INFLUENCE OF CHEMICAL COMPOSITION ON THE HOT OXIDATION OF CARBON STEEL – A REVIEW

• DOI: https://doi.org/10.22533/at.ed.3174162407068

• Palavras-chave: hot oxidation, scale, iron oxides, alloying elements, carbon steel.

• Keywords: hot oxidation, scale, iron oxides, alloying elements, carbon steel.

• Abstract:

  The hot forming of steels is associated with surface scales formed by layers of oxides whose oxidation kinetics and morphology are not fully understood, where there are several parameters that influence their formation. The chemical composition of carbon steel can influence the oxidation kinetics as well as the morphology of the oxide layers formed at high temperatures, which makes understanding these phenomena challenging. The fact is that each element behaves differently during steel oxidation. The alloying element Si, when present in the composition of steel, oxidizes to form silica, SiO2. This oxide, in turn, at high temperatures, reacts with wustite, FeO, forming a complex oxide, fayalite, Fe2SiO4. The fayalite film has a protective characteristic, increasing the steel's resistance to oxidation and the adhesion of the oxide layers. Other alloying elements, in addition to Si, which have a greater tendency than iron to oxidize, and which form protective oxides, such as Al and Cr, can be added to the steel composition to promote certain resistance to oxidation, reducing the thickness of the layers. of oxides. However, the formation of an alloying element oxide film will depend on its percentage in the steel composition. Alloy elements with low percentages in the steel composition tend not to form a continuous film, being precipitated in the wustite layer, close to the scale/substrate region, and in the steel, participating in internal oxidation. Low concentrations of alloying elements, even if they do not form continuous films, can influence the formation kinetics of other oxides. This review provides a comprehensive overview of the influence of alloying elements in hot oxidation regimes on the kinetics and mechanism of oxidation of carbon steels.