Experimental work has been carried out on waisted specimens to investigate the effect of fatigue on oxidation damage for a nickel-based superalloy at high temperature (700°C~800°C). Focused Ion Beam (FIB) microscopy of the tested specimens revealed surface oxide scale and internal micro-voids beneath the oxide scales, particularly at 750°C and 800°C. To examine the effect of cyclic stress on oxidation damage, three points on the surface of the waisted specimen, which have different stress levels due to the variation of the cross sectional area of the waisted specimen, were selected for the post-test FIB examination. The measured oxidation damage from these three locations indicates that the increase in cyclic stress level tends to enhance the extent of oxidation damage for temperatures at 750°C and above, whilst the influence of cyclic stress appeared to be insignificant at 700°C and below. Further energy dispersive x-ray (EDX) analyses show the enrichment of Cr and Ti in the surface oxide scales, together with lower Ni and Co levels. Internal oxidation is also found from both secondary ion imaging and EDX analyses.
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