Silicon carbide ceramics is a very good corrosion resistant material, when silicon carbide is used to manufacture ceramics, there are many sintering methods, and the appropriate sintering method can be selected according to the specific processing environment to improve the sintering efficiency.Silicon carbide ceramics not only have high room temperature strength, corrosion resistance, wear resistance and low friction coefficient, but also have high high temperature strength and creep resistance, the use of temperatures up to 1600℃, which is currently known ceramic materials high temperature oxidation resistance.
Silicon carbide ceramics have been widely used in automotive, mechanization, environmental protection, aerospace technology, information electronics, energy and other fields, has become an irreplaceable structural ceramics with excellent performance in many industrial fields, let us introduce the sintering method of silicon carbide ceramics!
Pressureless sintering
Pressureless sintering is considered to be the most promising method for SiC sintering. According to different sintering mechanisms, pressureless sintering can be divided into solid phase sintering and liquid phase sintering. S. Proehazka was sintered at 2020℃ to a SiC sintered body with a density of more than 98% by simultaneously adding appropriate amounts of B and C(oxygen content less than 2%) to the ultrafine β-SiC powder. ulla et al sintered 0.5μmβ-SiC(particle surface containing small amounts of SiO2) at 1850-1950℃ using Al2O3 and Y2O3 as additives. The relative density of SiC ceramics is greater than 95% of the theoretical density, and the grain size is small and average. It's 1.5 microns.
Hot press sintering
Nadeau pointed out that pure SiC can only be densified at very high temperatures without any sintering additives, so many people implement the hot press sintering process for SiC. There have been many reports on hot press sintering of SiC by adding sintering aid. Alliegro et al. investigated the effect of metal additives such as boron, aluminum, nickel, iron, and chromium on the densification of SiC. The results show that aluminum and iron are the most effective additives to promote hot pressing sintering of SiC. F.f.ange studied the effect of adding different amounts of Al2O3 on the properties of hot-pressing sintered SiC. It is concluded that the densification of hot pressing sintered SiC is related to the dissolution and precipitation mechanism. However, the hot press sintering process can only produce SiC parts with simple shapes, and the number of products produced by the one-time hot press sintering process is very small, which is not conducive to industrial production.
Hot isostatic pressing sintering
In order to overcome the shortcomings of the traditional sintering process, type b and type c were used as additives for the scuba, and hot isostatic pressing sintering technology was adopted. At 1900°C, fine crystalline ceramics with a density greater than 98 were obtained, and the bending strength at room temperature could reach 600 mpa. Although hot isostatic pressing sintering can obtain dense phase products with complex shapes and good mechanical properties, hip sintering must be sealed blank, which is difficult to achieve industrial production.
Reaction sintering
Reactive sintering silicon carbide, also known as self-bonding silicon carbide, refers to the process of porous billet reaction with the gas or liquid phase, improve the quality of the billet, reduce the porosity, and sintering the finished product with a certain strength and dimensional accuracy. The α-SiC powder is mixed with graphite in a certain proportion and heated to about 1650 ° C to form a square billet. At the same time, it penetrates through the gas phase Si or penetrates into the billet, reacts with the graphite to form β-SiC, which binds to the existing α-SiC particles. When Si is fully infiltrated, the reactive sintered body with complete density and no shrinkage can be obtained. Compared with other sintering processes, the size change of reactive sintering in the densification process is small, which can produce products with accurate size, but the presence of a large amount of SiC in the sintered body makes the high temperature performance of reactive sintered SiC ceramics worse.
Non-pressure sintered SiC ceramics, hot isostatic pressing sintered SiC ceramics and reaction sintered SiC ceramics have different properties. For example, in terms of sintering density and bending strength, hot pressing sintering and hot isostatic pressing sintering of SiC ceramics are relatively high, and reactive sintering SiC is relatively low. On the other hand, the mechanical properties of SiC ceramics vary with the change of sintering additives. The non-pressure sintering, hot press sintering and reaction sintering of SiC ceramics have good acid and alkali resistance, but the reaction sintered SiC ceramics have poor resistance to HF and other superacid corrosion. When the temperature is below 900℃, the bending strength of almost all SiC ceramics is significantly higher than that of high temperature sintered ceramics, and the bending strength of reactive sintered SiC ceramics decreases sharply when it exceeds 1400℃. For non-pressure sintering and hot isostatic pressing sintered SiC ceramics, the high temperature performance is mainly affected by the type of additives.
Each of the four sintering methods for SiC ceramics has its own advantages. However, in today's rapid development of science and technology, there is an urgent need to improve the performance of SiC ceramics, constantly improve the manufacturing process, reduce production costs, and achieve low temperature sintering of SiC ceramics. In order to reduce energy consumption, reduce production costs, and promote the industrialization of SiC ceramic products.
The above is a detailed introduction to the advantages and disadvantages of several sintering methods of silicon carbide ceramics. I hope you can choose your own products according to your actual needs! Pay attention to Huaxin Industry, pay attention to the silicon carbide ceramic experts around you!