Abstract
Abstract An experimental study of the thermal fatigue behaviour of polycrystalline nickel-base superalloy 263 sheets was conducted using a laboratory combustor system. Tests were done on 0.91 mm and 1.2 mm thick sheets. Square specimens (100 × 100 mm) with a 14.85 mm diameter electrodischarge-machined hole at the centre were cycled between a hot combustor gas jet and a cold jet. The maximum specimen temperature was 900 °C, and the minimum temperature was 50 °C during a 2 min fatigue cycle. The number of cycles to crack initiation was determined. It was found that this change in sheet thickness did not significantly alter thermal fatigue life. Scanning electron micrographs revealed that out-of-phase non-isothermal fatigue (resulting from thermal stresses) assisted by grain boundary oxidation is the main mechanism of failure in these tests.
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