Bolts for joining of hot structure

For joining of hot structures like furnace with temperature higherthan 1400°C you need ceramic materials to withstand the hightemperature. But bolts on the basis of conventional ceramics are notsuitable due to their brittle failure mechanism and notch sensitivity.With notch insensitive Ceramic Matrix Composites (CMC) materials,joining with bolts is possible.

With fibre reinforced ceramics a material becomes available, whichcompared to conventional ceramics shows excellent fracture toughnessand extreme thermal shock resistance. Carbon- or SiC-fibres, embeddedin SiC matrix, are bridging each starting crack and, by their highstrength and elongation, lead to high values for crack resistance andfracture toughness.

These properties and the high level of notch insensitivity allow theuse of these materials in bolts and screws. The tensile strength isaround 300 MPa, the elongation at fracture at 0.7% - 0.9%.Standard andspecial threads are possible for screws and nuts. Under vacuum or inertgas atmosphere temperatures up to 2200°C, the temperature ofSiC-decomposition, can be reached.

Source: sirris.beAdded: 12 November 2007