Comparative Behaviour of Specialty Austenitic Stainless Steels in High Temperature Environments

Two different alloying strategies may be utilised to improve the high temperature performance of austenitic stainless steels: increasing the chromium content, sometimes in combination with a higher nickel level; and alloying with silicon, nitrogen and rare earth metals. The relative merits of the two approaches are explored by comparing the performance of commercial alloys in oxidation tests in air–water vapour, corrosion tests in an oxidising-sulphidising atmosphere and with applied deposits, and creep and fatigue testing. Significant increases in high temperature performance are achieved by selecting specialty heat-resisting austenitic stainless steels, and it will be shown that the choice of grade should be governed by the dominant operative degradation mechanisms.