Corrosão a quente de diferentes superligas de niquel e cobalto

Abstract

This study investigated the hot corrosion resistance of three alloys: Inconel 718, Haynes 25, and Super Duplex 2507. Comparative analyses were conducted on polished surface samples exposed to a static air atmosphere at 800 °C using a Na2SO4 and NaCl mixture. The primary objective was to evaluate the influence of surface finish on hot corrosion resistance by analyzing mass variation and sample morphology after testing. The results indicated that the polished Inconel 718 sample exhibited the lowest corrosion rate due to the formation of a more stable and adherent protective oxide layer. In contrast, the Super Duplex 2507 showed the highest corrosion rate, with significant mass variation and evidence of severe degradation. The Haynes 25 superalloy displayed intermediate behavior, with moderate mass gain and relatively stable oxide formation. Morphological analysis revealed that the polished surface promotes the formation of more adherent protective oxides, while rougher surfaces facilitate contaminant penetration and accelerate degradation. Microhardness tests indicated a significant increase in surface hardness after exposure to the corrosive environment due to microstructural transformations and the formation of hardening oxides. This study emphasizes the importance of surface finish and appropriate material selection for applications involving high temperatures and aggressive atmospheres, providing valuable insights for the aerospace, petrochemical, and power.