Investigation of thermal spray coatings on additively manufactured alloy 718 substrates

Alloy 718 substrates were additively manufactured via electron beam-powder bed fusion (EB-PBF), followed by post-processing, using shot peening (SP), hot isostatic pressing (HIP), and a combination of both. The EB-PBF built samples were analyzed in comparison to cast alloy 718 to understand the manufacturing and post-processing influence on the corrosion and erosion performance. The substrates were subsequently coated with NiCoCrAlY using the high-velocity air fuel (HVAF) thermal spray process. Hot corrosion behavior of both coated and uncoated samples was evaluated after 1008 h of exposure to Na 2 SO 4 at 650 °C. The uncoated samples exhibited severe hot corrosion characterized by non-uniform and flaky oxide-scale formation. In contrast, the coated samples showed comparatively less severe oxide degradation, indicating improved corrosion resistance under the tested conditions. The erosion performance revealed severe material removal in the uncoated samples, particularly for the as-built surfaces due to loosely bonded and less deformed particles remaining from the EB-PBF process. Despite the influence of post-processing on substrate surface characteristics, all coated samples exhibited comparable erosion resistance, highlighting the reliability and consistency of the HVAF-sprayed NiCoCrAlY coatings.