Improvement of the oxidation-proof property and the scale structure of Mo3Si intermetallic alloy through the addition of chromium and aluminum elements

The influences of chromium and aluminum additions to Mo3Si intermetallic alloy on the microstructure, mechanical and oxidation properties as well as the scale evolution were investigated for alloys with the composition of Mo75 − yCrySi25 − xAlx (y = 0, 15, 30, 45, 60, 75 mol%, x = 0, 5, 10 mol%). Cr and Al were added for the aim of not only improving the oxidation property but also changing the compound type from Daltonide to Berthollide ones. The alloys were prepared by arc-melt method and the button ingots were homogenized at 1873 K for 10 h. It was found that the homogenized (Mo,Cr)3Si alloy consists of continuous solid solution. During oxidation test at 1173 K, the mass of Mo3Si alloy decreased remarkably due to the evaporation of molybdenum oxides. However, the improvement of the oxidation resistance was confirmed when chromium was added up to at least 15 mol%. In particular, the (Mo,Cr)3Si alloys with above 30 mol%Cr showed excellent oxidation resistance through the formation of the passive oxide-scale layer. Although the effect is smaller, aluminum addition also contributed to the improvement of oxidation resistance.