Advances in solidification characteristics and typical casting defects in nickel-based single crystal superalloys

Single crystal (SC) superalloy is a kind of complex structure and multi phase materials. With the increase of the degree of alloying and the content of refractory elements, or the more complicated structure and larger size of the casting made of SC superalloy, it is essential important to suppress the formation of solidification defects to improve the quality and performance of the blades. The microstructure and solidification defects of single crystal alloy are not only related to the composition of the alloy, but also depend on its solidification characteristics and technological conditions. The paper first summarizes the research progress of the solidification characteristics for advanced SC superalloys, focusing on analysis of the effects of solidification characteristics and processing parameters on the formation and its mechanics for two typical directional solidification defects, crystallographic orientation deviation and stray grains. Then some methods and approaches to suppress such defect formation for complex single crystal blade have been reviewed.