Comportamento de oxidação em temperatura elevada do aço inoxidável austenítico AISI 201LN

Abstract

With a proposal to be more economical alloys, the 200 series austenitic stainless steels have shown increasing market shares, often replacing 304 stainless steel in domestic applications. Despite their usage also in high-temperature environments, the oxidation behavior in these situations is not yet widely understood, for there is a lack of investigations specifically aimed at those alloys. This project investigated the high-temperature oxidation behavior of AISI 201LN austenitic stainless steel. Samples were oxidized in air and characterizations via optical microscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy and X-ray diffraction were carried out. At 700 ºC little oxidation took place and the material presented a thinner and more compact oxide layer, with some defects like nodes and spallation; on the other hand, at 750 and 800 ºC the mass gain due to oxidation was approximately ten times more intense, and the material exhibited an oxide layer with a very irregular, porous morphology, with many cracks and severe spallation. Such differences were related to the different oxides formed at each combination of time and temperature, with the formation mainly of simple and complex Cr and Mn-rich oxides at the lowest temperature, while at the highest temperatures the formation of an external Fe-rich oxide took place. Ultimately it could be concluded that the oxidation resistance of the material is mainly driven by Mn, which induces the formation of non-protective oxides, detrimental to the oxidation resistance of the alloy.