The Effect of Melt Holding Time and Vacuum Pressure on the High ‎Temperature Fatigue Life of Ni Based Hastelloy X Superalloy

The aim of this study is the improvement of fatigue properties via controlling the vacuum pressure and melt holding time. The vacuum pressure of 10-1 and 10-3 mbar were applied during melting in VIM and the melt were kept for 3 and 30 minutes. The results show that with increasing the pressure from 10-1 to 10-3 mbar at 3 and 30 min, the grain size increase from 44 to 66 µm and from 71 to 78 µm, respectively. Also, the volume fraction of carbides at 3 min decrease from 9.6 to 8.05 vol% with increasing the pressure and it also decrease with increasing time as well. High temperature low cycle fatigue test was carried out at strain of 0.6% and temperature of 750°C. At 3 and 30 min with increasing pressure, the cycling life increase 26% and 15%, respectively. At constant pressure, with decreasing time, the cycling lives also increase.