OXIDATION BEHAVIOR OF A NEW Ni-Fe-Cr-Al ALLOY FOR ELEVATED TEMPERATURE APPLICATIONS

A new type of alumina-forming Ni-Fe-Cr-Al based alloy (HAYNES (R) HR-224 (TM) alloy) has been recently developed for applications in harsh oxidizing environments. The new developmental alloy is a solid solution strengthened alloy designed to exhibit excellent oxidation resistance and fabricability (i.e. weldability, formability, and processing) characteristics. The cyclic oxidation resistance of HR-224 alloy is superior to several chromia-forming heat-resistant alloys in harsh oxidizing environments, such as flowing air, air with water vapor, and combustion (i.e. burner-rig oxidation) environments. Preliminary results on a production-scale heat of HR-224 alloy indicate that it exhibits improved or comparable oxidation resistance to the alumina-forming Ni-Cr-Al based 214 (R) alloy. Isothermal oxidation testing at 982 degrees C confirmed that alloy indeed forms a continuous, adherent, and slow-growing Al2O3 scale, while 214 alloy formed a duplex oxide structure consisting of Al2O3 scale beneath a spinel (NiAl2O4) layer.