Steel alloys containing more than 20% chromium produce a protective, sustainable surface scale when exposed to high temperatures in oxidising atmospheres up to 1100 degrees C. When nickel and carbon are added to these alloys, a series of heat resisting alloys is produced to perform in an array of high temperature applications.

Increased nickel content progressively stabilises austenite in heat resisting steels, from a duplex structure especially designed for sulphurous environments (R80), through alloys with measured ferrite/austenite ratios (R81,R83), to fully austenitic alloys (R84, R85).

By adjusting nickel, chromium and carbon content and including additions of rare earth elements, niobium and tungsten, castings can be manufactured to withstand high temperature thermal cycling, carburising and high load environments. In more severe applications, a series of grades with substantially increased nickel contents are used (R87,R88). Generally, these super alloys contain additions of one or a combination of rare earths, niobium, tungsten and cobalt (R87Nb, R88Nb,R89). This produces an alloy that is able to absorb considerable amounts of carbon over long periods without significant embrittlement.