| The isothermal oxidation behavior of W-Mo-(29~48wt%)Cr alloys were investigated at 1000, 1100 and 1200℃ in air. The oxidized layers and their morphologies were analyzed by scanning electron microscopy, X-ray diffraction and electron probe microanalysis. The oxidation resistance was improved as the Cr content increased. The oxidation rates of W-Mo-Cr alloys containing 41~48wt % Cr followed a parabolic rate law and the measured rate constant(kp) of oxidation was approximately 1.92 × 10(-2)~9.55 × 10(-11)(g/cm2)2sec(-l) between 1000℃ and 1200℃. At the surface of this alloys, a Cr2O3 protective layer was continuously formed, and below the protective layer, CrZO3 internal oxide formed. The depth of internal oxidation zone was found to decrease with increasing Cr content. The oxidation resistance of W-Mo-(29~35wt%)Cr alloys was good at 1000℃, however, decreased rapidly as the temperature increased. The observed optimum Cr content for oxidation resistance was more than 35% at 1100℃ and 41% at 1200℃. The oxidation mechanism of W-Mo-Cr alloys was proposed. |
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