Oxidation behavior of αMo-Mo3Si-Mo5SiB2 (T2) three phase system

The cyclic oxidation kinetics and microstructures of the oxide scales have been investigated from 600 to 1400 degreesC on compositions within the three phase field alphaMo-Mo3Si-Mo5SiB2. From 600 to 750degreesC, the oxidation behavior is controlled by increasing volatilization Of MoO3 with increasing temperature and, consequently there is no oxidation protection. From 800 to 900 degreesC, the kinetics show a rapid transient weight loss due to MoO3 Volatilization and, a steady state weight loss associated with the formation of a porous outer borosilicate scale and continuous escape Of MoO3. At and above 1000 degreesC, the oxide scale consists of relatively solid and well adherent outer SiO2 scale and an inner reaction zone consisting of alphaMo and SiO2 phases. In the temperature regime 10001300 degreesC, there is a high degree of oxidation protection characterized by low transient- and steady-state weight losses. The overall oxidation behavior is governed by a competition between volatilization of Mo and the passivation provided by formation of borosilicate glass scale. (C) 2002 Elsevier Science Ltd. All rights reserved.