Effect of powder size segregation on the mechanical properties of hot isostatic pressing Inconel 718 alloys
Xiaosheng Tian, Jie Wu, Zhengguan Lu, Rui Yang, Lei Xu
Abstract
Pre-alloyed powder of Inconel 718 alloy was prepared by electrode induction melting gas atomization (EIGA) and powder metallurgy (PM) Inconel 718 alloys were made through hot isostatic pressing (HIPing) route. The change in volume of large size parts (special-shaped cylindrical capsule) has a much lower effect on the alloy than the powder size. The vibration of the powder filling process over a long time causes the particle size segregation phenomenon that the proportion of coarse particle powders in top part increases, and the proportion of finer particle powders in middle and bottom part increases. This phenomenon has little effect on tensile strength of PM Inconel 718 alloys at room temperature and 650 °C, but has a significant effect on elongation, room temperature impact properties, and stress rupture life at 650 °C/725 MPa. Compared to finer particle powders, the plastic deformation of coarse particle powders is small and a large number of under-deformed powder particles are retained, forming prior particle boundaries (PPBs) and reducing the bonding strength between powder particles. In order to avoid particle size segregation, optimized process parameters and reasonable particle size should be used.