STUDIES ON HIGH TEMPERATURE OXIDATION BEHAVIOR OF HEAT TREATED PLAIN CARBON STEELS

Abstract

There has been a long history of studies on the oxidation behavior of carbon steel at high temperatures. The oxidation behavior and the scale structure developed are complex. The microstructure and the ratio of the three classical layers of wustite, magnetite and hematite may be difficult to identify. In this study, the effect of heat treatment at 900oC (annealing, normalizing, quenching) on high temperature oxidation behavior of plain carbon steel with the help of their microstructural and other changes were studied. For this, the oxidation behavior of a plain carbon steel with three different carbon percentage (low, medium and high carbon steel) was investigated on heat treated and non-heat treated samples by performing the test in static air at high temperatures (850oC). The result of oxidation of heat treated samples and non-heat treated were compared with help of the scale characterization and weight gain method. For this purpose, heat treated and non-heat treated samples were examined under the scanning electron microscopy(SEM), energy dispersive spectroscopy (EDS), optical microscopy and X-ray diffraction (XRD). The study reveals that as grain refinement takes place by heat treatment, the oxidation diffusion through grain boundary increases in other words as the number of grain boundaries increase oxidation rate increases and this is determine by oxide scale characterization and weight gain method with help of micro balance. In this study, the minor effects such as residual stresses and other internal defect are neglected.