Effect of porosity and eutectics on the high-temperature low-cycle fatigue performance of a nickel-base single-crystal superalloy

This work investigates the separate influence of porosity and gamma/gamma'-eutectics on the low-cycle fatigue life of a single-crystal Ni-base superalloy at high temperatures. A conventional vacuum furnace heat-treatment but also integrated heat-treatments in a hot isostatic press are applied to produce different material variants of the same alloy. High-resolution electron microscopy revealed that both pores and gamma/gamma'-eutectics act as crack starters, thus initiating early failure. Moreover, the results indicate that remaining gamma/gamma'-eutectics can weaken the fatigue resistance even more than pores. Furthermore, the results confirm the beneficial effect of proper integrated hot isostatic pressing heat-treatments on the fatigue performance. (C) 2018 Acta Materialia Inc. Published by Elsevier Ltd.