A Study on the Cracking and Spalling of Some Common Oxide Scales Formed on Iron-Base Alloys by AE

The cracking and break up of some common oxide scales on the iron-base alloys during their oxidation at a constant temperature and in the subsequent cooling process has been studied by means of an acoustic emission(AE) technique.The time dependence of the accumulation counts and the temperature were obtained.The phase species of oxide scales on the tested alloys were determined by a microscope,a scanning microscope and especially the X-ray diffraction analysis.It can be stated from the experimental results that the oxide scales on alloys cracked and broke up during the cooling process except for the oxide scale on the alloy containing silicon which cracked in the period of the constant temperature oxidation.The α-Al₂O₃ scale on Fe-25Cr-10Al cracked and exfoliated most severly.The total counts of AE of the Cr₂O₃ scale on the Fe-25Cr-7.5Nb alloy is much higher than that of Fe-25Cr.The situations of Fe-25-Cr-4Ti and Fe-25Cr-9Mn alloys were similar to that of Fe-25Cr.