Carbides are binary compounds of elements with carbon, classified in saline carbides, covalent carbides and metal carbides. Covalent silicon carbide (SiC) and metallic tungsten carbide (WC) are the types used primarily as materials for seal faces and stationary seats. For reasons of cost and function, shrink-fitted and – in the case of WC – brazed designs also find application in addition to solid SiC and WC seal faces and stationary seats.