SiC Heating Elements

SiC Heating Elements

Advantages to employing silicon carbide heating elements includes corrosion resistance, heat zone resistance, minimal operation-induced deformation, cold end resistance, easy maintenance and a long service life. However, there are some disadvantages, and they include a higher risk of fracture compared to other heating element compositions, increased electrical resistance over time as well as more expensive power control equipment than metallic heating elements. SiC heating elements are widely used for applications such as electric furnaces, kilns and other electric heating devices in industries including powder metallurgy, ceramics, metal processes, glass, semiconductor, scientific research and electronics.

SiC heating elements are formed through either a reaction-bonding process or a recrystallization process. In the reaction bonding process, liquid silicon is used to infiltrate compacts made of mixtures of SiC and carbon. As a result, the silicon then reacts with the carbon in order to form silicon carbide. In the recrystallization process, high-density, high-purity green silicon carbide is formed into a blank and then silicided under extremely high temperatures. Next the silicon carbide is recrystallized, and fine grains of silicon carbide are formed, which act as connection points between large grains, resulting in conductive pathways. As a result of the high heat resistance of silicon carbide, temperatures must be in excess of 3900º F (2150° C) in order for either process to work. SiC heating elements can be used in temperatures ranging from 600° C to 1650° C, and they do not require a protective atmosphere. While there are several external factors that can affect the service life of SiC heating elements, including type of service, furnace atmosphere, maintenance and watt density, SiC heating elements will most likely fail mechanically rather than as a result of aging.