Heat-resistant materials must contain chromium to resist oxidation. Cobalt, aluminum, silicon and rare earth elements contribute to the formation of surface oxide layers. Nickel provides strength, stability, toughness, and resistance to carburization. Tungsten and molybdenum increase the high temperature strength.
When the temperature is higher than 600 degrees Celsius, the following materials are usually considered:
1. Ferritic steel containing 17%-27%Cr and a small amount of Mo.
2. Austenitic high-temperature, high-strength steel (Cr-Ni-Mo steel containing more than 8% Ni), such as grades 321 (06Cr18Ni11Ti), 347 (06Cr18Ni11Nb), 316 (06Cr17Ni12Mo) and 310 (20Cr25Ni20).