| Superalloys, such as IN738 and IN738LC, have been used in the hot section as gas turbine blade materials. In order to preserve surface stability and mechanical properties of these materials, a protective oxide scale must develop on the surface. However, such oxide scales often crack or even fail as a result of the accumulation of growth and thermal stresses, thus the thermal and mechanical properties of oxide scales must be understood. IN738 and IN738LC have slight difference in carbon content and showed different oxidation behavior. From the isothermal oxidation experiment between 900 and 1050℃ IN738LC revealed better oxidation resistance than IN738. These materials both had outer scale consisted of mainly Cr₂O₃ with some TiO₂ and discontinuous internal oxides of Al₂O₃. It appeared that the additional Cr carbide in Cr₂O₃ resulted in IN738 suffering more cracks and failure at high temperature than IN738LC. This phenomenon was also seen in the case of cyclic oxidation experiments at 900-1100℃. |
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