Different Aspects on Operating Duplex Stainless Steels at Elevated Temperatures

Abstract The critical question for use of Duplex stainless steels at elevated temperatures is normally the embrittlement caused by spinodal decomposition of the ferrite, historically referred to as the 475°C-embrittlement, since 475°C is the most sensitive temperature for this phenomenon. Through the years the stainless steel industry has gained a lot of knowledge on kinetics and boundary conditions on how to apply duplex at high temperatures. The maximum operating temperature has been described in different standards, however with different temperatures. One question that earlier also has been discussed is whether the maximum operating temperature actually should be a combination of time and temperature as this phenomenon develops with time. In this paper some historical examinations combined with relatively new data from different welded duplex stainless steel materials will be presented. Properties of both base metal and weld will be covered and their relevance to the design and operation of pressure vessels and piping systems at high temperatures will be discussed.