Fixtures and Insulators for High-Temperature Furnaces

High-Temperature Furnace Components

A typical design of a high temperature furnaces operating at temperatures significantly higher than 1600°C incorporates heating elements manufactured from graphite, tungsten or molybdenum disilicide. There is a need to electrically insulate these heating elements from the furnace environment using high temperature ceramics.

While oxide ceramic insulators are commonly used in low temperature furnaces, they are not as well suited for high-temperature furnaces. They become highly stressed at high temperatures, especially under shorter production cycles with faster heating and cooling rates. This leads to premature component failures and increased furnace downtime

For thermal processes at extremely high temperatures and vacuum or in inert conditions, Boron Nitride insulators and components present the only viable solution. Saint-Gobain's Combat™ grade AX05 is the material of choice in these applications due to its high purity, and therefore operating temperature up to 2000°C in inert atmosphere.

Furthermore, easy machinability of Boron Nitride makes it easier to make precision-machined components such as sleeves, tubes, washers, insulators, spools, flanges and other parts subjected to high thermal stresses – to suit specific requirements of an application.

Sintering Media for Ceramic Manufacturing

The exceptional properties of boron nitride such as high operating temperature and thermal shock resistance are exploited in variety of sintering applications, both in powder form, as a bedding-in powder, and in sintered form using plates and crucibles. Use of Boron Nitride in these applications ensures an even heat transfer to prevent the differential thermal expansions that can lead to the distortion of the finished sintered part.

One growing area for ceramic manufacturing is the sintering of green sheets of AlN, commonly used as substrate material in the manufacturing of LED, HBLEDs and power devices. Key properties needed for sintering media in this application are high chemical stability at elevated temperatures, high purity, and good structural properties to avoid warping from the weight.  Typical materials used for sintering applications such as Al₂O₃ and graphite are not a good fit for the growing AlN substrate market due to low operating temperature and possibility of contamination respectively.

Saint-Gobain grade AX05 offers the right combination of mechanical strength, high purity and low coefficient of friction of AX05. Use of AX05 sintering plates offer multiple runs without warping of the plates, easy cleanup between runs, long service life, reduced frequency of replacement, and protection against contact reaction between sintered parts and supporting media.