Sintering of silicon carbide industrial ceramics - Hot isostatic pressing sintering

The ceramic factory has introduced you to the pressureless sintering technology and static pressure sintering technology of silicon carbide industrial ceramics. Next, we will continue to introduce the third sintering method of silicon carbide ceramics - hot isostatic pressing sintering.

Hot isostatic pressing sintering:

In recent years, in order to further improve the mechanical properties of SiC industrial ceramics, researchers have conducted research on the hot isostatic pressing process of SiC industrial ceramics. Researchers used B and C as additives and used the hot isostatic pressing sintering process to obtain high-density SiC sintered bodies at 1900 ℃. Furthermore, through this process, dense sintering of SiC ceramics without additives was successfully achieved at 2000 ℃ and 138MPa pressure. This high-density silicon carbide industrial ceramic can be used for a series of ceramic processing, ceramic rod processing, ceramic tube processing, and so on.

Research shows that when the particle size of SiC powder is less than 0.6 μ At m, even without any additives, it can be densified by hot isostatic pressing sintering at 1950 ℃. If SiC ultrafine powder with a specific surface area of 24m2/g is selected and hot isostatic pressing sintering process is used, high-density additive free SiC ceramics can be obtained at 1850 ℃.

In addition, Al2O3 is an effective additive for hot isostatic pressing sintered SiC ceramics. The addition of C has no effect on the densification of SiC ceramics during hot isostatic pressing sintering, and excessive C can even inhibit the sintering of SiC ceramics.

In order to overcome the shortcomings of traditional sintering processes, Duna used B and C as additives and adopted the hot isostatic pressing sintering process to obtain fine-grained SiC ceramics with a density greater than 98% and a room temperature bending strength of about 600MPa at 1900 ℃. Although hot isostatic pressing sintering can obtain dense SiC products with complex shapes and good mechanical properties, HIP sintering requires encapsulation of the blank, making it difficult to achieve industrial production

Silicon carbide ceramic ring

The use of hot pressing sintering process can obtain dense ceramic sintered bodies at lower temperatures than pressureless sintering, and the sintering time is much shorter. However, hot pressing sintering adopts unidirectional pressure, so the shape and size of the product are limited by the mold, usually cylindrical or circular. In addition, unidirectional pressure also causes uneven pressure distribution in the billet during hot pressing sintering, especially for non equiaxed crystal samples. After hot pressing, the severe orientation of flake or columnar grains can easily cause anisotropy in the microstructure and mechanical properties of the ceramic sintered body. In order to overcome these defects in the pressureless sintering and hot pressing sintering processes, people urgently hope to develop a new sintering process.

Hot Isostatic Pressing Sintering (HIP), also known as High Temperature Isostatic Pressing Sintering, is a process in which materials (powders, billets, or sintered bodies) undergo isotropic pressure during the heating process, promoting material densification through the combined action of high temperature and high pressure. This process was first developed by the Bfitelle Columbus laboratory in the United States in 1955. It was initially mainly applied in the field of powder metallurgy, and with the continuous increase of temperature and pressure that the equipment can reach, it was successfully applied to high-temperature sintering in the field of industrial ceramics.

The characteristics of hot isostatic pressing sintering technology: materials with uniform microstructure, fine grains, and complete density can be prepared at lower sintering temperatures; Complex shaped products can be prepared, especially when preparing nanomaterials with low requirements for powders, and even powders with severe agglomeration can be used for the preparation of nanoceramics.

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