Method for preparing large scale ceramic ball

A ceramic ball and large-size technology, which is applied in the field of preparation of large-size silicon nitride ceramic balls, can solve problems such as difficult sintering, excessive grain growth, and difficulty in controlling the uniformity of sintered materials to achieve high strength and structural uniformity Effect

Inactive Publication Date: 2008-02-20
SHANGHAI RES INST OF MATERIAL
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  • Abstract
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AI Technical Summary

Problems solved by technology

[0005] However, there are certain difficulties in the preparation technology of large-sized ceramic balls. The special difficulty lies in: it is difficult to control the uniformity of the green body during molding; deformation or cracking easily occurs during the process; it is difficult to densify during sintering, and pores and The control of defects is difficult, and the uniformity of si

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example Embodiment

[0019] Example 1

[0020] 1. Take Si 3 N 4 Powder as the main raw material, with 2 O 3 , Al 2 O 3 , La 2 O 3 , CeO 2 ) Is an additive, Si 3 N 4 The mass ratio of powder and additive is 100:15-5; among them, Si in Si3N4 powder 3 N 4 Content ≥95%, median particle size D 50 ≤1μm, oxygen content ≤2%; additive purity ≥99.9%, median particle size D 50 ≤1μm;

[0021] 2. Mix the silicon nitride powder and additives in step 1 by ball milling and wet mixing. The mixing time is ≥18h. After the mixture is dried, it is dry-pressed and molded. The molding pressure is 2-10MPa. After vacuuming and plastic sealing, cold isostatic pressure treatment is carried out, and the cold isostatic pressure is 100-450MPa;

[0022] 3. Hot isostatic pressing sintering the green body after cold isostatic pressing in step 2. The hot isostatic pressing sintering method adopts the glass sheathing process; the sheath glass adopts borosilicate glass, B 2 O 3 The content is 10-18%, SiO 2 The content is 70-85%, Al 2 O ...

Example Embodiment

[0025] Example 2

[0026] Will add (5wt% Y 2 O 3 +2wt%Al 2 O 3 ) The silicon nitride powder of the sintering aid is uniformly mixed, and after drying is completed, it is dry-pressed into a ceramic ball body with a diameter of 35mm under a pressure of 2MPa, and then cold isostatically pressed at 200MPa for further compaction, and the molded body is embedded The composition is (SiO 2 77wt%, B 2 O 3 15wt%, Al 2 O 3 3wt%, Na 2 O 4wt%, K 2 O 0.6wt%, CaO 0.4wt%) glass frit, heat isostatic pressure sintering at 130MPa, 1750°C, holding time 1.5 hours, nitrogen or argon atmosphere, and cooling after sintering.

[0027] The silicon nitride ceramic ball prepared by the above process has no defects such as pores and cracks on the surface, and has a uniform microstructure with a microhardness of 1550kg / mm 2 ,Indentation fracture toughness 5.4MPa·m 1 / 2 .

Example Embodiment

[0028] Example 3

[0029] Will add (6wt% Y 2 O 3 +4wt%La 2 O 3 +3wt% CeO 2 ) The silicon nitride powder of the sintering aid is evenly mixed. After drying, it is dry-pressed into a ceramic ball body with a diameter of 55 mm under a pressure of 2 MPa, and cold isostatic pressing at 200 MPa is further compacted. The formed body is packed into the composition (SiO 2 82wt%, B 2 O 3 10wt%, Al 2 O 3 2.7wt%, Na 2 O 4.3wt%, K 2 O 0.7wt%, CaO 0.3wt%) glass frit, heat isostatic pressure sintering at 150MPa, 1730°C, holding time of 2 hours, nitrogen or argon atmosphere, and control cooling after sintering.

[0030] The silicon nitride ceramic ball prepared by the above process has no defects such as pores and cracks on the surface, uniform microstructure, and microhardness of 1500kg / mm 2 ,Indentation fracture toughness 6.3MPa·m 1 / 2 .

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Abstract

The invention relates to a preparation method of a large size ceramic ball, comprising the steps of material mixing, moulding and sintering. The method takes silicon nitride powder and additive as raw materials, of which the weight ratio is 100:15-5; certain amount of raw materials are weighted, evenly mixed by a ball milling method, dry pressed and then treated by cold isostatic pressure to get rough-body; the rough-body is hot isostatic pressure sintered under the protection of nitrogen and argon by adopting glass canning process; after a period of insulation and sintering, the temperature is reduced and the finished products are obtained. Compared with the prior art, the silicon nitride ceramic ball prepared by the invention has no stomata and gape on the surface, has even micro structure, 1500kg/mm2 of microhardness, above 5.4MPa.m1/2 of indentation and fracture toughness, and the invention can be widely applied to fields such as bearing ball, etc.

Description

technical field [0001] The invention relates to the field of preparation of engineering ceramics, in particular to a method for preparing large-size silicon nitride ceramic balls. Background technique [0002] Silicon nitride material has a series of excellent properties such as wear resistance, corrosion resistance, high temperature resistance, electrical insulation, magnetic insulation, high strength, high rigidity, low specific gravity, and low expansion. It is the preferred material for ceramic balls at present. Silicon nitride ceramic balls can be used as ceramic bearing balls, valve balls, measuring balls, etc., and are widely used in aviation, aerospace, electronics, machinery and other fields. [0003] At present, the preparation of silicon nitride ceramic balls mainly focuses on the production of products with a diameter of less than 20mm, and there is a certain difficulty in the preparation of large-size silicon nitride ceramic balls. [0004] Large-size ceramic b...

Claims

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Application Information

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IPC IPC(8): C04B35/584C04B35/622
Inventor 张培志何万保
Owner SHANGHAI RES INST OF MATERIAL
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