High temperature oxidation of intermetallic compounds of Mo(Si 1- xAl x) 2

Abstract

High temperature oxidation of Mo(Si 1- x Al x ) 2 and MoSi 2 was examined at 1823 and 2048 K in air. At 1823 K, Mo(Si 1- x Al x ) 2 gave a scale of alumina and the scale on MoSi 2 was composed of amorphous silica which partly crystallizes into crystobalite. At 2048 K, the scales on both MoSi 2 and Mo(Si 1- x Al x ) 2 were in a liquid state. On cooling, the scale on MoSi 2 completely crystallized into crystobalite, while that on Mo(Si 1- x Al x ) 2 remained in an amorphous state because the dissolution of alumina suppressed the crystallization. The oxidation rate was higher for Mo(Si 1- x Al x ) 2 than for MoSi 2. The scale adherence was excellent for Mo(Si 1- x Al x ) 2 although the scale easily spalled off in MoSi 2.