Abstract:Because of its superior high-temperature creep strength in combination with good workability and low cost compared to its Ni-Co-Cr based counterparts, GH 2984 alloy is evaluated to be a candidate material for applying as superheater/ reheater in 700℃ ultra-supercritical coal-fired power plants. At such high temperature (up to 700-760℃), the corrosion behavior of the alloy in steam is of great concern mainly due to the thickness of the oxide scales that are formed. In the present work, the oxidation behavior of GH 2984 alloy in pure steam at 750℃ has been investigated by using scanning electron microscope and X-ray diffractometer. The results show that a single Cr2O3 layer is formed with minor TiO2 solid soluted in it. Ti and Al are internally oxidized into TiO2 and Al2O3, respectively, preferentially along grain boundaries in the alloy underneath the Cr2O3 scale. The oxidation kinetic of the alloy observes a parabolic law. Investigation on the morphology evolution figures out that Cr2O3 blades formed initially which decreased in number and length and finally evolved into short rod-like ones with increasing oxidation time. The reason for the Cr2O3 nodules and blades formation and the oxidation mechanism of GH 2984 alloy in pure steam is discussed in detail.