of which the thickness of the fine particle layer is 7 mm, the thickness of the medium particle layer is 9 mm, and the thickness of the coarse particle layer is 10 mm. There is no obvious transition zone at the interface between the composite layer and the metal substrate, the metallurgical bonding effect is poor, and the interfacial bonding strength is low.

[0030] Comparative Example 3 The ceramic preform in this comparative example, after being pressed and dried, undergoes a single-stage sintering at a higher temperature. The difference compared to Example 2 is that: (2) Preparation of ceramic preforms with gradient pore structure: ceramic particles are layered and filled into a mold, pressed and dried, and then sintered at 1200℃ for 45 min to obtain gradient ceramic preforms. (3) Shaping: The sintered gradient ceramic preform is fixed directly into the cavity of the end face of the hammer head of the casting mold without preheating; (4) Casting: The molten 40CrNiMo high-toughness alloy steel is poured into the casting mold at a temperature of 1625℃ without applying pressure to assist casting infiltration; The total thickness of the composite ceramic hammer gradient composite layer is 26 mm, of which the fine particle layer is 6 mm thick, the medium particle layer is 8 mm thick, the coarse particle layer is 12 mm thick, and the thickness of the interface transition zone between the composite layer and the metal substrate is 50 μm. However, due to the low porosity of the hammer preform (less than 20%), the metal liquid does not penetrate sufficiently, the interface bonding is poor, and the gradient layer is easy to peel off.

[0031] The bonding strength between the ceramic layer and the metal substrate was measured using a shear testing machine. Tensile tests were performed on the metal substrate to obtain its tensile strength. Using a standard high-manganese steel hammer as a reference (abrasion resistance 1), relative values ​​were calculated through impact abrasion tests. The interfacial bonding was observed using a scanning electron microscope (SEM). The performance tests and microstructure observation results of the material samples prepared in the examples and comparative examples are shown in Table 1.

[0032] Table 1 Performance tests and tissue observations of the examples and comparative examples Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A gradient hardness composite ceramic drop weight, characterized by, The hammer head end face of the drop hammer is formed with a gradient composite layer with continuously decreasing hardness from the surface to the inside, the total thickness of the gradient composite layer is 20-35 mm, the thickness of the fine particle high hardness layer is 5-9 mm, the thickness of the medium particle transition layer is 6-12 mm, and the thickness of the coarse particle strong bonding layer is 8-14 mm.

2. The gradient hardness composite ceramic dart of claim 1, wherein, There is an interface transition zone composed of reaction generated boride and silicide between the composite layer and the metal matrix, the thickness of the transition zone is 10-100 μm, and the whole gradient composite layer is metallurgically bonded with the matrix.

3. A method of manufacturing a gradient hardness composite ceramic flyer according to any one of claims 1-2, characterized in that, The preparation method comprises the following steps: S1, ceramic particle pretreatment: prepare coarse, medium and fine ceramic particles with different particle sizes and hardness, and pretreat the ceramic particles respectively; S2, preparation of ceramic preform with gradient porosity structure: after the three kinds of ceramic particles are fully mixed with specific proportions of reactive metal binder, pore forming agent and inorganic binder respectively, they are loaded into a mold with a conical hole in the order of fine, medium and coarse, and then molded under a pressure of 20-50 MPa, dried and sintered in two stages to obtain a three-dimensional gradient ceramic preform with gradient composition and structure; S3, molding and preheating: preheat the sintered gradient ceramic preform to 800-1000℃, then fix it in the hammer head end face cavity of the casting mold, and ensure that the fine particle layer is the impact working surface; S4, pouring and reaction infiltration: pour the high toughness alloy liquid prepared by smelting into the mold at a temperature of 1600-1650℃, and apply a pressure of 0.5-2 MPa during pouring to assist the infiltration; S5, cooling, cleaning and heat treatment: after the casting is cooled to room temperature in the mold, it is knocked out and cleaned to obtain a drop hammer blank, and the drop hammer blank is heat treated; S6, machining: the heat treated drop hammer is subjected to necessary mechanical processing, which includes grinding, drilling and shaping to meet the final size and shape tolerance requirements, and a finished gradient hardness composite ceramic drop hammer is obtained.

4. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: In step S1, the coarse and medium particles are one of Al2O3 or zirconia corundum, the particle size of the coarse particles is 8-16 mesh, the particle size of the medium particles is 20-40 mesh, and the fine particles are one of ZrO2 toughened Al2O3 or pure ZrO2, and the particle size of the fine particles is 100-200 mesh.

5. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: In step S1, the pretreatment is first soaking and cleaning with 5-10% oxalic acid solution to remove surface impurities, then rinsing with deionized water to neutral, and finally drying at 150-200℃ for 2-4h.

6. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: In step S2, the specific proportions are that the addition amounts of the reactive metal binder, pore forming agent and inorganic binder for the fine particles are 5-10.wt%, 5-8.wt% and 5-8.wt% of the mass of the fine particles respectively, the addition amounts of the reactive metal binder, pore forming agent and inorganic binder for the medium particles are 10-15.wt%, 7-10.wt% and 6-9.wt% of the mass of the medium particles respectively, and the addition amounts of the reactive metal binder, pore forming agent and inorganic binder for the coarse particles are 15-25.wt%, 5-8.wt% and 7-10.wt% of the mass of the coarse particles respectively.

7. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: The reactive metal binder in the step S2 is one of Fe-Cr-B-Si or Ni-Cr-B-Si alloy powder, the powder particle size is 5-15 μm, the pore-forming agent is one of starch, polyvinyl alcohol microspheres or ammonium bicarbonate, and the inorganic binder is sodium silicate solution.

8. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: The two-stage sintering in the step S2 is low-temperature calcination at 300-500 ℃ for 1-2 h, and then medium-temperature sintering at 800-1000 ℃ for 30-60 min.

9. The method for preparing the gradient hardness composite ceramic hammer according to claim 3, characterized in that, The high-toughness alloy steel in the step S4 is one of 42CrMo, 40CrNiMo, 35CrMo, 35CrMnSi or 30CrMnTi.

10. The method of claim 3, wherein the gradient hardness composite ceramic flyer is prepared by the steps of: providing a ceramic material; providing a metal material; and combining the ceramic material and the metal material to form the gradient hardness composite ceramic flyer. The heat treatment in the step S5 is austenitizing by heating the spun hammer blank to 850-880 ℃ and holding for 2-3 h, then oil quenching, tempering at 420-480 ℃ and holding for 2-3 h, and air cooling to room temperature.

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