REACTION BONDED SILICON CARBIDE R004
A method used to manufacturing silicon carbide mechanical seal faces.
These reaction bonded silicon carbide materials are sensitive to caustic and other high pH liquids.
- Reaction bonded silicon carbide is produced by adding molten silicon to a mixture of silicon carbide and carbon. A reaction between the silicon and carbon bonds the structure while the excess silicon metal fills the majority of the pits left in the resultant material. There is almost no shrinkage during the process.
- The silicon content is about 8% to 15%. High pH chemicals such as caustic can attack this grade of silicon carbide.
- As of this writing carbon-graphite vs. reaction bonded silicon carbide has been demonstrated to have the best wear characteristics of all the possible face combinations.
- Reaction bonded silicon carbide is difficult to insert into a metal holder so it is usually supplied in a solid rather than a composite configuration.
There are many manufacturers of reaction bonded silicon carbide. The following chart shows some of them.
- ESK, Shunk and Hoechst of West Germany are also manufacturers of reaction bonded silicon carbide.
- Reaction bonded silicon carbide has proven to be more chip resistant than the sintered version
- Avoid the following chemicals when using reaction bonded silicon carbide :
- Sodium Hydroxide
- Potassium Hydroxide
- Nitric Acid *
- Green Sulfate Liquor *
- Calcium Hydroxide *
- Hydrofluoric Acid
- Caustics and strong acids
- Most high pH chemicals
* Results vary with temperature and concentration.
The above chemicals can leach the silicon out of the silicon carbide leaving a weakened, hard matrix that can act like a grinding wheel against the softer carbon face.