With ultra-high melting points advanced ceramics are often the only material of choice for high-temperature applications. Dynallox® alumina components have operated in furnace environments at up to 1800°C. Technox® 802 thermocouple sheaths are often used at 2100°C.
One of the main driving forces for the development of advanced ceramics has been their ability to operate effectively at elevated temperatures. The inter-atomic bonding of these materials provides an excellent platform for high-temperature operation, well above the regime of superalloys or other metallics.
The melting points of a selection of advanced ceramics are shown in the table below:
As with metallic materials there is often a reduction in room temperature properties at elevated temperatures so it is wise to discuss your application with our engineers before specifying an individual material.
One should also take into account the oxidation behaviour of non-oxide ceramics (Si3N4 and SiC), as this behaviour limits the temperature of application to +/- 1400ºC.
There are many examples of the use of advanced ceramics in elevated temperature applications, from relatively “low tech” kiln furniture for the electronics industry, to high tech in the form of silicon nitride turbocharger rotors which operate at 150,000 rpm and 800ºC. The following examples provide an insight to the range of high-temperature applications.
Furnace Roof Hangers
Produced from one of the several grades of Dynallox® Alumina manufactured by CoorsTek Crewe, these components operate as load bearing supports for furnace roof insulation. To date many years of successful service has been reported at temperatures of up to 1800ºC.
Technox® 802 zirconia tubes are now used extensively in optical fibre production, both as inspection devices and for thermocouple protection. In these applications the material experiences temperatures in excess of 2000ºC.
Production techniques have been developed to permit the fabrication of thin walled tubes, with both open and closed ends to exacting tolerances.