Effect of directional solidification on the microstructure and mechanical properties of a 2th Generation Ni-base single crystal superalloy CMSX-4

Ni-base super alloy CMSX-4, as the 2nd generation of single crystal alloys, had been used since ‎‎1990 in different gas turbine blades. In this research, the samples were prepared from poly ‎crystal ingot alloy which was made with VIM and VAR techniques. The carrot of a single ‎crystal super alloy was made by Bridgman furnace. After casting the same solution and aging ‎treatment were carried out. The cast microstructure of the single crystal super alloy consists of many ‎directed dendrites toward (001) direction with some eutectic phase and a few amounts of ‎carbides. In heat-treated microstructure, all of the γ phases ordered as the cubic shape. The ‎misorientation was determined in order of 6 to 7 degrees by laue and RO-XRD techniques. ‎The tensile strength of CMSX-4 alloy was determined at the temperature of 25 and 870 °C. ‎The results showed that the UTS was 1060 and 390 MPa respectively for polycrystalline and ‎single crystal were 1066 and 1163 MPa. SEM observations confirmed that these behaviors ‎were affected due to grain boundaries and the precipitation’s morphology at high ‎temperatures. ‎