Influence of creep damage on HCF behavior in alloy 617 M

The influence of creep damage on high cycle fatigue (HCF) in Alloy 617 M at 700 °C was investigated by incorporating periodic holds at the (maximum stress (σmax) during HCF cycling. The effect of creep damage in “HCF-creep interaction test” is reflected in the form of specimen failure at stress levels corresponding to the occurrence of run-out observed under pure HCF cycling. However, in-situ precipitation was found to play a major role at longer durations of hold during HCF-creep interaction by enhancing the strength of the material and offsetting the effect of creep damage. On increasing the temperature during the application of hold to 750 °C, the precipitates started coarsening, further augmenting the creep damage, resulting in early failure. Detailed fractography investigations showed significant intergranular cracking which corroborates the effect of creep damage on HCF cycling. In addition to this, oxide and precipitation induced cracking was noticed, bringing out the complex nature of damage evolution in “HCF-creep interaction” tests. •HCF-creep interaction tests were conducted by applying hold time in the HCF waveform.•Creep damage depend on the HCF block-size, hold-time and hold temperature.•Creep damage manifested in the form of intergranular cracking.