High-toughness ZTA ceramic material applied to high-impact hammer head and preparation method of high-toughness ZTA ceramic material

Abstract

The invention discloses a high-toughness ZTA ceramic material applied to a high-impact hammerhead and a preparation method of the high-toughness ZTA ceramic material. The material contains the following components in percentage by weight: 80%-85% of alpha-Al2O3, 15%-20% of 3Y-TZP, 0.5%-1% of Cr2O3, 0.5%-1% of TiO2 and 1%-2% of reinforced phase carboxylated carbon nanotubes or graphene. The preparation method comprises the steps of raw material pretreatment, composite powder synthesis, mixing dispersion, molding, sintering and surface treatment. The high-impact hammer head prepared from the material is long in service life, can effectively reduce the production cost and the downtime, and has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hammerhead ceramic materials, in particular to a high-toughness ZTA ceramic material applied to high-impact hammerheads and a preparation method thereof. BACKGROUND

[0002] In the mining, construction and other industries, the hammerheads of crushers, sand making machines and other equipment need to withstand severe impact and wear. Although the traditional metal hammerheads have a certain toughness, they have poor wear resistance, short service life and need to be frequently replaced, which increases the production cost and downtime. Ceramic materials have excellent wear resistance, but they are brittle and have low toughness, which limits their application in the field of hammerheads. ZTA ceramics improve the toughness of alumina ceramics to some extent through phase transformation toughening of zirconia, but the toughness and impact resistance of existing ZTA ceramic materials still cannot meet the use requirements of high-impact hammerheads. Therefore, it is of great significance to develop a ZTA ceramic material with high toughness, high wear resistance and good impact resistance for improving the service life of hammerheads and reducing production costs. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to provide a high-toughness ZTA ceramic material applied to high-impact hammerheads and a preparation method thereof, to avoid the poor wear resistance and impact resistance of previous hammerheads.

[0004] To solve the above technical problems, the present application discloses a high-toughness ZTA ceramic material applied to high-impact hammerheads, which consists of the following components in terms of mass fraction: α-Al2O3: 80-85%, purity ≥ 99.96%, average particle size ≤ 1 μm; 3Y-TZP: 15-20%, purity ≥ 99.9%, average particle size 50-80 nm, tetragonal phase content ≥ 90%; Cr2O3: 0.5-1%, purity ≥ 99.0%; TiO2: 0.5-1%, purity ≥ 98.0%; Reinforcing phase: 1-2%, which is carboxylated multi-walled carbon nanotubes or graphene nanosheets; Among them, the carboxylated multi-walled carbon nanotubes have a diameter of 10-20 nm, a length of 5-15 μm, and a -COOH group density of ≥ 2.5 at%; the graphene nanosheets have a thickness of ≤ 5 nm and a diameter of 5-10 μm.

[0005] Further, the specific surface area of 3Y-TZP is 10-20 m 2 / g, and the impurity content meets Fe2O3 < 0.003%, SiO2 < 0.002%.

[0006] The application further discloses a preparation method of the high-toughness ZTA ceramic material applied to a high-impact hammer head. Step a. raw material pretreatment: mixing multi-walled carbon nanotubes with a mixed solution of concentrated H2SO4 and HNO3 at a volume ratio of 3:1 according to a solid-liquid ratio of 1:50, ultrasonic dispersing in a 60℃ water bath at a power of 300W for 2h, centrifugal washing until pH=6-7, and vacuum drying at 80℃ for 12h; or mixing graphene nanosheets with N-methylpyrrolidone according to a ratio of 1:50, adding 5mm zirconia balls (ball-to-material ratio of 5:1), and performing planetary ball milling at 300r / min for 24h, and taking the upper suspension for freeze drying; Step b. composite powder synthesis: dissolving Al(NO3)3·9H2O and ZrOCl2·8H2O in deionized water according to a ratio, adding Y2O3 powder and ultrasonic dispersing for 30min, adding 0.5mol / L Cr(NO3)3 solution and tetrabutyl titanate ethanol solution dropwise, and stirring for 1h; adjusting pH to 3.5±0.2 by using 1:1 ammonia water, stirring in a 60℃ water bath for 2h to form a sol, drying at 80℃ for 24h to obtain a dry gel, crushing, and calcining at 500℃×2h and 900℃×3h; Step c. mixing and dispersing: adding the calcined powder and the modified reinforcing phase into a planetary ball mill, adding anhydrous ethanol and 5mm zirconia balls (ball-to-material ratio of 8:1) according to a liquid-to-solid ratio of 2:1, ball milling at 300r / min for 4h, and freeze drying and then sieving through a 200-mesh screen; Step d. forming: dry pressing the composite powder at 50MPa for 30s, and then cold isostatic pressing at 200MPa for 5min; Step e. sintering: adopting discharge plasma sintering or microwave sintering; Step f. surface treatment: sequentially performing salt bath titanium plating, chemical nickel plating and rubber composite treatment.

[0007] Further, the discharge plasma sintering process in the step e. is as follows: room temperature→500℃: 100℃ / min, 10MPa; 500℃→1000℃: 50℃ / min, 20MPa; 1000℃→1350℃: 30℃ / min, 30MPa; holding at 1350℃ for 3min and then furnace cooling.

[0008] Further, the microwave sintering process in the step e. is as follows: heating to 1450℃ at a rate of 50℃ / min, holding for 40min in an air atmosphere, and furnace cooling at a rate of 20℃ / min before 600℃.

[0009] Further, the salt bath titanium plating process in step f is: sintered ceramic is kept in a 750℃ molten salt bath (Na2TiF6 50wt%+NaCl 30wt%+KCl 20wt%) for 30min, and then quenched in cold water.

[0010] Further, the chemical nickel plating process in step f is: in a plating solution containing NiSO4·6H2O 2:5g / L, NaH2PO2·H2O 20g / L, sodium citrate 15g / L, and ammonium chloride 30g / L, the plating is carried out under the conditions of pH=5.0 and 85℃ for 4h, and then dried at 120℃ for 1h.

[0011] Further, the rubber compounding process in step f is: 5wt% KH550 ethanol solution is coated on the nickel-plated surface, dried at 80℃ for 30min, and then vulcanized with nitrile rubber containing 2wt% sulfur at 160℃ and 10MPa for 30min to form a 2-5mm thick rubber layer.

[0012] Compared with the prior art, the application can obtain the following technical effects: The ZTA ceramic material of the application has high toughness, high hardness and excellent wear resistance by reasonably matching the proportions of α-Al2O3, 3Y-TZP, Cr2O3, TiO2 and the reinforcing phase, and controlling the performance parameters of each component. In the preparation method, the pretreatment of the raw materials can improve the dispersibility of the reinforcing phase and the compatibility with the matrix; the sol-gel method is used for the synthesis of the composite powder, which can obtain uniform and fine powder; the optimization of the forming and sintering process can improve the density and performance of the material; and the surface treatment further improves the impact resistance and use effect of the material. The high-impact hammer head made of the material has a long service life, can effectively reduce the production cost and downtime, and has a wide application prospect.

[0013] Of course, any product implementing the application does not necessarily need to achieve all the technical effects described above. DETAILED DESCRIPTION

[0014] The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiments of the application and together with the description serve to explain the application. In the drawings: Figure 1 is a high-toughness ZTA ceramic material preparation method flow chart for a high-impact hammer head according to an embodiment of the application. DETAILED DESCRIPTION

[0015] The embodiments of the present application will be described in detail below with the accompanying drawings and examples, so that the implementation process of how the present application applies technical means to solve technical problems and achieves technical effects can be fully understood and implemented.

[0016] Example 1: Carboxylated multi-walled carbon nanotubes as reinforcing phase.

[0017] Raw material preparation: α-Al2O3: purity 99.96%, average particle size 0.8 μm, mass fraction 82%; 3Y-TZP: purity 99.9%, average particle size 60 nm, tetragonal phase content 92%, specific surface area 15 m 2 / g, Fe2O3<0.002%, SiO2<0.001%, mass fraction 17%; Cr2O3: purity 99.0%, mass fraction 0.5%; TiO2: purity 98.0%, mass fraction 0.5%; Multi-walled carbon nanotubes: diameter 15 nm, length 10 μm, mass fraction 1%.

[0018] Step a. Pretreatment of raw materials 1g of multi-walled carbon nanotubes was added to a beaker with 50mL of a mixed solution of concentrated H2SO4:HNO3 with a volume ratio of 3:1, and placed in a 60°C water bath for ultrasonic dispersion at a power of 300W for 2h. Then the mixed solution was transferred to a centrifuge tube and washed with deionized water by centrifugation at a speed of 3000r / min for 10min each time until the pH value of the supernatant reached 6.5. The treated carbon nanotubes were placed in a vacuum drying oven and dried at 80°C for 12h to obtain carboxylated multi-walled carbon nanotubes, which were detected to have a -COOH group density of 2.8at%.

[0019] Step b. Synthesis of composite powder The calculated amount of Al(NO3)3·9H2O and ZrOCl2·8H2O was weighed and dissolved in 100mL of deionized water, and stirred until completely dissolved.

[0020] The corresponding amount of Y2O3 powder was added and ultrasonically dispersed in an ultrasonic cleaner for 30min.

[0021] 0.5mol / L Cr(NO3)3 solution and titanium tetrabutoxide diluted 10 times with anhydrous ethanol were added dropwise, and stirring was continued for 1h.

[0022] The pH of the solution was slowly adjusted to 3.5 with 1:1 ammonia water, and stirring was continued in a 60°C water bath for 2h to form a uniform sol.

[0023] Pour the sol into a petri dish and dry in an 80°C oven for 24h to obtain a dry gel block.

[0024] Crush the dry gel and put it into a corundum crucible, and calcine in a muffle furnace at 500°C for 2h (heating rate 5°C / min), then increase the temperature to 900°C for 3h (heating rate 5°C / min), and obtain the composite powder after natural cooling.

[0025] Step c. Mixing and dispersing Put 82g of the calcined composite powder and 1g of the pretreated carboxylated multi-walled carbon nanotubes into the ball mill tank of a planetary ball mill, add anhydrous ethanol at a liquid-solid ratio of 2:1, and then add 5mm zirconia balls (ball-to-material ratio 8:1). Tighten the ball mill tank and install it on the planetary ball mill, and mill at a speed of 300r / min for 4h. After the ball milling is completed, pour the slurry into an evaporation dish and freeze-dry it (-50°C, vacuum degree 10Pa) for 24h. Screen the dried powder through a 200 mesh sieve and reserve it for use.

[0026] Step d. Shaping Dry pressing pre-forming: Put the mixed powder into a 100x50x20mm mold, place it on a hydraulic press, and apply a pressure of 50MPa for 30s to obtain a green body.

[0027] Cold isostatic pressing: Wrap the dry-pressed green body tightly with plastic film and place it in the high-pressure chamber of a cold isostatic pressing machine. Apply a pressure of 200MPa for 5min at a pressure release rate of 5MPa / min to obtain a green body with a density of 72%.

[0028] Step e. Sintering Discharge plasma sintering: Put the green body into a BN-coated graphite mold and fill it with graphite powder.

[0029] Put the mold into an SPS-2000 discharge plasma sintering furnace and set the program: room temperature→500°C, heating rate 100°C / min, pressure 10MPa; 500°C→1000°C, heating rate 50°C / min, pressure 20MPa; 1000°C→1350°C, heating rate 30°C / min, pressure 30MPa; 1350°C for 3min.

[0030] After the holding is completed, turn off the power and cool the furnace to room temperature, and then take out the sintered body.

[0031] Step f. Surface treatment Salt bath titanium plating: After sintering, the surface of the ceramic was polished with 800 grit sandpaper and ultrasonically cleaned with anhydrous ethanol for 10 min. Na2TiF6 50 g, NaCl 30 g, and KCl 20 g were added to a crucible, heated to 750°C to melt, and the ceramic sample was placed in it. After 30 min of heat preservation, it was taken out and immediately placed in cold water to quench. The surface residual salt was removed and dried at 80°C.

[0032] Electroless nickel plating: A plating solution was prepared (NiSO4・6H2O 2: 5 g / L, NaH2PO2・H2O 20 g / L, sodium citrate 15 g / L, ammonium chloride 30 g / L), and the pH was adjusted to 5.0. The titanium-plated ceramic was placed in the plating solution and plated at 85°C with stirring (100 r / min) for 4 h. After removal, it was rinsed with deionized water and dried at 120°C for 1 h.

[0033] Rubber compounding: A 5wt% KH550 ethanol solution was uniformly coated on the nickel-plated surface and dried at 80°C for 30 min. Butadiene rubber containing 2wt% sulfur was placed in a mold, and the ceramic was embedded in it. Sulfurization was carried out at 160°C and 10 MPa for 30 min to form a 3 mm thick rubber layer.

[0034] The properties of the resulting material were measured as follows: Fracture toughness: 6.8 MPa・m 1 / 2 Hardness: HRA 89 Impact strength: 16.5 kJ / m 2 Wear rate: 4.2 × 10 -6 mm 3 / (N・m) Density: 99.6% Example 2, with graphene nanosheets as the reinforcing phase.

[0035] Raw material preparation α-Al2O3: purity 99.96%, average particle size 0.9 μm, mass fraction 80%; 3Y-TZP: purity 99.9%, average particle size 70 nm, tetragonal phase content 90%, specific surface area 12 m 2 / g, Fe2O3<0.003%, SiO2<0.002%, mass fraction 18%; Cr2O3: purity 99.0%, mass fraction 1%; TiO2: purity 98.0%, mass fraction 1%; Graphene nanosheets: initial thickness 10 nm, diameter 8 μm, mass fraction 2%.

[0036] Step a. Raw material pretreatment 2g graphene nanosheets and 100mL N-methylpyrrolidone were added to a ball mill tank, 5mm zirconia balls were added (ball to material ratio 5:1), installed on a planetary ball mill, 300r / min ball milling for 24h. After ball milling, stand for 12h, take the upper suspension, rotary evaporation to remove NMP, then freeze-drying (-50℃, vacuum degree 10Pa) for 24h, get graphene nanosheets with thickness ≤5nm.

[0037] Steps b-e. Composite powder synthesis, mixing and dispersion, molding, sintering.

[0038] The steps are the same as Example 1, and microwave sintering is used for sintering: The green body is buried and sintered with zirconia powder, and placed in a MICROSINTERWAVE P7515 continuous microwave sintering furnace.

[0039] Set the program: heat to 1450℃ at a rate of 50℃ / min, keep in air atmosphere for 40min, cool down with the furnace at a rate of 20℃ / min before 600℃.

[0040] Step f. Surface treatment The steps are the same as Example 1, and the thickness of the rubber composite layer is 4mm.

[0041] The performance of the obtained material is as follows: Fracture toughness: 7.2MPa・m 1 / 2 Hardness: HRA88.5 Impact strength: 17.3kJ / m 2 Wear rate: 3.8×10 -6 mm 3 / (N・m) Density: 99.2% Example 3, preparation of high-impact hammer head.

[0042] The ZTA ceramic material prepared in Example 1 is used to make a high-impact hammer head, and the specific steps are as follows: According to the design size of the hammer head (such as 200×100×50mm), a mold is made, and the ceramic body is prepared according to the process of Example 1 and sintered and surface treated.

[0043] The treated ceramic block is connected with the hammer head base (using high chromium cast iron) by welding, and the ceramic material is located on the impact working surface of the hammer head.

[0044] The connected hammer head is polished and polished as a whole to remove burrs and excess parts.

[0045] The hammer head is tested on a mine crusher, and compared with a traditional high-chromium cast iron hammer head, the service life is prolonged by 4 times, and the replacement frequency and production cost are significantly reduced.

[0046] The foregoing description shows and describes several preferred embodiments of the present application, but it is understood that the application is not limited to the forms disclosed, but is to cover modifications and equivalents thereof which come within the scope of the invention as defined by the appended claims.

Claims

1. A high-toughness ZTA ceramic material for use in high-impact hammerheads, characterized in that, By mass fraction, it consists of the following components: α-Al₂O₃: 80-85%, purity ≥99.96%, average particle size ≤1μm; 3Y-TZP: 15-20%, purity ≥99.9%, average particle size 50-80nm, tetragonal phase content ≥90%; Cr2O3: 0.5-1%, purity ≥99.0%; TiO2: 0.5-1%, purity ≥98.0%; Reinforcing phase: 1-2%, consisting of carboxylated multi-walled carbon nanotubes or graphene nanosheets; The carboxylated multi-walled carbon nanotubes have a diameter of 10-20 nm, a length of 5-15 μm, and a -COOH group density of ≥2.5 at; the graphene nanosheets have a thickness of ≤5 nm and a diameter of 5-10 μm.

2. The high-toughness ZTA ceramic material for high-impact hammerheads according to claim 1, characterized in that, The specific surface area of ​​the 3Y-TZP is 10-20 m². 2 / g, with impurity content satisfying Fe2O3<0.003% and SiO2<0.002%.

3. A method for preparing a high-toughness ZTA ceramic material for use in high-impact hammerheads, characterized in that, include: Step a. Raw material pretreatment: Mix multi-walled carbon nanotubes with a concentrated H2SO4:HNO3 mixture with a volume ratio of 3:1 at a solid-liquid ratio of 1:50, ultrasonically disperse in a 60℃ water bath at 300W power for 2 hours, centrifuge and wash until pH=6-7, and vacuum dry at 80℃ for 12 hours. Alternatively, graphene nanosheets can be mixed with N-methylpyrrolidone at a ratio of 1:50, and 5mm zirconia balls can be added (ball-to-material ratio 5:1). The mixture can be ball-milled at 300r / min for 24h, and the upper suspension can be freeze-dried. Step b. Composite powder synthesis: Al(NO3)3・9H2O and ZrOCl2・8H2O were dissolved in deionized water in a certain proportion, Y2O3 powder was added and ultrasonically dispersed for 30 min, 0.5 mol / L Cr(NO3)3 solution and tetrabutyl titanate ethanol solution were added dropwise, and the mixture was stirred for 1 h; the pH was adjusted to 3.5±0.2 with 1:1 ammonia water, and the mixture was stirred in a 60℃ water bath for 2 h to form a sol, dried at 80℃ for 24 h to obtain a dry gel, pulverized and calcined at 500℃ for 2 h and 900℃ for 3 h. Step c. Mixing and dispersing: Add the calcined powder and the modified reinforcing phase to a planetary ball mill, add anhydrous ethanol and 5mm zirconia balls at a liquid-to-solid ratio of 2:1 (ball-to-material ratio of 8:1), ball mill at 300r / min for 4h, freeze dry and pass through a 200-mesh sieve; Step d. Molding: The composite powder is pre-molded by dry pressing at 50MPa for 30s, and then subjected to cold isostatic pressing at 200MPa for 5min; Step e. Sintering: Using spark plasma sintering or microwave sintering; Step f. Surface treatment: Salt bath titanium plating, electroless nickel plating, and rubber composite treatment are performed in sequence.

4. The method for preparing high-toughness ZTA ceramic material for high-impact hammerheads according to claim 3, characterized in that, The spark plasma sintering process in step e is as follows: Room temperature → 500℃: 100℃ / min, 10MPa; 500℃→1000℃: 50℃ / min, 20MPa; 1000℃→1350℃: 30℃ / min, 30MPa; Hold at 1350℃ for 3 minutes and then cool with the furnace.

5. The method for preparing high-toughness ZTA ceramic material for high-impact hammerheads according to claim 3, characterized in that, The microwave sintering process in step e is as follows: heating to 1450°C at a rate of 50°C / min, holding at that temperature in air for 40 min, and cooling with the furnace at a rate of 20°C / min before reaching 600°C.

6. The method for preparing high-toughness ZTA ceramic material for high-impact hammerheads according to claim 3, characterized in that, The salt bath titanium plating process in step f is as follows: the sintered ceramic is kept in a molten salt bath (Na2TiF650wt%+NaCl30wt%+KCl20wt%) at 750℃ for 30 minutes, and then quenched in cold water.

7. The method for preparing high-toughness ZTA ceramic material for high-impact hammerheads according to claim 3, characterized in that, The electroless nickel plating process in step f is as follows: in a plating solution containing NiSO4・6H2O2: 5g / L, NaH2PO2・H2O: 20g / L, sodium citrate: 15g / L, and ammonium chloride: 30g / L, the plating is stirred and plated for 4 hours at pH=5.0 and 85℃, and then dried at 120℃ for 1 hour.

8. The method for preparing high-toughness ZTA ceramic material for high-impact hammerheads according to claim 3, characterized in that, The rubber composite process in step f is as follows: a 5wt% KH550 ethanol solution is coated on the nickel-plated surface, dried at 80°C for 30 min, and then vulcanized with nitrile rubber containing 2wt% sulfur at 160°C and 10MPa for 30 min to form a 2-5mm thick rubber layer.

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