Effects of inclusions on the precipitation of chi phases and intergranular corrosion resistance of hyper duplex stainless steel

During the initial stage of aging heat treatment at 850 degrees C, inclusions such as (Cr, Mn, Al) oxides and (Cr, Mn, Al, Fe) oxides of a hyper duplex stainless steel act as preferential precipitation sites for the chi phase like ferrite/austenite phase boundaries and ferrite/ferrite grain boundaries. The chi phase is precipitated around the inclusions due to the blocking and piling up the alloying elements such as Mo and W around the inclusions. The precipitation of Mo and W enriched chi phase around the inclusions decreases the intergranular corrosion resistance due to the formation of Mo and W depleted zones. (C) 2014 Elsevier Ltd. All rights reserved.