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Abstract
The effect of prior oxidation on the room temperature fatigue life of coarse grained Ni based superalloy, RR1000 has been performed at an R ratio of 0·1 with two pre-oxidation times: 100 and 2000 h at 700°C. These pre-exposures produce extensive oxidation damage. The room temperature high cycle fatigue life of the pre-oxidised specimens has been compared to as received specimens. At a maximum applied stress of 800 MPa a significant fatigue life deficit is observed in the pre-oxidised testpieces. This is accompanied with the observations of significant cracking of the external chromia scale and the intergranular internal oxides within the area of maximum stress. Preferential cracking of oxides may lead to early crack initiation and consequently a reduction in total fatigue life.
Acknowledgements
The authors acknowledge, with thanks, the assistance provided by Jifeng Sun in producing the FIB sections. S. Cruchley is grateful for financial support provided by the Engineering and Physical Sciences Research Council (EPSRC) and Rolls-Royce plc.