A re-visit to the Haigh diagram with the effect of creep damage on the high cycle fatigue behavior of alloy 617M. (August 2021) - Ponnapureddy, Shiven
Highlights: The Haigh diagram at 700 °C is modified based on HCF-creep interaction tests. The modified Haigh line changes with an increase in hold time and the R -ratio. R -ratio is identified as the most decisive parameter in governing failure mechanism. Abstract: The present work is aimed at a re-evaluation of the Haigh diagram incorporating the effect of creep on HCF. HCF testing was carried out at 973 K with varying mean stress ( σm ) and alternating stress ( σa ) to generate the Haigh diagram. The influence of creep on HCF was investigated by imposing periodic holds at σm during the course of HCF cycling. Under such HCF-creep interaction tests, specimens were found to fail for certain σa -σm combinations that resulted in run-outs in the absence of superimposed creep holds, leading to a deviation in the Haigh diagram. Such deviation was more prominent with an increase in the σm (increase in R ) and the hold time. The test results obtained are correlated with microscopic and fracture surface analysis to understand the mechanism of crack initiation and propagation, as well as the role of precipitation under HCF-creep interaction.