铸型正反转搅动对精密铸造 K4169 合金凝固组织和室温力学性能的影响

The service temperature of K4169 superalloy aeronautic turbine disks and other important aeronautic components is generally below the equi-strength temperature, and grain refinement can significantly improve the service performance. Compared with the conventional gravity casting process, the centrifugal casting process as a dynamic grain refinement method plays an important role in grain refinement, feeding, and molten filling of the casting. A precision casting with typical structural characteristics of the K4169 superalloy was prepared using the centrifugal casting process with the mold positive and negative rotation method and the conventional gravity casting process, respectively. The alloy microstructure, element segregation, secondary phase distribution, fracture microstructure, and mechanical properties at room temperature were compared and studied under two process conditions. The as-cast structure of the K4169 superalloy can be significantly refined using the mold positive and negative rotation method. The grain refinement of the experimental alloy was the most significant when the casting mold was reversed for 4 s, and the grain size under gravity casting decreased from (5.37 ± 0.21) mm to (0.27 ± 0.01) mm. Also, the primary phase of the experimental alloy was broken and the dendrite morphology was degraded that the coarse dendrites were replaced by broken dendrites and rose-shaped crystals after positive and negative rotations. Compared with unidirectional rotation, the segregation of alloying elements decreased, the number of Laves phases in the solidified structure was reduced, and the number of carbides was slightly increased. The tensile strength of the K4169 alloy at room temperature under the positive and negative rotation duration of 4 s was 31.4% higher than that under conventional gravity casting.