Microstructure and Chemical Composition of Fe-Cr Alloy Tempered in High Temperature and Atmosphere Containing Ar-SO2

Abstract

MIcrostructure and cheMIcal coMposItIon of fe-cr alloy teMpered In hIgh teMperature and atMosphere contaInIng ar-so2The paper presents the microstructure, chemical and phase composition of thin scale, obtained as a result of hightemperature corrosion of X20Cr13 stainless steel. Samples were exposed to gas atmosphere of the following composition: 0.25 vol.% of SO2 and 99.75 vol.% of Ar at 600 °C for 5 h. As a consequence, thin compact scale was formed on steel surface. This scale consisted of three different zones. An amorphous zone was formed close to steel surface. Then, nanocrystalline zone could be observed. Finally, larger grains were formed during the corrosion process. The analysis of the chemical composition revealed higher concentration of chromium near steel surface. In contrast, to chromium, the content of iron, increased near the scale surface. It was found out that the (Cr, Mn, Fe)5O12 phase appeared in the thin scale.

Archives of Metallurgy and Materials

“…The degradation rates of steel are higher in the environment containing SO 2 [8], which can be attributed to more defects in metal sulphides in comparison with metal oxides. What is more, they form a low-temperature eutectics in the sulphide system [9]. There are also reports that the presence of SO 2 in the atmosphere hinders the process of Cr 2 O 3 formation which has a protective function [10].…”