1.4835 | X9CrNiSiNCe21-11-2 Radiant tube

Radiant tubes are used in heat treatment furnace to distribute heat evenly. They are heated by a burner and then radiate the heat into the furnace. This indirect heating enables precise temperature control and a contamination-free furnace atmosphere (no direct flames or combustion products).
This radiant tube was exposed to constant temperature changes (up to approx. 800 °C) for ~7 years. The microstructure consists of austenite (twins) and carbides (mainly chromium and nickel carbides) partially arranged in a network on the grain boundaries. Slight segregation lines are recognisable in the longitudinal direction.