Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5015015 | International Journal of Fatigue | 2017 | 29 Pages |
Abstract
Very high cycle fatigue (VHCF) properties of a Ni-based single crystal superalloy (CMSX-4) have been studied at 20 kHz and temperature of 1000 °C between 106 and 1010 cycles. Tests have been performed using 4 microstructural states of CMSX-4 (as-received, thermally aged at 1100 °C/300 h and creep deformed in tension at 1100 °C/120 MPa for 24 h and 100 h) to evaluate the impact of microstructure degradation on VHCF fracture mechanisms and lifetime. At ratio of R = â1, crack initiation at internal casting pore and subsequent planar slip propagation is systematically observed for all investigated microstructure. At ratio of R = 0.8, crack initiation occurs from multiple internal or subsurface pores. Mode I micro-propagation is observed and associated with the addition of a large mean stress. In specimens prior crept-deformed in tension, the density of micro-cracks is higher due to the precipitation coarsening. Moreover, the crack propagation path is affected by the morphology of the γ/γⲠmicrostructure. Both phenomena result in reduced VHCF lifetimes in comparison to the reference state.
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Authors
A. Cervellon, J. Cormier, F. Mauget, Z. Hervier,