Effect of Cr Content on the High Temperature Oxidation of Low Alloy Steels

Abstract

Abstract In the case of low carbon steel (AISI 1015, AISI 8617, AISI 4115 steel), the high-temperature oxidation behavior at different temperatures (600, 700, 800, 900, 1000 ℃) was studied by mass gain analysis, phase analysis (metallographic microscope, energy-dispersive spectroscopy, and x-ray diffraction). The oxidation process was performed from 2 to 100 min. As the oxidation time increased, the trend of mass gain per unit area switched from linear to parabolic law regardless of steel grades used in this study. As the chromium content increases, the duration of time during which the oxidation rate follows a linear relationship decreases. The structure of oxides can generally be classified into two types: outer oxide and inner oxide. The outward diffusion of Fe cations primarily leads to the formation of outer oxide, while the inward diffusion of O anions is responsible for the formation of chromium and inner oxides. In the low-alloy steel with higher chromium content, the thickness of the mixed oxide layer containing Cr increased, and the oxidation rate decreased at all oxidation temperatures.