Basic Properties Of Ceramic Materials

It is not possible to use common ceramic materials for ceramic seal ring. Engineering ceramics (i.e. structural ceramics) should be used, the main types of which are Al2O3, ZrO2, SiC and so on. These engineering ceramics are mostly ionic bonds and covalent bonds, which have high melting point, good corrosion resistance and antioxidation, high hardness and high temperature strength compared with metal and polymer. In traditional sealing elements, the rigid seal of metal materials and the "Elastoplastic" seal of non metal materials have the corrosion resistance and poor temperature resistance, which makes the life of the sealing element low. As a sealing element, engineering ceramics have been used more and more widely because of its high temperature resistance, high hardness and good chemical stability. As far as the current situation is concerned, engineering ceramic materials such as hydride porcelain, carbide porcelain and so on as mechanism seal friction pair and inlaid porcelain ring have been widely used, but they are only used as monomers in some products. As a mutual sealing element, it is relatively rare. With the development and research of engineering ceramics, its toughening and strengthening technology has been improved. Its good comprehensive mechanical properties provide a broad prospect for the application of engineering ceramic materials, and table 1 is the performance at normal temperature of commonly used engineering ceramics.

Table 1 Mechanical Properties of several common engineering ceramics

Material	Density (g/ cm3)	Hardness HRA	BendingStrength (MPa)	pressure resistance (MPa)	FractureToughness (MPa·m1/ 2)	MaximumUse Temperature ( ℃)
Al2O3 (98 %)	3172	88	350	2068	8106	1750
ZrO2	5165	84	735	2100	7113	2100
SiC	311	93	550	3138	416	1650

From table 1, it can be seen that several ceramic seals have good mechanical properties, not only bear certain pressure, but also bear a certain impact force for the sealing element, and can choose material with better toughness, such as AlO porcelain, and it is cheap, easy to take material, convenient to manufacture, suitable for new type of sealing element.