Creep oxidation behaviour and creep strength prediction for Alloy 617

Creep experimental data was obtained by a series of creep tests with different stress levels at 950 °C for Alloy 617. Oxidation behaviour was investigated by observing the microstructures of fractured specimens after the creep tests. Oxidation thickness was measured quantitatively with the creep rupture times, and the oxidation microstructures were represented by a SEM image. In addition, the long-term creep strength for Alloy 617 was predicted by using a multi-constant method with two C instead of the conventional one with a unique C in the Larson-Miller (LM) parameter. For 105 h at 950 °C, the creep strength for the conventional method was 7.2 MPa, but for the multi-constant method it was reduced to 4.7 MPa. The conventional method did not thoroughly match with the creep rupture data, and revealed an overestimation for the prediction of the long-term creep strength. On the other hand, the multi-constant method revealed a good agreement with the creep rupture data, and its method was thus more accurate than the conventional one. This multi-constant analysis can be used to accurately predict the long-term creep rupture of Alloy 617.