It is well known that the engine efficiency increases with the increase of operating temperature. According to the calculation, when the working temperature of the engine is increased from 1100 ℃ to 1370 ℃, its thermal efficiency can be increased by 30%. In order to improve the thermal efficiency of the engine, make full use of energy, reduce fuel consumption and reduce air pollution, it is hoped that the working temperature of the engine will be higher than 1200 ℃. silicon carbide ceramic have good high temperature resistance, low thermal expansion coefficient, high thermal conductivity and good thermal shock resistance, and considered as the most promising candidate materials for use at temperatures above 1200 ℃. The USA and Germany respectively used pressureless sintering and reaction bonded SiC to manufacture the stator, rotor, burner and vortex tube of the engine, and achieved good results. In addition, in order to develop new energy sources such as atomic energy and nuclear fusion energy, heat resistant materials which can withstand high temperatures of about 2000 ℃ are needed. At present, this can only rely on the use of silicon carbide ceramic. As we know, mechanical seal is carried out by rotating and sliding the materials of two seal faces. Therefore, as a seal face material, high hardness and wear resistance are required first. The hardness of SiC ceramics is quite high and the friction coefficient is small, so SiC ceramics can obtain sliding characteristics which other materials cannot achieve as mechanical seal end materials. On the other hand, during the rotation of the two end face sealing materials, the friction will generate a certain amount of heat, which will increase the local temperature of the sealing end face. Therefore, the end face materials must be able to withstand a certain temperature. In order to avoid thermal strain and thermal crack of end face seal material during rotary sliding, it is required that the end face material has high thermal conductivity and good thermal shock resistance. silicon carbide ceramic have excellent heat resistance, high temperature strength, large thermal conductivity, small coefficient of thermal expansion, and excellent thermal shock resistance. As mechanical end face sealing materials, SiC ceramics have ideal characteristics. At present, silicon carbide ceramic have been widely used in various mechanical seals, and have made great contributions to the labor saving and energy saving of mechanical equipment. For example, in the slurry with solid particle scouring, reaction bonded SiC, as a static and dynamic anti wear sealing end face material, can ensure the prolongation of the service life of the seals, thus greatly reduce the maintenance cost of the equipment, reducing the production cost, and showing the advantages that other materials can not compare.
