Corrosão sob tensão em aço ASTM A516 com revestimento Cr3C2-25NiCr por HVOF

Abstract

Thermal spray deposited coatings (HVOF) are widely used on the surface of steel substrates to protect against corrosion and wear, in order to increase the durability of the material. The Cr3C2-25NiCr composite coating plays a protective role, with the NiCr matrix providing corrosion resistance and the chromium carbide providing durability and high resistance to abrasive wear. In this study, the protective behavior of the Cr3C2- 25NiCr coating was analyzed under conditions conducive to stress corrosion. For this purpose, three ASTM A516 steel specimens were used as the metallic substrate, in addition to which they were subjected to different levels of plastic deformation by threepoint bending (1%, 5% and 15%). To simulate the corrosive environment, the samples were placed in an autoclave at a temperature of 60 °C and a CO2 pressure of 20 bar, and the test lasted three months. To obtain the results, metallography, pitting depth analysis, crack quantification and SEM images were carried out. The coating did not show corrosion, but many cracks were identified and pitting was found just below them. However, the severity of the damage intensified as the percentage of deformation increased.