A new Ni-based alumina-forming alloy, NiCoCrMoAl, has been invented with the high creep strength and excellent high temperature oxidation and corrosion resistance for high temperature applications. The static oxidation tests of the alloy, along with the other commonly used Ni-based high temperature alloys, such as UNS N07214, N06230, N06002, N06625 and N06617, were conducted at the temperatures of 871 °C (1600 °F), 982 °C (1800 °F), and 1149 °C (2100 °F). The oxidation kinetics and cross-sections of the alloys were analyzed to understand their oxidation mechanism and behaviors. At the test temperatures, the alumina-forming alloys, NiCoCrMoAl and N07214, showed excellent oxidation resistance as a result of the formation of a continuous and adherent alumina scale. In addition, the NiCoCrMoAl alloy exhibited similar or superior oxidation resistance when compared to the N07214 alloy, which was attributed to a consistent alumina scale formed on NiCoCrMoAl with less internal oxidation attack. The chromiaforming alloys showed good oxidation resistance, without observed spallation, due to the formation of a protective chromia scale at 871 and 982 °C. At 1149 °C, the chromiaforming alloys showed inferior oxidation resistance, in which N06625 experienced breakaway oxidation after two cycles (336h). Amongst the chromia forming alloys, the N06230 alloy showed the best oxidation resistant performance at the test temperatures.
Keywords: High temperature, Oxidation, Ni-Base alloy, Alumina-former, Chromia-former