Oxidation Resistance and Nanoscale Oxidation Mechanisms in Model Binary and Ternary Alloys Exposed to Supercritical Water

• Main Author: Li, Weimi
• Other Authors: Newman, Roger C.
• Language: en_ca
• Published: 2012
• Subjects: Supercritical water; Oxidation; Fe-Cr alloys; Third element effect; 0794
• Online Access: http://hdl.handle.net/1807/33288

The oxidation behavior of model binary and ternary alloys in supercritical water (SCW) was examined. Binary alloys contained 9 or 14 at% Cr. Ternary alloys had 1.5 at% of one of the following elements: Si, Al, V, Mn or Ti. Samples with different surface finishes were exposed to SCW for up to 500 hours. The oxidized samples were characterized using gravimetry, SEM, HRTEM and EDX. After exposure, a uniform double layer oxide with outwardly grown magnetite inwardly grown Fe-Cr mixed oxide was detected on most of samples. Alloys contains 14 at% Cr or/and 1.5 at% Si showed a mixed oxidation mode, where relatively thick double layer oxides coexisted with thin protective oxide. The coverage with the thin oxide increased with the increase of deformation and/or Cr and/or Si content. A 20 nm thick Si-enriched layer was detected at such alloy/oxide interfaces. This behavior is very similar to “third element effect”.