Let's talk about the advantages and disadvantages of pressureless sintering and hot pressing sintering.

Sintering is a crucial step in the preparation of B4C ceramics, and the main factors affecting the sintering of B4C ceramics include sintering method, particle size and activity of powder raw materials, type and dosage of additives, sintering temperature and insulation time, etc. At present, the sintering methods for boron carbide ceramic powder mainly include pressureless sintering, hot pressing sintering, hot isostatic pressing sintering, discharge plasma sintering, etc.Now let's talk about the advantages and disadvantages of pressureless sintering and hot pressing sintering.

Pressureless sintering

The densification of pure B4C by pressureless sintering is very difficult, and pore defects and density are key factors affecting the performance indicators of boron carbide ceramics. The sintering temperature and powder particle size are important indicators affecting the density of boron carbide ceramics. The influence of raw material powder on the sintering performance of boron carbide ceramics is crucial. The finer the powder and the faster the heating rate, the more conducive it is to improving the density of ceramics. The smaller the particle size of the powder, the larger the specific surface area, and the greater the driving force for sintering; The increase in particle surface area and sintering temperature can promote densification sintering, resulting in higher density (56% to 71%). Rapid heating helps to achieve high density of good microstructure, as compaction can be heated to a certain temperature and densification occurs before the microstructure coarsens. Research has shown that the main condition for densification of pure boron carbide by pressureless sintering is the use of ultra-fine powder with a low oxygen content of ≤ 3 μ m and a temperature range of 2250~2350 ℃.

The pressureless sintering of boron carbide products has a simple process, low processing cost, and does not require too many sintering conditions. It is suitable for producing products with complex shapes and is suitable for large-scale industrial production. It is a commonly used sintering technology for preparing ceramics. However, due to the high sintering temperature, the grains are prone to abnormal growth, making it difficult to control the sintering process and resulting in unstable product performance.

Hot press sintering

The hot pressing sintering preparation process is to apply pressure at higher temperatures and improve the plasticity of the powder, which has advantages such as excellent microstructure, high product density, low deformation resistance, and low forming pressure. Therefore, in order to effectively reduce the sintering temperature of boron carbide, the preparation process of hot pressing sintering can be adopted.

Compared to pure hot pressing, the effective combination of hot pressing sintering and liquid-phase sintering can greatly reduce the sintering temperature and improve the density. In general, the basic conditions required for hot pressing sintering are: inert or vacuum atmosphere, pressure usually between 20-40MPa, temperature controlled between 1900-2200 ℃, and maintained at this temperature for 0.5-2.0 hours. The characteristics of boron carbide hot press sintering preparation process are complex process flow, high equipment requirements, high processing costs, and low production efficiency. Moreover, it cannot prepare products with complex shapes, and can only produce products with simple shapes.