High-compactness silicon nitride bearing ball and preparation method thereof

Abstract

The invention discloses a high-compactness silicon nitride bearing ball and a preparation method thereof, and belongs to the technical field of ceramic products. The high-alpha-phase Si3N4 powder is a main material of the silicon nitride bearing ball, the ALN is used for further improving the wear resistance of the material, the Y2O3 is used for improving the compactness of the silicon nitride bearing ball, pores can be seen under the action of a 0.5 mu m electron microscope after the Y2O3 is added, the MgO is used for promoting the alpha-phase Si3N4 powder to be converted into a beta phase, and the Li2O and the La2O3 form a high-temperature liquid phase to promote the densification of the bearing ball. According to the preparation method, by means of the solubility of the organic solvent to silicon nitride, part of silicon nitride is dissolved in the solution, the surface layer of the silicon nitride powder is further softened, and tiny bubbles in the silicon nitride powder are removed in a negative pressure pumping mode; the silicon nitride is separated out on the surface of the silicon nitride powder in a solvent evaporation manner, so that the shape of the silicon nitride powder is further improved and adjusted, and finally, the bearing ball with higher compactness is obtained.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic products, and in particular to a high-density silicon nitride bearing ball and a preparation method thereof. Background Art

[0002] In the field of modern industry and science and technology, bearing balls are key components, and their performance directly affects the operating efficiency and service life of mechanical equipment. As an advanced ceramic material, silicon nitride has shown significant performance advantages in the application of bearing balls due to its excellent physical and chemical properties. Silicon nitride bearing balls have shown broad application prospects in the field of modern industry and science and technology with their excellent performance characteristics such as high hardness, high temperature stability, corrosion resistance, light weight, low friction and quietness. With the continuous advancement of technology and the continuous expansion of the market, silicon nitride bearing balls will play an important role in more fields and provide strong support for technological progress and equipment upgrades in various industries.

[0003] With the continuous advancement of science and technology and the continuous development of the market, the demand for high-performance silicon nitride ceramic bearing balls is increasing. Silicon nitride ceramic bearing balls may form more microscopic pores and crack sources during the preparation process, and these defects will reduce the hardness and wear resistance of the material. The development of densification technology can optimize the sintering process, reduce these defects, and thus improve the hardness and wear resistance of the material. The development of densification technology will help improve the performance and quality of products and meet the needs of high-end application fields. Summary of the invention

[0004] The object of the present invention is to provide a high-density silicon nitride bearing ball and a preparation method thereof. The present invention dissolves part of the silicon nitride powder in the solution by a solvent, brings extremely small powder particles into the pores of the powder by the solvent, and slowly evaporates the solvent to achieve the effect of reducing the porosity of the silicon nitride powder.

[0005] A high-density silicon nitride bearing ball and a preparation method thereof, characterized in that the steps are: S1. Put Si3N4 powder with α-phase content higher than 70%, AlN, Y2O3, MgO, Li2O, La2O3 and sintering aid into a ball mill for ball milling until all particles have a particle size of <0.5 μm to prepare a mixed powder. In this step, Si3N4 powder with high α-phase is the main material of silicon nitride bearing balls, AlN is used to further improve the wear resistance of the material, Y2O3 is used to improve the compactness of silicon nitride bearing balls, and after adding Y2O3, pores can be seen under an electron microscope of 1 μm, MgO is used to promote the transformation of Si3N4 powder with α-phase to β-phase, and Li2O and La2O3 form a liquid phase at high temperature to promote the densification of bearing balls.

[0006] S2, take out the mixed powder and put it into a container, pour an organic solvent in an amount exceeding the mass of the mixed powder into the container, stir evenly, put the container into a vacuum furnace for vacuum treatment, and let the container stand in a vacuum state for more than 12 hours. In this step, the solubility of the organic solvent in silicon nitride is used to dissolve part of the silicon nitride in the solution, thereby further softening the performance of the surface layer of the silicon nitride powder.

[0007] S3. Take out the container after vacuum standing, stir evenly, put it into a distillation device with negative pressure and heating function, heat the distillation device, and slowly distill the organic solvent out, while maintaining the negative pressure state in the distillation device, and distill until the mass fraction of the organic solvent is 10%-40%. In this step, the tiny bubbles in the silicon nitride powder are removed by drawing negative pressure; by evaporating the solvent, silicon nitride is deposited on the surface of the silicon nitride powder, further improving the shape of the silicon nitride powder itself, and laying a good foundation for further densification.

[0008] S4, take out the wet powder containing organic solvent in the container, pour the wet powder into two hemispherical molds, apply pressure to mold into a spherical body; while keeping the pressure applied, put the spherical body into a distillation device for negative pressure heating until the spherical body is dry and stop the negative pressure heating. In this step, the remaining organic solvent is squeezed out by physical pressure, and a high temperature negative pressure state is maintained. While removing the organic solvent, negative pressure is formed inside the powder, and positive pressure is applied outside to achieve the overall densification of the material.

[0009] S5, cold isostatic pressing the spherical green body; S6, sintering the spherical blank, the sintering process is carried out in a nitrogen atmosphere, the sintering temperature is 1700° C.-1900° C., the sintering pressure is 4 atm-30 atm, the sintering time is 48h-96h, and the sintered blank is a silicon nitride blank; S7. Machining the silicon nitride blank to prepare bearing balls of required sizes.

[0010] Furthermore, the mass fraction ratio of Si3N4 powder, AlN, Y2O3, MgO, Li2O, La2O3 and sintering aid is (80-88):(3-7.0):(3-7):(1-5):(1-5):(1-5):(1-3).

[0011] Furthermore, the organic solvent in step S2 is one or a combination of two or three of toluene solution, acetone and butanone.

[0012] Furthermore, in step S2, the distillation temperature is 60° C.-200° C., and the distillation time is greater than 12 hours per kilogram of organic solvent.

[0013] Furthermore, in step S4, the edge area of ​​the hemispherical mold has a toothed structure.

[0014] Furthermore, in step S4, the negative pressure heating temperature is 120° C.-300° C., and the distillation time is 0.5 h-2 h. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the specific implementation of the present invention or the technical solution in the prior art, the drawings required for use in the specific implementation or the description of the prior art will be briefly introduced below.

[0016] Figure 1 This is a SEM image of a cross-section of a bearing ball prepared in the present invention; Figure 2 This is the SEM image of the cross section of the bearing ball prepared by the original process. DETAILED DESCRIPTION

[0017] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention. Example

[0018] Si3N4 powder with an α phase content higher than 70%, AlN, Y2O3, MgO, Li2O, La2O3, and sintering aids in a mass fraction ratio of 80:4:5:5:3:1:1:1 were put into a ball mill for ball milling until the particle size of all particles was less than 0.5 μm, and 0.8 kg of mixed powder was prepared.

[0019] Take out the mixed powder and put it into a container. Pour 1.2 kg of butanone into the container and stir evenly. Put the container into a vacuum furnace for vacuum treatment and let it stand for 24 hours under vacuum.

[0020] Take out the container after vacuum standing, stir it evenly, put it into a distillation device with negative pressure and heating functions, heat the distillation equipment, and slowly distill the organic solvent out while maintaining the negative pressure in the distillation equipment until the mass fraction of the organic solvent is 10%.

[0021] Take out the wet powder containing organic solvent in the container, pour the wet powder into two hemispherical molds, the hemispherical molds are claw-shaped, the claws protect the powder from being scattered when it is squeezed, and the pressure can be continuously applied after the solvent is squeezed out. Apply pressure to mold it into a spherical body; while keeping the pressure applied, put the spherical body into the distillation equipment for negative pressure heating until the spherical body is dry and the negative pressure heating is stopped.

[0022] The spherical green body is subjected to cold isostatic pressing.

[0023] The spherical green body is sintered in a nitrogen atmosphere at a sintering temperature of 1750°C, a sintering pressure of 20 atm, and a sintering time of 72 hours to obtain a silicon nitride green body.

[0024] The silicon nitride blank obtained in Example 1 was cut with a diamond wire and scanned with a scanning electron microscope to obtain the following Figure 1 In the image shown, the cross-section porosity is approximately 0.12%. Example

[0025] Si3N4 powder with an α phase content higher than 70%, AlN, Y2O3, MgO, Li2O, La2O3, and sintering aids in a mass fraction ratio of 80:4:5:5:3:1:1:1 were put into a ball mill for ball milling until the particle size of all particles was less than 0.5 μm, and 0.8 kg of mixed powder was prepared.

[0026] The mixed powder is poured into two hemispherical molds and pressed into spherical bodies.

[0027] The spherical green body is subjected to cold isostatic pressing.

[0028] The spherical blank is debinded.

[0029] The spherical green body is sintered in a nitrogen atmosphere at a sintering temperature of 1750°C, a sintering pressure of 20 atm, and a sintering time of 72 hours to obtain a silicon nitride green body.

[0030] The silicon nitride blank obtained in Example 2 was cut with a diamond wire and scanned with a scanning electron microscope to obtain the following Figure 2 In the image shown, the cross-section porosity is approximately 0.76%.

Claims

1. A high-density silicon nitride bearing ball and a preparation method thereof, characterized in that: The steps are: S1. Put Si3N4 powder with an α-phase content higher than 70%, AlN, Y2O3, MgO, Li2O, La2O3 and sintering aid into a ball mill for ball milling until all particles have a particle size of less than 0.5 μm to prepare a mixed powder; S2, take out the mixed powder and put it into a container, pour an organic solvent in an amount exceeding the mass of the mixed powder into the container, stir evenly, put the container into a vacuum furnace for vacuum treatment, and let the container stand in a vacuum state for more than 12 hours; S3, taking out the container after vacuum standing, stirring evenly, putting it into a distillation device with negative pressure and heating functions, heating the distillation device, slowly distilling the organic solvent out, while maintaining the negative pressure state in the distillation device, and distilling until the mass fraction of the organic solvent accounts for 10%-40%; S4, taking out the wet powder containing the organic solvent in the container, pouring the wet powder into two hemispherical molds, applying pressure to mold into a spherical body; while maintaining the pressure, placing the spherical body in a distillation device for negative pressure heating until the spherical body is dry and then stopping the negative pressure heating; S5, cold isostatic pressing the spherical green body; S6, sintering the spherical blank, the sintering process is carried out in a nitrogen atmosphere, the sintering temperature is 1700° C.-1900° C., the sintering pressure is 4 atm-30 atm, the sintering time is 48h-96h, and the sintered blank is a silicon nitride blank; S7. Machining the silicon nitride blank to prepare bearing balls of required sizes.

2. A high-density silicon nitride bearing ball and a preparation method thereof according to claim 1, characterized in that: In step S1, the mass fraction ratio of Si3N4 powder, AlN, Y2O3, MgO, Li2O, La2O3 and sintering aid is (80-88): (3-7.0): (3-7): (1-5): (1-5): (1-5): (1-3).

3. A high-density silicon nitride bearing ball and a preparation method thereof according to claim 1, characterized in that: The organic solvent in step S2 is one or a combination of two or three of toluene-based solution, acetone and butanone.

4. A high-density silicon nitride bearing ball and a preparation method thereof according to claim 1, characterized in that: In step S2, the distillation temperature is 60° C.-200° C., and the distillation time is greater than 12 hours per kilogram of organic solvent.

5. The high-density silicon nitride bearing ball and the preparation method thereof according to claim 1, characterized in that: In step S4, the edge area of ​​the hemispherical mold has a toothed structure.

6. The high-density silicon nitride bearing ball and the preparation method thereof according to claim 1, characterized in that: In step S4, the negative pressure heating temperature is 120° C.-300° C., and the distillation time is 0.5 h-2 h.

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