Sintering and application of silicon carbide ceramics

---

Silicon carbide ceramic materials have the advantages of wear resistance, corrosion resistance, high hardness, low density and high high temperature strength, so they are rapidly popularized and developed in various fields in recent years. In aerospace, nuclear industry, petroleum industry, chemical industry, textile industry, food industry and other special environments, such as high temperature, high speed, corrosion resistance, vacuum, electrical insulation, non-magnetic, dry friction and so on, the incomparable substitution of this new ceramic material is gradually recognized by people.

In addition to the above advantages, the content of free silicon and free carbon in atmospheric pressure sintered silicon carbide ceramics is very small. For example, in the fine chemical industry, in the process of ultra pure fluid transportation, high cleanliness is required. Atmospheric pressure sintered silicon carbide ceramic materials can provide a very reliable transportation environment and protect the transportation environment. With the enhancement of people’s awareness of environmental protection, atmospheric pressure sintered silicon carbide ceramic materials will eventually replace reaction sintered silicon carbide products in the chemical industry.

At present, atmospheric pressure sintered silicon carbide ceramic materials are mainly used in the following aspects:

1、 Bearing assembly of sealed magnetic drive pump
With the rapid development of fine chemical products, especially the further implementation of the international standard ISO14000 in the fine chemical industry, it puts forward higher requirements for the elimination of running, emitting, dripping and leaking, and the environmental protection of the chemical industry, especially for the transportation of corrosive liquid. The pursuit of zero leakage has become the main goal of environmental protection in the chemical industry.
The sealed magnetic drive pump uses non-contact magnetic drive to generate torque and drive the pump shafting components to work. Its main features are as follows: large space is reduced, and the overall volume of the pump is reduced by 20% – 30%; Using non-contact transmission, the bearing and shafting components are all placed inside the pump body, which is fully closed, so as to achieve no leakage work. In this condition, the bearing life determines the overall life of the pump.
The seal ring made of normal pressure sintered silicon carbide ceramic material is used to replace the general mechanical seal, packing seal and other dynamic seals, so that the leakage is smaller, the reliability is higher and the service life is longer. For magnetic pump, maintenance free for a long time is usually required, and the time is about 5-8 years, which puts forward extremely strict requirements for the material selection of magnetic pump shafting components. For example, the pump shaft, thrust plate and shaft sleeve in the pump must be wear-resistant, corrosion-resistant and zero leakage after assembly: at present, atmospheric pressure sintered silicon carbide ceramics has become the most suitable material of choice.

2、 Mechanical seal ring
Atmospheric pressure sintered silicon carbide ceramics have good chemical corrosion resistance, high strength, high hardness, good wear resistance, low friction coefficient, oxidation resistance, low high temperature creep and good thermal stability, so they are ideal materials for manufacturing sealing rings. Due to the compact structure of the material matrix, there is no free silicon; Carbon content is very little, and it is widely used in high purity, ultra clean, fine chemical and other fields. Due to the ultra precision machining of the workpiece surface, the friction coefficient is smaller than that of alumina ceramics and cemented carbide, so it has higher PV value. It is especially suitable for conveying strong acid, strong alkali and corrosive liquid. Atmospheric pressure sintered silicon carbide ceramic products, with high density (310G / cm3-320g / cm3), high hardness (hpa95), can be a variety of mass production of various shapes of complex mechanical seal ring, such as flat ring, single step ring, multistage step ring, etc.

3、 Sandblasting nozzle
As a rising star to replace cemented carbide and alumina ceramic materials, atmospheric pressure sintered silicon carbide ceramic materials have become second only to boron carbide ceramics, and the largest amount of materials used in sandblasting industry. Although the price of alumina ceramic nozzle is low, because of its low hardness and poor wear resistance, it is only used in the occasion where the workload of sandblasting is small. In practice, the service life of SiC ceramics sintered at atmospheric pressure is 4-7 times that of alumina ceramics, and it is also a substitute for cemented carbide with large proportion.

4、 Bulletproof board
Since the invention of ceramic armor by the British chobam, atmospheric pressure sintered silicon carbide ceramics have been widely used in bulletproof armor, such as the protection of vehicles and ships, as well as the protection of civil safes and cash carriers, due to their high hardness, small specific gravity, good ballistic performance, more energy absorption after fragmentation and low price. The ballistic performance of SiC ceramics sintered at atmospheric pressure is better than that of alumina ceramics, and the comprehensive strength is about 70-80% of that of boron carbide ceramics. However, due to its low price, it is especially suitable for the occasions where the amount of SiC ceramics is large and the protective armor cannot be too thick or heavy. The atmospheric pressure sintered silicon carbide ceramic has the characteristics of high strength and good toughness. As a bulletproof armor material, it has very good resistance to multiple attacks, so the overall protection effect is better than that of ordinary silicon carbide ceramic. When it is used in cylindrical ceramic lightweight protective armor, its breaking point can reach more than 65 tons, The protective effect is obviously better than that of cylindrical ceramic armor with ordinary silicon carbide ceramics.

Learn More :
Silicon Carbide Vacuum Pressureless Sintering Furnace
Silicon Carbide Pressureless Sintering Furnace
Silicon Carbide Reaction Sintering Furnace