Reaction bonded silicon carbide

Reaction sintering silicon carbide ceramic sintering

Manufacturers are looking for more energy-efficient engines and want to replace critical metals. These motives initiated the development of different ceramic materials and processes. Reaction bonded silicon carbide is a result of these investigations.Reaction bonded silicon carbide is a type of silicon carbide that is produced by a chemical reaction between graphite or porous carbon with molten silicon. The material has some traces of silicon that’s why it is also referred to as siliconized silicon carbide.Its excellent wear and chemical resistance qualities make it ideal for extreme environments. Due to its high hardness and good temperature resistance, it is suitable for different types of applications such as wear parts and thrust bearings.

In this guide, we will cover different aspects of reaction bonded silicon carbides such as their key properties and applications. Further, we will cover different types of reaction bonded silicon carbide. Let’s get started…

Processing of Reaction Bonded Silicon Carbide

Reaction bonded silicon carbide is produced by the mixtures of silicon carbide and carbon with liquid silicon. Silicon carbide is obtained after the reaction between silicon and carbon. The remaining pores after the reaction are filled by the silicon. As a result, you will get a dens SiC-Si composite.
The particle size distribution and the ratio between SIC and carbon vary widely among different manufacturers. Therefore, the material is manufactured with an extensive range of properties and compositions. For instance, at one extreme, you can infiltrate carbon fiber or cloth with liquid silicon. However, on the other extreme, you can make impervious silicon with a small amount of carbon.
In addition to this, many manufacturers produced reaction bonded silicon carbide with formulations that contain an organic plasticizer, silicon carbide particles, and carbon. The mixture is formed by pressing, extruding, or injection molding. Plus, manufacturers have good control of components tolerance because the reaction process offers less than 1% dimensional change.

What Are Different Types of Reaction Bonded Silicon Carbide?

There are two primary types of reaction bonded silicon carbide as follows:

Monolithic or Solid Reaction Bonded Silicon Carbide

In this type of silicon carbide, the silicon infiltrates the integral absorbency of the matrix. As a result, you will get an impervious composition. The free silicon also creates a surface texture that will reduce the friction for prolonged component life.Monolithic reaction bonded silicon carbide is a good candidate for tribological components. It is used in fluids that are somewhat caustic or acidic including abrasive, fuels, light hydrocarbons, etc. It offers the highest PV capability when mated with different mechanical carbon materials.

Reaction Bonded Silicon Carbide with Graphite (CMC)

It is an impervious material that has a unique surface texture. Its beautiful texture is due to the existence of graphite and silicon. This type of silicon carbide has also excellent thermal conductivity and a lower degree of thermal expansion. These abilities make it suitable for applications susceptible to different forces of friction, impact, erosion, abrasion, high temperatures, and thermal shock.

Different Properties of Silicon Carbide

The material grade defines the properties of different components of silicon carbide. For instance, the material shows excellent bend strength at room temperature in the case of fully dense SIC-SI composite. And, it maintains this property to the melting point of silicon which is 1410o C. Its Young modulus ranges from 350 to 400 GPa.
Below are some key properties of Silicon Carbide:Silicon Carbide has an excellent ability to resist a wide range of acids and alkalis.It has good resistance against wear and oxidation.The material has a good ability to resist abrasion.Due to its high thermal conductivity and low thermal expansion coefficient, it has excellent thermal shock resistance.It maintains its strength at very high temperatures.Silicon Carbide has good dimensional control of complex shapes.

Different Applications of Reaction Bonded Silicon Carbide

Wear Parts And Thrust Bearings

The material comes with excellent wear and corrosion resistance, high hardness, and high-temperature strength. These abilities make it ideal for different wear components such as plates, screws, and impellers. Further, you can also use it in thrust bearings that will be very helpful to carry extremely high loads in very contaminated liquids.Due to its key properties, manufacturers can produce compact bearings that can operate in the temperature range from -200o C to 400o C.

Kiln Furniture and Support Components

The oxidation resistance, thermal shock resistance, and high-temperature resistance properties allow companies to manufacture low-mass kiln supports. Different kiln products include posts, burner nozzles, thin-walled beams, setters, and rolls.These products help in energy savings and offer the ability of faster product throughput by lowering the thermal mass of kiln cars. However, RBSC based kiln would be almost four times more expensive as compared to a cordierite.

Precision Components

You will notice a negligibly small volume change after reacting with liquid silicon. This property gives you excellent dimensional control of complex shapes. For instance, you can manufacture laser mirror blanks, optical benches, and wafer handling devices. These components are stiff and lightweight and have excellent thermal stability.

Mechanical Seals and Vanes

RBSC is widely used in pump vanes and mechanical seals due to its high abrasion resistance. The material properties depend on the free graphite level in the product. Reaction bonded silicon carbide is used as a seal nose material that works perfectly in hostile operating environments.

Wrapping Up

Reaction bonded silicon carbide is a material that has about 7 to 15% silicon metal, a little amount of unreacted carbon, and Silicon carbide. These materials are produced using a variety of processes depending on the need of the end product. For example, if you want to manufacture wear parts, the manufacturing processes of SiC-Si will be different than the process you used for producing precision components.

Reaction bonded silicon carbide is ideal for wear applications like flow control chokes, pipeliners, and larger wear components. This is an economical and reliable material for plenty of applications due to its excellent feature set.