The Role of Minor Compositional Variations in the Oxidation Behavior of Chromium-Molybdenum Steels

Oxide scale growth kinetics of 1.25Cr-0.5Mo and 2.25Cr-1Mo steels have been investigated and oxide scales have been characterized. In spite of the considerable difference in chromium contents of the two steels, their oxidation kinetics have been found to be similar. The similarity in oxidation behavior has been associated with formation of a protective innermost layer of silicon rich oxide in the case of 1.25Cr-0.5Mo steel and absence of such a layer in the case of 2.25Cr-1Mo steel, suggesting predominating role of Si over Cr.