Effect of Mo substitution by W on impact property of heat affected zone in duplex stainless steels

Abstract

The duplex stainless steels are characterized by two phase structures composed of a mixture of austenite and ferrite phases. They offer high toughness, good weldability, satisfactory corrosion protection, excellent stress corrosion cracking resistance and high strength. Because of these characteristics, these steels have been widely used in various applications such as oil, gas, and chemical industries. Duplex stainless steels generally have suffered embrittlement when exposed at elevated temperature, i.e. above 300 C. To avoid this embrittlement, conventional duplex stainless steels are subject to solution treatment followed by water quenching in the final stage of production or fabrication, which limits the size of products. Kim et al. have recently reported that embrittlement can be greatly reduced by the partial or full replacement of Mo by W in 22Cr-base duplex stainless steels. For the processing of duplex stainless steel, fusion welding is a major fabrication method for corrosion resistant applications. Therefore the welding behavior of these materials has to be fully defined. The purpose of this study is to investigate the effect of Mo substitution by W on the impact property of simulated heat affected zones in 22Cr duplex stainless steels. Structural transformation associated with Mo substitution by W in HAZ hasmore » been also investigated on W-containing alloys and conventional 3% Mo duplex stainless steel.« less