Investigation of oxide layer development of X6CrNiNb18-10 stainless steel exposed to high temperature water

Abstract

The oxide layer development of X6CrNiNb18-10 (AISI 347) over exposure time in high temperature water has been investigated. While a parabolic development of Cr in the protective primary layer and Fe in the secondary layer can be observed, dimensions of the Ni layer remains constant. Ni requires the presence of a pronounced Fe-rich secondary layer before being able to reside on the outer secondary layer. With rising immersion time, the Ni element fraction surpasses the Cr element fraction in the secondary layer. The oxide growth of the secondary layer could be observed. After 480 h, almost the entire surface is covered by the outer oxide layer. In the metal matrix no depletion of Cr or Ni could be observed over time. However, an increased presence of Cr and Ni in the primary layer was at the expense of Fe content.