Evaluation of Hot Corrosion Behavior of APS and HVOF Sprayed Thermal Barrier Coatings (TBCs) Exposed to Molten Na2SO4 + V2O5 Salt at 1000 °C

Abstract

Hot corrosion is a very destructive failure mechanism for thermal barrier coatings (TBCs) during service conditions. In the present study, a CoNiCrAlY is coated using atmospheric plasma spray (APS) and high velocity oxy-fuel (HVOF) techniques which produces TBCs that were exposed to 50% Na<inf>2</inf>SO<inf>4</inf> and 50% V<inf>2</inf>O<inf>5</inf> molten salts at 1000 °C. The top surface was visually inspected at the end of each four-hour cycle to determine the lifetime of TBCs. The failure criteria required for the termination of the hot corrosion cycles was assumed to be 25% cracking and spallation of top coats. X-Ray Diffraction (XRD) analysis was performed before and after hot corrosion tests in order to observe new phases which may occur in the top coating. After scanning electron microscopy (SEM) images of cross-section samples of hot corrosion tests are completed, samples were taken. As a result, it has been observed that the lifetimes of HVOF bond-coated TBCs are longer. © 2018 Elsevier B.V., All rights reserved.