Microstructures and mechanical properties of 25Cr duplex stainless steel

C Meena, V Uthaisangsuk

Abstract


Recently, the demand of duplex stainless steels has been continuously increased in different types of application, especially, tubing of heat exchanger, thermal generator, vessels and pumps. The duplex steel grades exhibit high strength property and excellent corrosion resistance. However, after welding and heat treatment their toughness and corrosion resistance could be significantly decreased due to the occurrences of various detrimental intermetallic phases like sigma phase. In this work, effect of heat treatment on microstructure and mechanical behavior of super duplex stainless steel grade SAF 2507 were investigated. Firstly, samples of the examined steel were heat-treated at the temperature of 850°C for different holding times. Then, microstructure evolutions of heat-treated samples were characterized by an optical and scanning electron microscopy. The emerged phases were identified, their phase fractions were determined and the Vickers hardness tests were performed for the different phase constituents. In addition, tensile tests and Charpy impact tests of heat-treated specimens were carried out. The steel samples subjected to the holding time of 90 min exhibited significantly deteriorated toughness property. This was caused by large amount of occurred brittle intermetallic precipitates.

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Printed ISSN: 0857-6149

Online ISSN: 2630-0508