Erosion–corrosion behaviour of lean duplex stainless steels in 3.5% NaCl solution

The interaction between corrosion and erosion has often been a subject of debate among scientists and engineers. The total material degradation when corrosion and erosion interact is often more than the individual components acting separately. Much effort has been directed towards the study of erosion–corrosion behaviour of carbon steels, standard austenitic and duplex stainless steels, highly alloyed austenitic and super duplex stainless steels. However, the subject of erosion–corrosion of lean duplex stainless steels is still rarely reported. This present work studies the erosion–corrosion behaviour of lean duplex stainless steels UNS S32304 and UNS S32101 in an aerated 3.5% NaCl environment. The erosion–corrosion behaviour of these alloys is compared with an austenitic stainless steel, UNS S30403 and a duplex stainless steel, UNS S32205. Sub-surface microstructure modifications induced by work-hardening as a result of the sand impingement were analysed by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). Results show that lean duplex stainless steels, UNS S32101 and UNS S32304, have higher resistance to pure erosion than UNS S30403 and UNS S32205; better erosion–corrosion resistance than UNS S30403 austenitic stainless steel; and equivalent erosion–corrosion resistance to UNS S32205 duplex stainless steel. Also, erosion with 500 mg/l sand at 15 m/s in de-aerated tap water was able to cause subsurface deformation, phase transformation and an increase in hardness on the stainless steels.