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Silicon nitride ceramic ball preparation method employing glass encapsulating heat and other static pressuring processes

A technology of silicon nitride ceramic balls and hot isostatic pressing, which is applied in the field of engineering ceramics preparation, can solve the problems of small improvement of microstructure, irreparable and incomplete elimination of large-sized cracks and pores, and easy operation. , Conducive to production, good repeatability

Inactive Publication Date: 2009-12-30
SHANGHAI RES INST OF MATERIALS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] The post-treatment process of hot isostatic pressing can partially eliminate defects such as small-sized cracks and pores, but it cannot completely eliminate existing defects, and cannot make up for large-sized cracks and pores, and has a great effect on improving the microstructure of materials. Small, for silicon nitride materials, after sintering, the crystal grains cross each other to form a skeleton structure, and it is difficult to change the post-treatment process of hot isostatic pressing. Therefore, although the post-treatment process of hot isostatic pressing has the advantages of simple process and high production capacity Large, low production cost, etc., but it has certain limitations for the production of high-performance silicon nitride ceramics

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] The silicon nitride formulation (95%Si 3 N 4 +3wt%Y 2 o 3 +2wt%Al 2 o 3 ) into a ceramic ball green body of φ5mm, cold isostatic pressing is carried out under a pressure of 200 MPa, and the density of the green body reaches 60% of the theoretical density, and then a layer of colloidal graphite isolation layer is coated on the surface by a solution impregnation method, and the thickness is greater than 0.05 mm, put it into a graphite crucible after fully drying, embed borosilicate cullet around it, then heat up to 1200°C, the glass melts, completely encapsulate silicon nitride balls, pressurize and heat up to 1850°C, 200MPa, heat preservation and pressure Hot isostatic pressing sintering was carried out for 2 hours, and after the sintering was completed, the temperature was lowered under control, and the silicon nitride balls were taken out.

[0025] The φ5mm silicon nitride ball prepared by the above process has a uniform microstructure, no pores, cracks and other ...

Embodiment 2

[0027] The silicon nitride formulation (95% Si 3 N 4 +3wt%Y 2 o 3 +2wt%Al 2 o 3 ) into ceramic balls of φ7mm, the batch size is 2kg, and the pressure is kept at 200MPa for 5 minutes for cold isostatic pressing, and then the green body is coated with a layer of colloidal graphite isolation layer on the surface by solution impregnation method, the thickness is greater than 0.05mm, and fully dried Then put it into a graphite crucible, embed borosilicate broken glass around it, then heat up to 1200°C, the glass melts, completely encapsulate the silicon nitride ball, pressurize and heat up to 1850°C, 200MPa, heat and hold the pressure for 2 hours. Isostatic sintering, after the sintering is completed, the temperature is lowered under control, and the silicon nitride balls are taken out.

[0028] The φ7mm silicon nitride balls prepared in batches by the above process have a uniform microstructure, no pores, cracks and other defects, and a microhardness of 1550kg / mm 2 , indenta...

Embodiment 3

[0030] The silicon nitride formulation (92%Si 3 N 4 +5wt%Y 2 o 3 +3wt%Al 2 o 3 ) into ceramic balls of φ16mm, hold the pressure at 200MPa for 5 minutes for cold isostatic pressing, and then use the solution impregnation method to coat a layer of colloidal graphite isolation layer on the surface, the thickness is greater than 0.1mm, and put it into a graphite crucible after fully drying Borosilicate broken glass is embedded inside and around, and then the temperature is raised to 1200 ° C, the glass is melted, and the silicon nitride ball is completely encapsulated, and the temperature is increased to 1850 ° C, 180 MPa, and the heat preservation and pressure are held for 2 hours for hot isostatic pressing sintering. After the sintering is completed, the silicon nitride ball is taken out by controlling the temperature drop.

[0031] The φ16mm silicon nitride ball prepared by the above process has a uniform microstructure, no pores, cracks and other defects, and a microhardn...

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Abstract

The invention relates a silicon nitride ceramic ball preparation method employing glass encapsulating heat and other static pressuring processes, comprising the following steps: adopting silicon nitride formula material for shaping and cold isostatic pressing to obtain base substrate, coating a layer of graphite isolation layer on the surface of the base substrate by solution dipping process, drying the obtained base substrate, then placing the dry base substrate in a crucible, embedding cullet around the dry base substrate, heating to 1100-1300 DEG C to melt the glass and form complete encapsulating, pressurizing to 100-200Mpa and heating to 1700-1900 DEG C, keeping the temperature for 1-3h to perform hot-isostatic pressing sintering and finally obtaining the product. Compared with the prior art, the method of the invention has the advantages of simple process, good repeatability, quantitative production and the like.

Description

technical field [0001] The invention belongs to the field of preparation of engineering ceramics, and relates to a method for preparing silicon nitride ceramic balls by using a glass-encapsulated hot isostatic pressing process. Background technique [0002] Silicon nitride materials have very important applications in the field of engineering ceramics. In addition to the unique properties of engineering ceramic materials such as wear resistance, corrosion resistance, high temperature resistance, electrical insulation, magnetic insulation, high strength, high stiffness, low specific gravity, and low expansion, etc. In addition to the excellent performance of the series, it also has a similar rolling contact fatigue failure form-flaking with steel balls for bearings, which can avoid sudden damage caused by brittle fracture of other ceramic materials, and has more and more applications in the field of bearing balls. [0003] The excellent comprehensive mechanical properties and...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C04B35/584C04B35/645
Inventor 张培志何万保李莉
Owner SHANGHAI RES INST OF MATERIALS CO LTD
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