Oxidation of Heat-resistant Alloys

The oxidation performance of three novel, heat-resistant alloys, namely KHR35C HiSi, KHR45A LC, and UCX, was studied at relatively low temperatures (i.e. 650 and 750 °C) for 1,000 h. The study was focused mainly on exploring oxide-layer growth and characterizing the oxide phases in order to prevent or minimizing metal dusting in carbonizing environments. The specimens were examined by visual and metallographic examination, SEM/EDX, XRD, and weight-change measurements. The results have been compared with a previous, short-term study (100 h) in order to understand the influence of exposure time on oxidation. It is concluded that exposing the alloys to air at 650 and 750 °C led to the formation of oxides of chromium, nickel, iron, silicon, and iron-containing spinels. Moreover, increasing the exposure time, temperature or both resulted in further oxide growth, leading to more continuous, adherent, and thicker oxides. The alloys, however, did not form a completely protective scale, especially at 650 °C, even after 1,000 h of exposure.