Long-term oxidation behaviour of Ni3Al alloys with and without chromium additions

The oxidation behaviour of NiAl alloys with and without chromium additions was studied after long-term exposure in an air furnace over a wide temperature range from 560–1300‡C. The chromium-containing alloy exhibited a better oxidation resistance below 1150‡C. Above this temperature the penetration depth of oxides into and along the grain boundaries in the chromium-containing alloy became larger than that in the alloy without chromium. Also the penetration depth increased drastically at 1150‡C for both alloys. Through energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy analyses, the compositions and structures of the oxide scales for both alloys were also identified.