Structural characterization of Ni-based superalloy manufactured by plasma transferred arc-assisted deposition

The manufacture of a Ni-based superalloy (GH163) was conducted by plasma transferred arc-assisted deposition starting from master alloy powders. The microstructure of the manufactured samples was characterized by using optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the as-deposited samples exhibited a fine and homogenous cellular dendrite structure with a stronger crystallographic orientation along <001> direction. Electron probe X-ray microanalyzer (EMPA) revealed that the composition distribution in the whole sample was pretty uniform and no significant segregation occurred in the interface regions between deposited layers. After solid solution and ageing treatments, a large number of fine γ′ particles with a size of about 20–30 nm precipitated inside grains of the alloy. Electron diffraction using TEM indicates that the γ′ phase precipitated has a FCC structure and exhibited a completely coherent relation with the matrix. In addition, a few fine carbide particles were formed at grain boundaries, which are believed to be good for creep strength of the superalloy. The present results demonstrate that the plasma transferred arc-assisted deposition is a promising technology for the manufacture of Ni-based superalloy with fine and homogenous microstructure.