液态金属冷却法制备镍基单晶高温合金铸件的研究进展

At present, high rate solidification (HRS) technique had been widely used in industry. As compared with HRS technology, liquid metal cooling (LMC) technology had higher temperature gradient, and thus it had an advantage in the preparation of single crystal turbine blades with large size. This paper summarized the working principle and temperature gradient of HRS and LMC technologies, as-cast microstructure, solution treatment, formation tendency of casting defect and mechanical properties of single crystal superalloys (prepared via HRS and LMC technologies). As compared with HRS technology, LMC technology can significantly refine dendrite arm spacing and reduce the microsegregation tendency of alloying elements in as-cast microstructure. LMC technology can effectively reduce the difficulty of solution treatment and decrease number and size of micro-pores in both as-cast and heat-treated single crystal superalloys. Meanwhile, LMC technology can effectively reduce the formation tendency of as-cast defects (e.g. freckles and stray grain at platform region). At relatively low service temperature, LMC technology can effectively improve the low cycle and high cycle fatigue properties of single crystal superalloys. However, LMC technology might led to relatively poor crystal orientation control effect during grain selection and Sn contamination, and the above problems needed to be solved by optimizing directional solidification process parameters and shell preparation process.