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Launch of oil and gas project

Connect, no. 110, January/February 2001, p.6

Intermetallic phase in superduplex stainless steel
Intermetallic phase in superduplex stainless steel

Following discussions between TWI and North Sea oil and gas operators a new Group Sponsored Project has begun to assess the significance of intermetallic and nitride precipitates in duplex and superduplex stainless steels.

The use of duplex and superduplex stainless steel in the offshore oil and gas industry has become widespread owing to their high strength and resistance to pitting corrosion and stress corrosion cracking in chloride media. Microstructural control is essential to obtain reproducibly good properties. Intermetallic phase precipitates such as sigma phase or chi phase have, for some time, been widely regarded as detrimental, most notably in terms of toughness and pitting corrosion resistance, and their presence has often been regarded as unacceptable.

The aim of the project is to summarise the existing knowledge of the relationships between extent of third phase precipitation in duplex and superduplex stainless steels and in-service properties with relevance to the offshore oil and gas industry. As well, a recommended practice will be developed for quantitative metallography of these materials containing third phase precipitates.

This project has already aroused considerable interest and has five major oil and gas sponsors. If you would like to join the sponsor group or wish further information, please contact the Project Leader, Andrew Leonard. E-mail:

For more information please email: