Low-cycle fatigue properties of nickel-based superalloys processed by high-gradient directional solidification

Abstract

The low-cycle fatigue (LCF) properties of DD10 (single-crystal) and DZ53 (columnar-grained) superalloys solidified by liquid-metal cooling (LMC) and high-rate solidification (HRS) processes have been systematically investigated. It was found that the LCF life of DZ53 solidified by LMC was obviously better than that solidified by HRS. In contrast, for DD10, LMC showed no remarkable influences on LCF properties at high temperature and only improved LCF properties at intermediate temperature. Microstructure examination showed that the cracks generally initiated at micropores in the subsurface at intermediate temperature. However, the cracks occurred on the surface due to oxidation, or persistent slip bands near script-MC at high temperature. Therefore, the benefits of LMC technique can be attributed to both of the reduced casting defects which significantly affect the LCF properties at intermediate temperature and the improved microstructural homogeneity which was strongly correlated to the LCF properties of alloys at high temperature.