Oxidation behaviour of NiAl intermetallics with embedded Cr and Mo

The isothermal oxidation of directionally solidified NiAl-34Cr and NiAl alloys with embedded Cr bar and Mo wire were studied in a thermobalance at 800 °C, 1200 °C and 1300 °C for 50 h (Ar/ 13 vol.% O${}_2$). NiAl-Cr showed formation of a continuous Al${}_2$O${}_3$-Cr${}_2$O${}_3$ solid solution in the vicinity of the interface of NiAl and Cr in which the composition changed from almost pure Al${}_2$O${}_3$ near the metal matrix to almost pure Cr${}_2$O${}_3$ near the gas surface. DS NiAl-34Cr showed more spallation compared to NiAl-Cr. In case of NiAl-Mo, a weight loss was observed due to formation of volatile oxides.