Revealing the interrelation between process parameters and microstructure to promote the mechanical performance for Hastelloy-X.

In this study, we investigated the effects of varied process parameters on the defect, molten pool morphologies, microstructures, and hardness of HX, and established the correlation based on the Hall-Petch relationship. The formation mechanism of different types of defects, which are formed by increasing energy density, is systematically explained. The dendritic/cellular structure analysis via detailed Scanning electron microscope (SEM) examination found that the size of dendritic arm spacing was affected significantly by varied energy densities. Higher energy input reduces the temperature gradient and solidification rate, which results in the increase of primary dendritic arm spacing (PDAS). In addition, the grain boundaries of dendrite can improve the mechanical properties, especially the hardness. The hardness test results show that the hardness value increased with the decrease of PDAS, which exhibited this linear relationship illustrated by the Hall-Petch relationship. [ABSTRACT FROM AUTHOR]