There is an upsurge of research interest on Alloy 718 additively manufactured (AM) by electron beam powder bed fusion (EB-PBF) technique in aero and land-based gas turbine engines. However, the surface quality hence the oxidation performance of the manufactured components is of great concern. Along with surface roughness resulted from partially melted powder particles, surface defects such as balls, satellites, microcracks as well as up-skin and down-skin surfaces can enhance the vulnerability of the manufactured parts to oxidation. When the surface is unable to withstand the exposed environment adequately, oxidation can be triggered. The surface-induced failures are increasingly becoming more challenging as the AM components often have complex geometries that render them even more difficult to finish. So, the relatively poor surface finish is the barrier to the full exploitation of the AM industry.

In the present study, a NiCoCrAlY coating deposited by high velocity air-fuel (HVAF) technique on EB-PBF manufactured Alloy 718 was investigated. The oxidation behavior of the parts was investigated in an ambient air environment at 650 and 800 °C for 168 h. The oxidation behavior of the coated samples was analyzed by scanning electron microscopy (SEM) equipped with energy disperse spectroscopy (EDS). The oxidation behavior of the parts was significantly improved after deposition of the thermal spray coating. The oxide scale formed on the surface of the EB-PBF Alloy 718 without the coating was rich in Cr and the oxide scale formed on the surface of the EB-PBF Alloy 718 with NiCoCrAlY coating was rich in Al.