High Temperature Oxidation of Chromium in air: Facts and FigureWednesday (28.09.2016) 12:00 - 12:15 Part of:
Chromium is widely utilized as an alloying element in engineering alloys such as stainless steels and Ni-based alloys due to the formation of protective chromia scale (Cr2O3). In fact, high temperature behavior of pure chromium above 1000°C shows very interesting features such as volatilization, scale wrinkling, and worst of all extreme nitridation when exposed to air. In this paper, a these facts were considered for isothermal oxidation of pure chromium. Thermogravimetric study of chromium oxidation in oxygen (Ar-20%O2), pure nitrogen (N2-5%O2), and air (N2-21%O2) indicated the role of single- and multi-oxidants on kinetics of oxidation. Measurements at temperature range of 950-1200°C resulted in activation energy for oxidation and nitridation in single oxidant atmospheres. It is revealed that the oxidation kinetics in air is significantly affected by nitridation. Isothermal in-situ acoustic emission measurements revealed that scale detachment at high temperature is correlated to the multistep mass gains behavior for pure chromium. Facts and figures found in this works are finally correlated to the large discrepancies observed in reported oxidation rates for chromium during last decades.