Structure and Oxidation Behavior of Tribaloy Alloy With Iron and Aluminum Additions

Abstract

Abstract T800 alloy with nominal chemical compositions of Co-17.5Mo-28.5Cr-3.4Si (wt%), T800 alloy with an 5.0 wt% iron addition and T800 alloy with additions of both 5.0 wt% iron and 5.0 wt% aluminum were produced by the vacuum arc re-melting method, in order to investigate the effect of Fe and Al additions on microstructure, hardness and oxidation performance of T800 alloy. The weight gains per unit area vs. time plots were obtained during isothermal oxidation at 800°C and 1000°C in air. The oxide morphology and microstructure were analyzed by X-ray diffraction (XRD), scanning electron microscopy with EDS (SEM/EDS). The results showed that Fe addition refined Laves phase in the T800-Fe alloy and volume fractions of the primary Laves phase decreased for T800-Fe alloy and T800-Fe-Al alloy. Hardness measurement showed no significant difference for the three alloys. The T800-Fe alloy exhibited a slightly reduced weight gain during air-exposure at 800°C, however, a pronounced improvement of oxidation resistance was visible for T800-Fe-Al alloy. In oxidation test at 1000°C, T800-Fe alloy and T800-Fe-Al alloy showed significantly low weight gains compared to the T800 alloy, especially the latter. Its oxidation kinetics was more stable during later oxidation stage in the present oxidation time. Besides, T800 alloy and T800-Fe alloy presented scale spallation at different degree but no oxide spallation was observed for T800-Fe-Al alloy.