Tensile cracking during thermal cycling of alumina films formed by high-temperature oxidation

✍ Scribed by V.K Tolpygo; D.R Clarke

• Book ID: 104403943
• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 577 KB
• Volume: 47
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/s1359-6454(99)00216-5

✦ Synopsis

AbstractÐPlastic relaxation of the stresses, produced by high-temperature oxidation and thermal contraction mismatch on cooling, decreases residual compression in the oxide. For this reason, slow cooling from the oxidation temperature is expected to have a bene®cial eect on spalling resistance of protective alumina ®lms. However, there exists a possibility of creating tensile stress in the oxide upon subsequent heating. With increasing stress relaxation on cooling, the magnitude of the tensile stress also increases which may lead to cracking of the oxide at high temperature. Experimental evidence shows an adverse eect of stress relaxation on the mechanical integrity of alumina ®lms formed on Fe±Cr±Al heat-resistant alloys. High cooling and heating rates between oxidation cycles are required to prevent tensile failure of the oxide.