Avaliação da resistência à corrosão localizada da superliga de níquel Nimonic 80A para diferentes tratamentos térmicos

Abstract

The Ni-base superalloys, or simply Ni superalloys, characteristically show a combination of elevated oxidation resistance and strength resistance in high temperatures, therefore known as high temperature alloys. They are applied in the construction of components of jet turbines, space vehicles, nuclear reactors, submarines, among others. In the present work, the evaluation of the resistance to localized corrosion by electrochemical techniques was carried out after the application of different heat treatments in a Nimonic 80A superalloy. The difference imposed in the heat treatments, besides the solubilization time, was the addition of an intermediate treatment before the aging treatment, commonly known as stabilization. From this, electrochemical techniques such as the potentiodynamic polarization, the determination of CPT based on ASTM G150 and the DL-EPR were used to evaluate the effect of the heat treatments in the sample. The treated samples were less sensitive than the sample received, according to DL-EPR. However, the evaluation by polarization curve was inconclusive, thus it was not possible to determine the CPT due to the high potential applied to the material, above its pitting potential.