The microstructure characteristics and anodic electrochemical behavior of Hastelloy X fabricated by directed energy deposition were investigated in this work. The microstructure of as-deposited Hastelloy X mainly consisted of columnar dendrites along the deposition direction. The dendrite trunk was the γ matrix, and the inter-dendritic region was composed of the Mo-rich γ phase and carbides. After solution heat treatment, the dendrites disappeared and the carbides were randomly distributed in the γ matrix. The samples in two different states presented different polarization behaviors because of their microstructural differences. After transpassive dissolution, the surface morphology of the as-deposited sample was uneven due to preferential dissolution in the inter-dendritic region. This uneven morphology could be dramatically improved by increasing the applied current density during dissolution or solution heat treatment before dissolution. It was also determined that the existence of a transpassive film reduced the current efficiency and hindered the dissolution of metal. This study could provide an effective theoretical guidance for electrochemical machining of directed energy deposited nickel-based superalloys.

本工作研究了通过定向能量沉积制备的哈氏合金X的微观结构特征和阳极电化学行为。沉积后的哈氏合金X的微观结构主要由沿沉积方向的柱状枝晶组成。枝晶主干为γ基体，枝晶间区域由富Mo的γ相和碳化物组成。固溶热处理后，枝晶消失，碳化物随机分布在γ基体中。处于两种不同状态的样品由于其微观结构差异而呈现出不同的极化行为。经过被动溶解后，由于优先在树突间区域溶解，沉积态样品的表面形态不均匀。通过增加溶解或溶解前固溶热处理期间施加的电流密度，可以显着改善这种不均匀的形态。还确定了透射型薄膜的存在降低了电流效率并阻碍了金属的溶解。该研究可以为定向能沉积镍基高温合金的电化学加工提供有效的理论指导。