科研之友
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摘要
K273 superalloys with alloying of aluminium were cast by intermediate frequency induction furnace. The oxidation resistance of test alloys at 1000 degrees C for 500 hours is examined according to the oxidation weight gain method. The scale morphology and composition are studied using scanning electron microscope (SEM) and x-ray diffraction (XRD), respectively. The effects of the transferring of ions and electrons on oxidation resistance are further studied microscopically using establishing semiconductor oxide models. As revealed, the composite scale compounded by Cr2O3, Al2O3 and spinel MCr2O4, with flat and compact structure, fine and even grains, provide a strong oxidation resistance of K273 superalloy. The mechanism of powerful oxidation resistance of the composite scale consists in the forming of p + n-type semiconductor oxide, which consumes most of the surplus negative and positive ions in oxide scales; the number of the mobile ions and electrons dropped enormously, and the transferring rate of them fells heavily. Therefore, the oxidation rate of the matrix metal significantly decreases.
