Effects of Dy on cyclic oxidation resistance of NiAl alloy

The NiAl alloys modified by reactive element(RE), dysprosium(Dy), were produced by arc melting. The microstructures of the modified alloys were investigated by field emission-scanning electron microscope(FE-SEM) equipped with energy dispersive spectroscope(EDS) and back scatter detector. Cyclic oxidation tests at 1 200 °C were conducted to assess the cyclic oxidation performance of the alloys. The Dy dopant prevents the surface rumpling of the oxide scale and the formation of cavities beneath the oxide scale. The pegs consisting of Dy-rich oxide inclusion core and an outer alumina sheath develop deeply in the alloy and improve the oxide scale adhesion. 0.05%-0.1% (molar fraction) Dy dramatically improves the cyclic oxidation resistance of the NiAl alloy. Too high concentration of Dy is deleterious because of the fast oxidation rate caused by severe internal oxidation.