Study on Corrosion Behaviors of Stainless Steels and Refractory Alloys in Pseudo-Critical Zone

The general corrosion behavior of three super alloys and four austenitic stainless steels was investigated in 380℃ /25 MPa deionized water.Morphology and composition of the surface oxide scale after various exposure time were analyzed through FEG-SEM and EDS.For all the tested materials,the weight gain（WG） represents no apparent regularity while the weight loss（WL） follows typical logarithmic law.HR3C showed the least WL while 347 the most,an order of magnitude difference.All the exposed samples developed relatively enact and compact dual oxide layer,with the outer layer rich in O,depleted in Cr,Ni and lack of Mo.Several alloys（316Ti,718,825,800H and HR3C） displays pitting.The pits were rich in Nb andTi,depleted in Cr and Ni,and lack of Mn and Mo,based on the alloy composition.